Patent Application
20050133166
1. Field of the Invention
The present invention generally relates to the fabrication of integrated circuits. More specifically, the invention relates to an apparatus for manufacturing a photomask, or “reticle,” useful in manufacturing semiconductors.
2. Description of the Related Art
Integrated circuits (IC) are manufactured by forming discrete semiconductor devices on a surface of a semiconductor substrate. An example of such a substrate is a silicon (Si) or silicon dioxide (SiO2) wafer. To interconnect the devices on the substrate, a multi-level network of interconnect structures is formed. Material is deposited on the substrate in layers and selectively removed in a series of controlled steps.
Increasing circuit densities have placed additional demands on processes used to fabricate semiconductor devices. For example, as circuit densities increase, the widths of vias, contacts and other features, as well as the dielectric materials between them, decrease to sub-micron dimensions. However, the thickness of the dielectric layers remains substantially constant, with the result that the aspect ratios for the features, i.e., their height divided by width, increases. Reliable formation of high aspect ratio features is important to the success of sub-micron technology and to the continued effort to increase circuit density and the quality of individual substrates and die.
Reliable formation of high aspect ratio features with desired critical dimensions requires precise patterning and subsequent etching of the substrate. A technique commonly used to form precise patterns on substrates is photolithography. The technique generally involves the direction of light energy through a lens, or “reticle” and onto the substrate. In conventional photolithographic processes, a photoresist material is first applied on a substrate layer to be etched. In the context of optical resists, the resist material is sensitive to light energy, such as ultraviolet or laser sources. The resist material defines a polymer that is tuned to respond to the specific wavelength of light used, and to different exposing sources.
After the resist is deposited onto the substrate, the light source is actuated to emit ultraviolet (UV) light or low X-ray light, for example, directed at the resist-covered substrate. The selected light source chemically alters the composition of the photoresist material. However, the photoresist layer is only selectively exposed. In this respect, a photomask, or “reticle,” is positioned between the light source and the substrate being processed. The photomask is patterned to contain the desired configuration of features for the substrate. The patterned photomask causes the light energy to strike the resist material in accordance with the pattern.
Photolithographic reticles are fabricated from an optically transparent material, such as quartz (i.e., silicon dioxide, SiO2). The reticle includes a pattern of opaque material that inhibits the light from exposing portions of the substrate in accordance with the desired pattern. A thin opaque layer of metal, typically chromium, is disposed on the surface of the reticle. This light-shielding layer is patterned to correspond to the features to be transferred to the substrate, such as transistors or polygates. The metallic material is patterned using conventional laser or electron beam patterning equipment to define the critical dimensions to be transferred to the metal layer. The metal layer is then etched to remove the metal material not protected by the patterned resist, thereby exposing the underlying quartz material and forming a patterned photomask layer. Photomask layers thus allow light to pass therethrough in a precise pattern onto the substrate surface.
In photolithography, the exposed material may either be a positive resist or a negative resist. In a positive resist, the exposed resist material on the substrate is removed, while in a negative resist, the unexposed portions are removed. Removal is typically by a chemical process to expose an underlying substrate material. The exposed underlying substrate material may then be etched to form patterned features in the substrate surface while the retained resist material remains as a protective coating for the unexposed underlying substrate material. In this manner, contacts, vias, or interconnects may be formed by exposing the resist to a pattern of light through a photolithographic reticle having a photomask layer disposed thereon.
In an iterative convergence, the method for fabricating a patterned reticle itself involves a deposition and subsequent etching process. In this respect, a metal layer is first deposited on a top surface of a glass reticle. Thereafter, selected portions of the metal layer are removed through etching. Various types of etching processes are used for etching the metal layer from a reticle. One such etching method is known as plasma etching. In order to perform plasma etching, a glass reticle is first placed within a process chamber. More specifically, the glass reticle is placed on a pedestal. In a plasma etching process, the pedestal serves as a cathode. To this end, the metallic pedestal is given RF power. Power applied to the pedestal creates a substrate bias in the form of a negative voltage on the upper surface of the reticle. This negative voltage is used to attract ions from a plasma formed above the reticle in the chamber. The plasma is formed by the application of power to one or more inductive coils at the top of the chamber. The inductive coils generate and sustain the plasma above the pedestal and reticle. Thus, a voltage drop is induced across the pedestal that draws ions to the upper surface of the reticle, thereby etching a metallic layer.
Because the reticle is formed from a material having a low dielectric constant, e.g., glass or quartz, the amount of RF power that is coupled through the reticle is low. This inhibits the gas plasma in reacting with the reticle surface. This limitation is compounded by a gap typically existing between the reticle and the supporting pedestal therebelow. In addition, when the surface area of the pedestal is large compared to the reticle area, the RF power may preferentially couple to other regions of the pedestal, producing a loss of RF power. Further, it has been observed that the use of a pedestal cover, e.g., cover ring and capture ring, fabricated from a dielectric material is inadequate to lessen the power coupled through the region of the pedestal that is not immediately below the reticle.
Therefore, there is a need for a plasma etching apparatus that aids in the chemical reaction between a gas plasma and a reticle. In addition, there is a need for a pedestal fabricated from a material that does not contribute to the power loss across the reticle during a plasma etching procedure.
The present invention generally provides an improved pedestal for supporting a substrate and related substrate support hardware. The pedestal has greatest application during a plasma etching process, such as for a quartz photomask, or “reticle.”
The pedestal defines a body, and a base along on an upper surface of the body. The body receives an RF power during substrate processing. The substrate support base has an outer edge, and an intermediate substrate support ridge for receiving and supporting the substrate. At least a portion of the substrate support base outside of the intermediate substrate support ridge is fabricated from a dielectric material, or material having a lower dielectric constant than the remaining support base. An example is quartz. Quartz has a lower dielectric constant than the materials typically used for fabricating the pedestal body or cover, e.g., alumina. The placement of quartz allows greater RF power to be coupled through the reticle, thereby enhancing the plasma etching process. It also provides greater control over the relative amount of RF power coupled through the reticle.
In one aspect, a layer of dielectric material is placed along the top of the support base of the pedestal body. In another embodiment, the entire cross-sectional thickness of the support base that encompasses the supporting ridge is fabricated from a dielectric material. In one embodiment, a separate substrate support assembly is disposed on the base to facilitate the transfer of the substrate onto and off of the pedestal, with the substrate support assembly being fabricated from a dielectric material.
So that the manner in which the above recited features 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 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.
Aspects of the invention will be described below in reference to an inductively coupled plasma etch chamber. Suitable inductively coupled plasma etch chambers include the Decoupled Plasma Source (DPS™) chamber available from Applied Materials, Inc., of Santa Clara, Calif., or the ETEC Tetra™ photomask etch chamber available from ETEC of Hayward, Calif. A two-coil chamber, such as the Tetra II™ decoupled plasma source chamber available from Applied Materials, Inc. may also be employed. Other process chambers may be used including, for example, capacitively coupled parallel plate chambers and magnetically enhanced ion etch chambers, as well as inductively coupled plasma etch chambers of different designs. Although the processes are advantageously performed with the DPS™ processing chamber, the description in conjunction with the DPS™ processing chamber is illustrative and should not be construed or interpreted to limit the scope of aspects of the invention.
In order to perform plasma etching, a substrate, e.g., a glass reticle, is placed within a processing chamber. An example of such a chamber is schematically shown in
The processing chamber 100 is configured to receive a substrate 222, such as a glass reticle to be processed through plasma etching. The substrate 222 enters and exits the chamber 100 through a gate 161. The gate 161 serves as a port, and also isolates the chamber 100 environment during reticle processing. The substrate 222 is transported via a substrate cassette, using the substrate handling blade 300. The substrate handling blade 300 transfers the substrate 222 between a separate transfer chamber (not shown) and various processing chambers. In this respect, it is understood that the reticle fabrication process involves multiple steps, and that different steps are typically conducted in different chambers that mechanically cooperate with the substrate handling blade 300. An example of such a processing system is a Centura™ processing system available from Applied Materials, Inc. of Santa Clara, Calif.
The process chamber 100 generally includes a cylindrical side wall 162. The side wall 162 helps define the chamber body, and also supports the gate 161. The chamber 100 is also defined by a chamber bottom 167, and an energy transparent ceiling or lid 163. An inductive coil 176 is disposed around at least a portion of the lid 163. The chamber body 162 and chamber bottom 167 of the chamber 100 can be made from a metal, such as anodized aluminum. The lid 163 is fabricated from an energy transparent material such as a ceramic or other dielectric material.
As mentioned above, the chamber 100 holds a substrate support member 200. The support member 200 supports the substrate 222 during processing. A plasma zone 164 is defined by the process chamber 100 above an upper surface of the substrate support member 200. During processing, process gases are introduced into the plasma etch chamber 100 through a gas distributor 172. The gas distributor 172 is peripherally disposed about the substrate support member 200. The gas distributor 172 is shown illustratively, and may be disposed in other configurations, such as disposed at the top of lid 163. Process gases and etchant byproducts may be exhausted from the process chamber 100 through an exhaust system (not shown). An optional cooling line 184 is provided in the pedestal 200. for controlling the pressure in the plasma etch chamber 100. An endpoint measurement device may optionally be included to determine the endpoint of a process performed in the chamber 100.
With respect to the substrate support member 200 itself, the support member 200 defines a pedestal for the substrate 222 during processing. The support member 200 first comprises a body 206. The body 206 has an upper surface that defines a substrate support base 210 (seen in
Referring back to
Channels 211 (three are shown) are also disposed through the body 206, and house internally movable lift pins 214 therein. As will be discussed further below, the lift pins 214 engage the lower surface of a capture ring 220 to move the capture ring 220 vertically within the chamber 100 relative to the cover ring 216. The body 206 may comprise a temperature controlled base adapted to regulate the temperature of the substrate support assembly 215, and thus, a substrate 222 disposed thereon. The body 206 can be made of a material inert to the process formed in the processing chamber including, for example, aluminum oxide, or aluminum, and substrate support assembly 215 components can be made of aluminum or aluminum oxide. The body 206 may include fluid channels, heating elements, e.g., resistive heating elements or other temperature control members.
In the support member arrangement of
Referring first to the cover ring 216, the cover ring 216 is preferably a circular ring having an upper surface 219 and support shoulders 218. The substrate supports 218 define shoulders for receiving a substrate (not shown). In one arrangement, the substrate supports 218 define opposing raised surfaces 221, 223 that each includes an inner sloped surface for receiving a substrate. A central opening 225 is formed in the upper surface 219 of the cover ring 216. The two raised surfaces 221, 223 are generally disposed on opposing sides of the central opening 225. The first raised surface 221 defines an essentially linear raised surface extending along the length of one side of the central opening 225. The second raised surface 223 defines an arcuate raised surface 221 having an outer diameter 224 and an inner diameter 226. The outer diameter 224 generally matches the radius of the cover ring 216, while the inner diameter 226 conforms to the geometry of the central bore 225 along one or more sides of the bore 225. The upper surface 219 and the raised surfaces 221, 223 may be monolithic or may be made of separate components connected together.
The capture ring 220 defines an arcuate base plate having an inner diameter 207 and an outer diameter 202. A central bore 206 is formed within the inner diameter 207 of the capture ring 220. The diameters 207, 202 of the capture ring 220 are not continuous, but retain an opening that serves as part of the bore 206. As with the cover ring 216, the capture ring 220 includes substrate supports 204, 205. The substrate supports 204, 205 generally follow the inner diameter 207 of the capture ring 220. In the arrangement of
The capture ring 220 moves vertically above the cover ring 216. In operation, the lift pins 214 move the capture ring 220 vertically above the cover ring 216 during substrate transfer, and then lower the capture ring 220 onto the cover ring 216 for substrate processing. The use of lift pins in the semiconductor fabrication business is known, and those of ordinary skill in the art will understand from this disclosure how the lift pins may be fabricated.
Channels 217 are formed through the cover ring 216 to enable the lift pins 214 disposed through the body 206 to move therethrough and lift the capture ring 220 vertically. The vertical movement imparted by the lift pins 214 is used to lift the capture ring 220 to effectuate substrate transfer between the substrate handler blade 300 and the capture ring 220. The lift pins 214 move the capture ring 220 vertically above the cover ring 216 during substrate transfer, and then lower the capture ring 220 onto the cover ring 216 for substrate processing.
To begin processing, the reticle 222 (or other substrate) is positioned on the surface of the pedestal 200. Etch gases are then introduced into the chamber 100. To this end, a process gas source supplies gas, such as an oxygen based gas, through a gas input line 172. In the arrangement of
As gas is injected into the chamber 100, a gas plasma is created. Plasma is formed by the application of power to one or more inductive coils 176 at the top of the lid 163. In the chamber 100 of
The pedestal first comprises a body 306. In the arrangement of
The support base 310 is typically configured to receive a cover (not shown) to further support a reticle during processing. The cover may be configured to operate as the substrate support assembly 215 described above.
In the novel pedestal 300 of the present invention, at least a portion of the body 306 is fabricated from a dielectric material. In the cutaway view of
The dielectric material portion 318 of the body 306 may be of different thicknesses. This is demonstrated in the schematic embodiments shown in
Dielectric material is shown at 318 in both
As can be seen, the pedestals 300, 300′, 300″ place dielectric material along a periphery of the upper substrate support body 306. The dielectric material 318 may be polymeric or ceramic. An example of a polymeric material is Ardel™ polyarylate material manufactured by Amoco polymers. Another example is Vespel™ polyimide from DuPont. Still another example is a plastic material sold under the trade name Ultem™. Yet another example is a synthetic rubber material. An example of a suitable ceramic material is aluminum oxide. Another example of an acceptable dielectric material is quartz. The selected use of dielectric material 318 has the effect of changing the amount of RF power coupling into the reticle during a plasma etching procedure. In this respect, during a plasma etching procedure, the body 306 receives power, such as an RF power. By using dielectric material on the periphery of the body, the potential drop across the pedestal is changed to have a value less than the region where the reticle rests, i.e., inside of the substrate support ridge 326. The portion of the pedestal 300 within the substrate support ridge 326 remains metallic in order to efficiently conduct waste heat away from the reticle 222.
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.
The present application claims priority to previously filed provisional patent application Ser. No. 60/531,062, filed Dec. 19, 2003, entitled “Tuned Potential Pedestal for Mask Etch Processing Apparatus.” The provisional application is incorporated herein by referenced in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60531062 | Dec 2003 | US |
