Substrate support with ceramic insulation

Embodiments of the present invention generally relates to substrate supports for use in a plasma processing chamber. The substrate supports, which are metallic, have ceramic inserts to prevent arcing between the substrate support and the shadow frame used to protect the edges of the substrate support during processing. In large area substrate processing chambers, the shadow frame may comprise multiple pieces. The individual pieces may be coupled together, but spaced slightly apart by a gap to permit thermal expansion. Ceramic inserts are positioned on the substrate support so that when a shadow frame is positioned adjacent thereto, the ceramic inserts are located adjacent the gaps in the shadow frame. The ceramic inserts adjacent the gap prevent and/or reduce the arcing because the gaps are located over electrically insulating material rather than electrically conductive material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to substrate supports for use in a plasma processing chamber.

2. Description of the Related Art

Televisions, computer monitors and other flat panel displays (FPDs) are typically fabricated in large area substrate processing chambers. These large area processing chambers are designed to process rectangular shaped substrates in order to maximize the effective use of the substrate. As most FPDs are rectangular in shape, a processing chamber designed to process circular shaped substrates, such as semiconductor wafers, may not be desirable due to the amount of wasted substrate that would need to be removed to form the final shape of the rectangular FPD.

As the large area processing chambers continue to increase in size, fabricating the various chamber components out of a unitary piece become difficult. Thus, some chamber components may comprise multiple pieces. Each piece may expand and contract due to thermal expansion issues. Therefore, the multiple pieces may be spaced slightly apart to create a gap between adjacent pieces. If the pieces are biased, arcing can easily occur within the chamber.

Therefore, there is a need in the art for avoiding arcing in a large area processing chamber where multi-piece components are utilized.

SUMMARY OF THE INVENTION

Embodiments of the present invention generally relates to substrate supports for use in a plasma processing chamber. The substrate supports, which are metallic, have ceramic inserts to prevent arcing between the substrate support and the shadow frame used to protect the edges of the substrate support during processing. In large area substrate processing chambers, the shadow frame may comprise multiple pieces. The individual pieces may be coupled together, but spaced slightly apart by a gap to permit thermal expansion. Ceramic inserts are positioned on the substrate support so that when a shadow frame is positioned adjacent thereto, the ceramic inserts are located adjacent the gaps in the shadow frame. The ceramic inserts adjacent the gap prevent and/or reduce the arcing because the gaps are located over electrically insulating material rather than electrically conductive material.

In one embodiment, a shadow frame to be disposed in a chamber body is disclosed. The shadow frame comprises a first piece, a second piece spaced from the first piece by a gap and one or more coupling elements coupled to the first piece and the second piece.

In another embodiment, an apparatus is disclosed. The apparatus comprises a chamber body, a rectangular substrate support disposed in the chamber body and having a first portion having a first thickness that surrounds a second portion having a second thickness that is greater than the first thickness, and a ceramic insert coupled to the substrate support and having a first top surface that is parallel to the top surface of the first portion and a second top surface that is parallel to the top surface of the second portion.

In another embodiment, a substrate support is disclosed. The substrate support includes a rectangular substrate support body having a first portion having a first thickness that surrounds a second portion having a second thickness that is greater than the first thickness and a ceramic insert coupled to the substrate support body and having a first top surface that is parallel to the top surface of the first portion and a second top surface that is parallel to the top surface of the second portion.

In another embodiment, a plasma enhanced chemical vapor deposition apparatus is disclosed. The apparatus includes a chamber body, a gas distribution showerhead disposed in the chamber body, a rectangular substrate support disposed in the chamber body opposite the gas distribution showerhead and having a first portion having a first thickness that surrounds a second portion having a second thickness that is greater than the first thickness, a ceramic insert coupled to the substrate support and having a first top surface that is parallel to the top surface of the first portion and a second top surface that is parallel to the top surface of the second portion, and a shadow frame disposed in the chamber body. The shadow frame comprises a first piece, a second piece spaced from the first piece by a gap and one or more coupling elements coupled to the first piece and the second piece.

DETAILED DESCRIPTION

Embodiments of the present invention generally relates to substrate supports for use in a plasma processing chamber. The substrate supports, which are metallic, have ceramic inserts to prevent arcing between the substrate support and the shadow frame used to protect the edges of the substrate support during processing. In large area substrate processing chambers, the shadow frame may comprise multiple pieces. The individual pieces may be coupled together, but spaced slightly apart by a gap to permit thermal expansion. Ceramic inserts are positioned on the substrate support so that when a shadow frame is positioned adjacent thereto, the ceramic inserts are located adjacent the gaps in the shadow frame. The ceramic inserts adjacent the gap prevent and/or reduce the arcing because the gaps are located over electrically insulating material rather than electrically conductive material.

Description below will be made with reference to a plasma enhanced chemical vapor deposition (PECVD) chamber, such as a 90K PECVD chamber available from AKT America, Inc, a subsidiary of Applied Materials, Inc., Santa Clara, Calif. It is to be understood that the embodiments discussed herein may be practiced in other processing chambers as well, including those sold by other manufacturers.

FIG. 1Ais a schematic cross-sectional view of an apparatus100according to an embodiment of the invention. The apparatus100includes a chamber body102having an opening104through at least one wall through which substrates may enter and exit the chamber body102. A gas distribution showerhead110is disposed opposite a substrate support126in the chamber. The substrate support126is movable on a stem128in a direction perpendicular to the face of the gas distribution showerhead110that is opposite the backing plate108, as shown by arrows “A”. The substrate support126may comprise an electrically conductive material such as aluminum or anodized aluminum.

As shown in more detail inFIG. 1B, the substrate support126has a rectangular cross section and has multiple different levels. The lower most level is where the shadow frame124rests during substrate118processing. The upper most level is where the substrate118is disposed. The lower level entirely surrounds the upper level.

Processing and/or cleaning gas is delivered to the processing area122of the apparatus100from a gas source106. The gas enters the chamber through the backing plate108that is spaced from a gas distribution showerhead110. The gas, upon exiting the opening in the backing plate108, expands into a plenum112formed between the gas distribution showerhead110and the backing plate108. The gas then travels from the plenum112into the processing area122by passing through gas passages114formed in the gas distribution showerhead110. Once in the processing area122, the gas is ignited into a plasma.

During operation, RF power is delivered from an RF power source116to the backing plate108. The RF current travels along the backside of the backing plate108to a bracket132that not only supports the gas distribution showerhead110, but also electrically couples the gas distribution showerhead110to the backing plate108. RF current travels along the surface of an electrically conductive structure and thus does not enter the plenum112. The RF current travels along the face of the gas distribution showerhead110that is opposite the backing plate108and ignites the processing gas into a plasma120in the processing area122. The RF current seeks to return to the source driving it.

In order to have a more predictable RF return path, an RF return mechanism130may provide an electrical connection between the substrate support126and the walls of the chamber body102. It is to be understood that RF return mechanism130may comprise any suitable mechanism upon which the RF current can travel such as a metal strap. As shown inFIG. 1A, the RF return mechanism130may be coupled to the wall at a location above the opening104in the chamber body. However, it is to be understood that the RF grounding mechanism may couple to the chamber body102at other locations.

When the RF return mechanism130is coupled to the chamber wall above the opening104, the RF return path is shortened because the RF current does not need to travel down the stem128and along the bottom of the chamber body102before moving up the chamber walls. It is believed that because the distance is shorter, arcing can occur between the gas distribution showerhead110and the shadow frame124even though the distance between the shadow frame124and the gas distribution showerhead110, represented by arrows “B”, is the same.

To alleviate the arcing, the shadow frame124may comprise an insulating material, such as a ceramic material. As discussed above, for large area processing chambers, fabricating a shadow frame124from a single piece of material may be quite expensive and difficult to fabricate. Therefore, the shadow frame124may comprise multiple pieces.

FIG. 2is a schematic top close up view of the apparatus100ofFIGS. 1A and 1B. As shown inFIG. 2, the shadow frame has two pieces124A,124B that are coupled together by coupling elements204. Because the shadow frame124has multiple pieces124A,124B, the pieces124A,124B will be spaced apart for thermal expansion purposes.

The coupling elements204may comprise a metallic material such as aluminum. Aluminum, which has a high thermal conductivity, will expand and contract and thus permit the space (represented by arrows “C”) between the adjacent shadow frame pieces124A,124B change throughout processing without the adjacent pieces124A,124B directly contacting one another. It is contemplated that the coupling elements204may comprise a ceramic material. The coupling elements204are coupled to the respective pieces124A,124B by one or more fasteners206such as a screw. It is to be understood that while three coupling elements204have been shown, more or less coupling elements204may be utilized. The coupling elements204may be evenly spaced along the width (shown by arrows “D”) of the pieces124A,124B.

Due to the space between adjacent pieces124A,124B, arcing can occur to the substrate support126. The arcing occurs due to the potential difference between the RF current along the substrate support126and the RF current at the edges of the pieces124A,124B or the RF current from the showerhead110or even from the plasma120. If the electrically conductive substrate support126is exposed by the space between adjacent shadow frame pieces124A,124B, arcing may occur. The arcing can be eliminated or substantially reduced by replacing the portion of the substrate support126that would be exposed by the space between adjacent shadow frame pieces124A,124B with an insert202directly under the space between adjacent pieces124A,124B. The inserts202may comprise an electrically insulating material such as a ceramic material. The inserts202replace the corners of the substrate support126and extends into the substrate support126a distance shown by arrows “E” in a first direction and a distance shown by arrows “F” in a second direction in order to provide sufficient electrical isolation between the ends of adjacent pieces124A,124B and the electrically conductive portion of the substrate support126. The inserts202operate to hide the exposed conductive surface of the substrate support126that is not in contact with the shadow frame pieces124A,124B.

FIGS. 3A and 3Bare a schematic isometric view of the substrate support126according to an embodiment of the invention. InFIG. 3A, the adjacent pieces124A,124B have been removed for clarity. InFIG. 3B, one piece124A is shown while an adjacent piece124B is shown in phantom. The substrate support126has recesses formed therein within which the inserts202are disposed. The recesses are formed in the both the topmost surface306of the substrate support126and the top surface308of the surrounding level upon which the shadow frame124rests. The inserts202are designed to fit within the recesses such that the exposed surfaces of the inserts202are flush with the exposed surfaces of the substrate support126.

As shown inFIGS. 3A and 3B, the insert202has a top surface302of a first portion310that is parallel to the top surface306of the substrate support126and substantially flush with the top surface306of the substrate support126. Additionally, the insert202has a second surface304that is flush with the top surface308of the surrounding level312of the substrate support126upon which the shadow frame124rests. The surrounding level312has a thickness shown by arrows “H” while the remainder of the substrate support126extends a distance represented by arrows “I” above the surrounding level312. Thus, the substrate support126has a total thickness represented by arrows “H” and “I” collectively. The distance “C” is less than the width of the top surface302and thus, the space between adjacent pieces124A,124B is always over an electrically insulating material at the locations where the pieces124A,124B are spaced from the substrate support126. In total, the insert202is sized such that there will be no location where the individual pieces124A,124B are: spaced apart, spaced from the substrate support126, and adjacent or above a conductive portion of the substrate support126.

The pieces124A,124B of the shadow frame124rest on the top surface308of the surrounding level312of the substrate support126and thus are in direct electrical contact with the surrounding level312of the substrate support126. However, the shadow frame pieces124A,124B are spaced from the top surface302of the insert202by a distance shown by arrows “G”. In absence of the insert202, the shadow frame124would be spaced a distance “G” from the conductive substrate support126and thus, could easily arc therebetween. The insert202, being electrically insulating and disposed directly beneath the space between adjacent pieces124A,124B of the shadow frame124, prevent, or at the very least reduce, arcing between the pieces124A,124B and the substrate support126.

It is important to understand that while the inserts202have been described as pieces that replace a portion of the substrate support126that has been removed, it is contemplated that the inserts202may comprise a cover disposed over a portion of the substrate support126without removing any portion of the substrate support126. Additionally, it is contemplated that the second surface304insert202can extend across the entire distance shown by arrows “J” and may be fastened to the substrate support126by any suitable fastener316.

By placing a portion of an electrically conductive substrate support with an electrically insulating material, arcing between the substrate support and a shadow frame disposed thereover during processing may be reduced or even eliminated. Thus, large area substrates can be easily processed under predictable processing chamber conditions.