|Publication number||US3325314 A|
|Publication date||Jun 13, 1967|
|Filing date||Aug 27, 1965|
|Priority date||Oct 27, 1961|
|Publication number||US 3325314 A, US 3325314A, US-A-3325314, US3325314 A, US3325314A|
|Inventors||John E Allegretti|
|Original Assignee||Siemens Ag|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (1), Referenced by (12), Classifications (21)|
|External Links: USPTO, USPTO Assignment, Espacenet|
June 13, i 967 J, E. ALLEF'GRETTI 3,325,314
SEMI-CONDUCTOR PRODUCT AND METHOD FOR MAKING SAME Original Filed Oct. 27, 1961 2 Sheets-Sheet 1 'Tlcil.
INVENTCSR JOHN E.ALLEGRETTI ATTORNE June 13, 967 J. E. ALLEGRETTI 3,325,314
SEMI-CONDUCTOR PRODUCT AND METHOD FOR MAKING SAME Original Filed Oct. 2'7, 1961 2 Sheets-Sheet 2 INVENTOR JOH E. ALLEGRETTI United States Patent 3,325,314 SEMI-CONDUCTOR PRODUCT AND MUETHOD FOR MAKING SAME John E. Allegrctti, East Brunswick, NJ, assignor to Siemens & Halslre Aktiengesellschaft, Berlin and Munich, Germany, a corporation of Germany Continuation of application Ser. No. 148,253, Oct. 27, 1961. This application Aug. 27, 1965, Ser. No. 497,581 4 Claims. (Cl. l48--1'75) This invention is a continuation of my copending application Ser. No. 148,253 filed Oct. 27, 1961, now abandoned, and relates to single crystal silicon semiconductor bodies grown from the vapor phase by thermal decomposition and, more particularly, it relates to a method of growth of silicon semiconductor layers having a flat, imperfection-free surface.
The process of deposition of silicon semiconductor material and active impurities therewith onto a single crystal silicon semiconductor substrate from the vapor phase by simultaneous thermal decomposition of a silicon compound and active impurity compounds therewith in the presence of hydrogen is well known in the art. What is found is that thermal decomposition of silicon under these conditions produces surfaces with one or more surface imperfections. For example, the surface may exhibit pyramidal growth, both rectangular and triangular in shape. Other imperfections manifest themselves in the form of pitting and growth stops wherein small hillocks are present on the surface, or as thickness deformities which occur in the form of a coarse texture or shingle appearance on the surface. As will be apparent to others skilled in the art, the availability or vapor-grown, flat, imperfection-free, single crystal semiconductor surfaces would enable the fabrication of semiconductor devices of improved quality.
An object of this invention is to provide a single crystal silicon semiconductor body including a plurality of layers of single crystal silicon semiconductor material of different conductivity separated by a transition region wherein said body has a flat, imperfection-free surface.
Still another object of the instant invention is to provide a single crystal silicon semiconductor body by growth from the vapor phase having a surface layer which has a substantially improved surface quality, by growth onto a single crystal silicon semiconductor substrate having a predetermined crystal orientation.
Among the other objects of the invention is to provide a method of making such bodies by thermal decomposition from the vapor phase.
These and other objects will be made apparent from the following more detailed description of the invention, in which reference will be made to the accompanying drawings, in which:
FIGURE 1 is a photolithographic reproduction of the surface characteristics of a single crystal silicon semiconductor layer formed by growth from the vapor phase; and regions marked A illustrate the imperfection-free surfaces produced according to the present invention, whereas those designated as B and C are indicative of the characteristics of surfaces produced in the prior art;
FIGURE 2 is a more detailed view of region B;
FIGURE 3 shows regions A and C under high magnification;
FIGURE 4 is an interference pattern of regions A and C;
FIGURE 5 is a schematic illustration, in section, of a silicon semiconductor substrate oriented in accordance with the present invention; and
FIGURE 6 shows a manner of preparing oriented sub strates in accordance with the invention starting with a single crystal of semiconductor material.
In accordance with the present invention there is provided a single crystal silicon semiconductor body including a plurality of layers of single crystal semiconductor material, and wherein the surface layer of the body has a substantially improved surface quality. The semiconductor bodies produced herein have surfaces which are exceedingly fiat and imperfection-free. In a preferred form of the present invention, single crystal semiconductor bodies having such improved surface qualities are prepared by thermal decomposition from the vapor phase onto a single crystal silicon semiconductor substrate which is oriented in a preferred manner. In particular, in the present invention, a silicon substrate is oriented at least three-eighths of a degree and not more than five degrees off orientation from a low order Miller Indices growth plane. In a specific embodiment of the invention, silicon semiconductor bodies having fiat, imperfectionfree surfaces are produced by orienting the substrate in the aforementioned predetermined amount off orientation in the  plane of the crystal along a  211 direction.
As another feature of the present invention there is provided a method of making such silicon semiconductor bodies having these improved surface qualities by growth from the vapor phase. In accordance with this method, growth from the vapor phase is effected by thermal decomposition of a semiconductor material and active impurities therewith in the presence of hydrogen onto a silicon semiconductor substrate oriented in a predetermined manner at deposition temperatures in the range of 1150-1200 C.
The process of growth from the vapor phase employed in the formation of semiconductor bodies in accordance with the invention utilizes known thermal semiconductor materials with the only criterion being that a decomposable vapor source of the material be available. The terms thermally decomposable, thermal decomposition and the associated deposit of a product. of decomposition, as used herein, are intended to be generic to the mechanisms of heat-cracking as, for example, the decomposition of silicochloroform or silicon tetrachloride and liberation of silicon atoms through the mechanism of high temperature reactions wherein the high temperature causes interaction between various materials with liberation of specific materials or atoms as, for example, the reaction of silicochloroform and hydrogen:
used in the preferred embodiments of this invention as hereinafter indicated.
Single crystalline silicon semiconductor bodies in accordance with the invention may he formed, in general, utilizing the apparatus and techniques described in the teachings of patent application SN. 86,239 by Benzing, Krsek and Topas, filed Jan. 31, 1961, and now Patent No. 3,131,098. As is disclosed in the Benzing et a1. application, semiconductor material is deposited upon a heated essentially single crystal semiconductor starting element from a decomposable source thereof in a reaction chamber. After a predetermined period of time during which the desired thickness of semiconductor material has been deposited, the reaction chamber is flushed with a gas to remove unwanted atoms of active impurity therefrom. Thereafter, additional semiconductor decomposable source material and atoms of active impurity of a desired type and degree are introduced into the reaction chamber and an additional layer of desired thickness of semiconductor material is deposited in essentially single crystalline form contiguous with the layer of material previously deposited. This process may be continued until such a time as the desired numbers of layers of semiconductor material of alternating conductivity type or degree, each having a junction separating it from the adjacent layer, are formed. As is evident, any desired number of layers of material, and any desired number of junctions, may be formed in accordance with any given design considerations.
Referring now to FIGURE 1, there is shown an actual photolithographic reproduction of the surface of a single crystal silicon layer formed by thermal decomposition of silicochloroform and hydrogen at 1150-1200 C. onto a single crystal silicon substrate oriented in a predetermined manner. In particular, the substrate is formed by providing a 4 arc of curvature from a  plane of the crystal, thereby exposing a number of crystal planes which are close to a  plane. In this manner, it is possible to illustrate in a single experiment the characteristics of layers formed on different substrate crystal planes. As may be seen in the drawing, certain regions contain surface imperfections characteristic of those surfaces previously obtained in the art. On the other hand, other regions exhibit a surface which is substantially imperfection-free. It is the latter surfaces which are characteristic of those produced according to the present invention and which are so dramatically to be distinguished from those produced in the past.
As may be observed, the region marked A in FIGURE 1 is essentially clear and free of any undesirable surface imperfections. The regions marked B and C, however, have one or more surface imperfections. Region B, for example, is illustrative of a pyramidal growth imperfection. FIGURE 2 shows this type of growth in more detail. Region C contains a form of surface imperfection called hillock-ty pe growth. FIGURE 3 shows region C under high magnification.
In FIGURE 4 there is shown the interference pattern, characteristic of regions A and C, under optical examination. What is shown therein is that the surface layer in region A is substantially free of distorting interference patterns, which indicates that the region is free of surface imperfections. Stated in more mathematical terms, region A has less than one interference line across 20 mm. of the surface thereof. Region C, on the other hand, has very many such lines in the same length.
The desired type of surface quality exhibited in region A occurs on that portion of the silicon crystal which is oriented at least /8 of a degree and not more than 5 off orientation from a  plane in the 211 direction of the crystal. Single crystal silicon semiconductor substrates which are oriented in this manner, have on an atomic scale, a number of atoms of semiconductor material arranged in the form of steps. This stepwise arrangement exposes a large number of atomic layers of the material, as illustrated in FIGURE 5. In a given length of exposed surface there are a number of exposed atomic layers, the exact number varying with the extent to which the crystal is oriented off from a low Miller indices crystal plane. For example, if the silicon crystal is oriented of a degree off orientation there are 1.42 atomic layers exposed per centimeter of length of the crystal. At a preferred 1.5 off orientation from the  plane, there are 4.9x 10 such exposed atomic layers, and at 5 there are 1.9 10 exposed atomic layers. In order to achieve the desired imperfection-free growth it is necessary that the number of exposed atomic layers be within the limits enumerated above.
FIGURE 6 illustrates a manner of preparation of a suitably oriented silicon single crystal substrate 10 in accordance with the invention. A cut along the lines 11- 12 is made in the single crystal body in the manner shown at an angle 0, thereby exposing a surface 13. The cut is made 0 degrees off  orientation in the '2 11 direction of the crystal.
What has been described is a method for producing single crystal silicon semiconductor bodies having improved surface qualities. In a preferred form of the invention a silicon crystal substrate is provided which is oriented at least of a degree and not more than five degrees off orientation from a  plane of the crystal in the 11 direction. Then a layer of silicon is deposited thereon by thermally decomposing silicochloroform and hydrogen at 1l501200C. The layer thus formed has a clear, flat and substantially imperfectionfree surface and the same orientation as that of the substrate.
While the invention has been described with particular reference to the formation of an individual semiconductor body having improved surface qualities, it will be understood that a plurality of such bodies may be formed simultaneously. Within the temperature ranges specified herein, a plurality of such bodies may be formed without appreciable diffusion of impurities from one body to another during the deposition process.
1. A method for epitaxial depositing monocrystalline silicon from the gaseous phase onto a heated substrate which comprises epitaxially vapor-depositing monocrystalline silicon at least primarily on a flat deposition surface which departs at least /8 of a degree and not more than 5 degrees off orientation from a  plane of the crystal in the ll direction.
2. A single crystal silicon semiconductor body comprising a substrate of single crystal silicon semiconductor material of predetermined conductivity oriented at least of a degree and not more than 5 degrees off orientation from a  plane of the crystal in the 11 direction and a single crystal silicon semiconductor material, of conductivity different from that of said substrate layer, vapor-deposited by thermal decomposition on said substrate layer, said vapor-deposited layers having a clear, flat, substantially imperfection-free surface and having the same orientation as the substrate.
3. A single crystal silicon semiconductor body comprising a substrate of single crystal silicon semiconductor material of predetermined conductivity oriented at least /8 of a degree and not more than 5 degrees off orientation from a  plane of the crystal in the 11 direction and a single crystal silicon semiconductor material, of conductivity different from that of said substrate layer, formed by thermal decomposition from the vapor phase on said substrate layer, said vapor-deposited layers having a clear, flat substantially imperfection-free surface characterized by having less than one interference line per 20 mm. of length across said surface and having the same orientation as the substrate.
4. A single crystal silicon semiconductor body comprising a substrate of single crystal silicon semiconductor material doped to one conductivity oriented at least of a degree and not more than five degrees off orientation from a low Miller indices plane, the highest Miller index not exceeding 2, and a single crystal silicon semiconductor material of conductivity different from that of said substrate layer vapor-deposited by thermal decomposition on said substrate layer, said vapor-deposited layers having a clear, flat, substantially imperfection-free surface and havin gthe same orientation as the substrate.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3200001 *||Apr 19, 1962||Aug 10, 1965||Siemens Ag||Method for producing extremely planar semiconductor surfaces|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3476592 *||Jan 14, 1966||Nov 4, 1969||Ibm||Method for producing improved epitaxial films|
|US3933985 *||Sep 24, 1971||Jan 20, 1976||Motorola, Inc.||Process for production of polycrystalline silicon|
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|U.S. Classification||148/33.4, 257/E29.4, 257/628, 117/101, 117/902, 257/E21.123, 148/DIG.115, 148/33, 148/33.3, 423/350|
|International Classification||H01L21/20, H01L29/04, C30B23/00|
|Cooperative Classification||H01L29/045, C30B23/005, H01L21/2015, Y10S148/115, Y10S117/902|
|European Classification||C30B23/00, H01L29/04B, H01L21/20B6|