JP2009206344A - Apparatus and method for processing plasma - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the rate of operation in a plasma processing apparatus and maintain appropriate plasma processing capacity for a long period. <P>SOLUTION: The plasma processing apparatus includes: a processing chamber which includes a substrate electrode 112 to place a substrate to be processed and a gas supply device 109 to supply a process gas at a specified flow rate; a vacuum discharge means 118 which can control pressure or gas density in the processing chamber and change gas discharging speed; and a mechanism 101 to generate plasma in the processing chamber. Thus, the density of a gas in the processing chamber is controlled uniform by the mechanism for measuring the density thereof based on the measured gas density. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a plasma processing technique for plasma processing a substrate to be processed, and relates to a plasma processing apparatus and a processing method suitable for preventing fluctuations in processing characteristics even for long-term plasma processing.

  In the plasma processing apparatus, if the plasma processing is continued for a long time, it may be difficult to maintain the initial processing performance. In this case, by performing some maintenance work, the state of the apparatus is initialized and the plasma processing is restarted. In many cases, the desired plasma processing performance cannot be obtained immediately after the maintenance work, and it is necessary to adjust the state of the plasma processing chamber or the like by performing preliminary discharge or the like. When the amount and frequency of such maintenance work and preliminary discharge increase, productivity deteriorates. For this reason, maintaining plasma processing characteristics over a long period of time is an important issue.

  For example, in the case of a plasma etching apparatus, the processing shape of the etching process gradually deteriorates due to a long-term etching process, or reaction products deposited in the processing chamber adhere to the substrate to be processed and the plasma processing characteristics deteriorate. There are things to do. As maintenance work in this case, removal of reaction products accumulated in the processing chamber and replacement of parts in the apparatus are often performed. However, these maintenance operations are usually performed with the processing chamber being evacuated to a vacuum state open to the atmosphere, and it often takes a long time to return the processing chamber to a usable state again.

  There is Patent Document 1 as a publicly known example relating to stabilization of plasma processing characteristics using the prior art. Patent Document 1 discloses that the plasma etching process is stabilized by monitoring the peak-to-peak voltage of the bias applied to the substrate to be processed and controlling it to a set value.

  Moreover, there is Patent Document 2 as a publicly known example relating to stabilization of plasma processing characteristics using the prior art. Patent Document 2 shows that both the opening degree and the bias voltage of the pressure control valve in the processing chamber are monitored, and maintenance is performed when one or both deviate from a preset value.

Moreover, there is Patent Document 3 as a publicly known example relating to stabilization of plasma processing characteristics using the prior art. In Patent Document 3, in plasma etching, self-bias voltage is measured, high-frequency power is adjusted based on the measured value, etching is performed, and high-frequency power is controlled so that the self-bias voltage measured in each batch becomes equal. Has been shown to do.
JP-A-8-199378 JP 2005-183756 A JP-A-8-165585

  However, the technique described in Patent Document 1 does not consider the cause of the change in the peak-to-peak voltage of the bias applied to the substrate to be processed. Therefore, it is not possible to prevent a change in plasma processing characteristics with time due to an unknown cause of a change in peak-to-peak voltage.

  Further, the technique described in Patent Document 2 does not take into account changes with time in plasma processing characteristics during maintenance. For example, it is not possible to prevent a change in plasma processing characteristics with time after the maintenance is performed until the next maintenance is performed.

  Further, the technique described in Patent Document 3 does not consider factors that cause the self-bias voltage to fluctuate. For this reason, it is impossible to prevent the time-dependent change in the plasma processing characteristics that is generated due to an unknown cause of changing the self-bias voltage.

  The present invention has been made in view of these problems, and provides a plasma processing technique capable of increasing the operating rate of a plasma processing apparatus and maintaining good plasma processing performance over a long period of time.

  In order to solve the above problems, the present invention employs the following means.

  A processing chamber provided with a substrate electrode for mounting a substrate to be processed and a gas supply device for supplying a processing gas at a predetermined flow rate, a vacuum exhaust means having a variable exhaust speed capable of controlling the pressure or gas density of the processing chamber, A plasma processing apparatus having a mechanism for generating plasma in the processing chamber is provided with a mechanism for measuring the gas density in the processing chamber, and the gas density in the processing chamber is controlled to be constant based on the measured gas density.

  Since the present invention has the above-described configuration, the operating rate of the plasma processing apparatus can be increased and good plasma processing performance can be maintained over a long period of time.

  Hereinafter, the best embodiment will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing an outline of a plasma etching apparatus according to the present embodiment. Microwaves oscillated from the microwave source 101 are transmitted using the rectangular waveguide 103 and connected to the circular waveguide 105 by the rectangular circular waveguide converter 104. The automatic matching machine 102 can automatically suppress the reflected wave by adjusting the load impedance. As the microwave source, a magnetron having an oscillation frequency of 2.45 GHz was used. An isolator 119 was used to protect the microwave source.

  The circular waveguide 105 is connected to the cavity resonance unit 106. The cavity resonance unit 106 has a function of adjusting the microwave electromagnetic field distribution to a distribution suitable for plasma processing. Below the cavity resonator 106 is a plasma processing chamber 110 via a microwave introduction window 107 and a shower plate 108. Since the shower plate 108 is directly exposed to the plasma generated in the plasma processing chamber 110, a material that has high plasma resistance and does not adversely affect the plasma processing is desirable. As a material for the microwave introduction window 107 and the shower plate 108, quartz was used as a material that efficiently transmits microwaves and keeps the plasma processing chamber airtight.

  A minute gap (not shown) is provided between the microwave introduction window 107 and the shower plate 108, and a gas supplied from a processing gas supply system 109 used for plasma processing is supplied. The shower plate 108 is provided with a plurality of fine gas supply holes (not shown) to supply the processing gas to the plasma processing chamber 110 in a shower shape. A substrate electrode 112 for placing a substrate to be processed 111 is installed in the plasma processing chamber 110. A bias power supply 114 is connected to the substrate electrode 112 via an automatic matching machine 113 in order to supply bias power to the substrate 111 to be processed. A frequency of 400 kHz was used as the frequency of the bias power source.

  A static magnetic field generator 115 is provided around the plasma processing chamber 110, and a static magnetic field can be applied to the plasma processing chamber 110. When the electron cyclotron resonance phenomenon, in which the microwave power is resonantly absorbed by electrons when the electron cyclotron frequency matches the microwave frequency, plasma is generated even in a high vacuum region where it is usually difficult to generate plasma. It becomes possible, and there is an effect that a region where plasma treatment can be performed is expanded. In addition, by applying a static magnetic field to the plasma processing chamber, plasma loss is suppressed and plasma ignitability is enhanced, and by adjusting the distribution of the static magnetic field, the plasma generation region and diffusion are controlled to control the plasma distribution. be able to. By controlling the plasma distribution, it is possible to control the uniformity of plasma processing performed on the substrate 111 to be processed. When the microwave frequency is 2.45 GHz, the magnitude of the static magnetic field that causes electron cyclotron resonance is 0.0875 Tesla. In this case, in order to utilize the electron cyclotron resonance phenomenon, it is necessary to generate a static magnetic field of 0.0875 Tesla in the plasma processing chamber, and a static magnetic field capable of generating a static magnetic field of this magnitude in any place in the processing chamber. It is desirable to use a magnetic field generator. A multistage electromagnet was used as a static magnetic field generator. By using a multi-stage electromagnet, there is an effect that the adjustment of the static magnetic field distribution and the size can be easily controlled by the current flowing through the electromagnet.

  The plasma processing chamber 110 is evacuated by a vacuum exhaust pump 118 connected through a valve 116 and a conductance variable valve 117. As the vacuum exhaust pump 118, a turbo molecular pump whose exhaust side was exhausted by a rotary pump was used. The pressure in the plasma processing chamber 110 is monitored by a pressure gauge 120. There is provided a mechanism for maintaining a constant pressure by automatically controlling the exhaust speed for exhausting a gas such as a gas supplied by the processing gas supply system 109 or a gas generated during the etching process using a conductance variable valve.

  In order to evaluate the long-term stability of the plasma etching characteristics, an experiment was carried out using the plasma etching apparatus shown in FIG. 1 to continue the etching process while monitoring the parameters of the apparatus. The processing chamber and parts inside the processing chamber were cleaned to initialize the apparatus, and the experiment was started. The monitored parameters are the temperature of the quartz top plate, the opening of the pressure regulating valve (denoted as VV opening), the emission intensity of the inert gas contained in the processing gas, and the peak-to-peak voltage (denoted as Vpp) of the bias voltage. . Further, an inert gas was added to the processing gas at the time of plasma etching, and the intensity of plasma emission due to the inert gas was also monitored. Furthermore, as a monitor of plasma etching characteristics, the line width when a linear pattern was processed by plasma etching was measured. A value obtained by subtracting the line width of the mask pattern from the line width of the formed linear pattern was evaluated, and expressed as a processing dimension in the figure. 7 and 8 show the initial value as 100%.

  When the etching process was continued, the temperature of the processing chamber represented by the temperature of the quartz top increased mainly due to heat input from the plasma. The evacuation speed of the evacuation system is adjusted by a conductance variable valve so that the processing chamber pressure during plasma processing is maintained at a predetermined value. However, the conductance of the conductance variable valve increases as the temperature of the processing chamber increases. Pumping speed increased. The intensity of plasma emission due to the inert gas tended to decrease. Furthermore, although the output of the bias power source is constant, the peak-to-peak voltage (Vpp) of the bias output decreases as the processing chamber temperature rises. In addition, the processing dimensions tended to become thinner.

  The increasing tendency of the exhaust speed is the result of the control that increases the exhaust speed and keeps the pressure constant because the gas temperature in the processing chamber rises and the pressure increases when the temperature of the processing chamber rises. Conceivable. The emission intensity of the inert gas is considered to be approximately proportional to the density of the inert gas, and a decrease in emission intensity is considered to indicate a decrease in gas density. Moreover, the decreasing tendency of Vpp is thought to be because the plasma density increased and the plasma impedance decreased. When the temperature rises at a constant pressure, the gas density decreases, but the relationship between the gas density and the plasma density varies depending on the gas molecule, and the gas density decreases due to the gas density decrease, and conversely the plasma density decreases due to the gas density decrease. There is an increasing gas. In the case of the halogen-based gas used in the experiment, the plasma density increased as the gas density decreased. In the case of a halogen-based gas, since the probability that electrons attach to gas molecules and generate negative ions is high, it is considered that the density of electrons increased due to a decrease in gas density. Therefore, the cause of the decrease in Vpp is considered to be a decrease in gas density. When Vpp is lowered, the energy of ions drawn from the plasma to the substrate to be processed is reduced, and it is considered that the processing dimension fluctuates accordingly.

  The above process is summarized as follows, and the inventor considered that an increase in the temperature of the gas used for the etching process caused a change in processing dimensions through a decrease in gas density and a decrease in Vpp.

(1) Process chamber temperature increase (2) Gas temperature increase (3) Gas density decrease by constant pressure control (4) Plasma density increase (5) Vpp decrease by constant bias power control (6) Variation in machining dimensions By the way, ideal gas It is known that the relationship between the gas temperature in the processing chamber and the gas density is expressed by equation (1).

PV = nRT (1)
Where P: processing chamber pressure (Pa)
V: Volume of processing chamber (m3)
n: amount of gas molecules (mol)
R: Gas constant (= 8.314 J / K / mol)
T: Gas temperature (K: Absolute temperature)
Strictly speaking, the equation (1) is not satisfied for an actual gas due to the size of gas molecules, but it may be considered that the equation (1) is approximately established. When the gas temperature fluctuates, the pressure in the processing chamber fluctuates substantially according to equation (1). When the processing chamber pressure is controlled to be constant as in the plasma processing chamber described above, it can be seen that when the gas temperature rises, the gas density decreases in order to maintain the pressure.

As for the actual gas, a formula obtained by correcting the formula (1) has been proposed for a long time, for example, Basic Physical Chemistry, Walter J. et al. It is described by Moore, Haruo Hosoya, Masako Yudasaka, Tokyo Kagaku Doujin, etc.

  From this result, in order to stabilize the etching characteristics represented by the etching rate, application of the following measures is effective.

(1) Stabilization of the processing chamber temperature In order to stabilize the processing chamber temperature, a heater is installed around the processing chamber and heated to a predetermined temperature, and a heater is installed on the quartz top plate and operated. After reaching the temperature, the processing chamber temperature is stabilized by starting the etching process. As a heater for heating the quartz top plate, a mechanism for irradiating the quartz top plate with electromagnetic waves that absorb energy may be used. The heater installed on the quartz top plate may be removed before starting the etching process.

  FIG. 2 is a diagram illustrating the processing chamber heating mechanism. There are a heater 201 for heating the side surface of the plasma processing chamber and a heater 202 for heating the microwave introduction window. The heater has a control mechanism that maintains a predetermined temperature while monitoring the temperature. In this example, both were set to 100 ° C. The heater 202 for heating the microwave introduction window is detachable, and is installed in the microwave introduction window and heated to a predetermined temperature before plasma processing. After reaching a predetermined temperature, the heater 202 is removed and plasma processing is started. When the plasma treatment is continued and the temperature near the microwave introduction window is stable, the heating of the microwave introduction window by the heater 202 can be omitted. The heating of the microwave introduction window by the heater 202 is effective when a long time has elapsed after the previous plasma treatment, or when the microwave introduction window has cooled down, such as a vacuum exhaust time after opening to the atmosphere or the like.

  It is desirable to set the temperatures of the heater 201 and the heater 202 so that the surface of the processing chamber is close to the saturation temperature reached when the plasma processing is continued for a long time.

  It is also effective to stabilize the processing chamber temperature by heating the processing chamber with a gas heated prior to the plasma processing using a gas heating mechanism used for gas temperature stabilization described below. The gas flowing into the processing chamber for heating the processing chamber is preferably a chemically inert gas such as argon or nitrogen. Moreover, there is also an effect of discharging a substance that deteriorates plasma processing characteristics by previously removing reaction products and the like attached to the inside of the processing chamber by flowing a gas.

(2) Stabilization of gas temperature In order to stabilize the gas temperature, a heating mechanism is provided in the gas pipe, and the heated gas is supplied to the plasma processing chamber. Since it is difficult to directly monitor the gas temperature in the processing chamber, it is possible to stabilize the gas temperature by starting the etching process after confirming that the temperature of the quartz top plate reaches a predetermined temperature. it can.

  FIG. 3 shows a gas heating mechanism. A gas heating mechanism 301 is provided in a pipe for supplying a processing gas from the gas supply mechanism 109. The gas heating mechanism was set to 100 ° C. Since the heated processing gas passes through the gas flow path between the microwave introduction window 107 and the shower plate 108, it is desirable that the microwave introduction window 107 and the shower plate 108 are also heated. Therefore, it is desirable to preheat the microwave introduction window and the like using the method described in the stabilization of the processing chamber temperature described above prior to the plasma processing.

(3) Stabilization of gas density In order to stabilize the gas density, the gas density was measured by the measurement system shown in FIG. This gas density measuring system is used in place of or in combination with the pressure gauge 120 shown in FIG. A pressure gauge 403 is connected to a processing chamber 401 for measuring the gas density via a pipe 402 with a gas temperature control mechanism. In the pipe 402 with a gas temperature control mechanism, a porous ceramic material is installed inside the pipe, and gas molecules passing through the pipe collide with the ceramic material and are adjusted to the same temperature as the ceramic material. The ceramic material is controlled to a predetermined temperature from the outside. When the temperature of the ceramic material is lowered, reaction products at the time of plasma treatment may easily adhere, and it is desirable to set the temperature higher. In this example, the temperature was set to 100 ° C. The gas density can be calculated from the controlled gas temperature and the measured pressure and used for gas density control in the processing chamber. As the pressure gauge 403, it is desirable to use a pressure gauge having a mechanism for controlling the temperature of the pressure gauge itself to a predetermined value or having a function of correcting the pressure measurement value by measuring the temperature of the pressure gauge. Furthermore, when controlling the temperature of the pressure gauge 403, it is desirable to control to the same temperature as the piping 402 with a gas temperature control mechanism. In this embodiment, the pressure gauge 403 is controlled to 100 ° C.

  In the above example, the gas temperature is controlled to a predetermined value. However, the gas temperature may be monitored by measuring the temperature of the porous ceramics, and the gas density may be calculated from the obtained gas temperature and pressure.

  The ceramic material is preferably a material that is resistant to plasma damage, stable over a wide temperature range, and has a high heat transfer coefficient. In this embodiment, a ceramic mainly composed of aluminum oxide is used.

  When porous ceramics that allow gas molecules to pass through are used, there is an effect of increasing the temporal response of pressure measurement to fluctuations in the processing chamber pressure, but the controllability of gas temperature is reduced. Conversely, if porous ceramics that hardly allow gas molecules to pass therethrough are used in order to improve controllability of the gas temperature, the responsiveness deteriorates. It is necessary to select an optimum porous ceramic from the viewpoint of response speed and controllability of gas temperature.

  FIG. 5 is a view showing another example of the pipe 402 with the gas temperature control mechanism. The probability of collision of gas molecules with the inner surface of the pipe is increased by bending the temperature-controlled pipe, and the temperature of the gas passing through the pipe is controlled to a predetermined temperature by the temperature control mechanism 501. When there are many collisions between the inner surface of the pipe and gas molecules, the bending of the pipe may be omitted or a valve or the like may be provided in the middle.

  In the present embodiment, an example in which the gas density is calculated and controlled from the gas temperature and pressure has been described. However, when the gas temperature is controlled to be constant, the same effect can be obtained even if the pressure measured by the pressure gauge 403 is constant. Is obtained. Moreover, when measuring gas temperature, it replaces with gas density and calculates the pressure at the time of converting into predetermined gas temperature, and you may control using this. Usually, since the pressure in the processing chamber is often controlled to be constant, there is an effect of facilitating comparison with the conventional example.

  In the above example, the gas density is calculated from the measured value of the pressure gauge and the gas temperature, but a mechanism for directly measuring the gas density may be used. Moreover, although the example which controls by the piping etc. which temperature-controlled gas temperature was shown, the fluctuation | variation of gas temperature may be calculated using the pressure measured value at a certain time as a reference, and gas density correction may be performed.

  FIG. 10 is a diagram for explaining another example of a mechanism for measuring a gas density. A gas density meter 1004 is connected to the processing chamber 401. The gas density meter 1004 includes a plurality of measuring instruments 1002 and 1003 and a branch pipe 1001. It is desirable that the gas density can be measured correctly with one measuring instrument, but when the gas density cannot be measured stably according to the type and temperature of the gas, the gas density can be adjusted by using different measuring instruments 1002 and 1003 together. It can be measured. Measuring instrument 1002 and measuring instrument 1003 measure pressure or gas density according to different measurement principles. For example, the measurement instrument 1002 and the measurement instrument 1003 have different gas temperature dependencies of the pressure measurement values. For example, a measuring instrument that can stably measure pressure regardless of the gas temperature is used as the measuring instrument 1002, and a measuring instrument that changes the pressure indication value relatively depending on the gas temperature is used as the measuring instrument 1003. The pressure and gas temperature dependency of both measuring instruments are measured in advance and stored in a database. The gas temperature can be calculated from the pressure indication value of the measuring instrument 1002 and the pressure indication value of the measuring instrument 1003 from this database.

  FIG. 13 is a diagram for explaining a method for calculating a true pressure and a gas temperature using two measuring instruments having different gas temperature dependencies. FIG. 13 is a schematic diagram in which a true pressure is taken on the vertical axis, a gas temperature is taken on the horizontal axis, and a line indicating a constant pressure indication value of the measuring instrument is displayed. The dependence of the pressure indication value and the gas temperature on the true pressure of the measuring instrument 1002 and the measuring instrument 1003 is acquired in advance. The solid line 1301 displays the characteristics of the measuring instrument 1002, and the broken line 1302 displays the characteristics of the measuring instrument 1003. The true pressure and gas temperature can be calculated from the intersection of the lines corresponding to the pressure indication values of the measuring instrument 1002 and the measuring instrument 1003. In the example shown in FIG. 13, the measuring instrument 1002 shows a constant pressure indication value regardless of the gas temperature, and the measuring instrument 1003 shows a case where the pressure indication value is higher than the true pressure when the gas temperature is high. As apparent from FIG. 13, in order to accurately measure the gas temperature and the true pressure, it is desirable to select two measuring instruments having a large difference in characteristics with respect to the gas temperature of each measuring instrument. In other words, when the characteristics of the two measuring instruments are displayed as shown in FIG. 13, it is desirable that the two lines intersect at an angle close to 90 degrees near the intersection of the solid line 1301 and the broken line 1302 indicating the characteristics of the two measuring instruments.

  Next, a typical pressure measurement principle used in a pressure gauge will be briefly described below. First, the principle of pressure measurement used in a pressure gauge called a capacitance manometer will be described with reference to FIG. The capacitance manometer 1101 is separated into a measurement chamber 1102 connected by a pipe 1105 and a reference chamber 1103 separated by a partition wall 1104 so as to have the same pressure as the processing chamber 401. A known gas is sealed in the reference chamber 1103 and adjusted and held at a known pressure. The partition walls 1104 receive forces from collisions between the gas molecules 1107 in the measurement chamber 1102 and the gas molecules 1106 in the reference chamber 1103 from the surfaces in contact with the rooms. This force difference is caused by the pressure difference between the reference chamber 1103 and the measurement chamber 1102, and the pressure in the measurement chamber 1102 can be measured by measuring this force difference. This force is measured from the amount of deformation of the partition wall 1104. In many cases, the deformation amount of the partition wall 1104 is calculated by measuring a change in electrostatic capacitance with a surface (not shown) provided to face the partition wall 1104.

  As described above, the principle of pressure measurement using a capacitance manometer directly measures the force applied to the partition wall by pressure, and it can be expected that the correct pressure is exhibited even if the gas temperature in the measurement atmosphere changes. However, there are many cases where the force applied to the partition wall is very small, and when measuring this small force, disturbances such as ambient temperature may occur, and commercially available capacitance manometers are devised to minimize the influence of the disturbance. There are many cases.

  Next, the measurement principle of pressure used in a pressure gauge called a Pirani gauge will be described with reference to FIG. A Pirani gauge 1201 is connected to the processing chamber 401 for measuring pressure. The Pirani gauge 1201 has a linear high-temperature part 1203 inside, and takes heat by the gas molecules 1202 in the measurement atmosphere colliding with the high-temperature part 1203. The atmospheric pressure can be measured by measuring the amount of heat taken from the high temperature part 1203. In general, at low pressure, the number of gas molecules that collide is small and the amount of heat lost is small, but at high pressure, the collision frequency of gas molecules is high and a large amount of heat is lost. In the commercially available Pirani gauge, for example, tungsten or platinum material is often used for the high temperature portion 1203. The high temperature part 1203 is heated by flowing an electric current, and the pressure is often calculated from the amount of heat taken when the temperature is kept at a constant temperature of about 200 ° C., for example.

  The Pirani gauge does not measure pressure directly, but measures the amount of heat lost and converts it to pressure. In general, since the heat transfer in the gas differs depending on the gas type even at the same pressure, the Pirani vacuum gauge has a difference in the pressure measured by the gas type. Moreover, since the pressure is measured by heat transfer to the measurement atmosphere gas, it is easily affected by the gas temperature.

  Thus, the capacitance manometer and the Pirani vacuum gauge have different dependencies on the gas temperature, and can be used as the measuring instrument 1002 and the measuring instrument 1003 in FIG. However, other measuring instruments 1002 and measuring instruments used as the measuring instrument 1003 only need to have different pressure indication value characteristics with respect to the gas temperature, and other measuring instruments or measuring methods may be used.

  Although the method for measuring the gas density by using a combination of measuring instruments having different characteristics in FIG. 13 has been described, the temperature and pressure of the gas follow the relationship of the equation (1). Gas density or temperature can be measured by preparing pressure measurement data. The gas density or gas temperature may be measured using the method described in Procedure 1 to Procedure 3 below.

Step 1
The apparatus is adjusted to a predetermined exhaust speed while the temperature of the apparatus is stable, and a predetermined gas at a predetermined flow rate is flowed to measure the pressure in the processing chamber to obtain a reference pressure P0 [Pa]. The gas temperature in this state is defined as an absolute temperature T0 [K]. In addition, when each part of the apparatus is at room temperature, the gas density (a value obtained by dividing the amount of gas molecules by the volume of the processing chamber) may be calculated according to Equation (1) assuming that the gas temperature is normal temperature.

Step 2
The pressure in the processing chamber is measured under the same conditions as in the case of measuring the reference pressure in Procedure 1 (a predetermined exhaust velocity and a predetermined flow of a predetermined gas are allowed to flow). The measurement result at this time is P1 [Pa]. The estimated gas temperature is defined as an absolute temperature T1 [K], and T1 is calculated by Equation (2).

T1 = (P1 / P0) * T0 (2)
Step 3
The gas density (value obtained by dividing the amount of gas molecules by the volume of the processing chamber) is obtained according to the equation (1).

(4) Stabilization of plasma density The following measures are effective to suppress fluctuations in plasma density.

1. 1. Control of microwave power for plasma generation Stabilization of Gas Density FIG. 6 is a diagram for explaining control of microwave power for plasma generation. As described above, a bias voltage is applied to the substrate to be processed through the automatic aligner and the substrate electrode. The peak-to-peak voltage (hereinafter referred to as Vpp value) of the bias voltage is measured by the Vpp monitor 601, and the monitor value is transmitted to the controller 602. The bias voltage applied to the substrate electrode, the substrate to be processed, and the plasma is divided according to the respective impedances. However, since the impedance of the substrate electrode and the substrate to be processed is low, the peak-to-peak voltage is almost applied to the plasma. Therefore, it is possible to monitor the impedance fluctuation of the plasma with the measured value of the Vpp monitor. Furthermore, since the plasma density fluctuation is directly reflected in the plasma impedance, the plasma density fluctuation can be monitored as a result of the Vpp value. When the bias power is constant, a high Vpp value corresponds to a low plasma density and a low Vpp value corresponds to a high plasma density.

  As described above, the plasma density can be monitored by the Vpp value. The plasma density can be controlled by microwave power. The plasma density can be monitored by the Vpp value, and the plasma density can be controlled by the microwave power. The controller 602 determines that the plasma density has increased when the Vpp value decreases, and sends a low microwave output setting signal to the microwave oscillator 603. The microwave oscillator 603 outputs microwave power according to the microwave output setting signal, and the output microwave power is monitored by the microwave output monitor 604. Conversely, when the Vpp value increases, the controller 602 performs the reverse operation. The operation of the controller can stabilize the plasma density.

(5) Stabilization of Bias Peak-to-Peak Voltage FIG. 9 is a diagram illustrating a system for applying a bias potential to a substrate to be processed. The output from the bias power source is transmitted to the substrate electrode unit via the automatic matching machine. The substrate electrode portion mainly includes a temperature control mechanism for the substrate to be processed and a holding mechanism for the substrate to be processed. The holding mechanism for the substrate to be processed was an electrostatic chuck mechanism. The substrate electrode part is provided with a voltage detection part for monitoring the voltage. Since the voltage of the substrate to be processed greatly affects the plasma processing characteristics, it is desirable to directly monitor the voltage of the substrate to be processed. However, since the substrate to be processed is held by the electrostatic chuck mechanism, it is difficult to directly monitor the voltage of the substrate to be processed. A voltage detector is provided on the bias power source side of the electrostatic chuck mechanism, and the voltage at this position is Is being monitored.

  Since the electrostatic chuck mechanism works as a capacitor having a large capacity electrically, the voltage drop with respect to the high frequency is small, and the high frequency voltage of the substrate to be processed may be effectively monitored. However, the electrostatic chuck mechanism has a large impedance in terms of direct current, and the direct current potential of the substrate to be processed cannot be monitored at the position of the voltage detector shown in FIG. If you want to detect the potential of the substrate to be processed with higher accuracy, measure the impedance of the substrate holding mechanism in advance, and add a detection unit for the current flowing through the path in addition to the voltage detection unit. By calculating and correcting the voltage drop at, the potential of the substrate to be processed can be monitored more accurately.

  A voltage signal from the voltage detector 112 is transmitted to the controller 901. The controller 901 sends a power signal for controlling the output power of the bias power supply 114 to the bias power supply so as to keep the voltage of the substrate 111 to be processed at a desired value.

  The present invention is not limited to the plasma etching apparatus shown in FIG. 1, but can be applied to plasma etching apparatuses using other plasma generation methods.

  As described above, according to the present embodiment, by stabilizing parameters related to plasma processing such as plasma processing chamber temperature, gas temperature in the plasma processing chamber, gas density, plasma density, and bias peak-to-peak voltage, The operating rate of the plasma processing apparatus is improved and productivity can be improved.

It is a figure showing the outline of the plasma etching device concerning an embodiment. It is a figure explaining a process chamber heating mechanism. It is a figure explaining the heating mechanism of gas. It is a figure explaining the measurement system of a gas density. It is a figure which shows the other example of piping with a gas temperature control mechanism. It is a figure explaining control of the microwave electric power for plasma generation. It is a figure explaining the change of a processing dimension. It is a figure explaining the change of a processing dimension. It is a figure explaining the system | strain which applies a bias potential to a to-be-processed substrate. It is a figure explaining the other example of the mechanism which measures a gas density. It is a figure explaining the measurement principle of the pressure used with a capacitance manometer. It is a figure explaining the measurement principle of a Pirani gauge. It is a figure explaining the method of calculating a true pressure and gas temperature using two measuring instruments from which gas temperature dependence differs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Microwave generator 102 Automatic matching machine 103 Rectangular waveguide 104 Rectangular circular waveguide converter 105 Circular waveguide 106 Cavity resonance part 107 Microwave introduction window 108 Shower plate 109 Gas supply apparatus 110 Plasma processing chamber 111 Processed Substrate 112 Substrate electrode 113 Automatic alignment machine 114 Bias power supply 115 Static magnetic field generator 201 Heater 202 Heater 301 Gas heating mechanism 401 Processing chamber 402 Pipe with gas temperature adjustment mechanism 403 Pressure gauge 501 Temperature adjustment mechanism 601 Vpp monitor 1001 Branch pipe 1002 Measuring instrument 1003 Measuring instrument 1004 Gas density meter 1101 Capacitance manometer 1102 Measurement chamber 1103 Reference chamber 1104 Bulkhead 1105 Pipe 1106 Gas molecule 1107 Gas molecule 1201 Pirani vacuum gauge 1202 Gas molecule 1203 in measurement atmosphere High temperature Part 1301 Characteristic 1302 of Measuring Instrument 1002 Characteristic of Measuring Instrument 1003

Claims (7)

A processing chamber including a substrate electrode on which a substrate to be processed is placed and a gas supply device for supplying a processing gas at a predetermined flow rate;
Evacuation means with variable evacuation speed capable of controlling the pressure or gas density of the processing chamber;
A plasma processing apparatus including a mechanism for generating plasma in the processing chamber;
A plasma processing apparatus comprising a mechanism for measuring a gas density in the processing chamber and controlling the gas density in the processing chamber to be constant based on the measured gas density. The plasma processing apparatus according to claim 1,
The gas density measuring mechanism includes a pressure gauge and a gas temperature measuring mechanism, and calculates a gas density from a pressure signal of the pressure gauge and a gas temperature signal of the gas temperature measuring mechanism. The plasma processing apparatus according to claim 1,
The gas density measuring mechanism includes a pressure gauge and a gas temperature control mechanism, and calculates a gas density from a pressure signal of the pressure gauge and a gas temperature signal of the gas temperature control mechanism. A processing chamber provided with a substrate electrode for mounting a substrate to be processed and a gas supply device for supplying a processing gas at a predetermined flow rate, a vacuum exhaust means having a variable exhaust speed capable of controlling the pressure or gas density of the processing chamber, In a plasma processing apparatus having a mechanism for generating plasma in a processing chamber,
A mechanism for measuring the pressure in the processing chamber, a mechanism for measuring the temperature of a gas that fills the inside of the mechanism for measuring the pressure, and a mechanism for calculating a pressure when converted into a predetermined temperature from the measured temperature and pressure of the gas The plasma processing apparatus is characterized in that the processing chamber pressure when converted to a predetermined temperature is controlled to be constant. A processing chamber provided with a substrate electrode for mounting a substrate to be processed and a gas supply device for supplying a processing gas at a predetermined flow rate, a vacuum exhaust means having a variable exhaust speed capable of controlling the pressure or gas density of the processing chamber, In a plasma processing apparatus having a mechanism for generating plasma in a processing chamber,
A plasma processing apparatus comprising: a mechanism for controlling a temperature of a gas that fills an inside of a mechanism that measures the pressure in the processing chamber and controls the processing chamber pressure to be constant, to a predetermined value. A processing chamber provided with a substrate electrode for placing a substrate to be processed and a gas supply device for supplying a processing gas at a predetermined flow rate, a vacuum exhaust means with variable exhaust speed capable of controlling the pressure or gas density of the processing chamber, and the processing In a plasma processing apparatus equipped with a mechanism for generating plasma in a room,
A plasma processing apparatus comprising a mechanism for controlling the gas temperature in the processing chamber, and performing plasma processing by controlling the gas temperature in the processing chamber to a predetermined value. A processing chamber equipped with a substrate electrode for placing a substrate to be processed and a gas supply device for supplying a processing gas at a predetermined flow rate, a mechanism for measuring the pressure of the processing chamber, and the pressure or gas density of the processing chamber can be controlled. In a plasma processing apparatus comprising a vacuum exhaust means with variable exhaust speed, a control means for controlling the vacuum exhaust means, and a mechanism for generating plasma in the processing chamber,
A plasma processing method characterized by calculating a gas density in a processing chamber and controlling the calculated gas density in the processing chamber to a predetermined value.

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