Plasma Reactor Having Radial Struts for Substrate Support
A plasma reactor for processing a workpiece includes a reactor chamber having a ceiling and a sidewall and a workpiece support facing the ceiling and defining a processing region, and a pair of concentric independently excited RF coil antennas overlying the ceiling and a side RF coil concentric with the side wall and facing the side wall below the ceiling, and being excited independently.
This application is a continuation of U.S. application Ser. No. 13/666,245, filed Nov. 1, 2012, which claims the benefit of U.S. Provisional Application Ser. No. 61/673,937, filed Jul. 20, 2012, the disclosures of which are incorporation by reference.
BACKGROUND FieldEmbodiments of the present invention are generally concerned with a plasma processing reactor chamber for processing workpieces, in which plasma is generated by inductive coupling of RF power to process gases inside the chamber.
Description of the Related ArtElectronic devices such as integrated circuits, flat panel displays and the like, are fabricated by a series of processes, in which thin film layers are deposited on substrates and etched into desired patterns. The process steps may include plasma-enhanced reactive ion etching (RIE), plasma-enhanced chemical vapor deposition (CVD), plasma-enhanced physical vapor deposition (PVD).
Uniform distribution of etch rate or deposition rate across the entire surface of the substrate is essential for successful fabrication. Such uniformity is becoming more difficult to achieve, as substrate size is increasing and device geometry is shrinking. In particular, inductively coupled plasma sources can have two concentrically arranged coil antennas over the chamber ceiling, so that uniformity of etch rate distribution can be optimized by adjusting the different RF power levels delivered to the different coil antennas. As workpiece diameter and chamber diameter increase, we have found this approach is not adequate, as the larger size increases the difficultly of attaining the requisite process uniformity. Various sources of process non-uniformity, such as chamber design asymmetries, temperature distribution non-uniformities and gas distribution control become more important.
SUMMARYA plasma reactor includes an axially symmetrical side wall, a ceiling overlying the side wall and a workpiece support, the side wall, the ceiling and the workpiece support defining a processing region. An inner coil antenna is disposed on an external side of the ceiling and overlies a first radial zone of the processing region. A middle coil antenna surrounds the inner coil antenna and overlies a second radial zone of the processing region surrounding the first radial zone. For precise control of plasma density near the edge of the processing region, an outer coil antenna is provided below a plane of the ceiling and surrounding the side wall. Plural RF power sources are coupled to respective ones of the inner coil antenna, middle coil antenna and outer coil antenna. A controller governs respective power levels of the plural RF power sources.
In an embodiment, the side wall, the inner coil antenna, the middle coil antenna and the outer coil antenna are coaxial.
The plasma reactor in one embodiment may further include an exhaust chamber assembly, the exhaust chamber assembly including: (a) an exhaust chamber wall defining an evacuation region at a side of the workpiece support opposite the processing region, the exhaust chamber assembly having an exhaust pump port symmetrically located relative to the axis of symmetry, and (b) plural axial exhaust passages between the processing region and the evacuation region, and symmetrically distributed with respect to the axis of symmetry.
A lift mechanism may be coupled to the workpiece support.
In an embodiment, the ceiling includes a first dielectric window facing the inner and middle coil antennas, and the side wall includes a cylindrical dielectric window facing the outer coil antenna.
In an embodiment, the ceiling includes an annular member supported on the side wall and having a central opening, a peripheral portion of the disk-shaped dielectric window resting on an inner edge of the central opening.
A grounded conductive shield may be disposed between the inner and middle coil antennas and surrounding the inner coil antenna. The grounded conductive shield may include a cylindrical portion coaxial with the side wall.
In one embodiment, each one of the inner, middle or outer coil antennas comprises plural conductor segments wound in a helical shape about an axis of the side wall, each of the conductor segments having a first arc length less than a full circle, successive ones of the conductor segments being offset from one another along an axial direction and being offset from one another along a circumferential direction by a second arc length not exceeding the first arc length. The plural conductor segments are coupled in parallel to one of the RF power sources. In an embodiment, in least one of the inner and middle coil antennas, the first arc length is 180 degrees and the second arc length is 90 degrees, and in the outer coil antenna the first and second arc lengths are 180 degrees.
In accordance with one embodiment, the plasma reactor further includes plural current distributors coupled between respective ones of the inner, middle and outer coil antennas and respective ones of the plural RF power sources, wherein each one of the current distributors comprises a conductive surface coaxial with the axis of symmetry, the conductive surface having (a) a receiving portion coupled to the respective one of the plural RF power sources and (b) a first circular edge coupled to the respective one of the plural coil antennas. Each one of the concentric coil antennas includes plural conductors helically wound about the axis of symmetry, each of the plural conductors having a supply end and a ground end, the first circular edge of each of the current distributors being connected to the supply ends of the respective coil antenna at spaced-apart locations along the first circular edge. The spaced-apart locations may be uniformly distributed.
Respective RF feed assemblies may be coupled between respective ones of the RF power sources and the receiving portions of respective ones of the current distributors. In an embodiment, each of the RF feed assemblies coupled to the middle and outer coil antennas includes: (a) an upper portion comprising an upper RF feed rod extending axially from a respective one of the RF power sources and being located away from the axis of symmetry, (b) plural radial rods extending radially from a common center and being electrically connected to the upper RF feed rod, and (c) plural axial rods extending axially between respective ones of the plural radial rods and the respective current distributor, the axial rods being symmetrically located with respect to the axis of the side wall.
In one embodiment, a conductive grounded plate lies in a radially extending plane intersecting the plural axial rods, and having passages therethrough maintaining separation between the grounded plate and the plural axial rods.
In one embodiment, the RF feed rod assembly coupled to the inner coil antenna is a single axial RF feed rod coaxial with the axis of symmetry, and the receiving portion of the current distributor coupled to the inner coil antenna is an apex coaxial with the wall, the single axial RF feed rod being connected to the apex.
The plasma reactor may further include respective separately controlled heater layers on respective ones of the dielectric windows, a first set of air fans directed along a first air flow path across the disk-shaped dielectric window, a second set of air fans directed along a second air flow path across the cylindrical dielectric window, and a controller independently controlling the respective heater layers and the first and second sets of fans.
So that the manner in which the exemplary embodiments of the present invention are attained can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be appreciated that certain well known processes are not discussed herein in order to not obscure the invention.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
DETAILED DESCRIPTIONA plasma reactor 10 depicted in
Plasma source power is inductively coupled into the processing region 101 by a set of coil antennas, including an inner coil antenna 140, a middle coil antenna 150 and an outer or side coil antenna 160, all of which are concentrically disposed with respect to each other and are coaxial with the axis of symmetry of the side wall 105. The lid assembly 110 includes a disk-shaped dielectric window 112 through which the inner and middle coil antennas 140 and 150 inductively couple RF plasma source power into the processing region 101. The disk-shaped dielectric window 112 is coaxial with the side wall 105 and has a disk-plane parallel with the plane of the workpiece support surface 121. The side coil antenna 160 inductively couples RF plasma source power into the processing region 101 through the cylindrical dielectric side window 106.
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Only the axial RF feed rod 148 is symmetrically located at the axis of symmetry of the side wall 105, while the axial feed rods 174 and 178 are located off-center, as depicted in
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As referred to above, the annular top gas plate 200 supports the disk-shaped dielectric window 112 and spans the gap or distance between the outer chamber wall 170 and the periphery of the disk-shaped dielectric window 112. The top gas plate 200 includes an annulus 202 surrounding an opening 204. A top inner edge 202a of the annulus 202 underlies and supports an outer edge 112a of the dielectric window 112 and surrounds the opening 204. A bottom outer edge 202b of the annulus 202 rests on the outer chamber wall 170. The opening 204 faces the disk-shaped dielectric window 112. The axial conductors 161-1 through 161-8 (of the outer coil antenna 160) extend through respective insulators 171 in the top gas plate 200.
The disk-shaped dielectric window 112 and the cylindrical dielectric side window 106 are heated and have their respective temperatures controlled independently of one another. They are heated and cooled independently, by cooling from a fan system described later in this specification and by independent heater elements now described. A flat heater layer 220 depicted in
A cylindrical Faraday shield layer 230 depicted in
Process gas is injected into the processing region 101 by a central dual-zone ceiling gas injector 300 (
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The axially centered exhaust assembly including the vacuum pump opening 410a and the axial exhaust passages 430 avoids asymmetries or skew in processing distribution across the workpiece 122. The annular grid 107-2 masks the processing region 101 from the discontinuities or effects of the radial struts 420. The combination of the axially centered exhaust assembly with the symmetrical distribution of RF current flow below the ground plate 184 minimize skew effects throughout the and enhance process uniformity in the processing region 101.
The ground plate 184 has a center opening 600 that is co-extensive with the inner ground shield 149. A cylindrical plenum center wall 606 is coextensive with the center opening 600. A plenum plate 610 overlies the plenum center wall 606. A return chamber 612 is enclosed between a return chamber side wall 608, the plenum plate 610, the ground plate 184 and the center wall 606. The return chamber side wall 608 includes air flow screen sections 609. Openings 614 through the ground plate 184 permit air flow between the lower plenum 502 and the return chamber 612.
An upper plenum 650 is enclosed between a top plate 655 and the plenum plate 610 by an upper plenum side wall 660 in the form of a truncated cone. Plural intake fans 665 are mounted at respective openings 667 in the upper plenum side wall 660.
The intake fans 665 draw air into the upper plenum 650 which flows down through the central opening formed by the center wall 606, the ground plate opening 600 and the middle grounded shield 149. An annular air flow plate 670 overlying the disk-shaped dielectric window 112 confines the air flow between the plate 670 and the window 112. This air may flow through the apertures 226 of the Faraday shield 220 of
The exhaust fans 504 provide cooling for the cylindrical dielectric window 106. The exhaust fans 504 draw air through intake ports 680 in the lower chamber side wall 170 and past the cylindrical dielectric window 106. By operating the intake fans 665 independently from the exhaust fans 504, the different heat loads on the different dielectric windows 106 and 112 may be compensated independently, for accurate temperature control of each window.
The controller 800 in one embodiment is programmed to govern the outputs 808-814 in response to the inputs 802, 804 to maintain the windows 106, 112 at respective target temperatures that may be furnished by a user to controller inputs 816 and 818. The controller 800 may be programmed to operate in the manner of a feedback control loop to minimize the difference between the user input 816 and the sensor input 802, and to minimize the difference between the user input 818 and the sensor input 804.
As described above, some of the advantageous effects of various ones of the foregoing embodiments include symmetrical distribution of RF power to the coil antennas for enhanced plasma distribution symmetry. Shielding of the coils from assymetrical RF current feed structures reduces skew effects in plasma distribution. Shielding of the coil antennas from one another enhances independent control of the coil antennas, for superior control of plasma density distribution. Symmetrical chamber exhaust in combination with the symmetrical coil antennas provides a high density plasma source with symmetrical plasma distribution. Separate dielectric windows for different RF coils enables independent thermal control of the different dielectric windows. Separately supporting the different dielectric windows at or over the processing region enables the chamber diameter to be increased beyond the diameter of each individual dielectric window, facilitating a large increase in chamber diameter. The moveable workpiece support electrode in combination with symmetrical coil antenna(s) allows superior control over center-to-edge plasma density distribution with a minimized asymmetrical non-uniformity component. The moveable workpiece support electrode in combination with symmetrical coil antenna(s) and in further combination with the symmetrical chamber exhaust allows even better control over center-to-edge plasma density distribution with minimized asymmetrical non-uniform component.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims
1-20. (canceled)
21. A plasma reactor comprising:
- a chamber enclosing a processing region, the chamber including an axially symmetrical side wall and a ceiling overlying the side wall;
- inner and outer current distributors to carry RF power to one or more conductive elements at the ceiling of the chamber to generate a plasma in the processing region;
- a workpiece support having a workpiece support surface to hold a workpiece in the processing region, the workpiece support having an electrode, the workpiece support surface having a plurality of backside gas channels;
- an exhaust chamber wall extending downwardly from the side wall and defining an evacuation region below the processing region;
- an exhaust pump port in a bottom of the evacuation region;
- a containment wall surrounded by an annular portion of the evacuation region and the exhaust chamber wall and enclosing a central region and separating the central region from the annular portion of the evacuation region, the containment wall including a floor extending below the workpiece support, the central region comprising a volume isolated from the evacuation region, the volume bounded on bottom and sides by the containment wall and on top by the workpiece support;
- an annular grid between the exhaust chamber wall and the containment wall, the annular grid having a plurality axial exhaust passages between the processing region and the evacuation region;
- plural radial struts below the annular grid extending between the exhaust chamber wall and the containment wall to support the containment wall;
- plural radial access passages extending from the central region through the containment wall, the plural radial struts and the exhaust chamber wall, the radial access passages providing access from outside the exhaust chamber wall to the central region;
- a power cable extending through one of the plural radial access passages into the central region to connect an RF power generator to the electrode; and
- a gas supply line extending through one of the plural radial access passages to supply gas to the backside gas channels in the workpiece support surface.
22. The plasma reactor of claim 21, wherein the evacuation region extends below the floor of the containment wall.
23. The plasma reactor of claim 22, wherein the exhaust pump port is located directly below the workpiece support surface.
24. The plasma reactor of claim 21, wherein at least some of the plurality axial exhaust passages in the annular grid are positioned over the plural radial struts.
25. The plasma reactor of claim 21, further comprising a lift mechanism positioned in said central region and having an upper end to adjust a vertical position of the workpiece.
26. The plasma reactor of claim 25, wherein the lift mechanism is configured to raise and lower the workpiece support relative to the floor of the containment wall.
27. The plasma reactor of claim 26, further comprising a bellows extending between the workpiece support and the containment wall.
28. The plasma reactor of claim 21, wherein the power cable comprises a flexible coaxial cable.
29. The plasma reactor of claim 21, wherein the power cable comprises a rigid transmission line.
30. The plasma reactor of claim 21, comprising a heater element in the workpiece support and a heater voltage supply line extending through one of the radial access passages and connected to the heater element.
31. The plasma reactor of claim 30, comprising an electrostatic chucking voltage supply line connected to the electrode in the workpiece support, the electrostatic chucking voltage supply line extending through one of the radial access passages.
32. The plasma reactor of claim 30, wherein different utilities extend through different ones of the radial access passages.
33. The plasma reactor of claim 21, wherein the side wall and containment wall are coaxial.
34. The plasma reactor of claim 21, wherein the plural radial struts are spaced at equal angular intervals around the containment wall.
35. The plasma reactor of claim 21, wherein the plural radial struts consist of exactly three radial struts.
Type: Application
Filed: Nov 19, 2018
Publication Date: Mar 21, 2019
Inventors: Andrew Nguyen (San Jose, CA), Kenneth S. Collins (San Jose, CA), Kartik Ramaswamy (San Jose, CA), Shahid Rauf (Pleasanton, CA), James D. Carducci (Sunnyvale, CA), Douglas A. Buchberger, Jr. (Livermore, CA), Ankur Agarwal (Fremont, CA), Jason A. Kenney (Sunnyvale, CA), Leonid Dorf (San Jose, CA), Ajit Balakrishna (Sunnyvale, CA), Richard Fovell (San Jose, CA)
Application Number: 16/195,670