Patent Application
20080190364
Embodiments of the present invention relate to a substrate support assembly for supporting a substrate in a process chamber.
In the manufacture of electronic circuits such as, for example, integrated circuits and displays, a substrate is placed in a process chamber and a process gas is introduced into the chamber to process the substrate. The process chamber generally comprises an enclosure wall surrounding a substrate processing zone. A gas energizer can be used to energize the process gas by applying RF or microwave energy to the gas. The process gas is energized to etch features in layers on the substrate or to deposit layers on the substrate.
In the process chamber, the substrate is held on a substrate receiving surface of a substrate support. The substrate support can have an electrode that can be charged to electrostatically hold the substrate. The electrode can also be electrically charged or maintained at a ground potential to serve as a gas energizer, by an electrical connector that passes through the body of the support. Thermocouples can also be passed through the support to allow more accurate measurement of substrate temperatures. The support can also have a heater with electrical connectors to heat the substrate during processing. Thus the support typically has a plurality of electrical conductors, such as the electrical connectors, thermocouples, and other conducting structures extending therethrough to power the electrode, heater, and other devices, or to transfer sensory information.
During processing, energized halogen-containing gases and oxygen-containing gases are used to process the substrate or clean chamber surfaces. In both deposition and etch processes, fluorine-containing and chlorine-containing gases, are used to deposit or etch material from the substrate. Energized cleaning gases that contain fluorine-containing gases such as CF4 or NF3 are also periodically used to remove accumulated process residues from the chamber surfaces. However, the energized gases often corrode and cause failure of the substrate support assembly. For example, such gases can erode external portions of the support to cause glow discharges between the plasma and the conductors in the support. Electrical arcing can also occur when such gases erode and damage joints between electrical connectors in the support. The RF electrical potential applied to the electrode to energize the gases in the chamber can also cause glow discharges or micro-arcing which damage or “burn” connectors and adjacent portions of the support. In some plasma environments, degradation of the substrate support assembly and its conductor components can require their refurbishment or replacement after processing of only a relatively small number of substrates, which increases fabrication costs per substrate.
Thus it is desirable to have a substrate support assembly that can withstand an erosive plasma environment. It is desirable to have a substrate support that exhibits reduced electrical arcing or glow discharges. Also, it is desirable to have a substrate support that allows processing of a large number of substrates without frequent replacement or repair. It is further desirable to be able to easily refurbish or clean a substrate support and its components.
These features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings which illustrate examples of the invention. However, it is to be understood that each of the features can be used in the invention in general, not merely in the context of the particular drawings, and the invention includes any combination of these features, where:
A substrate support assembly 100 comprises a support block 104 having a substrate receiving surface 106 to support a substrate 110 in a process chamber 112, as shown in
The support block 104 comprises an electrode 114 that is adapted to act as a part of a gas energizer 120 to energize a process gas provided in the chamber 112 to process the substrate 110. The electrode 114 may also optionally be chargeable to electrostatically hold the substrate 110 onto the substrate receiving surface 106 of the substrate support assembly 100. In one version, the electrode 114 is at least partially covered by, or embedded in a dielectric block 116. The embedded electrode 114 comprises a shape that is suitable to provide the desired electrical field characteristics across the substrate 110. For example, the embedded electrode 114 can comprise a mesh electrode or an electrode plate that is embedded in the dielectric block 116. The embedded electrode 114 is formed of a suitable conducting material, such as for example molybdenum. However, the electrode 114 can also be the support block 104 itself, for example, when the support block is a block of metal.
The support block 104 can also be adapted to control the temperature of the substrate 110. For example, the support block 104 can have heat transfer fluid conduits formed therein (not shown) to provide temperature control of a substrate 110 being supported thereon. The substrate receiving surface 106 can also have a plurality of raised mesas (not shown) that provide a more uniform distribution of heat across the substrate receiving surface 106 to control the temperature of the substrate 110.
The substrate support assembly 100 further comprises a support arm 124 that is shaped to securely hold the support block 104 in the middle of a process zone 126 in the chamber 112, and about an exhaust port 152 located in the bottom wall 154 of the process chamber 112. The support arm 124 comprises a support beam 160 that extends between the first and second ends 136, 148. The support arm 124 secures the support block 104 by providing a first clamp 128 that connects to the support block 104 and a second clamp 132 that connects to a portion of the chamber wall 134.
In the version shown, the first clamp 128 is substantially disk-shaped and comprises an inverted hollow cup 170 that is integrally connected to the arm 124. The first clamp 128 provides a flat surface that is attached to the center 140 of a lower surface 144 of the support block 104. The hollow cup 170 can serve as a protective enclosure for bolts, electrical connectors, electrical insulators and other connective or protective components of the support assembly 100.
The second clamp 132 is mounted at the second end 148 of the support arm 124 and attached to the chamber component of the chamber which can be for example, movable bellows 145 which are used to raise and lower the substrate support assembly 100 in the chamber 112, a chamber wall 134, or other chamber component. The clamps 128,132 are connected to the support block 104 and portions of the process chamber 112 or components of the chamber by screwing, bolting, brazing, or other suitable method. The support beam 160 is composed of a material that is resistant to corrosion by energized gas to provide a secure and corrosion resistant support structure. For example, the support beam 160 can comprise a ceramic material such as at least one of aluminum nitride, aluminum oxide and silicon oxide.
The support beam 160 has a channel 164 therethrough that is sized and shaped to receive a plurality of electrical conductors 168 that can include electrical connectors such as, for example, an electrical ground connector strap 230, one or more thermocouples 250 or other electrical connectors. The channel 164 extends along at least a portion of the support arm 124 to house the conductors 168, for example, the channel 164 may extend along substantially the entire length of the support beam 160 between the two ends 136, 148. The electrical conductors 168 are routed or passed though the channel 164 to guide the conductors 168 from the support block 104 to power supplies, process monitors and other chamber components which are external to the substrate support assembly 100 or even the chamber 112. The hollow support arm 124 shields and protects the electrical conductors 168 from the energized plasma species in the chamber 112.
A brazed bond 200a,b is used to electrically join at least one of the electrical conductors 168 to other components in the support block 104. For example, an electrical conductor 168 comprising a ground connector strap 230 can be connected to the electrode 114 in the support block 104. The brazed bond 200a,b is formed by first placing a brazing compound or brazing foil between the electrical conductor 168 and the other component at the join area, then heating the join area above the melting point of the braze material and finally cooling the join area to form a brazed bond 200a,b. The brazing compound or foil can comprise one or more of gold, silver, aluminum, copper, bronze or nickel alloys and more typically comprises a nickel alloy material. The surface wetting area of the brazed bond 200a,b between the electrical conductor 168 and the electrode 114 of the support block 104 is determined in part by the diameter of the electrical connectors 168. As the diameter of the electrical conductor 168 becomes larger more brazing material is used in the brazed bond 200a,b. The additional brazed material reduces, but does not prevent, erosion of the brazed bond 200a,b by the plasma and process gases in the process zone of the chamber.
In one version, a cover lock 180 is used to further reduce the erosion problem of the brazed bonds 200a,b. The cover lock 180 is positioned inside the hollow cup 170 with surrounding walls 174 which is at the first end 136 of the support arm 124. The cup 170 and cover lock 180 form an enclosure and protect the electrical conductors 168 and the electrical connection joints from erosion in the chamber plasma environment. In the embodiment shown in
The annular disc 182 of the cover lock 180 comprises a perimeter 184, center 188, and a U-shaped channel 188 extending radially from the perimeter 184 to the center 188 to allow passage of the electrical conductors 168 therethrough. The channel 188 comprises an elongated U-shaped aperture 190 with a curved base that allows the electrical conductors 168 to rotate from a horizontal alignment in the channel 164 of the support arm 124 to a vertical alignment as they pass through the cover lock 180 to the support block 104. In one version, the U-shaped channel 188 comprises a width of from about 2 mm to about 10 mm, for example, about 5 mm. The diameter of the U-shaped channel 188 is sufficient to pass the electrical connectors 168 therethrough.
An upper surface 192 of the annular disc 182 of the cover lock 180 comprises a plurality of U-shaped cut-outs 194 to provide space for the heads of bolts 196 that hold the support block 104 to the support arm 124. In one version the U-shaped cut-outs 194 in the upper surface 192 of the cover lock 180 are spaced apart at an angle of 120°. The hollow cup 170 in the first end 138 also has fastener holes for the shank of bolts 196 to pass through to hold the support block 104 to the support arm 124. Each fastener hole has an inundated ledge to provide a support surface for the head of the bolt 196 and allow it to be partially countersunk. The hollow cup 170 also comprises a shaped hole for passage of the electrical conductors 168, such as an electrical ground connector strap 230 that is connected at one end to the electrodes 114 within the support block 104 and passage of a thermocouple 250 for insertion into the back side of the support block 104. The shaped hole can also accommodate a spacer 198 to separate the thermocouple 250 from the electrical ground connector strap 230.
In one version, the cover lock 180 protects the brazed joint and electrical conductors 168 from erosion by serving as a sacrificial material that reacts with and consequently depletes the concentration of the plasma species about the conductors 168. For example, the cover lock 180 can comprise silicon. The silicon material reacts with halogen-containing plasma species, such as fluorine-containing species, to form silicon fluoride gases. The fluorine-containing gasses are used in etching processes or chamber cleaning processes. Fluorine and fluorine radicals are particularly reactive to brazed bonds 200a-b that are formed with nickel-containing brazing material. Erosion of the brazing material is undesirable because the impedance of the electrical connection formed by the bond 200a,b increases with erosion of the brazing material and can even result in arcing at the damaged brazed bond 200a,b when the bond 200a,b is sufficiently chemically eroded or corroded.
The cover lock 180 can be composed of quartz, which is a crystalline form of silicon oxide, or even pure elemental silicon such as, for example, single-crystal silicon. Single-crystal silicon is optimal because of the reaction of Si with fluorine to form SiF4, thereby depleting the fluorine left to react with the brazing material that makes up the brazed bond 200a,b.
In one version, the annular disc 182 of the cover lock 180 has a bottom surface 202 with a peripheral groove 204a which is used to fit a sealing ring 210 as shown in
The support arm 124 is held upside down during assembly and the various components, such as the electrical conductors 168, bolts 196 and the like are inserted into the cup 170 and attached to the support block 104. The cover lock and ring 210 are then inserted, and the retaining plate 220 is slid into the support arm 124, covering the underside of the cover lock 180 and ring 210. When the support arm 124 is turned the right way up, the sealing ring 210 drops into the indentation 204a of the lower retaining plate 220. This joins the cover lock 180 and the retaining plate 220 and prevents the retaining plate 220 from sliding out of the support arm 124 during use or installation. In one version, the sealing ring 210 comprises a C-shaped clamp 214 made from a ceramic material, such as aluminum oxide. The C-shaped clamp 214 comprises an opening 218 that is aligned with the U-shaped channel 188 in the annular disc 182. The aluminum oxide material is desirable because it is inert to the reactant gasses, fluorine radicals and plasma environment that can be present in the chamber.
In use, the support arm 124 is used to hold electrical conductors 168 such as an electrical ground connector strap 230 that is passed through the channel 164 of the hollow support arm 124. The connector strap 230 electrically grounds portions of the support block 104, such as the electrode 114, while another electrode 236, such as a wall of the chamber 112 is electrically biased so that a process gas provided in the chamber 112 can be energized to form energized gas, such as plasma. The connector strap 230 can also remove excess electrical charge from portions of the support block 104 to facilitate removal of the substrate 110 from the substrate receiving surface 106 after processing. The connector strap 230 comprises a first terminal 240 that is electrically connected to the electrode 114 (as shown) or the support block 104 itself when the support block functions as an electrode, and a second terminal 244 that is electrically connected outside the process chamber 112 to “ground” the electrode 114 or maintain the electrode 114 at about the same potential as the process chamber 112. The second terminal 244 can also be connected to a bottom wall 154 of the chamber 112. The electrical ground connector strap 230 desirably comprises an electrically conductive material, such as for example one or more of stainless steel, nickel, molybdenum, aluminum, hastelloy, and alloys thereof.
The first terminal 240 of the connector strap 230 can be electrically connected to the electrode 114 by, for example, braze joining the first terminal 240 to the electrode 114. The electrical connection can also be formed through an intermediary lug 128. A cylindrical bore 122 is machined into the bottom surface of the support block 104 and to the electrode 114. The lug 128 is then embedded into the cylindrical bore 122 and is braze-bonded to the electrode 114 and to the inner surface of the cylindrical bore 122 with a braze bond 200a. In the version shown in
The support arm 124 can also hold an electrical conductor 168 comprising a thermocouple 250 that is passed through the channel 164 of the hollow support arm 124 and also positioned near the ground connector strap 230.
In one version, the substrate support assembly 100 further comprises a ceramic insulator 223 positioned in between the electrical ground connector strap 230 and the thermocouple 250 in the channel of the support arm 124. The ceramic insulator 223 is provided in order to reduce the occurrence of electrical arcing between the ground connector strap 230 and thermocouple 250, thereby increasing the part life of the substrate support assembly 100. The ceramic insulator may comprise one of more of aluminum nitride, aluminum oxide, zirconium oxide, silicon oxide, silicon carbide, mullite and silicon nitride. The ceramic insulator 223 also desirably comprises a thickness suitable to electrically shield the thermocouple 250 and ground connector strap 230, such as a thickness of about 0.5 cm.
To facilitate the arrangement of the ground connector strap 230 and thermocouple 250 near one another, and to reduce manufacturing costs, the channel 164 can be formed having differently sized upper and lower grooves 217, 219. In one version, the ground connector strap 230 is positioned above the thermocouple 250 in an upper groove 217 and the thermocouple 250 is positioned below the ground connector strap 230 in a lower groove 219. In the version shown in
The above-described configuration of the substrate support assembly 100 having the cover lock 180 about the ground connector strap 230 and thermocouple 250 has been discovered to provide good resistance to corrosion in the process chamber 112 by reducing the erosion rate of the brazed bonds 200 between the electrical conductors 168 and the support block 104, hence reducing the occurrence of electrical arcing between the ground connector strap 230 and the electrodes 114 of the support block 104 during processing of substrates 110 in the chamber 112. The use of the cover lock 180 also preserves the ease of assembly of the substrate support assembly 100, as the ground connector strap 230 and thermocouple 250 may be easily routed through the same channel 164. Thus, the substrate support assembly 100 having the cover lock 180 provides an improved corrosion resistant support component for the processing of substrates 110 in the process chamber 112.
The substrate support assembly 100 also allows for refurbishing of the assembly 100 to provide a longer processing lifetime. The refurbishing process may allow for the cleaning of parts such as the support block 104 and support arm 124 to remove process residues, as well as the replacement of any corroded assembly parts, such as portions of the support block 104. As the cover lock 180 inhibits electrical arcing and reduces corrosion of the ground connector strap 230, the refurbishing process may also be performed without requiring replacement of the ground connector strap 230.
To refurbish the substrate support assembly 100, one or more of the thermocouple 250 and metal plate are removed from the support block 104. A cleaning process is then performed to clean process residues from one or more of the support block 104 and support arm 124. The cleaning process can comprise, for example, immersing the support block 104 and support arm 124 in a cleaning solution comprising acidic or basic species, such as for example HF or KOH, as described for example in U.S. application Ser. No. 10/032,387, Attorney Docket No. 6770, to He et al, filed on Dec. 21, 2001, assigned to Applied Materials, and U.S. application Ser. No. 10/304,535, Attorney Docket No. 8061, to Wang et al, filed on Nov. 25, 2002, and assigned to Applied Materials, which are herein incorporated by reference in their entireties. The cleaning solution removes any process residues and also can remove any loose grains from the dielectric block 116 and support arm 124 which could otherwise contaminate the substrate 110 during processing. A grit blasting process can also be performed to clean and refurbish the support block 104 and support arm 124, as described in the above-referenced applications. After the cleaning process has been performed, the same or a fresh thermocouple 250 is arranged adjacent to the support block 104, for example by brazing a tip of the thermocouple to the lower surface 144 of the support block 104. The thermocouple 250 and ground connector strap 230 are re-routed through the channel of the support arm 124, and the cover lock 180 is placed therebetween.
An apparatus 102 suitable for processing a substrate 110 with the substrate support assembly 100 comprising the hollow support arm 124 with the cover lock 180 comprises a process chamber 112, as shown in
The apparatus 102 may be attached to a mainframe unit (not shown) that contains and provides electrical, plumbing, and other support functions for the apparatus 102 and may be part of a multichamber system (not shown). The multichamber system has the capability to transfer a substrate 110 between its chambers without breaking the vacuum and without exposing the substrate 110 to moisture or other contaminants outside the multichamber system. An advantage of the multichamber system is that different chambers in the multichamber system may be used for different purposes in the entire process. For example, one chamber may be used for etching a substrate 110, another for the deposition of a metal film, another may be used for rapid thermal processing, and yet another may be used for depositing an anti-reflective layer. The process may proceed uninterrupted within the multichamber system, thereby preventing contamination of substrates 104 that may otherwise occur when transferring substrates 104 between various separate individual chambers for different parts of a process.
Generally, the process chamber 112 comprises a wall 107, such as an enclosure wall 103, which may comprise a ceiling 118, sidewalls 115, and a bottom wall 117 which enclose a process zone 108. In operation, process gas is introduced into the chamber 112 through a gas supply 130 that includes a process gas source 138, and a gas distributor 137. The gas distributor 137 may comprise one or more conduits 139 having one or more gas flow valves 133 and one or more gas outlets 142 around a periphery of the substrate 110 which is held in the process zone 108 on the substrate support assembly 100 having the substrate receiving surface 106. Alternatively, the gas distributor 137 may comprise a showerhead gas distributor (not shown). Spent process gas and etchant byproducts are exhausted from the chamber 112 through an exhaust 146 which may include a pumping channel that receives spent process gas from the process zone via the exhaust port 152, a throttle valve 135 to control the pressure of process gas in the chamber 112, and one or more exhaust pumps 153.
The process gas may be energized to process the substrate 110 by a gas energizer 120 that couples energy to the process gas in the process zone 108 of the chamber 112. In the version shown in
To process a substrate 110, the process chamber 112 is evacuated and maintained at a predetermined sub-atmospheric pressure. The substrate 110 is then provided on the substrate receiving surface 106 of the substrate support assembly by a substrate transport 101, such as a robot arm and a lift pin system. The gas energizer 120 then energizes a gas to provide an energized gas in the process zone 108 to process the substrate 110 by coupling RF or microwave energy to the gas. A bellows structure (not shown) can raise or lower the substrate support assembly 100 to provide the desired plasma processing characteristics.
Although exemplary embodiments of the present invention are shown and described, those of ordinary skill in the art may devise other embodiments which incorporate the present invention, and which are also within the scope of the present invention. For example, other support arm structures and shapes other than those specifically mentioned may be used. Also, the positions of the ground connector strap 230 and thermocouple 250 in the support arm 124 can be reversed, or they can be positioned side-by-side, as would be apparent to those of ordinary skill in the art. Furthermore, the terms below, above, bottom, top, up, down, first and second and other relative or positional terms are shown with respect to the exemplary embodiments in the figures and are interchangeable. Therefore, the appended claims should not be limited to the descriptions of the preferred versions, materials, or spatial arrangements described herein to illustrate the invention.
