Dopant activation anneal to achieve less dopant diffusion (better USJ profile) and higher activation percentage

• US 7,968,441 B2
• Filed: 10/08/2008
• Issued: 06/28/2011
• Est. Priority Date: 10/08/2008
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Xu, Zhi
• Primary Examiner(s): Picardat; Kevin M
• Application Number:
  US12/247,448
• Publication Number:
  US 20100087052A1
• Time in Patent Office: 993 Days
• Field of Search: 438/474, 438/530, 438/710, 438/711, 438/715, 438/723, 438/906
• US Class Current: 438/530
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32357 Generation remote from the workpiece, e.g. down-stream
• CPC Class Codes: H01L 21/2236 from or into a plasma phase
• CPC Class Codes: H01L 21/324 Thermal treatment for modifying the properties of semiconductor bodies, e.g. annealing, sintering H01L21/20 - H01L21/288 and H01L21/302 - H01L21/322 take precedence

Abstract

A method and apparatus for forming a semiconductor device. A semiconductor substrate is implanted with dopants. The substrate is subjected to a cleaning process employing electrically neutral nitrogen and fluorine radicals to produce an oxygen-free surface having dangling bonds. Before any further exposure to oxidizing gases, the substrate is annealed by thermal treatment to activate and distribute the dopants. A gate oxide layer is formed over the annealed surface. The apparatus performs all such treatments without breaking vacuum.

Claims

1. A method of processing a doped semiconductor substrate, comprising:

disposing the doped semiconductor substrate in a processing chamber;

providing a cleaning gas comprising a mixture of ammonia, nitrogen trifluoride, and a carrier gas to the processing chamber;

converting a portion of the cleaning gas to neutral radicals by applying RF power;

forming a sublimation layer on the doped semiconductor substrate by exposing the substrate to the cleaning gas while cooling the substrate;

forming an oxygen-free surface on the doped semiconductor substrate by heating the sublimation layer; and

activating the dopants in the doped semiconductor substrate by an annealing process, wherein a partial pressure of oxidizing gases is maintained below about 1 mTorr during the aforementioned disposing, providing, converting, forming, forming, and activating.

2. The method of claim 1, wherein the substrate temperature is maintained below about 100°

C. while forming the sublimation layer.

3. The method of claim 1, wherein heating the sublimation layer comprises positioning the sublimation layer proximate to a hot showerhead.

4. A process for forming a device on a substrate, comprising:

implanting dopants into a surface of the substrate;

terminating the implanted surface with dangling bonds by exposing the substrate to a reducing gas at a temperature less than about 100°

C.;

activating the dopants by heating the implanted surface of the substrate; and

forming an oxide layer over the implanted surface.

5. The process of claim 4, wherein the reducing gas comprises nitrogen and fluorine.

6. The process of claim 5, wherein terminating the implanted surface with dangling bonds comprises forming a sublimation layer over the implanted surface, and removing the sublimation layer by positioning the sublimation layer proximate to a hot showerhead and heating the sublimation layer to a temperature at or above 100°

C.

7. The process of claim 4, wherein the reducing gas comprises electrically neutral radicals.

8. The process of claim 7, wherein the reducing gas comprises nitrogen and fluorine radicals, and the reducing gas forms a sublimation layer on the substrate that is subsequently removed by heating to a temperature at or above 100°

C.

9. The process of claim 8, wherein the implanted surface of the substrate is hydrogen-terminated at the time the dopants are activated by heating.

10. The process of claim 4, wherein implanting dopants into the substrate surface, terminating the substrate surface with dangling bonds, and activating the dopants are all performed in a substantially oxygen-free atmosphere that is maintained during and between the implanting, terminating, and activating processes.

11. The process of claim 10, wherein forming an oxide layer over the implanted surface comprises exposing the implanted surface to an oxidizing gas in the presence of RF power.

12. A method of forming a device on a substrate, comprising:

implanting dopants into a surface of the substrate;

disposing the substrate in a processing chamber configured to produce a charge-free reducing gas comprising neutral radicals;

applying RF energy at a remote location to form neutral radicals comprising nitrogen and fluorine;

flowing the neutral radicals into the processing chamber and exposing the doped surface of the substrate to the neutral radicals;

reacting the neutral radicals with the substrate surface at a temperature less than about 100°

C. to form a thin film;

removing the thin film by heating a fixture of the processing chamber, positioning the fixture near the substrate surface, and heating the substrate surface;

generating dangling bonds on the substrate surface;

activating the dopants using a furnace annealing process; and

forming an oxide layer over the implanted surface.

13. The method of claim 12, wherein the furnace annealing process comprises heating the substrate surface to a temperature less than about 850°

C.