Patent Application
20190382891
Embodiments disclosed herein generally relate to apparatus for depositing films on a substrate and more specifically, to apparatus for facilitating uniform thickness of the films deposited on a substrate.
Electronic devices, such as thin film transistors (TFT's), photovoltaic (PV) devices or solar cells and other electronic devices have been fabricated on thin, flexible media for many years. The substrates may be made of glass, polymers, or other material suitable for electronic device formation. The substrates are typically processed in a tool that has multiple chambers, such as a cluster tool, and the substrates are transferred into and out of the various chambers that perform different processing steps in order to form the electronic devices thereon.
To facilitate transfer of the substrates into and out of the chambers, substrate support pins that extend through an upper surface of a substrate support based on movement of the substrate support, are utilized. For example, lowering of the substrate support actuates the substrate support pins such that the support pins contact the substrate so that the substrate may be spaced apart from the substrate support. This spacing allows a transfer mechanism, such as a robot blade or end effector, to move between the substrate and the upper surface of the substrate support and lift the substrate off the substrate support without causing damage to the substrate support or the substrate. When the substrate support is raised, the substrate support pins retract into the surface of the substrate support thereby placing the substrate into contact with the surface, and the substrate support pins rest under the substrate during processing thereof.
However, the areas of the substrate where the substrate support pins are located suffer from sub-optimal deposition as compared to other areas of the substrate. For example, the areas of the substrate corresponding to the locations of the substrate support pins have a film thickness that is less than a film thickness as compared to other areas of the substrate. This occurs for various reasons, one of which may be a difference in temperature of the substrate where the substrate support pins are located. The sub-optimal deposition of the substrate at locations corresponding to the locations of the substrate support pins may create problems in the final display product, one major problem being a “mura effect” or “clouding” of portions of the final display product, which typically corresponds to the locations of the substrate support pins.
What is needed are apparatus to prevent or minimize the non-uniform deposition of areas of a substrate to the locations of the substrate support pins.
Embodiments described herein provide an apparatus for providing an inductance at positions that correspond to positions of substrate support pins. In one embodiment, a substrate support pin includes a head portion having a first lateral dimension, a first portion coupled to the head portion, the first portion having a second lateral dimension substantially less than the first dimension, and a second portion coupled to the first portion, the second portion is a metal coil.
In another embodiment, a support pedestal for a vacuum chamber includes a body having a plurality of openings formed between two major sides of the body, and a substrate support pin disposed in each of the plurality of openings. Each of the substrate support pins includes a head portion having a first lateral dimension, a first portion coupled to the head portion, the first portion having a second lateral dimension substantially less than the first dimension, and a second portion coupled to the first portion, the second portion is a metal coil.
In another embodiment, an apparatus includes a chamber body defining a processing volume, and a substrate support disposed in the processing volume. The substrate support includes a body having a plurality of openings formed between two major sides of the body, and a substrate support pin disposed in each of the plurality of openings. Each of the substrate support pins includes a head portion having a first lateral dimension, a first portion coupled to the head portion, the first portion having a second lateral dimension substantially less than the first dimension, and a second portion coupled to the first portion, the second portion is a metal coil.
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, and 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 provide an apparatus for providing an inductance at positions that correspond to positions of substrate support pins. The apparatus includes one or more substrate support pins. Each substrate support pin includes a head portion, a first portion, and a second portion. The second portion is an inductor that provides inductance at positions of substrate support pins. The inductance provided by the second portion of the substrate support pin changes the impedance to match the impedance at areas of the substrate support without the substrate support pins. With matched impedance, the plasma density over the areas of the substrate support with the support pins and without the support pins is uniform, leading to improved film thickness uniformity. The uniform film thickness thus reduces or eliminates clouding or the “mura effect”.
As shown in
A pedestal or substrate support 104 is disposed in the processing volume 111 opposing a showerhead assembly 114. The substrate support 104 is adapted to support the substrate 101 on an upper or support surface 107 during processing. The substrate support 104 is also coupled to an actuator 138 via a hollow shaft 137. The actuator is configured to move the substrate support 104 at least vertically to facilitate transfer of the substrate 101 and/or adjust a distance between the substrate 101 and the showerhead assembly 114. One or more support pins 130 extend through the substrate support 104. Each of the support pins 130 is movably disposed within a corresponding opening 125 formed in the substrate support 104. Each of the support pins 130 is connected to the bottom 119 by a connector 131. In one embodiment, the connector 131 is a coiled wire made of a conductive metal, such as aluminum. In another embodiment, the connector 131 is a strap or straps made of a conductive metal, such as aluminum.
In the embodiment shown in
The showerhead assembly 114, backing plate 108, and the conduit 134 are generally formed from electrically conductive materials and are in electrical communication with one another. The chamber body 102 is also formed from an electrically conductive material. The chamber body 102 is generally electrically insulated from the showerhead assembly 114. In one embodiment, the showerhead assembly 114 is mounted on the chamber body 102 by a bracket 135. In one embodiment, the substrate support 104 is also electrically conductive, and the substrate support 104 is adapted to function as a shunt electrode to facilitate a ground return path for RF energy. A plurality of electrical return devices 109A, 1098 may be coupled between the substrate support 104 and the sidewall 117 and/or the bottom 119 of the chamber body 102.
Using a process gas from the processing gas source 122, the processing system 100 may be configured to deposit a variety of materials on the large area substrate 101, including but not limited to dielectric materials (e.g., SiO2, SiOxNy, derivatives thereof or combinations thereof), semiconductive materials (e.g., Si and dopants thereof), and/or barrier materials (e.g., SiNx, SiOxNy or derivatives thereof). Specific examples of dielectric materials and semiconductive materials that are formed or deposited by the processing system 100 onto the large area substrate may include epitaxial silicon, polycrystalline silicon, amorphous silicon, microcrystalline silicon, silicon germanium, germanium, silicon dioxide, silicon oxynitride, silicon nitride, dopants thereof (e.g., B, P, or As), derivatives thereof or combinations thereof. The processing system 100 is also configured to receive gases such as argon, hydrogen, nitrogen, helium, or combinations thereof, for use as a purge gas or a carrier gas (e.g., Ar, H2, N2, He, derivatives thereof, or combinations thereof). One example of depositing silicon thin films on the large area substrate 101 using the processing system 100 may be accomplished by using silane as the precursor gas in a hydrogen carrier gas. The showerhead assembly 114 is generally disposed opposing the substrate support 104 in a substantially parallel manner to facilitate plasma generation therebetween.
A temperature control device 106 is also disposed within the substrate support 104 to control the temperature of the substrate 101 before, during, or after processing. In one aspect, the temperature control device 106 comprises a heating element to preheat the substrate 101 prior to processing. In this embodiment, the temperature control device 106 may heat the substrate support 104 to a temperature between about 200° C. and 250° C. During processing, temperatures in the processing region 112 reach or exceed 400° C. and the temperature control device 106 may comprise one or more coolant channels to cool the substrate 101. In another aspect, the temperature control device 106 may function to cool the substrate 101 after processing. Thus, the temperature control device 106 may be coolant channels, a resistive heating element, or a combination thereof. Electrical leads for the temperature control device 106 may be routed to a power source and controller (both not shown) through the hollow shaft 137.
In one embodiment, the sleeve 204 is a straight ceramic hollow tube. The sleeve 204 is fabricated from a dielectric material, such as a ceramic material, for example Si2O3 or AlN. The head portion 202 has a lateral dimension D1 that is greater than a lateral dimension D2 of the sleeve 204. The head portion 202 prevents the support pin 130 from moving completely through the opening 125, thereby allowing the support pin 130 to be suspended when the substrate support 104 is in a raised position as shown in
The second portion 206 of the support pin 130 is an inductor, such as a metal coil or metal coil bar. The second portion 206 is fabricated from an electrically conductive material, such as a metal, for example aluminum. The second portion 206 of the support pin 130 helps reduce the impedance in areas of the substrate support 104 with the support pins 130. During operation, the RF power delivered to areas of the substrate support 104 without the support pins 130 is different from the RF power delivered to areas of the substrate support 104 with the support pins 130. The difference in RF power is due to a difference in the impedance caused by additional components in the RF power flow path through areas with the support pins 130. For example, an air gap is formed between the substrate 101 and the head portion 202 of the support pin 130, and an area of the head portion 202 of the support pin 130 is in contact with the substrate support 104. The second portion 206 is utilized to match the impedance of the areas of the substrate support 104 with the support pins 130 to the impedance of the areas of the substrate support 104 without the support pins 130. With the impedance of the areas of the substrate support 104 with the support pins 130 and without the support pins 130 matched, the plasma density over the areas of the substrate support 104 with the support pins 130 and without the support pins 130 is uniform, leading to improved film thickness uniformity. The uniform film thickness thus reduces or eliminates clouding or the “mura effect”.
The first portion 203 has a longitudinal dimension L1 and a lateral dimension D4. In one embodiment, the lateral dimension D4 is a diameter. The lateral dimension D4 is substantially less than the lateral dimension D1 of the head portion 202. The second portion 206 has a longitudinal dimension L2 and a lateral dimension D3. In one embodiment, the lateral dimension D3 is a diameter. The sleeve 204 has the lateral dimension D2. In one embodiment, the lateral dimension D2 is a diameter. In one embodiment, the longitudinal dimension L1 of the first portion 203 is substantially greater than the longitudinal dimension L2 of the second portion 206, such as about 30 percent to about 60 percent greater than the longitudinal dimension L2. In one embodiment, the lateral dimension D2 of the sleeve 204 is substantially the same as the lateral dimension D3 of the second portion 206. In another embodiment, the lateral dimension D2 of the sleeve 204 is substantially smaller than the lateral dimension D3 of the second portion 206, and the second portion 206 does not move into the opening 125 of the substrate support 104 (as shown in
The connector 208 may be any suitable connectors, such as a threaded connector. The connector 208 is fabricated from an electrically conductive material, such as a metal, for example aluminum. An end piece 210 is connected to the second portion 206 at an end opposite the connector 208. The end piece 210 is configured to be connected to the connector 131 (
The first portion 203 is configured to be coupled to the connector 208. In one embodiment, at least a portion of the first portion 203 is threaded, and the connector 208 is a nut. In one embodiment, the second portion 206 of the support pin 130 includes a connecting portion 310 configured to be coupled to the connector 208. The connecting portion 310 and the second portion 206 may be made of a single piece of material. In one embodiment, the connecting portion 310 is threaded, and the connector 208 is a nut. In one embodiment, the connecting portion 310 of the second portion 206 is directly coupled to the first portion 203 (e.g., threaded into the sleeve 204), and the connector 208 and the connecting portion 308 are not present.
The second portion 206 may be a coil having a plurality of turns. The number of turns depends on the amount of inductance to be generated in order to match the impedance of the areas of the substrate support without the support pins 130. In one embodiment, the number of turns ranges from about 30 to 70, such as about 40 to 60. In one embodiment, the second portion 206 is hollow. A connecting member 312 connects the second portion 206 to the end piece 210. The connecting member 312 may be fabricated from an electrically conductive material, such as a metal, for example aluminum.
The magnetic insert 314 has a longitudinal dimension L3 and a lateral dimension D5. The lateral dimension D5 of the magnetic insert 314 is substantially less than the lateral dimension D3 of the second portion 206, because the magnetic insert 314 is configured to be inserted into the second portion 206. The longitudinal dimension L3 of the magnetic insert 314 depends on the additional amount of inductance to be generated by the second portion 206. The longitudinal dimension L3 of the magnetic insert 314 is less than or equal to the longitudinal dimension L2 of the second portion 206. In one embodiment, the longitudinal dimension L3 of the magnetic insert 314 ranges from about five percent to about 100 percent of the longitudinal dimension L2 of the second portion 206, such as about 20 percent to about 60 percent of the longitudinal dimension L2 of the second portion 206.
Embodiments of the support pin 130 as described herein has been tested and the addition of a second portion 206 that is an inductor as described herein significantly increases film thickness on a substrate at positions corresponding to the position of the support pin 130. The increased film thickness reduces or eliminates clouding or the “mura effect” on the substrate.
While the foregoing is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof.
