JPS62256431A - Method and apparatus for plasma treatment of semiconductor substrate - Google Patents

Abstract

PURPOSE:To facilitate a high quality plasma treatment reducing damage such as breakdown of an insulating film by a method wherein an auxiliary electrode which can be withdrawn from and inserted into a treating chamber is provided close to an anode or a cathode in the treatment chamber and the plasma treatment is applied to a semiconductor substrate by a means which does not give damage to the substrate surface after the treatment of the semiconductor substrate comes close to finish. CONSTITUTION:If a radio frequency output is gradualy increased, a plasma state is spread in a whole treatment chamber (quartz chamber) 1. At that time, the plasma intensity is especially high between an auxiliary electrode 4 and an anode 2 and the plasma state is not uniform. Therefore, if the condition is realized under which the discharge can be maintained without the auxiliary electrode 4, the auxiliary electrode 4 is retreated to the position where the auxiliary electrode 4 has no effect on the discharge by the operation of a driving means 7. With this constitution, the breakdown phenomenon of an insulating film caused by a high voltage induced at the time of the closing of a radio frequency source can be avoided. Further, after the treatment of a semiconductor substrate comes close to finish of treatment, a plasma treatment is applied to the semiconductor substrate by a means which does not give damage to the semiconductor substrate surface.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a processing technology that uses plasma to perform ashing, etching, film formation, etc. This article relates to techniques useful for plasma processing in the field.

As is well known, in recent years, a dry processing process has become an essential technology for manufacturing highly integrated semiconductor devices, and processing using plasma is frequently used in this processing step.

[Conventional technology]

By the way, semiconductor substrate processing equipment using plasma mainly includes barrel (cylindrical) type equipment and parallel plate type equipment, and these equipment maintains a predetermined degree of vacuum inside the processing chamber and introduces processing gas. , a high-frequency power is applied between the anode and cathode to cause a plasma discharge between the electrodes, and processing such as ashing is performed using the reactive gas excited by this discharge, but the conventional woodcutter plasma processing apparatus In this case, the cause of damage to the semiconductor substrate was included.

In other words, as shown in Figure 4, when the high-frequency power is turned on, the electrical resistance is extremely high because the processing chamber is not in a plasma state, and therefore a high voltage must be applied between the electrodes in order to start the discharge. No. Once the discharge is started, the impedance between the electrodes decreases and the voltage also decreases to a constant value.Also, even when the high frequency dragon source is switched off, a high voltage is generated when the plasma disappears.

In this way, high voltage is generated when high-frequency power is turned on and S is turned off, and this high voltage can destroy thin insulating films (SzO, L, etc.), and can also damage the final stage of semiconductor substrate processing. When the photoresist on the substrate surface begins to disappear, the metal components in the photoresist are struck by high-speed particles accelerated in the electric field and invade the substrate surface, contaminating the substrate and impairing the performance of the semiconductor device. If the photoresist on the substrate surface begins to disappear and the insulating film is directly exposed to plasma, the KJ will gradually deteriorate.
If charge accumulates in the edge film and exceeds a limit, damage such as destruction of the insulating film occurs, and this damage deteriorates the electrical characteristics and yield of the semiconductor device.

[The problem that the invention attempts to solve]

As described above, processing using a conventional plasma processing apparatus causes a lot of damage to the substrate.

The present invention was made in view of these conventional problems, and its purpose is to provide a semiconductor substrate that enables high-quality plasma processing by reducing damage such as breakdown of the insulation film of the semiconductor substrate. An object of the present invention is to provide a plasma processing method and an apparatus thereof.

[Means for solving problems]

For this purpose, the present invention provides an auxiliary electrode in the processing chamber that is close to one of the anodes and cathodes and that can be taken in and out of the processing chamber. It is characterized by stabilizing the state and performing plasma processing on the semiconductor substrate from the time when the temperature reaches K near the processing end point of the semiconductor substrate by means such as lowering the space potential in the processing chamber so as not to damage the semiconductor substrate surface. It is something.

〔Example〕

Hereinafter, a preferred embodiment of the present invention will be described based on the drawings.

1 and 2 show an example of the apparatus of the present invention, in which an auxiliary electrode 4 is installed in a quartz chamber 1, which is a plasma processing chamber, at either an anode 2 or a cathode 3 (in this embodiment, an anode 2 ), and is provided so that it can be taken in and out from inside the quartz chamber 1.

That is, a quartz pipe 5 is airtightly inserted into the quartz chamber 1 from the outside in the axial direction approaching the anode 2, and the auxiliary electrode 4 is inserted into the quartz pipe 5 with the guide and sealing member 6. It is provided so as to be movable back and forth horizontally via a drive means 7 such as a cylinder and horizontally in the direction of the arrow.

The interior of the quartz pipe 5 is preferably in a vacuum state, and the auxiliary electrode 4 is electrically grounded.

In such a plasma processing apparatus, a high frequency power source 80
At the time of injection, the auxiliary electrode 4 is inserted into the quartz pipe 5 through the operation of the driving means 7. Then, since the auxiliary electrode 4 and the anode 2 are close to each other, discharge is started at a low voltage and can be maintained. Next, by gradually increasing the high frequency output,
The entire inside of the processing chamber (quartz chamber 1) is in a plasma state. At this time, the plasma becomes especially strong between the auxiliary electrode 4 and the anode 2, resulting in a non-uniform plasma state, so when the state where the discharge can be maintained even without the auxiliary electrode 4 is reached, the operation of the driving means 7 is stopped. auxiliary electrode 4 is retracted to a position unrelated to discharge.

This makes it possible to prevent breakdown of the insulating film due to the high voltage that occurs when the high frequency power source 8 is turned on.

Furthermore, when the high-frequency power source 8 is cut off, the auxiliary electrode 4 is advanced into the quartz chamber 1 through the operation of the driving means T, and after the auxiliary electrode 4 is brought close to the anode 2 to maintain the plasma state, the high-frequency The output is gradually lowered and when the output has decreased sufficiently, the high power supply 8 is shut off. As a result, the level of high voltage generated during RFMr of the high frequency power source 8 can be lowered, and breakdown of the insulating film can be prevented.

As described above, according to the apparatus of the present invention, the plasma state in the processing chamber is stabilized when the high-frequency sleep source is turned on and off, and insulation film breakdown phenomenon due to high voltage is prevented. In this method, in order to prevent damage such as substrate contamination caused by metal components in the photoresist, plasma processing is performed on the semiconductor substrate by a method that does not damage the semiconductor substrate surface after the semiconductor substrate is near the end of processing. ing.

Specifically, the approach of the processing end point of the semiconductor substrate is detected by the following method.

That is, ■ one that detects the emission spectrum. ■Measure the film thickness using a laser beam, etc. ■ Detect changes in voltage between electrodes. ■ Insert a glove into the processing chamber and measure changes in space potential. ■ Other methods that do not detect changes in film thickness.

After the above method approaches the end point of the process, the high frequency output is lowered to a certain level or below using means that will not damage the substrate surface. In other words, by lowering the space potential in the processing chamber, the activity of high-speed particles can be suppressed to a level where they are no longer affected, and it is possible to prevent substrate contamination by metal components in the photoresist.
Accumulation of charges in the insulating film of the substrate can be suppressed, and breakdown of the insulating film of the substrate can be prevented.

The above method is shown in Figure 3, Figure 81.

In addition to the method of lowering the high frequency output below a certain level as described above, there are other methods to prevent damage to the semiconductor substrate surface, such as lowering the degree of vacuum in the processing chamber, using ozone gas, and using light such as laser/ultraviolet light. Excite the processing gas,
There are methods such as processing by dissociation and other methods that do not use an electric field, and any of these methods can achieve the same effects as above, namely preventing contamination of the substrate surface and preventing the phenomenon of insulation film breakdown. It is possible.

Note that the above-mentioned processing means used after the point near the end point of substrate processing generally has a drawback that the processing rate (speed) is slow; Since this is a processing stage, the thickness of the film to be processed is extremely thin, and at this point, the surface of the film to be processed is sufficiently activated to be easily processed. Therefore, even if the processing rate is somewhat slow, the decrease in substrate processing efficiency with respect to the overall processing time is slight, and there is no practical problem.

Although the above embodiments have been described with reference to a barrel (cylindrical) type processing apparatus, the present invention is not limited thereto, and can of course be applied to a parallel plate type or other plasma processing apparatus.

〔Effect of the invention〕

As is clear from the detailed description above, according to the present invention, the auxiliary electrode is provided in the processing chamber close to either the anode or cathode and can be taken in and out of the processing chamber. and high 1 that occurs when shutting off.
It is possible to avoid destruction of the insulating film of the semiconductor substrate due to pressure, and plasma processing is performed after the semiconductor substrate is near the end of processing using a method that does not damage the substrate surface. , it is possible to avoid contamination of the substrate surface as well as the breakdown circuit of the insulating film, and realize a semiconductor device manufacturing process with high yield.
Its industrial value is remarkable

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are schematic diagrams showing an example of the present invention, the third cause, (Bl is a characteristic diagram showing the relationship between the detection point at the time when the processing end point of the semiconductor substrate approaches and the level down of the high frequency output; Fig. 4 is an explanatory diagram showing the time change of the voltage between anode and cathode. 1... Processing chamber 2... Anode 3... Cathode 4... Auxiliary electrode 5... Quartz pipe 7... Drive means 8 - Fist high frequency power supply

Claims (1)

[Claims] 1. In the processing chamber, close to either the anode or cathode,
In addition, the plasma state inside the processing chamber is stabilized when the high-frequency power is turned on and off through an auxiliary electrode that can be taken in and taken out of the processing chamber, and the space inside the processing chamber is stabilized from the point near the end point of semiconductor substrate processing. A plasma processing method for a semiconductor substrate, characterized by subjecting the semiconductor substrate to plasma processing by means such as lowering the potential that does not damage the surface of the semiconductor substrate. 2. In the processing chamber, an auxiliary electrode for stabilizing the plasma state in the processing chamber when turning on and off the high-frequency power source is provided close to either the anode or cathode and can be taken in and out of the processing chamber. Plasma processing equipment for semiconductor substrates.