JPH08250293A - Plasma treatment apparatus and control method - Google Patents

Abstract

PURPOSE: To install a plasma resistant wall inside a plasma treatment apparatus and stabilize plasma treatment properties by controlling the temperature of the plasma resistant wall. CONSTITUTION: Heating is controlled by far infrared-rays 9 which hardly passes a plasma resistant wall 8. The far infrared-rays 9 are radiated from a coating film made of a far infrared-ray radiating material, such as alumina, formed in a treatment chamber inner wall. The temperature control of the coating film is carried out by temperature adjustment of a treatment chamber block and the temperature for control is set to be the temperature of the plasma resistant wall measured by infrared ray thermometers 12, 20 through a window 19 made of silicon. Since the temperature control of the plasma resistant wall can be carried out highly precisely, plasma treatment can be carried out stably. Consequently, production yield and operation efficiency can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to stabilize the plasma processing by controlling the temperature of a plasma resistant wall installed inside the processing chamber of a plasma processing apparatus such as a microwave etching apparatus. The present invention relates to a plasma processing apparatus suitable for an apparatus whose plasma processing characteristics are easily influenced by the temperature of a processing chamber and a control method thereof.

[0002]

2. Description of the Related Art Taking an example of a conventional plasma processing apparatus in which the temperature of a processing chamber is controlled, the plasma processing chamber is constructed as a vacuum chamber.
As described in Japanese Patent No. 181, the wall surface of the processing chamber, that is, the vacuum container is heated from the atmosphere side by a heater to control the temperature,
As disclosed in Japanese Examined Patent Publication No. 6-8510, a method is adopted in which a cooling water flow path is provided on the atmosphere side of the processing chamber, or a refrigerant flow path is provided and a refrigerant is separately controlled by a temperature control unit. ing.

[0003]

Although the above-mentioned conventional method is sufficient for controlling the temperature of the wall surface, it controls the temperature of another member installed in the plasma processing chamber, for example, a dustproof wall or a plasma resistant wall. In order to do so, the inside of the plasma processing chamber is in a vacuum heat insulation state, which is insufficient. Therefore, usually, even if such an internal member is installed, the temperature control is not actively performed, and it is often utilized that the wall surface temperature is stabilized by the temperature rise by plasma. In particular, when the member installed inside is consumable and must be replaced regularly, it is difficult to implement a method such as providing a heater or a flow path for the refrigerant in the member considering the maintainability. was there.

It is also known that the plasma changes when the wall temperature of the plasma processing chamber changes. For example, the plasma processing apparatus controls the pressure of the processing gas in order to stabilize the plasma processing characteristics. However, when the temperature changes, the density changes and the plasma state changes even if the pressure is constant. Furthermore, ions and radicals in the plasma, processing gas, reaction products, etc. are incident on the wall surface, but the reaction, deposition, and desorption of these incident particles on the wall surface are affected by the wall surface temperature. When it changes, a phenomenon such as a change in plasma composition occurs. This phenomenon is, for example, Y. Hirosaka, et al .: Free Radicals
in an Inductively Coupled Etching Plasma: Jpn.JA
ppl.Phys., Vol.33 (1994) pp.2157-2163.

An object of the present invention is to provide a plasma processing method and apparatus for stabilizing the plasma processing characteristics by making the material of the plasma processing chamber excellent in plasma resistance and controlling the temperature with high accuracy. To provide.

[0006]

SUMMARY OF THE INVENTION The present invention controls the temperature of an internally installed member without attaching a special temperature control device to the member installed inside. Heat transfer in vacuum is mainly radiant heat transfer. Therefore, assuming a case where a plasma resistant wall surface close to the wall surface of the processing chamber is provided inside the plasma processing chamber, a heater provided outside the wall temperature of the plasma processing chamber facing the plasma resistant wall surface to control the temperature of the plasma resistant wall surface. The temperature of the plasma resistant wall surface can also be controlled by radiant heat transfer. However, when quartz is used as the plasma resistant wall surface, the heating efficiency is extremely poor because the quartz transmits infrared rays by ordinary radiant heating. Therefore, in the present invention, far infrared rays that can efficiently heat materials such as quartz are used. A material that easily emits far infrared rays, such as alumina, is formed on the inner wall surface of the plasma processing chamber to control the temperature of the inner wall surface of the plasma processing chamber. As a result, the temperature of the plasma-resistant wall surface installed inside is efficiently controlled by far infrared rays emitted from the wall surface of the plasma processing chamber.

Further, in order to heat and control the temperature of the plasma resistant wall, the temperature must be detected, but contact type sensors such as thermocouples and fluorescent thermometers are difficult to use in plasma. An infrared radiation thermometer is suitable for the purpose of the invention, but if the plasma resistant wall is quartz and the temperature measurement window is quartz,
I cannot make correct measurements. The measurement wavelength range of the infrared thermometer
The long-wavelength range, which cannot pass through quartz, allows the temperature measurement window to pass through, making it possible to measure non-contact temperature with an infrared thermometer.

[0008]

According to the present invention, the temperature of the wall surface of the plasma processing chamber can be easily controlled by a heater or a refrigerant passage provided on the atmosphere side,
Thereby, the temperature of the inner wall surface of the plasma processing chamber is controlled, and far infrared rays corresponding to the temperature are radiated. The far infrared rays efficiently control the heating of the wall surface provided inside the plasma processing chamber regardless of the material. Therefore, the plasma state is also kept stable, and the characteristics of the object to be treated which has been subjected to the plasma treatment are also stabilized.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described by taking a microwave plasma etching apparatus as an example. FIG. 1 shows a microwave plasma etching apparatus embodying the present invention. FIG.
At, the microwave passes through the waveguide 5 and the quartz window 1 and is introduced into the plasma processing chamber 2 to generate plasma.
A wafer 3 for performing plasma processing (here, etching) is placed on the electrode 4. Although not shown here, a high frequency power source is connected to the electrode 4 so that a bias for attracting ions from the plasma can be applied.
Further, in order to control the temperature of the wafer 3, it is possible to control the temperature of the electrode 4 with a coolant.
Temperature control is performed by introducing helium gas on the back surface of the to improve heat transfer efficiency. Although not shown in the figure, the etching gas is supplied from, for example, a gas inlet provided directly below the quartz window, and the etching reaction products and excess gas are exhausted from the plasma processing chamber through a vacuum pump. It A coil 6 for generating a magnetic field for resonance absorption of microwaves by electron cyclotron resonance (ECR) is installed around the plasma processing chamber 2.

In the present invention, the container wall 7 of the plasma processing chamber 2 is
A far-infrared film made of a material (alumina, silicon oxide, silicon carbide, etc.) that easily emits far-infrared rays on the surface of the container wall 7 facing the plasma-resistant wall 8 is installed in proximity to the plasma-resistant wall 8 made of quartz. 9 is formed, the container wall 7
A heater 10 is provided on the atmosphere side. When the temperature of the container wall 7 is controlled by the heater 10, the temperature of the far infrared ray film 9 formed on the container wall 7 is also controlled. Furthermore, the far infrared rays emitted from the far infrared film 9 heat the plasma resistant wall 8 and control the temperature thereof. For reference, FIG. 4 shows the wavelength dependence of the transmittance of quartz and the emissivity of alumina as an example of a material that easily emits far infrared rays. It can be seen that the emissivity of alumina is large in the wavelength range that does not pass through quartz, and that quartz efficiently absorbs far infrared rays and is heated. In the examples described below, mainly the heating control of the plasma resistant wall 8 (higher than room temperature or a temperature equal to or higher than the temperature at which the plasma resistant wall 8 is heated by plasma) is shown, but the plasma resistant wall 8 has a high temperature. In this state, it is possible to construct a process even in the state, and by maintaining the plasma-resistant wall 8 at a high temperature, it is possible to suppress the growth of the deposition film on the wall surface, and it is also possible to prevent the generation of foreign matter due to the removal of the deposition film. There is no particular problem with the device. However, since the plasma resistant wall 8 can be cooled by lowering the temperature of the container wall 7, the heating control method is the same when the plasma resistant wall 8 is cooled to a low temperature. In that case,
A refrigerant flow path is provided on the container wall 7 to control the refrigerant temperature by the refrigerator. Furthermore, when only the plasma resistant wall 8 needs to be cooled, it is effective to make the material of the container wall 7 excellent in absorption characteristics in the radiation wavelength range of the plasma resistant wall 8 (here, quartz). is there. For example, it is effective to form alumina on the container wall 7.

Now that the basic principles of the invention have been set forth above, an example of use of the invention will now be described. Since the conventional apparatus does not have a temperature adjusting function of the plasma resistant wall 8, the temperature of the plasma resistant wall 8 is raised and stabilized by performing preliminary discharge before the plasma treatment. Next, the plasma discharge is stopped and a new wafer to be processed is loaded and placed on the electrode 4. After that, the plasma treatment is promptly performed before the temperature of the plasma resistant wall 8 decreases. When the next wafer to be processed is etched, the time required from the unloading of the previous wafer to be processed to the loading of the next wafer to be processed is short, so the temperature drop of the plasma resistant wall 8 is small, and the above-described preliminary discharge is performed. You don't have to. In this way, 1 lot (usually 25)
Etching is completed. If the time to move to the next lot is short, pre-discharge is not necessary. However, when the plasma discharge stop time becomes long, preliminary discharge becomes necessary. Further, since the plasma discharge is stopped during the loading and unloading of the wafer, the temperature of the plasma resistant wall 8 is lowered.
If the etching characteristics are affected by the temperature drop during this period, temperature stabilization by preliminary discharge is also ineffective.
The conventional method cannot stabilize the etching characteristics. The results of measuring the temperature of the plasma resistant wall 8 in the above steps are shown in FIG. In FIG. 2, the temperature of the plasma resistant wall 8 rapidly rises at the same time as plasma generation. After a while, the rate of temperature rise slows and gradually stabilizes at high temperature. Although the temperature slightly drops during wafer loading and unloading, the temperature remains stable.

On the other hand, according to the present invention, the heater 10 is energized and heated to raise the temperatures of the container wall 7, the far infrared ray film 9 and the plasma resistant wall 8 to be constant before performing the etching process. When the plasma processing is started, the plasma resistant wall 8 is also heated by the plasma, so that the current supplied to the heater 10 is suppressed to a small value. At this time, the temperature of the plasma resistant wall 8 is monitored by the method shown in FIG.
Controls the output of 0. Further, in order to further improve the temperature controllability, a cooling medium passage may be provided in the container wall 7 to allow cooling. By doing so, the temperature of the plasma resistant wall 8 can be kept constant.

A method of monitoring the temperature of the plasma resistant wall 8 shown in FIG. 3 will be described. In the case of the plasma resistant wall 8 made of quartz, a normal infrared thermometer cannot measure the temperature because of the transmission wavelength. Therefore, the sensor (fiber) of the fluorescence thermometer is brought into contact with the surface of quartz, which is the material of the plasma resistant wall 8, and the measurement is performed by utilizing the heat conduction between the quartz and the sensor. A method is conceivable in which the phosphor used is pasted or contained and the emission decay characteristics of the phosphor are measured. However, these are essentially contact-type temperature measurement methods, and it is necessary to devise to keep the contact state constant, and it is necessary to insert the sensor unit into the plasma. Therefore, it is necessary to consider that the sensor may be damaged by plasma, and various measures are required when applied to mass-produced products.

Therefore, as shown in FIG. 3, if a method of forming a film 11 of alumina or the like on the surface of the quartz 8 instead of the phosphor and measuring the temperature of the film with an ordinary infrared thermometer 12, Since the infrared rays 13 that pass through the quartz 8 are blocked, the non-contact temperature measurement can be performed without being affected by the radiation from the plasma 14. In this case, the quartz window 1 from the atmosphere side
Since it becomes possible to measure the temperature through No. 5, there is an effect that the plasma resistance measure of the temperature sensor becomes unnecessary. In addition,
In areas where heating by microwaves is not a problem or in devices that do not use microwaves, metals (preferably refractory metals such as tantalum and tungsten) are formed or contained on the surface in addition to microwave transparent materials such as alumina. The method of doing can also be applied. In this way, the temperature of the plasma resistant wall 8 can be accurately monitored, so that the control accuracy thereof can be improved and the plasma stability can be improved. However, for this method to be applied, the window 15 provided in the plasma processing chamber must transmit the infrared rays 16 in the measurement wavelength range of the infrared thermometer. Generally, quartz is used for the window material for the plasma processing chamber. Therefore, the transmission wavelength range is 4μ
m or less. An infrared radiation thermometer capable of measuring in this wavelength range is a so-called monochromatic thermometer having a single wavelength as a measurement wavelength. Further, the infrared radiation from a black body shifts to a longer wavelength region as the temperature lowers, but a monochromatic thermometer has a short measurement wavelength of around 1 μm, so that detection sensitivity becomes a problem at low temperatures. Therefore, this method is effective when the temperature of the plasma resistant wall is high.

Next, a temperature measuring method based on an idea different from that shown in FIG. 3 will be described. Another embodiment of the present invention which enables highly accurate measurement of the temperature when the plasma resistant wall is quartz is
The material of the plasma resistant material and the material of the infrared temperature measurement window should be different. FIG. 5 shows an example of the transmission wavelength range of the window material and the measurement wavelength range of the infrared thermometer. Since the transmission wavelength range of quartz and sapphire are different, use a sapphire window instead of quartz for the window material, and use an infrared thermometer (A) in the wavelength range of 4 to 5 μm as shown in FIG. For example, an infrared thermometer (A) can measure a lower temperature than when using a quartz window. Infrared thermometer (A) measuring wavelength range 4 ~
If it is wider than 5 μm, use an infrared transmission filter
It is also possible to measure as a range of 5 microns. Further, in addition to the sapphire window, a window made of silicon is also effective in the present invention. Since the silicon window transmits infrared rays in the longer wavelength range than the sapphire window, it is possible to increase the sensitivity by broadening the measurement wavelength range of the infrared thermometer to the long wavelength side.
More accurate low temperature measurement is possible. A silicon window is more suitable for a plasma etching processing apparatus or the like. By the way, in the present invention, the film 11 on the plasma resistant wall 8 shown in FIG. 3 is unnecessary.

The principle will be described below with reference to FIG.
In FIG. 7, if the plasma resistant wall 8 is made of quartz, infrared rays 13 of 4 μm or less emitted from the plasma pass through the plasma resistant wall 8 and reach the window 19 for temperature detection. Window 19
If the infrared ray is made of quartz, the infrared ray 13 passes through the window 19 and is detected by the infrared thermometer (B) 20. Of the infrared rays 17 and 18 emitted according to the temperature of the plasma resistant wall 8, the infrared ray of 4 μm or more is detected. If the window 19 is made of quartz, the infrared rays 18 in the long wavelength region are blocked by the quartz window 19, so that the detection sensitivity becomes a problem, and the temperature of the plasma resistant wall 8 cannot be measured.
Therefore, the material of the window 19 is sapphire or silicon. By using this window material, of the infrared rays 17 and 18 radiated according to the temperature of the plasma resistant wall 8, the infrared ray 18 in the long wavelength range that passes through the window 19 is 6.
It becomes 5 μm or less, and 15 μm or less in the silicon window. Therefore, the infrared ray 13 radiated from the plasma and transmitted through the plasma resistant wall 8 and the infrared ray 1 radiated from the plasma resistant wall 8
Infrared rays obtained by combining 7 and 18 reach the infrared thermometer (B) 20. However, since the measurement wavelength of the infrared thermometer (B) 20 is in the range of 4 μm or more (in FIG. 5, the measurement wavelength range of 8 to 14 μm), the plasma resistant wall 8 is radiated from the plasma.
Infrared rays 13 of 4 μm or less transmitted through the plasma and plasma resistant wall 8
Infrared rays 17 having a wavelength of 8 μm or less emitted from are not detected. Therefore, infrared thermometer (B) 2
0 is an infrared ray 18 corresponding to the temperature of the plasma resistant wall 8 made of quartz
However, since the detection sensitivity is high in this wavelength range, highly accurate temperature measurement is possible. The measurable temperature range of the infrared thermometer whose measurement wavelength is in the range of 8 to 14 μm can be measured near room temperature, and in some cases to a low temperature region of 0 ° C. or less, and the temperature of the plasma resistant wall can be adjusted from room temperature.

Although silicon is etched with fluorine or chlorine, since it is a window, it is difficult to be exposed to plasma, and since a bias voltage is not applied, the etching rate is small and there is no problem. It can be dealt with by replacing it regularly. Diamond can also be used in plasma processing where carbon is not an issue. Glassy carbon can be used instead of diamond.

Since the temperature of the inner wall surface member can be measured by the method of the present invention, the temperature of the inner wall surface member is set in advance by performing plasma discharge at the time of starting the plasma processing as a preliminary treatment of the plasma processing. Value, eg 25
Stabilization of the plasma processing characteristics can also be achieved by determining whether the temperature has reached 0 ° C. or higher and then starting the actual plasma processing. In this case, the temperature of the inner wall surface member cannot be adjusted, and it is mainly determined whether or not the temperature is stable. Therefore, if the temperature of the inner wall surface member is equal to or higher than the set value, it is limited to the case where the plasma processing characteristics are stable.

[0019]

According to the present invention, the temperature of the plasma-resistant wall surface or the dust-proof wall surface provided inside the plasma processing chamber can be controlled, so that the change of the plasma state due to the change of the wall surface temperature can be prevented. As a result, it is possible to prevent changes in plasma processing characteristics in the initial stage of plasma processing until the wall surface temperature stabilizes, and it is possible to improve the yield. Further, in the case where a step of stabilizing the wall surface temperature by performing plasma discharge in advance is performed in order to prevent a change in plasma processing characteristics, the step can be omitted, and thus the throughput is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a microwave plasma etching apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a temperature change of a plasma resistant wall.

FIG. 3 is an explanatory diagram showing a method of monitoring a temperature of a plasma resistant wall.

FIG. 4 is an explanatory diagram showing wavelength dependence of transmittance and emissivity.

FIG. 5 is an explanatory diagram showing a transmission wavelength range of a window material and a measurement wavelength range of an infrared thermometer.

FIG. 6 is an explanatory diagram showing the transmittances of quartz and a window material.

FIG. 7 is an explanatory diagram showing a temperature measuring method of the present invention.

[Explanation of symbols]

1 ... Quartz window, 2 ... Plasma processing chamber, 3 ... Wafer, 4 ... Electrode, 5 ... Waveguide, 6 ... Coil, 7 ... Vessel wall, 8 ... Plasma resistant wall, 9 ... Far infrared film, 10 ... Heater, 11 ... Film, 12 ... Infrared thermometer, 13 ... Infrared, 14 ... Plasma, 15 ... Quartz window, 16 ... Infrared, 17 ... Infrared, 18
... infrared, 19 ... window, 20 ... infrared thermometer (B).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Saburo Kanai 794 Azuma Higashitoyo, Shimomatsu City, Yamaguchi Prefecture Inside the Kasado Plant, Hitachi, Ltd. Hitachi Co., Ltd. Kasado Factory

Claims (8)

[Claims] 1. In a plasma processing apparatus for processing an object to be processed using plasma, an inner wall surface made of an insulating material such as quartz or alumina is provided inside a plasma processing chamber of the plasma processing apparatus in proximity to the wall surface of the processing chamber. Member or the inner wall member in which the insulating member is covered with a metal member is installed, and the temperature of the inner wall member is heated by far infrared rays emitted from a material that easily emits far infrared rays formed on the inner wall surface of the plasma processing chamber. A plasma processing apparatus characterized in that it is configured to control. 2. The plasma processing apparatus according to claim 1, wherein the inner wall surface member or the surface of the inner wall surface member is made of alumina, and a window made of quartz is provided in the plasma processing chamber.
A plasma processing apparatus, wherein the temperature of the inner wall surface member is measured by an infrared thermometer through the window. 3. The plasma processing apparatus according to claim 1, wherein the material provided on the inner wall surface of the plasma processing chamber is an oxide such as aluminum oxide or silicon oxide, a carbide such as carbon or silicon carbide, or aluminum nitride or the like. A plasma processing apparatus comprising a nitride such as titanium nitride, a fluoride such as aluminum fluoride, or a mixture of the above materials. 4. The plasma processing apparatus according to claim 1, wherein the temperature of the inner wall member is measured and the temperature of the plasma processing chamber is controlled by the temperature. Method. 5. The method for controlling a plasma processing apparatus according to claim 4, wherein the temperature of the plasma processing chamber is controlled by controlling the output of a resistance heater provided in the processing chamber or by providing a coolant channel in the processing chamber. A method for controlling a plasma processing apparatus, comprising controlling a temperature of a refrigerant. 6. The method for controlling a plasma processing apparatus according to claim 4, wherein a temperature detecting member made of a material that does not transmit infrared rays in a transmission wavelength range of the inner wall surface member is attached to the inner wall surface member. A method for controlling a plasma processing apparatus, wherein the temperature of a member is measured by an infrared thermometer, and the temperature of the inner wall member is controlled by the output of the infrared thermometer. 7. The method for controlling a plasma processing apparatus according to claim 4, wherein the temperature of the inner wall surface member is set in the plasma processing chamber by a window made of sapphire or silicon.
A method for controlling a plasma processing apparatus, characterized in that infrared rays having a long wavelength range or longer that do not pass through the inner wall member are measured as a measurement wavelength range of the infrared thermometer. 8. The plasma processing apparatus and the control method thereof according to claim 1, wherein the temperature of the inner wall surface member is measured with an infrared thermometer, and the temperature of the inner wall surface member reaches a preset value or more. A method for controlling a plasma processing apparatus, comprising the step of starting plasma processing after confirming that the above.