JP2008118017A - Plasma processing method and processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent instability of plasma at the time of switching of plasma treatment conditions when step switching is performed while plasma discharge is continued in a plasma treatment method. <P>SOLUTION: The method of plasma treatment uses a plasma treatment apparatus that is provided with a plasma treatment chamber, a high frequency power supply for generating plasma and an automatic matching machine which automatically reduces reflected power of the high frequency power supply for generating plasma. In this case, plasma treatment conditions after switching of treatment conditions are previously determined (step 1). Test discharge is performed under the treatment conditions after switching and the position of matching elements is recorded at the time of reduction in reflected wave by the automatic matching machine (step 2). When the plasma treatment conditions are switched, the automatic matching machine is moved to the position of the matching elements which is previously recorded (step 3). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus capable of performing high-quality plasma processing.

  In plasma processing apparatuses using conventional techniques, plasma processing is often divided in time and optimum processing conditions are set for each. For example, in a plasma etching apparatus, a film on a substrate to be etched may be formed of a multilayer film, and plasma processing may be performed by sequentially switching processing conditions corresponding to each film type. Hereinafter, such switching of plasma processing conditions is referred to as step switching.

  FIG. 2 shows the result of monitoring the state of the apparatus when switching steps while continuing plasma discharge. This example is a case where the plasma impedance change is small and does not cause a problem in step switching. As monitor values, traveling wave power of high frequency power for plasma generation, high frequency reflected power, plasma emission intensity, and matching element position of an automatic matching machine were taken. The upper diagram in FIG. 7 shows the monitor values of the traveling wave power, the high frequency reflected power, and the plasma emission intensity of the plasma generating high frequency power, and the lower diagram shows the monitor values of the position of the matching element of the automatic matching machine. The high frequency power for plasma generation is supplied from a high frequency power source to an antenna disposed in the processing chamber via an automatic matching machine. The automatic matching machine is composed of a combination of three matching elements. The plasma processing conditions are such that only the coil current value described later is switched, and the high frequency power for plasma generation is not changed. Step switching was performed at time zero. As shown in FIG. 2, the plasma emission intensity is slightly reduced by step switching, and the reflected power is slightly increased by changing the plasma impedance. Corresponding to the plasma impedance change, the matching elements of the automatic matching machine are operated to suppress the reflected wave.

  When switching each of the plasma processing conditions separated in terms of time as described above while plasma discharge is continued, the plasma may become unstable, for example, the plasma density may be extremely reduced immediately after switching. In general, high-frequency power is often used to generate plasma. When the plasma processing conditions are switched during plasma discharge, characteristics such as plasma density change, and accordingly, the impedance of plasma with respect to high frequency changes. If the impedance variation of the plasma is large, the high-frequency reflected waves used for plasma generation increase, and the power absorbed by the plasma decreases. Usually, an automatic matching machine is often used for the high-frequency transmission path for plasma generation, and the reflected wave is always kept to a minimum. However, if the plasma changes rapidly, the matching operation of the automatic matching machine will follow. In some cases, the reflected waves cannot be suppressed. When the reflected wave increases, the plasma absorbed power decreases and the plasma density decreases. If the plasma density is significantly reduced, it may be difficult to maintain the plasma and disappear.

  FIG. 3 shows an example in which the apparatus state is monitored when the plasma density decreases and the plasma impedance changes immediately after switching. Plasma processing conditions were switched at time “0”. The monitor value is the same as in FIG. In addition, only the coil current value described later is switched as the plasma processing condition, and the high frequency power for plasma generation is not changed. As the plasma processing conditions were switched, the plasma emission intensity decreased, and the reflected wave increased and the traveling wave decreased. The high frequency power supply used in the experiment has a function of suppressing the output for protecting the power supply when an excessive reflected wave is detected. The reduction of the traveling wave shown in FIG. 3 is a result of the power protection function working. It is. Although the matching element of the automatic matching machine operates to suppress the reflected wave, the output suppression function for suppressing the reflected wave and protecting the power supply has not been completely canceled in a short time. The output suppression function for protecting the power supply promotes a decrease in plasma density when the plasma processing conditions are changed. Automatic matching machines often perform matching operations by mechanically driving matching elements. For this reason, the matching operation is relatively slow and may not be able to follow high-speed impedance changes.

  The instability of the plasma emission intensity at the time of step switching shown in FIG. 3 is that the plasma processing conditions can be switched at a relatively high speed, whereas the operation of the automatic matching machine is often relatively slow as described above. This is because it is impossible to follow the switching of the processing conditions. Although the impedance of the load changes at a relatively high speed with step switching, since the automatic matching machine cannot follow, the reflected wave is generated and the power absorbed in the load is reduced, resulting in instability at the time of switching. Below, it demonstrates quantitatively using numerical formula.

Consider a case where a high-frequency power source for generating plasma is connected to a processing chamber as a load via an automatic matching machine. The high-frequency reflection coefficient Γ at the input port of the automatic matching machine is expressed by the following equation (1).

In the above equation (1), Z _L is a load impedance composed of an automatic matching machine and a processing chamber, and Z ₀ is a characteristic impedance of a waveguide connected to the load. Since the plasma is generated in the processing chamber, the load impedance Z _L is changed by processing conditions. Further, the high frequency power absorbed by the plasma is expressed by the following equation (2) using the incident wave power P _f and the reflected wave power _Pr .

Since the square of the reflection coefficient is the ratio between the incident power and the reflected power, the power P absorbed by the plasma is expressed by the following equation (3) using Γ.

The transition from the plasma processing condition consisting of high-frequency power, gas type, pressure, static magnetic field distribution, etc. to another condition is hereinafter referred to as step switching. Immediately before the step switching, the automatic matching machine matches the impedance, and ideally, the reflected wave is suppressed as shown in the following equation (4).

From this point, assuming that the step impedance is changed and the plasma impedance is changed and the load impedance is changed from Z _L (= Z ₀ ) to Z ₁ , the reflection coefficient at this time is expressed by the following equation (5).

The greater the change in load impedance (Z ₀ -Z ₁ ), the greater the reflection coefficient and the smaller the power absorbed by the plasma. If the power absorbed by the plasma falls below the minimum required to maintain the plasma, the plasma will disappear.

  In a method of dry etching a wiring layer of a semiconductor device, it has been proposed to perform continuous discharge without evacuation at the time of transition from the breakthrough process to the main etching process or from the main etching process to the over etching process. (For example, refer to Patent Document 1). In this example, continuous discharge is performed without evacuation at the time of process transition. However, if the gas system used in each process is different, at least one process of changing the gas flow stepwise to stabilize the discharge is performed. It is necessary to insert more than one.

In plasma etching using an etching gas and a position gas, it has been proposed to synchronize the switching of the position gas and the on / off of the generated power of the plasma with the etching gas (see, for example, Patent Document 2). However, no consideration is given to continue the plasma when the etching process is switched.
JP 2002-343798 A Japanese Patent Laid-Open No. 2-105413

  As described above, the high frequency power input to the plasma processing chamber for generating plasma is usually input to the plasma processing chamber via an automatic matching machine. The automatic matching machine can suppress a reflected wave caused by impedance mismatching and consume predetermined high-frequency power in the plasma. However, the matching operation of the automatic matching machine is often performed by mechanically driving the matching element, and the matching operation often requires time on the order of seconds. A predetermined high-frequency power cannot be consumed by the plasma until the matching operation is completed, which may cause a problem in optimally controlling the plasma processing conditions. For example, when the plasma processing conditions are switched while the plasma is maintained, a high-frequency reflected wave is generated in accordance with a change in load impedance accompanying the switching of the processing conditions, and the plasma density may temporarily decrease. In some cases, the plasma could not be maintained when the density was significantly reduced.

  Among the parameters of the plasma processing, for example, the pressure in the processing chamber depends on the flow rate of the gas flowing into the processing chamber, the processing chamber temperature, and the exhaust speed of the processing chamber. Usually, the process chamber pressure is monitored by a pressure gauge, and the pressure is often controlled by adjusting a conductance variable valve for adjusting the exhaust speed of the process chamber. The conductance variable valve is often accompanied by a mechanical operation like the above-described automatic matching machine, and the process chamber pressure control often requires a relatively long time on the order of seconds. For this reason, there may occur a case where the predetermined pressure cannot be transiently controlled during step switching, which may cause a problem in highly accurate process control.

  In view of the above problems, an object of the present invention is to prevent plasma instability during switching of plasma processing conditions when step switching is performed while plasma discharge is continued in a plasma processing method and a plasma processing apparatus. Furthermore, in the plasma processing method and the plasma processing apparatus, the present invention achieves a reduction in foreign matters by suppressing the adhesion of foreign matters to the substrate to be processed by preventing plasma instability when switching the plasma processing conditions. In addition, the plasma processing characteristics can be optimized with high accuracy. Another object of the present invention is to enable plasma processing conditions to be switched at high speed in a plasma processing method and a plasma processing apparatus, and to shorten the time required for the entire plasma processing.

  In order to prevent a decrease in plasma density when switching the plasma processing conditions, it is effective to shorten the matching operation time of the automatic matching machine. As a method for shortening the matching time, a test discharge for obtaining the matching condition after the step switching may be performed in advance, and the initial setting of the matching machine immediately after the step switching may be changed based on the result. By using the initial setting of the matching machine corresponding to the matching conditions obtained in advance, the matching operation can be speeded up and the plasma density can be prevented from lowering.

  Further, as another method for preventing a decrease in plasma density at the time of step switching, it is possible to reduce a reflection that occurs transiently by inserting intermediate processing conditions between them, and to prevent a decrease in plasma density.

  In order to solve the above problems, the present invention provides a plasma processing chamber, a substrate electrode for placing a substrate to be processed in the plasma processing chamber, and a plasma processing gas supplied to the plasma processing chamber at a predetermined flow rate. A gas supply device for exhausting the plasma processing chamber, a high-frequency power source for generating plasma, an automatic matching machine that automatically reduces the reflected power of the high-frequency power source for generating plasma, and the gas supply In the plasma processing method of processing the substrate to be processed using a plasma processing apparatus having a mechanism for controlling the pressure of the plasma processing chamber by controlling the apparatus and the exhaust device, the substrate to be processed is formed of a multilayer film, A plasma processing method in which plasma processing conditions are switched stepwise according to each film type, and the plasma processing conditions are changed when plasma processing conditions are switched. The initial setting of the automatic matching device for automatically reducing the reflected power of the high frequency power source of use in response to the plasma impedance after switching the plasma processing conditions to control so as to reduce the reflected power.

  According to the present invention, in the plasma processing method, the reflected power is reduced in advance by obtaining an initial setting value of an automatic matching machine capable of reducing the reflected power corresponding to the plasma impedance after switching the plasma processing conditions. At the time of switching, the reflected power is reduced by setting the initial setting value of the automatic matching machine obtained in advance. Furthermore, the present invention provides the above plasma processing method, wherein the reflected power is reduced by acquiring the plasma processing conditions for automatically reducing the reflected power of the high frequency power source for generating plasma when switching the plasma processing conditions. The reflected power is reduced corresponding to the later plasma impedance.

  Further, according to the present invention, in the above plasma processing method, the stepwise switching performs step switching of the plasma processing conditions step by step, and reduces the reflected power of the plasma generating high frequency power source immediately after the plasma processing condition switching.

  In order to solve the above problems, the present invention provides a plasma processing chamber, a substrate electrode for placing a substrate to be processed in the plasma processing chamber, and a plasma processing gas supplied to the plasma processing chamber at a predetermined flow rate. A gas supply device for exhausting the plasma processing chamber, a high-frequency power source for generating plasma, an automatic matching machine that automatically reduces the reflected power of the high-frequency power source for generating plasma, and the gas supply And a mechanism for controlling the pressure of the plasma processing chamber by controlling the apparatus and the exhaust device. In the plasma processing apparatus for processing the substrate to be processed, the substrate to be processed is formed of a multilayer film, and according to each film type. A plasma processing apparatus for switching plasma processing conditions in a stepwise manner, wherein the plasma processing conditions are automatically adjusted to automatically reduce the reflected power of a high-frequency power source for generating plasma. The initial setting of the machine, comprising means for controlling the plasma processing condition switching inhibition of the reflected power of the plasma generating high-frequency power supply immediately after.

  According to the present invention, in the plasma processing apparatus, the control unit automatically reduces the reflected power of the high frequency power source for generating plasma that can suppress the reflected power of the high frequency power source for generating plasma immediately after switching the plasma processing conditions obtained in advance. The automatic setting machine has a function of setting the initial setting of the automatic matching machine to the automatic setting machine when the plasma processing conditions are switched. Further, according to the present invention, the control unit is configured to perform initial setting of an automatic matching machine that automatically reduces the reflected power of the high frequency power source for generating plasma that can suppress the reflected power of the high frequency power source for generating plasma immediately after switching the plasma processing conditions. Has a function for automatically obtaining.

  According to the present invention, in the plasma processing apparatus, the stepwise switching includes means for stepwise switching plasma processing conditions to reduce reflected power of a plasma generating high frequency power supply immediately after switching the plasma processing conditions.

  According to the present invention, plasma instability can be prevented in a plasma processing apparatus when plasma processing conditions are switched. By preventing plasma instability, it is possible to reduce foreign matter by suppressing foreign matter adhesion to the substrate to be processed, and to optimize the plasma processing characteristics with high accuracy. In addition, since the plasma processing condition can be switched at high speed, the time required for the entire plasma processing can be shortened.

  [Embodiment 1] A plasma etching apparatus will be described as a first embodiment using the present invention. FIG. 1 shows a schematic diagram of an example of a plasma etching apparatus which is a plasma processing apparatus used in this embodiment. A plasma etching apparatus, which is a plasma processing apparatus, includes a processing chamber 10, a disk-shaped antenna 11 of an antenna section, a shower plate 12, a dielectric window 13, a static magnetic field generator 14, a vacuum exhaust device 15, and a gas. Supply source 16, gas introduction path 17, substrate electrode 21, RF bias power supply 22, RF bias automatic matching machine 23, high frequency power supply 31, automatic matching machine 32, coaxial line 33, and automatic matching machine control Device 34. The automatic matching machine control device 34 has a matching parameter table 341. A substrate 50 to be processed is placed and held on the substrate electrode 21.

  When applying the plasma processing method of the present invention, which will be described later, the automatic matching machine controller 34 automatically changes the reflected power of the high frequency power in response to changes in the plasma impedance when the plasma processing conditions are changed. It is a device that controls the operation of. The matching parameter table 341 of the automatic matching machine controller 34 has matching parameters necessary for controlling the automatic matching machine 32 so as to reduce the reflected power of the high frequency power corresponding to the change in plasma impedance when the plasma processing condition is changed. It is a described table. When the plasma condition is changed, the automatic matching machine controller 34 reads the contents of the matching parameter table 341 and controls the automatic matching machine 32 so that the high-frequency reflected power is reduced.

  The high frequency power generated by the high frequency power source 31 is transmitted from the coaxial line 33 to the disk-shaped antenna 11 of the antenna unit via the automatic matching machine 32. A dielectric window 13 and a shower plate 12 are provided on the processing chamber 10 side of the disk-shaped antenna 11, and high frequency power is input to the processing chamber 10 through these. There is a static magnetic field generator 14 around the processing chamber 10, and a static magnetic field can be applied to the processing chamber 10. An electron cyclotron resonance phenomenon is known as an interaction between an electromagnetic wave and an electron in a static magnetic field. Plasma processing conditions such as high-frequency power is efficiently absorbed by electrons due to the electron cyclotron resonance phenomenon, making it easy to generate plasma and enabling plasma processing even in low-pressure and low-power areas where plasma generation is generally difficult There is an advantage that can be taken widely. By changing the distribution of the static magnetic field, plasma diffusion can be controlled and plasma loss can be reduced. Therefore, in this plasma processing apparatus, the uniformity of plasma processing can be improved. A multistage electromagnet was used as the static magnetic field generator 14. The distribution of the static magnetic field can be controlled by changing the current supplied to each electromagnet.

  A substrate electrode 21 for holding the substrate to be processed 50 is provided in the processing chamber 10. The substrate electrode 21 is provided with an RF bias power source 22 via an RF bias automatic matching machine 23, and a bias potential can be applied to the substrate 50 to be processed.

  Connected to the processing chamber 10 is an evacuation system provided with an evacuation device 15 and a processing gas supply system provided with a gas supply source 16 and a gas introduction path 17 to supply a predetermined gas into the processing chamber at a predetermined flow rate. , It can be maintained at a pressure suitable for processing. The shower plate 12 is provided with a large number of fine gas supply holes, and the processing gas from the gas supply source 16 can be supplied into the processing chamber in a shower shape.

  A control apparatus (not shown) is connected to the plasma etching apparatus shown in FIG. 1, and can monitor and control high-frequency power, gas flow rate, RF bias power, processing chamber pressure, and the like. The control device can also monitor the matching parameters of the automatic matching machine and the RF bias automatic matching machine. Switching of plasma processing conditions, which will be described later, can be automatically performed by the control device and the automatic matching machine control device 34 according to a procedure predetermined by the user. The procedure previously determined by the user is called a recipe.

  In general, in a plasma etching apparatus, plasma processing conditions are often switched during an etching process. For example, at the initial stage of the etching process, the processing conditions for removing the material to be etched are used at high speed. In many cases, the aim is to prevent scratching of the groundwork. When the material to be etched is a multilayer film, the etching process may be performed by applying plasma processing conditions optimized for each film.

  If foreign matter adheres to the substrate to be processed 50, the quality of the plasma processing is deteriorated. For example, in the case of the plasma etching process, there arises a problem that the foreign matter obstructs the etching of the part covering the surface of the substrate to be processed. It is known that foreign matters are charged during plasma discharge and trapped in the plasma (in the plasma sheath) and hardly fall on the substrate to be processed. For this reason, it is desirable from the viewpoint of foreign matter reduction to maintain the plasma even when the above-described plasma processing conditions are switched.

  When the plasma processing conditions are changed, characteristics such as plasma density change, and the plasma impedance changes correspondingly. The automatic matching machine operates so as to suppress the reflected wave of the high frequency power in accordance with the plasma impedance. However, the operation of the automatic matching machine is often performed by driving a mechanical element. Since the matching operation is slow, it may not be able to follow the change in plasma processing conditions. For this reason, when the plasma processing conditions are changed, a reflected wave is generated and the plasma absorbed power is lowered, so that the plasma density is lowered and it may be difficult to maintain the plasma.

  In response to the above problem, the reflected wave can be suppressed when the plasma processing conditions are changed by the procedure shown in FIG. After first determining the plasma processing conditions before and after switching (procedure 1), test discharge is performed under the conditions after switching the plasma processing conditions, and the set value of the automatic matching machine in a state where the reflected wave is suppressed is recorded ( Procedure 2). Next, when the plasma processing condition is switched, simultaneously with the switching, the setting value of the automatic matching machine is switched to the setting value recorded in advance (procedure 3).

  According to this procedure, the matching condition obtained in advance can be used at the same time as the switching, and the time required for the matching condition search and the time that the plasma is in an unstable state due to the increase of the reflected wave can be shortened. it can. Thereby, generation | occurrence | production of a high frequency reflected wave can be suppressed to the shortest, and maintenance of plasma becomes easy. Switching of the plasma processing conditions can be automatically performed according to a procedure predetermined by a user by a control device connected to the plasma processing apparatus. Moreover, the part regarding a test discharge can be automated among the procedures shown in FIG. That is, after determining the plasma processing conditions before and after the switching in the procedure 1, the determination of an appropriate matching element position initial setting value in the procedure 2 and the work of reflecting the matching element initial setting position in the recipe in the procedure 3 are collectively automated. be able to.

  In this embodiment, the case where the plasma processing conditions are switched once has been described as an example. However, when switching is performed a plurality of times, the same procedure may be repeated for each switching. As described above, the embodiment using the high frequency power source for generating the plasma has been described. However, the present invention also applies to the case where a microwave plasma source, a parallel plate type plasma source, an inductively coupled plasma source, or the like is used as another plasma source. Are equally applicable.

  [Embodiment 2] A plasma etching apparatus will be described as a second embodiment using the present invention. In the second embodiment, the description of the parts common to the first embodiment is omitted. In the second embodiment, a plasma processing condition (condition C) for preventing plasma instability during switching is inserted between the plasma processing condition before switching (condition A) and the processing condition after switching (condition B). To do. The condition C may be a single condition or a combination of a plurality of conditions in time.

  Plasma disappearance can be prevented by plasma processing conditions (condition C) for preventing plasma instability during switching. By switching the plasma processing conditions in stages over a plurality of times, the change in load impedance at each stage is reduced, and the intensity of the reflected wave generated at each stage can be reduced. It is desirable to control the division of the reflected power so that the magnitude of the reflected power becomes equal at each stage during step switching.

  FIG. 5 and FIG. 6 are schematic diagrams showing the above-described splitting of input power, and the conditions are the same before and after step switching. FIG. 5 shows a large change in impedance caused by a large change at a time as described above. The input power is reduced by suppressing the reflection of power by the operation of the automatic matching machine 32 after the step switching operation. Shows recovery. In this example, the effective input power at the time of step switching falls below the limit necessary to maintain the plasma, and the plasma disappears.

  On the other hand, in FIG. 6, step switching is divided into a plurality of steps, and the reflection of power is divided into a plurality of times. The change in load impedance at each stage is small, the decrease in input power is not less than the minimum necessary for maintaining the plasma, and the plasma does not disappear.

  The operation of the automatic matching machine during step switching described above is stepwise and may be continuous, and the continuous step switching operation is an infinite increase in the number of reflected power divisions. Is equivalent.

  That is, in the example shown in FIGS. 2 and 3, the current of the coil (not shown) is changed stepwise (instantaneously) at the time of step switching. However, in the continuous step switching operation, the coil current is gradually changed. (For example, it may be changed linearly with time). In FIG. 7, the coil current is gradually changed over a number of steps. However, this can be changed to a continuous step by, for example, performing a control that equalizes a straight line.

  As described above, in the step switching from the condition A to the condition B, the reflected power increases due to the change in the plasma impedance, and the accompanying power becomes less than the minimum necessary for maintaining the plasma, causing a plasma misfire. There is a case. However, there are cases where it is possible to maintain the plasma in step switching from condition A to condition C and from condition C to condition B. By searching in advance for a condition C such as a setting value of the matching element that does not cause such a plasma misfire, high-frequency power, and magnetic field strength, and specifying that the condition C be passed during step switching, that is, step switching. It is possible to perform step switching while maintaining the plasma by specifying the point to be passed through the path and performing stepwise step switching.

  There may be a plurality of points to be passed through the step switching path.

  The above-described points that should be passed through the step switching path may be independently controlled with respect to the above-described high-frequency power, magnetic field strength, and the like. That is, a route that changes only the high-frequency power as the first passing point and changes only the magnetic field strength as the second passing point may be designated.

  FIG. 7 is an experimental result showing the second embodiment of the present invention, and shows the operation of the plasma processing apparatus when the static magnetic field is changed in 10 steps every 2 seconds. The change in impedance at each stage is small, and the matching machine completes the matching operation during the discharge time of 2 seconds, and the reflected wave can be made almost “0”. You can see that it is maintained.

  [Embodiment 3] A third embodiment of the present invention will be described with reference to FIGS. The third embodiment is an improvement of the setting method of the condition C used in the second embodiment, and the description of the parts common to the second embodiment is omitted.

  An example of an intermediate condition C setting method is shown below. In general, when the plasma processing condition is switched from the condition A to the condition B, the impedance of the plasma changes, and the automatic matching machine cannot follow the impedance change, so that a reflected wave is generated. As described above, when the reflected wave becomes large and falls below the power necessary for plasma maintenance, there is a problem in switching the conditions such as plasma disappearing. By inserting the condition C that does not cause the disappearance of the plasma between the condition A and the condition B, it is possible to avoid such a problem. A method for setting the condition C will be described below.

  It is assumed that the time required for step switching is sufficiently shorter than the time required for alignment of the automatic aligner, and each step is maintained sufficiently longer than the time required for alignment of the automatic aligner. That is, immediately before the step switching, the automatic matching machine sufficiently suppresses the reflected wave, and immediately after the switching, the automatic matching machine maintains the state immediately before the switching. The impedance of the load is switched faster than the matching operation of the automatic matching machine, and impedance mismatch occurs immediately after switching. In this case, according to the formulation described in [Means for Solving the Problems], it is possible to calculate the magnitude or the like of the reflected wave generated at the step switching using the impedance of the load. Alternatively, the magnitude of the reflected wave may be measured experimentally.

FIG. 8 shows an example in which the automatic matching machine and the load are modeled. The automatic matching machine was modeled as shown in FIG. 8 using a π-type circuit, and the load of the processing chamber including the plasma was R _p + jX _p . However, j is an imaginary unit. Further, let Z _{0 be} the characteristic impedance of the line connecting the automatic matching machine and the processing chamber.

The impedance when the load side is viewed from the input port of the automatic matching machine is Z ₀ which is the same as the characteristic impedance since matching is obtained immediately before the step switching. Assuming that the impedance Z ₀ ′ seen from the input port of the automatic matching machine immediately after the step switching maintains the same state as that immediately before the switching and the load impedance changes to R _p ′ + jX _p ′, FIG. The following equation (6) is used.

However, in the above equation (6), Rpp ′ + jXpp ′ is the following equation (7).

At this time, the reflection coefficient Γ at the input port of the automatic matching machine is expressed by the following equation (8), and the magnitude of the reflected wave can be calculated.

  That is, using the load impedance data, it is possible to calculate the magnitude of the reflected wave that occurs when the step is switched between arbitrary conditions.

  FIG. 9 shows the result of comparison between the experimental value and the calculated value of the reflection coefficient. In the experiment, step switching was performed from a certain processing condition, and the reflection coefficient immediately after the step switching was measured. Only the static magnetic field was changed as step switching. The impedance of the load used for the calculation was measured and used in a state where matching was achieved after step switching. As shown in FIG. 9, the measurement points are arranged in a substantially straight line, the experimental value and the calculated value show a high correlation, and it has been confirmed that the reflection immediately after the step switching can be evaluated by calculation.

  In the above example, the model called π type shown in FIG. 8 is used as the circuit model of the automatic matching machine, but other models (for example, T type, Γ type, etc.) may be used for modeling.

  An example of a method for obtaining a condition C for suppressing plasma instability during step switching by inserting an intermediate condition when step switching from a certain condition A to a condition B will be described with reference to FIG. The plasma processing conditions include, for example, several parameters such as processing pressure and high frequency power. For the sake of simplicity, description will be made by taking as an example a case where the conditions are composed of two parameters of plasma processing parameter 1 and plasma processing parameter 2. Since there are two parameters, condition A, condition B, and the like can be displayed as planar points shown in FIG.

  When the reflected power is constant when step switching is performed from the condition A to the arbitrary condition D, the condition D can draw a certain trajectory and can be expressed as a line in a planar shape. Similarly, when step switching is performed from an arbitrary condition D ′ to a condition B, a locus where the reflected power is constant can be drawn as a line in a planar shape. When the reflected power at the time of step switching from the condition A to the condition D is small, the distance between the condition D and the condition A is close, but when the reflected power at the time of switching is large, the distance between the condition D and the condition A is separated. The locus of the condition D draws a contour line on the plane according to the reflected power at the time of step switching. Similarly, the locus of the condition D ′ also draws another contour line corresponding to the reflected power. Considering the case where the reflected power generated at the step switching from the condition A to the condition D and the reflected power generated at the step switching from the condition D ′ to the condition B are equal, the locus of the condition D and the locus of the condition D ′ intersect or touch each other. When there is a point, the point where the reflected wave generated at the time of step switching between the two becomes the minimum value is used as the condition C. When step switching is performed from condition A to condition C and further to condition B, the reflected wave generated at each switching is minimized.

  The calculation of the reflected power may use calculation based on load impedance or may be obtained experimentally. In the above description, the case where there are two parameters for determining the plasma processing condition has been described as an example. However, the condition C can be obtained in the same procedure even when the number of parameters is increased.

  The case where one condition C is inserted in the case of performing step switching from condition A to condition B has been described above, but the same applies to step switching between condition A and condition C, and step switching between condition C and condition B. If the procedure is applied, the steps can be further subdivided. If the plasma instability at the time of step switching cannot be suppressed only by inserting one condition C, the steps may be further divided. By repeating such a procedure, the steps can be divided virtually arbitrarily. By finely dividing the step switching step, the reflected wave at the step switching can be suppressed and the step switching can be performed more smoothly.

  [Embodiment 4] A fourth embodiment of the present invention will be described with reference to FIG. In the fourth embodiment, the setting method of the condition C used in the third embodiment is improved, and the description of the parts common to the third embodiment is omitted.

One method for calculating a condition to be inserted when step switching is performed stepwise has been described in the third embodiment. An example of another method will be described below with reference to FIG. A vector in which numerical values (for example, pressure, high-frequency power, etc.) of plasma processing conditions are arranged is defined and referred to as a condition vector. A condition vector corresponding to condition A is indicated by Av (indicated by → on A in the following expression), and a condition vector corresponding to condition B is indicated by Bv (indicated by → on B in the expression). ). The following vectors (9) and (10) are defined using the condition vectors Av and Bv.

When t = 0 and t = 1, the above equation (10) becomes the following equations (11) and (12), and the parameter t is set to a value between 0 and 1, so that the condition vector xv (t) An intermediate condition between the condition A and the condition B can be expressed by (in the following formula, x is added to x (t)).

  A transient reflected wave is generated by switching the step once. A lower limit of power consumed by the plasma (Pcmin) is determined and inserted between the condition A and the condition B according to the following procedure. Decide. However, Pcmin is set to a size that does not cause plasma instability when switching steps. For the calculation of the reflected power, the calculation based on the load impedance described above may be used, or may be obtained experimentally.

(1) in the t = 0 Step of _{t 1} switching, power consumed seeks _t 1> 0 becomes _{t 1} becomes PCMin.

(2) Similarly, in the switching step _{t 2} from t = _{t 1,} obtaining the _t 2> _{t 1} becomes _{t 2} power consumed becomes PCMin.

(3) The above steps (1) and (2) are repeated and the procedure is continued until just before t _i (i = 1, 2, 3,...) Exceeds 1.

(4) A condition xv (ti) (i = 1, 2, 3,...) Corresponding to each t _i (i = 1, 2, 3,...) Is inserted between the condition A and the condition B, respectively.

  In step switching performed in a stepwise manner between the condition A and the condition B, the consumed electric power is maintained at Pcmin or higher, so that plasma instability associated with the step switching does not occur.

  [Embodiment 5] A fifth embodiment of the present invention will be described. The fifth embodiment is substantially the same as the first embodiment except that the operation of the automatic matching machine at the time of step switching is different, and the description of the common parts is omitted.

  In the second embodiment to the fourth embodiment, it has been described that the switching speed of the plasma processing parameter at the time of step switching is sufficiently high with respect to the matching speed of the automatic matching machine. However, the plasma processing parameter is adjusted according to the matching speed of the automatic matching machine. The switching speed may be reduced. By reducing the parameter switching speed, the time change of the load impedance can be suppressed to a speed that the automatic matching machine can follow. Can be suppressed. Suppression of plasma instability due to a decrease in the switching speed of plasma processing parameters may be used alone or in combination with the method of adding intermediate steps described above.

  [Embodiment 6] A sixth embodiment of the present invention will be described. The sixth embodiment is similar to the third embodiment, and a description of parts common to the third embodiment is omitted. When the plasma processing condition is finally switched from the condition A to the condition B, step switching is smoothly performed by inserting a predetermined condition between the condition A and the condition B. A reflected wave is generated between each step due to an impedance change, and plasma instability associated with this is prevented. In this embodiment, first, a lower limit value (Pcmin) of plasma power consumption that can be allowed at each step switching is set. However, Pcmin is set to a size that does not cause plasma instability during step switching. Hereinafter, the route from the condition A to the condition B is searched in the following procedure.

(1) in the parameter space to determine the area that can be reached by switching one step from the condition A (the Omega _1).

(2) determining whether either of the conditions B in the region Omega _1, the process proceeds to if it contains (4). If not included, a region (referred to as Ω ₂ ) that can be reached from the region Ω _{1 by one} more step switching is obtained.

(3) The above condition (2) is repeated until the condition B is included, and it is assumed that the condition B is included for the first time in an area (Ω _{N where} N is a natural number) that can be reached by N step switching.

(4) Condition B is contained in the region Omega _N, the switching N single step, but can be reached from the condition A, the path is not one, to search for the optimum route. A region (referred to as Ω _N ′) in which there is a path that can reach condition B by N step switching from condition A is included in region Ω _N. Search within Ω _N ′ to find the optimum route.

  The criteria for searching for the optimum route in (4) above are as follows.

(1) A path that requires the least amount of operation of the automatic matching machine In the case of an automatic matching machine of a type in which the matching element is mechanically operated, evaluation is performed based on the moving distance of the matching element or a value correlated with the moving distance. When a plurality of matching elements are used, the evaluation is performed using the moving distance of each matching element or the sum of values correlated with the moving distance, or the sum of squares, maximum value, and norm. Short movement distance also leads to short operation time of the automatic aligner.

(2) Path that avoids difficult matching area of automatic matching machine Although it is desirable that the automatic matching machine can cope with any load impedance, there are areas where matching is difficult due to the breakdown voltage and the like. In order to prevent the set route from passing through a region that is difficult to match, a search is performed by excluding the region that is difficult to match from the region Ω _N ′.

  In each of the above embodiments, an etching apparatus using magnetic field high frequency discharge has been described as an example. However, other discharges (capacitively coupled discharge, inductively coupled discharge, magnetron discharge, surface wave excited discharge, transfer coupled discharge) can be used. The same effect can be obtained in the dry etching apparatus used. In each of the above embodiments, the etching apparatus has been described. However, other plasma processing apparatuses that perform plasma processing, such as a plasma CVD apparatus, an ashing apparatus, and a surface modification apparatus, have similar operational effects.

  The method shown in Example 1 may be used in combination with the methods shown in Examples 2 to 6, and has the same effect.

Schematic explaining an example of the structure of the etching apparatus using this invention. The figure explaining the time dependence of the high frequency electric power before and after switching of desirable plasma processing conditions, a matching element position, etc. The figure explaining the time dependence of the high frequency electric power before and after the conventional plasma processing condition switching, a matching element position, etc. The figure explaining the procedure for speeding up operation | movement of the automatic matching machine at the time of the plasma processing condition switch which concerns on this invention. The figure explaining the change of the input electric power before and after the conventional step change. The figure explaining the change of the input electric power before and after step switching which concerns on this invention. The figure explaining transition of high frequency electric power etc. at the time of performing step change concerning the present invention in steps. The circuit diagram which shows the circuit model of an automatic matching machine and load. The graph which shows the correlation of the calculated value of a reflection coefficient, and an experimental value. The figure explaining the setting method of the step inserted for stabilization at the time of step switching of this invention. The figure explaining the setting method of the step inserted for stabilization at the time of step switching of this invention.

Explanation of symbols

10: Processing chamber 11: Disc antenna 12: Shower plate 13: Dielectric window 14: Static magnetic field generator 15: Vacuum exhaust device 16: Gas supply device 17: Gas introduction path 21: Substrate electrode 22: RF bias power supply 23 : RF bias automatic matching machine 31: High frequency power supply 32: High frequency automatic matching machine 33: Coaxial line 34: Automatic matching machine controller 341: Matching parameter table 50: Substrate to be processed

Claims (8)

A plasma processing chamber, a substrate electrode for placing a substrate to be processed in the plasma processing chamber, a gas supply device for supplying a plasma processing gas to the plasma processing chamber at a predetermined flow rate, and the plasma processing chamber. An exhaust device for exhausting, a high-frequency power source for generating plasma, an automatic matching machine that automatically reduces reflected power of the high-frequency power source for generating plasma, and controlling the gas supply device and the exhaust device to control the plasma processing In the plasma processing method of processing the substrate to be processed using a plasma processing apparatus having a mechanism for controlling the pressure of the chamber,
The substrate to be processed is a multilayer film, and a plasma processing method for switching plasma processing conditions step by step according to each film type,
The initial setting of the automatic matching machine that automatically reduces the reflected power of the high frequency power source for generating plasma when the plasma processing condition is switched is reduced to correspond to the plasma impedance after switching the plasma processing condition. The plasma processing method characterized by controlling as follows. The plasma processing method according to claim 1,
The reflected power is reduced by obtaining an initial setting value of an automatic matching machine that can reduce the reflected power corresponding to the plasma impedance after the plasma processing condition is switched in advance. The plasma processing method is characterized in that the reflected power is reduced by setting the initial set value. The plasma processing method according to claim 1,
The reflected power is reduced by acquiring plasma processing conditions that automatically reduce the reflected power of the high-frequency power source for plasma generation when switching the plasma processing conditions, and reducing the reflected power corresponding to the plasma impedance after switching the plasma processing conditions. And a plasma processing method. The plasma processing method according to claim 1,
In the plasma processing method, the stepwise switching is performed by stepwise switching of plasma processing conditions to reduce the reflected power of the high-frequency power source for plasma generation immediately after switching of the plasma processing conditions. A plasma processing chamber, a substrate electrode for placing a substrate to be processed in the plasma processing chamber, a gas supply device for supplying a plasma processing gas to the plasma processing chamber at a predetermined flow rate, and the plasma processing chamber. An exhaust device for exhausting, a high-frequency power source for generating plasma, an automatic matching machine that automatically reduces reflected power of the high-frequency power source for generating plasma, and controlling the gas supply device and the exhaust device to control the plasma processing A plasma processing apparatus for processing the substrate to be processed, comprising a mechanism for controlling the pressure in the chamber,
The substrate to be processed is composed of a multilayer film, and is a plasma processing apparatus that switches plasma processing conditions step by step according to each film type,
Means for controlling the suppression of the reflected power of the high frequency power source for plasma generation immediately after switching the plasma processing conditions by the initial setting of the automatic matching machine that automatically reduces the reflected power of the high frequency power source for generating plasma. A plasma processing apparatus comprising: The plasma processing apparatus according to claim 5, wherein
The control means performs plasma processing on an initial setting of an automatic matching machine that automatically reduces the reflected power of the high frequency power source for generating plasma that can suppress the reflected power of the high frequency power source for generating plasma immediately after switching the plasma processing conditions obtained in advance. A plasma processing apparatus having a function of setting in an automatic setting machine when conditions are switched. The plasma processing apparatus according to claim 5, wherein
The control means is a function that automatically obtains an initial setting of an automatic matching machine that automatically reduces the reflected power of the plasma generating high-frequency power source that can suppress the reflected power of the plasma generating high-frequency power source immediately after switching the plasma processing conditions. A plasma processing apparatus comprising: The plasma processing apparatus according to claim 5, wherein
The stepwise switching includes means for stepwise switching plasma processing conditions to reduce reflected power of a plasma generating high-frequency power source immediately after switching the plasma processing conditions.

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