# Patent

## Title
Lower liner with integrated flow equalizer and improved conductance

## Abstract

A plasma processing chamber has a lower liner with an integrated flow equalizer. In an etching process, the processing gases may be unevenly drawn from the processing chamber which may cause an uneven etching of the substrate. The integrated flow equalizer is configured to equalize the flow of the processing gases evacuated from the chamber via the lower liner.

## Background
BACKGROUND
1. Field
Embodiments of the present invention generally relate to a plasma processing chamber having a lower chamber liner.
2. Description of the Related Art
Modern integrated circuits are complex devices that may include millions of components on a single chip; however, the demand for faster, smaller electronic devices is ever increasing. This demand not only requires faster circuits, but it also requires greater circuit density on each chip. In order to achieve greater circuit density, minimal dimensions, or critical dimensions, of features of integrated circuit components must be reduced as well.
Reduction in the critical dimensions of integrated circuit component features requires strict process uniformity across a substrate in order to maintain high yields. One problem associated with conventional plasma etch processes used in manufacturing of integrated circuits is non-uniformity of an etch rate across the substrate. Such non-uniformity may be due, in part, to a vacuum pump drawing an etching gas toward an exhaust port provided in an etch chamber and away from the substrate. Since gases are more easily pumped away from areas of the chamber that are closest to the exhaust port, the etching gas is pulled toward the exhaust port and away from the substrate. This creates a non-uniform etch on the substrate positioned therein, which may significantly decrease the performance of the resulting integrated circuit and significantly increase the cost of fabrication.
Therefore, a need exists for an apparatus for uniformly etching material layers during the manufacture of integrated circuits.
SUMMARY
In one embodiment, an integrated flow equalizer is provided in a plasma processing chamber. In one embodiment, the integrated flow equalizer is configured to protect lower chamber walls from exposure to plasma and to allow improved gas flow conductance. In one embodiment, a lower chamber liner is elevated from a chamber bottom wall to create a high conductance plenum between the lower chamber liner and the bottom wall. In one embodiment, the lower chamber liner has an aperture formed therethrough configured to equalize the flow of processing gas drawn by a vacuum pump in fluid communication with the plenum resulting in uniform plasma flow and uniform etching across a substrate situated in the plasma processing chamber.
In one embodiment of the present invention, an apparatus for plasma processing comprises a chamber body, a first chamber liner disposed within the chamber body, and a second chamber liner disposed within the chamber body below the first chamber liner. The second chamber liner is electrically coupled to the first chamber liner. The second chamber liner is in an elevated position with respect to a bottom surface of the chamber body such that an annular plenum is defined between the second chamber liner and the bottom surface of the chamber body. The second chamber liner has an aperture formed therethrough and configured to equalize the flow of processing gas drawn by a vacuum pump in fluid communication with the plenum.
In another embodiment of the present invention, an annular chamber liner for a plasma chamber comprises a bottom wall, an inner wall extending upwardly from the bottom wall, and an outer wall extending upwardly and outwardly from the bottom wall. The annular chamber liner has a plurality of slots extending through the bottom and outer walls. In one embodiment, the slots equalize the flow of processing gas. The plurality of slots is arranged such that at least one slot is present within each quadrant of the annular chamber liner.
In another embodiment of the present invention, an etching apparatus comprises a chamber body, a substrate support pedestal disposed in the chamber body, a gas introduction showerhead disposed in the chamber opposite the substrate support, and an upper chamber liner disposed in the chamber body. The upper chamber liner is disposed in the chamber body such that the substrate support pedestal, the gas introduction showerhead, and the first chamber liner at least partially enclose a processing area. An annular baffle is coupled to and surrounds the substrate support pedestal. A lower chamber liner, comprising a bottom wall, an inner wall, and an outer wall sloping upwardly and outwardly from the bottom wall, is provided below the annular baffle and surrounds the substrate support pedestal. The lower chamber liner is disposed within the chamber body such that an annular plenum is defined between the bottom and outer walls of the lower chamber liner and a bottom and outer wall of the chamber body. The lower chamber liner has a slot therethrough to equalize the flow of processing as drawn by a vacuum pump in fluid communication with the plenum.



BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the embodiments of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical 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.
FIG. 1 is a schematic cross-sectional view of an etching apparatus according to one embodiment of the invention.
FIG. 2A is a partial, schematic cross-sectional view of a lower chamber liner with an integrated flow equalizer according to one embodiment of the invention.
FIG. 2B is a schematic bottom view of the chamber liner in FIG. 2A.
FIG. 3 is a schematic bottom view of another embodiment of the lower chamber liner of the present invention.



DETAILED DESCRIPTION
Embodiments of the present invention generally comprise a plasma processing chamber having a lower chamber liner with an integrated flow equalizer. Various embodiments of the present invention will be described below in relation to an etching chamber. However, a variety of plasma deposition and etching chambers may benefit from the teachings disclosed herein, and in particular, dielectric etching chambers such as the ENABLER® etch chamber, which may be part of a semiconductor wafer processing system such as the CENTURA® system, the PRODUCER® etch chamber, the eMax® etch chamber, among others, all of which are available from Applied Materials, Inc. of Santa Clara, Calif. It is contemplated that other plasma reactors, including those from other manufacturers, may be adapted to benefit from the invention.
FIG. 1 is a schematic cross-sectional view of an etching apparatus 100 according to one embodiment of the present invention. The apparatus 100 comprises a chamber body 102 in which a substrate 104 may be disposed on a pedestal 106 opposite a gas introduction showerhead 108. Processing gas may be supplied to the chamber 102 through the showerhead 108. Processing gas may be supplied to the chamber 102 through the showerhead 108 from a gas source 110. In one embodiment, the pedestal 106 may be biased with current from a power source 130. In another embodiment, the showerhead 108 may be biased with a current from a power source 112.
During processing, the processing gas is supplied through the showerhead 108 into the processing area 128 where the processing gas, in plasma form, proceeds to etch material from the substrate 104. The plasma may extend not only to the substrate 104, but it may extend to the chamber walls as well. To protect the chamber walls from the plasma, an upper liner 126 may be present. The upper liner 126 may protect the chamber walls from exposure to the plasma. Additionally, the upper liner 126 may be removed during processing downtime to be cleaned or replaced.
An annular baffle 116 may surround the substrate 104 and the pedestal 106. The annular baffle 116 may extend close to the upper liner 126 and have a plurality of slots therethrough. The slots in the baffle 116 permit processing gas to be drawn therethrough to be evacuated out of the processing chamber body 102. The slots may be sized to eliminate or reduce the amount of plasma that passes through the baffle 116.
Processing gas may also be drawn around the baffle 116 in the area between the baffle 116 and the upper liner 126. Generally, most of the plasma is confined to the processing area 128, but some plasma may extend out beyond the outer diameter of the baffle 116 and be pulled below the baffle 116. A lower chamber liner 120 may be present to protect the lower chamber walls from the plasma. The lower liner 120 may be removed during processing downtime to be cleaned or replaced. The lower liner 120 may be coupled to the bottom of the chamber body 102 by a fastening mechanism 124. In one embodiment, the fastening mechanism 124 may comprise a screw. In one embodiment, the fastening mechanism 124 may be countersunk into the lower liner 120.
A vacuum pump 114 may evacuate the processing chamber body 102 and thus pull processing gases through the baffle 116 and through the area between the baffle 116 and the upper liner 126. The lower chamber liner 120 may be configured in an elevated position with respect to the bottom of the chamber body 102, such that a large plenum 122 may exist between the bottom surface 121 of the lower chamber liner 120 and the bottom surface 101 of the chamber body 102 around the entire periphery of the chamber body 102. Additionally, the lower chamber liner 120 may have an upwardly sloping outer wall 123, such that the plenum 122 extends upwardly around the entire periphery of the lower chamber liner 120 between the outer wall 123 of the lower chamber liner and the wall 103 of the chamber body 102. The lower chamber liner 120 may contain a plurality of apertures (not shown in FIG. 1) to equalize the flow of processing gas drawn therethrough. Example of suitable apertures can be seen in FIGS. 2B and 3. The large plenum 122 functions to broadly distribute the vacuum draw. In one embodiment, the greatest draw through the lower chamber liner 120 may be achieved in the area closest to the exhaust port 113 in the chamber body 102, which may lead to non-uniformity in the etch plasma across the substrate 104. In one embodiment, to further promote, a uniform vacuum draw of process gas across the annulus of the lower chamber liner 120, the size and positioning of the apertures in the lower chamber liner 120 may be arranged as described below with respect to FIGS. 2B, and 3.
In addition, the lower chamber liner 120 is electrically coupled to the upper chamber liner 126, both of which are grounded. When an RF plasma is present, the RF current seeking a return path to ground may travel along the upper liner 126 and/or the lower liner 120, whichever has the path of least resistance. Electrically coupling the lower chamber liner 120 to the upper chamber liner 126 provides substantial surface area for the RF current seeking a path to ground. As a result, plasma may extend more uniformly over the substrate 104 in the chamber 100, resulting in increased etching uniformity.
FIG. 2A is a schematic, partial cross-sectional view of a lower chamber liner 200 according to one embodiment of the present invention. The lower liner comprises an inner wall 202 that extends up from the bottom wall 204. The inner wall 202 protects the area under the pedestal from plasma exposure. The outer wall 206 is upwardly sloping from the bottom wall 204 to the outer periphery of the lower chamber liner 200. A plurality of gas passages 208 extend across and through the outer wall 206 and the bottom wall 204 as depicted in FIGS. 2B and 3 and described below.
FIG. 2B is a schematic bottom view of a lower chamber liner 200 of FIG. 2A. As shown in FIG. 2B, the gas passages 208 in the bottom wall 204 and the side wall 206 are broadly spaced apart in a first quadrant 210, which is to be positioned adjacent the exhaust port 113 in the chamber body 102. The gas passages 208 may be more narrowly spaced in a second quadrant 220 and a third quadrant 230 extending away from the first quadrant 210 of the lower chamber liner 200. In one embodiment, the spacing of the gas passages 208 may decrease across the second quadrant 220 and the third quadrant 230 extending away from the first quadrant 210. In another embodiment, the gas passages may be equally spaced across the second quadrant 220 and the third quadrant 230. The gas passages 208 are most narrowly spaced across the fourth quadrant 240, which is to be positioned farthest from the exhaust port 113 of the chamber body 102.
FIG. 3 is a schematic bottom view of a lower chamber liner 300 according to another embodiment of the present invention. In this embodiment, thin gas passages 307 are broadly spaced across the first quadrant 310 of the chamber liner 300, which is to be positioned adjacent the exhaust port 113 in the chamber body 102. Mid-sized gas passages 308, which are larger than the thin gas passages 307, are positioned more narrowly across the second quadrant 320 and the third quadrant 330 extending away from the first quadrant 310. Large gas passages 309, which are larger than the mid-sized gas passages 308, are positioned across the fourth quadrant 340 of the lower chamber liner 120, which is to be positioned farthest from the exhaust port 113 of chamber body 102. The large gas passages 309 are separated by thin, structural ribs. In one embodiment, a single gas passage 309 extends across the entire fourth quadrant 340. In another embodiment, the fourth quadrant 340 is divided into two gas passages 309 having a single structural rib 341 therebetween.
By configuring the gas passages 208, 307-309 extending through the lower chamber liner 120, 200, 300 such that the area farthest from the exhaust port 113 of the chamber 100 has the largest opening and the area adjacent the exhaust port 113 has the smallest area, the uniformity of vacuum draw from the processing area 128 may be increased. Correspondingly, by evening out the vacuum draw from the processing area 128, the plasma distribution, and ultimately, etching uniformity may be increased as well.
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. An apparatus for plasma processing, comprising:
a chamber body;
a first chamber liner disposed within the chamber body; and
a second chamber liner disposed within the chamber body below the first chamber liner and electrically coupled to the first chamber liner, wherein the second chamber liner comprises:
a bottom wall; and
an outer wall sloping upwardly and outwardly from the bottom wall, wherein a plurality of apertures are disposed through the bottom and outer walls, wherein at least one of the apertures extends through both the bottom wall and the outer wall, and wherein the second chamber liner is in an elevated position with respect to a bottom surface of the chamber body such that an annular plenum is defined between the second chamber liner and the bottom surface of the chamber body.

2. The apparatus of claim 1, wherein the second chamber liner further comprises
an inner wall extending upwardly from the bottom wall.

3. The apparatus of claim 2, wherein a first portion of the annular plenum is defined between the bottom wall of the second chamber liner and the bottom surface of the chamber body.

4. The apparatus of claim 3, wherein a second portion of the annular plenum is defined between the outer wall of the second chamber liner and a wall of the chamber body.

5. The apparatus of claim 1, wherein at least one aperture is present in each quadrant of the second chamber liner.

6. The apparatus of claim 5, wherein fewer apertures are present in a first quadrant of the second chamber liner than in an opposing quadrant.

7. The apparatus of claim 6, wherein the first quadrant of the second chamber liner is positioned adjacent an exhaust port within the chamber body.

8. The apparatus of claim 5, wherein smaller apertures are present in a first quadrant of the second chamber liner than in an opposing quadrant.

9. The apparatus of claim 8, wherein the first quadrant of the second chamber liner is positioned adjacent an exhaust port within the chamber body.

10. The apparatus of claim 1, wherein the plurality of apertures are slots.

11. The apparatus of claim 10, wherein one quadrant of the second chamber liner has fewer slots than the other three quadrants.

12. The apparatus of claim 10, wherein one quadrant of the second chamber liner has a greater number of slots than the other three quadrants.

13. The apparatus of claim 10, wherein one quadrant of the second chamber liner has larger slots than the other three quadrants.

14. The apparatus of claim 10, wherein one quadrant of the second chamber liner has smaller slots than the other three quadrants.