Electrostatic chuck having textured contact surface
An electrostatic chuck has an electrode embedded in a dielectric which is mounted on a pedestal. The dielectric has a contact surface with an average surface roughness of less than about 0.5 μm, a surface peak waviness of less than about 0.12 μm, and a surface peak waviness material ratio of greater than about 20%. The surface texture can be formed by lapping the dielectric surface with a slurry of abrasive particles.
1. An electrostatic chuck for holding a substrate in a process chamber, the electrostatic chuck comprising:
(a) at least one electrode capable of receiving an electrical charge to generate an electrostatic force;
(b) a dielectric enclosing the electrode, the dielectric having a contact surface that is characterized by:
(i) an average surface roughness of less than about 0.6 μm,
(ii) a surface peak waviness across the entire contact surface of less than about 0.12 μm, and
(iii) a surface waviness material ratio of greater than about 20%, the surface waviness material ratio being measured at a reference depth level; and
(c) a pedestal bonded to the dielectric.
2. A chuck according to claim 1 wherein the surface peak waviness is the mean amplitude of the measured surface profile after the small wavelength roughness variations have been filtered out at a cutoff length.
3. A chuck according to claim 2 wherein the cutoff length for the surface peak waviness is 0.8 mm.
4. A chuck according to claim 1 wherein the surface waviness material ratio is the waviness of a length L of the contact surface expressed as a percentage of the evaluation length E L at a depth (d) below a reference depth level (c) which cuts 0.2 microns below the contact surface.
5. A chuck according to claim 1 wherein the dielectric comprises a contact surface such that when a batch of 1000 substrates are processed on the electrostatic chuck in a process chamber having a plasma environment, the change in temperature from the first processed substrate to the 1000 th processed substrate is less than about 10° C.
6. A chuck according to claim 5 wherein the change in heat transfer gas leak rate from the first processed substrate to the 1000 th processed substrate is less than 2 sccm.
7. A chuck according to claim 1 wherein the dielectric comprises aluminum nitride or aluminum oxide.
8. A chuck according to claim 1 wherein the contact surface comprises a plurality of mesas, the mesas including at least one seal band.
9. A chuck according to claim 1 wherein the pedestal comprises fluid channels.
10. An electrostatic chuck for holding a substrate in a process chamber, the electrostatic chuck comprising:
(a) at least one electrode capable of receiving an electrical charge to generate an electrostatic force;
(b) a dielectric enclosing the electrode, the dielectric having a contact surface defined by the tops of a plurality of mesas, and wherein the contact surface is characterized by:
(i) an average surface roughness of less than about 0.6 μm,
(ii) a surface peak waviness across the entire contact surface of less than about 0.12 μm, the surface peak waviness being the mean amplitude of the measured surface profile after the small wavelength roughness variations are filtered out at a cutoff length of 0.8 mm; and
(iii) a surface waviness material ratio of greater than about 20% the surface waviness material ratio being the waviness of a length L of the contact surface expressed as a percentage of the evaluation length E L at a depth (d) below a reference depth level (c) which cuts 0.2 microns below the contact surface; and
(c) a pedestal bonded to the dielectric with a bond layer, the pedestal comprising fluid channels.
11. A chuck according to claim 10 wherein the dielectric comprises a contact surface such that when a batch of 1000 substrates are processed on the electrostatic chuck in a process chamber having a plasma environment, the change in temperature from the first processed substrate to the 1000 th processed substrate is less than about 10° C.
12. A chuck according to claim 11 wherein the change in heat transfer gas leak rate from the first processed substrate to the 1000 th processed substrate is less than 2 sccm.
13. A chuck according to claim 10 wherein the dielectric comprises aluminum nitride or aluminum oxide.
14. A chuck according to claim 10 wherein the bond layer comprises an adhesive sheet.
15. A method of fabricating an electrostatic chuck comprising a dielectric with an embedded electrode, the method comprising:
(a) forming a green ceramic preform comprising a least one embedded electrode;
(b) sintering the green ceramic preform to form a sintered electrostatic chuck having a contact surface;
(c) lapping the contact surface to provide a surface roughness of less than about 0.6 μm, a surface peak waviness of less than about 0.12 μm across the entire contact surface, and a surface waviness material ratio of greater than about 20%, the surface waviness material ratio being measured at a reference depth level.
16. A method according to claim 15 wherein (c) comprises lapping the contact surface with a slurry comprising abrasive particles.
17. A method according to claim 16 comprising lapping the contact surface with a slurry comprising abrasive particles of silicon carbide particles.
18. A method according to claim 15 comprising bonding a pedestal to the sintered electrostatic chuck.
19. A method according to claim 18 comprising forming a pedestal having fluid channels.
20. An electrostatic chuck fabricated by the process of claim 15 .