Faraday Shield Disposed Within An Inductively Coupled Plasma Etching apparatus
An apparatus and method is provided for positioning and utilizing a Faraday shield in direct exposure to a plasma within an inductively coupled plasma etching apparatus. Broadly speaking, the Faraday shield configuration maintains a condition of an etching chamber window. At a minimum, positioning the Faraday shield between the window and the plasma prevents erosion of the window resulting from plasma sputter and shunts heat generated by an etching process away from the window.
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This application is a divisional application of U.S. patent application Ser. No. 10/232,564, filed on Aug. 30, 2002, from which priority under 35 U.S.C. 120 is claimed, which is incorporated herein by reference in its entirety for all purposes.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates generally to semiconductor fabrication, and more particularly, to apparatuses and methods for using a Faraday shield in direct exposure to a plasma within an inductively coupled plasma etching apparatus.
2. Description of the Related Art
In semiconductor manufacturing, etching processes are commonly and repeatedly carried out. As is well known to those skilled in the art, there are two types of etching processes: wet etching and dry etching. Dry etching is typically performed using an inductively coupled plasma etching apparatus.
A chuck 117 is positioned within the chamber internal cavity 102 near the bottom inner surface of the etching chamber. The chuck 117 is configured to receive and hold a semiconductor wafer (i.e., “wafer”) 119 upon which the etching process is performed. The chuck 117 can be electrically charged using an RF power supply 123. The RF power supply 123 is connected to matching circuitry 121 through a connection 127. The matching circuitry 121 is connected to the chuck 117 through a connection 125. In this manner, the RF power supply 123 is connected to the chuck 117.
A coil 133 is positioned above the window 111. The coil 133 is fabricated from an electrically conductive material and includes at least one complete turn. The exemplary coil 133 shown in
The plasma 155 contains various types of radicals in the form of positive and negative ions. The chemical reactions of the various types of positive and negative ions are used to etch the wafer 119. During the etching process, the coil 133 performs a function analogous to that of a primary coil in a transformer, while the plasma 155 performs a function analogous to that of a secondary coil in the transformer.
The reaction products generated by the etching process may be volatile or non-volatile. The volatile reaction products are discarded along with used reactant gas through the gas exhaust port. The non-volatile reaction products, however, typically remain in the etching chamber. The non-volatile reaction products may adhere to the chamber walls 101 and the window 111.
In contrast to the deposition 157 of non-volatile reaction products on the window 111, plasma 155 sputter can cause erosion of the window 111.
In addition to the deposition 157 and erosion 159 problems associated with the window 111, selection of the window 111 material is limited by the thermal output of the etching process. During the etching process, the window 111 is exposed directly to the plasma 155. Therefore, the window 111 must absorb not only the heat generated by the bulk plasma 155 but also the heat transferred to the window 111 from sputtered plasma 155. The thermal properties of the window 111 must be sufficient to accommodate the thermal energy absorbed by the window 111 during the etching process. The thermal properties of the window 111 are primarily defined by the window 111 material.
Quartz is commonly used as a window 111 material in the inductively coupled plasma etching apparatus 100. The primary benefit associated with quartz is its low coefficient of thermal expansion. Thus, in the presence of a high temperature gradient from its center to its edge, the quartz window 111 will not experience differential thermal expansion leading to cracking and failure. Quartz, however, has a relatively low tensile strength. Thus, a large (e.g., ≧1.75 inch) quartz window 111 thickness is typically required to span the opening above the chamber internal cavity 102. The quartz window 111 is relatively expensive and costly to replace upon failure. Thus, it is desirable to have more flexibility in using window 111 materials other than quartz.
Ceramic has been used as an alternative to quartz for the window 111 material. Ceramic is more durable, stronger, and less expensive that quartz. However, ceramic materials have a higher coefficient of thermal expansion than quartz. Thus, when exposed to a high thermal output associated with certain etching processes, the ceramic window 111 is more susceptible to experiencing differential thermal expansion leading to cracking and failure. For ceramic window 111 materials to be used in higher thermal output etching processes, it is necessary to maintain a low temperature gradient across the ceramic window 111 to prevent cracking and failure.
In view of the foregoing, there is a need for an apparatus and a method to protect the window from deposition of non-volatile reaction products, erosion due to plasma sputter, and high temperatures resulting from the heat source associated with the etching process.
SUMMARY OF THE INVENTIONBroadly speaking, the present invention fills these needs by providing an apparatus and method to maintain a condition of an etching chamber window by configuring a Faraday shield between the etching chamber window and a plasma. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method. Several embodiments of the present invention are described below.
In one embodiment, an apparatus for plasma processing is disclosed. The apparatus includes a chamber having a substrate support, surrounding walls, and an upper surface to define a plasma containment region. A metal shield is disposed within the chamber. The metal shield is oriented over the substrate support and proximate to the upper surface of the chamber. The metal shield is located substantially above the plasma containment region of the chamber. The metal shield is capable of being in direct contact with a plasma to be generated in the plasma containment region.
In another embodiment, a plasma etching apparatus is disclosed. The plasma etching apparatus includes a chamber having an interior cavity defined by a bottom and side walls. The side walls are configured to have a top surface. A plate is configured to interface with the top surface of the side walls. The plate has an upper surface and a lower surface. The plate is further configured to have an opening centrally located above the interior cavity. A window is configured to interface with the upper surface of the plate. The window covers the opening centrally located above the interior cavity. A metal shield is disposed immediately below the window and inside the chamber. The metal plate is capable of being exposed directly to a plasma to be generated in the interior cavity.
In another embodiment, a method for making an inductively coupled plasma etching apparatus is disclosed. The method includes providing a chamber having an interior cavity defined by a bottom, a top, and side walls. The top is configured to have an opening. The method further includes placing a metal shield over the chamber interior cavity such that the metal shield is directly exposed to the chamber interior cavity. The method also includes placing a window above the metal shield such that the window creates a seal around the top opening of the chamber. The metal shield remains inside the chamber interior cavity and below the window. The method further includes placing a coil above the window.
In another embodiment, a method is disclosed for making an inductively coupled plasma etching apparatus. The method includes providing a chamber having an interior cavity defined by a bottom and side walls, wherein each of the side walls has a top surface. The method also includes placing a thermally conductive adapter plate to interface with the top surface of the side walls so as to form a seal between the thermally conductive adapter plate and the side walls. The thermally conductive adapter plate is defined to have a central opening over the chamber interior cavity. The method further includes placing a metal shield to cover the central opening of the thermally conductive adapter plate. The metal shield is also placed to establish a thermal connection between the metal shield and the thermally conductive adapter plate. Thus, the metal shield is placed to be in direct exposure to the chamber interior cavity. Additionally, the method includes placing a window above the metal shield and thermally conductive adapter plate so as to form a seal between the window and the thermally conductive adapter plate. A coil is then placed above the window.
In another embodiment, a method is disclosed for making an inductively coupled plasma etching apparatus. The method includes providing a chamber defined by a bottom, side walls, and an upper heat dissipation structure. The upper heat dissipation structure is defined to include an opening through which an interior cavity of the chamber is exposed. The method also includes placing a thermally conductive metal shield in thermal communication with the upper heat dissipation structure so as to cover the opening within the heat dissipation structure. Thus, the thermally conductive metal shield is directly exposed to the chamber interior cavity. The method further includes placing a window above the thermally conductive metal shield so as to form a seal between the window and the upper heat dissipation structure around the thermally conductive metal shield. Additionally, the method includes placing a coil above the window.
In another embodiment, a method is disclosed for making an inductively coupled plasma etching apparatus. The method includes providing a chamber defined by a bottom and side walls, wherein each of the side walls has a top surface. The method also includes forming a chamber top to include a heat dissipation structure and a metal shield thermally integrated with the heat dissipation structure. The heat dissipation structure defines a peripheral portion of the chamber top. The metal shield defines a central portion of the chamber top. Also, the metal shield is substantially planar with a top surface of the heat dissipation structure. The method further includes placing the chamber top to interface with the top surface of the side walls so as to form a seal between the chamber top and the side walls. Additionally, the method includes placing a window above the chamber top so as to form a seal between the window and the peripheral portion of the chamber top. Then, a coil is placed above the window.
The advantages of the present invention are numerous. Most notably, the apparatus and method for configuring a Faraday shield between the etching chamber window and a plasma avoids the problems of the prior art by maintaining the condition of the etching chamber window. The present invention avoids one problem of the prior art by preventing erosion of the etching chamber window resulting from plasma sputter. The present invention avoids another problem of the prior art by shunting heat generated by an etching process away from the etching chamber window.
Other aspects and advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the present invention.
BRIEF DESCRIPTION OF THE DRAWINGSThe invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:
An invention is disclosed for apparatuses and methods for positioning and using a Faraday shield in direct exposure to a plasma within an inductively coupled plasma etching apparatus. Broadly speaking, the present invention maintains a condition of an etching chamber window. Configuring the Faraday shield between the window and the plasma prevents erosion of the window resulting from plasma sputter and shunts heat generated by an etching process away from the window. The present invention solves one problem of the prior art by reducing the window replacement frequency driven by erosion of the window due to plasma sputter. The present invention solves another problem of the prior art by allowing the use of a larger variety of window materials through a relaxation of thermal performance requirements afforded by the shunting of heat away from the window.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention.
An adapter plate liner 213 is configured to cover the adapter plate 203 surface exposed to a chamber internal cavity 102. The adapter plate liner 213 also extends between the chamber walls 101 and the adapter plate 203. The adapter plate liner 213 thickness is nominally about 0.06 inch. However, the adapter plate liner 213 thickness may be larger or smaller depending on the etching chamber configuration and etching process requirements. Typically, there is a region of free space between the adapter plate liner 213 and the adapter plate 203. Therefore, an o-ring 217 is used to provide a vacuum seal between the adapter plate liner 213 and the adapter plate 203 at a location between the adapter plate 203 and the chamber walls 101. An RF gasket 219 is provided outside of the o-ring 217 to maintain continuity of ground between the adapter plate liner 213 and the adapter plate 203.
A chuck 117 is positioned near the bottom inner surface of the etching chamber. The chuck 117 is configured to receive and hold a semiconductor wafer (i.e., “wafer”) 119 upon which the etching process is performed. The chuck 117 can be electrically charged using an RF power supply (not shown). A bucket liner 215 is configured to form an annular trough surrounding the chuck 117. The bucket liner 215 is further configured to cover the chamber walls 101 extending upward from the annular trough. The bucket liner 215 also extends between the chamber walls 101 and the adapter plate 203. Typically, there is a region of free space between the bucket liner 215 and the chamber walls 101. Therefore, an o-ring 221 is used to provide a vacuum seal between the bucket liner 215 and the chamber walls 101 at a location between the adapter plate 203 and the chamber walls 101. An RF gasket 223 is provided outside of the o-ring 221 to maintain continuity of ground between the bucket liner 215 and the chamber walls 101.
A coil 133 composed of an electrically conductive material and including at least one complete turn is configured above the window 111. The exemplary coil 133 shown in
The Faraday shield 201 is positioned immediately below the window 111 to be directly exposed to the chamber internal cavity 102. The Faraday shield 201 is configured to be substantially parallel to the window 111. The Faraday shield 201 generally has a thickness ranging from about 0.03 inch to about 1 inch. A nominal Faraday shield 201 thickness is about 0.19 inch. The Faraday shield 201 is generally composed of an electrically conductive material such as aluminum. Hence, the Faraday shield 201 is also referred to as a metal shield 201. The Faraday shield 201 may also be coated or anodized with a material compatible with the etching process environment such as alumina. Depending on the Faraday shield 201 configuration, the coating thickness can range from about 0.002 inch to about 0.01 inch. Numerous other Faraday shield 201 and coating materials may be used so long as the Faraday shield 201 functionality is not compromised.
A space 205 exists between the Faraday shield and the window 111. A distance across the space 205 perpendicular to both the Faraday shield 201 and the window 111 is generally within the range from about 0.005 inch to 0.04 inch. A nominal perpendicular distance across the space 205 is about 0.02 inch. As previously mentioned, the Faraday shield 201 shown in
During operation, a reactant gas flows through the etching chamber from a gas lead-in port 220 to a gas exhaust port (not shown). High frequency power (i.e., RF power) is then applied from a power supply (not shown) to the coil 133 to cause an RF current to flow through the coil 133. The RF current flowing through the coil 133 generates an electromagnetic field about the coil 133. The electromagnetic field generates an inductive current within the etching chamber. The inductive current acts on the reactant gas to generate the plasma. High frequency power (i.e., RF power) is applied from a power supply (not shown) to the chuck 117 to provide directionality to the plasma such that the plasma is “pulled” down onto the wafer 119 surface to effect the etching process.
The plasma contains various types of radicals in the form of positive and negative ions. The chemical reactions of the various types of positive and negative ions are used to etch the wafer 119. During the etching process, the coil 133 performs a function analogous to that of a primary coil in a transformer, while the plasma performs a function analogous to that of a secondary coil in the transformer.
During operation, the Faraday shield 201 ensures that an electrostatic field generated between the coil 133 and the plasma is uniformly distributed across the window 111 interior surface. With the Faraday shield 201 configured below the window 111 and in direct exposure to the plasma, the Faraday shield intercepts plasma sputtering toward the window 111, thus preventing window 111 erosion generally caused by plasma sputter. The Faraday shield also intercepts the heat flux generated by the etching process occurring in the chamber internal cavity 102. The integral configuration of the Faraday shield with the adapter plate 203 creates an efficient thermal conduction path to shunt heat away from the window 111. Hence, the window 111 temperatures are lowered, and the temperature gradient across the window surface is substantially decreased. Configuring the Faraday shield 201 to be inside the chamber internal cavity 102, below the window 111, and in direct exposure to the plasma serves to protect the window 111 from etching by-product deposition, plasma sputter induced erosion, and thermal stresses caused by large temperature gradients.
The Faraday shield 231 includes a surrounding ring 241 configured to mate with the channel 239 provided in the adapter plate 233. The o-ring 211 provides a vacuum seal between the window 111 and the surrounding ring 241. Similarly, an o-ring 235 provides a vacuum seal between the adapter plate 233 and the surrounding ring 241. The Faraday shield 231 and surrounding ring 241 are both electrically conductive and are grounded to the adapter plate 233 by an RF gasket 237. The Faraday shield 231 and surrounding ring 241 have the beneficial feature of being easy to access and remove from the adapter plate 233 for routine maintenance or replacement.
The Faraday shield 251 includes a surrounding insulating ring 255 configured to mate with the channel 257 provided in the adapter plate 253. The o-ring 211 provides a vacuum seal between the window 111 and the surrounding insulating ring 255. Similarly, an o-ring 258 provides a vacuum seal between the adapter plate 253 and the surrounding insulating ring 255. The Faraday shield 251 is electrically conductive and electrically isolated from the adapter plate 253 by the surrounding insulating ring 255. An electrical conductor 261 is connected to the Faraday shield 251 through an insulated penetration 259 in the bumper 207. A voltage can be applied to the electrical conductor 261 to electrically charge the Faraday shield 251. Some etching processes may benefit from the Faraday shield 251 being electrically charged. The Faraday shield 251 and surrounding insulating ring 255 have the beneficial feature of being easy to access and remove from the adapter plate 253 for routine maintenance or replacement.
The Faraday shield 271 includes a radial support body 275 contoured to be bottom-inserted within the adapter plate 273. The contour of the radial support body 275 mates with a complementary contour on the adapter plate 273. The o-ring 211 provides a vacuum seal between the window 111 and the radial support body 275. Similarly, an o-ring 277 and an o-ring 279 provide a vacuum seal between the adapter plate 273 and the radial support body 275. An o-ring 283 provides a vacuum seal between the bucket liner 215 and the radial support body 275. The Faraday shield 271 and the radial support body 275 are both electrically conductive and are grounded to the adapter plate 273 by an RF gasket 281. The radial support body 275 is further grounded to the bucket liner 215 by an RF gasket 285. The Faraday shield 271 and the radial support body 275 have the beneficial feature of being easy to access and remove from the adapter plate 273 for routine maintenance or replacement. Also, the adapter plate 273 can be removed from the etching apparatus without removing the Faraday shield 271 and the radial support body 275.
The Faraday shield 291 includes a radial support body 295 contoured to be top-inserted within the adapter plate 293. The contour of the radial support body 295 mates with a complementary contour on the adapter plate 293. The o-ring 211 provides a vacuum seal between the window 111 and the radial support body 295. Similarly, an o-ring 297 provides a vacuum seal between the adapter plate 293 and the radial support body 295. An o-ring 301 provides a vacuum seal between the bucket liner 215 and the adapter plate 293. The Faraday shield 291 and the radial support body 295 are both electrically conductive and are grounded to the adapter plate 293 by an RF gasket 299. Continuity of ground is also provided by an RF gasket 305 between the adapter plate 293 and the bucket liner 215. The Faraday shield 291 and the radial support body 295 have the beneficial feature of being easy to access and remove from the adapter plate 293 for routine maintenance or replacement. Also, the Faraday shield 291 and the radial support body 295 can be removed without removing the adapter plate 293.
The Faraday shield 311 is integral with the adapter plate liner 315. An o-ring 317 provides a vacuum seal between the Faraday shield 311 and adapter plate liner 315 combination and an adapter plate 313. The Faraday shield 311 and adapter plate liner 315 combination is electrically conductive and is grounded to the adapter plate 313 by an RF gasket 319. The Faraday shield 311 and adapter plate liner 315 combination has the beneficial feature of being easy to access and remove from the adapter plate 313 for routine maintenance or replacement.
For the example etching process considered in
For the example etching process considered in
While this invention has been described in terms of several embodiments, it will be appreciated that those skilled in the art upon reading the preceding specifications and studying the drawings will realize various alterations, additions, permutations and equivalents thereof. It is therefore intended that the present invention includes all such alterations, additions, permutations, and equivalents as fall within the true spirit and scope of the invention.
Claims
1. A method for making an inductively coupled plasma etching apparatus, comprising:
- providing a chamber having an interior cavity defined by a bottom and side walls, wherein each of the side walls has a top surface;
- placing a thermally conductive adapter plate to interface with the top surface of the side walls so as to form a seal between the thermally conductive adapter plate and the side walls, wherein the thermally conductive adapter plate is defined to have a central opening over the chamber interior cavity;
- placing a metal shield to cover the central opening of the thermally conductive adapter plate and establish a thermal connection between the metal shield and the thermally conductive adapter plate, whereby the metal shield is placed to be in direct exposure to the chamber interior cavity;
- placing a window above the metal shield and thermally conductive adapter plate so as to form a seal between the window and the thermally conductive adapter plate; and
- placing a coil above the window.
2. A method for making an inductively coupled plasma etching apparatus as recited in claim 1, wherein placing the window above the metal shield is performed such that a distance ranging from about 0.005 inch to about 0.04 inch exists between the metal shield and the window.
3. A method for making an inductively coupled plasma etching apparatus as recited in claim 1, further comprising:
- coating the metal shield.
4. A method for making an inductively coupled plasma etching apparatus as recited in claim 1, wherein placing the metal shield over the chamber interior cavity is performed such that the metal shield is electrically isolated from the chamber side walls.
5. A method for making an inductively coupled plasma etching apparatus as recited in claim 4, further comprising:
- applying an electric charge to the metal shield.
6. A method for making an inductively coupled plasma etching apparatus as recited in claim 1, wherein the metal shield is defined to include a plurality of slits configured to control a flow of electrical current through the metal shield.
7. A method for making an inductively coupled plasma etching apparatus as recited in claim 1, further comprising:
- placing a liner proximate to the thermally conductive adapter plate such that the liner is in direct exposure to the chamber interior cavity.
8. A method for making an inductively coupled plasma etching apparatus, comprising:
- providing a chamber defined by a bottom, side walls, and an upper heat dissipation structure, wherein the upper heat dissipation structure is defined to include an opening through which an interior cavity of the chamber is exposed;
- placing a thermally conductive metal shield in thermal communication with the upper heat dissipation structure so as to cover the opening within the heat dissipation structure, whereby the thermally conductive metal shield is directly exposed to the chamber interior cavity;
- placing a window above the thermally conductive metal shield so as to form a seal between the window and the upper heat dissipation structure around the thermally conductive metal shield; and
- placing a coil above the window.
9. A method for making an inductively coupled plasma etching apparatus as recited in claim 8, wherein placing the thermally conductive metal shield in thermal communication with the upper heat dissipation structure includes mating a surrounding support body of the thermally conductive metal shield with a complementary shaped portion of the upper heat dissipation structure.
10. A method for making an inductively coupled plasma etching apparatus as recited in claim 9, wherein the surrounding support body of the thermally conductive metal shield is defined as a ring, and the complementary shaped portion of the upper heat dissipation structure is defined as a channel.
11. A method for making an inductively coupled plasma etching apparatus as recited in claim 9, wherein the surrounding support body of the thermally conductive metal shield is defined to include an outer surface contoured to be inserted into and removed from the upper heat dissipation structure from a direction below the upper heat dissipation structure.
12. A method for making an inductively coupled plasma etching apparatus as recited in claim 9, wherein the surrounding support body of the thermally conductive metal shield is defined to include an outer surface contoured to be inserted into and removed from the upper heat dissipation structure from a direction above the upper heat dissipation structure.
13. A method for making an inductively coupled plasma etching apparatus as recited in claim 8, wherein the thermally conductive metal shield is defined to have a thickness ranging from about 0.03 inch to about 1 inch.
14. A method for making an inductively coupled plasma etching apparatus as recited in claim 8, wherein placing the window above the thermally conductive metal shield is performed such that a distance ranging from about 0.005 inch to about 0.04 inch exists between the thermally conductive metal shield and the window.
15. A method for making an inductively coupled plasma etching apparatus, comprising:
- providing a chamber defined by a bottom and side walls, wherein each of the side walls has a top surface;
- forming a chamber top to include a heat dissipation structure and a metal shield thermally integrated with the heat dissipation structure, wherein the heat dissipation structure defines a peripheral portion of the chamber top and the metal shield defines a central portion of the chamber top such that the metal shield is substantially planar with a top surface of the heat dissipation structure;
- placing the chamber top to interface with the top surface of the side walls so as to form a seal between the chamber top and the side walls;
- placing a window above the chamber top so as to form a seal between the window and the peripheral portion of the chamber top; and
- placing a coil above the window.
16. A method for making an inductively coupled plasma etching apparatus as recited in claim 15, wherein placing the window above the chamber top is performed such that a distance ranging from about 0.005 inch to about 0.04 inch exists between the metal shield and the window.
17. A method for making an inductively coupled plasma etching apparatus as recited in claim 15, wherein the metal shield is defined to include a plurality of slits configured to control a flow of electrical current through the metal shield.
18. A method for making an inductively coupled plasma etching apparatus as recited in claim 15, further comprising:
- placing a liner proximate to the heat dissipation structure such that the liner is in direct exposure to an interior cavity of the chamber.
19. A method for making an inductively coupled plasma etching apparatus as recited in claim 15, further comprising:
- coating the metal shield.
20. A method for making an inductively coupled plasma etching apparatus as recited in claim 15, wherein the metal shield is defined to have a thickness ranging from about 0.03 inch to about 1 inch.
Type: Application
Filed: Apr 4, 2007
Publication Date: Aug 9, 2007
Applicant: Lam Research Corporation (Fremont, CA)
Inventors: Keith Comendant (Fremont, CA), Robert Steger (Los Altos, CA)
Application Number: 11/696,327
International Classification: C23F 1/00 (20060101);