Gas distribution showerhead for inductively coupled plasma etch reactor

• US 9,099,398 B2
• Filed: 09/19/2013
• Issued: 08/04/2015
• Est. Priority Date: 05/31/2011
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Kang, Michael, Paterson, Alex, Kenworthy, Ian J.
• Primary Examiner(s): Zervigon, Rudy
• Application Number:
  US14/031,840
• Publication Number:
  US 20140065827A1
• Time in Patent Office: 684 Days
• Field of Search: 118/723.I, 156/345.48, 15634533-34534
• US Class Current: 1/1
• CPC Class Codes: B05B 1/185 characterised by their outlet element; Mounting arrangements therefor
• CPC Class Codes: B05D 1/62 Plasma-deposition of organic layers plasma deposition in general C23C14/00, C23C16/00
• CPC Class Codes: C23C 16/455 characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
• CPC Class Codes: C23C 16/45561 Gas plumbing upstream of the reaction chamber
• CPC Class Codes: C23C 16/505 using radio frequency discharges
• CPC Class Codes: C23C 16/507 using external electrodes, e.g. in tunnel type reactors
• CPC Class Codes: H01J 2237/3341 Reactive etching
• CPC Class Codes: H01J 37/3211 Antennas, e.g. particular shapes of coils
• CPC Class Codes: H01J 37/3244 Gas supply means
• CPC Class Codes: H01L 21/30604 Chemical etching
• CPC Class Codes: H01L 21/30655 comprising alternated and repeated etching and passivation steps, e.g. Bosch process
• CPC Class Codes: H01L 21/67069 for drying etching

Abstract

A two piece ceramic showerhead includes upper and lower plates which deliver process gas to an inductively coupled plasma processing chamber. The upper plate overlies the lower plate and includes radially extending gas passages which extend inwardly from an outer periphery of the upper plate, axially extending gas passages in fluid communication with the radially extending gas passages and an annular recess forming a plenum between the upper and lower plates. The lower plate includes axially extending gas holes in fluid communication with the plenum. The two piece ceramic showerhead forms a dielectric window of the chamber through which radiofrequency energy generated by an antenna is coupled into the chamber. The gas delivery system is operable to supply an etching gas and a deposition gas into the processing chamber such that the etching gas in the plenum can be replaced with the deposition gas.

Claims

1. A ceramic showerhead of uniform thickness configured to form a vacuum wall at the top of an inductively coupled plasma processing apparatus wherein semiconductor substrates supported on a substrate support are subjected to plasma etching, comprising:

a lower plate of ceramic material having a planar lower surface, axially extending gas holes having diameters of less than 0.06 inch and aspect ratios of at least 2 located in an annular zone on an outer portion and extending between upper and lower surfaces, a vacuum sealing surface located on the outer portion at an outer periphery of the lower surface, and inner and outer vacuum sealing surfaces on the upper surface defining the annular zone in which the axially extending gas holes are located;

an upper plate of ceramic material having planar upper and lower surfaces, the upper plate overlying the lower plate such that a plenum is located between opposed surfaces of the upper and lower plates and the gas holes are in fluid communication with the plenum.

2. The ceramic showerhead of claim 1, wherein the lower plate includes at least two rows of axially extending gas holes, each of the rows having 20 to 50 of the axially extending gas holes.

3. The ceramic showerhead of claim 2, wherein the lower plate has a diameter of about 20 inches, a thickness of about 1.5 inches at a central portion and a thickness of about 0.8 inch at the outer portion, the two rows of gas holes including an inner row of 32 gas holes having diameters of 0.04 inch and located about 5 inches from a center of the lower plate and an outer row of 32 gas holes having diameters of about 0.04 inch and located about 6.5 inches from the center of the lower plate, and the sealing surface located on a step in the lower surface, the step having a depth of about 0.4 inch and a width of about 1.2 inches.

4. The ceramic showerhead of claim 1, wherein the upper plate includes at least 8 radially extending gas passages having diameters of about 0.125 inch and located 45°

apart, at least 8 axially extending gas passages having diameters of about 0.125 inch and located about 5.75 inches from the center of the upper plate, an annular recess defining an annular plenum having a width of about 1.7 inches and depth of about 0.015 to 0.02 inch, and inner and outer O-ring grooves surrounding the annular plenum, the annular plenum providing fluid communication between the gas passages in the upper plate and the gas holes in the lower plate.

5. The ceramic showerhead of claim 4, wherein the upper plate further comprises 8 pairs of axially extending mounting holes having diameters of about 0.4 inch located in the upper surface of the upper plate, 8 pairs of radially extending mounting holes having diameters of about 0.35 inch located in flat mounting surfaces on outer periphery of the upper plate, the centers of each pair of the mounting holes located about 1 inch apart.

6. The ceramic showerhead of claim 1, wherein the upper and lower plates are made of high purity alumina and the lower surface of the lower plate includes a coating of high purity yttria covering all of the lower surface except the sealing surface.

7. A processing chamber in which a semiconductor substrate is processed;

a substrate support on which the semiconductor is supported during processing thereof;

the ceramic showerhead of claim 1 forming a dielectric window of the chamber;

an antenna operable to inductively couple RF energy through the dielectric window and into the chamber to energize process gas into plasma in a chamber gap between the substrate support and the dielectric window; and

a gas delivery system operable to alternately supply process gas comprising an etching gas and a deposition gas to the radially extending gas passages in the ceramic showerhead such that the etching gas in the annular plenum is replaced with the deposition gas within 200 milliseconds or the deposition gas in the annular plenum is replaced with the etching gas within 200 milliseconds, the plasma processing apparatus being operable to etch openings in silicon material on the semiconductor substrate at a rate of at least 10 μ

m/minute.

8. The plasma processing apparatus of claim 7, wherein the etching gas is selected from SF₆, NF₃ and CF₄ and the deposition gas is selected from C₄F₈, C₄F₆, CH₂F₂, CHF₃, CH₃F.

9. A method of processing a semiconductor substrate using the plasma processing apparatus of claim 7, the method comprising:

(a) supporting the semiconductor substrate on the substrate support in the processing chamber;

(b) interrupting flow of the deposition gas and supplying the etching gas to the annular plenum such that the etching gas flows through the gas holes in the ceramic showerhead into the chamber gap;

(c) energizing the etching gas in the chamber gap into a first plasma and plasma etching openings in the semiconductor substrate with the first plasma;

(d) interrupting flow of the etching gas and supplying the deposition gas to the annular plenum such that the deposition gas flows through the gas holes in the ceramic showerhead into the chamber gap;

(e) energizing the deposition gas in the chamber gap into a second plasma and depositing polymer in the openings with the second plasma;

(f) repeating steps (b)-(e) with a total cycle time of no greater than 1.8 seconds.

10. The method of claim 9, wherein the semiconductor substrate is a silicon wafer, the etching gas replaces the deposition gas in the chamber gap within a period of about 500 milliseconds in step (b), and the deposition gas replaces the etching gas in the chamber gap within a period of about 500 milliseconds in step (d).

11. The method of claim 9, wherein pressure in the plenum is at least 1 Torr during steps (b)-(e).

12. The method of claim 9, wherein a total time of supplying the etching gas is 1.3 seconds or less and a total time of supplying the deposition gas is 0.7 seconds or less.

13. The method of claim 9, wherein pressure in the chamber gap during supply of the etching gas is at least 150 mTorr and pressure in the chamber gap during supply of the deposition gas is below 150 mTorr.

14. The method of claim 9, wherein the etching gas is supplied to the plenum at a flow rate of at least 500 sccm and the deposition gas is supplied to the plenum at a flow rate of below 500 sccm.

15. The method of claim 9, wherein the chamber gap between the semiconductor substrate and the showerhead plate is at least 4 inches.