Apparatus For Growing Films

Abstract

Vapor deposition apparatus has a closed chamber formed by a first platelike member having a recess to receive evaporant source material and a shoulder in the top surface thereof to support a substrate closely spaced from said source material and with the substrate back surface generally flush with said top surface. A second plate member overlies said top and back surfaces and in sealing relationship therewith. Means communicate said space with a gaseous medium.

Description

SUMMARY OF INVENTION

The present invention relates to an apparatus to be used as a reactor for the transfer of semiconductor material on a substrate by use of close spaced vapor transport. The invention essentially relies on an apparatus which permits the source and substrate materials to be separated by a well defined spatial relationship and permits independent temperature control of the source and substrate materials.

OBJECTS

It is the object of the present invention to provide an apparatus making possible the deposition of thin films of semiconductor materials on a substrate using closed spaced vapor transport.

Further objects and features of the apparatus described in the present invention will be more readily understood from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing is a cross sectional view of the reactor constructed in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now specifically to FIG. 1, the apparatus therein illustrated consists of four main components. The first of these is the heat source 1, the lower plate 3, the upper plate 4, and the heat sink 2. The heat source 1 is exterior to the reactor and may be of any controllable type of sufficient capacity. The necessary capacity of the heat source 1 will be determined by considering the temperature that must be maintained by the source material 7 and the volume of the reactor itself.

The second component of the reactor the lower plate 3 may be made of any nonreactive nonporous material, e.g., fused quartz. The size of the lower plate 3 will generally vary in relation to the size and shape of the source 7 and substrate 9 materials used. Lower plate 3 in the preferred embodiment has three distinct configurations. The first is the lower recess 6 whose main function is to serve as a holder for the source material 7. Therefore, the size and shape of the lower recess is determined by the size and shape of the source material 7 used.

Also formed in the lower plate 3 is the upper recess 8. The upper recess is a lip which serves as a support for the substrate 9 material. The depth and size of upper recess 8 is generally determined by the size and shape of the substrate 9 material which is chosen. However, there are two important considerations in determining the depth of the upper recess 8. The first is that the distance 10 between the bottom of the substrate 9 and top of the source 7 material is critical. The distance shown as 10 in FIG. 1 can range from 0.002 to 0.040 inch with an optimum distance of 0.010 inch. Another important consideration is the top surface of the substrate 9 material is maintained level with the top of the lower plate 3. Thus, when the lower plate 3 and upper plate 4 are clamped together an enclosed chamber is formed and the top of the substrate 9 is in contact with the bottom surface of the upper plate 4.

Finally there is formed in the lower plate 3 the gas channel 16. As shown in FIG. 1 the gas channel 16 provides an entrance 16a and exit 16b for the atmosphere used in the reactor. The size of the gas channel is not crucial.

The upper plate 4 is made of the same material that is chosen for the lower plate 3, for example, fused quartz. The upper plate 4 also has gas channels 16a and 16b which match those of the lower plate 3. The gas channels 16a and 16b in the upper plate 4 serve as extensions for those in the lower plate 3.

The heat sink 2 is exterior to the reactor and may be of any controllable type. The capacity of the heat sink 2 needed will depend on the volume of the reactor and temperature at which it is desired to maintain the substrate 9 materials.

Because of the control possible over source 7 and substrate 9 temperatures, many combinations of source 7 and substrate 9 materials will be feasible which were not possible in the prior art processes. To illustrate the operation of this apparatus comprising the preferred embodiment of FIG. 1, Al.sub.2 O.sub.3 is used as the substrate 9 and InAs is used as the source 7 material. The deposition of a source material such as InAs on a substrate like Al.sub.2 O.sub.3 is accomplished using this embodiment by the following procedure:

A section of the source material 7, InAs, is placed in lower recess 6 of the reactor. Next the substrate 9 material, Al.sub.2 O.sub.3, is put in the upper recess 8. When the source 7 and substrate 9 materials are in position their adjacent surfaces are parallel and separated at 10 by a distance in the order of 0.010 inch.

After the source 7 and substrate 9 materials are in place, the upper 4 and lower 3 plates are clamped together forming an enclosed chamber. The heat generator 1 is turned on and the reaction chamber is filled at inlet 16a with an appropriate atmosphere, in this example H.sub.2 and AsCl.sub.3 vapor is used.

The heat from generator 1 applied to the bottom of the chamber causes the source material 7 to heat more rapidly than the substrate 9. During this transient condition the substrate's 9 temperature lag sets up the proper conditions for the nucleation process.

In this embodiment the source 7 material 7 is heated to 800.degree. C. while the temperature of the substrate is maintained below 700.degree. C. by using the heat sink 2. After the substrate 9 has been coated with InAs, the temperature of the substrate 9 is allowed to rise above 700.degree. C. in order to decrease the nucleation rate on what is now a surface covered with InAs. Thus by raising the substrate 9 temperature as soon as the nuclei on the Al.sub.2 O.sub.3 have reached critical size, the nucleation rate is decreased and optimum crystal structure is obtained.

To shut down the reactor, the heat source is turned off, the atmosphere is allowed to leave via outlet 16b the reaction chamber, and the reactor is allowed to return to ambient conditions.

Claims

What is claimed is:

1. Apparatus for growing semiconductor films on a substrate by close spaced vapor transport comprising:

A. means forming a nonreactive, closed chamber for positioning a semiconductive source material and a substrate in a predetermined spaced coplanar relationship to one another;

B. said means comprising a first platelike member having a recessed portion adapted to contain the source material and an outwardly facing shoulder portion formed in the top surface and the wall defining said recessed portion;

C. said shoulder portion adapted to support and maintain the substrate in said spaced relationship and with the substrates back surface lying generally flush with the top surface of said first member;

C. said means including a second plate member overlying said top surface and substrate and in sealing relationship therewith;

D. means communicating the enclosed space between said substrate and source material to a predetermined gaseous atmosphere;

E. a heat source disposed external to said chamber and adjacent said platelike member whereby to evaporate the source material; and

F. a heat sink disposed external to said chamber and adjacent said second plate member.

2. Apparatus for the growing of film on a substrate as set forth in claim 1 wherein said space maintained is in the order of 0.002 to 0.040 inch.

3. Apparatus as set forth in claim 1 wherein the nonreactive material comprising said means (A) is quartz.

4. Apparatus as set forth in claim 1 wherein said means (D) includes an inlet passage and an outlet passage disposed in said means (A) which communicate with the space between said source material and said substrate.