JPH05206076A - Plasma processing device - Google Patents

Abstract

PURPOSE:To surely catch the etching end point by providing optical system which monitors emission from plasma process with a moving mechanism which permits the optical system to move from the plasma processing system. CONSTITUTION:Optical system 3 which is a monitoring means 4 that monitors emission from the processing area A of a plasma processing means 2 is provided with a moving mechanism 54 which moves a lens container 42 vertically, horizontally and back and forth against the processing area A in a vacuum chamber 6. The moving mechanism 5 is composed of an X table 68 which is movable in the focal point direction of the lens 40, a Y table 40 which is movable in the Y direction and a vertically movable Z table 60. The lens container 42 is fixed on the X table so as to move each table, the focal point of the lens is positioned at the peak of the emission intensive point and even a slight plasma intensity change is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus.

[0002]

2. Description of the Related Art In the semiconductor manufacturing process, dry etching performed by using, for example, a plasma processing apparatus is an essential technique for forming a fine pattern. This etching is a method in which plasma is generated by using a reaction gas in a vacuum and an object is removed by using ions, neutral radicals, atoms and molecules in the plasma. By the way, if the etching is continued even after the object to be etched is completely removed, the underlying material is unnecessarily scraped or the etching shape is changed. It is very important to accurately detect the end point of.

Therefore, a typical method conventionally used to detect the end point of etching is to monitor the emission intensity of the reaction product of the etching by using an optical system equipped with a lens or the like to detect the change in the emission intensity. Had decided the end point. Specifically, on the outside of the reaction vessel equipped with a plasma electrode, for example, an observation window made of quartz glass having a diameter of several cm is provided.
An optical system including a lens is fixedly installed outside this. Then, for example, the light emission generated at the time of etching processing by plasma is condensed by the above optical system and is guided to a photoelectric conversion element or the like by an optical fiber, and the output is processed by a determination unit or the like to detect the end point of etching or the like. I was going. For example, when a silicon dioxide film is etched with a CF-based etching gas, the emission of carbon monoxide, which is a reaction product, is condensed through an optical system including the lens and converted into an electric signal by a photoelectric conversion element. Then, the emission intensity was monitored by processing this signal, and the end point of etching was judged based on this intensity change. That is,
The reaction product exists in the reaction vessel during etching, but it will not be generated when the etching target is exhausted.
This emission intensity decreases, and therefore, the end point of etching can be detected by catching this decrease.

[0004]

By the way, in order to obtain the stability of plasma during etching,
Alternatively, in order to increase the selectivity with respect to the underlying film and the resist, a large amount of additive gas other than the etching gas is added as compared with the etching gas. For example, argon is sometimes used to stabilize the plasma, but the emission spectrum of this argon gas itself spreads in a band shape, and the spectrum of the reaction product carbon monoxide overlaps and is buried in this spectrum. It may end up. The reason why such overlap occurs is that argon and carbon monoxide have strong emission wavelength ranges of 300 to 800, respectively.
This is because both ranges are very close to each other. Moreover, the amount of carbon monoxide gas generated is very small because the etching target area where the chemical reaction due to etching occurs is very small, whereas the amount of argon gas introduced is several times the amount of etching gas. -10
As a result, the emission intensity of argon gas becomes much larger than the emission intensity of carbon monoxide, and as a result, as described above, the emission spectrum of carbon monoxide is equal to that of the plasma itself. Since it is buried and the emission intensity of carbon monoxide cannot be accurately detected, it is difficult to specify the end point of etching, for example.

Therefore, the inventor of the present application has
Instead of the emission spectrum of the reaction product, the emission spectrum of an etching gas whose emission spectrum region is completely different from that of argon gas is monitored, and when the amount of etching gas increases and the amount of this emission increases, this emission amount increases. For example, the method of setting the etching end point is disclosed. However, due to the trend toward miniaturization or the increase in the need for a special etching process such as etching only contact holes, only trenches, or only wiring patterns, the opening showing the area ratio of the etching target area to the entire wafer area is opened. In recent years, when the rate tends to be reduced to 1% or less, the fluctuation of the etching gas amount before and after the etching end point, that is, the intensity change of the emission spectrum of the etching gas becomes very small, and the emission amount is very small. Since it is very small, even the method disclosed above is no longer sufficient.

Further, the intensity of the emission spectrum from each gas constantly fluctuates due to slight fluctuations in the power supply voltage, the influence of the mass flow controller, fluctuations in the processing pressure, and rises in the substrate temperature caused by plasma. Therefore, even if the intensity change of the emission spectrum of the etching gas is monitored as described above, it is relatively difficult to specify the etching end point, for example. Furthermore, the plasma generation position varies depending on the wafer size of the object to be processed, and in order to observe the optimum plasma peak point in each case in consideration of the fluctuation of the plasma generation position due to the change in the process conditions, There was a problem that it could not be handled if the optical system for observing the plasma intensity was fixed. In such a situation, in general, the plasma standing in the reaction vessel is different due to the difference in various conditions such as the size of the wafer to be processed, the processing step, and the gas conditions to be used. The strongest portion moves vertically between the plasma electrodes in the front-rear, left-right, and up-down directions, mainly depending on various process conditions.

However, in the conventional apparatus, since the optical system including the lens for catching the emission intensity of the plasma is fixedly installed, it is not always possible to observe the peak point of the emission intensity, and the peak point of the emission intensity is small. In today's situation where it is required to detect even such a change in emission intensity itself, there is an improvement point that it is more difficult to detect the end point of etching and the like. The present invention has been made to pay attention to the above problems and to solve them effectively. An object of the present invention is to provide a plasma processing apparatus in which a moving mechanism is provided in an optical system that catches plasma emission.

[0008]

In order to solve the above problems, the present invention provides a plasma processing apparatus having monitor means for monitoring light emission from the plasma processing means via an optical system, wherein the optical system comprises: It is configured to have a moving mechanism that is movable with respect to the plasma processing system.

[0009]

Since the present invention is configured as described above, when the emission peak point in the plasma processing means moves,
Immediately driving the moving mechanism moves the optical system such as the lens in the vertical and horizontal directions or in the front-back direction, so that the focal point of the lens always coincides with the strongest emission intensity. As a result, even a slight change in the emission intensity of plasma can be sufficiently detected, and for example, the etching end point can be surely known.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the dry etching method according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a plasma processing apparatus according to the present invention. In this embodiment, an etching apparatus will be described as an example of the plasma processing apparatus. As shown in the figure, this etching apparatus is mainly composed of a plasma processing means 2 for actually etching an object to be processed and a monitor means 4 for monitoring the emission intensity or light emission from the processing means 2. The monitor means 4 is mainly composed of an optical system 3 for catching light emission during etching and a processing system 5 for processing an electric signal from the optical system 3. The plasma processing means 2 has a vacuum chamber 6 which is a reaction container and is made of, for example, aluminum.
Inside, plate-shaped electrodes 8 and 10 are arranged vertically opposite to each other. For example, the upper electrode 10 is grounded and the lower electrode 8 is connected to a high frequency power source 14 via a capacitor 12.

The electrodes 8 and 10 constitute parallel plate electrodes, and the electrodes 8 and 10 may also serve as the vacuum chamber 6. In the illustrated example, the space between the electrodes 8 and 10 is widely described for the sake of description, but the space between the electrodes is actually about 5 mm. The lower electrode 8 is provided with a semiconductor substrate 16 which is an object to be processed on the upper surface thereof, and a clamper or the like is provided so as to securely fix the substrate 16. Further, a gas introduction pipe 20 is connected to the side wall of the vacuum chamber 6, and the CF is provided in the chamber.
It is configured to introduce a system stabilizing gas or a plasma stabilizing gas such as argon. A vacuum exhaust pipe 22 is connected to the other side wall so that the inside of the vacuum chamber 6 can be evacuated to an arbitrary pressure by a vacuum pump or the like (not shown).

Further, a load lock chamber 26 is connected to the side wall of the vacuum chamber 6 via a gate ben 24, and the semiconductor substrate 16 is provided in the vacuum chamber 6 by an arm (not shown) without opening the atmosphere to the atmosphere. Is configured so that it can be carried in and out. Further, the vacuum chamber 6 has a sidewall with a diameter of about 20 mm made of, for example, quartz gas that allows light in a short wavelength range to pass therethrough in order to transmit the light emitted from the plasma generated between the electrodes 8 and 10 to the outside. An observation window 28 is provided so as to face the electrodes.

As shown in FIG. 3, the observation window 28 is provided with an adhering substance removing means 30 for eliminating reaction products and the like adhering to the inside of the observation window 28 at the time of etching processing to eliminate fogging. It is provided. Specifically, the adhering substance removing means 30 is a heating means formed in the peripheral portion of the observation window 28 along the circumferential direction thereof, for example, the ceramic heater 3.
Have two. A heater power supply 34 for applying heating power to the ceramic heater 32 is connected to the ceramic heater 32. Further, a heat detector, for example, a thermocouple 36 is installed in the vicinity of the ceramic heater 32 so that the heating temperature of the heater 32 and the observation window 28 can be measured. A control unit 38 including, for example, a microcomputer is connected to the thermocouple 36, and the observation window 28 is required by controlling the heater power supply 34 according to the output value from the thermocouple 36. Accordingly, the heating is maintained at a predetermined temperature. Therefore, by driving the deposit removing means 30 during or after the etching process, the observation window 28
Is heated to prevent the deposits from adhering to it.

On the other hand, the optical system 3 of the monitor means 4 for monitoring the light emission from the processing area A of the plasma processing means 2 has a condenser lens 40 which is brought close to the observation window 28 and faces the observation window 28. It is configured to collect the light transmitted through the observation window 28. The condenser lens 40 is housed in one end of a cylindrical lens container 42, and a light guide having a light absorption characteristic such as an optical fiber is provided in an optical path downstream from the condenser lens 40. Do not use any medium. That is, in the optical path L from the condenser lens 40 on the other end side in the lens container 42, in order to divide the condensed light into about half and branch it into two, the optical path L is divided. A half mirror 44 tilted at 45 ° is provided and is configured to form an optical path L1 of transmitted light and an optical path L2 of reflected light which is perpendicular to the optical path L1.

Then, on the optical path L1 of the transmitted light and at the other end of the lens container 42, for example, a specific wavelength, for example, a wavelength, is passed in order to allow light emission from CF ₂ gas, which is an active species during plasma etching, to pass therethrough. A first interference filter 46 that selectively transmits light in the region of about 259.5 nm and light for converting the light that has passed through the filter 46 into an electrical signal,
A first photoelectric conversion element 48 such as a photodiode is provided, and is configured to convert the transmitted light into an electric signal. Further, on the optical path L2 of the reflected light and on the side wall on the other end side of the lens container 42, a specific wavelength, for example, for passing light emitted from CO gas, which is a reaction product at the time of plasma etching, is passed. Wavelength 482.7n
A second interference filter 50 that selectively transmits light in a region of about m and a second photoelectric conversion element 52, such as a photodiode, for converting the light that has passed through the filter 50 into an electrical signal are continuously provided. And is configured to convert the reflected light into an electrical signal. It should be noted that instead of the above-mentioned relatively inexpensive interference filters 46 and 50, a spectroscope having good spectral accuracy may be provided.

As described above, since the optical system 3 does not use any light guide medium that tends to absorb light in a relatively short wavelength range, light with weak emission intensity or slight intensity change is surely performed. It becomes possible to detect. Then, as shown in FIG. 2, the lens container 42 accommodating the lens 40 is arranged in a vertical (Z) direction, a horizontal (Y) direction, and a front-back direction with respect to the processing region A in the vacuum chamber 6, that is, the observation window 28. In order to be movable in the (X) direction, it is attached to the moving mechanism 54 which is a feature of the present invention. In particular,
The moving mechanism 54 is mounted on a base 56 via a rail 66 in the X direction by a linear motor or the like in the X direction, that is, the lens 4
X table 68 installed so as to be movable in the focus direction of 0
And a Y mounted on the X table 68 via a Y-direction rail 62 so as to be movable in the Y-direction by a linear motor or the like.
The table 64 and a Z table 60 mounted on the Y table 64 via a lifting means 58 such as a ball screw so as to be movable up and down are mainly configured. On the X table 68, the lens container 42 is mounted. The lens 40 is mounted at a desired position in the processing area A, that is, at the peak point of the emission intensity by moving each table while mounting and fixing.
Is configured so that the focal point F of can be positioned.

The movement of each table is performed by a control signal from the movement mechanism controller 53. By moving the lens container 42, the first filter 46, and the second filter 50 on the X, Y, and Z tables, the optical paths L, L1, and L are moved.
2 moves up and down and left and right, but in reality, these moving distances are small, and the optical path is not deviated from the half mirror surface or the surfaces of the interference filters 46 and 50, and the optical path is deviated. Set a half mirror and interference filter to a size that does not exist. Further, as in this embodiment, the lens 40, the half mirror 44, the first and second interference filters 46 and 50, and the first and second photoelectric exchanges 48 and 52.
All of the above, that is, the whole of the optical system 3 is mounted on a table so as to move integrally. Therefore, as described above, the light passing through the lens 40 surely reaches the half mirror 44.

On the other hand, the first photoelectric converter 48 of the above optical system 3
The output line 70 output from is connected to the first amplifier 72 for amplifying the signal of the processing system 5 and the first amplifier 72
The output of is connected to a first low-pass filter 74 of, for example, about 10 Hz in order to remove frequency components outside the observation band. Then, this first low-pass filter 7
The output of 4 is the first A for digitizing analog signals
The output of the A / D converter 76 and the output of the converter 76 is, for example, a determination unit 78 including a microcomputer.
Has been entered into. Further, the output line 80 output from the second photoelectric converter 52 is the second line for amplifying the signal of the processing system 5.
In addition to being connected to the amplifier 82, the output of the second amplifier 82 is connected to the second low-pass filter 84 of, for example, about 10 Hz in order to remove frequency components other than the observation band, as described above. The output of the second low-pass filter 84 is the second output for digitizing the analog signal.
The output of the converter 86 is input to the A / D converter 86, and the output of the converter 86 is input to the determination unit 78. The signal indicating the emission intensity of the reaction product input from the converter 86 and the first A / D signal are input. The ratio with the signal indicating the emission intensity of the active species input from the converter 76 is obtained, and the end point of etching is detected when the amount of change in this ratio exceeds a predetermined amount.

The band of the first and second low-pass filters 74 and 84 is not limited to 10 Hz, and the band frequency is related to the sampling frequency of the A / D converters 76 and 86 in the subsequent stage. Is set,
To faithfully represent the original signal, a sampling frequency that is at least four times the band frequency of the low-pass filter,
For example, in this embodiment, A / D conversion is performed at a sampling frequency of about 40 Hz or higher. As a result, it is possible to accurately capture the change in emission intensity, and it is possible to extract only the DC component by further averaging. On the other hand, the output of the determination unit 78 is connected to an overetching timer circuit 88 for setting the time for performing overetching, and overetching is performed for a predetermined time after the end of etching to appropriately set, for example, the taper angle during etching. It is configured to be adjustable. As described above, the reason for performing over-etching is that, for example, the peripheral portion and the central portion of a circular semiconductor substrate have different gas densities, so that the etching rate is different and the degree of etching becomes uneven, or As a result, sagging may occur at the tangent line between the non-etched portion and the etched portion, and this is done to correct them.

The output of the over-etching timer circuit 88 is connected to a high-frequency control circuit 90 for controlling ON / OFF of the high-frequency power source 14, and an over-etching end signal from the over-etching timer circuit 88. Upon receiving the signal, the driving of the high frequency power source 14 can be completely stopped. Next, the operation of this embodiment configured as described above will be described. First, the semiconductor substrate 16 that has already been loaded into the load lock chamber 26 in the plasma processing means 2 is placed on the lower electrode 8 by the arm (not shown) via the gate bend 24. A mask having a predetermined pattern is formed on the silicon dioxide film of the semiconductor substrate through an exposure process.

After the semiconductor substrate 16 is introduced into the vacuum chamber 6 as described above, the inside of the vacuum chamber 6 is evacuated to a predetermined pressure through the vacuum exhaust pipe 22, and the gas introduction pipe 20
A CF-based gas such as CHF ₃ gas or CF ₄ gas is introduced as an etching gas at a flow rate of 60 SCCM, and an argon gas is introduced as a plasma stabilizing gas at a flow rate of 1000 SCCM, and a predetermined vacuum degree, for example, 1 Set to about 2 Torr. The frequency 13.56MH _z or 380 between the electrodes 8 and 10 in the vacuum chamber 6 by driving the high-frequency power source 14
A high frequency power of KHz _{and a} power value of 750 W is applied to generate plasma, and the silicon dioxide film of the substrate 16 is etched. At this time, the temperature of the substrate 4 is set to, for example, −50 to 40 ° C.

The CHF ₃ gas or CF ₄ gas introduced into the chamber 6 is dissociated in plasma to generate various kinds of active species, which participate in the etching reaction. For example,
Taking CF ₂ radicals Examples as active species, the CF ₂
Radicals react with silicon dioxide as shown in the following formula. _{S i O 2 + 2CF 2 →} S i F 4 + 2CO , where plasma stabilizing argon gas is a gas, a CF ₂ gas and reaction products which is an etching gas C
The O gas or the like emits light with a unique spectrum in the plasma, but the light emitted through the observation window 28 is collected by the condenser lens 40 of the optical system 3 and passes through a light guide medium such as an optical fiber. Without passing through the atmosphere, or when the entire optical system 3 is a vacuum system, it passes through the vacuum along the optical path L and hits the harp mirror 44,
Here, the transmitted light and the reflected light are split into two.

The transmitted light passes through the optical path L1 in the atmosphere or vacuum.
Through the first interference filter 46 for active species of CF-based gas
Light having a predetermined wavelength is extracted, and the intensity of the light, that is, the emission intensity is converted into an electric signal by the first photoelectric converter 48. The electric signal indicating the emission intensity of the active species is amplified by the first amplifier 72 of the processing system 5 and then passes through the first low-pass filter 74 to extract only low frequency components, for example, components having a frequency of 10 Hz or less. This signal is sampled by the first A / D converter 76 at a frequency of, for example, four times or more the above frequency, digitized, and input to the determination unit 78. On the other hand, the reflected light from the half mirror 44 passes through the optical path L2 in the atmosphere or vacuum and enters the second interference filter 50 for reaction products to extract the light of a predetermined wavelength, and the intensity of the light, that is, the light emission. The intensity is converted into an electric signal by the second photoelectric converter 52.

The electric signal indicating the emission intensity of the reaction product is amplified by the second amplifier 82 of the processing system 5 and then passes through the second low-pass filter 84 to have a low frequency component, for example, 10 Hz or less as described above. Is extracted, and this signal is sampled by the second A / D converter 86 at a frequency of, for example, four times or more of the above frequency, digitized, and input to the determination unit 78. Then, the determination unit 78 including a microcomputer or the like detects the end point of etching based on the variation of the ratio of the emitted light intensity that has been input. The determination unit 78 considers that the etching operation has ended in response to the fluctuation value having changed by a predetermined value or more, and outputs an etching end signal to the overetching circuit 88 in the subsequent stage. Upon receiving the etching end signal, the overetching circuit 88 recognizes this as an overetching start signal, and further performs overetching processing for a time preset in this timer circuit. In practice, the determination of the end of etching is made, for example, always based on the average of the fluctuation values for the latest 10 seconds. Therefore, if the determination of the end of etching is made, the over-etching operation for 10 seconds has already been performed. However, since the actual overetching operation is performed for 10 seconds or more, no problem occurs.

Then, if overetching is performed for a predetermined time, this circuit 88 outputs an overetching end signal to the high frequency power supply control circuit 90 in the subsequent stage. Upon receiving this over-etching end signal, the high-frequency power supply control circuit 90 immediately shuts off the power supply of the high-frequency power supply 14 and completes the etching operation. In the present embodiment, the emission spectrum of CF ₂ radicals as the active species of CF-based gas is separated by the first interference filter 46, and the emission spectrum of the emission wavelength of CO gas as a reaction product and the emission wavelength of argon gas are separated. The spectral regions are both 300 to 800 nm and almost completely overlap each other, and since a large amount of argon gas is made to flow and the emission intensity thereof is also large, the emission of CO gas is buried and it is difficult to extract it. However, from a microscopic point of view, there are many emission peaks in the above spectral region. Therefore, in order to detect the emission intensity of CO gas, the amount of emission is small in the valley of the emission peak of argon gas, and
The emission intensity of CO gas is measured at a specific wavelength such that the emission amount of gas increases. For example, FIG. 4 is a graph showing an emission spectrum of argon gas when the resolution is increased. The peak wavelength is 480.6 nm and the peak wavelength is 480.6 nm.
There is an extremely small amount of light emission of argon gas between 4.6 nm, that is, a valley exists, and this portion, that is, a wavelength of 483.5 nm or 482.7 nm.
Is where CO gas emission is present.

Therefore, in this example, the second interference filter 50 was set to a wavelength of 482.7 nm, light of this wavelength was extracted, and the emission intensity from the CO gas, which was a reaction product, was measured. The CF ₂ gas, which is an active species, has a wavelength of 259.5 nm outside the spectral range of argon gas.
Since it has an emission peak at, the first interference filter 46
Was set to this wavelength and the emission intensity of CF ₂ gas was measured. FIG. 5 is a graph showing the emission intensity of each gas and its ratio when the actual etching is performed under the above conditions. In the graph, the change in emission intensity of both gases is corrected and described as a percentage. As shown in the figure, the emission intensity of CF ₂ gas and CO gas gradually decreases as the etching progresses. It is considered that the cause of this decrease in emission intensity is that the substrate temperature rises as the etching progresses. Then, the emission intensity of the CF ₂ gas slightly increases after passing the point which is considered to be the end point of etching, but if only this emission intensity is monitored, the above-mentioned increase amount causes fluctuations in the emission intensity of the CF ₂ gas. It is difficult to accurately grasp the etching end point because there is not much difference from the size. Further, when the emission intensity of CO gas exceeds the point where the etching end point is considered,
Although the slope is slightly steep, the emission end point alone cannot accurately grasp the etching end point as described above.

On the other hand, the value obtained by taking the ratio of the emission intensity of the CO gas and the CF ₂ gas is almost constant while fluctuating in the etching process, but rises sharply after a certain point, The amount of increase is equal to or larger than the fluctuation width of this value. After that, the ratio value becomes constant again, indicating that the etching is finished. As a result of measurement with a SEM (scanning electron microscope), a point that seems to be this etching end point, that is, an etching time of about 12
It was found that the point of 8 seconds was the actual etching end point. Therefore, by taking the ratio of the emission intensities of CO gas and CF ₂ gas and monitoring the amount of this change, etching was performed accurately and reliably. It becomes possible to detect the end point.
In this way, the end point of the etching is detected by monitoring the change in the ratio of the emission intensity of the active species and the reaction product, so that the fluctuations of both emission intensities are canceled out, and the sensitivity is theoretically improved. It can be doubled, and it becomes possible to reliably detect the etching end point of the semiconductor substrate having an aperture ratio of 10% or less, which has been difficult to detect conventionally.

When the over-etching time is set to, for example, 30 seconds, the above-mentioned etching end point becomes the over-etching start point, so that the point at which the etching time is approximately 158 seconds becomes the over-etching end point. In addition, the overlapping of spectra includes not only complete overlapping, but also partial overlapping such as overlapping of one spectrum with one hem during spectroscopic measurement. By the way, in such an etching process,
Due to the difference in the size of the semiconductor substrate 16, the processing step, the gas conditions, etc., the way the plasma in the chamber 6 stands is different,
As a result, the peak points of the emission intensity in the processing area A between the electrodes 8 and 10 are, for example, P1 and P as shown in FIG.
2 and P3 may move slightly, but if this is left and the focus F of the condenser lens 40 is always set to the point P1, the overall plasma emission intensity is weak or the emission intensity is low. If there is little variation in the above, it may not be possible to sufficiently capture the variation in the emission intensity.

In such a case, as a feature of the present invention, the moving mechanism 54 of the optical system 3 is driven by a control signal from the moving mechanism controller 53 or automatically.
The focal point F of the condenser lens 40 is always the emission peak points P1, P
2, P3. For example, the emission peak point is point P1
Z table 6 when moving from above to point P2
By raising 0, the focus F of the condenser lens 40 is moved to the point P2. Further, when the light emission peak point moves from the point P1 to the point P3 in the distance in the horizontal direction (depth of focus direction), the X table 68 is horizontally moved to the chamber 6 side and the focus F of the condenser lens 40 is moved to the point P3. .. Similarly, when the emission peak point moves from the point P1 in the vertical direction in the drawing, the Y table 64 is moved so that the focus F is always located at the emission peak point.

Thus, the focusing lens 40 is moved by moving the condenser lens 40 by the moving mechanism 54 which is movable in the XYZ directions.
Can always be positioned at the emission peak point of the processing region A, so that even a slight change in emission intensity can be reliably captured, and therefore the etching end point and the like can be reliably determined. In the above embodiment, it is possible to automatically perform the focus position control by separately providing a detector for obtaining the peak point of the emission intensity and inputting this output to the moving mechanism control unit 53. Further, in the conventional apparatus, for example, an optical fiber was used as a light guide medium for the optical system for catching the emission intensity of plasma, but this optical fiber is selected in this embodiment even though it has a good light transmittance. In such a short wavelength range, the light absorptivity becomes relatively high, and for example, about 50% of the light is absorbed, so that the variation in the emission intensity may not be sufficiently captured.

In such a case, the optical system 3 in this embodiment can be used in the air without using any optical fiber or the like.
Alternatively, since light emitted straight in a vacuum is directly introduced into the photoelectric converters 48 and 52 through a filter or the like, there is almost no loss of light in the optical path, and therefore light can be detected with high sensitivity even with low light emission intensity. It is possible to almost surely capture even minute fluctuations in the emission intensity, and it is possible to reliably determine the end point of etching and the like. Further, in the etching process, products tend to adhere to the lowest temperature of the apparatus due to the nature of the etching gas, but generally, the observation window 28 provided in the chamber 6 is used.
Is lower than other parts, so this observation window 2
Since the product adheres to the inner surface of 8 and becomes cloudy, and a sufficient amount of light emission cannot be extracted, the etching end point cannot be detected, or the observation window 2 is often used to extract a sufficient emission intensity.
I had to do the cleaning operation of 8.

In such a case, since the observation window 28 in this embodiment is provided with the adhered matter removing means 30 as shown in FIG. 3, the heater power source 34 is driven by driving the removing means 30. From the above, the ceramic heater 32 is energized, and the entire observation window 28 is heated to a temperature at which products and the like do not adhere, for example, around 100 ° C. The heating temperature at this time is monitored by the thermocouple 36 and is fed back, and the control unit 38 receiving the signal from the thermocouple 36 ensures that the temperature of the observation window 28 always maintains the above predetermined value. The heater power supply 34 will be controlled. The heating operation of the observation window 28 may be performed constantly during the etching process, or after the etching process is completely completed. In this way, by preventing the products and the like from adhering to the observation window 28 during the etching process, it is possible to emit the plasma to the outside of the observation window 28 without loss of the light emission amount, and thus the emission intensity. Since it is possible to reliably detect even a slight fluctuation in the area, it is possible to reliably detect the etching end point and the like, and it is not necessary to manually perform the cleaning operation of the observation window.

Although a heater such as a ceramic heater 32 is provided as the deposit removing means 30 in the above embodiment, the present invention is not limited to this, and the local plasma generating mechanism 100 as shown in FIG. 6 is used. It may be provided. Specifically, an opening 102 is formed in the side wall of the chamber 6, and a cylindrical observation window 104 formed by quartz glass or the like in a recessed cross section having a diameter of about 20 mm and a length of, for example, about several tens of mm is formed in this portion. It is airtightly attached and fixed through the O-ring 106. A high-frequency coil 108 is wound around the outer periphery of the cylindrical observation window 104, and a matching circuit 110 is wound around the high-frequency coil 108.
An RF generator 112 provided with is connected so that cleaning plasma can be generated only in the concave observation window 104. This RF generator 112 is driven by RF
Performed by the control unit 114, for example, after the etching process is completed, a cleaning gas such as O ₂
By introducing the gas into the chamber 6 and driving the RF generator 112, plasma is locally generated only in the concave observation window 104. The processing condition at this time is, for example, 1
A high frequency of 3.56 MHz is output at 40 W for about 30 seconds.

As a result, the observation window 1 is used during the etching process.
The product adhered in 04 is sputtered and removed by the locally generated plasma. Therefore, at the same time as the above, the cloudiness of the window 104 disappears and the light emission amount in the chamber can be taken out without being lost. Such a cleaning operation is performed every time the process is completed or every lot, and is performed while recognizing the adhesion state of the product by, for example, a monitor device (not shown) provided outside the window 104.
In particular, since the cleaning plasma is locally generated, it does not sputter the chamber 6. In addition, the RF generator 112 described above is not used alone, but is used as a high frequency power supply 1 for plasma processing.
4 may be switchable and shared. Further, the deposit removing means 30 of this type is not limited to the plasma etching apparatus described in the present embodiment, but may be applied to a processing apparatus such as an asher apparatus or a CVD apparatus that may adhere to the inner wall of the container. All can be applied.

In the above example, the etching end point and the like were detected based on the ratio of the emission intensity of the active species and the emission intensity of the reaction product. However, if the amount of light emission decreases during etching and the reduction rate is different between the two wavelengths, it is difficult to determine the end point even if the ratio of the two wavelengths is simply taken. Therefore,
Predetermined arithmetic processing for these emission intensities, as described below,
That is, the end point can be detected very simply by calculating the ratio after performing the arithmetic processing for making the slopes of the change curves of the emission intensity of the two coincide with each other. That is, the light emission intensity gradually changes with the progress of etching in a change curve as shown in FIG. FIG. 7A shows changes in the emission intensity of the active species (the output CH0 of the first photoelectric converter 48) and changes of the emission intensity of the produced gas (the output CH1 of the second photoelectric converter 52). The determination unit 78 first (1) calculates the average value A of the designated section of such a change curve.
VE0 and AVE1 are calculated, and (2) the absolute value of the difference between the N measured values CH0 and CH1 in the specified section and the average values AVE0 and AVE1 is calculated to obtain the specified section average A0 and A1 (area calculation). A0 = Σ | CH0-AVE0 | / N A1 = Σ | CH1-AVE1 | / N (3) Take the ratio R of the designated section averages A0 and A1. R = A0 / A1

As described above, the average value AVE for the designated section
After calculating 0, AVE1 and the ratio R, the following calculation is performed on the output CH0 of the photoelectric converter 48 based on these coefficients to obtain the calculated value and the output CH of the photoelectric converter 52.
Calculate the ratio to 1. (4) Subtract the average value AVE0 from the measured value CH0. CH0 '= CH0-AVE0 CHO' is shown by the curve E in FIG. (5) Divide CHO 'by the ratio R. As a result, the slopes of the CH0 curve and the CH1 curve match. CH0 ″ = CH0 ′ / R CHO ″ is shown by the curve C in FIG. 2 (B). (6) Add the average value AVE1 of CH1 to CH0 ″.
This matches the CH1 curve. CH0 ′ ″ = CH0 ″ + AVE1 (7) The ratio R between the calculated value CH0 ′ ″ and the output CH1 is calculated. Then, it is determined when the value of the ratio has changed to a predetermined threshold value or more, which is set as the etching end point.

Although the output CH0 is converted by the coefficient in this example of operation, it goes without saying that the output CH1 may be converted. Further, the calculation of the determination unit 78 is
The method is not limited to the above-described method, and appropriate changes can be made, for example, by obtaining approximate curves of change curves of both outputs and matching the slopes of these approximate curves to obtain a ratio. Based on the above determination by the determination unit 78, the etching is finished automatically or manually. Further, when overetching is required depending on the object to be processed, the overetching timer circuit 8 starts from the time when the determination unit 78 determines the end point.
After the predetermined overetching time set in 8, the etching is finished.

In the above embodiments, the etching end point and the like are detected based on the emission intensity here, that is, the ratio of the emission intensity of the active species to the emission intensity of the reaction product. The present invention is not limited to this, and the etching end point or the like may be detected based on only the emission intensity of the active species, for example, which will be described below. This principle is because active species are consumed during the etching process due to the presence of the etching target, and when the etching target is exhausted, that is, when the etching end point is reached, the active species are not consumed and increase rapidly. The fact that the amount of emitted light also increases is used. In this case, the emission intensity detection system for the reaction product in FIG. 1, that is, the optical path L2 is cut off, and the emission intensity detection system for the active species, that is, the optical path L1 is used. Further, the determination unit 78 is programmed so that the etching end point is recognized when, for example, the variation of the emission intensity of the active species is equal to or more than a predetermined value.

First, a semiconductor substrate 16 having a silicon dioxide film formed on a silicon substrate is placed on the lower electrode 8, and a C—F type gas such as CHF ₃ is placed in the vacuum chamber 6.
Both the gas and the CF ₄ gas are introduced at a flow rate of 60 SCCM through the gas introduction pipe 20, and, for example, argon gas is added as an additive gas to stabilize the plasma.
Introduced through the gas introduction pipe 20 at a flow rate of 00 SCCM,
The gas pressure is set to, for example, 1.2 Torr by drawing a vacuum with a vacuum pump (not shown). Then, a high frequency power having a frequency of 13.56 MH and a power value of 750 W is applied between the electrodes 8 and 10 to generate plasma, and the SiO ₂ film on the substrate 16 is etched. At this time, the temperature of the substrate 16 is -50 to 4
Set to 0 ° C. Here, in this embodiment, the electrodes 8 and 10 are
C, which is one of the active species in the plasma state generated during
Focusing on the F ₂ radical, light having a wavelength of, for example, 262.8 nm in the emission wavelength of the CF ₂ radical is extracted using the first interference filter 46. Then, the determination unit 78 monitors the intensity of the dispersed light (emission intensity), determines that the time point when the plasma is stable, for example, increases by 1.4%, is the end point of the etching, and then performs overetching for a predetermined time. Apply and stop applying power.

In the above, there are a plurality of wavelengths of the emission spectrum of the CF ₂ radical. Among them, the wavelength is 262.8 nm.
Of the light (wavelength used in the example) and the light having a wavelength of 259.5 nm, the results of examining the emission intensity when the same etching as above is performed are shown in FIG. 8 as solid line (1) and dotted line (2), respectively. Shown in. However, the average of the emission intensity before and after etching is 100. As can be seen from this result, CF ₂
The intensity of light corresponding to the wavelength of the emission spectrum of radicals largely changes before and after the end of etching, and the rates of change are about 1.4% and 0.85%, respectively. In order to confirm that the time point when the emission intensity increases as described above is the etching end point, etching is performed under exactly the same conditions as described above, and immediately before the time point when the emission intensity increases significantly (for example, 1.4%). Substrate 1 when plasma generation is stopped
6 and the substrate 16 in the case where the plasma generation was stopped immediately after the large increase in the emission intensity, the surface was confirmed by SEM (electron scanning microscope) photographs, and the former (before the emission intensity change) substrate With respect to No. 16, the silicon dioxide film was very thin and the surface of the underlying single crystal silicon substrate was exposed from a part thereof, but in the latter, the surface of the single crystal silicon substrate was exposed over the entire surface. Therefore, it is proved that the CF ₂ radicals whose emission intensity is to be measured are involved in the etching, that is, the CF ₂ radicals directly react with the silicon dioxide film as shown in the following formula to remove it. ₂ + 2CF ₂ → SiF ₄ + 2CO

After the silicon dioxide film to be etched is removed, it increases by the amount consumed by the etching until then, and the end point of the etching can be detected by catching this increase. In this embodiment as well, by driving the moving mechanism 54 for moving the optical system 3, which is a feature of the present invention, the condenser lens 30 of the optical system 3 is appropriately moved in the X, Y, and Z directions. The focus F is always maintained at the emission peak point, and the emission peak point is always watched. Further, during the etching process, by driving the adhered matter removing means 30, the observation window 28 is heated and maintained at a predetermined temperature, the reaction products and the like are prevented from adhering to the observation window 28, and the emitted light intensity is controlled. Prevent it from falling.

Further, the optical system 3 directly detects the light from the condenser lens 40 without using an optical fiber or the like that causes light absorption. Therefore, even a slight change in the emission intensity can be recognized almost certainly, and thus the end of etching or the like can be surely determined. In the above-mentioned embodiment, when detecting the emission intensity of the active species, the emission around the wavelength of 260 nm is traced, but the wavelength is not limited to this range, and for example, CF ₂ is 240 to 380.
nm, CF ₁ , emission of 202.4, 208 nm is measured, and in the case of reaction product, for example, 210 nm to 236 nm
Range, especially wavelengths 219.0 nm, 230.0 nm,
211.2 nm, 232.5 nm and 224-229 n
At m, emission may be traced due to carbon monoxide or CO ⁺ ions. Further, in the above embodiment, CF-based and C used as etching gas are used.
Has been described using a CF _4, CH ₃ as HF-based gas is not limited thereto, the present invention other C ₂ F
₆ , C ₃ F ₈ , C ₄ F ₈ , CH ₂ F ₂ , CF ₃ Cl, C
₂ F ₅ Cl, CF ₂ Cl ₂ , CF ₃ Br and C ₂ F ₅ B
It can also be applied to the case where r or the like is used, or CCl ₄ is also used.

The present invention is not limited to the etching of a silicon dioxide film, but can be applied to the etching of a polysilicon film or an aluminum alloy film. The certain material may be a material other than single crystal silicon, such as a polysilicon oxide film. That is, the object to be processed is not limited to SiO _2, and polysilicon, silicon nitride, amorphous silicon, gallium arsenide (GaAs), aluminum (Al), or the like can be used. When gallium arsenide is used as the object to be processed, When CF ₄ —O ₂ gas is used as the etching gas, and when aluminum is used, CCl ₄ , BCl ₄ , SiCl ₄ or the like can be used. Further, the present invention can be applied to both a cathode coupling type etching apparatus having a substrate placed on the cathode side and an anode coupling type etching apparatus having a substrate placed on the anode side. It is also applicable to an etching method in which reactive gas plasma is generated in the discharge chamber by the above method and is guided to the etching region.

[0044]

As described above, according to the present invention, the following excellent operational effects can be exhibited. Since it is possible to always detect the light emission from the emission peak point of the plasma, without being affected by the standing of the plasma,
Even a slight change in the emission intensity can be detected almost certainly. Therefore, it is possible to reliably detect the end point of etching of the object having a low aperture ratio, which has been difficult to detect in the past.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a plasma processing apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing a moving mechanism used in the present invention.

FIG. 3 is a schematic configuration diagram showing an adhering substance removing unit.

FIG. 4 is a graph showing a part of an emission spectrum of argon gas.

FIG. 5 is a graph showing luminescence intensities of active species and reaction products and a temporal change in a ratio of these luminescence intensities.

FIG. 6 is a schematic configuration diagram showing a modified example of the adhered substance removing means.

FIG. 7 is a diagram for explaining a calculation when a specific calculation is performed on the emission intensity.

FIG. 8 is a characteristic diagram showing changes in emission intensity of CF ₂ radicals.

[Explanation of symbols]

 2 plasma processing means 3 optical system 4 monitoring means 5 processing system 6 vacuum chamber (reaction vessel) 8, 10 electrode 14 high frequency power supply 16 semiconductor substrate (object to be processed) 28 observation window 30 adhering matter removing means 32 ceramic heater (heating means) 34 Heater Power Supply 36 Thermocouple 38 Control Unit 40 Condenser Lens 42 Lens Container 44 Half Mirror 46 First Interference Filter 48 First Photoelectric Converter 50 Second Interference Filter 52 Second Photoelectric Converter 54 Moving Mechanism 56 Base 58 Elevating Means 60 Z table 64 Y table 68 X table 78 Judgment unit 88 Over-etching timer circuit 90 High frequency power supply control circuit 100 Local plasma generation mechanism A Processing area F Focus P1, P2, P3 Emission peak point

Claims (2)

[Claims] 1. A plasma processing apparatus having monitor means for monitoring the light emission from the plasma processing means via an optical system, wherein the optical system is provided with a moving mechanism capable of moving with respect to the plasma processing system. A plasma processing apparatus having the above configuration. 2. The plasma processing apparatus according to claim 1, wherein the moving mechanism includes an X table that moves in the X direction, a Y table that moves in the Y direction, and a Z table that moves in the Z direction.