Inductively Coupled Plasma Source with Multiple Dielectric Windows and Window Supporting Structure
A plasma reactor enclosure has a metallic portion and a dielectric portion of plural dielectric windows supported on the metallic portion, each of the dielectric windows extending around an axis of symmetry. Plural concentric coil antennas are disposed on an external side of the enclosure, respective ones of the coil antennas facing respective ones of the dielectric windows.
This application is a continuation of U.S. application Serial No. 13/666,280, filed Nov. 1, 2012, which claims the benefit of U.S. Provisional Application Serial No. 61/673,937, filed Jul. 20, 2012, the disclosures of which are incorporated 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 enclosure having an axis of symmetry and a workpiece support within the enclosure, the workpiece support and the enclosure defining a processing region. The enclosure includes a metallic portion and a dielectric portion including plural dielectric windows supported on the metallic portion, each of the dielectric windows extending around the axis of symmetry, the enclosure having a diameter greater than the diameter of at least one of the dielectric windows. Plural concentric coil antennas are disposed on an external side of the enclosure, respective ones of the coil antennas facing respective ones of the dielectric windows. Respective RF power sources are coupled to respective ones of the coil antennas.
In one embodiment, a first one of the dielectric windows includes a disk-shaped dielectric window, the enclosure having a diameter greater than the diameter of the disk-shaped dielectric window. A second one of the dielectric windows is a cylindrical dielectric window. The cylindrical dielectric window is below a plane of the disk-shaped dielectric window.
In an embodiment, the metallic portion includes: (a) a cylindrical chamber body wall surrounding the cylindrical dielectric window, and (b) an annular top gas plate including a peripheral portion supported on the chamber body wall, and a central opening through the annular top gas plate, wherein the disk-shaped dielectric window includes a circular edge portion supported on an edge of the central opening.
The disk-shaped dielectric window has a diameter less than the diameter of the chamber body wall. A gap separates the chamber body wall from the disk-shaped dielectric window, the peripheral portion of the top gas plate spanning the gap and the disk-shaped dielectric window is suspended over the central opening of the top gas plate.
In an embodiment, first and second ones of the coil antennas are concentrically disposed over the disk-shaped dielectric window, and a third one of the coil antennas has a diameter exceeding a diameter of the cylindrical dielectric window and surrounds the cylindrical dielectric window.
The plasma reactor may further include a center gas disperser in a center of the disk-shaped dielectric ceiling and disposed to spray gas into the processing region, and the top gas plate may include: (a) plural gas injection orifices circularly arranged about the peripheral portion, (b) plural gas supply ports, and (c) a first hierarchy of equal length recursive gas flow paths from a first one of the gas supply ports to the plural gas injection orifices.
The center gas disperser may include a pair of opposing input ports, the reactor further including at least a pair of opposing gas flow conduits extending radially across the disk-shaped dielectric window to the opposing input ports of the center gas disperser. And, the top gas plate further includes a second hierarchy of equal length recursive gas flow paths from a second one of the gas supply ports to the pair of gas flow conduits.
The plasma reactor may further include a first heater layer on the disk-shaped dielectric window and including a radially outer portion and plural fingers extending radially inwardly from the radially outer portion. In an embodiment, the pair of opposing gas flow conduits is enclosed in respective ones of the plural fingers of first heater layer. The plasma reactor may further include a second heater layer on the cylindrical dielectric window, the second heater layer including a grid of axial fingers.
In an embodiment, the plasma reactor further includes: (a) a cylindrical shield coaxial with the axis of symmetry and located between the first and second coil antennas and facing an inner radial portion of the disk-shaped dielectric window, (b) a top fan plenum in a central air flow path including having an axial path passing through an interior of the cylindrical shield and a radial path extending across a surface of the disk-shaped dielectric window, and (c) plural intake fans coupled to the top fan plenum. In one embodiment, an annular air flow plate overlies the disk-shaped dielectric window and has a center air flow aperture open to the interior of the cylindrical shield and forming a top boundary of the radial path of the central air flow path. The annular air flow plate confines the radial path to regions between the plural fingers of the first heater layer.
In an embodiment, a side air flow passage is defined between the cylindrical dielectric window and cylindrical chamber body side wall, and the plasma reactor further includes: (a) a side fan plenum at an axial location between the top fan plenum and the cylindrical dielectric window, the side fan plenum open to the side air flow passage and including plural side fan plenum openings, and (b) plural exhaust fans at the plural side fan plenum openings.
An embodiment further includes: (a) an RF power feed assembly coupled to the plural coil antennas and including plural conductive legs, (b) a ground plate extending radially and having openings through which respective ones of the legs extend, the ground plate providing a boundary between an upper region in which at least some of the plural conductive legs are distributed asymmetrically and a lower region in which the respective ones the legs are distributed symmetrically with respect to the axis of symmetry. and (c) wherein the ground plate includes a circular center aperture aligned with the axial path of the central air flow path.
A first temperature sensor may be provided at the disk-shaped dielectric window and a second temperature sensor may be provided at the cylindrical dielectric window, with a controller coupled to the first and second temperature sensors, the controller being coupled to govern levels of power delivered respectively to the first heater layer, the second heater layer, the plural intake fans, the plural exhaust fans, and to respective ones of the coil antennas. In an embodiment, the controller is programmed to control the power levels delivered to the first heater layer and the plural intake fans in response to an output of the first temperature sensor. The controller is further programmed to control the power levels delivered to the second heater layer and the plural exhaust fans in response to an output of the second temperature sensor.
In one embodiment, the plasma reactor further includes 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.
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 (FIG. 1A) and a circular array of peripheral (side) gas injectors 310 (
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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 processing region 101 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 asymmetrical 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:
- an enclosure having an axis of symmetry and a workpiece support within the enclosure, the workpiece support and the enclosure defining a processing region, the enclosure including a cylindrical metallic portion, a cylindrical dielectric window extending around the said axis of symmetry and supported on the metallic portion, a bottom edge of the cylindrical dielectric window positioned above the workpiece support such that a workpiece on the workpiece support is supported below the bottom edge, a metallic plate having a central opening and supported on the cylindrical dielectric window, and a disk-shaped dielectric window supported on the plate and extending around the said axis of symmetry and overlying the central opening, a bottom face of the disk-shaped dielectric window positioned above a top edge of the cylindrical dielectric window, an inner diameter of cylindrical dielectric window being greater than an outer diameter of the disk-shaped dielectric window; and
- a plural concentric coil antennas disposed on an external side of said enclosure, the plural concentric coil antennas including a first coil antenna positioned above and facing the disk-shaped window, and a second coil antenna surrounding and facing the cylindrical dielectric window.
22. The plasma reactor of claim 21, wherein the disk-shaped dielectric window has a circular edge portion supported on an edge of said central opening.
23. The plasma reactor of claim 21, wherein the metallic plate provides an annular top gas plate having a peripheral portion supported on the cylindrical dielectric window.
24. The plasma reactor of claim 23, wherein the top gas plate has plural gas injection orifices circularly arranged about the peripheral portion.
25. The plasm reactor of claim 24, further comprising a center gas disperser in a center of said disk-shaped dielectric window and disposed to introduce gas into the processing region.
26. The plasma reactor of claim 21, wherein the metallic plate abuts the top edge of the cylindrical dielectric window.
27. The plasma reactor of claim 21, the metallic plate comprises a planar bottom surface extending inwardly from the top edge of the cylindrical dielectric window.
28. The plasma reactor of claim 21, wherein the metallic plate extends radially outward past the dielectric window.
29. The plasma reactor of claim 28, comprising at least one insulator extending axially through the metallic plate, and an axial conductor extending through the insulator and connected to the second coil antenna to supply RF power to the second coil antenna.
30. The plasma reactor of claim 21, comprising a third coil antenna, the third coil antenna disposed over and facing the disk-shaped dielectric window and concentric and surrounding the first coil antenna.
31. The plasma reactor of claim 21, further comprising a first heater layer on the disk-shaped dielectric window.
32. The plasma reactor of claim 31, further comprising a second heater layer on the cylindrical dielectric window.
33. The plasma reactor of claim 21, wherein the workpiece support comprises a pedestal and a post to hold the pedestal above a bottom of the processing region.
34. The plasma reactor of claim 33, wherein the cylindrical metallic portion extends to the bottom of the processing region.
Type: Application
Filed: Aug 24, 2017
Publication Date: Dec 7, 2017
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 (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: 15/685,787