Atomic layer epitaxy (ALE) apparatus for growing thin films of elemental semiconductors

• US 5,281,274 A
• Filed: 02/04/1993
• Issued: 01/25/1994
• Est. Priority Date: 06/22/1990
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Yoder, Max N.
• Primary Examiner(s): Hearn, Brian E.
• Assistant Examiner(s): BASKIN, JONATHAN
• Application Number:
  US08/013,386
• Time in Patent Office: 355 Days
• Field of Search: 118/715, 118/719, 118/723, 118/724, 118/725, 118/730, 118/696
• US Class Current: 118/697
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 25/14 Feed and outlet means for the gases; Modifying the flow of the reactive gases
• CPC Class Codes: C30B 25/18 characterised by the substrate
• CPC Class Codes: C30B 29/02 Elements
• CPC Class Codes: C30B 29/04 Diamond
• CPC Class Codes: C30B 29/06 Silicon
• CPC Class Codes: C30B 29/08 Germanium
• CPC Class Codes: C30B 29/36 Carbides
• CPC Class Codes: C30B 29/52 Alloys
• CPC Class Codes: Y10S 438/909 Controlled atmosphere
• CPC Class Codes: Y10S 438/931 Silicon carbide semiconductor
• CPC Class Codes: Y10S 438/974 Substrate surface preparation

Abstract

An apparatus for and a method of growing thin films of the elemental semiductors (group IVB), i.e., silicon, germanium, tin, lead, and, especially diamond, using modified atomic layer epitaxial (ALE) growth techniques are disclosed. In addition, stoichiometric and non-stoichiometric compounds of the group IVB elements are also grown by a variation of the method according to the present invention. The ALE growth of diamond thin films is carried-out, inter alia, by exposing a plurality of diamond or like substrates alternately to a halocarbon reactant gas, e.g., carbon tetrafluoride (CF₄), and a hydrocarbon reactant gas, e.g., methane (CH₄), at substrate temperatures between 300 and 650 Celsius. A stepping motor device portion of the apparatus is controlled by a programmable controller portion such that the surfaces of the plurality of substrates are given exposures of at least 10¹⁵ molecules/cm² of each of the reactant gases. The chemical reaction time to complete the growth of an individual atom layer is approximately 25×10^-6 second.

Claims

1. A growth apparatus for atomic layer epitaxial (ALE) growth of thin films upon the surfaces of a plurality of substrates of the elemental semiconductors comprising:

a growth reactor chamber means for securing said plurality of substrates therein to allow the growth of thin films upon said surfaces thereof;

a purge means operatively connected to said growth reactor chamber means for evacuating all impurities therefrom and to purge clean said surfaces of said plurality of substrates;

a heater means operatively connected to said growth reactor chamber means for maintaining a predetermined purge temperature within a range of purge temperatures, and a predetermined growth temperature within a range of growth temperatures on said surfaces of said plurality of substrates;

a first reactant gas means operatively connected to said growth reactor chamber means for flooding thereof with a first reactant gas so as to expose said surfaces of said plurality of substrates thereto;

a second reactant gas means operatively connected to said growth reactor chamber means for flooding thereof with a second reactant gas so as to expose said surfaces of said plurality of substrates thereto; and

a differential pressure means operatively connected to said growth reactor chamber means for desorbing said surfaces of said plurality of substrates of all physisorbed species of said first and second reactant gases and for maintaining a predetermined purge pressure within a range of purge pressures and a predetermined growth pressure within a range of growth pressures in said growth reactor chamber means.

2. The growth apparatus of claim 1 wherein said growth reactor chamber means further includes:

a first reactant gas sub-chamber integrally affixed to said growth reactor chamber means and operatively connected to said first reactant gas means;

a second reactant gas sub-chamber integrally affixed to said growth reactor chamber means and operatively connected to said second reactant gas means;

a first vacuum sub-chamber integrally affixed to said growth reactor chamber means and said first and second reactant gas sub-chambers, said first vacuum sub-chamber being operatively connected to said differential pressure means; and

a second vacuum sub-chamber integrally affixed to said growth reactor chamber means and said first and second reactant gas sub-chambers, said second vacuum sub-chamber being operatively connected to said differential pressure means.

3. The growth apparatus of claim 2 wherein said growth reactor chamber means further includes a tailpipe means integrally affixed to said first and second reactant gas sub-chambers, and said first and second vacuum sub-chambers so as to form a portion thereof, said tailpipe means being operatively connected to said purge means and said differential pressure means.

4. The growth apparatus of claim 3 wherein said tailpipe means further includes:

a first plurality of ventholes configured in said tailpipe means so as to exit into said first vacuum sub-chamber; and

a second plurality of ventholes configured in said tail pipe means so as to exit into said second vacuum sub-chamber;

said first and second plurality of ventholes in cooperation with said differential pressure means operating to maintain said first and second vacuum sub-chambers at a lower operating pressure than that of said first and second reactant gas sub-chambers.

5. The growth apparatus of claim 3 wherein said differential pressure means further includes:

a first high capacity vacuum pump operatively connected to said tailpipe means; and

a second high capacity vacuum pump operatively connected to said growth reactor chamber means so as to permit said first and second vacuum sub-chambers to operate at a differentially lower pressure than said first and second reactant gas sub-chambers.

6. The growth apparatus of claim 2 wherein said growth reactor chamber means further includes a pedestal being rotatably affixed to said growth reactor chamber means for securing said plurality of substrates and for rotating them through said first and second reactant gas sub-chambers and said first and second vacuum sub-chambers in accordance with a predetermined timing and switching sequence.

7. The growth apparatus of claim 6 wherein said pedestal is operatively connected to a stepper motor device such that said pedestal is rotated in accordance with the predetermined timing and switching sequence.

8. The growth apparatus of claim 1 wherein said purge means further includes:

a high vacuum purge pump means operatively connected to said growth reactor chamber means for evacuating any residual impurities therefrom;

a purge gas means operatively connected to said growth reactor chamber means for flooding thereof with a purge gas so as to expose said surfaces of said plurality of substrates thereto; and

a radio frequency coil plasma device operatively connected to said growth reactor chamber device for striking a plasma of said purge gas so as to remove any oxide that may have accumulated and to hydrogenate said surfaces of said plurality of substrates.

9. The growth apparatus of claim 8 wherein said high vacuum purge pump means further includes a purge pump control valve operatively connected between said growth reactor chamber means and said high vacuum purge pump means for adjusting the pressure in said growth reactor chamber means to a predetermined value prior to flooding thereof with said purge gas.

10. The growth apparatus of claim 8 wherein said purge gas means further includes:

a purge gas container for containing said purge gas;

a purge gas control valve operatively connected between said growth reactor chamber means and said purge gas container for adjusting the amount of said purge gas available to said growth reactor chamber means; and

a purge gas flow controller operatively connected between said growth reactor chamber means and said purge gas control valve for adjusting the flow rate of said purge gas to a predetermined value.

11. The growth apparatus of claim 1 wherein said first reactant gas means further includes:

a first reactant gas container for containing said first reactant gas;

a first reactant gas control valve operatively connected between said growth reactor chamber means and said first reactant gas container for adjusting the amount of said first reactant gas available to said growth reactor chamber means; and

a first reactant gas flow controller operatively connected between said growth reactor chamber means and said first reactant gas control valve for adjusting the flow rate of said first reactant gas to a predetermined value.

12. The growth apparatus of claim 1 wherein said second reactant gas means further includes:

a second reactant gas container for containing said first reactant gas;

a second reactant gas control valve operatively connected between said growth reactor chamber means and said second reactant gas container for adjusting the amount of said second reactant gas available to said growth reactor chamber means; and

a second reactant gas flow controller operatively connected between said growth reactor chamber means and said first reactant gas control valve for adjusting the flow rate of said second reactant gas to a predetermined value.

13. The growth apparatus of claim 1 further including a programmable controller operatively connected to said growth reactor chamber means, said purge means, said heater means, said first reactant gas means, said second reactant gas means and said differential pressure means so as to automatically control the ALE growth of said thin films upon said surfaces of said plurality of substrates according to a predetermined program.