US 3918396 A
Semiconductor material, in particular silicon, is deposited onto heated carrier members from gaseous semiconductor compounds within a chamber formed by a glass or quartz dome and a base member. Breakage of the dome is avoided by a pressure chamber surrounding the glass dome.
Description (OCR text may contain errors)
[ Nov. 11, 1975 United States Patent n91 Dietze et al.
[ CONTAINER FOR THE PRODUCTION OF 3.293.074
SEMICONDUCTOR BODIES 112  Inventors: Wolfgang Dietze, Munich; Herbert 3:492:96) Sandmann, Vaterstetten. both of 3.690.290
Germany 1 ms S67 Siemens Aktiengesellschaft, Berlin & Munich, Germany Mar. 4, 1974  Assignee:
Primary Examiner-Mo rris Kaplan . Filed:
Attorney. Agent. or FirmHill. Gross. Simpson. Van Santen. Steadman, Chiara & Simpson Appl. No.: 447,721'
Foreign Application Priority Data May l4v i973 ABSTRACT Germany...................;........
Semiconductor material. in particular silicon. is depos- I ited onto heated carrier members from gaseous semiconductor compounds within a chamber formed by a glass or quartz dome and a base member. Breakage of the dome is avoided by a pressure chamber surrounding the glass dome.
oonhz Q N L 43. 0 W 1 lc m am W H Wmh c r U "e HUS L .f C...0 .M Uhh H M UUU References Cited UNITED STATES PATENTS 6 Claims, 1 Drawing Figure U.S. Patent Nov. 11,1975
CONTAINER FORTTHE PRODUCTION OF SEMICONDUCTOR BODIES BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to the production of semiconductor bodies by the thermal decomposition of gaseous semiconductor compounds on heated surfaces of carri'er members. I
2. Prior Art" Reaction containers used for the deposition of semiconductor materials such as silicon from gaseous compounds onto heated carrier members are known in particular fromthe German Letters Patent 1' I98 787. They comprise a quartz or glass dome, nozzles for the supply and discharge of reaction gases as well as a plate-or disc-schap ed base member whereby the dome must be held air-tightly on the base member.
In the German Letters Patent 1 I98 787, the carrier members are two parallel silicon rods which are arranged perpendicular to the base plate and which are mounted on the electrodes extending from the base plate. Their upper ends are conductively connected by a bridge made of silicon or graphite. An electric current is supplied through the electrodes, and it flows through both silicon rods or tubes and heats them to the requiredtemperature. The base member consists of a temperature-resistant metal such as silver, whereby the surface which forms part of the reaction chamber is covered by quartz plates. It is also possible to replace the carrier rods by tubes or discs, exchange their material for graphite, and/or use a different manner of heating them. 7
Usually the quartz dome is placed on a sealing ring made of air-tight, elastic material, and -a flange at its margin serves for clamping the dome onto the base member. Clamping members or similar mounting members are usedfor this purpose, whereby a bettersealing effect is obtained by the use of a grease which is resistant to'high temperatures.
An arrangement asdescribed above has proven to be disadvantageous since the contact pressure is exerted mechanically. This is sometimes done directly at the flange or top of the dome. Strong mechanical stresses are thus exerted on the dome in certain locations. Since the glass dome must be mechanically handled every time a semiconductor member is removed from the carrier members, considerable breakage Occurred in the past which could not be eliminated by using a thicker, and thus more costly, dome. On the contrary, a thicker dome increased the cost factor since such a dome is much more costly to produce.
SUMMARY OF THE INVENTION The invention improves on the prior-art reaction containers as described above in such a way that the glass or quartz dome is surrounded by a pressure chamber pressing the dome against the base member. This pressure chamber is filled with a gas at a pressure higher than that of the surrounding atmosphere, and the dome is thus pressed air-tightly against its support by the forces exerted uniformly over the surface of the dome by the pressure gas, in addition to the weight of the dome. Nitrogen may be used as such a pressure gas.
BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a sectional view of a reaction container according to this invention DESCRIPTION OF THE PREFERRED EMBODIMENTS AND METHOD The FIGURE is a preferred embodiment of a reaction container 10 according to this invention comprising perforated base member 12 and a silver plate 14 thereupon, provided with bores 16, 18 and 20 and a circular recess or groove 22. The discharge channel 24 serves for removing the used gas from the reaction chamber through boring 20, and it contains a supply tube 26 with a valve for the fresh reaction gas compound. Borings l6 and I8 serve for mounting electrodes 30 and'32 gas-tightly in the silver plate 14. These electrodes 30 and 32 constitute mounting members for two rod-shaped or tubular carrier members 34 and 36. Their upper ends are connected by a bridge 38 made of a temperature-resistant and electrically conductive material. In another embodiment, the carrier member or members are flat to form semiconductor layers, or the heating is carried out in a different manner.
The quartz or glass dome 9 of the embodiment in the figure has a flange-type margin 42 at its open end, and it rests upon the silver plate 14 at least partially covering the circular recess 22 which contains a sealing ring 44 consisting of a gas-tight, elastic and temperatureresistant material such as a fluorine containing elastomer, a silicon rubber or a sealing grease with the above properties. In other embodiments, the flange 42 is removed or the dome 40 tapers off. The dome and the silver plate 14 may also have mutually adapted contact surfaces, for instance, grindings, replacing any other sealing means.
Otherwise, a sealing ring may consist of an air-tight elastic and temperature-resistant material such as a flourine-containing elastomer or silicon rubber or a high-temperature-resistant sealing grease.
The dome 40 is arched in its closed portion to obtain a better pressure distribution. The pressure container 46 holds the pressure gas. It surrounds the dome 40 and ismounted on the base member 12. It consists of steel or any material which can be easily handled without breakage. This pressure container 46 contains an inlet port 48 for the pressure gas which is preferably an inert gas, in'particular nitrogen or a rare gas. A manometer 50 allows to maintain a desired pressure in the pressure container 46. A pressure-tight window 52 forms a further feature ensuring a perfect operation of the system.
The pressure difference between the outer and inner pressure of the glass or quartz dome 40 which is required for sufficient sealing depends strongly on the size (diameter) of the dome 40 and on the elasticity of the sealing ring 44 or its dimensions. Usually a pressure of 0.5 through I atmospheres should be sufficient.
For the operation of an arrangement according to this invention, the carrier members 34 and 36 are inserted into the mountings constituted by the electrodes 30 and 32 and are connected by the conductive bridge 38. The glass dome 40 is then placed upon the silver plate 14 with the possible insertion of a sealing member 44. Then the pressure-gas container 46 is closed and filled with the inert gas before the reaction gas is placed into the reaction chamber formed by the quartz or glass dome 40, and before the carrier members 34 and 36 are heated. The pressure at this time is 0.5 through 2 atmospheres.
Hereafter, hydrogen is admitted to the reaction chamber, and the electric current is switched on which will heat the carrier members 34 and 36. When the carrier members 34 and 36 are at a sufficiently high temperature, the reaction gas itself, for instance a mixture of H and SiHCl is admitted into the reaction chamber allowing the deposition of the semiconductor material on the hot surfaces of the heated carrier members 34 and 36. It is thereby advantageous to introduce the fresh reaction gas at such pressures into the reaction chamber that it will form a lively current reaching the upper parts of the reaction chamber.
The gas pressure on the outer surface of the glass or quartz dome 40, in particular on its upper side, will result in an air-tight connection with the base 14 without difficulty. If the pressure within the pressure container 46 minus the pressure of the pressure gas is denoted by p and the largest outer radius of the dome 40 is denoted by r, the pressure force K will be K p r (1r 3.1425634). The total vertical force K is now K p r' rr G and the contact pressure due to the dome 40 is whereby r, is the outer radius of the lower dome margin and r is its inner radius. If r, r, and if G is negligibly small as compared with the force due to the pressure gas. the expression for p will simply result in Since the two forces G and p producing the pressure P are uniformly distributed over all parts of the dome, the danger of uneven stresses on the dome 40 and thus of its breakage is avoided to a great extent. lf, in addition, the dome 40 is bent convexly, in particularly evenly, a perfectly stable construction can be obtained with less than 0.5 cm wall strength. The mechanical pressure which must exist at the boundary between base 14 and dome 40, and thus the desired air-tight connection, can be obtained much easier without the danger of damaging the dome 40.
An additional advantage is given by the arrangement as described above since the inert pressure-gas atmosphere surrounding the dome 40 provides a safety factor against a discharge of gas from the reaction chamber which may occur due to a faulty sealing or due to damage of the dome 40 during the operation. The emerging gas would simply mix with the inert gas and become harmless.
Although particular embodiments of the invention have been described and illustrated herein it is recognized that modifications and variations may readily occur to those skilled in the art. It is consequently intended that the claims be interpreted to cover all such modifications and equivalence.
1. An apparatus for the deposition of semiconductor material from a gaseous compound onto a workpiece,
' comprising a base plate having means to support at least one workpiece thereon, including means to heat the workpiece,
a dome covering a portion of said base plate and the means supporting the workpiece,
an outer container mounted on said base plate and enclosing said dome to define a closed pressure chamber therewith,
gas inlet means connected to said outer container for introducing a gas under pressure into said pressure chamber defined by said dome and outer container,
whereby when gas under pressure is introduced into said pressure chamber said dome is positively sealed onto said base plate.
2. An apparatus in accordance with claim 1 wherein said pressure-gas container serves as a safety feature capturing escaping reaction compound gas in the case of a leak.
3. An apparatus in accordance with claim 1 wherein an inert gas is introduced into said pressure-gas container.
4. An apparatus in accordance with claim 1 wherein nitrogen is introduced into said pressure-gas container.
5. An apparatus in accordance with claim 1 wherein a layer of sealing grease is placed between said dome and said base plate to form a gas-tight connection.
6. An apparatus in accordance with claim 1 wherein a resilient temperature resistant material is placed between said dome and said base plate to form a gas-tight connection.