Temperature control modules for showerhead electrode assemblies for plasma processing apparatuses

• US 20090081878A1
• Filed: 09/24/2008
• Published: 03/26/2009
• Est. Priority Date: 09/25/2007
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Dhindsa, Rajinder
• Granted Patent: US 8,313,610 B2
• Time in Patent Office: Days
• US Class Current: 438/729
• CPC Class Codes: H01J 37/32091 the radio frequency energy being capacitively coupled to the plasma
• CPC Class Codes: H01J 37/32724 Temperature
• CPC Class Codes: H05B 3/03 Electrodes

Abstract

A temperature control module for a showerhead electrode assembly for a semiconductor material plasma processing chamber includes a heater plate adapted to be secured to a top surface of a top electrode of the showerhead electrode assembly, and which supplies heat to the top electrode to control the temperature of the top electrode; a cooling plate adapted to be secured to and thermally isolated from a surface of a top plate of the showerhead electrode assembly, and to cool the heater plate and control heat conduction between the top electrode and heater plate; and at least one thermal choke adapted to control heat conduction between the heater plate and cooling plate.

Claims

1. A temperature control module for a showerhead electrode assembly for a semiconductor material plasma processing chamber, the temperature control module comprising:

a heater plate having a bottom surface adapted to be secured to a top surface of a top electrode of the showerhead electrode assembly, the top electrode having a plasma-exposed bottom surface, the heater plate including at least one heater adapted to supply heat to the top electrode to control the temperature of the top electrode;

a cooling plate having a top surface adapted to be secured to and thermally isolated from a bottom surface of a top plate forming a top wall of the plasma processing chamber, the cooling plate adapted to control the temperature of the heater plate and control heat conduction between the heater plate and the top electrode; and

at least one electrically and thermally conductive thermal choke located between, and in contact with, a top surface of the heater plate and a bottom surface of the cooling plate, the at least one thermal choke adapted to control heat conduction between the heater plate to the cooling plate.

2. The temperature control module of claim 1, wherein:

the heater plate comprises a piece of a metal having heating elements embedded therein, and gas distribution passages adapted to be in fluid communication with a gas supply and with gas distribution plenums in a backing member of the showerhead electrode assembly, the heating elements adapted to be connected to at least one power supply operable to supply power to the heating elements; and

the cooling plate comprises a piece of a metal having liquid channels formed therein, the liquid channels are adapted to be in fluid communication with at least one source of a temperature-controlled liquid which is supplied to the liquid channels to control the temperature of the cooling plate.

3. The temperature control module of claim 1, wherein:

the cooling plate comprises a plurality of radially-spaced, concentrically-arranged first grooves in the bottom surface, each of the first grooves has a first height; and

the at least one thermal choke comprises a plurality of thermal chokes, each thermal choke is a ring disposed in a respective first groove in the cooling plate, the rings are concentrically arranged with respect to each other, each ring has a second height which is greater than the first height of the respective first groove in which the thermal choke is disposed such that the rings support the cooling plate on the heater plate, a gap is defined between the bottom surface of the cooling plate and the top surface of the heater plate, and heat is conducted between the heater plate and cooling plate through the rings.

4. The temperature control module of claim 3, wherein the plurality of rings comprises at least one first ring and a second ring, each first ring includes a plurality of through openings, and the second ring is non-porous and surrounds the at least one first ring and forms an outer surface of the temperature control module.

5. The temperature control module of claim 3, wherein the plurality of the rings comprises at least one first ring and a second ring, each first ring is a sintered porous metallic body, and the second ring is non-porous and surrounds the at least one first ring and forms an outer surface of the temperature control module.

6. The temperature control module of claim 1, wherein:

the bottom surface of the cooling plate is planar;

the top surface of the heater plate is planar; and

the at least one thermal choke comprises a plate composed of a flexible, thermally and electrically conductive material, the thermal choke plate has opposed planar surfaces secured to the bottom surface of the cooling plate and the top surface of the heater plate, respectively, and the thermal choke plate has a porous structure that provides thermal resistance to heat conduction between the heater plate and the cooling plate.

7. The temperature control module of claim 1, wherein:

the cooling plate, at least one thermal choke and heater plate comprise aligned openings; and

a threaded fastener is received in each of the aligned openings to secure the cooling plate, at least one thermal choke and heater plate to each other, each threaded fastener includes a washer set adapted to resist loosening of the fastener due to thermal cycling of the heater plate.

8. A showerhead electrode assembly for a plasma processing chamber, comprising:

a top plate forming a top wall of the plasma processing chamber;

a top electrode including a top surface and a plasma-exposed bottom surface; and

a temperature control module comprising;

a heater plate having a bottom surface secured to the top surface of the top electrode, the heater plate including at least one heater adapted to supply heat to the top electrode to control the temperature of the top electrode;

a cooling plate having a top surface secured to and thermally isolated from a bottom surface of a top plate, the cooling plate adapted to control the temperature of the heater plate and control heat conduction between the heater plate and the top electrode; and

at least one electrically and thermal conductive thermal choke located between, and in thermal contact with, a top surface of the heater plate and a bottom surface of the cooling plate, the at least one thermal choke adapted to control heat conduction between the heater plate and the cooling plate.

9. The showerhead electrode assembly of claim 8, wherein:

the heater plate comprises radial gas distribution passages in fluid communication with a gas supply; and

the top electrode comprises;

an inner electrode member including a plurality of first gas passages;

an outer electrode member which is secured to and surrounds the inner electrode member, the outer electrode member includes a plurality of second gas passages;

a backing plate secured to a top surface of the inner electrode member, the backing plate includes a plurality of radially-spaced plenums in fluid communication with radial gas distribution passages, and third gas passages in fluid communication with respective first gas passages; and

a backing ring which surrounds the backing plate, the backing ring includes a plurality of fourth gas passages in fluid communication with the radial gas distribution passages.

10. The showerhead electrode assembly of claim 9, wherein:

the inner electrode member includes surfaces bonded to the backing plate, outer electrode member and backing ring;

the outer electrode member includes surfaces bonded to the inner electrode member and backing ring;

the backing plate includes surfaces bonded to the inner electrode member and backing ring; and

the backing ring includes surfaces bonded to the backing plate, outer electrode member and inner electrode member.

11. The showerhead electrode assembly of claim 9, wherein the outer electrode member comprises a step extending outwardly at an obtuse angle from a plasma-exposed bottom surface of the inner electrode member.

12. The showerhead electrode assembly of claim 9, wherein the inner electrode member comprises a step extending outwardly at an obtuse angle from a plasma-exposed bottom surface of the inner electrode member.

13. The showerhead electrode assembly of claim 9, wherein:

the heater plate comprises a piece of a metal having heating elements embedded therein, the heating elements are connected to at least one power supply operable to supply power to the heating elements; and

the cooling plate comprises a piece of a metal having liquid channels formed therein, the liquid channels are in fluid communication with at least one source of a temperature-controlled liquid which is supplied to the liquid channels to control the temperature of the cooling plate;

or

the heater plate comprises an inner heater plate having at least one inner heating element and an outer heater plate having at least one outer heating element, the inner and outer heating elements connected to separate power supplies operable to supply power to the inner and outer heating elements and control temperature of the inner and outer electrode members.

14. The showerhead electrode assembly of claim 9, wherein:

the cooling plate comprises a bottom surface and a plurality of radially-spaced, concentrically-arranged first grooves in the bottom surface, each of the first grooves has a first height; and

the at least one thermal choke comprises a plurality of thermal chokes, each thermal choke is a ring disposed in a respective first groove in the cooling plate, each of the rings has a second height which is greater than the first height of the respective first groove in which the thermal choke is disposed such that the rings support the cooling plate on the heater plate, a gap is defined between the bottom surface of the cooling plate and the top surface of the heater plate, and the top surface of the heater plate and heat is conducted between the heater plate and cooling plate through the rings.

15. The showerhead electrode assembly of claim 14, wherein the plurality of rings comprises at least one first ring and a second ring, each first ring has a plurality of through openings or is a sintered porous metallic body, and the second ring is non-porous and surrounds the at least one first ring and forms an outer surface of the temperature control module.

16. The showerhead electrode assembly of claim 8, wherein:

the bottom surface of the cooling plate is planar;

the top surface of the heater plate is planar; and

the at least one thermal choke comprises a plate composed of a flexible, thermally and electrically conductive material, the plate has opposed planar surfaces secured to the bottom surface of the cooling plate and the top surface of the heater plate, respectively, and the thermal choke plate has a porous structure adapted to provide thermal resistance to heat conduction from the heater plate to the cooling plate.

17. The showerhead electrode assembly of claim 8, wherein:

the cooling plate, at least one thermal choke and heater plate comprise aligned openings; and

a threaded fastener is received in each of the aligned openings to secure the cooling plate, at least one thermal choke and heater plate to each other, each threaded fastener includes a washer set adapted to resist loosening of the fastener due to thermal cycling of the heater plate.

18. The showerhead electrode assembly of claim 8, wherein the bottom surface of the top plate comprises radially-spaced, concentrically-arranged second grooves, adjacent ones of the second grooves are separated by annular projections on the bottom surface of the top plate and the top plate is in contact with the top surface of the cooling plate at the annular projections.

19. A method of controlling the temperature of a top electrode of a showerhead electrode assembly in a plasma processing chamber containing a substrate support having a bottom electrode, the showerhead electrode assembly comprising a top plate forming a top wall of the plasma processing chamber, and a temperature control module located between and secured to the top plate and the top electrode, the method comprising:

generating plasma in the plasma processing chamber in a gap between the top electrode and the substrate support;

applying power from at least one power supply to at least one heater of a heater plate of the temperature control module to heat the top electrode;

supplying a temperature-controlled liquid from at least one liquid source to liquid channels of a cooling plate of the temperature control module to control the temperature of the cooling plate; and

controlling heat conduction (i) between the cooling plate and the top plate by thermally isolating the cooling plate from the top plate, (ii) between the cooling plate and the heater plate with at least one thermal choke located between the cooling plate and heater plate, and (iii) between the heater plate and the top electrode by controlling the temperature of the heater plate, to thereby maintain the top electrode at a desired temperature.

20. The method of claim 19, wherein:

the temperature control module maintains the top electrode at a temperature which is within about ±

5 of a set point of about 40°

C. to about 200°

C. when the plasma is being generated and when the plasma is not being generated; and

the temperature control module maintains a maximum radial center-to-edge temperature gradient of the top electrode of about ±

30°

C.