JP2011002345A - Instrument and method for measuring gas decomposition ratio near plasma or in plasma - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate the decomposition ratio of a gas from a result obtained by measuring special distribution to the plasma of "quartz vibrator sensor calibration value change quantity" cleared in a correlation with the decomposition ratio of the gas and extrapolating the shape of the result of the spacial distribution to the vicinity and a position of the plasma to calculate the "quartz vibrator sensor calibration value change quantity" in that place.SOLUTION: The measurement by a quartz vibrator sensor 1 which can measure a quantity depending on the physical property value (viscosity and molecular weight) of the gas in the reactor 3 of a plasma device, an absolute pressure gauge 2 and a thermometer 18 is performed, the calibration of pressure and a temperature is performed from the output of a quartz vibrator sensor at the time of the generation of the plasma to obtain the quantity depending on the component change of the gas in the plasm device and the decomposition ratio of the gas near the plasma and in the plasma can be calculated from the shape of the spacial distribution of the change quantity to the presence of the plasma of the calibration value of the quartz vibrator sensor.

Description

  The present invention relates to a method and an apparatus for measuring a gas decomposition rate existing in a reaction apparatus, and more particularly to a measurement apparatus and a method for obtaining a decomposition rate and a consumption rate of gas as a stable molecule supplied in a gas phase such as plasma.

  Conventionally, various types of processing using plasma have been performed in the field of semiconductor manufacturing equipment and the like. In such a device using plasma, measuring the gas decomposition rate, that is, the consumption rate, not only contributes to the improvement of gas utilization efficiency, but also maintains the plasma in a state suitable for processing, and the accuracy and efficiency of the processing. It is necessary to keep the constant.

In view of this, plasma measuring methods such as a plasma monitoring method, a plasma processing method, a semiconductor device manufacturing method, and a plasma processing apparatus have been proposed (see Patent Document 1).
Conventionally, a method and an apparatus for measuring a gas decomposition rate in a reaction tank are known (see Patent Document 2).
Further, by utilizing the fact that the quartz vibrator sensor output depends on the molecular weight and viscosity of the gas to be measured, the concentration (partial pressure) of each gas in the mixed gas composed of two kinds of gases can be obtained. Such a concentration measuring method in a binary gas mixture is already known (see Patent Document 3).

Japanese Patent No. 3873394 JP 62-272152 A Japanese Patent No. 3336384

The inventions described in Patent Documents 1 and 2 are methods for measuring the decomposition rate of gas in a reactor mainly composed of plasma, but it is indispensable to use a rare gas in both of the above two patents. Is the method. Therefore, it cannot be used when the introduction of the rare gas is inappropriate, such as when the introduction of the rare gas into the apparatus adversely affects the quality of the manufactured product.
Even when only one type of gas is used as the supply gas, various types of molecules, ions, and radicals are generated and exist in the gas phase of the plasma due to collisions between the supply gas and electrons. In the method described in Patent Document 3 in which the concentration in gas can be measured, the concentration of all substances present in the plasma gas phase cannot be measured, and the decomposition rate of the supply gas cannot be obtained.
In order to solve these points, the applicant has previously filed a "apparatus for measuring the supply gas decomposition rate of a plasma apparatus and a measuring method" as Japanese Patent Application No. 2008-205384. Although the decomposition rate can be measured, since it is difficult to measure in the vicinity of the plasma and in the plasma, the gas decomposition rate at these locations cannot be obtained.

The present application further improves the previously filed Japanese Patent Application No. 2008-205384, and measures the spatial distribution by moving the crystal resonator sensor in the apparatus, and actually measures from the shape of the spatial distribution. However, it is necessary to provide a technique for obtaining the gas decomposition rate in and near the plasma, which is difficult but important information.
By applying the value of the gas decomposition rate, which is determined by gas analysis, away from the plasma to the spatial distribution of the gas decomposition rate, and extrapolating the result to the vicinity of the plasma and the position of the plasma, the gas decomposition rate at these points can be calculated. Desired.

The amount of change due to the presence or absence of “physical property-dependent output”, which is an output that depends on the physical properties of the gas to be measured, such as a crystal resonator sensor (“crystal resonator sensor calibration value change amount”) obtained by gas analysis Since it correlates with the decomposition rate, once the correlation between the "quartz crystal sensor calibration value change amount" and the gas decomposition rate is obtained, the gas decomposition rate by plasma can be obtained. Japanese Patent Application No. 2008-205384 filed earlier uses this to measure the gas decomposition rate, and the outline is described below.
In the crystal sensor measurement, an apparatus capable of measuring a gas decomposition rate without introducing a gas unnecessary for manufacturing other than a gas necessary for processing is provided. Specifically, using a crystal sensor that can output an output that depends on physical properties such as viscosity and molecular weight of the gas present in the device (physical property-dependent output), it is directly attached to the production device in-situ, and plasma discharge Measure before and after to obtain the physical property dependent output.
Since the difference in the "crystal oscillator sensor calibration value change amount" before and after plasma discharge has a good correlation with the gas decomposition rate, this measurement allows the gas decomposition rate to be as simple as pressure measurement without using other gases. It can be obtained on the spot of the device with a simple measurement. The absolute value of the gas decomposition rate can be obtained by separately performing a gas analysis using a mass spectrometer or the like, creating a calibration curve for comparison, and comparing it.
One of the specific physical property dependent outputs can be obtained by the above-described crystal resonator sensor. It has been found that the output of this crystal resonator sensor depends on the molecular weight and viscosity of the gas to be measured, and the impedance of the electric circuit including the crystal resonator in this sensor. Therefore, a physical property-dependent output that depends on the molecular weight and viscosity of the gas can be obtained by using a quartz oscillator sensor.
By utilizing the fact that the crystal resonator sensor output depends on the molecular weight and viscosity of the gas to be measured, the concentration (partial pressure) of each gas in the mixed gas composed of two kinds of gases can be obtained. Such a concentration measuring method in a binary gas mixture has already been patented (see Patent Document 3).
When a piezoelectric element including a crystal resonator such as a crystal resonator sensor is used, measurement can be performed by a simple method similar to measuring pressure. Is practical and can be easily measured. Furthermore, since the measurement method does not irradiate heat or light, it is possible to safely measure even a highly reactive gas mixture in which explosion occurs due to stimulation by heat or light. The measurement does not require an ultraviolet lamp having a specific wavelength, and maintenance is easy. Therefore, the decomposition rate of the supplied gas can be measured without using a complicated and manufacturing apparatus such as gas analysis as in the prior art or a measuring method that affects the manufacturing process.
In the above method, the value of the gas decomposition rate is obtained from the result of gas analysis using a quadrupole mass spectrometer (QMS). Since gas sampling is required for this gas analysis measurement, in order to prevent the sample tube used for this sampling from directly acting on the plasma, measurement must actually be performed at a position away from the plasma. The gas decomposition rate inside cannot be determined.

Therefore, the spatial distribution of the “quartz crystal sensor calibration value change”, which is known to correlate with the gas decomposition rate, is measured with respect to the plasma, and the shape of the spatial distribution is extrapolated to the vicinity of the plasma and the position of the plasma. By doing so, we have devised to find the "crystal oscillator sensor calibration value change amount" and to obtain the gas decomposition rate from the result.
Such a spatial distribution can be measured by performing a measurement by spatially changing the position of the measurement part of the measuring device even in gas analysis. However, in the case of QMS, for example, in order to obtain the spatial distribution, ionization is used. When moving the measuring head section, which is an area, the measuring head mounting section needs to have a sufficient length in order to move spatially. It is necessary to prepare a special order product.
On the other hand, since the size of the measurement using the quartz crystal sensor is small, it is possible to easily perform the measurement by changing the spatial relative position with respect to the plasma. The spatial distribution for can be obtained.
By correlating the actual gas decomposition rate at the position where the gas analysis is performed, the gas decomposition rate in the vicinity of the plasma and in the plasma can be obtained from the “crystal oscillator sensor calibration value change amount”.
The method of obtaining the “quartz crystal sensor calibration value change amount” is the same as that in the above application, as will be described later.

The plasma reactor of the present invention has the following excellent effects.
(1) In a plasma using a gas as a medium, it is possible to obtain the decomposition rate of the gas introduced into the container in which the plasma is present using only a quartz crystal sensor and an absolute pressure gauge. In this measurement, high-speed measurement is possible without consuming the gas measured at the time of measurement, and it can always be measured even when the pressure of the mixed gas is other than atmospheric pressure or even when the pressure changes. Furthermore, if the quartz crystal sensor is moved in the device and spatial distribution measurement is performed, the result is fitted with an exponential function, and extrapolation to the vicinity of the plasma and the position in the plasma is actually difficult to measure. Gas decomposition rates at these important locations can be determined.
(2) When a piezoelectric element including a crystal resonator is used, since it is a measurement method that does not irradiate heat or light, it is possible to safely measure even a highly reactive gas mixture that causes an explosion due to stimulation by heat or light. it can. The measurement does not require an ultraviolet lamp having a specific wavelength, is easy to maintain, and can immediately measure the composition in response to changes in the gas composition.

FIG. 1 is a diagram for explaining the configuration of an embodiment of the present invention. FIG. 2 shows the absolute values of the crystal sensor output (upper figure (a)), the display pressure of the quartz crystal pressure gauge (lower left figure (b)), and the indicated pressure of the spinning rotor gauge (lower right figure (c)). It is a graph which shows the relationship with a pressure. FIG. 3 is a diagram showing the temperature dependence of the crystal resonator sensor output. FIG. 4 is a diagram showing the definition of the time change of the quartz oscillator sensor calibration value and the change amount of the quartz oscillator sensor calibration value with respect to plasma generation / stop. FIG. 5 is a diagram showing a correlation between the amount of change in the calibration value of the quartz crystal sensor and the decomposition rate of ammonia gas when plasma is generated. FIG. 6 is a diagram of the results of gas analysis using a mass analyzer in ammonia gas (black bar) and plasma (white bar). FIG. 7 is a diagram of the spatial distribution of the quartz oscillator sensor calibration value change amount. FIG. 8 is a diagram of the spatial distribution of the gas decomposition rate obtained from the quartz sensor sensor calibration value change amount. FIG. 9 is a diagram showing the spatial distribution of silane and germane gas in a direction parallel to the parallel plate surface in plasma.

The gas decomposition rate measuring method and apparatus in the vicinity of and in the plasma according to the present invention measures the gas decomposition rate in the vicinity of the plasma and in the plasma with a simple method and apparatus as compared with the conventional plasma diagnostic method. A method and apparatus are provided.
Specifically, for the gas in the plasma device, the physical property dependent output depending on the physical property is measured according to the presence or absence of the plasma, respectively, and from the shape of the spatial distribution of the difference of the physical property dependent output caused by the presence or absence of the plasma The decomposition rate in the vicinity of the plasma of the gas supplied to the apparatus and in the plasma is obtained.

The present invention provides a device for measuring a physical property dependent output depending on a physical property value of a gas existing in a reactor of each plasma device before and after the generation of the plasma and calculating the change, and supplying from the change amount of the physical property dependent output In the apparatus for measuring the supply gas decomposition rate of a plasma apparatus equipped with a device for determining the gas decomposition rate, from the spatial distribution of the gas decomposition rate in the apparatus obtained by moving the probe in the apparatus, in the vicinity of the plasma It is characterized in that the gas decomposition rate of is obtained.
Further, the present invention measures the physical property dependent output depending on the physical property value of the supply gas supplied into the reactor of the plasma device before the plasma generation, and the physical property of the gas in the reactor of the plasma device after the plasma generation. Supply of a plasma apparatus comprising: a device that measures a physical property dependent output depending on a value and calculates a change in the physical property dependent output before and after plasma generation; and a device that determines a decomposition rate of a supply gas from the change in the physical property dependent output In the gas decomposition rate measuring device, the gas decomposition rate in the vicinity of the plasma and in the plasma is obtained from the spatial distribution of the gas decomposition rate in the device obtained by moving the measuring element in the device.
Further, the apparatus of the present invention is characterized in that the apparatus for calculating the change in the physical property dependent output before and after the generation of the plasma includes a crystal oscillator sensor and an absolute pressure gauge.
The device of the present invention is further characterized in that the physical property dependent output depends on viscosity and molecular weight.
In addition, the present invention measures the physical property dependent output depending on the physical property value of the gas existing in the reactor of each plasma device before and after the plasma generation, detects the change, and supplies it from the amount of change in the physical property dependent output. In the method for measuring the gas decomposition rate of the plasma apparatus for determining the gas decomposition rate, the gas decomposition rate in the vicinity of the plasma and in the plasma is determined from the spatial distribution of the gas decomposition rate in the apparatus obtained by moving the probe inside the apparatus. It is characterized by seeking.
Further, the present invention measures the physical property dependent output depending on the physical property value of the supply gas supplied into the reactor of the plasma device before the plasma generation, and the physical property of the gas in the reactor of the plasma device after the plasma generation. In a method for measuring a supply gas decomposition rate of a plasma apparatus, by measuring a property-dependent output depending on a value, calculating a change amount of the property-dependent output before and after plasma generation, and obtaining a decomposition rate of the supply gas from the change in the property-dependent output The gas decomposition rate in the vicinity of the plasma and in the plasma is obtained from the spatial distribution of the gas decomposition rate in the apparatus obtained by moving the probe in the apparatus.
The method of the present invention is further characterized in that a quartz oscillator sensor and an absolute pressure gauge are used to detect a change in physical property dependent output before and after the generation of the plasma.
The method of the present invention is further characterized in that the physical property dependent output depends on viscosity and molecular weight.

Hereinafter, the best mode of a gas decomposition rate measuring apparatus and method according to the present invention will be described in detail with reference to the drawings. However, the present invention is not construed as being limited thereto, and the present invention is not limited thereto. Various changes, modifications, and improvements can be made based on the knowledge of those skilled in the art without departing from the scope of the invention.
FIG. 1 is a diagram for explaining the entire configuration of a plasma processing apparatus to which an embodiment of a supply gas decomposition rate measuring apparatus and method according to the present invention is applied. The present invention measures the physical property dependent output depending on the physical property of the gas in the reactor of the plasma device depending on the presence or absence of plasma, and the shape of the spatial distribution of the difference in the physical property dependent output caused by the presence or absence of the plasma From this, the decomposition rate of the gas supplied to the reactor of the plasma device is determined in the vicinity of the plasma and in the plasma.
In FIG. 1, the physical property values are viscosity and molecular weight, and the quartz vibrator sensor 1, the diaphragm pressure gauge 2, and the thermometer 18 that can measure quantities depending on the physical properties are used to measure the crystal vibration when plasma is generated. By performing pressure and temperature calibration from the child sensor output, an amount depending on the gas component change in the apparatus is acquired. The gas decomposition rate in the vicinity of the plasma and in the plasma is determined from the shape of the spatial distribution of the change amount of the quartz resonator sensor calibration value with respect to the presence or absence of the plasma. A specific method is shown below.

  The above physical properties are viscosity and molecular weight, and measurement with a quartz vibrator sensor, absolute pressure gauge and thermometer that can measure quantities depending on this, and pressure and temperature calibration from the quartz vibrator sensor output when plasma is generated To obtain the amount corresponding to the gas component change in the apparatus. Furthermore, the spatial distribution of the change amount of the quartz resonator sensor calibration value with respect to the presence or absence of the plasma is obtained by moving the quartz resonator sensor in the apparatus for the above measurement. From the shape of this spatial distribution, the decomposition rate of the supply gas in and near the plasma, which is actually difficult to measure, is obtained. The specific apparatus and method will be described below.

  The plasma processing apparatus includes a reaction apparatus 3 of the plasma apparatus, a plasma electrode 5 projecting from the reaction apparatus 3 of the plasma apparatus that supplies a high-frequency voltage from the high-frequency power supply 10, and a plurality of gas flow rates for introducing a plurality of types of supply gases. A plurality of introduction pipes having a control device (mass flow controller: MFC) 7, a quartz crystal sensor 1 having a size of 1 cm or less, a diaphragm pressure gauge 2, a heater 8 for increasing the production temperature, and a product 12 The workpiece support 15, the pressure control valve 9, and the mass spectrometer 19 for analyzing the gas in the plasma are provided.

  The apparatus for measuring the decomposition rate of the supply gas of the plasma apparatus according to the present embodiment receives a physical property dependent output from the plasma apparatus and obtains a “quartz crystal sensor calibration value” which is an amount depending on a gas component in a gas phase. Pressure correction means 4 and temperature correction means 6 are provided. Specifically, the pressure correction unit 4 and the temperature correction unit 6 use a computer 17 having an input unit, an output unit, a CPU, a storage device, and the like (not shown).

  The quartz vibrator sensor 1 and the diaphragm pressure gauge 2 are connected to the input unit of the computer 17 via a data line. The quartz oscillator sensor calibration value is obtained by directly using the data obtained by the pressure correction means 4 or by using the data obtained by further processing the data by the temperature correction means 6 if necessary.

  The pressure correction means 4 inputs measurement data from the quartz oscillator sensor 1 and the diaphragm pressure gauge 2 and corrects the influence of absolute pressure from the output of the quartz oscillator sensor 1. If the temperature change during measurement is large, the pressure-corrected value (pressure correction value) is output to the temperature correction means 6, and if not, this value is used as it is as a calibration value for the crystal oscillator sensor. .

  The temperature correction means 6 inputs the pressure correction value and information on the resonance frequency of the crystal resonator having a large correlation with the temperature generated from the crystal resonator sensor 1 or the ambient temperature obtained by actual measurement. The calibration value of the crystal resonator sensor is obtained by performing correction.

  The upper diagram (a) of FIG. 2 is a graph showing the absolute pressure dependence of the crystal resonator sensor output in each gas, and the lower left diagram (b) of FIG. 2 shows the absolute value of the display pressure of the crystal resonator manometer. It is a graph which shows pressure dependence, and the lower right figure (c) of FIG. 2 is a graph which shows the absolute pressure dependence of the instruction | indication pressure of a spinning rotor gauge.

  As shown in FIG. 2A, the output of the crystal resonator sensor 1 (not a crystal resonator sensor but a crystal friction vacuum gauge or a spinning rotor gauge) at the same absolute pressure differs depending on the type of gas. By utilizing this, it is possible to measure changes in components in the plasma.

  In addition, not only in the pressure range shown in FIG. 2 (a), but also in all pressures, the output varies depending on the type of gas at the same absolute pressure depending on the type of gas. It is possible to measure component changes in plasma.

  Here, the quartz friction pressure gauge has a built-in quartz oscillator sensor oscillated by electricity, and the resistance generated when gas molecules collide with the quartz vibrator sensor depends on the pressure and viscosity of the gas. It is a pressure gauge which measures by taking out as a voltage of the electric circuit containing a sensor.

  A spinning rotor gauge is a pressure gauge that stops power after rotating a steel ball, etc. at high speed in a gas, and uses the fact that the rate of decrease in the number of rotations after this power stop is also dependent on the pressure and viscosity of the gas. It is.

  Since the component measurement in the present invention utilizes the fact that the output of the quartz oscillator sensor (or quartz friction vacuum gauge or spinning rotor gauge) differs at the same absolute pressure depending on the type of gas, Measurement with both the child sensor 1 and the diaphragm pressure gauge 2 is necessary. When there is no substantial change in absolute pressure as under atmospheric pressure, measurement can be performed by measuring only the crystal resonator sensor 1.

  By removing the influence of the absolute pressure from the output of the crystal resonator sensor 1, the crystal resonator sensor calibration value is obtained. Specifically, first, the absolute pressure dependence of the crystal resonator sensor output as shown in FIG. 2A is examined, and a pressure coefficient which is a change rate with respect to the pressure of the output is obtained. This pressure coefficient can be used to correct the change in the output due to the absolute pressure change.

If the measurement device output, measurement pressure, and pressure coefficient are V, P, and C, respectively, the pressure correction value V _p is V _p = V−C × (P with respect to the absolute pressure P ₀ at an arbitrary point. obtained by the -P _0). This pressure corrected value V _p is the quantity that correlates with the molecular weight and viscosity of the gas, it is possible to measure the change in the gas component by using this value.

  In order to correct the influence of the temperature, the ambient temperature at the measurement location of the crystal resonator sensor 1 is simultaneously measured by the thermometer 18, or from the information on the resonance frequency having a large correlation with the temperature obtained from the crystal resonator sensor 1, The temperature coefficient of the crystal oscillator sensor output as shown in FIG. 3 is obtained and temperature correction is performed. FIG. 3 is a graph showing the measured ambient temperature dependence of the crystal resonator output under a constant pressure condition.

  Since the correlation between the quartz crystal sensor output and temperature is constant, the quartz crystal sensor output value is calculated using the previously calculated quartz crystal sensor output-the slope of the temperature line, that is, the temperature coefficient of the quartz crystal sensor output. By calibrating, it is possible to eliminate the influence of temperature change and obtain the quartz crystal sensor calibration value.

If the measurement device output, measurement temperature, and temperature coefficient are V, T, and K, respectively, the temperature correction value V _t is V _t = V−K × (with respect to the absolute temperature T ₀ at an arbitrary point. (T−T ₀ ). Since the vibration frequency of the crystal resonator has temperature dependency, the temperature coefficient of the crystal resonator sensor output can be obtained from the temperature dependency of the vibration frequency.

  The method for obtaining the decomposition rate in the vicinity of the plasma of the supply gas first introduced into the apparatus using the “crystal crystal sensor calibration value”, which is a physical property-dependent output obtained by the above method, is as follows. .

  First, before the plasma is generated, the crystal resonator sensor calibration value is obtained by performing the above-described measurement and pressure / temperature calibration in the apparatus into which the supply gas is introduced. Next, plasma is generated, and measurement and pressure / temperature calibration are performed in the same manner to obtain a quartz oscillator sensor calibration value. The decomposition rate of the supply gas can be obtained from the amount of change in the calibration value of the quartz vibrator sensor with respect to the plasma.

  The result when ammonia is actually used is shown in FIG. FIG. 4 is a plot of quartz resonator sensor calibration values against time on the horizontal axis. As can be seen from FIG. 4, the “quartz crystal sensor calibration value” changes as the plasma is generated. Here, the difference between the “quartz crystal sensor calibration value” before and after the plasma generation is defined as “a quartz crystal sensor calibration value change amount”.

  It is possible to change the decomposition rate of the supply gas by variously changing plasma conditions such as pressure, gas flow rate, electrode temperature, input discharge power, and electrode potential bias. Among the plasma conditions, when the input power is changed, the decomposition rate of the supply gas changes greatly, and the decomposition rate of the supply gas increases with the normal input power. Therefore, the above-described quartz crystal sensor was used for measurement by changing the input power.

  In FIG. 4, the increase in the “quartz crystal sensor calibration value” due to the plasma generation indicates that the average molecular weight and viscosity of the supply gas existing in the gas phase have decreased due to the plasma generation. This is qualitatively consistent with a report that nitrogen gas and hydrogen gas are generated by ammonia decomposition in ammonia gas plasma. Also from this, it is clear that the “crystal oscillator sensor calibration value change amount” correlates with the change in the supply gas composition caused by plasma, that is, the decomposition rate of the supply gas.

  As described above, the magnitude of the decomposition rate of the supply gas can be obtained from this “amount of change in quartz crystal sensor calibration value”. That is, if the amount of change in the quartz resonator sensor calibration value with respect to plasma is large, the decomposition rate of the supply gas is large, and if it is small, it is small.

In fact, as shown in FIG. 5, the “crystal oscillator sensor calibration value change amount”, which is the difference between the “crystal oscillator sensor calibration values” before and after plasma generation, increases with respect to the plasma discharge power, and the decomposition rate of the supplied gas Correlate with
Here, the gas decomposition rate on the vertical axis in FIG. 5 is obtained as follows by performing gas analysis with 19 mass analyzers, for example. FIG. 6 shows the result of mass spectrum obtained by performing gas analysis when plasma is generated. Comparing the plasma before (black bar) and the plasma (white bar), it can be seen that the signal of mass number 17 which is the mass number (molecular weight) of ammonia is decreased by the plasma. By dividing this decrease by the amount of ammonia present first, the decomposition rate of the ammonia gas by the plasma can be obtained. Actually, the gas decomposition rate R _dis is expressed by the following expression (1) when the signal intensity of mass number 17 before and after the plasma is I _gas and I _pla , respectively. The rate can be determined.
_Rdis = (I _gas -I _pla ) / I _gas (1)

  As described above, a conventional gas analysis method is required to produce a calibration curve as shown in FIG. 5 for obtaining the decomposition rate of the supply gas from the “crystal oscillator sensor calibration value change amount”. It is sufficient to perform the gas analysis once in advance, and once a calibration curve for the decomposition rate of the supply gas is obtained, the supply gas is decomposed only by measurement with a quartz crystal sensor without performing gas analysis. The rate can be easily determined.

  The physical properties that depend on the physical property dependent output required by the quartz crystal sensor are viscosity and molecular weight. For example, the viscosity is measured by a quartz crystal pressure gauge and a spinning rotor gauge in addition to the quartz crystal sensor. It is calculated by removing the influence of absolute pressure measured with an absolute pressure gauge such as a diaphragm vacuum gauge.

  In addition, when it is obvious that the gas in the plasma apparatus is one or two kinds, a calibration curve is separately prepared for the partial pressure of each gas and mixed gas, and this is used as a calibration curve. The partial pressure of gas can be obtained. This is essentially the same as the patent (Patent Document 3).

  If the quartz vibrator sensor is covered with a cover made of an insulator that does not conduct charged particles from the plasma, disturbance to the plasma can be prevented during measurement.

  Since the crystal oscillator sensor is small and can move within the apparatus, it can be measured by moving with respect to the fixed plasma electrode in the apparatus.

When determining the decomposition rate of the supply gas, for example, it is optimal to measure between discharges between parallel plate electrodes, but if this is not possible under some conditions, the plasma electrode can be used as much as possible. It is desirable to measure at a close location.
In this case, if the distance to the electrodes of the quartz crystal sensor is smaller than the distance between the parallel plates, the direct influence of the plasma on the quartz crystal sensor becomes large and the measurement becomes inaccurate. It is preferable to measure at a position separated by the distance between the plate electrodes.
However, since gas due to plasma is generated in the plasma electrode, it is very effective to determine the gas decomposition rate in the vicinity of the plasma electrode and in the plasma electrode. The gas decomposition rate in the vicinity of plasma that is actually difficult to measure as described above or in plasma that is almost impossible to measure is obtained by moving the crystal sensor in the device. It can be obtained from the spatial distribution of “quantity”. A specific method is as follows.

As shown in FIG. 1, the quartz resonator sensor can be measured by spatially moving in the apparatus. As a result, the spatial distribution of the “crystal oscillator sensor calibration value change amount” due to the plasma can be obtained. An example is shown in FIG.
As shown in FIG. 7, it can be seen that the “quartz crystal sensor calibration value change amount” becomes larger as the crystal vibrator-plasma electrode distance (Z) becomes smaller, that is, closer to the plasma. The above results are due to the fact that the “crystal oscillator sensor calibration value change amount” corresponds to the gas decomposition rate, and that the closer to the plasma, the higher the gas decomposition rate is reflected. It is done.
The detection portion of the mass spectrometer that performs gas analysis spatially corresponds to Z = 70 mm in FIG. Therefore, the “quartz crystal sensor calibration value change amount” at Z = 70 mm corresponds to the gas decomposition rate obtained by the gas analysis as described in the above paragraph 0038, and can be related to the value.

As shown in FIG. 5, since there is a correlation between the “crystal oscillator sensor calibration value change amount” and the gas decomposition rate, the spatial distribution in FIG. 7 can be directly converted into the value of the gas decomposition rate. The result of the spatial distribution of the gas decomposition rate, which is the result, is shown in FIG.
From the shape of the spatial distribution of FIG. 8, the gas decomposition rate in the vicinity of the plasma and in the plasma, which is actually difficult to measure, can be obtained as follows.
In FIG. 8, the spatial distribution occurs because gas decomposition actually occurs only in the plasma, and gas decomposition does not occur in the outer region corresponding to Z> 0 mm. This is because a difference occurs depending on the presence or absence of gas decomposition in the steady state after passing through. The change corresponding to gas decomposition occurs when Z> 0 where no gas decomposition actually occurs, because the product of gas decomposition diffuses to this region.

In a situation where gas decomposition occurs only in the plasma and not elsewhere, the shape of the spatial distribution due to diffusion of the gas decomposition products is, for example, that the radioactivity of the radioactive material is exponential with respect to time. It is assumed that it takes a shape that decreases exponentially as it decreases.
Actually, when the result of FIG. 8 is fitted with an exponential function, it is very well in agreement with the measurement result as shown by the line in FIG. 8, and it can be seen that the approximation with the above exponential function is correct.
Assuming that the spatial distribution of the gas decomposition rate can be approximated by an exponential function, the gas decomposition rate in the vicinity of the plasma where Z = 0 is calculated by extrapolating this function to Z = 0, which is the original plasma position. be able to. In this case, the gas decomposition rate (R) is related to the distance (Z).
R = R ₀ · exp (−k · z) (2)
It is represented by Here, R _{0 and} k are constants related to the gas decomposition rate and diffusion at Z = 0, respectively.

Now, when obtaining the fitting equation to the result of FIG.
R = 35.0 · exp (-0.0013 · Z)
Therefore, Z = 0 mm, that is, the gas decomposition rate at the plasma electrode end is determined to be 35%.
Further, if it is assumed that the gas decomposition rate is distributed in the same function in the plasma, the gas decomposition rate in the plasma can be similarly obtained using the equation (2).
Since the radius of the plasma electrode of the apparatus used is 52 mm and the plasma center in FIG. 8 corresponds to Z = −52 mm, this is substituted into equation (2), and the gas decomposition rate in the plasma is determined to be 37%. It is done.

  In this calculation, the gas concentration is assumed to change exponentially even in the plasma. However, in plasma, this assumption that “the concentration distribution changes exponentially” may not hold. The concentration distribution in the plasma mainly depends on the energy of electrons generated from the electrodes, which depends on the electric field between the parallel plate electrodes. However, since this electric field also changes depending on the gas pressure or the like, the gas concentration distribution in the resulting plasma cannot be uniquely formulated. In such a case, the gas concentration spatial distribution in the plasma can be estimated by actually measuring the spatial distribution of some chemical species in a plane parallel to the electrode surface. For example, the spatial distribution of the gas in the plasma can be obtained as shown in FIG. 9 using coherent anti-Raman Stoke spectroscopy (CARS) as in the literature (JAP, vol. 61, p. 3055, 1987). By making the distribution a gas distribution, the gas decomposition rate in the plasma can be obtained. In addition, the spatial distribution measurement of this chemical species can use the method using light emission, such as an emission spectroscopic analysis method, instead of CARS.

As described above, the gas decomposition rate at these positions can be obtained from the shape of the spatial distribution even in the vicinity of plasma or in the plasma where actual measurement is difficult.
Of course, since these are the most important places in the plasma, it is very useful to determine the gas decomposition rate in the plasma by such measurements.

  In the measurement near the plasma electrode, the effect of temperature becomes prominent. To correct this effect, another temperature measurement is performed, or the resonance frequency obtained from the quartz oscillator sensor and highly correlated with the temperature is measured. As described above, the physical property value output is calibrated by correcting the temperature to obtain the quartz resonator sensor calibration value.

The consumption rate of the gas can be easily obtained from the decomposition rate of the supply gas obtained as described above, and effective knowledge for improving the utilization efficiency of the gas and reusing the unused gas can be obtained.
Furthermore, since a gas decomposition rate calibration curve is created, the gas decomposition rate can be obtained in real time at any time during the generation of plasma, so monitoring using this becomes possible, and various conditions can be set if necessary. By adjusting, it can manufacture, maintaining a desired decomposition rate.
In addition, when this real-time property is used, it is possible to control conditions in the plasma. Since the gas decomposition rate is one of the important conditions in the manufacturing conditions, if the gas decomposition rate is known, the product can be sophisticated by performing modulation control in real time. In addition, the product can be made uniform and uniform.
When an abnormal discharge of plasma occurs, the gas decomposition rate in the plasma changes greatly. By monitoring this abnormal change in the gas decomposition rate, abnormal operation of the plasma and plasma stop can be detected early.
The plasma conditions for controlling the gas decomposition rate include each supply gas flow rate, total pressure in the apparatus, high frequency power and frequency, product temperature / electric field, plasma electrode temperature / electric field, apparatus temperature, gas phase temperature in the apparatus, etc. is there. All of these can be quickly controlled by electrical signals. On the other hand, since the measurement output by this measuring apparatus can also be output as an electrical signal, quick result output and quick control by this are possible. If the gas component change is always measured during the plasma operation by this measurement method, even if the initially assumed gas decomposition rate changes due to some abnormality, the change is detected by detecting the deviation by this measurement method. When a significant difference appears in the component change, the gas decomposition rate can be maintained at a desired value by applying feedback to the flow rate of the supply gas.
By using a gas decomposition rate measuring apparatus capable of rapid measurement, a simple, small and inexpensive film thickness / film forming speed / film structure automatic control apparatus can be provided.
In particular, in the silane-hydrogen binary system used in the manufacturing process of thin film silicon, the gas decomposition rate of the material gas affects important physical properties such as the film structure (amorphous or microcrystalline) to be manufactured and light stability. Therefore, if the correlation between the physical properties and the gas decomposition rate is obtained in advance, the characteristics of the product can be kept constant by measuring the gas decomposition rate by this method during the actual process.
Similarly, the correlation between various properties such as film thickness, electrical properties, and aspect ratio in etching and the gas decomposition rate is obtained, and these conditions are used during actual process to control process conditions. can do.

  Since the gas decomposition rate measuring method and apparatus according to the present invention has the above-described configuration, it can be applied to various manufacturing apparatuses that perform processing, machining, and manufacturing using a plasma apparatus.

DESCRIPTION OF SYMBOLS 1 Crystal oscillator sensor 2 Diaphragm pressure gauge 3 Reaction apparatus of plasma apparatus 4 Pressure correction means 5 Plasma electrode 6 Temperature correction means 7 Gas flow control apparatus (mass flow controller: MFC)
DESCRIPTION OF SYMBOLS 8 Heater 9 Pressure control valve 10 High frequency power supply 12 Product 15 Work support stand 17 Computer 18 Thermometer 19 Mass spectrometer

Claims (8)

  Before and after plasma generation, a device that measures the physical property dependent output depending on the physical property value of the gas present in the reactor of each plasma device and calculates the change, and the decomposition rate of the supply gas from the amount of change in the physical property dependent output In the apparatus for measuring the gas decomposition rate of a plasma apparatus provided with a device for determining the gas decomposition rate in the vicinity of the plasma and in the plasma from the spatial distribution of the gas decomposition rate in the apparatus obtained by moving the probe in the apparatus An apparatus for measuring a supply gas decomposition rate of a plasma apparatus, wherein:   Before the plasma generation, the physical property dependent output depending on the physical property value of the supply gas supplied into the reactor of the plasma device is measured, and the physical property dependency depending on the physical property value of the gas in the reaction device of the plasma device after the plasma generation. In a supply gas decomposition rate measuring apparatus for a plasma apparatus, comprising: an apparatus for measuring output and calculating a change in physical property dependent output before and after plasma generation; and a device for determining a decomposition rate of supply gas from the change in physical property dependent output A supply gas decomposition rate measuring device for a plasma device, wherein the gas decomposition rate in the vicinity of the plasma and in the plasma is obtained from the spatial distribution of the gas decomposition rate in the device obtained by moving the probe in the device.   The apparatus for calculating a supply gas decomposition rate of a plasma apparatus according to claim 1 or 2, wherein the apparatus for calculating a change in physical property dependent output before and after plasma generation includes a quartz vibrator sensor and an absolute pressure gauge.   The supply gas decomposition rate measuring apparatus for a plasma apparatus according to any one of claims 1 to 3, wherein the physical property dependent output depends on viscosity and molecular weight.   Before and after the generation of the plasma, the physical property dependent output depending on the physical property value of the gas existing in the reactor of each plasma device is measured and the change is detected, and the decomposition rate of the supply gas is obtained from the change amount of the physical property dependent output. In the method for measuring the supply gas decomposition rate of a plasma device, the gas decomposition rate in the vicinity of the plasma and in the plasma is obtained from the spatial distribution of the gas decomposition rate in the device obtained by moving the probe in the device. A method for measuring the gas decomposition rate of a plasma apparatus.   Before the plasma generation, the physical property dependent output depending on the physical property value of the supply gas supplied into the reactor of the plasma device is measured, and the physical property dependency depending on the physical property value of the gas in the reaction device of the plasma device after the plasma generation. In the method for measuring the supply gas decomposition rate of the plasma apparatus, which calculates the amount of change in the physical property dependent output before and after plasma generation and calculates the decomposition rate of the supply gas from the change in the physical property dependent output, A gas decomposition rate measurement method for a plasma apparatus, characterized in that the gas decomposition ratio in the vicinity of the plasma and in the plasma is obtained from the spatial distribution of the gas decomposition ratio in the apparatus obtained by moving the gas.   7. A method for measuring a supply gas decomposition rate of a plasma apparatus according to claim 5, wherein a quartz vibrator sensor and an absolute pressure gauge are used to detect a change in physical property dependent output before and after the plasma generation.   The method for measuring a supply gas decomposition rate of a plasma apparatus according to any one of claims 5 to 7, wherein the physical property dependent output depends on viscosity and molecular weight.