JP2000269187A - Method for monitoring treatment of substrate and manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a method for accurately monitoring the treatment of substrate to be treated in a vacuum treatment chamber, using a gas in plasma state, utilizing a Pirani gage of fast response and a method for manufacturing a semiconductor device which accurately detects the end of treatment of the substrate to be treated, using the gas in the plasma state. SOLUTION: Gas for treatment is introduced into a treatment chamber 21 subjected to pressure reduction, and the specific heat of the gas on introduction at a prescribed place in this treating chamber 21 is measured beforehand by using a Pirani gage 24 of fast response. Treatment of a substrate 20 to be treated is executed b having the state of this gas change, and the specific heat of the gas of which the state is changed from that before the treatment to that after the treatment is measured by the Pirani gage 24. The result of this measurement is compared with a measured value obtained beforehand and the state of progress of the treatment, the end point of the treatment in particular, is detected therefrom. The end point of the treatment of a wafer or the like, for which the gas in the state of plasma is used, can be detected accurately and quickly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring the processing status of a substrate in a vacuum processing chamber, and more particularly to a method for detecting the end point of semiconductor wafer processing using a high-speed vacuum gauge.

[0002]

2. Description of the Related Art Conventionally, in a process of manufacturing a semiconductor device, a process of processing a semiconductor wafer (hereinafter, referred to as a wafer) includes dry etching, CVD (Chemical Vapor Deposit).
There are many processes inside the vacuum chamber, such as ion) process and dry cleaning process.

[0003]

A description will be given of dry etching using a conventional dry etching apparatus. FIG. 7 is a conceptual sectional view of the dry etching apparatus. A vacuum vessel (chamber) 1 made of an aluminum alloy is grounded. The chamber 1 has an exhaust system 2 for exhausting the inside, a gas inlet 3 for supplying an etching gas into the chamber 1, a pressure gauge 4 for maintaining a constant pressure in the chamber 1, A quartz window 5 for viewing the inside and an electrode 6 for processing a substrate to be processed such as a wafer are mounted. The electrode 6 for processing the substrate to be processed is connected to a high-frequency power supply 7. A spectroscope 8 and a photo sensor 9 are connected to the outside of the quartz window 5 so that light emission inside the chamber 1 can be monitored. In this device, for example, a diaphragm vacuum gauge (capacitance manometer; CM) is used as a pressure gauge.

[0004] Etching using this dry etching apparatus is performed as follows. First, the inside of the chamber 1 is sufficiently evacuated using an exhaust system 2 connected to a pump (not shown). As the internal pressure, a pressure that is at least one digit lower than the pressure at the time of performing the etching process is appropriate. A silicon wafer 10 as a substrate to be processed is inserted into the chamber 1 and placed on the electrode 6 for processing the object to be processed. Next, an appropriate gas is introduced into the chamber 1 while the chamber 1 is being exhausted, and the conductance of the exhaust is adjusted using a pressure adjusting valve 11 provided in the chamber 1 so as to maintain a constant pressure. When an appropriate high-frequency power is supplied from the high-frequency power supply 7 to the electrode 6 for processing the object to be processed, plasma is generated in the chamber 1 and appropriate active species and ions are generated and formed on the silicon wafer 10. Etch the thin film. The end point of the etching can be detected, for example, by monitoring the emission of a specific element in the plasma. For example, when dry etching of polysilicon is performed using chlorine (Cl ₂ ) gas, the end point can be detected by monitoring the light emission (wavelength: 405 nm) of SiCl. At the end point of the etching, the amount of SiCl, which is a reaction product of Cl and Si, appearing in the plasma is greatly reduced, so that the time point at which the light emission amount is significantly reduced can be regarded as the end point. The setting of the wavelength is not particularly limited and is determined empirically, and the half-value width of the spectrum is not always taken out from a specific line spectrum.

That is, a conventional pressure gauge installed in a chamber for processing a semiconductor wafer measures the pressure in order to keep the pressure in the chamber constant. By using this method, etching can be stably performed. However, when a large number of silicon wafers are continuously processed, the following problem occurs. Reaction products generated by the etching include products having a low vapor pressure, and these products accumulate on the inner wall of the chamber before being evacuated. This deposited film is also deposited on a quartz window and monitored as the etching is continued (in this case, 40 wavelengths).
5 nm), the detection of the etching end point becomes difficult, and finally the end point cannot be detected at all. When this happens, open the chamber to the atmosphere and open the quartz window,
It is necessary to clean the chamber inner wall,
After the cleaning is completed, the chamber is evacuated again and the next etching can be started at least for about 3 hours.
If it is long, it may take day and night, and the operation rate of the device will be reduced. For cleaning the quartz window and the inner wall of the chamber, the following method called dry cleaning is often performed.

As in the case of etching, the inside of the chamber is sufficiently evacuated, an appropriate gas different from the etching is introduced, a constant pressure is maintained, and high-frequency power is applied to the electrodes to clean the chamber. I do. The end point detection of the cleaning is performed in the same manner as the end point detection of the etching until the emission intensity is sufficiently recovered through the quartz window until the emission intensity is recovered.
Alternatively, the end point can be detected by continuing until the specific line spectrum from the sediment decreases. However, dry cleaning has a biased effect, and in many cases, it is not possible to detect a sufficient end point only by light emission. After repeating dry cleaning several times, cleaning (wet cleaning) in which the chamber is opened is also necessary. is there. The purpose of the cleaning is not only to remove the fogging of the window but also to remove the film deposited on the inner wall of the chamber. If the deposited film becomes too thick, it will come off due to stress. The peeled deposited film becomes a particle which is particularly disliked in a semiconductor manufacturing apparatus, and thus needs to be removed before peeling.

In recent years, the pressure used in dry etching or plasma CVD equipment is about 0.1 to 10 Pa. CM is well known as a vacuum gauge that can measure this range with good reproducibility, and is widely used. As is well known, CM exposes one surface of a capacitor electrode to the side to be measured, and reads the change in the capacitance of the capacitor due to distortion of the electrode due to the pressure on the side to be measured as pressure. The pressure of the atmosphere gas can be measured. However, since plasma is used in both plasma CVD and dry etching, a lot of active atoms and molecules are generated, and these are deposited on the CM surface, so that there is a problem that the reliability of the measured value is lowered. 0.1-1
The CM suitable for measuring the pressure of 0 Pa with high accuracy has a sensitive (high sensitivity) sensor part, and the exposure pressure is:
The limit is at most about 1000 Pa. Therefore, when exposing the chamber to the atmosphere, it is necessary to isolate the sensor unit and maintain the sensor atmosphere in a high vacuum, and even if the chamber is evacuated again, the sensor unit is affected by the pressure rise due to a slight leak. There is also a problem that it takes time for the measurement pressure to stabilize. The present invention has been made in view of such circumstances, a method for accurately monitoring the processing of a substrate to be processed using a gas in a plasma state in a vacuum processing chamber using a high-speed Pirani vacuum gauge,
Further, the present invention provides a method of manufacturing a semiconductor device for accurately detecting a processing end point of a substrate to be processed such as a semiconductor wafer using a gas in a plasma state.

[0008]

SUMMARY OF THE INVENTION The present invention provides a Pirani vacuum gauge which introduces a processing gas into a decompressed processing chamber and measures the specific heat of the gas at a predetermined location in the processing chamber at a high speed response. The gas is changed in advance to perform processing on the substrate to be processed, and the specific heat of the gas in which the state is changed from before to after processing is measured by the Pirani vacuum gauge having the high-speed response. The measurement result is compared with the previously measured value to detect the progress of the process, particularly, the end point of the process. Further, by using a vacuum gauge different from the high-speed Pirani vacuum gauge, the pressure at the time of introduction of the processing gas introduced into the decompressed processing chamber is measured in advance, and the state of this gas is changed. Perform processing on the substrate to be processed, and measure the pressure of the gas whose state has been changed from before the processing to after the processing with a vacuum gauge different from the Pirani vacuum gauge, and the measurement result and the previously measured measurement value It is characterized in that the progress of the processing is detected by comparison, and the results of comparison of the measured values of the Pirani gauge and a gauge different from the Pirani gauge are further compared. With such a configuration, the processing using the gas in the plasma state in the vacuum processing chamber can be accurately and quickly monitored using the Pirani vacuum gauge, and the end point of the processing using the gas in the plasma state such as the wafer can be accurately and accurately determined. It can be detected quickly.

The high-speed response Pirani vacuum gauge used in the present invention will be described below. FIG. 6 is a conceptual sectional view of a Pirani vacuum gauge. The Pirani vacuum gauge is provided with a filament 1 at a central portion thereof at a distance from the wall 101 in the container.
00 is the main component of the gauge. The storage container is open at one end into the processing chamber to be measured. The filament 100 is connected to terminals 102 and 103 at both ends of the storage container, and these terminals also serve as a filament support. Terminal 102, 1
Numeral 03 is connected to a power supply (not shown) via a bridge circuit (not shown) which is a measurement circuit. An electric current is supplied from a power source to the filament 100 via terminals 102 and 103 to operate the Pirani vacuum gauge. The operating principle of such a Pirani vacuum gauge is as follows. When gas molecules collide with the filament 100 heated to a certain temperature, heat is taken from the filament 100 at this time. Also,
When the heated gas molecules collide with the wall 101, the wall 101
Is deprived of heat. Filament 100 via gas molecules
The amount of heat (Q) that is lost is proportional to the number of gas molecules impinging on the filament 100; ie, the pressure (P). A Pirani vacuum gauge is a measuring instrument that measures pressure using this characteristic. The amount of heat (Q) lost by the filament 100 is
It depends on the temperature difference between 0 and the wall 101.

[0010] It also depends on the specific heat of gas molecules.
The temperatures of the gas molecules 104 and 105 before and after the collision are T
Assuming that g (= wall temperature), Tf (= filament temperature), molecular weight of gas molecule is M, thermal adaptation coefficient is α, specific heat of constant pressure and constant heat of gas are Cp and Cv, respectively, the amount of heat lost by the filament 100 (Q) is expressed as follows: Q = α ｛(γ + 1) / (γ-1)｝ M-1 / ² (Tf-Tg) P (1) (where γ = Cp / Cv). By controlling with a Wheatstone bridge circuit so that Tf (= filament temperature) does not change even if the pressure (P) changes, the amount of heat (Q) lost by the filament, that is, the power supplied to the filament is proportional to the pressure (P). Pressure measurement becomes possible. However, from this equation, it can be seen that generally the measured value changes when the gas type differs. Further, it can be seen that in the case of several types of mixed gas, the composition becomes further complicated. Therefore, Pirani gauges cannot measure absolute pressure. Rather, what is measured by the Pirani vacuum gauge is the specific heat of the gas.For example, considering the vicinity of the end point of dry etching, the components or ratios of the reaction products due to the etching reaction change before and after the end point, that is, in the chamber. The specific heat as a whole of the mixed gas changes, and the Pirani vacuum gauge detects this.

The conventional Pirani vacuum gauge has a response speed as low as about 10 seconds, and cannot measure a range of 133 to 66500 Pa, which is an extremely high degree of vacuum. As described above, if the response speed is low, it is difficult to obtain an accurate end point time even when used for detecting the etching end point and the like. In addition, for example, 0.
A high-precision value cannot be obtained for measuring a relatively low pressure of about 133 Pa, and it has not usually been used for measurement in such a range. However, recent Pirani gauges (for example, high-precision Pirani gauges manufactured by ULVAC, Inc.) have improved their response speed to about 1 second or less due to improved responsiveness due to disturbances such as control signal processing and thermal insulation. And also
The measurement range is also 0.133 to 133000 Pa (0.001
１０００1000 Torr), and the performance is improved to be suitable for the monitoring method and the semiconductor device manufacturing method of the present invention. That is, the present invention uses a high-speed Pirani vacuum gauge to measure the pressure over time in the processing chamber, instead of measuring the pressure in order to keep the pressure in the processing chamber constant as in the related art. The change in pressure accompanying the process is monitored by the change in specific heat of the processing gas.

As described above, the Pirani vacuum gauge measures the specific heat of a gas atmosphere to be measured, and the pressure can be known from the measured value. CM, on the other hand,
In principle, the pressure itself is measured. In addition, comparing the atmosphere at the time of introduction into the processing chamber with the atmosphere before the processing in the plasma state, the actual pressure changes before and after the plasma generation because the decomposition of gas molecules is promoted by the plasma. Considering that this is measured by each of the above-mentioned pressure gauges, the measured values do not always match because the measured physical quantities are different.

The method for monitoring substrate processing according to the present invention comprises:
A processing gas is introduced under a predetermined condition into a reduced pressure vacuum chamber or into a processing chamber for processing a substrate to be processed connected to the vacuum vessel, and the processing gas at the time of the introduction is introduced into a predetermined place in the processing chamber. A first step of previously measuring the specific heat of using a Pirani vacuum gauge, and after introducing the processing gas,
The processing of the substrate to be processed is performed by changing the state of the processing gas, and the specific heat of the processing gas having changed the state at any time in the predetermined place from before the processing to after the processing is determined by the Pirani vacuum. A second step of measuring with a meter and a third step of comparing the measurement results measured in the first and second steps and detecting the progress of the processing. Features.
Further, the monitoring method of the substrate processing according to the present invention is characterized in that a cleaning gas is introduced under a predetermined condition into a reduced-pressure vacuum chamber or into a processing chamber for processing a substrate to be processed connected to the vacuum chamber, A first step of previously measuring the specific heat of the cleaning gas at the time of the introduction using a Pirani vacuum gauge, and performing a cleaning process on the processing chamber by changing the cleaning gas to a plasma state; A second step of measuring, using the Pirani vacuum gauge, a specific heat of the cleaning gas in the plasma state at an arbitrary time in the predetermined place from before the processing to after the processing, and measured in the first and second steps. A third step of comparing the measurement results to detect the progress of the cleaning process. It is.

Further, in the method of monitoring substrate processing according to the present invention, a processing gas comprising at least one kind of gas is supplied to a processing chamber for processing a substrate to be processed, which is connected to the vacuum chamber or in a reduced pressure vessel. The specific heat of the processing gas at the time of the introduction at a predetermined location in the processing chamber is measured in advance using a Pirani vacuum gauge and the processing gas is measured using another type of vacuum gauge. A first step of preliminarily measuring the gas pressure of, and after introducing the processing gas, performing processing on the substrate to be processed by changing the state of the processing gas, and performing the processing from before the processing to after the processing. The specific heat of the processing gas having changed the state at any time in a predetermined place is measured by the Pirani vacuum gauge, and the gas pressure of the processing gas having changed the state using the another type of vacuum gauge is used. A second step of measuring, and a third step of detecting the progress of the process by comparing the measurement results of the specific heat and the gas pressure measured in the first and second steps, respectively. That third
The feature is. The processing chamber for processing the substrate to be processed may be fixed at a constant pressure before the processing. As the Pirani vacuum gauge, a Pirani vacuum gauge having a high response speed of 1 second or less may be used.

In the method of manufacturing a semiconductor device according to the present invention, a processing gas is introduced under a predetermined condition into a reduced-pressure vacuum vessel or a processing chamber connected to the vacuum vessel for processing the surface of a semiconductor wafer on which a film is formed. The specific heat of the processing gas at the time of introduction at a predetermined location in the processing chamber is measured in advance using a Pirani vacuum gauge, and the gas pressure of the processing gas is measured in advance using another type of vacuum gauge. A first step of measuring, and after introducing the processing gas, performing processing on the semiconductor wafer by changing a state of the processing gas,
Measure the specific heat of the processing gas having changed the state at any time in the predetermined place from before the processing to after the processing by the Pirani vacuum gauge and use the another type of vacuum gauge to change the state. A second step of measuring the gas pressure of the changed processing gas, and comparing the measurement results of the specific heat and the gas pressure measured in the first and second steps, respectively, to detect the progress of the processing The first feature is that the third step is performed. Further, the method for manufacturing a semiconductor device of the present invention includes introducing an etching gas under a predetermined condition into a reduced pressure vacuum chamber or a processing chamber for processing a surface of a film-formed semiconductor wafer connected to the vacuum vessel, A first step of preliminarily measuring the specific heat of the etching gas at the time of introduction at a predetermined location in the processing chamber using a Pirani vacuum gauge, and changing the etching gas to a plasma state to keep the processing chamber constant. Performing a second etching process on the semiconductor wafer while fixing the pressure to a predetermined pressure, and measuring the specific heat of the etching gas in the plasma state at an arbitrary time in the predetermined place from before the processing to after the processing by the Pirani vacuum gauge. And a third step of comparing the measurement results measured in the first and second steps, wherein the second step That the measurement value to be measured and the first measurement values measured etching end point the point began to change toward the in step is a second feature. In the method of manufacturing a semiconductor device according to the present invention, a Pirani gauge having a high response speed of 1 second or less may be used as the Pirani gauge.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment will be described with reference to FIGS. 1 to 3 and FIG. FIG. 1 is a conceptual sectional view of a dry etching apparatus. A vacuum vessel (chamber) 21 made of an aluminum alloy is grounded. An exhaust system 22 for exhausting the inside of the chamber 21, a gas inlet 23 for supplying an etching gas into the chamber 21, a first pressure gauge 24 for monitoring the pressure in the chamber 21, and a second pressure 32 in total, 21 chambers
A quartz window 25 for viewing the inside of the device and an electrode 26 for processing a substrate to be processed such as a wafer are mounted. The electrode 26 that processes the substrate to be processed is connected to a high-frequency power supply 27. A spectroscope 28 and a photosensor 29 are connected to the outside of the quartz window 25 so that light emission inside the chamber 21 can be monitored. Etching using this dry etching apparatus is performed as follows. First, as the internal pressure for sufficiently exhausting the inside of the chamber 21 using the exhaust system 22 connected to a pump (not shown), a pressure that is at least one digit lower than the pressure at the time of performing the etching process is appropriate. A silicon wafer 20, which is a substrate to be processed, is inserted into the chamber 21 and placed on an electrode 26 for processing the substrate to be processed. Next, an appropriate gas is introduced into the chamber 21 while the chamber 21 is evacuated, and a pressure regulating valve 31 provided in the chamber 21 so as to maintain a constant pressure.
Use to adjust the conductance of the exhaust. When an appropriate high-frequency power is supplied from a high-frequency power supply 27 to an electrode 26 for processing an object to be processed, plasma is generated in the chamber 21 and appropriate active species and ions are generated and formed on the silicon wafer 20. Etch the thin film.

Conventionally, the end point of etching has been detected, for example, by monitoring light emission of a specific element in plasma. The dry etching apparatus of FIG. 1 is provided with one more pressure gauge than the conventional one (FIG. 7), and these use different types of vacuum gauges.
As the first pressure gauge, a new-type Pirani vacuum gauge whose measurement time is short and the lower limit of the measurable vacuum degree is widened is used, and a CM is attached as the second pressure gauge. As the substrate to be processed 20, for example, a silicon wafer is used,
A 300 nm-thick polysilicon film and a 300 n-thick polysilicon film are formed on this silicon wafer via a thin oxide film having a thickness of 10 nm.
m silicon oxide films (SiO ₂ ) are formed in this order. The processing target substrate 20 used here was formed of a 0.25 μm line and space (Lin) using a photoresist.
e & Space) is patterned. After the substrate to be processed 20 is placed in the chamber 2, CHF ₃ and CO
Is introduced, and the atmosphere at the time of introduction is measured with a first pressure gauge (Pirani vacuum gauge) to 5.6 Pa (actually, the total specific heat of the internal gas is measured. Since the amount of heat has a relationship proportional to the pressure, the displayed value is adjusted to the pressure converted from the equation (1) (hereinafter, similarly represented by Pa). At this time, the display value of the second pressure gauge (CM) is 5.3 Pa.

Next, a power of 3.4 W / cm ² is applied to the electrode 26 from the high frequency power supply 27 to generate plasma to etch the silicon oxide film (SiO ₂ ). When performing this etching, the pressure adjustment valve 31 is fixed. The indication value of the Pirani vacuum gauge at the time of introducing the mixed gas was 5.6 Pa since the plasma was not generated, but it becomes 6.1 Pa when the plasma is generated. After the polysilicon film is exposed and the etching end point of the silicon oxide film (SiO ₂ ) is reached, the indication value of the Pirani vacuum gauge is 5.6 Pa.
It became. From the above, the indication value of the Pirani vacuum gauge was 6.
The start point of the change from 1 Pa to 5.6 Pa is the end point of the etching. Therefore, the end point of the etching can be detected by monitoring the change in the indicated pressure value. With this method, the etching end point can be easily and stably monitored.

FIG. 8 is a characteristic diagram showing the relationship between the pressure in the processing chamber and the time course of the processing. The vertical axis represents the pressure (Pa) in the processing chamber, and the horizontal axis represents the processing time (second). At the time A when the processing starts, the pressure of the processing gas in the processing chamber is p (Pa). In the dry etching apparatus shown in FIG. 1, p1 = 5.6. Electric power is applied to this dry etching apparatus to convert the gas in the processing chamber into plasma. The pressure in the processing chamber becomes p
2 (Pa). In FIG. 1, p2 = 6.1. The degree of the effect of the plasma is about 10% or more. Then, a pressure change occurs at time C, and this time point is measured to detect the etching end point. At time D, the etching ends. Time Δt from point C where pressure changes to point D where pressure stabilizes
Is at most 1 second, and therefore, a Pirani vacuum gauge having a high response speed of 1 second or less can sufficiently detect the etching end point. The final pressure may not always coincide with the initial pressure because the gas species may eventually change, and may be higher or lower. FIG.
, The final pressure is equal to the initial pressure. Further, since the response speed of the conventional Pirani vacuum gauge is about 10 seconds, it cannot be used for detecting the etching end point.

Conventionally, if the quartz window of the chamber becomes cloudy, it becomes difficult to detect the end point by light emission. Therefore, cleaning is performed at a certain frequency (for example, dry cleaning every 100 etchings, every four dry cleanings, that is, every 500 etchings). Wet cleaning by opening to the atmosphere)
However, the use of this method eliminated the need for dry cleaning for every 100 sheets. Further, when the pressure indication values before and after plasma generation were examined, the following was found. FIG. 2 shows changes in indicated values of the first pressure gauge (Pirani vacuum gauge) and the second pressure gauge (CM) before and after plasma generation. CM was theoretically closer to absolute pressure than the Pirani gauge and was considered to be less affected by discharge.In fact, however, there are gases whose composition changes greatly before and after the start of discharge, and there are also cases where CM has the effect of discharge. I found it.
If there is an effect of this discharge, it is not clear at present whether this is a problem of the vacuum gauge itself or any other problem, but if there is a possibility other than the vacuum gauge, the following can be considered. When the atmosphere in the chamber is O ₂ gas (that is, when dry cleaning is performed), the indicated value of CM increases after discharge (5.1 Pa → 9.
9 Pa (FIG. 2)), when this evaluation was performed, the deposited film (CFx) was adhered to the inner wall of the chamber, and the pressure was substantially increased by etching the film by O ₂ discharge.

That is, CF _x (solid) + O ₂ → CO + xF
+ O) is considered to increase the pressure by increasing the number of molecules according to the reaction formula (O ₂ → 2O).
Reaction is small). In the case of CHF ₃ , since CF _x is deposited in the chamber at the same time as the start of discharge, it is considered that the number of molecules decreases and the pressure decreases. Even if the pressure in the same chamber is measured, the measured value differs between the CM and the Pirani vacuum gauge because the measuring method is different for each pressure gauge. The process of this embodiment is shown in FIG.
This will be described with reference to FIG. The figure is a flowchart for detecting the end point of the process of etching a wafer using FIG.
First, (1) a wafer is mounted in a chamber. (2) An etching gas is introduced into the chamber. (3) The pressure inside the chamber is fixed to fix the internal pressure. (4) The pressure in the chamber is measured with a Pirani vacuum gauge. (5)
Electric power is supplied to the electrodes in the chamber to convert the etching gas into plasma. (6) The pressure in the chamber after the formation of plasma is measured by a Pirani vacuum gauge. (7) The etching state in the chamber is monitored while measuring the Pirani vacuum gauge as needed. (8) If it starts to change in a direction approaching the measurement result of step (4), it is determined as the etching end point.

Next, a second embodiment will be described with reference to the above description of the Pirani vacuum gauge. This embodiment will be described using the dry etching apparatus shown in FIG. This apparatus differs from the conventional apparatus in FIG. 7 in the type of pressure gauge and uses a Pirani vacuum gauge. FIG. 4 is a conceptual sectional view of the dry etching apparatus. A vacuum vessel (chamber) 41 made of an aluminum alloy is grounded.
The chamber 41 has an exhaust system 4 for exhausting the inside.
2. A gas inlet 43 for supplying an etching gas into the chamber 41, a pressure gauge 44 composed of a Pirani vacuum gauge for monitoring the pressure in the chamber 41, a quartz window 45 for viewing the inside of the chamber 41, and processing of wafers and the like. An electrode 46 for processing the substrate 40 is mounted. Substrate to be processed 4
The electrode 46 for processing 0 is connected to a high-frequency power supply 47. A spectroscope 48 and a photosensor 49 are connected to the outside of the quartz window 45 so that light emission inside the chamber 41 can be monitored.

A silicon wafer selected from the 500 silicon wafers subjected to the etching process is mounted on the electrode 46 in the chamber 41 with the substrate 40 to be processed. First, O ₂ gas was introduced into the chamber 41, and the internal pressure at the time of introduction was measured using the Pirani vacuum gauge 44, and it was 3.5 Pa. Next, 4.9 W / c is applied to the electrode 46 from the high frequency power supply 47.
An RF power of m ² is supplied to bring the gas into a plasma state.
The pressure indication value at this time is 7.7 Pa. Thereafter, the internal pressure gradually decreased as the processing in the apparatus progressed, and it was found that the pressure reading of the Pirani vacuum gauge 44 returned to 3.5 Pa after 3 minutes. When the inside of the chamber 41 was opened to the atmosphere in this state, the deposits in the chamber 41 had been cleanly removed. FIG. 5 is a characteristic diagram showing a processing time (cleaning time) dependency of a pressure indication value (Pa) indicating the pressure inside the chamber and the emission intensity of CO observed by a conventional method. A is a curve showing the relationship between the indicated pressure value and the processing time, and B is a curve showing the relationship between the emission intensity of CO and the processing time. As shown by the curve B in the figure, the emission intensity of CO (around 313 nm) decreased in about 2 minutes in the past, and this area was considered as the end point of the dry cleaning (that is, the cleaning was slightly insufficient). . But,
In practice, the end point is about 3 minutes after returning to the original pressure reading as described above.

Based on this result, by performing dry cleaning for 3 minutes after processing each of 500 wafers, wet cleaning by opening to the atmosphere, which was conventionally required for stabilizing particles, is no longer necessary. The other reason why the output of the CM changes before and after the start of discharge is considered to be that deposits adhere to the surface of the capacitor, which is the heart of the CM, as described in connection with the related art. It is known that a source gas (a source gas such as CF ₃ or CO) dissociated by discharge, a reaction product by etching, and the like adhere to the deposit. When the deposits adhere to the capacitor surface, the inclusions substantially become capacitors, and thus do not show accurate values. This should appear as a change with time rather than before and after the start of discharge. Actually, for example, when a long-term used CM and a new CM are attached to the same chamber and the output is compared, they show different values. To eliminate such an effect, the CM used as described above is used.
It is conceivable to use the output of the capacitor while calibrating it with the output of the CM for calibration, or to constantly heat the capacitor surface to suppress the adhesion of deposits. This will increase the cost. Further, in order to suppress the adhesion of the deposits, it is necessary to heat the surface temperature to about 120 to 130 ° C.
８０80 ° C.), at most not exceeding 100 ° C.

On the other hand, the Pirani vacuum gauge used in the present invention heats the filament temperature, which is the heart, to about 140 ° C., and uses a highly corrosion-resistant Pt as a filament material.
Is used, the adhesion of the deposits and the corrosion by the corrosive gas can be suppressed, and the improvement is advanced, the response speed is about 1 second, and the measurement range is 0.133 to 133000 Pa.
(0.001 to 1000 Torr), so that a more stable output can be maintained. The sensor is P
Since the filament is made of t and has no sensitive portion such as CM, there is no need to isolate the chamber when returning the chamber to atmospheric pressure. In addition, the reproducibility and reliability of the measurement are high.
Therefore, it is easier and cheaper to handle than a CM. Above, the method of monitoring the change of the Pirani vacuum gauge as the end point detection such as dry etching and cleaning was described.However, in semiconductor processes, especially dry etching, absolute pressure is not particularly important. As for the reproducibility and the change of the output over time when the same setting is made, the range from a short range (several seconds to several minutes) such as the above-described detection of the etching end point to the interval of opening the chamber to the atmosphere (several days to several weeks) There is also a long range of things. As a way to detect these changes,
The method of monitoring vacuum gauge changes of the present invention is considered to be simple, accurate and effective.

In addition, only one Pirani vacuum gauge is used for monitoring.
The changes of several different gauges simultaneously
By doing so, it is possible to further increase the sensitivity. example
O _TwoFor gas, CM and Pirani vacuum before and after starting discharge
In both cases, the indicated pressure increases about twice, but C_FourF₈Moth
In the case of a commercial, the indicated value increases slightly in CM,
In Pirani, the indicated value decreases to about 67%. Therefore,
Using a mixed gas, the reaction product is also a complex process gas.
To monitor information, compare these data.
More accurate monitoring becomes possible. What can be monitored
Is often based on empirical methods,
Can be used to understand phenomena by comparing with results
Can be easily predicted. For example, set by dry etching
Possible parameters include the degree of vacuum and the gas to be introduced.
Flow rate, RF power, substrate temperature, chamber temperature, etc.
There is. However, these parameters to be set
Even so, the etching characteristics and the like may not be stable.
The cause is, for example, the high voltage actually applied to the wafer.
Frequency power and induced bias may change,
It is considered that the plasma may be biased due to abnormal internal components.
available. These changes do not require replacement of parts in the chamber.
Appears before and after maintenance and changes over time
Or

On the other hand, a pressure gauge indicating a stable characteristic is obtained empirically, and the change is monitored to monitor the change of the plasma which affects the etching characteristic. It is thought that it is also possible to detect as a change. For example, when using anodized aluminum material that is often used as a chamber material,
When the alumite film is peeled off and the underlying aluminum is exposed, it is etched and the pressure indication value may change. In the case of performing etching or dry cleaning, in the embodiment, the pressure adjustment valve is fixed and the end point at which the pressure output starts to change is described. However, these processes may be performed while keeping the pressure constant. The method can be achieved by sending an output signal of a vacuum gauge to a pressure regulating valve and moving the pressure regulating valve so that the pressure signal becomes constant. Therefore, when etching or dry cleaning is performed by this method, the pressure adjusting valve is moved near the end point of etching or cleaning. Therefore, the point at which the signal for operating the pressure regulating valve is output is the etching end point. By monitoring this signal, the end point detection using the Pirani vacuum gauge can be performed even in the process of keeping the pressure constant.

According to the present invention, plasma control and monitoring in a simple and inexpensive substrate processing can be performed. Although the present invention has been described with reference to the embodiments based on dry etching, the present invention is not limited to this, and can be applied to processes such as plasma CVD, thermal CVD, and sputtering film forming processes. .

[0029]

According to the present invention, the response speed due to disturbances such as signal processing and thermal insulation of the control system is improved, the response speed is improved to about 1 second, and the measurement range is 0.133 to 1330.
It is configured using a Pirani vacuum gauge expanded to 00 Pa, and monitors processing of a substrate using a gas in a plasma state in a vacuum processing chamber simply, quickly, and accurately using the Pirani vacuum gauge. In addition, it is possible to simply, quickly and accurately detect the processing end point of a substrate such as a wafer using a gas in a plasma state.

[Brief description of the drawings]

FIG. 1 is a conceptual sectional view of a dry etching apparatus of the present invention.

FIG. 2 shows a Pirani vacuum gauge before and after generating plasma and C
FIG. 4 is a characteristic diagram showing a change in a pressure instruction value of M.

FIG. 3 is a process flow chart for detecting an etching end point according to the first embodiment.

FIG. 4 is a conceptual sectional view of a dry etching apparatus according to the present invention.

FIG. 5 is a characteristic diagram showing the processing time dependency of the pressure indication value (Pa) inside the chamber and the emission intensity of CO observed by a conventional method.

FIG. 6 is a sectional view of an essential part of a Pirani vacuum gauge used in the present invention.

FIG. 7 is a conceptual sectional view of a conventional dry etching apparatus.

FIG. 8 is a characteristic diagram showing a relationship between a pressure in a processing chamber and a lapse of time of processing.

[Explanation of symbols]

1, 21, 41 ... chamber, 2, 22, 42
..Exhaust systems, 3, 23, and 43 gas inlets
4, 44 ... pressure gauge, 5, 25, 45 ... quartz window,
6, 26, 46 ... electrodes, 7, 27, 47 ...
High frequency power supply, 8, 28, 48 ... Spectroscope, 9, 2
9, 48 ... sensor, 10, 20, 40 ... wafer, 11, 31, 51 ... pressure regulating valve, 24
..First pressure gauge, 32... Second pressure gauge, 10
0 ... filament, 102, 103 ... terminal.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Katsuya Okumura 8, Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 2F055 AA40 BB08 CC43 DD20 EE40 FF31 GG01 4G075 AA25 AA61 BC02 BC04 BC06 BD14 CA47 CA65 DA02 DA13 EB01 EB41 5F004 AA15 BA04 CA02 CA08 CB01 CB02 CB15 DA16 5F103 AA08 BB25 BB51 BB59 NN04 PP01

Claims (8)

[Claims] 1. A process gas is introduced under a predetermined condition into a reduced-pressure vacuum chamber or into a processing chamber for processing a substrate to be processed connected to the vacuum vessel, and the gas is introduced into a predetermined location in the processing chamber. A first step of previously measuring the specific heat of the processing gas using a Pirani vacuum gauge, and performing a process on the substrate by changing the state of the processing gas after introducing the processing gas. A second step of measuring, using the Pirani vacuum gauge, a specific heat of the processing gas having changed the state at any time in the predetermined place from before the processing to after the processing, and the first and second steps. A third step of comparing the measurement results measured in the steps to detect the progress of the processing, and a third step of monitoring the substrate processing. 2. A cleaning gas is introduced under a predetermined condition into a reduced pressure vacuum chamber or into a processing chamber for processing a substrate to be processed connected to the vacuum chamber, and the cleaning gas is introduced into a predetermined place in the processing chamber at the time of the introduction. A first step of previously measuring the specific heat of the cleaning gas using a Pirani vacuum gauge, and performing a cleaning process on the processing chamber by changing the cleaning gas to a plasma state, from before the process to after the process. A second step of measuring, using the Pirani vacuum gauge, specific heat of the cleaning gas in the plasma state at an arbitrary time at the predetermined location,
And a third step of comparing the measurement results measured in the second step to detect the progress of the cleaning processing, and a third step of monitoring the substrate processing. 3. A process gas comprising at least one kind of gas is introduced under a predetermined condition into a reduced-pressure vacuum chamber or into a processing chamber connected to the vacuum chamber for processing a substrate to be processed. The specific heat of the processing gas at the time of introduction at a predetermined place is measured in advance using a Pirani vacuum gauge, and the gas pressure of the processing gas is measured in advance using another type of vacuum gauge. Step 1, and after introducing the processing gas, performing processing on the substrate to be processed by changing the state of the processing gas, and performing the processing at any time in the predetermined place from before the processing to after the processing. A second step of measuring the specific heat of the processing gas having changed by the Pirani vacuum gauge and measuring the gas pressure of the processing gas having changed the state using the another type of vacuum gauge, and First and second A third step of comparing the specific heat and gas pressure measurement results measured in the step of detecting the progress of the processing, respectively. 4. The substrate processing monitoring method according to claim 1, wherein the processing chamber for processing the substrate to be processed is fixed at a constant pressure before the processing. . 5. The Pirani vacuum gauge having a response speed of 1
5. The monitoring method for substrate processing according to claim 1, wherein a Pirani vacuum gauge having a high-speed response of sub-second or less is used. 6. A processing gas is introduced under a predetermined condition into a reduced pressure vacuum chamber or into a processing chamber connected to the vacuum chamber for processing a surface of a semiconductor wafer on which a film is formed, and a predetermined location in the processing chamber. A first step in which the specific heat of the processing gas at the time of introduction is previously measured using a Pirani vacuum gauge and the gas pressure of the processing gas is measured in advance using another type of vacuum gauge. Performing the processing on the semiconductor wafer by changing the state of the processing gas after introducing the processing gas, and changing the state of the predetermined place at any time from before the processing to after the processing. A second step of measuring the specific heat of the processing gas with the Pirani vacuum gauge and measuring the gas pressure of the processing gas with the state changed using the another type of vacuum gauge; and The second step A third step of comparing the specific heat and gas pressure measurement results measured in each step to detect the progress of the processing. 7. An etching gas is introduced under a predetermined condition into a decompressed vacuum chamber or into a processing chamber for processing the surface of a film-formed semiconductor wafer connected to the vacuum chamber under a predetermined condition. A first step of previously measuring the specific heat of the etching gas at the time of introduction using a Pirani vacuum gauge, and changing the etching gas to a plasma state, fixing the processing chamber at a constant pressure, and A second step of performing an etching process on a semiconductor wafer and measuring a specific heat of the etching gas in the plasma state at an arbitrary time in the predetermined place from before the process to after the process using the Pirani vacuum gauge; And a third step of comparing the measurement results measured in the second step, wherein the measurement value measured in the second step is A method of manufacturing a semiconductor device, characterized in that a point at which the value starts to change toward a measured value measured in one step is an etching end point. 8. The Pirani vacuum gauge having a response speed of 1
8. The method for manufacturing a semiconductor device according to claim 6, wherein a Pirani vacuum gauge having a high-speed response of sub-second or less is used.