Thermal oxidation method utilizing atomic oxygen to reduce dangling bonds in silicon dioxide grown on silicon

• US 6,509,283 B1
• Filed: 05/13/1998
• Issued: 01/21/2003
• Est. Priority Date: 05/13/1998
• Status: Expired due to Term

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Thomas, Michael E.
• Primary Examiner(s): Zarabian, Amir
• Assistant Examiner(s): GUERRERO, MARIA F
• Application Number:
  US09/076,960
• Time in Patent Office: 1,714 Days
• Field of Search: 438/439, 438/765, 438/778, 438/787, 438/788, 438/624, 438/762, 438/769, 438/770
• US Class Current: 438/787
• CPC Class Codes: H01L 21/0214 the material being a silicon oxynitride, e.g. SiON or SiON:H
• CPC Class Codes: H01L 21/02238 silicon in uncombined form, i.e. pure silicon
• CPC Class Codes: H01L 21/02249 formation by combined oxidation and nitridation performed simultaneously
• CPC Class Codes: H01L 21/02255 formation by thermal treatment H01L21/02252 takes precedence; after treatment of an insulating film H01L21/3105 and subgroups
• CPC Class Codes: H01L 21/31662 of silicon in uncombined form

Abstract

Atomic oxygen, or a mixture of atomic oxygen and atomic nitrogen, is utilized in thermally oxidizing silicon to form a layer of silicon dioxide, or nitrogen-doped silicon dioxide, on a surface of the silicon. Use of atomic oxygen (or O⁻+N⁻) provides a better stoichiometric silicon dioxide structure with fewer dangling bonds than results from standard oxidation processes. The atomic oxygen (or O⁻+N⁻) may be generated within the oxidation furnace, for example by passing the gas through a heated ceramic material (e.g., Al₂O₃) or by using internal UV radiation of the oxygen gas. Alternatively, the atomic oxygen (or O⁻+N⁻) may be generated at a remote source, for example in a plasma reactor, and then introduced to the oxidation furnace. Atomic chlorine can be generated and used prior to the oxidation step for pre-cleaning the silicon surface.

Claims

1. A method of thermally oxidizing silicon to form a layer of silicon dioxide on a surface of the silicon, the method comprising:

placing the silicon and a ceramic material in a furnace;

passing oxygen gas through the ceramic material to generate atomic oxygen,

introducing the atomic oxygen to the surface of the silicon; and

heating the silicon surface such that the silicon reacts with the atomic oxygen to form the layer of silicon dioxide on the surface of the silicon.

2. A method as in claim 1, and wherein the step of introducing atomic oxygen includes simultaneously introducing atomic nitrogen such that the heating step results in formation of a layer of nitrogen-containing silicon dioxide on the surface of the silicon.

3. A method as in claim 1, and wherein the atomic oxygen is generated within the furnace.

4. A method as in claim 1, and wherein the atomic oxygen is generated outside the furnace and provided to the interior of the furnace for introduction to the surface of the silicon.

5. A method as in claim 1, and wherein the surface of the silicon is pre-cleaned using atomic chlorine prior to introducing the atomic oxygen to the surface of the silicon.

6. A method of thermally oxidizing silicon to form a layer of silicon dioxide on a surface of the silicon, the method comprising:

placing the silicon and a ceramic material in a furnace;

introducing an inert gas into the furnace;

pre-heating the surface of the silicon to a first temperature in the presence of the inert gas such that the presence of the inert gas substantially inhibits oxidation of the silicon surface during the pre-heating step;

passing oxygen gas through the ceramic material, and simultaneously heating the ceramic material to a second temperature that is greater than the first temperature such that the passing of the oxygen gas through the heated ceramic material generates atomic oxygen that reacts with the silicon to form the layer of silicon dioxide on the surface of the silicon.

7. A method as in claim 6, and wherein the step of passing oxygen gas through the ceramic material includes simultaneously passing nitrogen gas through the ceramic material to generate atomic nitrogen thereby resulting in formation of a layer of nitrogen-containing silicon dioxide on the surface of the silicon.

8. A method as in claim 6, and wherein the inert gas is argon.

9. A method as in claim 6, and wherein the ceramic material comprises aluminum oxide.

10. A method as in claim 9, and wherein the first temperature is about 500°

C.

11. A method as in claim 10, and wherein the second temperature is about 1000°

C.

12. A method of thermally oxidizing a silicon substrate to form a layer of silicon dioxide on the surface of the silicon substrate, the method comprising:

placing the silicon substrate and ceramic material in a fast ramp furnace;

introducing an inert gas into the fast ramp furnace;

pre-heating the silicon substrate to a first temperature in the presence of the inert gas such that the presence of the inert gas substantially inhibits oxidation of the silicon substrate during the pre-heating step;

passing chlorine gas through the ceramic material such that the chlorine gas dissociates to generate atomic chlorine for pre-cleaning the surface of the silicon substrate;

removing chlorine constituents from the fast ramp furnace;

passing oxygen gas through the ceramic material, and simultaneously heating the ceramic material to a second temperature that is greater than the first temperature such that the passing of the oxygen gas through the heated ceramic material generates atomic oxygen that reacts with the silicon substrate to form the layer of silicon dioxide on the surface of the silicon substrate.

13. A method as in claim 12, and wherein the ceramic material is selected from the group consisting of Al₂O₃, ZrO₂, and Y₂O₃.

14. A material as in claim 12, and wherein the inert gas comprises argon.