|Publication number||USRE43508 E1|
|Application number||US 11/196,842|
|Publication date||Jul 17, 2012|
|Filing date||Aug 4, 2005|
|Priority date||Apr 30, 2001|
|Also published as||CN1505829A, CN100342480C, US6602381, US6716762, WO2002089173A1|
|Publication number||11196842, 196842, US RE43508 E1, US RE43508E1, US-E1-RE43508, USRE43508 E1, USRE43508E1|
|Inventors||Eric H. Lenz|
|Original Assignee||Lam Research Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (27), Non-Patent Citations (1), Referenced by (1), Classifications (11), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
More than one reissue application has been filed for the reissue of U.S. Pat. No. 6,602,381. The reissue applications are Ser. No. 11/196,842 (the present application), Ser. Nos. 12/078,349 and 12/078,348, both of which are divisional reissues of U.S. Pat. No. 6,602,381. Because all claims of the divisional applications have been indicated as allowable over the prior art and the PTO has advised that the claims of the divisional applications should be merged with the claims of the originally filed reissue application, such a merger is being performed and the divisional applications are being abandoned.
The present invention relates to plasma etching apparatus. More particularly, the present invention relates to improved techniques for controlling plasma formation in a plasma processing chamber.
The use of plasma-enhanced processes in the manufacture of semiconductor-based products (such as integrated circuits or flat panel displays) is well known. Generally speaking, plasma-enhanced processes involve the processing of a substrate (e.g., a glass panel or a semiconductor wafer) in a plasma processing chamber. Within the plasma processing chamber, a plasma may be formed out of appropriate etchant or deposition source gases to respectively etch or deposit a layer of material on the surface of the substrate.
A reactor top 112, formed of a conductive material such as aluminum, is disposed above substrate 106. Confinement rings 102 may be coupled in a fixed manner to reactor top 112 or may be coupled to cam-based plungers (not shown in
In general, confinement rings 102 help confine the etching plasma to the region above substrate 106 to improve process control and to ensure repeatability. Although only two confinement rings are shown in the example of
An upper electrode 114 and a baffle 116 are also coupled to reactor top 112. The upper electrode 114 may be grounded (as in the case of
When RF power is supplied to the chuck 104 (from the radio frequency generator 110), equipotential field lines are set up over the substrate 106. During plasma processing, the positive ions accelerate across the equipotential field lines to impinge on the surface of substrate 106, thereby providing the desired etch effect (such as improving etch directionality). Due to geometry factors, however, the field lines may not be uniform across the substrate surface and may vary significantly at the edge of substrate 106. Accordingly, a focus ring is typically provided to improve process uniformity across the entire substrate surface. With reference to
The equipotential field lines that are set up during plasma etching may be seen more clearly in
Furthermore, current return paths have relied on the chamber wall 118 for a return path or a return path outside the chamber. Magnetic fields are generated from the return paths and cause magnetic fields that can light and sustain a plasma outside the confined region. The dotted lines in
The inadvertent generation of plasma in the region 160 renders the etch process difficult to control and may damage components within this region. By way of example, this unconfined plasma, which may be unplanned and/or intermittent, changes the location of power absorbed by the plasma within the plasma processing chamber, thereby making it difficult to control the delivery of power to the chuck to achieve consistent, repeatable etch results. As another example, the presence of unwanted plasma in region 160 may cause damage to the chamber door (not shown), particularly to the seals that are provided therewith. The chamber door is necessary for substrate transport into and out of the chamber, and if the seals are damaged, accurate control of the chamber pressure may be difficult. When the seals and/or other components in the region 160 are inadvertently attacked by the plasma, particulate and/or polymeric contaminants may form along the chamber walls, potentially leading to contamination of the etch environment.
Accordingly, it would be desirable to provide techniques for minimizing and/or eliminating the unwanted plasma formation in the region outside of the focus ring of the plasma processing chamber.
A confinement assembly for confining a discharge within an interaction space of a plasma processing apparatus comprising a stack of rings and at least one electrically conductive member. The rings are spaced apart from each other to form slots therebetween and are positioned to surround the interaction space. At least one electrically conductive member electrically couples each ring. The electrically conductive member contacts each ring at least at a point inside of the outer circumference of each ring.
The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more embodiments of the present invention and, together with the detailed description, serve to explain the principles and implementations of the invention.
In the drawings:
Embodiments of the present invention are described herein in the context of controlling plasma formation in a plasma processing chamber. Those of ordinary skill in the art will realize that the following detailed description of the present invention is illustrative only and is not intended to be in any way limiting. Other embodiments of the present invention will readily suggest themselves to such skilled persons having the benefit of this disclosure. Reference will now be made in detail to implementations of the present invention as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following detailed description to refer to the same or like parts.
In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will, of course, be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made in order to achieve the developer's specific goals, such as compliance with application- and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure.
In accordance with one aspect of the present invention, process control is substantially improved by reducing or eliminating the unconfined plasma (i.e., the unwanted plasma that is inadvertently ignited and/or sustained outside of the focus ring and the walls of the plasma chamber). Confinement rings consists of a stack of rings spaced apart from each other to form slots therebetween and positioned to surround the interaction space. During operation of the plasma processing apparatus, the distance an exiting charged particle must travel in the slot is substantially longer than its mean free path. As the term is employed herein, the region outside of the focus ring refers to annular region of the plasma processing chamber which is external to the column of space whose outer periphery is defined by the circumference of the focus ring. The plasma is preferably confirmed within this column of space. Outside of the focus ring, the electric field is preferably reduced to the point where plasma can no longer be sustained. By eliminating the unconfined plasma, the amount of power absorbed by the etching plasma that is disposed above the substrate may be more consistent from substrate to substrate, thereby rendering the etch repeatable. The elimination of the unconfined plasma also helps reduce the corrosion or break down of components disposed in the region outside of the focus ring (e.g., door seals).
In accordance with one embodiment of the present invention, there is provided a confinement assembly, including a stack of focus rings configured to concentrate the equipotential field lines in the focus ring body. The focus rings preferably include at least one cavity disposed evenly around each ring and a corresponding number of electrically conductive members for returning the current to the ground. Each cavity receives and accommodates one member. It is believed that this configuration substantially reduces the density of equipotential field lines in the region outside of the focus ring. By substantially reducing the density of equipotential field lines in the near-vacuum region outside of the focus ring, the amount of energy acquired by any charged particle that leaks into this area is substantially reduced, thereby essentially eliminating the possibility of plasma formation and/or sustenance in this region.
The features and advantages of the present invention may be better understood with reference to
The confinement rings 216 also include at least one cavity 302, equidistant from each other, as illustrated in
The power supply 212 provides an RF current to the lower electrode 206. During the process, the current travels towards the upper electrode 204 through the confinement region 214. Because the upper electrode 204 electrically contacts members 218, the current travels through this preferred path, i.e. Members 218, towards the grounded shield 219.
The presence of the members 218 embedded within the cavities 302 of the confinement rings 216 provides a preferred return path that substantially reduces the density of the magnetic fields in the upper portion of annular region 220, i.e., the region outside of the focus and confinement rings 216. The confinement rings 216 isolate the plasma and the chamber 202 from the preferred return paths. Being embedded in the confinement rings 216, the stray magnetic fields are kept from penetrating into the volume between the outer edge of the confinement rings 216 and the chamber 202, i.e. the region 220. The plasma stays confined and since the return paths are in the confinement ring area, the plasma cannot damage the return path materials. Therefore the stray magnetic fields are substantially reduced outside the confinement rings 216.
Other embodiments may exist in which an electrically conductive member connects each ring at least a point inside of the outer circumference of the ring. The magnetic fields generated by the electrically conductive member are substantially reduced from an excluded region when the member is disposed within the ring. The member may include any shape or form that allows the current to return to the ground while substantially reducing the magnetic fields generated by the member. Examples of members may be rods, strings, or beams connecting the rings at least at a point inside of the outer circumference of the rings.
While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US8677590 *||Sep 9, 2013||Mar 25, 2014||Lam Research Corporation||Plasma confinement structures in plasma processing systems and methods thereof|
|U.S. Classification||156/345.43, 118/723.00E, 216/67|
|International Classification||C23C16/00, H01J37/32, H01L21/306, C23F1/00|
|Cooperative Classification||H01J37/32623, H01J37/32642|
|European Classification||H01J37/32O8D, H01J37/32O8|