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Publication numberUS3854447 A
Publication typeGrant
Publication dateDec 17, 1974
Filing dateOct 18, 1973
Priority dateOct 19, 1972
Also published asCA1012447A1, DE2352605A1, DE2352605B2
Publication numberUS 3854447 A, US 3854447A, US-A-3854447, US3854447 A, US3854447A
InventorsH Kobayashi
Original AssigneeMatsushita Electric Ind Co Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Apparatus for deposition of semiconductor thin layers
US 3854447 A
Abstract
An apparatus for crystal growth is originally provided with at least one cavity arranged axially thereof for storing a solution containing material to be epitaxially grown on a plurality of substrates. The apparatus comprises a plurality of plate members arranged on top of one another, each of the plurality of plate members having at least one recess for accommodating the substrates, the plurality of plate members being arranged to be movable alternately relative to the remaining plate members so that the substrates in the recesses of the movable plate members are caused to contact the solution and simultaneously the solution confined in a bore of the movable plate members is caused to contact the substrate in the recesses of the stationary plate members.
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Description  (OCR text may contain errors)

United States atent m1 [75] Inventor: Hiroyuki Kobayashi, Kawasaki,

Japan [73] Assignee: Matsushita Electric Industrial Company, Limited,'Kadoma City, Osaka, Japan [22] Filed: Oct. 18, 1973 [21] Appl. N0.: 407,605

[30] Foreign Application Priority Data 0m. 19. 1972 Japan 47405114 52 11.8. C1 118/421, 118/425, 148/171 [51] Int. Cl. B05c 3/00 [58] Field of Search 118/421, 400, 423, 425, 118/415, 500; 148/171, 172

[56] References Cited UNITED STATES PATENTS 3,665,888 5/1972 Bergh et'al. 113/415 X Kobayashi V Dec. 17, 1974 [54] APPARATUS FOR DEPOSITION OF 1 3,690,965 9/1972 Bergh et a1. 148/172 SEMICONDUCTOR THIN L E 3,759,759 9/1973 Solomon 148/171 3,765,959 10/1973 Unno et a1. 148/171 Primary ExaminerMorris Kaplan [5 7] ABSTRACT .An apparatus for crystal growth is originally provided with at least one cavity arranged axially thereof for storing a solution containing material to be epitaxially grown on a plurality of substrates. The apparatus comprises a plurality of plate members arranged on top of one another, each of the plurality of plate members having at least one recess for accommodating the substrates, the plurality of plate members being arranged to be movable alternately relative to the remaining plate members so that the substrates in the recesses of the movable plate members are caused to contact the solution and simultaneously the solution confined in a bore of the movable plate members is caused to contact the substrate in the recesses of the stationary plate members.

11 Claims, 38Drawing Figures PATENTEUUEBIYIQN 3854,44?

SHEET 10F 9 F/lg- (PRIOR ART) los Hoe Fig. /b (PRIOR. ART) Fig. lc (RR)0R RT) I24 I23 I2) I22 Fig. la (RR)0R ART) PAINTED-181N974 SHEET 2 OF 9 N QE HEAVY NMOHS :JO SSBNMOIHL PATENTEU and] 71974 SHEET 4 BF 9 APPARATUS FOR DEPOSITION OF SEMICONDUCTOR THIN LAYERS This invention relates to an apparatus for epitaxial growth from liquid phase and more particularly to an apparatus suitable for mass-production of epitaxially grown wafers from liquid phase.

The liquid-phase-epitaxial process has proven to be a very effective technique for formation of high quality semiconductor wafers. Heretofore, various apparatus for liquid-phase-epitaxial growth have been developed, and an apparatus equipped with a sliding substrate holder has found widespread use because in it reproducibly highly uniform wafers are being grown.

The prior art apparatus will be described with reference to FIGS. 1a -'ld of the accompanying drawing.

FIGS. 1a through 1d are cross-sectional views of four conventional apparatus each equipped with a sliding substrate holder. In FIG. 10, there is shown a most typical one provided with a solution holder 101 and a sliding substrate holder 102 arranged slidably in intimate contact with the bottom surface of the solution holder 101. The sliding substrate holder 102 is provided with a recess 105 for accommodating a substrate 106 therein. The solution holder includes a plurality of bores 103 each of which carries a solution 104 containing material to be epitaxially grown on the substrate 106. In this prior art arrangement, the temperature of the solution is elevated to a desired predetermined level, then the sliding substrate holder 102 is pushed as indicated by an arrow to bring the substrate into contact with the solution, and the solution is allowed to cool to grow an epitaxial layer on the substrate. After the completion of the first epitaxial growth, the sliding substrate holder is further pushed for succeeding solution-substrate contacts, thus resulting in growth of successive epitaxial layers from the liquid phase on the substrate. This apparatus is disclosed in US. PAT. NO. 3,565,702 issued Feb. 23, I971 to Nelson, and also on page 109 of the Applied Physics Letters, vol. 17, No. 3, 1970.

Recently an improvement of the aforementioned method, i.e., so called sliding method had been made by Miller et al. As described in detail in J. Appl. Phys", vol. 43, No. 6, P. 2,817, June 1972.

In spite of the excellent crystalline characteristics of wafers grown by these apparatus, they suffer some drawbacks, one of which is non-suitability for massproduction of wafers. Therefore, efforts have been made to develop apparatus suitable for mass production. In FIGS. lb through hi, there are shown conventional apparatus directed to this end. Referring now to FIG. 1b, there is shown an apparatus, which is similar to the apparatus of FIG. la except that a sliding substrate holder 112 is provided with a plurality of recesses 115 each accommodating a substrate 116. In operation, the sliding substrate holder 112 is pushed as indicated by an arrow, resulting in a plurality of simultaneous substrate-solution contacts. FIG. shows an apparatus much more suitable for mass-production by stacking on top of each other two apparatus of FIG. 1b. However, disadvantages are encountered in each of these apparatus of FIGS. lb and 1c in that each requires a bulky furnace and a large volume of solutions. Another disadvantage is that each of the wafers grown is liable to have heterogeneous crystalline characteristics because it is commonly very difficult to maintain a homogeneous temperature area within a bulky furnace. In FIG. 1d another conventional apparatus for a massproduction of wafers is shown. The difference between 1 the apparatus illustrated in FIGS. 1b and 1d is that a solution holder 131 is provided with only one cavity. The disadvantages inherent to the apparatus are the required very long operating time and lengthy furnace, so that a variation in proportions of constituents of of the solution and horizontal temperature gradient are liable to occur.

The present invention is, therefore, intended to improve liquid-phase-epitaxial growth apparatus and contemplates to obviate the above-mentioned disadvantages. An apparatus according to the present invention is originally provided with at least one cavity arranged axially thereof for storing a solution containing material to be epitaxially grown on a plurality of substrates. The apparatus comprises a plurality of plate members arranged on top of one another, each of the plurality of plate members having at least one recess for accommodating the substrates, the plurality of plate members being arranged to be slidable alternately relative to the remaining plate members so that the substrates in the recesses of the slidable plate members are caused to contact the solution and simultaneously the solution confined in a bore of the slidable plate members is caused to contact the substrate in the recesses of the stationary plate members. Because of the compactness of the apparatus epitaxial growths on a plurality of separate substrates are readily obtained. In practice, the thickness of the plate member is within a range of 0.8 to 1.5 millimeters, for example, and the size of each recess for accommodating the substrates is determined in accordance with that of each of the substrates. From the above description, it is understood that various advantages can be derived by use of the present apparatus. Because of the very small temperature gradient due to the very small size and the confinement of the solution to a thin liquid layer above the substrate, the epitaxial layer grown has a very uniform thickness throughout the whole wafer and only a small amount of solution is required. Furthermore, epitaxial growths can be readily attained on a mass production scale in a short operating time. The short operating time in turn makes it possible to reduce contamination of the solution and uniform growth is obtained since there are no fluctrations of constituent proportions in the solution. Also, assuming that the surface of the solution is contaminated, this does not adversely affect the resultant wafer because the polluted solution is not used. From the foregoing description of the present invention, it is understood that the solution layer covering each of the substrates is very thin, for example, about 1 millimeter.

According to our experiment, the thickness of Ga? epitaxial-grown-layer from a saturated solution of Ga GaP increases with increasing depth of the solution layer covering the substrate. In FIG. 2, there is shown the relationship between them. In this case, variations of the solutions thickness have not adversely affected the characteristics of the resultant layers. Recently, in J. Appl. Phys, vol. 43 April 1972, P. 1394, Blum et al., have disclosed a liquid-epitaxial growth apparatus which make possible growth of reproducibly uniform and smooth layers by using a thin covering solution layer. In the above publication, it is described that an AI Ga As grown-diffused diode having superior luminant characteristics is fabricated with a solution layer as thin as about 0.8 millimeters.

It is accordingly an object of the present invention to provide an improved apparatus which is suitable for mass-production of epitaxially grown wafers during a short operating time.

Another object of the present invention is to provide an improved apparatus with a small homogeneous temperature area at which the operation is completed in a short time.

Still another object of the present invention is to provide an improved apparatus of small size.

A further object of the present invention is to provide an improved apparatus which requires a small volume of solution of the material to be epitaxially grown on substrates.

A still further object of the present invention is to provide an improved apparatus capable of reproducibly grow highly uniform wafers.

These and other objects, advantages and features of the present invention will be better understood from the following description when taken in conjunction with the accompanying drawings, in which:

FIGS. la through 1d are cross-sectional views of a prior art apparatus for Iiquid-phase-epitaxial growth.

FIG. 2 is a graph illustrating the relationship between the thickness of an epitaxially grown layer on a substrate and depth of solution covering the substrate.

FIG. 3a is a longitudinal sectional view of a first preferred embodiment for liquid-phase-epitaxially growth apparatus prior to substrate-solution contact in accordance with the present invention.

FIG. 3b is a longitudinal sectional view of the first preferred embodiment, which shows the substrate in contact with the solution after rotation of alternate plates a half cycle about the longitudinal axis thereof.

FIGS. 4a and 4b are perspective top and bottom views of a member of the first preferred embodiment illustrated in FIG. 3a, respectively.

FIGS. 40 and 4d are perspective and top views of another member of the first preferred embodiment illus trated in FIG. 3a, respectively.

FIGS. 4e and 4f are perspective top and bottom views from upper and lower sides of another member of the first preferred embodiment illustrated in FIG. 3a, respectively.

FIGS. 4g and 411 are perspective and top plan views of another member of the first preferred embodiment illustrated in FIG. 3a, respectively.

FIGS. 5a and 5b are perspective and top plan views of a variation of the FIG. 40 member, respectively.

FIGSfSc and 5e are perspective and top plan views of a variation of the FIG. 4g member, respectively.

FIGS. 6a and 6b are perspective and top plan views of another variation of the FIG. 4c member, respectively.

FIGS. 60 and 6d are perspective and top plan views of another variation of the FIG. 4g member, respectively.

FIGS. 7a, 7b, 7c and 7d are a perspective top view, top plan view, perspective bottom view. and bottom plan view of a variation of the FIG. 60 member, respectively.

FIGS. 7e, 7f, 7g and 7h are a perspective top view,

- top plan view, perspective bottom view, and bottom plan view of a variation of FIG. 60 member, respectively.

FIG. 8a is a perspective view of a second preferred embodiment of an apparatus in accordance with the present invention.

FIGS. 8b to 8e are perspective views of members of the embodiment of FIG. 8a.

FIG. 8fis a longitudinal sectional view of the embodiment of FIG. 80 prior to substratesolution contact.

FIG. 8g is a longitudinal sectional view of the em bodiment of FIG. 8a, which shows the substrate in contact with the solution after a sliding movement.

For detailed description of the present invention, reference is now made to FIGS. 3a through 4h. In FIG. 3a there is shown a longitudinal sectional view of a first preferred embodiment of an apparatus according to the present invention, wherein a refractory tube 11 is provided for disposing an epitaxial growth boat assembly therein. The tube 11 and assembly members of the boat assembly 30 are made of refractory material such as quartz, boron nitride, high purity graphite and the like. The refractory tube 11 is positioned a suitable refractory furnace (not shown) to be heated up to a desired predetermined temperature. The bottom wall 12 of the refractory tube 11 is partly concaved inwardly to form a small wall hole 15a for receiving a thermocouple 17. In the present embodiment, the wall hole 15 I is arranged in the bottom center portion of the tube 11 so that the thermocouple 17 might be positioned as close to a solution 31 and substrates 33 as practically possible. The thermocouple 17 indicates only an approximate temperature of them, which, however, is adequate. The tube 11 is provided with an elongate projection 13 on its inner bottom surface for supporting circumferentially a base member 60, which corresponds to a lowermost member of the growth boat 30.

In FIGS. 4e and 4f, there is shown the base member 60 wherein two recesses 63 and 65 are formed in the upper surface of a base plate member 69 in addition to the portion supporting a center rod 61, the recess 65 being provided for accommodating the substrate 33 therein, and the recess 63 for forming a bottom of a cavity 35. The two recesses each located equidistantly from the center point of the base plate member 69 and in the present embodiment the two recesses are arranged symmetrically with respect to the center point of the base plate member 69. The center rod 61 is attached to the center portion of the upper surface of the base plate member 69, extending axially, and being provided for carrying at the center portions pluralities of rotatable and stationary members, 50 and 70, respectively. A support shaft 62 is provided for supporting circumferentially .the plurality of stationary members 70 relative to the base member 60, and is L-shaped with the shorter arm attached to a portion of the circumference of the base plate member 69 and with the longer armextending into the same direction as the center rod 61. The longer arm carries the plurality of stationary members 70 at the bores 72 so that members 70 are fixed circumferentially relative to the base member 60 because the center rod 61 carries the members 70 at the center bores 7I. The base plate member 69 has formed in the lower surface an elongate recess 67 for receiving snugly the elongate projection 13 of the tube 11, so that the base member 60 is forced to stay circumferentially stationary relative to the tube 11. The

lower surface of the base plate member 69 forms a concave recess 68 in the elongate recess 67 for receiving theupper wall portion of the well hole 15, and in the present embodiment the concave recess 68 is arranged in the central portion of the lower surface.

In FIGS. 4a and 4b, there s shown a cap member 40. The center portion of a cap plate member 49 forms a circular center bore 41 for rotatably accommodating the center rod 61 of the base member 60. The cap plate member 49 forms a cap bore 43 in addition to the center bore 41 for forming the cavity 35, and also forms a cap recess 47 in the upper surface in addition to the center bore 41 and a cap bore 43'for receiving a drive shaft 15, which rotated the cap member 40 about the center rod of the base member 60. The drive shaft is rotated by suitable means (not shown) positioned outside the tube 11. A rotating shaft 42 is provided for rotating the plurality of rotatable members 50 about the center rod-61, and is L-shaped with the shorter arm attached to a portion of the circumference of the cap plate member 49 and with the longer arm extending axially downward to'the opening direction of the cap re-- cess 47. The longer arm of the rotating shaft 42 carries the plurality of rotatable members 50 at the bores 52 thereof, so that the drive shaft could rotate the rotatable members 50 about the center rod 61 by way of the cap member 40.

In FIGS. 4c .and 4d, there is shown one rotatable member 50, which has a recess 55 in the upper surface thereof for accommodating the substrate 33 and a bore 53 for forming the bore 35. Each of the recesses 55 and the bores 53 are located equidistantly from the center point of the member 50, and in the present embodiment they are arranged symmetrically with respect to the center point of the member 50. The central portion of the member 50 forms a center bore 51 for carrying snugly and rotatably the center rod 61 of the base member. A projection 54 radially protrudes from the circumference of the member 50, having a circular bore 52 therein through which the rotating shaft 42 of the cap member 40 carries snugly and rotatably the plurality of rotatable members 50.

FIGS. 4g and 4h illustrate one stationary member 70, which is similar to the rotatable member 50 except that a projection 74 protrudes from a different circumferential portion from which the projection 54 protrudes relative to substrate recesses 55 and 75.

It is to be noted that in the first preferred embodiment the projections 54 and 74 should be arranged in such a manner that they do not prevent a plurality of rotatable members from rotating through a half circle about the center rod 61 of the base member 60 for the purpose of complete substrate-solution contacts. In the first preferred embodiment, an assembly (FIG. 3a) is further provided for stirring-the solution to make it uniform and for doping an impurity into the solution 31 from the vapor sate; The stirring assembly 20 is rotated by suitable means (not shown) positioned outside the tube 11. The upper portion of a hollow tube 24 carries a chamber 23 in which a suitable impurity having a relatively high vapor pressure is contained, and the chamber 23 and the solution 31 communicate through openings 26 and 27 of the hollow tube 24. Blades 28 are attached to a lower portion of the hollow tube 24 for the purpose of stirring the solution.

The operation of the first preferred embodiment of the apparatus (illustrated in FIGS. 3a through 4h) is generally as follows. The suitable substrates 33 are placed in the recesses 65, 55 and 75 of the base member 60, the rotatable members 50 and the stationary members 70, respectively, and then the rotatable and stationary members 50 and 70 are alternately superimposed upon the base member 60, and thereafter the cap member 40 is put on the above assembly, thus forming the growth boat 30. In this case it is to be noted that the growth boat is originally arranged to form the cavity and this results in causing the axial alignment of the recesses (65, 55 and 75). A suitable charge of the materials to be epitaxially grown then placed in the cavity 35, and the growth boat 30 is disposed in the refractory tube 11 such that the elongate projection 13 is snugly engaged with the recess 67, fixing the boat 30 circumferentially. The drive shaft 15 is set as shown in FIG. 3a, and the refractory tube I] placed in a suitable furnace (not shown). Next, the temperature of the growth boat 30 is elevated to a desired predetermined degree through the tube 11. At the temperature thus attained the source material dissolves, and thereafter the solution 31 is stirred by the assembly 20 to become uniform and at the same time a suitable impurity is doped into it and the assembly 20 is pulled out of the tube 11. The drive shaft 15 is rotated by suitable means (not shown) to rotate counterclockwise both the cap member 40 and the plurality of the rotatable members 50 through a half circle about the center rod 61 of the base member 60, so that each of the substrates 33 carried in the recesses 55 is brought into contact with the solution confined in the each of the bores 73, while the solution confined in the each of the bores 53 is brought into contact with each of the substrates carried in the recesses 75. In FIG. 3b, there is shown in longitudinal sectional view the substrates contacting the solution. Then, the temperature is lowered slowly at a predetermined rate, so that a plurality of epitaxial growths take place at the same time, and after the completion of the epitaxial growths, the rotatable members are rotated clockwise for separating the solutions from the substrates. After the temperature of the apparatus is sufficiently low, for example, room temperature, wafers having epitaxially grown layers are taken out of the apparatus.

It is to be noted that in the present embodiment, for example, the recess 75 and the bore 73 of the stationary member are arranged symmetrically to each other with respect to the center point, however, it is not essential but solely for illustration. The arrangement is discretional on the condition that each of them be equidistant from the center point. The same statements are true for the other assembly members; In the present first embodiment, by providing suitable means therewith, multi-layer epitaxial growths on each of the substrates 33 can be accomplished. The means is provided in the bottom of cavity 35 for draining the solution after the completion of a first epitaxial growth, so that successive epitaxial growths on each of the substrates can be made by pouring new solution into the drained cavity 35. The new solution is stored in a suitable means which is provided over the cavity 35.

Reference is now made to FIGS. 5a and 5d, wherein there are shown a variation (FIGS. 5a and 5b) of the FIG. 4c member and a variation (FIGS. 5c and 5d) of the FIG. 4g member. In this case, variations of FIGS. 4a and 4e are not illustrated, however, they could be readily perceived from FIGS. 5a and 5c in view of FIGS. 4a and 4c, respectively. In FIG. 5a, the modified member 250 is provided with two recesses (255, 256), each of which accommodates a substrate therein, and two bores (253, 254) each forming a portion of a cavity for storing a solution. Similarly, in FIG. 50, the modified member 270 is provided with two recesses (275, 276), each of which accommodates a substrate therein, and two bores (273, 274) each forming a portion of a cavity for storing a solution. It is understood that, in accordance with the present apparatus embodiment, the number of produced grown wafers are twice that of the first preferred embodiment. Moreover, addition of an other bores and recesses to each of the members of FIGS. 5a and 5c make it possible to increase the number of epitaxially grown wafers tobe more than thrice that of the first embodiment. It is to be noted that in the above mentioned modified embodiments of the first preferred one a suitable means for draining a solution can be provided in each of the bottom portions of the cavities and a suitable means for storing solutions poured into the drained cavity also can be provided over the each of the cavities.

Referring to FIGS. 6a through FIG. 6d, there are shown two kinds of members which are incorporated in a still different form of the first preferred embodiment. In FIGS. 6a and 60 there are shown different variations of FIGS. 40 and 4g, respectively. FIGS. 6b and 6d are top plan views of FIGS. 6a and 6c, respectively. Itis understood that each of the variations illustrated in FIGS.

60 and 6c is provided with one more bore as compared I the base member 60 of FIG. 4e which are also equipped with this preferred embodiment, however, they are readily perceived from FIGS. 6a and 6c in view of FIG. 4a and 4e, respectively. In operation, substrates are placed within each of a plurality of recesses 355 and 375, and a first change is positioned within a first cavity formed by pluralities of bores 354 and 374, and a second charge within a second cavity formed by pluralities of bores 353 and 373. Then, the temperature of the growth boat is elevatedto a desired predetermined degree, so that the first and second charges dissolve forming first and second solutions, respectively. A modified cap member is rotated by a suitable means similar to the drive shaft of FIG. 3a, and the rotation in turn causes a plurality of members 350 to rotate about the longitudinal axis of the boat assembly. In the present case, the members 350 are rotated, for example, clockwise 90 degrees so that each of the substrates accommodated in the recesses 355 of the members 350 is brought into contact with the first solution confined in bores 374 of the members 370. The first solution confined in each of the bores 354 is brought into contact with each of the substrates in recesses 375, thus a first substrate-solution contact is accomplished.

After the completion of the first epitaxial growths, the members 350 are rotated counterclockwise through a half circle, resulting in an occurence of a second substrate-solution contact in the same manner as above described.

Reference is made to FIGS. 7a through 7h, wherein there is shown a variation (FIGS. 7a 7d) of the FIG. 60 member and a variation (FIGS. 7e 7/1) of the FIG. 61 member. A member 450 (FIGS. 70 7d) is similar to the member 350 (FIGS. 60 and 6b) except that the former is provided with a recess 454 (FIGS. 70 and 7d) in the lower surface corresponding with the bore 354 of the member 350. The member 470 (FIGS. 7e 7h) is similar to the member 370 (FIGS. 6:: and 6d) except that the former is provided with a recess 474 (FIGS. 73 and 7h) in the lower surface corresponding with the bore 374 (FIGS. 6c and 6d) of the latter. In the present embodiment, esch of the recesses 454 and 474 is used for accommodating an impurity. In operation, each of a plurality of substrates is placed within each of a plurality of recesses 455 (FIGS. 7a and 7b) and 475 (FIGS. 7c and 7]), and then a charge is positioned within a cavity formed by pluralities of bores 453 (FIGS; 7a 7d) and 473 (FIGS. 7e 7h). The growth boat is disposed within a suitable furnace (not shown). Then, the temperature of the growth boat assembly is elevated to a desired predetermined degree, so that the source materials dissolve forming a solution. Following, the members 450 are rotated counterclockwise through about the center axis so that a first substrate-solution contact is accomplished in the same manner as described in connection with one form of the first preferred embodiment (FIGS. 6a 6d). After completion of the first epitaxial growth, the members 450 are rotated counterclockwise 909 in order to dope the solution with the impurity. Then the members 450 are rotated clockwise 90 for a second substratesolution contact. The resultant second epitaxial layers are characteristically different from the first ones.

Reference is now made to FIGS. 8a through 8f, wherein ther are shown a second preferred embodiment of the apparatus in accordance with the present invention. An epitaxial growth boat 800 forms a cavity 895 which is arranged axially thereof for storing a solu tion 870. The growth boat 800 comprises a base member 841', pluralities of transverse stationary 831 and slidable 821 members which are arranged alternately on top of one another upon the base member 841, and a cap member 811 is put on the above assembly. The epitaxial boat assembly 800 is equipped with a suitable casing or housing (not shown) which has a bore in the upper surface forming a portion of the cavity 895 and has stoppers for stopping horizontal movement of the stationary members 831, the base 841 and cap 811 members. The upper surface of the base member 841 forms a recess 845 for forming a portion of the cavity 895 and a recess 847 for accommodating one of the substrates 860 therein. Each of the plurality of transverse stationary members 831 is provided with a recess 837 in the upper surface for accommodating one of the substrates 860 and is provided with a bore 835 forming a portion of the cavity 895. Each of the plurality of transverse slidable members 821 is provided with a recess 823 in the upper surface for accommodating one of the substrates 860 and provided with a bore 825 for forming a portion of the cavity 895. It is to be noted that the bores 825 and 835 are provided in the opposite sides with respect to the cavity 895. The cap member 811 is provided with a bore 815 forming a portion of the cavity 895. Preferably, each of the transverse stationary and slidable members is rectangular, each of the bores and recesses having a circular cross section, each of the bores and each of the recesses being equidistantly spaced not more than, for example, I centimeter apart, and the thickness of each of the stationary and slidable members being, for example. about 0.8 1.5 mm.

In operation, each of the substrates 860 is placed within each of the recesses, the boat 800 assembled as mentioned above, and then source materials placed within the cavity 895. The boat assembly is then equipped with the suitable casing and disposed in a suitable furnace (not shown) and its temperature is elevated to a desired predetermined degree. At the temperature thus attained, the source materials dissolve forming a solution. Next, the plurality of slidable memhers is slid to the direction as indicated by arrows (FIG. 8}) by suitable means (not shown) at the same time, so that each of the substrates accommodated in the recesses 823 is brought into contact with the solution, while the solution confined in each of the bores 825 is brought into contact with each of the substrates accommodated in the recesses 837 and 847. Then the temper- EXAMPLE I This example describes the fabrication of an electroluminescent p-n junction diode and more particularly growth of an epitaxial p-type-GaP layer on n-type-GaP layers in accordance with the first preferred embodiment of the apparatus of the present invention. Prior to the above-mentioned epitaxial growth, the following preparations are made. An n-type-GaP single crystal is fabricated by a crystal pulling method under high pressure, next, on a sliced wafer from the single crystal an n-type-GaP epitaxial layer is deposited by the use of the apparatus in accordance with the first preferred embodiment of the apparatus, wherein there is utilized a solution including 20 grams of Ga, 2 grams of polycrystal Ga? and 2 milligrams of tellurium. After'preparing the wafers each having an n-type-GaP layer on the GaP substrate, an epitaxial p-type-GaP layer is further deposited on each of the n-type-GaP layers as described below. A plurality of the wafers is placed in the recesses 65 (H6. 4e), 75 (H6. 4g) and 55 (FIG. 4c). The epitaxial boat 30 is formed according to the description of the first'preferred embodiment. Disposed is within the cavity 35 source materials which include 20 grams of Ga, 2 grams of polycrystal GaP and 30 milligrams of 641 Thereafter the epitaxial growth boat 30 is placed within the tube 11 such that the elongate recess 67 of the base member 60 is engaged with the projection 13 of the tube 11. An impurity material having a high vapor pressure, in this example, zinc is provided in the chamber 23 and the stirring means 20 is arranged as shown in FIG. 30. Finally, the cavity 35 is covered by the cover 19. The air in the tube 11 is completely substituted by high purity hydrogen gas and the tube 11 is placed in a suitable furnace. The temperature of the apparatus is elevated to approximately 1,020C. and then the formed solution 31 is stirred by the stirring means 20 to make the solution uniform. At this temperature, zinc accommodated in the chamber 23 is added to the solution from vapor state so that the solution is doped with a predetermined concentration of zinc. After stirring the solution sufficiently, the stirring means 20 is pulled out of the tube 11. Thereafter, the drive shaft is rotated counterclockwise by suitable means, resulting in the simultaneous rotation of a plurality of the rotatable members 50 by way of the cap member 40, so that a substrate-solution contact is achieved in the same manner as described in detail in connection with the first preferred embodiment. In this example, the rotatable and stationary members each has a thickness of l millimeter, so that the solution covering the substrate is naturally I millimeter deep.

Thereafter, the temperature is lowered at the rate of 2.5C/min so that epitaxial layers are grown on the substrates. When the temperature is lowered to approximately 800C, the rotatable members are rotated clockwise for the purpose of separation of the sub strates from the solution. The epitaxial layers so obtained ar p-type and have free carrier concentratio of 5 X 10 electrons per cubic centimeter. After the temperature is lowered to room temperature, the formed wafers are taken out of the apparatus and then subjected to a mesa-etching process, and after attaching ohmically electrodes thereto, being scribed and cut in the usual manner into pellets of semiconductor devices. Thus, we have obtained electroluminescent diodes, which emit red light by a forward flowing current of 3 milliamperes.

EXAMPLE ll This example describes the fabrication of another electroluminescent diode having high luminance according to a varied form of the first preferred embodiment of the apparatus of the present invention. In this example, mirror-etched n-type GaAs wafers doped with tellurium at 10 electrons per cubic centimeter are used as substrates. The substrates are placed in the recesses 355 (FIG. 6a), 375 (FIG. 60) and the recess of the modified base member of FIG. 4e. The epitaxial boat is formed according to the description of the first preferred embodiment. It is understood that the varied form of the first preferred embodiment provides two solution-containing cavities.

in the first cavity, the solution includes 20 grams of Ga, 2 grams of GaAs, 9 milligrams of Al, and a small amount of Si for impurity, and the solution in the sec ond cavity includes 20 grams of Ga, 2 grams of GaAs, 180 milligrams of Al and a small amount of Si for impurity. Thereafter, the epitaxial growth boat is placed within the tube 11 such that the elongate recess 67 of the modified base member is engaged with the projection 13 of the tube 11. The air in the tube 11 is completely substituted by high purity hydrogen gas and the tube 11 is placed in a suitable furnace. The temperature of the apparatus is elevated to 860C, resulting in melting the source materials in two cavities. After heating the apparatus sufficiently, that is, minimizing temperature gradients thereof, the drive shaft 15 is, for example, clockwise rotated through by suitable means, resulting in the simultaneous 90 rotation of a plurality of rotating members 350 by way of the modified cap member vso that a first substrate-solution contact is achieved as described in detail in connection with the third preferred embodiment. In this example, the rotatable and stationary members (350, 370) each has a thickness of about 1 millimeter, so that the solution covering the substrates is naturally about 1 millimeter deep. Thereafter, the temperature is firstly lowered at the rate of 15C per minute, secondly per minute so that silicon contained in the solution is firstly added as a donor and secondly as an acceptor into two layers, respectively, thus resulting in successively depositing n-type and p-type layers of GaAlAs on the ntype-GaAs substrate. Next, the rotatable members 350 are rotated counterclockwise through a half circle about the longitudinal axis of the boat assembly for a second solution-substrate contact, and after the temperature of the solution is reached at 840C, the temperature is reduced at the rate of 2C per minute, resulting in a successive epitaxial growth on the p-type layer of GaAlAs. The epitaxial layer grown by the first substrate-solution contact has a p-n junction therein and a molar ratio of (AlAs) containing in the layer to (GaAsAl) is about 1:5. The epitaxial layer grown by the second substrate-solution contact has a 1:2 molar ratio of (AlAs) to (GaAsAl) and also a larger energy gap. Consequently, since the inner absorption of light emitted in the p-n junction is reduced due to the larger energy gap, the resultant electroluminescent diode has a high degree of luminance.

What is claimed is:

1. Apparatus for depositing epitaxial layers on a plurality of substrates from a liquid phase, which comprises:

a refractory furnace;

a refractory tube disposable internally of said furnace;

an epitaxial growth boat disposable within said refractory tube, and provided with at least one cavity arranged axially thereof, a solution of material to be epitaxially grown on a plurality of substrates andstored in said at least one cavity, said boat comprising a plurality of flat members arranged on top of one another, each of said plurality of flat members having at least one recess for accommodating said substrate, alternate members of said plurality of flat members being arranged to be movable relative to the remaining fiat members so that a plurality of substrate-solution contacts are accomplished.

2. Apparatus for depositing epitaxial layers on a plurality of substrates from a liquid phase, which comprises:

a refractory furnace;

a refractory tube disposable internally of said furnace;

an epitaxial growth boat disposable within said re fractory tube, and having a longitudinal axis, said boat being provided with at least one cavity arranged axially with said axis, a solution of material to be epitaxially grown on a plurality of substrates and stored in said at least one cavity, said boat comprising plurality of transverse movable members, each of said members having at least one first recess accommodating said substrate therein, and at least one first bore for forming a portion of said at least one cavity, said transverse movable members being movable about said longitudinal axis, each of said at least one first recess and bore located equidistantly from the center point thereof, and plurality of transverse stationary members, each having at least one second recess accommodating at least one second substrate therein, and at least one second bore for forming a portion of said at least one cavity, each of said at least one second recess and bore being located equidistantly from the center point thereof, said plurality of movable and plurality of stationary members being alternately arranged coaxially on top of one another such that said at least one first and at least one second bores form said at least one cavity and such that said at least one first and at least one second recesses are axially arranged in at least one straight line, whereby a movement of each of said plurality of transverse movable members causes said substrate in said at least one first recess to contact said solution confined in said at least one second bore and causes simultaneously said solution confined in said at least one first bore to contact said substrate in said at least one second recess, and further movements of each of said plurality of transverse movable members cause a plurality of substratesolution contacts.

3. Apparatus as claimed in claim 2, in which said epitaxial growth boat further comprises:

a flat base member, arranged coaxially in intimate contact with a first end of the set of said pluralities of movable andstationary members,

at least two recesses formed in a first surface of said flat base member in addition to the portion supporting a center rod, at least one of which accommodates one of said substrates therein, the remaining recess being provided for forming a bottom of said at least one cavity, said recesses being each located equidistantly from the center point of said flat base member,

said center rod attached to the central portion of said first surface of said flat base member, and extending axially to the opening directions of said recesses formed in said first surface, being provided for carrying at their central portions said pluralities of movable and stationary members,

a shaft attached to said base plate member for fixing said plurality of stationary members relative to said base member, and

a first base fixing means formed in a second surface of said base plate member, engageable snugly with a second base fixing means formed in the inner bottom surface of said refractory tube.

4. Apparatus as claimed in claim 3, in which said flat base member is circular,

said shaft being L-shaped with the shorter arm attached to a portion of the circumference of said base member and with the longer arm extending to the same direction as said center rod,

each of said recesses having a circular cross section,

said first base fixing means being a groove. 5. Apparatus as claimed in claim 2, in which said epitaxial growth boat further comprises: i

a flat cap member arranged coaxially in intimate contact with the second end of the set of said pluralities of rotatable and stationary members, the center portion of said flat cap member forming a circular cap center bore for rotatably accommodating said center rod of said base member,

said fiat cap member forming at least one cap bore therethrough in addition to said cap center bore for forming said at least one cavity,

said cap plate member forming a cap recess in a first surface in addition to said center bore for receiving a drive shaft provided for moving said cap member about said center rod of said base member, and

a moving shaft attached to said cap member for moving said plurality of transverse movable members about said center rod of said base member.

6. Apparatus as claimed in claim 5, in which said flat cap member is circular,

said moving shaft being L-shaped with the shorter arm attached to a portion of the circumference of said cap member and with the longer arm extending axially in the opening direction of said cap recess, and in which each of said cap bore and said cap recess have a circular cross section.

7. Apparatus as claimed in claim 2, in which said at least one first recess of each of said plurality of transverse movable members is formed in a first surface thereof in addition to a first center bore,

the central portion of each of said plurality of transverse movable members forming said first center bore for carrying snugly and movably said center rod of said base member,

said first bore of each of said plurality of transverse movable members being formed therethrough in addition to the portion of said first center bore,

a projection radially protruding from a side edge of said movable member, and having a circular bore therein through which a moving shaft of a cap member carries snugly and rotatably said plurality of said movable members about a center rod of said base member.

8. Apparatus as claimed in claim 7, in which each of said plurality of movable members is a circular plate, and each of said first bore and first recess have a circular cross section.

9. Apparatus as claimed in claim 2, in which said at least one second recess of each of said plurality of transverse stationary members is formed in a first surface thereof in addition to a second center bore,

the central portion of each of said plurality of transverse stationary members forming said second center bore to be snugly carried by a center rod of a base member,

said second bore of each of said plurality of transversal stationary members being formed therethrough in addition to said second center bore, and in which a projection radially protruding from a side edge of said stationary member, having a bore therein through which said fixing shaft means of said base member carries snugly said stationary member for fixing relative to said base member circumferentially.

10. Apparatus as claimed in claim 9, in which each of said plurality of stationary members is a circular plate, and each of said second bore and second recess having a circular cross section.

11. Apparatus as claimed in claim 2, wherein each of said plurality of transverse movable members further comprises at least one third recess formed in the second surface thereof, each of said first and third recesses being located equidistant from the center point thereof,

each of said plurality of transverse stationary members further comprising at least one fourth recess formed in the second surface thereof, each of said second and fourth recesses of said transverse stationary members being located equidistant from the center point thereof, said rotatable and stationary members being alternately arranged on one another such that said third and fourth recesses are axially arranged in at least one straight line.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO. 5,85Z+,/+L+7 Dated December 17, 197

Inventor(s) Hirovuki Kobavasi It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the first page under item [19] "Kobayashi" should be --Kobayasi-- Item [75] "Kobayashi" should be --Kobayasi- Signed and sealed this 1st day of July 1975.

(SEAL) Attest:

C. I'ZARSHT-TLL HAHN RUTIF C. MASON Cormissioner of Patents Attesting Officer and Trademarks

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3951700 *Aug 16, 1974Apr 20, 1976Tokyo Shibaura Electric Co., Ltd.Epitaxial
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Classifications
U.S. Classification118/421, 118/425, 117/61
International ClassificationC30B19/00, H01L21/208, C30B19/06, H01L21/02, H01L33/30
Cooperative ClassificationC30B19/065, C30B19/064
European ClassificationC30B19/06J, C30B19/06I