METHOD OF SUPPORTING A SUBSTRATE IN A GAS CUSHION SUSCEPTOR SYSTEM

• US 20060222481A1
• Filed: 06/16/2006
• Published: 10/05/2006
• Est. Priority Date: 03/08/2002
• Status: Active Grant

• Current Assignee: ASM IP Holding B.V. (ASM International NV)
• Original Assignee: Michael Todd Foree
• Inventors: Foree, Michael Todd
• Granted Patent: US 7,601,224 B2
• Time in Patent Office: Days
• US Class Current: 414/800
• CPC Class Codes: C23C 16/45521 the gas, other than thermal contact gas, being introduced the rear of the substrate to flow around its periphery
• CPC Class Codes: C23C 16/4584 the substrate being rotated
• CPC Class Codes: C30B 25/12 Substrate holders or susceptors
• CPC Class Codes: H01L 21/6838 with gripping and holding devices using a vacuum; Bernoulli devices

Abstract

An apparatus and method to position a wafer onto a wafer holder and to maintain a uniform wafer temperature is disclosed. The wafer holder or susceptor comprises a recess or pocket whose surface includes a grid containing a plurality of grid grooves that separate protrusions. A plurality of gas passages is provided in the susceptor to enable an upward flow of gas toward the bottom surface of the substrate. During drop-off of the substrate, a cushion gas flow is provided to substantially slow the rate of descent of the substrate onto the susceptor and to gradually heat the substrate before it makes contact with the susceptor. Optionally, a trickle gas flow may be provided through the aforementioned passages during processing of the substrate to prevent deposition of reactant gases onto the bottom surface of the substrate. A liftoff gas flow may then be provided through the passages to help lift the substrate off of the susceptor after processing is completed and thus aid in removing the substrate from the process chamber. These features help to achieve temperature uniformity and thus quality of deposited films onto the substrate.

Claims

1. A method of supporting a substrate, comprising:

releasing a substrate above a support surface of a susceptor, such that said substrate is permitted to descend toward said support surface by gravitational force;

providing a cushioning flow of gas upwardly through a plurality of gas passages provided in said susceptor, said cushioning gas flow providing an upwardly directed force onto said substrate, the flow rate of said cushioning gas flow being sufficient to slow the rate of descent of said substrate to a rate no greater than one half of the rate at which said substrate would descend under gravity alone; and

permitting said substrate to come into contact with said support surface.

2. The method of claim 1, wherein said susceptor includes a plurality of outer gas passages positioned just radially outward of a peripheral edge of said substrate when said substrate is centered upon said support surface of said susceptor, said outer gas passages being substantially vertical so that upward gas flow through said outer gas passages flows substantially vertically upward above said susceptor, said method further comprising providing gas flow through said outer gas passages to counteract sideward sliding of said substrate.

3. The method of claim 2, wherein said gas flow is provided through said outer gas passages while said substrate descends toward said support surface of said susceptor.

4. The method of claim 2, wherein said gas flow is provided through said outer gas passages while said substrate is in contact with said support surface of said susceptor.

5. The method of claim 1, wherein said cushioning flow of gas exits each of said gas passages at said support surface by flowing upward and radially outward.

6. The method of claim 1, said support surface having a plurality of grooves extending radially outward beyond the peripheral edge of said substrate, said method further comprising:

providing a trickle flow of gas through said plurality of gas passages after said substrate comes into contact with said support surface and while processing said substrate, the flow rate of said trickle gas flow being sufficient to cause said gas to flow under said substrate through said grooves and upward around a peripheral edge of said substrate without disrupting contact between said substrate and said support surface.

7. The method of claim 1, further comprising:

after said substrate is in contact with said support surface, providing a liftoff flow of gas through said plurality of gas passages, said liftoff gas flow being sufficient to lift said substrate off of said support surface; and

removing said substrate from above said support surface.

8. The method of claim 7, wherein said susceptor includes a plurality of outer gas passages positioned just radially outward of a peripheral edge of said substrate when said substrate is centered upon said support surface of said susceptor, said outer gas passages being substantially vertical so that upward gas flow through said outer gas passages flows substantially vertically upward above said susceptor, said method further comprising providing gas flow through said outer gas passages to counteract sideward sliding of said substrate after said liftoff gas flow is provided.

9. The method of claim 1, wherein said susceptor is configured with a pocket to support a 300 mm semiconductor substrate.

10. The method of claim 1, wherein said susceptor is configured with a pocket to support a 200 mm semiconductor wafer.

11. The method of claim 1, wherein said susceptor is configured with a pocket to support a 150 mm semiconductor wafer.

12. The method of claim 1, wherein said rate of descent of said substrate is no greater than one third of the rate at which said substrate would descend under gravity alone.

13. The method of claim 1, wherein said rate of descent of said substrate is no greater than one quarter of the rate at which said substrate would descend under gravity alone.

14. The method of claim 1, wherein at the moment that said substrate comes into contact with said support surface, the temperature difference between said substrate and said support surface is no greater than 100°

C.

15. The method of claim 1, wherein said contact between said substrate and said support surface produces a curl of said substrate of no greater than 0.200 inches.

16. The method of claim 1, wherein said contact between said substrate and said support surface produces a curl of said substrate of no greater than 0.100 inches.

17. The method of claim 1, wherein said contact between said substrate and said support surface produces a curl of said substrate of no greater than 0.050 inches.

18. The method of claim 1, wherein said susceptor has a temperature within the range of 200-1000°

C., and said substrate has a temperature within the range of 0-100°

C. at the time of said releasing of said substrate.

19. A method of loading a substrate onto a susceptor, comprising:

releasing a substrate above a support surface of a susceptor, such that said substrate is permitted to descend toward said support surface by gravitational force;

providing a cushioning flow of gas that imparts an upwardly directed force onto said substrate, the flow rate of said cushioning gas flow being sufficient to slow the rate of descent of said substrate to a rate no greater than one half of the rate at which said substrate would descend under gravity alone; and

permitting said substrate to come into contact with said support surface.

20. A method of loading a wafer onto a susceptor, comprising:

releasing a wafer above a susceptor, said wafer having a peripheral edge; and

providing a plurality of substantially vertical upwardly directed gas jets radially exterior of said peripheral edge of said wafer, said jets substantially inhibiting sideward motion of said wafer as said wafer descends toward said susceptor.