Patent Application
20050161321
This invention relates to an apparatus that is disposed in the gas supply system of a semiconductor processing system and that generates and supplies fluorine gas. Semiconductor processing refers in this context to the various processes carried out in order to fabricate semiconductor devices and/or semiconductor device-connecting structures (e.g., interconnects, electrodes) on the substrate undergoing the processing (the target substrate) by the formation of semiconductor, dielectric, and conductive layers in specific patterns on the target substrate, such as a semiconductor wafer or LCD substrate.
A variety of semiconductor processes, such as film formation, etching, and diffusion, are carried out on the target substrate, e.g., a semiconductor wafer or LCD substrate, during the fabrication of semiconductor devices. The semiconductor processing systems used to carry out these treatments employ fluorine-type gases as process gases in a variety of applications, such as for the etching of silicon films and silicon oxide films or to clean the interior of process compartments, which are not necessarily limited to semiconductor processes.
Fluorine-type process gases are generally made available to the gas supply system of a semiconductor processing system as an already prepared fluorine compound filled in a cylinder. Gases of this type are seldom produced on-site from their essential precursors, e.g., fluorine. The reasons for this relate not just to problems with the reliability of the gas composition, but also to the extreme danger associated with placing a cylinder filled to high pressures (typically at least 5 kg/cm2) with a strong oxidizer such as fluorine in the gas supply system of a semiconductor processing system.
U.S. Pat. No. 5,688,384, on the other hand, discloses an apparatus that automatically controls the on/off switching of fluorine gas generation in response to demand. As its fluorine gas generation module this apparatus uses an electrolytic cell that generates fluorine gas by the electrolysis of hydrogen fluoride. Since such electrolytic-type apparatuses can as necessary produce fluorine gas at near atmospheric pressure, they can avoid the safety problems associated with the installation of fluorine cylinders.
Problems to Be Solved by the Invention
When a fluorine gas-generating and -supply apparatus as described above is placed in the gas supply system of a semiconductor processing system, it is also necessary to provide a back-up means in order to prevent perturbations in the operation of the main processing apparatus even when abnormalities occur in the fluorine gas-generating and -supply apparatus. In a typical strategy, two fluorine gas-generating and -supply apparatuses are installed in a gas supply system and are operated in rotation as the online apparatus and back-up apparatus. This back-up strategy, however, causes high initial costs and high operating costs for the gas supply system. Moreover, while fluorine cylinders can also be used as a back-up means, safety problems are incurred by the disposition of high-pressure fluorine cylinders in the gas supply system of a semiconductor processing system.
This invention was developed in view of the problems identified above for the prior art. The object of this invention is to provide a fluorine gas-generating and -supply apparatus that is disposed in the gas supply system of a semiconductor processing system and that in the event of abnormalities in the apparatus enables back up by a safe and inexpensive structure.
A particular object of this invention is to provide an apparatus that can generate and supply fluorine gas both on-site and on-demand. As used herein, on-site means that the mechanism for generating and supplying the fluorine gas is combined or assembled with the particular main process apparatus, for example, the main process apparatus of a semiconductor processing system. On-demand means that the gas can be supplied, with accompanying control of its required components, with a timing that responds to the requirements of the main process apparatus.
Means Solving the Problems
The first aspect of this invention is an apparatus that generates and supplies fluorine gas and is disposed in the gas supply system of a semiconductor processing system, said apparatus being characteristically provided with
The second aspect of this invention is an apparatus in accordance with the first aspect with the additional characteristic feature that the electrolytic cell detector detects a state that is representative of the composition of the electrolytic bath.
The third aspect of this invention is an apparatus in accordance with the second aspect with the additional characteristic feature that the electrolytic cell detector detects a state selected from the electrical current characteristics, liquid level, and temperature of the electrolytic bath.
The fourth aspect of this invention is an apparatus in accordance with any of the first to third aspects, characterized in that the apparatus is additionally provided with a path detector that can detect an abnormal state in the gas supply path that supplies fluorine gas from the electrolytic cell to the gas utilization section and in that the controller, upon detection of an abnormal state at the electrolytic cell by the electrolytic cell detector or upon detection of an abnormal state in the gas supply path by the path detector, exercises control on the gas switching section so as to feed the substitute gas from the cylinder to the gas utilization section.
The fifth aspect of this invention is an apparatus that generates and supplies fluorine gas and is disposed in the gas supply system of a semiconductor processing system, said apparatus being characteristically provided with
The sixth aspect of this invention is an apparatus in accordance with the fourth or fifth aspect, characterized in that the gas supply path is provided with a buffer section that controls the pressure and flow rate of the fluorine gas that is supplied from the electrolytic cell to the gas switching section and in that the path detector is provided with a buffer detector that detects the state of the buffer section.
The seventh aspect of this invention is an apparatus in accordance with the sixth aspect, characterized in that the buffer section is provided with a compressor that pressurizes the fluorine gas from the electrolytic cell and in that the buffer detector detects the operational status of the compressor.
The eighth aspect of this invention is an apparatus in accordance with the sixth aspect, characterized in that the buffer section is provided with a buffer tank that temporarily stores fluorine gas from the electrolytic cell and in that the buffer detector detects the pressure within the buffer tank.
The ninth aspect of this invention is an apparatus in accordance with the sixth aspect, characterized in that the buffer section is provided with a flow controller that supplies fluorine gas from the electrolytic cell to the gas switching section at a specified flow rate and in that the buffer detector detects the fluorine gas flow rate at said flow controller.
The tenth aspect of this invention is an apparatus in accordance with any of the first through ninth aspects, characterized in that the substitute gas comprises chlorine fluoride.
In addition, the embodiments of this invention explore a variety of executions of this invention, and various embodiments of this invention can be derived by suitable combination of the plural number of disclosed constituent elements. For example, when an embodiment of the invention has been derived in which some constituent elements have been omitted from the overall set of constituent elements presented for the embodiment, these omitted elements can be suitably fulfilled by conventional well-known technologies in the actual working of the derived inventive embodiment.
Embodiments of this invention are explained in the following with reference to the drawings appended herewith. In the explanation that follows, those constituent elements that have approximately the same structure and function are assigned a common reference symbol and their explanation will be repeated only when necessary.
The semiconductor processing apparatus 10 is provided with a process chamber 12 that holds the target substrate and in which the semiconductor process is implemented. Disposed within the process chamber 12 is a mounting platform 14 (support member) that functions both as a lower electrode and as a platform for mounting the target substrate. An upper electrode 16 is also disposed within the process chamber 12 facing the mounting platform 14. RF (high frequency) power can be applied from an RF power source 15 across the two electrodes 14 and 16 in order to form an RF field in the process chamber 12 for the purpose of converting the process gas into a plasma. An exhaust system 18 is connected to the lower region of the process chamber 12 for the purpose of evacuating the interior of the chamber and establishing a vacuum therein. A gas supply system 20 is connected to the upper region of the process chamber 12 for the purpose of supplying the process gas.
With reference again to
An inventive apparatus 30 for the generation and supply of fluorine gas is connected in the embodiment under consideration to the flow management section 22 and the gas production section 26. More specifically, this generation and supply apparatus 30 either directly supplies fluorine gas to the flow management section 22 or is used to supply starting fluorine gas to the gas production section 26 (switching valve not shown). The gas production section 26 can produce, for example, an interhalogen fluorine compound gas by reacting the starting fluorine gas with another halogen gas such as chlorine.
The generation and supply apparatus 30 contains an electrolytic cell 34 that generates fluorine gas (F2) by the electrolysis of hydrogen fluoride in an electrolytic bath comprising hydrogen fluoride-containing molten salt. This molten salt comprises a mixture (KF/2HF) of potassium fluoride (KF) and hydrogen fluoride (HF) or a mixture of hydrogen fluoride and Fremy's salt. The electrolytic cell 34 is connected to a hydrogen fluoride source 32 that supplies hydrogen fluoride, the starting material that undergoes depletion. A detector 36 is disposed within the electrolytic cell 34 for the purpose of detecting, as a state representative of changes in the composition of the electrolytic bath, the electrical current characteristics, liquid level, temperature, etc., of the electrolytic bath. The detection results generated by the detector 36 are fed to a controller 40. The electrolytic cell 34 is replenished with hydrogen fluoride—the consumable starting material—from the hydrogen fluoride source 32 based on the detection result yielded by the detector 36 and under control by the controller 40 using a quantitative threshold value as the criterion.
The fluorine gas generated by the electrolytic cell 34 is fed to a gas switching section 56 across a buffer section 42; the purpose of the buffer section 42 is to control the pressure and flow rate of the fluorine gas present in the supply conduit 38. This buffer section 42 is provided with a compressor 44 in order to pressurize the fluorine gas generated at substantially atmospheric pressure at the electrolytic cell 34, a buffer tank 46 that temporarily holds the fluorine gas, and a flow controller 48 that feeds fluorine gas from the buffer tank 46 to the gas switching section 56 at a specified flow rate. An operations detector 50 is disposed at the compressor 44 in order to detect the operational status of the compressor 44. A pressure detector 52 is disposed at the buffer tank 46 in order to detect the pressure within the buffer tank 46. A flow rate detector 54 is disposed at the flow controller 48 in order to detect the flow rate of the fluorine gas in the flow controller 48. The detection results generated by these detectors 50, 52, and 54 are fed to the controller 40.
A back-up section 60 is provided against the contingency of the appearance o-f abnormalities in the electrolytic cell 34 (fluorine gas generator), supply conduit that runs from the electrolytic cell 34 to the gas utilization section, or fluorine gas supply path (including the buffer section 42). This back-up section 60 is provided with a cylinder 62 (or cylinder group) that holds the substitute gas used as a fluorine gas substitute. The substitute gas exiting the valve 64 of the cylinder 62 is supplied, adjusted to a specified flow rate by the flow controller 66, to the gas switching section 56.
The substitute gas is selected from the group consisting of nitrogen fluoride, sulfur fluoride, and chlorine fluoride. Among these, the use of nitrogen fluoride as the substitute gas is particularly desirable due to its low reactivity at room temperature and because it is a relatively safe gas. When nitrogen fluoride (NF3) is used as the substitute gas, it will be desirable to configure the flow controller to automatically bring the nitrogen fluoride flow rate to approximately two-thirds the fluorine flow rate when a switch is made from fluorine gas to nitrogen fluoride. This configuration can maintain a constant processing capacity at the location where the substitute gas is used. The preferred substitute gas will also vary as a function of the type of process and the nature of the semiconductor processing apparatus. For example, nitrogen fluoride (NF3) is preferably used as the substitute gas in the case of plasma cleaning while chlorine fluoride is preferably used as the substitute gas in the case of thermal cleaning.
The controller 40 controls the gas switching section 56 in such a manner that substitute gas is supplied to the gas utilization section (the main process facility) from the cylinder 62 when an abnormal state is detected in the electrolytic cell 34 and/or in the buffer section 42. Accompanying this gas switching at the gas switching section 56, the controller 40 also adjusts the status of the valve 64 on the cylinder 62 and adjusts the ON/OFF status of the operation of the buffer section 42 (for example, the operation of the compressor 44).
An abnormal state in the electrolytic cell 34 is sensed by the electrolytic cell detector 36. In specific terms, the detector 36 detects, for example, the electric current characteristics, liquid level, or temperature of the electrolytic bath as a state representative of changes in the composition of the electrolytic bath and transmits the result to the controller 40. The controller 40 then compares the detected value with a preliminarily set threshold value and determines whether the electrolytic bath 34 resides in a normal state or has entered into an abnormal state.
Likewise, an abnormal state at the buffer section 42 is detected by means of three detectors making up the buffer detector, i.e., the operations detector 50, the pressure detector 52, and the flow rate detector 54. In specific terms, these detectors 50, 52, and 54 detect, respectively, the operational status of the compressor 44, the pressure within the buffer tank 46, and the fluorine gas flow rate at the flow controller 48, and transmit their results to the controller 40. The controller then compares these detected values with preliminarily set threshold values and determines whether the buffer section 42 resides in a normal state or has entered into an abnormal state.
Thus, the detectors 36, 50, 52, and 54 are respectively disposed in each of the main constituent members on the fluorine gas generation and supply side, which enables the location and type of an abnormal state on the generation and supply side to be recognized by the controller 40. This enables the controller 40 to carry out, in correspondence to the location and type of an abnormal condition, a variety of information processing in connection with control of the gas switching section 56, including, for example, the decision on the timing of gas switching, the execution prior to gas switching of a program that checks the status of each main constituent member, transmission of an alarm signal that alerts the operator of the location, etc., of the abnormal state, and a manual operation indication.
The generation and supply apparatus 30 shown in
An abnormal state at the electrolytic cell 34 will generally also cause an abnormality or perturbation in the status of the generated fluorine gas. As a consequence, the basic information necessary for controlling the gas switching section 56 can be obtained by sensing an abnormal state in the gas supply path that supplies fluorine gas from the electrolytic cell 34 to the gas utilization section, for example, an abnormal state for the fluorine gas in the downstream buffer section 42. However, in this case it will be desirable to have enabled a separate sensing of any abnormal state at the electrolytic cell 34 unrelated to control of the gas switching section 56.
An abnormal state in the buffer section 42 will generally also cause an abnormal state or condition in the pressure and flow rate in the fluorine gas supply conduit. As a consequence, the basic information necessary for controlling the gas switching section 56 can be obtained by sensing an abnormal state in the pressure and flow rate within the fluorine gas supply conduit downstream from the buffer section 42.
The gas switching section 56 may also be disposed between the electrolytic cell 34 and the buffer section 42 in each of the embodiments discussed above. In such a case the controller 40 will exercise control on the gas switching section 56 with reference only to the detection result afforded by the detector 36 for the state of the electrolytic cell 34. Moreover, while the fluorine gas is fed either to the flow management section 22 or to the gas production section 26 in the embodiments discussed above, this gas can be supplied directly to the process chamber 12 separately from other process gases. The gas production section 26 can also be configured to produce other fluorine-type process gases instead of interhalogen fluorine compound gases. A cylinder of fluorine gas can be used in each of the embodiments elaborated hereinabove in place of the cylinder of substitute gas insofar as the corresponding safety issues can be resolved.
While various modifications and alterations within the technical sphere of the concept of this invention can be devised by the individual skilled in the art, it should be understood that such modifications and alterations also fall within the scope of this invention.
Advantageous Effects of the Invention
As has been described in detail hereinabove, this invention provides a fluorine gas-generation and -supply apparatus that is disposed in the gas supply system of a semiconductor processing system and that in the event of abnormalities in the apparatus enables back up by a safe and inexpensive structure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2001/397278 | Dec 2001 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP02/14909 | 12/20/2002 | WO |
