Heat transfer system for improved semiconductor processing uniformity

• US 20060075969A1
• Filed: 10/13/2004
• Published: 04/13/2006
• Est. Priority Date: 10/13/2004
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Fischer, Andreas
• Granted Patent: US 7,244,311 B2
• Time in Patent Office: Days
• US Class Current: 118/725
• CPC Class Codes: C03C 15/00 Surface treatment of glass, not in the form of fibres or filaments, by etching etching or surface-brightening compositions, in general C09K13/00
• CPC Class Codes: C03C 17/23 Oxides C03C17/02 takes precedence
• CPC Class Codes: C03C 2217/213 SiO2
• CPC Class Codes: C03C 2218/33 by etching
• CPC Class Codes: H01J 2237/2001 Maintaining constant desired temperature
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/67103 mainly by conduction
• CPC Class Codes: H01L 21/67109 mainly by convection
• CPC Class Codes: H01L 21/68742 characterised by a lifting arrangement, e.g. lift pins
• CPC Class Codes: H01L 21/6875 characterised by a plurality of individual support members, e.g. support posts or protrusions
• CPC Class Codes: H01L 21/68778 characterised by supporting substrates others than wafers, e.g. chips

Abstract

A plasma processing system and methods for processing a substrate using a heat transfer system are provided. The heat transfer system, which is capable of producing a high degree of processing uniformity across the surface of a substrate, comprises a uniformity pedestal supported on and in good thermal contact with a heat transfer member. The uniformity pedestal includes a pin array which provides a conformal substrate support surface (i.e., contact surface) that can conform to the profile of a backside surface of a substrate during processing. To uniformly cool a substrate, a large thermal gradient can be established between the uniformity pedestal and the heat transfer member during the processing of a substrate.

Claims

1. A heat transfer system adapted to support a substrate for semiconductor processing of an upper surface thereof comprising:

a pin base overlying and in thermal contact with a heat transfer member, said pin base having an upper wall, a lower wall and a side wall extending between the upper and lower walls and defining a cavity therebetween, wherein said upper wall comprises an array of bores;

an array of substrate support pins each of which is slideably positioned in a respective one of the bores, each substrate support pin in thermal contact with the pin base and comprising a contact tip at its upper distal end; and

a pressurized gas source in fluid communication with said cavity and adapted to supply pressurized gas to said cavity in an amount sufficient to move each support pin in an upward direction.

2. The heat transfer system of claim 1, wherein the pin array comprises a dense array of support pins.

3. The heat transfer system of claim 1, wherein the support pins are located no more than about 5 mm apart and/or the diameter of the support pins is between about 0.5 mm and 3 mm.

4. The heat transfer system of claim 1, wherein each of the support pins comprises a cylindrical pin body adapted to slideably move within a respective one of said bores, the cylindrical pin body having a substantially constant outer diameter, each of the bores having a substantially constant inner diameter, wherein the outer diameter of the cylindrical pin body is between about 0.1 and 5% less than the inner diameter of the bore in which the cylindrical pin body is located.

5. The heat transfer system of claim 1, wherein the support pins comprise a metal or a semiconductor and/or the pin base comprises a metal or a semiconductor.

6. The heat transfer system of claim 1, wherein the support pins and/or the upper surface of the pin base are coated with an electrically conductive and/or sputter resistant metal or semiconductor.

7. The heat transfer system of claim 1, wherein the support pins and the pin base are adapted to transfer thermal energy from the substrate to the heat transfer member when the substrate is supported on the support pins.

8. The heat transfer system of claim 1, wherein the pin base is bonded to the heat transfer member via solder, braze or an adhesive.

9. The heat transfer system of claim 1, further comprising at least one temperature sensor adapted to measure a temperature at a backside surface of the substrate.

10. The heat transfer system of claim 1, wherein the support pins further comprise at least one stop adapted to restrict the upward or downward movement of the support pins.

12. The heat transfer system of claim 1, wherein each contact tip comprises a contact surface having an average surface roughness of less than about 0.3 microns.

13. The heat transfer system of claim 1, wherein each contact tip is substantially flat or substantially hemispherical.

14. The heat transfer system of claim 1, wherein each of the support pins is adapted to be displaced downward by contact with a backside surface of the substrate and each of the support pins is adapted to be displaced upward by a positive gas pressure in the cavity.

15. The heat transfer system of claim 1, wherein the total vertical range of motion of each support pin is less than about 5 mm.

16. The heat transfer system of claim 1, wherein the pin array comprises at least 1000 support pins.

17. The heat transfer system of claim 1, wherein the heat transfer member comprises flow channels in fluid communication with a thermal fluid source adapted to provide a thermal fluid to the flow channels, said thermal fluid selected from the group consisting of water, liquid helium, liquid nitrogen, ethylene glycol, propylene glycol, and mixtures thereof.

18. The heat transfer system of claim 1, further comprising a plurality of thermoelectric elements on top of the heat transfer member.

19. The heat transfer system of claim 18, wherein the thermoelectric elements are arranged in concentric circles.

20. The heat transfer system of claim 1, further comprising a gas supply inlet in said pin base for flowing a pressurized gas into said cavity and an optional gas outlet for releasing a pressured gas from said cavity, wherein the pressurized gas is selected from the group consisting of helium, nitrogen and argon.

21. The heat transfer system of claim 1, further comprising an RF electrode configured for generating a plasma adjacent the upper surface of the substrate, wherein a bottom surface of the pin base is bonded to an upper surface of the RF electrode and a bottom surface of the RF electrode is bonded to an upper surface of the heat transfer member, wherein the bonding comprises solder, braze or an adhesive.

22. The heat transfer system of claim 21, further comprising an edge ring disposed above the RF electrode, the edge ring being configured for shielding the RF electrode and the pin base from a plasma, the edge ring having a first portion configured to be disposed between the RF electrode and the substrate when the substrate is supported by the heat transfer system;

and an impedance matching layer disposed between the RF electrode and the edge ring, the impedance matching layer being bonded to the RF electrode and/or to the edge ring, the impedance matching layer configured to control an impedance between the RF electrode and a plasma, said impedance between arranged to affect the electric field to improve processing uniformity across the upper surface of the substrate.

23. The heat transfer system of claim 21, wherein the substrate is a semiconductor wafer and the electrode has a diameter less than, greater than or equal to the diameter of the wafer, but not more than about 2 mm less than or more than about 2 mm greater than the diameter of the wafer.

24. A method of processing a substrate in a process chamber comprising the heat transfer system of claim 21, said method comprising steps of:

supporting the substrate on the support pins;

contacting a majority of the contact tips with a backside surface of the substrate by controlling the gas pressure in the cavity; and

processing the substrate.

25. The method of claim 24, wherein the process chamber is a plasma etch chamber and the processing comprises generating a plasma adjacent the upper surface of the substrate and etching an exposed layer on the upper surface of the substrate with the plasma.

26. The method of claim 24, wherein the processing comprises forming a layer on the upper surface of the substrate.

27. The method of claim 24, wherein the gas pressure in the cavity is maintained at a level effective to maintain at least 95% of the contact tips in thermal contact with a backside surface of the substrate during processing.

28. The method of claim 24, comprising cooling the heat transfer member to a temperature of less than about 100K during processing by circulating a thermal fluid in the heat transfer member

29. The method of claim 24, comprising cooling the substrate to a temperature of less than about 450K during processing by circulating a thermal fluid in the heat transfer member and/or by supplying currents to a plurality of thermoelectric modules to control the temperature of the substrate support pins.

30. The method of claim 24, comprising maintaining a temperature gradient of at least about 200K or at least about 300K between the heat transfer member and the substrate.

31. The method of claim 24, wherein the step of processing comprises chemical vapor deposition, plasma vapor deposition, physical vapor deposition, sputtering, ion implantation, plasma etching or resist stripping.

32. The method of claim 24, comprising supporting and processing the substrate without clamping the substrate.

33. The method of claim 24, wherein the process chamber comprises a dual frequency capacitively coupled plasma reactor including an upper showerhead electrode and a bottom electrode, RF energy being supplied at two different frequencies to either the bottom electrode or at different first and second frequencies to the showerhead electrode and bottom electrode.

34. A plasma processing system for processing a surface of a substrate, comprising:

a vacuum processing chamber adapted to ignite and sustain a plasma for processing; and

the heat transfer system of claim 1 disposed within the processing chamber.

36. The heat transfer system of claim 1, wherein said substrate support pins are movable to different heights relative to each other.

11. (canceled)

35. A heat transfer system adapted to support a substrate for semiconductor processing of an upper surface thereof comprising:

a pin base overlying and in thermal contact with a heat transfer member, said pin base having an upper wall, a lower wall and a side wall extending between the upper and lower walls and defining a cavity therebetween, wherein said upper wall comprises an array of bores;

an array of substrate support pins each of which is slideably positioned in a respective one of the bores, each substrate support pin in thermal contact with the pin base and comprising a contact tip at its upper distal end; and

a pressurized gas source in fluid communication with said cavity and adapted to supply pressurized gas to said cavity in an amount sufficient to move each support pin in an upward direction, wherein the heat transfer member comprises flow channels in fluid communication with a thermal fluid source adapted to provide a thermal fluid to the flow channels.