Patent Application
20180218905
Embodiments of the present disclosure generally relate to a substrate support used in flat panel display manufacturing. More particularly, embodiments of the disclosure relate to substrate lift pins for use in a vacuum chamber utilized to deposit materials on flat media, such as rectangular, flexible sheets of glass, plastic, or other material in the manufacture of flat panel displays, photovoltaic devices, or solar cells among other applications.
Electronic devices, such as thin film transistors (TFT's), photovoltaic (PV) devices or solar cells, and other electronic devices have been fabricated on thin media for many years. Fabricating the electronic devices on substrates having a large surface area, such as two square meters, or larger, produce an end product of a larger size and/or decrease fabrication costs per device (e.g., pixel, TFT, photovoltaic or solar cell, etc.).
Plasma-enhanced chemical vapor deposition (PECVD) is a process in which various materials are deposited on a substrate in order to create a film. Generally, during a PECVD process, the substrate is supported by a substrate support in a vacuum deposition processing chamber and is heated to several hundred degrees Celsius during processing. Deposition gases are injected into the chamber, a plasma is formed of the deposition gases, and a chemical reaction occurs on and, or, with a surface of the substrate, resulting in the deposition of a specific film thereon. The PECVD process is used to manufacture liquid crystal displays, flat panel displays, film transistors as well as other semiconductor devices.
During a PECVD process, plasma distribution affects the quality of the film deposited in terms of both thickness and film properties. If the plasma distribution above the surface of a substrate is not generally uniform, then the quality of the film deposited will not be uniform. One source of non-uniform plasma distribution is unequal energy coupling with the plasma above substrate lift pins disposed in the substrate support. Lift pins are conventionally used to raise the substrate from a substrate receiving surface of the substrate support which provides access to the backside of the substrate by a robot handler for transferring of the substrate to and from the PECVD chamber. Typically, handling schemes for large area substrates use a lift pin configuration having a plurality of lift pins arranged about the edges of the substrate support (edge lift pins) and one or more lift pins arranged towards the center of the substrate support (inner lift pins). The inner lift pins are necessary for large area substrate handling because the weight of large area substrates causes sagging in the middle of the substrate as it is lifted from a substrate support that would, without the inner lift pins, prevent access thereto by the robot handler. Unfortunately, discontinuity marks (visible disruptions in the appearance of the deposited film, also known as golf tee mura) are commonly found on the processed substrate in regions disposed above and, or, proximate to the lift pins.
Conventionally, display screens that do not require large surface areas, such as those for PDA or computer screens, are cut from the large area substrate in a pattern designed to avoid discontinuity marks which might be visible to a consumer. However, the discontinuity marks in the large area substrate remain undesirable as they result in wasted substrate surface area and, therefore, increased manufacturing costs. Further, processes designed to avoid discontinuity marks in the center of a substrate require additional patterning steps and procedures that increase overall manufacturing time. In applications that require large continuous substrate areas, such as large screen television production, such discontinuity marks cannot be avoided.
Accordingly, what is needed in the art are improved apparatus and methods to equalize plasma distribution for large area substrates and substantially eliminate or minimize visible discontinuity marks in and, or, on the surfaces thereof.
Embodiments described herein relate to biasing or grounding of one or more lift pins used for large area substrate handling in order to eliminate, or minimize, the appearance of discontinuity marks in the substrate from unequal distribution of the plasma formed thereabove.
In one embodiment, a processing chamber is provided. The processing chamber includes a chamber body defining a processing volume and a substrate support disposed within the processing volume, where the substrate support has a plurality of openings formed therethrough. The processing chamber further includes one or more first lift pins respectively disposed through one or more first openings of the plurality of openings and one or more second lift pins respectively disposed through one or more second opening of the plurality of openings, where the one or more second lift pins are electrically isolated from the substrate support.
In another embodiment, a processing kit is provided. The processing kit includes one or more lift pins. The one or more lift pins each comprise an elongated shaft coupled to a head, the head having a top surface, sides, and a bottom surface and a coating of electrically non-conductive material disposed on the elongated shaft, the sides of the head, and the bottom surface of the head.
In another embodiment, a method of processing a substrate is provided. The method includes positioning a substrate on a substrate support, where the substrate support disposed in a processing volume of a processing chamber, applying a bias voltage to one or more lift pins movably disposed through the substrate support, flowing a processing gas into the processing volume, igniting and maintaining a plasma of the processing gas, exposing the substrate to the plasma, and depositing a material layer on the substrate.
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 typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure 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 disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.
Embodiments described herein generally relate to methods and apparatus for equalizing plasma distribution above a substrate support in order to eliminate or minimize discontinuity marks formed during plasma enhanced chemical vapor deposition (PECVD) of a material layer onto a large area substrates. Discontinuity marks, corresponding to lift pin configurations in the substrate support, can be eliminated or minimized by biasing or by grounding desired lift pins. To prevent shorting between biased or grounded lift pins and the substrate support, the lift pins are electrically isolated from the substrate support. In one embodiment, one or more biased or grounded lift pins are electrically isolated from the substrate support by an electrically insulating material disposed on surfaces of the one or more lift pins. In another embodiment, one or more lift pins are electrically isolated from the substrate support by an electrically insulating material disposed on the walls of one or more respective openings formed through the substrate support.
The gas distribution assembly 106 herein is further coupled to the backing plate 112 by a showerhead suspension 134, such as a flexible metal skirt. Typically, the showerhead suspension 134 includes a lip 136 upon which at least a portion of the gas distribution assembly 106 rests. In some embodiments, the backing plate 112 rests on an upper surface of a ledge 114 of the chamber walls 102 which seals the processing volume 105 from atmospheric conditions.
The substrate support 118 is disposed on a shaft 117 sealingly extending through the chamber base 104. The shaft 117 is coupled to an actuator 116 which is used to raise and lower the shaft 117, and the thus substrate support 118 disposed thereon, to facilitate processing of a substrate 120 and transfer thereof to and from the processing volume 105. The substrate 120 is loaded into the processing volume 105 through a second opening 108 in one of the one or more chamber walls 102, which is conventionally sealed with a door or a valve (not shown) during substrate processing. A plurality of lift pins, such as lift pins 122A, 122B, disposed above, but engageable with, the chamber base 104 are moveably disposed through the substrate support 118 to facilitate transferring of the substrate 120 to and from a substrate receiving surface thereof. When the substrate support 118 is in a lowered position the plurality of lift pins 122A, 122B contact the chamber base 104 and are moved to extend above the substrate support 118 lifting the substrate 120 from the substrate receiving surface and enabling access to the substrate 120 by a robot handler (not shown). When the substrate support 118 is in a raised and, or, processing position, the tops of the plurality of lift pins 122A, 122B are flush with or below the substrate receiving surface of the substrate support 118 and the substrate 120 rests thereon. In some embodiments, the substrate support 118 further includes heating and/or cooling elements 124 to maintain the substrate support 118, and thus the substrate 120 disposed thereon at a desired temperature. Typically, the substrate support 118 is electrically coupled to one or more RF return straps 126 to provide an RF return path at the periphery thereof.
Herein, the plurality of lift pins 122A, 122B include one or more edge lift pins 122A for edge and corner support of the substrate 120 during substrate transfer and one or more inner lift pins 122B for center support of the substrate 120, where center support includes locations radially inward from the locations of the edge lift pins 122A in a direction towards the center of the substrate support 118. Typically, each of the plurality of lift pins 122A,122B include an elongated shaft 304 (See
In one embodiment, the one or more inner lift pins 122B are electrically coupled to a bias potential source 185, such as an RF source. A bias voltage provided to the one or more inner lift pins 122B provides for equalized capacitive energy coupling with the plasma, formed thereabove, across the surfaces of the substrate support 118 and the one or more inner lift pins 122B disposed therethrough. The equalized plasma energy coupling provides a uniform plasma distribution that substantially eliminates or minimizes film deposition discontinuities on the substrate in regions above the one or more inner lift pins 122B, compared to the substrate surfaces proximate thereto, which eliminates and, or, minimizes discontinuity marks in the deposited film, such as the discontinuity marks 208 described in
In another embodiment, the one or more inner lift pins 122B are coupled to an earthen ground 188 and the grounded one or more inner lift pins 122B are each electrically isolated from the substrate support 118.
An opening in the substrate support 118 is bounded by opening walls 320 defining the opening. The opening walls 320 have a liner 322 so that the one or more inner lift pins 122B are electrically isolated from the substrate support 118 when the substrate support is in a raised position, as shown in
The apparatus and methods described herein provide for the elimination and, or, minimization of discontinuity marks, also known as golf tee mura, on and, or, in a material layer deposited using a plasma enhanced CVD process by equalizing capacitive energy coupling with the plasma across the surface of a substrate support, including across the surfaces of lift pins disposed therethrough. To prevent shorting between biased or grounded lift pins and the substrate support, the biased or grounded lift pins described herein are electrically isolated from the substrate support. In some embodiments, the lift pins are electrically isolated from the substrate support by a coating of electrically insulating material disposed on the lift pins. In other embodiments, the lift pins are electrically isolated from the substrate support by lining the openings formed in the substrate support with an electrically insulating material.
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.
This application claims priority to U.S. Provisional Patent Application Ser. No. 62/453,725 filed on Feb. 2, 2017, which is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62453725 | Feb 2017 | US |
