Patent Application
20180235110
The disclosure relates to a method of forming semiconductor devices on a semiconductor wafer. More specifically, the disclosure relates to systems for plasma or non-plasma processing semiconductor devices.
In forming semiconductor devices, stacks are subjected to processing in a plasma processing chamber. Such chambers use RF power generators to create and maintain a plasma.
To achieve the foregoing and in accordance with the purpose of the present disclosure, a cooling apparatus is provided. At least one power electronic component is provided. A fluid tight enclosure surrounds the at least one power electronic component. An inert dielectric fluid at least partially fills the fluid tight container and is in contact with the at least one power electronic component.
In another manifestation, an apparatus for processing a substrate is provided. A processing chamber is provided. A substrate support supports a substrate within the processing chamber. A gas source is provided. A gas inlet is in fluid connection between the gas source and the processing chamber. A power source for provides RF power into the processing chamber, comprising RF power electronic components for providing RF power, and a cooling system for cooling the RF power electronic components, comprising a cooling chamber surrounding the RF power electronic components and a pump for circulating coolant within the cooling chamber.
These and other features of the present invention will be described in more details below in the detailed description of the invention and in conjunction with the following figures.
The present disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:
The present invention will now be described in detail with reference to a few preferred embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention.
In this embodiment, the pump 240 is a particle free pump, such as a magnetic levitation (maglev) pump. The inert dielectric fluid 228 is a fluorinated oxygen free fluid, such as Gladen® Heat Transfer Fluid HT 110 by Kurt J. Lesker Company, Jefferson Hills, Pa.
In operation, a substrate 104 is mounted on the ESC 108. A process gas is flowed from the gas source 110 into the processing chamber 149. The pump 240 pumps the dielectric fluid 228 from the fluid tight enclosure 204 through fluid outlet 232, the heat exchanger 244, and the temperature sensor 248 to the fluid inlet 236, which directs the dielectric fluid 228 back into the fluid tight enclosure 204. RF power is provided from the RF power source 130 to the ESC 108 to form the process gas into a plasma.
Gladen® Heat Transfer Fluid HT 110 is FM 6930 approved and provides sufficient cooling without damaging the RF power electronic components. The maglev pump 240 recirculates the dielectric fluid 228 without adding particulates, which could damage the RF power electronic components, by possibly shorting the components. In addition, the maglev pump is frictionless, which reduces heat generated by the pump. The heat exchanger 244 dissipates heat from the dielectric fluid 228. The temperature sensor 248 may be used to determine if the system is working properly. If there is component overheating due to a malfunction, smoking is prevented, because the dielectric fluid is oxygen free. The component may cause the dielectric fluid to vaporize, but would be smoke free, due to the lack of oxygen. The dielectric fluid has more than three times the heat conductivity of air, and prevents moisture from reaching the RF power electronic components. In addition, the dielectric fluid has a heat capacitance much higher than air. In this embodiment, the heat exchanger 244 uses Peltier cooling. Such Peltier cooling may use cooling fins. Cooling fans may be avoided, since fans may be a source of particle generation in a clean room. The use of a maglev pump and cooling fins for cooling instead of a cooling fan reduces noise. Since this embodiment is smoke free at failure, a higher power may be provided without the danger of creating smoke.
The direct contact between the dielectric fluid 228 and the RF power electronic components keeps the RF power electronic components sufficiently cool to prevent the RF power electronic components from smoking or failing. The presence of smoke during the plasma processing is a fire hazard and may create contaminants which would interfere with semiconductor fabrication.
Preferably, the fluid system is a sealed system. A diaphragm may be used to adjust for changing pressure. The level controller 224 may receive input from the temperature sensor 248 to shut down the system if the temperature is elevated above a threshold temperature, indicating a system failure.
Inert dielectric fluids have a high electrical resistivity and high dielectric strength. An inert dielectric fluid has a dielectric strength value of at least 106 V/m and electrical resistivity of at least 1010 ohm-cm.
Preferred embodiments use a single phase cooling process, since single phase cooling may be used to remove larger amounts of heat. In other embodiments, a micro electromechanical systems (MEMS) micropump may be used. In other embodiments, multiple inlets and/or multiple outlets may be used. In some embodiments, the controller may switch on the pump when a threshold temperature is measured. If a diaphragm is used, the diaphragm may be connected to a sensor. Preferably, the pump generates minimal particles. More preferably, the pump is particle free.
If the enclosure is fluid tight, the water 436 acts as a heat sink and limited heat exchanger. If the enclosure is not fluid tight, allowing vaporized water to escape, then the vaporizing water acts as a heat sink and more as a heat exchanger.
In other embodiments, the fluid may be a silicone oil or other dielectric fluid. Fluorinated fluids are preferred, because such fluids tend to be more inert. Oxygen free fluids prevent smoking. In some embodiments, the pump is immersed in the fluid in the fluid tight enclosure. In such a case, the fluid inlet and fluid outlet are in fluid connection with the fluid, although the fluid inlet and fluid outlet are not connected to an enclosure wall.
Other power electronic components may be used in other embodiments. Power electronic components are electronic components used in a power electronic assembly for generating RF or microwave signals for providing and/or sustaining a plasma, and AC and/or DC power supplies for ESC, Pedestals, and other high power supplies for components adjacent to and/or in a semiconductor processing chamber. Power electronic components may operate at temperatures above 90° C. A power electronic component is defined in the specification and claims as an electronic component that is able to operate at a high power of at least 100 Watts in a clean room environment, so that power electronic component is made to receive at least 100 Watts of power. The requirements for cooling power electronic components in a clean room for semiconductor manufacturing are different than the requirements for cooling a CPU or memory in a computer system. CPUs or memory in a computer system operates at temperatures below 50° C. Computer systems do not have the same particle generation limits required by a clean room. In addition, computer systems do not have the same heat transfer requirements as power electronic components. In other embodiments, the electronic components may be used in a non-plasma processing chamber.
In some embodiments, a cooling fluid flow rate above 0.31 m/s is preferred. More preferably, the flow rate is between 0.31 m/s and 0.96 m/s. Most preferably, the cooling fluid flow rate is sufficient to cause turbulent flow. Such a turbulent flow would occur at the above flow rate when the fluid Reynold's Numbers are greater than 4000. In addition, the power electronics preferably provide an irregular profile that further increased turbulence. For CPU and memory, which operate at lower temperatures, a slower flow rate is used to provide laminar flow, since in such situations laminar flow is more desirable.
While this invention has been described in terms of several preferred embodiments, there are alterations, modifications, permutations, and various substitute equivalents, which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, modifications, permutations, and various substitute equivalents as fall within the true spirit and scope of the present invention.
