Patent Application
20180340257
This application claims benefit to Indian Provisional Patent Application No. 201741018368, filed May 25, 2017, the entirety of which is herein incorporated by reference.
Embodiments of the present disclosure generally relate to a plasma enhanced chemical vapor deposition (PECVD) diffuser.
Flat panel displays are commonly used for active matrix displays such as computer and television monitors. PECVD is generally employed to deposit thin films on a substrate, such as a transparent substrate for flat panel display implementations. PECVD is generally accomplished by introducing a precursor gas or gas mixture into a vacuum chamber that contains a substrate. The precursor gas or gas mixture is typically directed toward the substrate through a distribution plate situated near a top of the chamber opposite the substrate. The precursor gas or gas mixture in the chamber is energized (e.g., excited) into a plasma by applying radio frequency (RF) power to the chamber from one or more RF sources coupled to the chamber. The excited gas or gas mixture reacts to form a layer of material on a surface of the substrate.
Flat panels processed by PECVD techniques are typically large, often exceeding several square meters. Gas distribution plates (or gas diffuser plates) utilized to provide uniform process gas flow over flat panels are relatively large in size, particularly as compared to gas distribution plates utilized for 200 mm and 300 mm semiconductor wafer processing. Further, as the substrates are rectangular, edges of the substrate, such as sides and corners thereof, experience conditions that may be different than the conditions experienced at other portions of the substrate. These different conditions affect processing parameters such as film thickness, deposition uniformity, and/or film stress.
As the size of substrates continues to grow in the flat panel display industry, film thickness and film uniformity control for large area PECVD becomes an issue. The difference of deposition rate and/or film property, such as film thickness or stress, between the center and the edges of the substrate becomes significant and may result in displays with suboptimal characteristics.
Therefore, what is needed in the art are improved gas distribution plate assemblies.
In one embodiment, a gas diffuser apparatus is provided. The apparatus includes a first plate having a first bore formed therein and a second plate having an orifice hole formed therein. The second plate is brazed to the first plate. The apparatus further includes a third plate having a second bore formed therein and the second plate is brazed to the third plate. A diameter of the orifice hole is less than a diameter of the first bore and a diameter of the second bore and the orifice hole is substantially aligned with a center of the first bore and a center of the second bore.
In another embodiment, a substrate process apparatus is provided. The apparatus includes chamber walls, a bottom coupled to the chamber walls, a backing plate coupled to the chamber walls opposite the bottom, and a diffuser coupled to the backing plate opposite the bottom. The diffuser includes a first plate having a first bore formed therein and a second plate having an orifice hole formed therein. The second plate is brazed to the first plate. The apparatus further includes a third plate having a second bore formed therein and the second plate is brazed to the third plate. A diameter of the orifice hole is less than a diameter of the first bore and a diameter of the second bore and the orifice hole is substantially aligned with a center of the first bore and a center of the second bore.
In yet another embodiment, a gas diffuser apparatus is provided. The apparatus includes a first aluminum plate having a first bore formed therein and a diameter of the first bore is constant alone a depth of the first bore. A second aluminum plate is brazed to the first aluminum plate, the second aluminum plate has an orifice hole formed therein, and a diameter of the orifice hole is constant along a depth of the orifice hole. A third aluminum plate is brazed to the second aluminum plate, the second aluminum plate has a second bore formed therein, and a diameter of the second bore increases along a depth of the second bore from a first surface of the third aluminum plate adjacent to the second aluminum plate to a second surface of the third aluminum plate opposite the first surface.
So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, 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 exemplary embodiments and are therefore not to be considered limiting of its scope, may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
Embodiments described herein relate to a PECVD chamber and diffuser assembly for processing large area flat panel display substrates. The diffuser includes a first plate having a plurality of first bores formed therein, a second plate having a second plurality of bores formed therein, and a third plate having a third plurality of bores formed therein. The second plate is disposed between the first plate and the second plate. The first plate, second plate, and third plate are brazed to form a diffuser having a unitary body.
Embodiments described herein provide for a diffuser assembly which enables substantially uniform deposition on a substrate. In operation, the diffuser assembly can compensate for non-uniformities corresponding to various regions of the substrate. According to embodiments described herein, the diffuser assembly compensates for the non-uniformities by adjusting flow of gases through the plates comprising the diffuser assembly in areas where deposition is non-uniform. In one embodiment, a local gas flow gradient within one or more portions of the diffuser assembly may be modulated to provide a greater flow rate though portions of the diffuser assembly relative to other portions of the diffuser assembly in order to compensate for non-uniformities. In one aspect, an orifice of a gas passage can be sized to improve maintenance of plasma generation through the diffuser assembly. The orifice size can be varied to form a gradient of orifice diameters or a mixture of diameters that result in substantially uniform deposition.
Embodiments herein are illustratively described below in reference to a PECVD system configured to process large area substrates, such as a PECVD system, available from AKT, a division of Applied Materials, Inc., Santa Clara, Calif. It is contemplated that other suitably configured apparatus from other manufacturers may also be implemented according to the embodiments described herein. In addition, it should be understood that various implementations described herein have utility in other system configurations, such as etch systems, other chemical vapor deposition systems, or other systems in which distributing gas within a process chamber is desired, including those systems configured to process round substrates.
The substrate support 130 includes a substrate receiving surface 132 for supporting a substrate 105 and a stem 134 coupled to a lift system 136 to raise and lower the substrate support 130. In operation, a shadow frame 133 may be positioned over a periphery of the substrate 105 during processing. Lift pins 138 are moveably disposed through the substrate support 130 to move the substrate 105 to and from the substrate receiving surface 132 to facilitate substrate transfer. The substrate support 130 may also include heating and/or cooling elements 139 to maintain the substrate support 130 and substrate 105 positioned thereon at a desired temperature. The substrate support 130 may also include grounding straps 131 to provide RF grounding at a periphery of the substrate support 130.
The diffuser 110 is coupled to a backing plate 112 adjacent a periphery of the diffuser 110 by a suspension element 114. The diffuser 110 may also be coupled to the backing plate 112 by one or more center supports 116 to help prevent sag and/or control the straightness/curvature of the diffuser 110. A gas source 120 is fluidly coupled to the backing plate 112 to provide gas through the backing plate 112 to a plurality of gas passages 111 formed in the diffuser 110 and ultimately to the substrate receiving surface 132.
A vacuum pump 109 is coupled to the chamber 100 to control the pressure within the process volume 106. An RF power source 122 is coupled to the backing plate 112 and/or to the diffuser 110 to provide RF power to the diffuser 110 to generate an electric field between the diffuser 110 and the substrate support 130. In operation, gases present between the diffuser 110 and the substrate support 130 are energized by the RF electric field into a plasma. Various RF frequencies may be used, such as a frequency between about 0.3 MHz and about 200 MHz. In one embodiment, the RF power source 122 provides power to the diffuser 110 at a frequency of 13.56 MHz.
A remote plasma source 124 is also coupled between the gas source 120 and the backing plate 112. The remote plasma source 124 may be an inductively coupled remote plasma source, a capacitively coupled remote plasma source, or a microwave remote plasma source, depending upon the desired implementation. The remote plasma source 124 may be utilized to assist in process gas plasma generation and/or cleaning gas plasma generation.
In one embodiment, the heating and/or cooling elements 139 embedded in the substrate support 130 are utilized to maintain the temperature of the substrate support 130 and substrate 105 thereon during deposition of less than about 400 degrees Celsius or less. In one embodiment, the heating and/or cooling elements 139 are used to control the substrate temperature to less than 100 degrees Celsius, such as between 20 degrees Celsius and about 90 degrees Celsius.
Spacing between a top surface of the substrate 105 disposed on the substrate receiving surface 132 and a bottom surface 140 of the diffuser 110 during deposition processes may be between 400 mil and about 1,200 mil, for example between 400 mil and about 800 mil. In one embodiment, the bottom surface 140 of the diffuser 110 may include a concave curvature wherein the center region is thinner than a peripheral region thereof (See
Each of the first plate 202 and the third plate 206 may be coupled to the second plate 204 such that the second plate 204 is disposed between the first plate 202 and the third plate 206. The first plate 202 and third plate 206 may be brazed to the second plate 204. For example, the first plate 202, the second plate 204, and the third plate 206 may be subjected to a vacuum brazing process to bond the three plates into a unitary body comprising the diffuser 110. A thickness 220 of the unitary body of the diffuser may be between about 0.50 inches and about 3.00 inches, such as between about 1.00 inch and about 2.00 inches, for example, about 1.20 inches. During the vacuum brazing process, a metallic foil material similar to or identical to the material utilized to form the first, second, and third plates, 202, 204, 206, respectively, is heated to near or above the melting point of the metallic material in order to braze the first plate 202 and the third plate 206 to the second plate 204.
Advantageously, the gas passages 111 formed in the first plate 202, the second plate 204, and the third plate 206 may be machined prior to brazing which improves efficiency of the machining process and the reliability with which the gas passages 111 are fabricated. Because the dimensions of the gas passages 111 influence gas flow distribution and various plasma characteristics and can be better controlled by machining the plates 202, 204, 206 separately, without a reduction in mechanical integrity of the diffuser 110 after brazing, improved film deposition uniformity may be achieved when processing substrates. In addition, cost reductions of diffuser fabrication may be realized according to the embodiments described herein.
Each of the gas passages 111 formed in the diffuser 110 are defined by a first bore 208 and a second bore 212 coupled together by an orifice hole 214. The first bore 208, the orifice hole 214, and the second bore 212 form a fluid path through the diffuser 110. The first bore 208 extends a first depth 222 from the first surface 240 of the first plate 202 to the second surface 242 of the first plate 202. The first depth 222 may extend between about 0.40 inches and about 1.20 inches, such as between about 0.60 inches and about 1.00 inch, for example, about 0.80 inches. In certain embodiments, the first depth 222 corresponds to a thickness of the first plate 202. The first bore 208 generally has a diameter 228 of between about 0.09 to about 0.22 inches, and in one embodiment, is about 0.15 inches.
The second bore 212 is formed in the third plate 206 of the diffuser 110 and extends a second depth 226 from the first surface 244 of the third plate 206 to the bottom surface 140 of the third plate 206. The second depth 226 may extend between about 0.10 inches and about 1.00 inch, such as between about 0.20 inches and about 0.40 inches, for example about 0.28 inches. A first region 210 of the second bore 212, which extends from the first surface 244 of the third plate toward the bottom surface 140, may have a diameter similar to the diameter 228 of the first bore 208. A second region 211 of the second bore 212 extends from the first region 210 to the bottom surface 140 of the third plate 206.
In one embodiment, a diameter of the second region 211 of the second bore 212 increases from the first region 210 to the bottom surface 140. In one embodiment, a diameter 232 of the second bore 212, measured where the second bore 212 intersects the bottom surface 140, is between about 0.10 inches and about 0.50 inches, such as between about 0.20 inches and about 0.30 inches, for example, about 0.24 inches. The second region 211 of the second bore 212 may also be flared at an angle 234 of between about 10 degrees and about 50 degrees relative to a hypothetical vertical axis. In one embodiment, the flaring angle 234 is between 15 degrees and about 30 degrees, such as between about 20 degrees and about 25 degrees, for example, about 22 degrees.
In one example, the diffuser 110 may be used to process 1500 mm by 1850 mm substrates and has second bores 212 at a diameter of about 0.24 inches and at a flare angle 234 of about 22 degrees. A distance 236 between adjacent second bores 212 is between about 0.0 inches to about 0.6 inch, and in one embodiment, is between about 0.01 inches and about 0.40 inches. The diameter 228 of the first bore 208 is usually, but not limited to, at least equal to or smaller than the diameter 232 of the second bore 212. The second regions 211 of the second bore 212 may be tapered, beveled, chamfered or rounded to minimize the pressure loss of gases flowing out from the orifice hole 214 and into the second bore 212.
The orifice hole 214, which is formed in the second plate 204, fluidly couples the first bore 208 to the second bore 212. In one embodiment, the orifice hole 214 is substantially aligned with a center 238 of the first bore 208 and the center 238 of the second bore 212. The orifice hole 214 has a diameter 230 of between about 0.001 inches and about 0.05 inches, such as between about 0.010 inches and about 0.030 inches, for example, about 0.018 inches. The orifice hole 214 extends a third depth 224 from the first surface 218 of the second plate 204 to the second surface 216 of the second plate 204. The third depth 224 may extend between about 0.01 inches and about 0.50 inches, such as between about 0.05 inches and about 0.20 inches, for example, about 0.10 inches. In certain embodiments, the third depth 224 of the orifice hole 214 corresponds to a thickness of the second plate 204.
The third depth 224 and diameter 230 (or other geometric attribute) of the orifice hole 214 is the primary source of back pressure in the volume between the diffuser 110 and the backing plate 112 (shown in
In summation, an improved diffuser is described herein which provides for improved manufacturing accuracy and efficiency. By more precisely controlling fabrication of the gas passages formed in the diffuser, fabrication cost reductions may be realized and improved deposition film uniformity results may be achieved.
While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201741018368 | May 2017 | IN | national |
