JPH0533816B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a plasma processing apparatus and a plasma cleaning method, and more particularly to a plasma processing apparatus and a plasma cleaning method that utilize plasma to process, modify, or deposit a thin film on a sample. . [Prior art] There are various techniques and devices for turning gas into plasma under vacuum and utilizing the excellent properties of the plasma constituent species to process and modify the surface of a sample, or to deposit a thin film of a reactant on the sample. It has been put into practical use in the field. In particular, dry etching and vapor phase growth are used in the production of semiconductor devices (VLSI) because the plasma constituent species are suitable for microfabrication of samples, or because certain gases that have been turned into plasma are highly reactive. It has been adopted for thin film deposition and has now become an indispensable technology. Due to the high integration of VLSI, its patterns are becoming increasingly finer, and for example, the minimum processing size for 4M bit d-RAM has reached 0.7 to 0.8 μm. In such ultra-fine fields, dust is the enemy that controls the yield of VLSI manufacturing, and a clean environment is required. On the other hand, in dry etching equipment that processes semiconductor wafers or thin film deposition equipment that deposits reactants on wafers, reaction polymers from plasma gas, reaction products between plasma gas and wafer constituents, and wafer Alternatively, the actual situation is that debris etc. from substances exposed to plasma accumulate and adhere to the surface of the walls of the device. These deposits peel off from the component walls at some point and become dust that falls onto the wafer. Conventionally, in order to remove (so-called cleaning) the above-mentioned deposits, the lid of the processing apparatus is opened and the dust-proof cloth soaked in a chemical solution such as water, alcohol, or acetone is used to manually wipe off the deposits. This type of technology is discussed, for example, in Iida, "Chamber and Sample Contamination in RIE," Semiconductor World, pp. 127-132 (November 1984). [Problems to be Solved by the Invention] The frequency of cleaning varies depending on the material and processing dimensions of the sample, but in most cases it is necessary to perform it every several plasma treatments. In the above-mentioned conventional technology, this cleaning operation first involves stopping the processing equipment, breaking the vacuum of the equipment, and opening it to the atmosphere, so that the constituent materials of the processing equipment may adsorb atmospheric gases and moisture, or absorb moisture from the chemical solution. Because of the adsorption, it takes a long time to re-establish a vacuum state, reducing the operating rate of the processing equipment.Secondly, the adsorbed components on the equipment's constituent materials may slightly disturb the processing characteristics and impair the reproducibility of processing performance. I have a problem. The purpose of the present invention is to not reduce the operating rate, and
It is an object of the present invention to provide a plasma processing apparatus and a plasma cleaning method that can perform cleaning while maintaining good reproducibility of processing performance. [Means for solving the problem] The above object is to provide a plasma processing apparatus with a processing chamber configured to be able to reduce pressure, a means for introducing a sample processing gas or a cleaning gas into the processing chamber, and a means for introducing a sample processing gas or a cleaning gas into the processing chamber. The plasma cleaning method includes a pair of opposing electrodes provided in the sample, a high frequency power source for plasma generation, and means for connecting the two electrodes to the high frequency power source. A step of introducing a cleaning gas into a processing chamber which is internally subjected to plasma processing, and a step of connecting both of a pair of opposing electrodes provided in the processing chamber to a high frequency power source to generate plasma to clean the inside of the processing chamber. This can be achieved by using a method that includes a step of cleaning. [Operation] Electrically neutral molecules and radical species in an active state, electrons, and normally positively charged ion species are present in the plasma generated by glow discharge caused by the application of high-frequency power. Dry etching is mainly due to the reaction between radical species and ionic species, and is called reactive ion etching, especially when the active molecular region of the ionic species is an atomic ion.
It is called. When gas becomes plasma, a negative DC voltage is generated at the electrode to which high-frequency power is applied due to the difference in mobility between electrons and ions. Positively charged ions are accelerated by the electric field created by the negative DC voltage. Therefore, in Reactive Ion Etching, a wafer (sample) is placed on the electrode side to which high-frequency power is applied that generates a negative DC voltage, and the irradiation and reaction of ion species are utilized in addition to the reaction of radical species. In etching, in addition to etching due to the action of the radical species and ions, reaction polymers from the supplied gas and reaction products with the wafer as a sample are also deposited. Etching is a process in which the etching action is more dominant than the deposition action on the wafer, but in actual etching, deposits are observed in areas other than the wafer that are in contact with the plasma. These deposits occur in areas with little ion irradiation and are hardly observed in areas with high ion irradiation. The above phenomenon is thought to be due to the fact that deposits generated during etching are constantly irradiated with ions and are decomposed by spatter (deposit decomposition action of ions). For example, the surface of the electrode to which high-frequency power is applied is exposed to a large amount of ion irradiation due to the generation of the above-mentioned negative DC voltage, and there are very few deposits, but a lot of deposits are found on the counter electrode and processing chamber constituent walls, which are exposed to less ion irradiation. The outline of the present invention is to make active use of the deposit decomposition effect by ion irradiation described above, and to provide means for switching the connection between the high frequency power source and the electrode to any mode, and to remove the deposit after plasma processing for etching or thin film deposition. This involves switching the connection between the high-frequency power source and the electrode to generate plasma and decompose and remove the deposits. [Example] An example of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a diagram showing the cross-sectional structure and electrical system of the etching apparatus. Top lid 1-a, side wall 1-b,
An etching chamber 1 configured to be depressurized by a lower lid 1-c has a gas supply nozzle 2 for etching.
It has an exhaust nozzle 3 for pressure reduction, and a pair of opposing electrodes 4 and 5 are installed inside through airtight and electrical insulation mechanisms 6 and 7, respectively. The etching apparatus further includes a high frequency power source 8, a matching circuit 9, and a relay 10. The relay 10 has four contacts A, B, C, and D, and has a function of connecting and disconnecting each contact. The upper electrode 4 of the opposing electrodes is connected to the contact A, the lower electrode 5 is connected to the contact B, and the high frequency power source 8 is connected to the matching circuit 9 to the contact C.
The contact D is connected to ground. Here, the relay 10 is capable of the connection modes shown in the table below.

〔Effect of the invention〕

As described above, according to the present invention, since the processing equipment can be cleaned in a dry state without being exposed to the atmosphere, the operating rate of the equipment can be increased, and
This has the effect of maintaining good reproducibility of processing characteristics. In particular, the cleaning speed is improved not only for the upper and lower electrodes but also for deposits on the walls of the etching chamber.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an etching device showing an embodiment of the present invention, FIGS. 2 to 4 are connection mode diagrams of a relay in the device of FIG. 1, and FIGS. 5 to 7 are:
FIG. 3 is a configuration diagram of an etching apparatus showing another embodiment of the present invention. 1... Processing chamber, 4, 5... Electrode, 8... High frequency power supply, 10... Relay.

Claims (1)

[Scope of Claims] 1. A processing chamber configured to be able to reduce pressure, means for introducing sample processing gas or cleaning gas into the processing chamber, a pair of opposing electrodes provided in the processing chamber, and a plasma A plasma processing apparatus comprising: a high-frequency power source for generation; and means for connecting both of the pair of electrodes to the high-frequency power source. 2. A switching means in which the connecting means can switch between a state in which both of the pair of electrodes are connected to the high frequency power source, and a state in which one of the pair of electrodes is grounded and the other is connected to the high frequency power source. A plasma processing apparatus according to claim 1, characterized in that it has the following. 3. Introducing a cleaning gas into a processing chamber that is configured to be able to reduce pressure and in which a sample is subjected to plasma treatment, and connecting both a pair of opposing electrodes provided in the processing chamber to a high frequency power source to generate plasma. and cleaning the inside of the processing chamber by generating plasma.