Patent Application
20190378696
Embodiments of the present disclosure generally relate to process chambers, such as plasma enhanced chemical vapor deposition (PECVD) chambers. More particularly, embodiments of the present disclosure relate to a substrate support assembly disposed in a PECVD chamber.
Plasma enhanced chemical vapor deposition (PECVD) is used to deposit thin films on a substrate, such as a semiconductor wafer or a transparent substrate. PECVD is generally accomplished by introducing a precursor gas or gas mixture into a vacuum chamber containing a substrate disposed on a substrate support. The precursor gas or gas mixture is typically directed downwardly through a gas distribution plate situated near the top of the chamber. The precursor gas or gas mixture in the chamber is energized (e.g., excited) into a plasma by applying a power, such as a radio frequency (RF) power, to an electrode in the chamber from one or more power sources coupled to the electrode. The excited gas or gas mixture reacts to form a layer of material on a surface of the substrate. The layer may be, for example, a passivation layer, a gate insulator, a buffer layer, and/or an etch stop layer.
During PECVD, a capacitively coupled plasma, also known as a main plasma, is formed between the substrate support and the gas distribution plate. However, a parasitic plasma, also known as a secondary plasma, may be generated underneath the substrate support in a lower volume of the chamber. The parasitic plasma reduces the concentration of the capacitive coupled plasma, and thus reduces the density of the capacitive coupled plasma which reduces the deposition rate of the film. Furthermore, variation of the concentration and density of the parasitic plasma between chambers reduces the uniformity between films formed in separate chambers.
Accordingly, an improved substrate support assembly is needed to mitigate the generation of parasitic plasma.
Embodiments of the present disclosure generally relate to a metal shield to be used in a PECVD chamber. In one embodiment, a metal shield includes a metal plate, a metal hollow tube including a tubular wall, and a coolant channel formed in the metal plate and tubular wall of the metal hollow tube. The coolant channel includes a supply channel having a planar spiral pattern in the metal plate and a helical pattern in the tubular wall of the metal hollow tube. The coolant channel further includes a return channel having a planar spiral pattern in the metal plate and a helical pattern in the tubular wall of the metal hollow tube. The supply channel and the return channel are interleaved in the metal plate and the tubular wall.
In another embodiment, a substrate support assembly includes a heater plate, a thermal insulating plate having a surface facing the heater plate, and a first plurality of reduced contact features formed on the surface of the thermal insulating plate. The heater plate is in contact with the first plurality of reduced contact features. The substrate support assembly further includes a metal shield including a metal plate and a metal hollow tube having a metal tubular wall. The metal plate includes a surface facing the thermal insulating plate, and a second plurality of reduced contact features is formed on the surface of the metal plate. The thermal insulating plate is in contact with the second plurality of reduced contact features.
In another embodiment, a process chamber includes a chamber wall, a bottom, a gas distribution plate, and a substrate support assembly. The substrate support assembly includes a heater plate, a thermal insulating plate having a surface facing the heater plate, and a first plurality of reduced contact features formed on the surface of the thermal insulating plate. The heater plate is in contact with the first plurality of reduced contact features. The substrate support assembly further includes a metal shield including a metal plate and a metal hollow tube having a metal tubular wall. The metal plate includes a surface facing the thermal insulating plate, and a second plurality of reduced contact features is formed on the surface of the metal plate. The thermal insulating plate is in contact with the second plurality of reduced contact features.
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 of the present disclosure generally relate to a metal shield to be used in a PECVD chamber. The metal shield includes a substrate support portion and a shaft portion. The shaft portion includes a tubular wall having a wall thickness. The tubular wall has a supply channel of a coolant channel and a return channel of the coolant channel embedded therein. Each of the supply channel and the return channel is a helix in the tubular wall. The helical supply channel and the helical return channel have the same direction of rotation and are parallel to each other. The supply channel and the return channel are interleaved in the tubular wall. With the supply channel and return channel interleaved in the metal shield, the thermal gradient in the metal shield is reduced.
Embodiments herein are illustratively described below in reference to use in a PECVD system configured to process substrates, such as a PECVD system, available from Applied Materials, Inc., Santa Clara, Calif. However, it should be understood that the disclosed subject matter has utility in other system configurations such as etch systems, other chemical vapor deposition systems, and any other system in which a substrate is exposed to plasma within a process chamber. It should further be understood that embodiments disclosed herein may be practiced using process chambers provided by other manufacturers and chambers using multiple shaped substrates. It should also be understood that embodiments disclosed herein may be adapted for practice in other process chambers configured to process substrates of various sized and dimensions.
The substrate support assembly 128 includes a substrate support portion 130 and a shaft portion 134. The shaft portion 134 is coupled to a lift system 136 that is adapted to raise and lower the substrate support assembly 128. The substrate support portion 130 includes a substrate receiving surface 132 for supporting the substrate 105. Lift pins 138 are moveably disposed through the substrate support portion 130 to move the substrate 105 to and from the substrate receiving surface 132 to facilitate substrate transfer. The substrate support portion 130 may also include grounding straps 129 or 151 to provide RF grounding at the periphery of the substrate support portion 130. The substrate support assembly 128 is described in detail in
In one embodiment, the gas distribution plate 110 is coupled to a backing plate 112 at the periphery by a suspension 114. In other embodiments, the backing plate 112 is not present, and the gas distribution plate 110 is coupled to the walls 102. A gas source 120 is coupled to the backing plate 112 (or the gas distribution plate) through an inlet port 116. The gas source 120 may provide one or more gases through a plurality of gas passages 111 formed in the gas distribution plate 110 and to the processing volume 106. Suitable gases may include, but are not limited to, a silicon-containing gas, a nitrogen-containing gas, an oxygen-containing gas, an inert gas, or other gases.
A vacuum pump 109 is coupled to the process chamber 100 to control the pressure within the processing volume 106. An RF power source 122 is coupled to the backing plate 112 and/or directly to the gas distribution plate 110 to provide RF power to the gas distribution plate 110. The RF power source 122 may generate an electric field between the gas distribution plate 110 and the substrate support assembly 128. The electric field may form a plasma from the gases present between the gas distribution plate 110 and the substrate support assembly 128. Various RF frequencies may be used. For example, the frequency may be between about 0.3 MHz and about 200 MHz, such as about 13.56 MHz.
A remote plasma source 124, such as an inductively coupled remote plasma source, may also be coupled between the gas source 120 and the inlet port 116. Between processing substrates, a cleaning gas may be provided to the remote plasma source 124. The cleaning gas may be excited to a plasma within the remote plasma source 124, forming a remote plasma. The excited species generated by the remote plasma source 124 may be provided into the process chamber 100 to clean chamber components. The cleaning gas may be further excited by the RF power source 122 reduce recombination of the dissociated cleaning gas species. Suitable cleaning gases include but are not limited to NF3, F2, and SF6.
The chamber 100 may be used to deposit a material, such as a silicon-containing material. For example, the chamber 100 may be used to deposit one or more layers of amorphous silicon (a—Si), silicon nitride (SiNx), and/or silicon oxide (SiOx).
In one embodiment, the stem 206 and the heater plate 202 are fabricated from a single piece of material. The stem 206 is connected to a connector 216, which is in turn connected to the lift system 136.
The substrate support assembly 128 further includes a metal shield 208. The metal shield 208 includes a substrate support portion 210 supported by a shaft portion 212. The substrate support portion 210 is part of the substrate support portion 130 of the substrate support assembly 128, and the shaft portion 212 is part of the shaft portion 134 of the substrate support assembly 128. In one embodiment, the substrate support portion 210 of the metal shield 208 is a metal plate, and the shaft portion 212 of the metal shield 208 is a metal hollow tube. The substrate support portion 210 and the shaft portion 212 of the metal shield 208 are fabricated from a metal, such as aluminum, molybdenum, titanium, beryllium, copper, stainless steel, or nickel. In one embodiment, the substrate support portion 210 and the shaft portion 212 of the metal shield 208 are fabricated from aluminum, because aluminum is not eroded by the cleaning species, such as fluorine containing species. In another embodiment, the substrate support portion 210 is fabricated from stainless steel. In one embodiment, the substrate support portion 210 and the shaft portion 212 of the metal shield 208 are separate components that are connected by any suitable connecting method. In another embodiment, the substrate support portion 210 and the shaft portion 212 of the metal shield 208 are a single piece of material.
The metal shield 208 is grounded via the grounding straps 129 or 151 during a PECVD process. The grounded metal shield 208 functions as an RF shield that can substantially reduce the generation of parasitic plasma. In one embodiment, the metal shield 208 is fabricated from aluminum, because aluminum does not contribute to metal contamination and is resistive to the fluorine containing species formed during the cleaning process. However, mechanical and electrical properties of the metal shield 208 fabricated from aluminum can degrade at processing temperatures greater than 500 degrees Celsius. Thus, in applications when the metal shield 208 is intended for use at temperatures near or exceeding 500 degrees Celsius, the metal shield 208 includes cooling elements, such as a coolant channel 222 is formed in the metal shield 208.
The shaft portion 212 of the metal shield 208 includes a tubular wall 223, and the coolant channel 222 is formed in the tubular wall 223 and the substrate support portion 210. The coolant channel 222 includes a supply channel 224 and a return channel 226. Each of the supply channel 224 and the return channel 226 is a helix in the tubular wall 223. The helical supply channel 224 and the helical return channel 226 formed in the tubular wall 223 have the same direction of rotation and are parallel to each other. The helical supply channel 224 and the helical return channel 226 are alternately positioned in the tubular wall 223. In other words, the helical supply channel 224 and the helical return channel 226 are interleaved in the tubular wall 223. The supply channel 224 and the return channel 226 formed in the substrate support portion 210 have planar spiral patterns, and the spiral supply channel 224 and the spiral return channel 226 are alternately positioned in the substrate support portion 210. In other words, the spiral supply channel 224 and the spiral return channel 226 are interleaved in the substrate support portion 210. With the supply channel 224 and return channel 226 positioned alternately, or interleaved, in the metal shield 208, the thermal gradient in the metal shield 208 is reduced.
The thermal insulating plate 204 is disposed between the heater plate 202 and the substrate support portion 210 of the metal shield 208 to keep the metal shield 208 at a lower temperature than the heater plate 202 during operation. In addition, a thermal insulating tube 215 is disposed between the stem 206 and the shaft portion 212 of the metal shield 208 to reduce heat transfer from the stem 206 to the shaft portion 212 of the metal shield 208. Furthermore, reduced contact features 218, 220 are utilized at the interface between the heater plate 202 and the thermal insulating plate 204 and at the interface between the thermal insulating plate 204 and the substrate support portion 210 of the metal shield 208, respectively. The reduced contact features 218, 220 limit contact and thus limit thermal conductive heat transfer from the heater plate 202 to the metal shield 208 during operation. The reduced contact feature 218 extends from a surface 234 of the thermal insulating plate 204, and the surface 234 faces the heater plate 202. The thermal insulating plate 204 has a surface 232 opposite the surface 234. The reduced contact feature 220 is disposed on or in a surface 230 of the substrate support portion 210 of the metal shield 208, and the surface 230 faces the thermal insulating plate 204. The heater plate 202 is in contact with the reduced contact feature 218, and a gap G1 is formed between the heater plate 202 and the surface 234 of the thermal insulating plate 204. The thermal insulating plate 204 is in contact with the reduced contact feature 220, and a gap G2 is formed between the surface 232 of the thermal insulating plate 204 and the surface 230 of the substrate support portion 210 of the metal shield 208.
During operation, a coolant, such as water, ethylene glycol, perfluoropolyether fluorinated fluid, or combinations thereof, flows from the supply channel 224 to the return channel 226. The return channel 226 is fluidly connected to the supply channel 224 at a location in the substrate support portion 210. The supply channel 224 is substantially parallel to the return channel 226 in the substrate support portion 210 and the shaft portion 212. Furthermore, the helical supply channel 224 and the helical return channel 226 formed in the shaft portion 212 have the same direction of rotation. The helical supply channel 224 and the helical return channel 226 are interleaved in the shaft portion 212, and the spiral supply channel 224 and the spiral return channel 226 are interleaved in the substrate support portion 210. With the supply channel 224 and return channel 226 interleaved in the metal shield 208, the thermal gradient in the metal shield 208 is reduced.
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. 62/682,557, filed on Jun. 8, 2018, which herein is incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62682557 | Jun 2018 | US |
