JP5703038B2 - Plasma processing equipment - Google Patents

Description

  The present invention relates to a plasma processing apparatus for processing a substrate-like sample such as a semiconductor wafer placed on a sample stage disposed in a processing chamber inside a vacuum vessel, using plasma formed in the processing chamber. The present invention relates to a plasma processing apparatus that includes a refrigerant flow path that circulates in a refrigeration cycle and processes a sample while adjusting the temperature of a sample stage.

  Conventionally, in a semiconductor device manufacturing process, plasma processing is performed on a sample such as a semiconductor wafer by a plasma etching apparatus, a plasma CVD apparatus, or the like. In these plasma treatments, the temperature of the sample strongly affects the treatment results. Specifically, the plasma etching process affects the size and shape of the processed pattern formed on the sample surface by etching, and the plasma CVD process affects the quality and deposition rate of the film formed on the sample surface. Affect. Therefore, it is very important to manage the sample temperature in order to improve the quality of the treatment applied to the surface of the sample substrate in these plasma treatments.

  In such plasma processing, in order to control the temperature of the sample, a technique of adjusting the temperature of the sample table and the sample holding surface by means of temperature adjusting means arranged inside the sample table holding the sample is adopted. I came. For example, a coolant channel is formed inside the sample stage, and a liquid coolant is allowed to flow into the channel to exchange heat by heat transfer between the coolant and the channel wall surface in contact with the coolant. An apparatus system that adjusts the temperature and adjusts the sample to a desired temperature is used. In such a case, a refrigerant temperature adjusting unit (for example, a chiller unit) is connected to the sample stage through a pipe, and the refrigerant adjusted to a predetermined temperature by the cooling device or the heating device in the refrigerant temperature adjusting unit is supplied to the sample stage. After being supplied into the internal flow path and exchanging heat, it is returned to the refrigerant temperature adjusting unit again.

  Such a refrigerant temperature adjusting unit is configured to temporarily store the liquid refrigerant in a tank for storing the liquid refrigerant and supply the refrigerant to the sample stage after adjusting the temperature. In this configuration, since a large amount of refrigerant is used for temperature adjustment, the heat capacity of the refrigerant increases, and as a result, it is advantageous for keeping the sample temperature constant even if the heat input to the sample and the sample stage changes. . On the other hand, however, when the temperature of the sample and the sample stage is positively and rapidly changed, there is a problem that the rate of temperature change cannot be increased due to the large heat capacity of the refrigerant. In addition, the heat exchange between the liquid refrigerant and the flow path is only heat transfer, and the amount of heat transfer is small, which is the cause of the rapid change in temperature of the sample stage and the sample.

  On the other hand, in the manufacture of semiconductor devices, as the diameter of a semiconductor wafer, which is a sample in plasma processing as described above, increases, the power applied to the sample during processing tends to increase. The amount of heat input to is getting bigger than before. For this reason, there is a need for a technique for stably adjusting the temperature of a semiconductor substrate at high speed and with high accuracy even with such large heat input. Furthermore, it is desired to adjust the temperature of the sample quickly and appropriately in accordance with each processing step for processing each of the plurality of films due to the complicated semiconductor device structure and the multilayered film on the surface of the semiconductor substrate.

  Further, in the conventional refrigerant temperature control unit, the liquid refrigerant flows through the flow path inside the sample stage and transfers heat between the wall of the flow path and the liquid refrigerant. It will gradually rise from the entrance to the exit. Since the temperature of the sample table surface is affected by the temperature of the refrigerant flowing through the flow path, such a temperature change of the refrigerant may lead to deterioration of the in-plane temperature distribution on the sample table surface. As a result, the in-plane temperature distribution of the sample is deteriorated, which may cause deterioration of the in-plane distribution of the plasma treatment.

  In response to such a problem, a path through which the refrigerant for cooling the sample stage circulates is configured as a refrigeration cycle including a compressor, a condenser, an expansion valve, and an evaporator, and the refrigerant is provided in the refrigerant flow path in the sample stage. A technique has been proposed in which the temperature of the sample stage is adjusted by a so-called direct expansion type refrigerant temperature adjusting unit, in which the sample stage is cooled by boiling and evaporating the sample stage, that is, the sample stage acts as an evaporator of the refrigeration cycle. As examples of such a technique, those disclosed in JP-A-6-346256 (Patent Document 1) and JP-A-2005-83864 (Patent Document 2) are known.

  In these prior arts, for example, an alternative chlorofluorocarbon R410a (hydrofluorocarbon) is used as a refrigerant, introduced into a refrigerant flow path inside the sample stage, and a refrigeration cycle is configured to operate the sample stage as an evaporator. Is used for heat exchange between the refrigerant and the flow path wall surface, and a technique for adjusting the temperature corresponding to a large amount of heat input to the sample and the sample stage is disclosed. Also, the temperature of the refrigerant can be changed quickly by adjusting the opening of the expansion valve to quickly adjust the pressure of the refrigerant in the flow path. As a result, the temperature of the sample stage and the sample can be changed as desired. In order to improve the accuracy and reproducibility of sample processing, a method has been disclosed.

JP-A-6-346256 JP 2005-89864 A

  In the temperature control mechanism of the sample table using the direct expansion type refrigerant temperature control unit disclosed in Patent Document 1 and Patent Document 2, even when the sample table has heat input from plasma, When the gas-liquid mixed phase flow is present, the refrigerant temperature is constant. On the other hand, when the liquid portion of the refrigerant completely evaporates and becomes a state called dryout in which only the gas is obtained, the temperature of the refrigerant rises.

  Therefore, it entered from the refrigerant inlet of the sample stage, circulated through the flow path inside the sample stage, and on the way out from the outlet, the dryness gradually increased due to heat input from the plasma and became dry out inside the sample stage. In this case, the temperature of the refrigerant is higher on the downstream side than the point where the dryout occurs, and as a result, the temperature distribution on the sample stage is not uniform or cannot be expected. The reproducibility and accuracy of the process will be impaired. In order to prevent this, it is necessary to detect and detect the dry-out of the refrigerant or an indication of its occurrence, but such a problem has not been taken into account in the prior art.

  In addition, the direct expansion type refrigerant temperature control unit disclosed in Patent Document 1 and Patent Document 2 is configured such that the temperature of the circulating refrigerant pressure is adjusted outside the sample stage because the inside of the sample stage constitutes a refrigeration cycle. The refrigerant is supplied with a higher pressure than when the sample stage is not used as part of the refrigeration cycle. For example, in the configuration in which the liquid refrigerant is circulated by the above-described chiller unit, the refrigerant is at a pressure of about 0.4 to 0.8 MPa (4 to 8 atm), whereas disclosed in Patent Document 1 and Patent Document 2. In the technology, for example, when the substitute Freon R410a is used, the refrigerant reaches a high pressure of about 2.0 to 4.0 MPa (20 to 40 atmospheres).

  Note that a sample stage on which a sample is placed is generally manufactured by joining a metal disk that forms a coolant channel and another metal disk by cutting the surface into a groove shape. Therefore, the force applied to the refrigerant flow path by the pressure of the refrigerant acts to peel off these two metal disks. Therefore, when the refrigerant has a pressure of about 0.4 to 0.8 MPa, the bonding strength can be easily secured, whereas when the refrigerant has a high pressure of about 2.0 to 4.0 MPa, the bonding There is a problem that there is a high risk that the part will peel off and lead to breakage of the sample stage. In addition, as described above, the refrigerant inside the sample table flows while boiling, but the sample table vibrates with the boiling, so that the joint between the two metal disks constituting the sample table is peeled off. The risk increases.

  Since plasma processing is generally performed inside a processing chamber that has been depressurized to about several Pa, the joint at the outer periphery of the sample stage located inside the processing chamber peels off, and refrigerant leaks outside the sample stage. In this case, the pressure in the processing chamber rises due to the vaporization of the refrigerant, which hinders plasma processing. When the refrigerant is an alternative chlorofluorocarbon, since it is a compound of hydrogen, fluorine, and carbon, these components diffuse into the plasma, which hinders plasma processing. In addition, when the joint part of the outer periphery of the sample stage is effectively joined, and even if there is no leakage of the refrigerant to the outside of the sample stage, the joint part of the inner periphery is peeled off and the refrigerant flow path is short-circuited In this case, a refrigerant flow occurs in a region other than the provided flow path. Since the flow path inside the sample stage is strictly designed, the temperature distribution of the sample stage changes to an unintended one by disturbing the flow of the refrigerant, and as a result, the plasma applied to the sample surface The distribution within the processing plane will change.

  As described above, the prior art takes into account the problem of detecting the dry-out detection means of the refrigerant when flowing through the flow path inside the sample stage, the peeling of the joint of the sample stage, and the breakage of the sample stage. There wasn't. For this reason, it has not been considered about the problem that the accuracy, reproducibility and reliability of the processing by the plasma processing apparatus are impaired.

  An object of the present invention is to provide a plasma processing apparatus with improved processing accuracy or reliability.

The object is to provide a processing chamber in which plasma is formed inside a vacuum vessel, and a sample stage which is arranged below the processing chamber and on which a sample is placed, in which a refrigerant for a refrigeration cycle is placed. A sample stage having a cylindrical shape that operates as an evaporator through which the gas flows, a flow path of the refrigerant disposed concentrically with respect to the center of the cylinder disposed inside the sample stage, and disposed below the sample stage And at least one detector connected to a location in the vicinity of the inlet of the refrigerant into the sample table to detect vibration of the sample table, and the flow from the output from the detector to the inside of the flow path. This is achieved by a plasma processing apparatus that includes a compressor or an adjustment unit that adjusts the operation of an expansion valve that constitutes the refrigeration cycle based on the result of detecting the dryness of the refrigerant.

  Further, the sample table disposed between the compressor and the sample table on the refrigeration cycle based on a result of detecting the dryness of the refrigerant flowing inside the flow path from the output from the detector. This is achieved by a plasma processing apparatus including an adjustment unit that adjusts the temperature of the refrigerant flowing into the chamber.

  Furthermore, this is achieved by arranging the detector connected to a location near the outlet of the refrigerant arranged on the lower surface of the sample stage.

  Furthermore, among the arc-shaped channels, a plurality of arc-shaped channels in which the refrigerant channels are arranged concentrically at different radial distances from the center inside the sample stage. This is achieved by arranging the detector on the lower surface of the sample stage and in the vicinity of the connection path.

  Furthermore, this is achieved by having a planar shape of the connecting path having a curvature smaller than the curvature of the arcuate channel.

  Furthermore, the flow path of the sample stage is configured by joining two members on the upper and lower sides, and from the detector arranged in a position connected to the vicinity of the connection path on the lower surface of the sample stage. This is achieved by detecting a deficiency in joining of the upper and lower members from the output.

  Furthermore, this is achieved by having an electrically insulating member disposed in contact with the lower surface of the sample stage, and disposing the detector in contact with the insulating member.

It is a longitudinal cross-sectional view which shows the outline of a structure of the plasma processing apparatus which concerns on the Example of this invention. It is the horizontal and longitudinal cross-sectional view which expands and shows the structure of the sample stand of the Example shown in FIG. It is a graph which shows the output which each vibration sensor arrange | positioned at the sample stand of 1st Example shown in FIG. 1 detected in time series. It is a horizontal and longitudinal cross-sectional view which shows the outline of a structure of the sample stand which concerns on the modification of the Example shown in FIG. It is a horizontal and longitudinal cross-sectional view which shows the outline of a structure of the sample stand which concerns on another modification of the Example shown in FIG. It is a horizontal and longitudinal cross-sectional view which shows the outline of a structure of the sample stand which concerns on another modification of the Example shown in FIG. It is a graph which shows the output which the pressure gauge detected in the modification shown in FIG. 6 in time series.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  Embodiments of the present invention will be described below with reference to FIGS.

  FIG. 1 is a longitudinal sectional view schematically showing the configuration of a plasma processing apparatus according to an embodiment of the present invention. In particular, the present embodiment is a configuration of a plasma processing apparatus that forms ECR plasma using an electric field and a magnetic field by microwaves and etches a substrate-like sample such as a semiconductor wafer disposed in a processing chamber inside a vacuum vessel. Is shown.

  In this embodiment, a processing chamber lid 2 made of disc-shaped quartz that forms a vacuum vessel on a cylindrical processing chamber wall 1 that also forms the upper portion of the vacuum vessel and hermetically seals the inside and outside. A processing chamber 3 is configured which is arranged and thereby decompressed inside. A sample stage 4 having a cylindrical shape is provided below the inside of the processing chamber 3, and a sample 5 (in this embodiment, a semiconductor wafer) is held on the upper mounting surface.

  An opening of a gas introduction pipe 6 is provided in the upper part of the processing chamber 3, and a processing gas 7 that is a highly reactive gas for performing an etching process is introduced into the processing chamber 3 from the opening. An exhaust port 8 is provided in the lower part of the processing chamber 3 to exhaust the processing gas 7 introduced into the processing chamber 3 and the particles of the reaction product generated by plasma and etching. A pressure adjusting valve 9 and a turbo molecular pump 12 which is a kind of vacuum pump are provided at the tip of the exhaust port 8, and the pressure of the processing chamber 3 is adjusted to about several Pa by adjusting the opening degree of the pressure adjusting valve 9. Is done.

  The microwave 10 is applied via the processing chamber lid 2 at the upper part of the processing chamber 3, and the processing chamber 3 is interacted with a magnetic field generated by a solenoid coil (not shown) arranged around the processing chamber wall 1. Plasma 11 is generated inside. A plasma etching process is performed by exposing the sample 5 to the plasma 11.

  In this embodiment, a coolant channel 20 is provided inside the sample stage 4 in order to control the temperature of the sample 5 which is a circular semiconductor wafer. A refrigerant temperature adjusting unit 21 using a direct expansion refrigeration cycle is connected to the refrigerant flow path 20, and alternative chlorofluorocarbon is flowed to the flow path 20 as a refrigerant.

  The refrigerant temperature adjustment unit 21 includes a compressor 22, a condenser 23, an expansion valve 24-1, an expansion valve 24-2, and an evaporator 26. The refrigerant discharged from the sample stage 4 is introduced into the evaporator 26 via the expansion valve 24-2 whose opening degree is adjusted, and is vaporized until the dryness becomes almost zero. Thereafter, the refrigerant is introduced into the compressor 22 where it is compressed and introduced into the condenser 23.

  Cooling water 25 is introduced into the condenser 23, whereby the refrigerant introduced into the condenser 23 is cooled and condensed as a result. The condensed refrigerant is introduced into the expansion valve 24-1 whose opening degree is adjusted, and after being adjusted to a desired pressure by the opening degree, the refrigerant is introduced into the refrigerant flow path 20 and circulates while boiling and vaporizing.

  The sample stage 4 is controlled to a desired temperature by the configuration of the refrigeration cycle. In addition, since the refrigerant introduced into the sample stage 4 boils and regulates the temperature of the sample stage 4, the sample stage 4 functions as a first evaporator, and the evaporator 26 inside the refrigerant temperature adjusting unit 21 is so-called. Will function as a second evaporator.

  Although not shown, the piping between the expansion valve 24-1 and the sample table 4 and the piping between the expansion valve 24-2 and the sample table 4 are covered with a heat insulating material, and are thus insulated. Yes.

  Note that if the opening of the expansion valve 24-1 is reduced, the pressure of the refrigerant in the refrigerant flow path 20 is reduced, so that the temperature is lowered. Conversely, if the opening of the expansion valve 24-1 is increased, the pressure of the refrigerant is increased, so the temperature is Go up. Further, if the opening degree of the expansion valve 24-2 is decreased, the refrigerant pressure in the refrigerant flow path 20 increases, so that the temperature rises. Conversely, if the opening degree of the expansion valve 24-2 is increased, the refrigerant pressure decreases, so that the temperature increases. Go down.

  When the rotation speed of the compressor 22 is increased, the flow rate of the refrigerant introduced into the sample stage 4 is increased, so that the pressure is increased and the temperature is increased. By controlling the opening degree of the expansion valve 24-1 and the expansion valve 24-2 and the rotational speed of the compressor 22, the sample stage 4 is controlled to a desired temperature. As a result, the sample 5 is suitable for the plasma etching process. Controlled to target temperature.

  Vibration sensors 37-1 to 37-3, which are detectors for detecting vibrations, are arranged at a plurality of locations on the lower surface of the sample stage 4 of the present embodiment, whereby vibrations in the vicinity of the arranged locations are detected. . In this embodiment, an AE sensor (Acoustic Emission Sensor) is used as the vibration sensor.

  2 is an enlarged horizontal and vertical cross-sectional view showing the configuration of the sample stage of the embodiment shown in FIG. FIG. 2A is a cross-sectional view of the sample table 4 as viewed from above.

  Inside the sample stage 4 used in the present embodiment, as shown in this figure, a planar shape in which a plurality of refrigerant flow paths are arranged substantially concentrically at a plurality of different radius positions is an arc-shaped portion. There are multiple. Here, the flow paths are connected to each other in order to allow the coolant to flow from an arc-shaped flow path at a certain radius position to an arc-shaped flow path at a different radial position outside or inside. A passage having an arcuate planar shape having a smaller radius of curvature is disposed, and a portion of the passage or a portion of the sample table 4 on which the passage is disposed is referred to as a bent portion.

  The refrigerant introduced from the refrigerant inlet 30 divides in two directions as indicated by arrows, circulates along the refrigerant flow path 20, and flows to the inner flow path via the bent portion 31. Thus, after circulating through the substantially concentric flow path and the bent portion 31, the refrigerant joins in the vicinity of the refrigerant outlet 32 and is discharged from the sample outlet 4 from the refrigerant outlet 32, as shown in FIG. Return to the correct refrigerant temperature control unit 21. Such a configuration improves the temperature uniformity of the sample or sample stage in the circumferential direction at different radius positions.

  FIG. 2B is a diagram showing a configuration in the vicinity of the sample stage 4. The sample stage 4 is composed of two metal (for example, aluminum alloy) discs 35-1 and 35-2. On the bottom surface of the disc 35-1, a groove having a rectangular channel cross section as viewed from above as shown in FIG. 2A is disposed, and a groove is formed on the bottom surface of the disc 35-1. The refrigerant flow path 20 is configured by joining a region where no digging is made and the upper surface of the disk 35-2. Therefore, the joined region is a portion indicated by hatching in FIG.

  In this embodiment, the state of the refrigerant was detected by arranging a vibration sensor on the lower surface of the sample stage 4 and measuring the vibration generated by the refrigerant. Moreover, the vibration accompanying peeling of the joined disk 35-1 and disk 35-2 was also detected.

  Hereinafter, the location of the vibration sensor will be described with reference to FIG. In addition, in order to help an understanding about an arrangement location, the arrangement location of the vibration sensors 37-1 to 37-3 was also shown with the broken line also in Fig.2 (a).

  A vibration sensor 37-1 is arranged on the lower surface of the sample table 4 and in the vicinity of the refrigerant inlet 30, and a vibration sensor 37-3 is arranged on the lower surface of the sample table 4 and in the vicinity of the inner refrigerant outlet 32. Furthermore, a vibration sensor 37-2 is arranged on the lower surface of the sample stage 4 and in the vicinity of the bent portion 31. By arranging vibration sensors at these locations, vibrations in the vicinity of each can be detected. For example, since the vibration sensor 37-1 is disposed in the vicinity of the refrigerant inlet 30, vibration in the vicinity of the refrigerant inlet 30 can be detected. Further, vibration signals detected by the vibration sensors 37-1 to 37-3 are sent to the signal processing unit 39 for processing.

  Hereinafter, a specific method for evaluating vibrations detected by the vibration sensors 37-1 to 37-3 will be described. In the present embodiment, the purpose of arranging the vibration sensors 37-1 to 37-3 on the lower surface of the sample stage 4 is mainly to detect vibrations accompanying boiling of the refrigerant in a gas-liquid mixed phase state. However, there are other vibrations detected on the lower surface of the sample stage 4. For example, the vibration from the floor where the plasma processing apparatus is disposed, the vibration of the turbo molecular pump 12 attached to the processing chamber wall 1, and the like are noise components in the detection in this embodiment.

  Therefore, in order to separate vibration and noise components due to the boiling of the refrigerant, spectrum analysis using fast Fourier analysis, which is generally used for analysis of vibration data such as sound, is performed. It can be converted into a power spectrum indicating intensity. Moreover, a sound pressure level is obtained by decibel transforming the obtained power spectrum. The decibel transform expresses the power spectrum by the common logarithm of the ratio to the reference value, and generally the sound pressure level Lp is obtained from the intensity p at a certain frequency by the equation (1).

Lp = 20 × log ₁₀ (p / p ₀ ) (1)
Here, p ₀ = 20 × 10 ⁻⁶ [Pa] (Pascal)
Since the obtained sound pressure level is data including a noise component, the sound pressure level less than a certain threshold is regarded as noise, and the sound pressure level higher than that is used for the analysis of the vibration accompanying the boiling of the refrigerant. In this embodiment, the threshold is set to 0. This operation removes weak noise components of the data from the vibration sensor. For example, the vibration from the floor where the plasma processing apparatus is placed, which is one of the noises described above, is removed by this operation.

  The results detected by the vibration sensor 37-1 and the vibration sensor 37-3 arranged using the method as described above are shown as time series data in FIGS. 3A and 3C, respectively. Moreover, the detection result by one of the plurality of vibration sensors 37-2 is shown in FIG. FIG. 3 is a graph showing, in time series, outputs detected by the vibration sensors arranged on the sample stage of the first embodiment shown in FIG. These graphs are obtained in a state where the plasma 11 is generated in the processing chamber 3 and in a state where the refrigerant is supplied to the refrigerant flow path 20 by the refrigerant temperature adjusting unit 21. The frequency and the vertical axis indicate the sound pressure level.

  Here, in particular, FIG. 3C shows a detection result obtained when no dry-out occurs at the refrigerant outlet 32. In the graph of FIG. 3A, the peak 40-a appears at frequencies of 450 Hz, 900 Hz, and 1350 Hz. These are determined to be caused by the operation of the turbo molecular pump 12 because they coincide with the fundamental frequency 450 Hz of the rotational speed 27000 rpm of the turbo molecular pump 12 and the secondary frequency 900 Hz and the tertiary frequency 1350 Hz.

  Also, in the detection results of the vibration sensor 37-2 and the vibration sensor 37-3 shown in FIGS. 3B and 3C, respectively, the same frequency as that of the peak 40-a (that is, 450 Hz, 900 Hz, 1350 Hz). The peaks shown as the peak 40-b and the peak 40-c appear, respectively. Furthermore, the sound pressure levels of these peaks 40-ac are almost the same. This is because the sample stage 4 is mechanically connected to the processing chamber wall 1, and the vibration of the turbo molecular pump 12 is transmitted to the vibration sensors 37-1 to 3-3 disposed on the lower surface of the sample stage 4 with substantially the same strength. As a result, vibration was detected at almost the same sound pressure level.

  Further, in FIGS. 3A to 3C, peaks 41-a to c appear in the vicinity of 650 Hz in addition to the peaks 40-a to c. Here, the detection result of the vibration sensor 37-2 in a state where the turbo molecular pump 12 is operated, the operation of the refrigerant temperature adjusting unit 21 is stopped, and the supply of the refrigerant to the refrigerant channel 20 is stopped is shown in FIG. d). When the refrigerant is flowing, a peak 41-b appears in the vicinity of 650 Hz as shown in FIG. 3B, whereas when the refrigerant is not flowing, it is shown in FIG. Thus, no peak appears in the vicinity of 650 Hz. Although not shown here, when no refrigerant is flowing, no peak appears in the vicinity of 650 Hz in the detection results of the vibration sensor 37-1 and the vibration sensor 37-3 as in FIG. . Therefore, it is determined that the peaks 41-a to c appear only when the refrigerant is flowing.

  When the peaks 41-ac in the vicinity of 650 Hz in FIGS. 3A to 3C where the refrigerant is flowing are compared, there is a difference in the size of the peaks. Here, since the height of the peak 41-a in the vibration sensor 37-1 disposed in the vicinity of the refrigerant inlet 30 is extremely small, this peak is caused by vibration accompanying boiling of the refrigerant. This is because, in the vicinity of the refrigerant inlet 30, it is immediately after the refrigerant having almost zero dryness is introduced into the refrigerant flow path 20, and receives almost no heat from the plasma 11, so that almost no boiling occurs. This is because no vibration occurs as a result.

  Further, in the detection result of the vibration sensor 37-2 arranged in the vicinity of the bent portion 31 shown in FIG. 3B, the heat input from the plasma 11 is received in the process in which the refrigerant flows from the refrigerant inlet 30 to the bent portion 31. When the boiling occurs vigorously, the vibration increases, and as a result, the peak 41-b near 650 Hz is higher than the peak 41-a. Further, in the detection result (FIG. 3B) of the vibration sensor 37-3 disposed in the vicinity of the inner refrigerant outlet 32 located downstream of the bent portion 31-1, the peak 41-c is the peak 41-b. The sound pressure level is lower than. This is because boiling continues due to heat input from the plasma 11 while the refrigerant flows from the bent portion 31 to the refrigerant outlet 32, and the dryness is high, that is, the proportion of the liquid in the gas-liquid mixed phase state is reduced. This is because the magnitude of vibration caused by boiling has been reduced.

  From the above, it is concluded that the peaks 41-ac in the vicinity of 650 Hz in FIGS. 3A to 3C are due to vibration caused by boiling.

  Next, dryout occurs before the refrigerant reaches the refrigerant outlet 32, and as a result, the detection result of the vibration sensor 37-3 in a state in which all the refrigerant at the refrigerant outlet 32 becomes gas is shown in FIG. Show. The dryout at the refrigerant outlet 32 occurs when the amount of heat input from the plasma 11 to the sample table 4 is too large or the flow rate of the refrigerant introduced into the refrigerant flow path 20 is too small. As shown in FIG. 3E, when dryout occurs, a peak around 650 Hz does not appear.

  The vibration due to boiling indicated by the peaks 41-a to c in FIGS. 3A to 3C occurs when bubbles are generated in the liquid and when the bubbles rise to the gas-liquid interface and the bubbles are blown. Therefore, as shown in FIG. 3 (e), when the refrigerant outlet 32 is dry-out, the refrigerant is evaporated and becomes only gas, so no vibration occurs and no peak near 650 Hz appears. .

  As described above, in the detection result of the vibration sensor 37-3 arranged in the vicinity of the refrigerant outlet 32, when the peak 41-c indicating the boiling of the refrigerant appears, the dry-out has not occurred, and the peak 41 If -c does not appear, it can be considered that dryout has occurred.

  Spectral analysis using fast Fourier analysis is performed on each vibration data detected by the vibration sensors 37-1 to 3-3 as described above, and a sound pressure level is calculated by conversion to a power spectrum and decibel conversion. The signal processing unit 39 performs processing for extracting a peak of 0 or more, identifying a peak indicating boiling of the refrigerant, and determining the presence or absence of dryout based on the height.

  Here, the operation of this embodiment when the signal processing unit 39 determines that a sign of dryout has been detected will be described. In the present embodiment, when the sound pressure level of the peak 41-c indicating the boiling of the refrigerant in the detection result of the vibration sensor 37-3 is lower than a certain threshold (for example, 3 decibels), the flow rate of the refrigerant is Increased. Accordingly, the flow rate of the refrigerant is increased and the refrigerant is discharged from the refrigerant outlet 32 before being completely vaporized, so that dryout is avoided.

  For this reason, the rotation speed of the compressor 22 in the refrigerant temperature adjusting unit 21 is increased. However, when the rotation speed of the compressor 22 is increased, the temperature of the refrigerant in the refrigerant flow path 20 is increased, and the temperatures of the sample stage 4 and the sample 5 are increased. As a result, since the sample 5 rises above the target temperature, the etching process is adversely affected.

  In order to prevent this, the rotation speed of the compressor 22 is increased in the refrigerant temperature adjusting unit 21, and the opening degree of the expansion valve 24-1 is lowered or the opening degree of the expansion valve 24-2 is increased. By this operation, an increase in the temperature of the refrigerant is suppressed while increasing the flow rate of the refrigerant. Further, by performing such an operation, when the dryness at the refrigerant outlet 32 decreases and the peak 41-c of the detection result of the vibration sensor 37-3 becomes higher than a certain threshold value, the dryout is suppressed. Therefore, the rotation speed of the compressor 22 and the opening degree of the expansion valve 24-1 and the expansion valve 24-2 may be maintained. Such an operation improves the accuracy and reliability of sample processing by maintaining and adjusting the temperature of the sample 5 within a desired range while suppressing dry-out.

  In adjusting the flow rate and temperature of the refrigerant as described above, the rotation speed of the compressor 22, the opening degree of the expansion valve 24-1 and the expansion valve 24-2, and the temperature of the refrigerant or the temperature of the sample table 4 are It is desirable to obtain the correlation and relationship in advance through experiments and record the data. In the present embodiment, the refrigerant temperature adjusting unit control unit 33 reads out the data stored in the internal storage device (not shown) by the arithmetic unit, and similarly uses the above data in accordance with the program stored in the storage device. The value of the refrigerant temperature to be set is selected, and a command signal is transmitted to the refrigerant temperature adjustment unit 21 via the input / output interface so as to adjust to the temperature.

  The operation of the rotational speed of the compressor 22 of the refrigeration cycle and the opening degree of the expansion valve 24-1 and the expansion valve 24-2 that have received the signal are adjusted by these drive devices (not shown), and the refrigerant temperature is adjusted to a desired value. Is done. Furthermore, a temperature meter is arranged on the sample stage 4 or a temperature of the refrigerant is measured by a thermometer 27 arranged inside the refrigerant temperature adjusting unit 21, and the compressor 22 is adjusted so that the temperature falls within a predetermined range. Or the like may be transmitted from the refrigerant temperature control unit 33.

  In this embodiment, the peak of vibration accompanying the boiling of the refrigerant appears in the vicinity of 650 Hz, but it does not always appear at this frequency. Since this vibration is caused by the generation and disappearance of bubbles as described above, it is affected by physical properties such as the viscosity, density and surface tension of the refrigerant and the dryness. In addition, since these physical properties are affected by the type and temperature of the refrigerant, it is difficult to predict in advance which frequency the vibration peak due to the boiling of the refrigerant will appear. However, the vibration of the turbo molecular pump 12, which may be confused with the vibration due to the boiling of the refrigerant, is distinguished from the fact that the sound pressure level is very high as described above, and the peak frequency appears at an integer multiple of the rotation speed. It becomes possible to do.

  Therefore, in this embodiment, the vibration spectrum associated with the boiling of the refrigerant is detected by distinguishing the vibration associated with the boiling of the refrigerant and the vibration of the turbo molecular pump 12. In addition, as described above, the detection result at the position where the refrigerant is boiling (FIG. 3B), the operation of the refrigerant temperature adjusting unit 21-1 is stopped, and the refrigerant is supplied to the refrigerant flow path 20. By comparing the detection result in the case of stopping (FIG. 3D), it becomes easy to determine the peak frequency indicating the vibration accompanying the boiling of the refrigerant.

  In the sample stage 4 of the present embodiment, a total of eight vibration sensors 37-1, one for each of the refrigerant inlet 30 and the refrigerant outlet 32 and one for the vicinity of the six bent portions 31. Although 3 is arranged, the number of arrangement is not limited to this. In the structure of the refrigerant flow path 20 shown in the present embodiment, the refrigerant is not cooled, and flows while receiving heat from the wall surface of the refrigerant flow path 20 while boiling. Generally, the closer to the refrigerant outlet, the higher the dryness. Therefore, if the vibration sensor 37-3 is arranged only at one location near the refrigerant outlet 32 and the vibration accompanying the boiling of the refrigerant is detected, the minimum dryout detection is possible.

  Further, by detecting the vibration at the bent portion 31 with the vibration sensor 37-2 arranged in the vicinity of the bent portion 31, whether the refrigerant is normally evaporated while flowing the refrigerant, or the sample table 4 It is possible to determine with good sincerity whether the cooling is being performed or the state is abnormal. Further, by detecting the vibration near the refrigerant inlet 30 by the vibration sensor 37-1, the dryness of the refrigerant near the refrigerant inlet 30 is 0 (0%) or a value close to this (the refrigerant is in a saturated liquid state). Therefore, it is possible to improve the necessity and accuracy of the refrigerant temperature adjustment by the refrigerant temperature adjustment unit 21.

  Further, when the amount of heat received by the sample 5 or the sample stage 4 from the plasma 11 is very large and the flow rate of the refrigerant is small, there is a possibility that dryout may occur before the refrigerant introduced from the refrigerant inlet 30 reaches the bent portion 31. is there. In that case, the peak indicating the vibration accompanying the boiling of the refrigerant is not detected by the vibration sensor 37-2 and the vibration sensor 37-3, but is detected only by the vibration sensor 37-1. In that case, since it is necessary to increase the flow rate of the refrigerant further than when the dry-out occurs between the bent portion 31 and the refrigerant outlet 32 as described above, the rotation speed of the compressor 22 is further increased and the expansion is performed. By reducing the opening degree of the valve 24-1 or increasing the opening degree of the expansion valve 24-2, the refrigerant can be maintained at the target temperature while increasing the flow rate of the refrigerant. Thus, by determining at which point in the refrigerant flow path 20 the dry-out occurs, the reliability of control of the refrigerant flow rate can be improved. Therefore, it is desirable to arrange a plurality of vibration sensors as shown in this embodiment.

  In addition, as described above, by arranging a vibration sensor at a position below the flow path and between the refrigerant inlet 30 and the refrigerant outlet 32, the accuracy of detection of an indication of the occurrence of dryout and its location. In addition, the effect of reducing the accumulation of bubbles generated by evaporation and the suppression of dry-out by adjusting the supply of refrigerant performed based on the detection results is improved. In addition, it is desirable to arrange these detection means in the vicinity of the bent portion 31 and the like.

  This is because in the refrigerant flow path 20, the radius of curvature in each flow path becomes the smallest at the bent portion 31, and therefore the stress of trying to separate the disk 35-1 and the disk 35-2 by the internal pressure of the refrigerant. Concentration is likely to occur at the joint in the vicinity of the bent portion 31, and there is a high possibility that incomplete joining such as peeling or cracking occurs. Therefore, by arranging the vibration sensor 37-2 in the vicinity of the bent portion 31, not only the vibration due to the boiling of the refrigerant, but also the vibration accompanying the separation is detected when the joint is separated, and the occurrence of the separation is detected. Is possible.

  In such a configuration, as a result of detecting the vibration, a signal is output from each vibration sensor 37-1, 2, etc. and sent to the signal processing unit 39. When it is determined that the vibration is accompanied, the processing result is transmitted to the apparatus control unit 43 via the communication unit, and the apparatus control unit 43 determines that the abnormality has occurred according to the program stored in the internal storage unit in advance. Information is displayed using the notification means provided in the apparatus, or displayed on the monitor of the user's command input device. For example, a warning is displayed on the control screen displayed on the CRT monitor for command input to notify the operator.

  As described above, the output from the detecting means arranged on the lower surface of the sample stage 4 is received to detect the dryness of the refrigerant flowing and the occurrence of dryout, and based on the result, the refrigerant temperature adjusting unit 21 Owing to the operation of the refrigeration cycle or the flow of the refrigerant, and the temperature of the refrigerant introduced into the refrigerant flow path 20 in the sample table 4 is adjusted to a desired value, the occurrence of dryout is suppressed, and the temperature of the sample 5 being processed is controlled. Maintaining within a desired range improves processing accuracy, yield, and reproducibility. In addition, by detecting the occurrence of separation at the bent portion 31 where the joint portion of the sample stage 4 is likely to be peeled off at an early stage, the amount of work and time required for maintenance and inspection can be reduced, and the reliability or apparatus of the plasma processing apparatus can be reduced. The efficiency of processing by the is improved.

[Modification 1]
In the above embodiment, the refrigerant channel 20 inside the sample stage 4 is one system, that is, the refrigerant supplied to the refrigerant channel 20 is adjusted to one condition, and the sample stage 4 is adjusted to substantially one temperature. The configuration was In that case, the surface of the sample stage 4 and the temperature of the sample 5 are substantially uniform in the plane.

  On the other hand, when a plurality of systems, for example, two systems of refrigerant flow paths are formed in the sample table 4 and a refrigerant having a higher temperature is introduced into the inner system than the outer system, the temperature of the sample table 4 or the sample 5 is set. A highly convex distribution can be achieved on the inside.

  In the etching process for forming the gate electrode, the density of the reaction product generated in the process is increased on the inner peripheral side. Therefore, by increasing the temperature of the sample 5 on the inner side, the adhesion coefficient of the reaction product to the gate is increased. As a result, the gate electrode dimensions are generally processed so as to be uniform within the surface of the sample 5. In order to control the temperature distribution of the sample 5 and the sample stage 4 in this way, a configuration in which a plurality of refrigerant flow paths are formed inside the sample stage 4 will be described with reference to FIG. 4 as a modification of the above embodiment. explain.

  FIG. 4 is a horizontal and vertical cross-sectional view schematically showing the configuration of the sample stage according to the modification of the embodiment shown in FIG. FIG. 4A is a view showing an upper section of the sample stage 4. The sample stage 4 is provided with an inner refrigerant flow path 20-1 and an outer refrigerant flow path 20-2 in order to have a temperature distribution in the radial direction, which are substantially concentric flow paths as in the first embodiment. And a bent portion. In addition, the direct expansion type refrigerant temperature adjustment unit 21-1 and the refrigerant temperature adjustment unit 21-2 described in the above embodiment are connected to the inner refrigerant channel 20-1 and the outer refrigerant channel 20-2, respectively. Has been.

  In the inner refrigerant flow path 20-1, the refrigerant introduced from the inner refrigerant inlet 30-1 is divided into two directions and circulated along the inner refrigerant flow path 20-1, and further via the bent portion 31-1. It flows in the flow path on the inner circumference side. The refrigerant flowing in two directions as described above merges in the vicinity of the inner refrigerant outlet 32-1 and is discharged from the inner refrigerant outlet 32-1 to the outside of the sample table 4 to adjust the refrigerant temperature as shown in FIG. Return to Part 21-1.

  Similarly, also in the outer refrigerant channel 20-2, the refrigerant introduced from the outer refrigerant inlet 30-2 divides into two hands and circulates along the outer refrigerant channel 20-2, and passes through the bent portion 31-2. Further flows into the flow path on the inner peripheral side. The refrigerant that has flowed in two steps as described above joins at the outer refrigerant outlet 32-2, and flows out of the sample stage 4 from the outer refrigerant outlet 32-2.

  FIG. 4B is a diagram showing a configuration in the vicinity of the sample table 4. As in the above embodiment, the vibration sensor 37-1 is located on the lower surface of the sample stage 4 and near the inner refrigerant inlet 30-1, and the vibration sensor is located on the lower surface of the sample stage 4 and near the inner refrigerant outlet 32-1. 37-3 is the lower surface of the sample stage 4 and in the vicinity of the outer refrigerant inlet 30-2, and the vibration sensor 37-4 is the lower surface of the sample stage 4 and in the vicinity of the outer refrigerant outlet 32-2. 6 was placed. Furthermore, a vibration sensor 37-2 is disposed on the lower surface of the sample table 4 and in the vicinity of the bent portion 31-1, and a vibration sensor 37-6 is disposed on the lower surface of the sample table 4 and in the vicinity of the bent portion 31-2. .

  By arranging the vibration sensors at these places, vibrations in the vicinity thereof can be detected as in the embodiment. The vibration signals detected by the vibration sensors 37-1 to 37-6 are sent to the signal processing unit 39 for processing.

  The method of detection by these vibration sensors 37-1 to 6 is the same as in the first embodiment. That is, vibrations of the refrigerant at the inner refrigerant inlet 30-1, the bent portion 31-1, the inner refrigerant outlet 32-1, the outer refrigerant inlet 30-2, the bent portion 31-2, and the outer refrigerant outlet 32-2 are detected by the vibration sensor 37-. Detect with 1-6. In addition, spectrum analysis using fast Fourier analysis is performed on each vibration data detected by the vibration sensors 37-1 to 6-6, and a sound pressure level is calculated by conversion to a power spectrum and decibel conversion. Is extracted, the peak indicating the boiling of the refrigerant is identified, and the signal processing unit 39 performs the process of determining the presence or absence of the dryout based on the height thereof, and the inner refrigerant outlet 32-1 or the outer refrigerant outlet 32-2. It is then determined whether or not the refrigerant has been dried out.

  When the signal processing unit 39 determines that a sign of dryout has been detected, the temperature controller 21 controls the refrigerant temperature controller 21-1 or the compressor in the refrigerant temperature controller 21-2. The rotational speed of 22 and the opening degree of the expansion valve 24-1 and the expansion valve 24-2 are controlled in the same manner as in the first embodiment, and while preventing dryout, the inner refrigerant flow path 20-1 and the outer refrigerant flow path 20- 2 can be controlled to a desired value. When peeling of the joint portion of the sample stage 4 is detected by the vibration sensors 37-1 to 37-6, a warning indicating that an abnormality has occurred is issued to the plasma etching apparatus by the apparatus control unit 43.

  By implementing the apparatus configuration and operation as described above, even when a plurality of refrigerant flow paths, that is, the inner refrigerant flow path 20-1 and the outer refrigerant flow path 20-2 are provided on the sample stage 4, the same as in the embodiment. In addition, the temperature of the refrigerant introduced into each of them is controlled to a desired value while preventing dryout, and as a result, the temperature distribution of the sample 4 can be controlled and a good etching process can be performed. Further, as in the first embodiment, it is possible to detect the occurrence of peeling at the bent portion 31-1 and the bent portion 31-2 where the bonded portion of the sample table 4 is likely to be peeled off.

  Here, the positional relationship between the inner refrigerant inlet 30-1 and the inner refrigerant outlet 32-1 in the present embodiment will be described. In this embodiment, the inner refrigerant inlet 30-1 is arranged on the inner peripheral side with respect to the inner refrigerant outlet 32-1.

  In the present embodiment, the temperature of the refrigerant introduced into the inner refrigerant flow path 20-1 is introduced into the outer refrigerant flow path 20-2 so that the temperature of the sample 5 is higher in the central portion than the outer peripheral portion. Higher than the temperature of the refrigerant. At that time, the refrigerant having a degree of dryness of approximately 0 introduced from the inner refrigerant inlet 30-1 is boiled by receiving heat input from the plasma 11, and the inner circumference side of the inner refrigerant flow path 20-1 while increasing the degree of dryness. And the outer peripheral side of the inner refrigerant channel 20-1 is heated from the plasma 11 and then cooled from the outer refrigerant channel 20-2 adjacent to the outer peripheral side. It circulates while being discharged from the inner refrigerant outlet 32-1.

  In that case, if the degree of dryness of the refrigerant in the bent portion 31-1 is sufficiently high, the amount of cooling heat from the outer refrigerant flow path 20-2 is larger than the amount of heating heat from the plasma 11, and the degree of dryness is high. Even if it circulates on the outer peripheral side of the inner refrigerant flow path 20-1 while being lowered, it is suppressed that the dryness is reduced to zero before reaching the inner refrigerant outlet 32-1. Therefore, the dryness of the refrigerant introduced from the inner refrigerant flow path 20-1 does not become zero before being discharged from the inner refrigerant outlet 32-1. Thus, when the dryness of the gas-liquid mixed phase refrigerant is not 0, the temperature of the refrigerant does not change, so the refrigerant temperature does not change in the process of flowing through the inner refrigerant flow path 20-1. Therefore, the sample stage 4 and the sample 5 can realize a temperature distribution without any deviation in the circumferential direction.

  On the other hand, when the inner refrigerant inlet 30-1 is arranged on the outer peripheral side of the inner refrigerant outlet 32-1, contrary to the present embodiment, for example, in FIG. The refrigerant is introduced and discharged from the inner refrigerant inlet 30-1. When the temperature of the refrigerant introduced into the inner refrigerant flow path 20-1 is higher than the temperature of the refrigerant introduced into the outer refrigerant flow path 20-2, the dryness introduced from the inner refrigerant outlet 32-1 is almost equal. The 0 refrigerant receives heat input from the plasma 11 and circulates while being cooled from the innermost flow path of the outer refrigerant flow path 20-2 adjacent to the outer peripheral side, and enters the bent portion 31-1. To reach.

  In this case, if the amount of cooling heat from the outer refrigerant flow path 20-2 is larger than the amount of heating heat from the plasma 11, the temperature of the inner refrigerant flow path 20-1 decreases while the dryness remains zero. It circulates on the outer peripheral side and reaches the bent portion 31-1. Therefore, the temperature distribution in the circumferential direction in the inner refrigerant flow path 20-1 is biased, and the temperature distribution in the circumferential direction of the sample table 4 and the sample 5 is biased. It will be damaged.

  In addition, the optimal value of the dryness of the refrigerant | coolant in the bending part 31-1 when the inner side refrigerant | coolant inlet 30-1 is arrange | positioned in the inner peripheral side rather than the inner side refrigerant | coolant outlet 32-1 like a present Example is an outer side refrigerant | coolant flow path. It is influenced by the amount of cooling heat from 20-2 and the amount of heating heat from the plasma 11. For example, if the former is larger than the latter, the degree of dryness of the refrigerant passing through the bent portion 31-1 gradually decreases when circulating through the flow path on the outer peripheral side of the inner refrigerant flow path. Therefore, the degree of dryness at the bent portion 31-1 needs to be sufficiently high so that the degree of dryness of the refrigerant does not become zero before being discharged from the inner refrigerant outlet 32-1.

  Conversely, when the amount of cooling heat from the outer refrigerant channel 20-2 is smaller than the amount of heating heat from the plasma 11, the refrigerant that passes through the bent portion 31-1 circulates in the outer peripheral channel of the inner refrigerant channel. When dry, the dryness gradually increases. Therefore, the degree of dryness at the bent portion 31-1 needs to be sufficiently low so that the dryness of the refrigerant does not become 1 before being discharged from the inner refrigerant outlet 32-1, that is, the dryout does not occur. is there. As described above, if the amount of heat input from the plasma and the amount of cooling from the adjacent refrigerant flow path are obtained in advance by calculation or experiment, and if the optimum dryness at the bent portion 31-1 is obtained, vibration during plasma processing will occur. Whether or not the dryness is an optimum value can be confirmed by the sensor 37-2. That is, when the optimum value of the dryness at the bent portion 31-1 is high and close to 1 (100%), the liquid portion of the refrigerant should be reduced, so the peak 41-b shown in FIG. Should be.

  On the other hand, when the optimum value of the dryness at the bent portion 31-1 is low, the peak 41-b shown in FIG. Should be. As described above, vibrations at the inner refrigerant inlet 30-1 and the inner refrigerant outlet 32-1 are detected by the vibration sensor 37-1 and the vibration sensor 37-3 during the plasma processing, and the bent portion is detected by the vibration sensor 37-2. By detecting the 31-1 vibration, it is possible to prevent the dryness from being 0 or dryout in the entire region of the inner refrigerant flow path 20-1.

  Further, regarding the arrangement of the refrigerant flow paths, when a plurality of refrigerant flow paths are provided inside the sample table 4 and refrigerants having different temperatures are introduced into the respective systems, the refrigerant flow paths are lower as shown in this embodiment. It is desirable that the dryness is increased by heating from the plasma 11 before the refrigerant reaches the flow path adjacent to the flow path through which the refrigerant of temperature passes. Thereby, the uneven temperature distribution in the circumferential direction of the sample stage 4 and the sample 5 is eliminated, and as a result, the in-plane distribution of the plasma etching process of the sample 5 can be made uniform.

[Modification 2]
Hereinafter, a third embodiment of the present invention will be described with reference to FIG. In the second embodiment, the vibration sensors 37-1 to 37-6 are directly arranged on the lower surface of the sample stage 4. However, in the etching process, in order to draw ions in the plasma 11 into the sample 5 that is the object to be processed, a high frequency power source 53 is often connected to the sample stage 4 to apply a high frequency. In that case, since the high frequency adversely affects the vibration sensors 37-1 to 37-6, they cannot be arranged directly on the lower surface of the sample stage 4. The second embodiment of the present invention addresses this problem. Like the first embodiment, the vibration due to the boiling of the refrigerant introduced into the sample stage 4 is detected by the vibration sensor, and the dryout of the refrigerant is detected. Unlike the first embodiment, a pipe made of an electrically insulating material (for example, alumina ceramics) is arranged below the sample stage 4, and a vibration sensor is arranged on the insulating pipe to detect vibration.

  FIG. 5 shows the vicinity of the sample stage used in this embodiment and the components connected thereto. Here, although a cross-sectional view of the sample stage 4 seen from above is not shown, the same sample stage 4 as that shown in the second embodiment of the present invention is used. A circular portion is connected to the inner refrigerant inlet 30-1, the inner refrigerant outlet 32-1, the outer refrigerant inlet 30-2 and the outer refrigerant outlet 32-2. Are formed, and the insulating pipes 51-1 to 5-4 are respectively inserted and connected to the holes. An O-ring 57 is disposed on each of the insulating pipes 51-1 to 51-4 to form a shaft seal structure, and is introduced into or discharged from the inner refrigerant flow path 20-1. Sealed to prevent leakage of refrigerant. Furthermore, a vibration sensor 37-1, a vibration sensor 37-3, a vibration sensor 37-4, and a vibration sensor 37-6 are directly arranged in these insulating pipes 51-1 to 51-4. Although not shown, the insulating pipes 51-1 to 51-4 in the region where the vibration sensor 37-1, the vibration sensor 37-3, the vibration sensor 37-4, and the vibration sensor 37-6 are not disposed are covered with a heat insulating material. It is insulated by this.

  These insulative pipes 51-1 to 51-4 are firmly in contact with and fixed to the lower surface of the sample stage 4, so that the inner refrigerant inlet 30-1, the inner refrigerant outlet 32-1, the outer refrigerant inlet 30-2, and the outer refrigerant. The vibration due to the refrigerant at the outlet 32-2 can be detected by the vibration sensor 37-1, the vibration sensor 37-3, the vibration sensor 37-4, and the vibration sensor 37-6 via the insulating pipes 51-1 to 51-4. .

  Furthermore, a member made of an insulating material is provided directly below the bent portion 31-1 of the inner refrigerant channel 20-1 and the bent portion 31-2 of the outer refrigerant channel 20-2 and on the lower surface of the sample table 4. The insulating pipe 55-1 and the insulating pipe 55-2 are firmly contacted and fixed, and the insulating pipe 55-1 and the insulating pipe 55-2 are respectively connected to the vibration sensor 37-2 and the vibration sensor 37. -5 is firmly contacted and fixed. Thereby, the vibration of the refrigerant | coolant in the bending part 31-1 and the bending part 31-2 can be detected with the vibration sensor 37-2 and the vibration sensor 37-5. In this configuration, since each of the insulating pipes 55-1 to 55-4 and the sample table 4 are firmly contacted and fixed, the vibration sensor 37-1 is located at any position of the insulating pipes 55-1 to 55-4. The vibration can be detected even if the vibration sensor 37-3, the vibration sensor 37-4, and the vibration sensor 37-6 are arranged. However, when the respective vibration sensors are separated from the sample stage 4 and are arranged at positions close to the refrigerant temperature adjusting unit 21-1 or the refrigerant temperature adjusting unit 21-2, the expansion valve 24-1, the expansion valve 24-2, Since the vibration of driving parts such as the compressor 22 is also detected, the S / N ratio is lowered. Therefore, it is desirable to arrange each vibration sensor in a region close to the sample stage 4 of each insulating pipe.

  The method of detection by the vibration sensors 37-1 to 6 is the same as in the first embodiment. That is, vibrations of the refrigerant at the inner refrigerant inlet 30-1, the bent portion 31-1, the inner refrigerant outlet 32-1, the outer refrigerant inlet 30-2, the bent portion 31-2, and the outer refrigerant outlet 32-2 are detected by the vibration sensor 37-. It is determined whether or not the refrigerant is dry-out at the inner refrigerant outlet 32-1 or the outer refrigerant outlet 32-2, using the data detected at 1 to 6 and processed by the signal processor 39. When the signal processing unit 39 determines that the dry-out is about to occur, the rotation speed of the compressor 22 in the refrigerant temperature adjusting unit 21-1 or the refrigerant temperature adjusting unit 21-2 and the expansion valve 24-1. If the opening degree of the expansion valve 24-2 is controlled in the same manner as in the first embodiment, the refrigerant temperature inside the inner refrigerant flow path 20-1 and the outer refrigerant flow path 20-2 is set to a desired value while preventing dryout. Can be controlled to a value.

  Even when a high frequency is applied to the sample stage 4 by performing the apparatus configuration and operation as described above, the inner refrigerant flow path 20-1 and the outer refrigerant are prevented while preventing dryout as in the first embodiment. The temperature of the refrigerant introduced into the flow path 20-2 is controlled to a desired value, and as a result, the temperature distribution of the sample 4 can be controlled and a good etching process can be performed. Further, as in the first embodiment, it is possible to detect the occurrence of peeling at the bent portion 31-1 and the bent portion 31-2 where the bonded portion of the sample table 4 is likely to be peeled off.

[Modification 3]
In the first and second embodiments, the separation at the joint portion of the sample stage 4 is detected by the vibration sensors 37-1 to 37-6. On the other hand, in the third embodiment, a pressure gauge is arranged in the pipe between the refrigerant temperature adjusting unit 21-1 or the refrigerant temperature adjusting unit 21-2 and the sample stage 4, thereby detecting the pressure of the refrigerant and thereby providing a sample stage. Detecting the peeling of the joint 4 and the occurrence of refrigerant leakage. Hereinafter, the third embodiment will be described with reference to FIGS.

  FIG. 6 shows the vicinity of the sample stage 4 used in this embodiment and the components connected thereto. The structure of the sample stage 4 is the same as that shown in the upper sectional view of FIG. 2A, and will be described using the same reference numerals.

  A refrigerant temperature adjusting unit 21-1 and a refrigerant temperature adjusting unit 21-2 are connected to the inner refrigerant channel 20-1 and the outer refrigerant channel 20-2, respectively, and the refrigerant is supplied to the respective channels. Here, a pressure gauge 60-1 is connected to a pipe downstream of the expansion valve 24-1 inside the refrigerant temperature adjusting unit 21-1 and between the refrigerant inlet 30-1 and the inner refrigerant flow path. The pressure almost the same as the pressure of the refrigerant in 20-1 can be measured.

  FIG. 6A shows the time change of the refrigerant pressure detected by the pressure gauge 60-1 in such a configuration. When the set temperature of the refrigerant is not changed up and down and the amount of heat input from the plasma 11 to the sample 5 and the sample stage 4 does not change, the pressure of the refrigerant changes with time as in the pressure stabilization region 72-1. It becomes constant. In such a state, when peeling occurs at the joint portion of the sample stage 4, the volume of the refrigerant flow path increases rapidly, so that the pressure of the refrigerant decreases and a pressure change 72-2 occurs. Then, since the change in volume stops when the progress of peeling stops, the pressure change 72-2 of the refrigerant also stops and becomes constant again like the pressure stable region 72-3. Such a phenomenon is a change in pressure, such as when pressure decreases and recovers within a specific time, or when pressure suddenly decreases from a stable value and then recovers to a value close to or close to the original pressure value. Appears as fluctuations in the pressure of the series. The result of detecting the pressure of such a refrigerant is sent to the signal processing unit 39.

  When the pressure change 72-2 appears between the pressure stable region 72-1 and the pressure stable region 72-3 as shown in FIG. 7A and the magnitude thereof is equal to or greater than a predetermined threshold value. Is determined by the signal processing unit 39 as being peeled off, and the processing result is sent to the device control unit 43, or is determined by the computing unit of the device control unit 43 based on the signal from the signal processing unit 39 that has been examined, As a result, a warning indicating that an abnormality has occurred is issued to the plasma etching apparatus. For example, a warning is displayed on the control screen of the plasma etching apparatus to notify the operator.

  In general, a plasma etching apparatus repeats a plurality of wafer processes using the same processing conditions. At that time, the detection result of the refrigerant pressure is stored, and the detection result of the refrigerant pressure in the same type of processing in the past is stored. You may detect the change of a refrigerant | coolant pressure also by comparing. The refrigerant pressure detection result 75-1 when the plasma etching process is normally performed as shown by the broken line in FIG. 6B and the detection result when the pressure change 72-2 appears as shown by the solid line in FIG. By comparing with 75-2, it is possible to more reliably detect pressure fluctuations accompanying peeling of the joint portion of the sample stage 4.

  In the present embodiment, the pressure gauge 60-1 is disposed downstream of the expansion valve 24-1 and between the inner refrigerant inlet 30-1. However, the location is not limited thereto. Since the purpose of disposing the pressure gauge 60-1 is to detect the pressure of the refrigerant inside the refrigerant flow path 20-1, a place where the pressure as close as possible to the pressure can be measured is desirable. Therefore, it is necessary that there is no part with low conductance, such as valves, between the expansion valve 24-1 and the inner refrigerant inlet 30-1. Therefore, a pressure gauge 60-1 may be disposed downstream of the inner refrigerant outlet 32-1 and between the expansion valve 24-2.

  In the present embodiment, a pressure gauge 60-1 is disposed between the inner refrigerant inlet 30-1 and the refrigerant temperature adjusting unit 21-1 in order to detect the pressure of the refrigerant flowing inside the inner refrigerant flow path 20-1. However, similarly, the pressure of the refrigerant flowing inside the outer refrigerant flow path 20-2 is detected by disposing the pressure gauge 60-2 between the outer refrigerant inlet 30-2 and the refrigerant temperature adjusting unit 21-2. In addition, the signal processing unit 39 and the device control unit 43 can detect separation of the joint portion of the sample stage 4 and notify the operator of the abnormality. In addition, when there are a plurality of refrigerant channels (two in this embodiment) of the inner refrigerant channel 20-1 and the outer refrigerant channel 20-2 inside the sample stage 4 as in the present example, In all of the systems, it is desirable to arrange a pressure gauge between the refrigerant flow path and the refrigerant temperature adjusting unit.

  As described above, the pressure gauge 24-1 is arranged between the refrigerant temperature adjusting unit 21-1, the refrigerant temperature adjusting unit 21-2, and the sample stage 4, and the pressure of the refrigerant is detected, and the time variation is captured. It is possible to detect the peeling of the joint portion of the sample stage 4 and notify the operator of the abnormality.

  By applying the first to third embodiments described above, it is possible to prevent dry-out and to detect separation of the joint portion of the sample stage 4 that can occur when a direct expansion type temperature control unit is used in the plasma processing apparatus. It can be carried out.

  According to the above embodiment, the dryness of the refrigerant inside the sample stage is accurately detected to adjust the flow of the refrigerant, and the value of the temperature of the sample or the sample stage being processed or the circumferential or radial temperature of the sample Can be brought close to the desired distribution. In addition, it is possible to detect the separation of the joined portions of the members constituting the passage inside the sample stage early and with high accuracy. By these actions, the accuracy, reproducibility, or reliability of the processing of the sample of the plasma processing apparatus is improved.

DESCRIPTION OF SYMBOLS 1 Processing chamber wall 2 Processing chamber lid 3 Processing chamber 4 Sample stand 5 Sample 6 Gas introduction pipe 7 Processing gas 8 Exhaust port 9 Pressure control valve 10 Microwave 11 Plasma 12 Turbo molecular pump 20-1 Inner refrigerant flow path 20-2 Outside Refrigerant flow path 21-1, 2 Refrigerant temperature control unit 22 Compressor 23 Condenser 24-1, Expansion valve 25 Cooling water 26 Evaporator 27 Thermometer 30-1 Inner refrigerant inlet 30-2 Outer refrigerant inlet 31-1, 2 Bent part 32-1 Inner refrigerant outlet 32-2 Outer refrigerant outlet 33 Temperature adjusting part control part 35-1, disc 37-1-6 Vibration sensor 39 Signal processing part 40-a, 40-b, 40-c , 41-a, 41-b, 41-c Peak 41 Peak of vibration due to refrigerant boiling 43 Device control unit 51-1, 6-5-1, Insulating piping 53 High frequency power supply 57 O-ring 60-1, 2 Pressure Total

Claims (7)

A processing chamber that is arranged inside the vacuum vessel and in which plasma is formed inside, and a sample stage that is arranged below the processing chamber and on which the sample is placed. The refrigerant of the refrigeration cycle flows through the processing chamber. a sample stage having a cylindrical operating as an evaporator, a flow path of the refrigerant is disposed concentrically about the center of the arranged inside the sample stage the cylinder, the arranged sample stage below the refrigerant At least one detector connected to a location near the entrance to the inside of the sample stage to detect vibration of the sample stage, and the dryness of the refrigerant flowing through the inside of the flow path from the output from the detector And a controller for adjusting the operation of the compressor or the expansion valve that constitutes the refrigeration cycle based on the detection result.
A processing chamber that is arranged inside the vacuum vessel and in which plasma is formed inside, and a sample stage that is arranged below the processing chamber and on which the sample is placed. The refrigerant of the refrigeration cycle flows through the processing chamber. a sample stage having a cylindrical operating as an evaporator, a flow path of the refrigerant is disposed concentrically about the center of the arranged inside the sample stage the cylinder, the arranged sample stage below the refrigerant At least one detector connected to a location near the entrance to the inside of the sample stage to detect vibration of the sample stage, and the dryness of the refrigerant flowing through the inside of the flow path from the output from the detector A plasma processing apparatus comprising: an adjustment unit that is arranged between the compressor and the sample stage on the refrigeration cycle and adjusts the temperature of the refrigerant flowing into the sample stage based on the detection result.
3. The plasma processing apparatus according to claim 1, wherein the detector is connected to a location in the vicinity of an outlet of the refrigerant disposed on a lower surface of the sample stage.
4. The plasma processing apparatus according to claim 1 , wherein a plurality of flow paths of the refrigerant are arranged concentrically at different distances in the radial direction from the center inside the sample stage. 5. A plasma having an arc-shaped channel and a connecting channel that connects two of these arc-shaped channels, and the detector is disposed on the lower surface of the sample stage and in the vicinity of the connecting channel Processing equipment.
5. The plasma processing apparatus according to claim 4 , wherein the planar shape of the connection path has a planar shape having a curvature smaller than that of the arc-shaped flow path .
The plasma processing apparatus according to any one of claims 1 to 5, wherein the flow path of the sample stage is configured by joining two upper and lower members, and a connection path on a lower surface of the sample stage. The plasma processing apparatus which detects the defect of joining of the said upper and lower members from the output from the said detector connected and arrange | positioned at the location of the vicinity .
7. The plasma processing apparatus according to claim 1 , comprising an electrically insulating member disposed in contact with a lower surface of the sample stage, and in contact with the insulating member. A plasma processing apparatus in which the detector is disposed .

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