JP2010245218A - Plasma processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing apparatus that enhances the reproducibility of wafer processing precision by monitoring the secular change of a temperature sensor. <P>SOLUTION: A sample placing table 107 of the plasma processing apparatus includes a metallic substrate 201, a dielectric-made film 202 arranged on an upper surface of the substrate and having a sample mounted thereupon, a film-like heater 204 arranged in the film, a passage 203 which is disposed in the substrate and in which a refrigerant flows, and the sensor 205 which is inserted into the substrate and detects the temperature of the substrate, abnormality of the sensor being detected upon temporal variation in output from the sensor when a heater is supplied with predetermined electric power. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus, and more particularly, to a plasma processing apparatus capable of monitoring deterioration over time of a temperature sensor and suppressing a decrease in processing accuracy of a sample.

  In a plasma processing apparatus for processing a wafer placed in a processing chamber in a vacuum chamber using plasma generated in the processing chamber, the temperature of a sample mounting table placed in the processing chamber is adjusted to a temperature suitable for processing. It is important to process the wafer. For this reason, a temperature sensor is attached to the sample mounting table of the plasma processing apparatus.

  As described above, in the plasma processing apparatus, when a wafer is processed, the processing accuracy is increased by adjusting the temperature to a temperature suitable for the processing.

  Patent Document 1 is known as such a conventional technique. In Patent Document 1, the temperature of the sample mounting table is measured by a temperature sensor attached to the sample mounting table, the temperature of the wafer placed on the sample mounting table is estimated, and a wafer embedded in the upper part of the sample mounting table is used for the wafer. By heating the wafer, the wafer is adjusted to a temperature suitable for processing, and the wafer is processed with high accuracy.

JP 2008-177285 A

  In the prior art, since the measurement accuracy of the temperature sensor attached to the sample mounting table affects the control of the wafer temperature, the measurement accuracy of the temperature sensor is important for performing high-precision wafer processing.

  The temperature sensor is attached to the sample mounting table so as to reduce the contact thermal resistance. However, if the contact state with the sample stage changes due to a change over time or the like, the contact thermal resistance changes and the temperature measurement accuracy decreases. In this case, the measurement system measures a value different from the actual temperature, erroneous heater control is performed, and the accuracy of wafer processing decreases.

  The present invention has been made in view of these problems, and a plasma processing apparatus capable of monitoring a change in temperature sensor over time and detecting a decrease in temperature measurement accuracy before causing a decrease in wafer processing accuracy. It is to provide.

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

  A vacuum processing chamber, a high-frequency wave power source for generating plasma that supplies high-frequency energy to the introduced processing gas and generates plasma, and a sample mounting table disposed in the vacuum processing chamber; A plasma processing apparatus comprising a high-frequency bias power source for supplying a high-frequency voltage to the sample mounting table, wherein the sample mounting table performs plasma processing on the sample mounted on the sample mounting table by attracting ions in the plasma. A metal substrate, a dielectric film disposed on the upper surface of the substrate and on which the sample is placed, a film-shaped heater disposed in the film, and a substrate disposed in the substrate And a passage through which the refrigerant flows, and a sensor that is inserted inside the base material and detects the temperature of the base material, and the time change of the output from the sensor when a predetermined power is supplied to the heater. Based on the above Detecting an abnormality of the capacitor.

  Since the present invention has the above-described configuration, it is possible to detect a decrease in temperature measurement accuracy by monitoring a change with time of the temperature sensor without causing a decrease in wafer processing accuracy.

It is a figure explaining the plasma processing apparatus which concerns on embodiment of this invention. It is a figure explaining the detail of the sample mounting base arrange | positioned in a vacuum vessel. It is a figure explaining the method of detecting the fall of the temperature measurement precision accompanying a time-dependent change. It is a figure explaining the method of detecting the fall of the temperature measurement precision accompanying a time-dependent change. It is a figure which shows the example of a time-dependent change of time constant (tau).

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a plasma processing apparatus according to an embodiment of the present invention. In FIG. 1, the plasma processing apparatus includes a vacuum vessel 101 and a processing chamber 103 formed by the vessel, and the inside of the processing chamber 103 is decompressed by a vacuum exhaust device 102.

  A resonance container 106 is disposed above the processing chamber 103, and the microwave from the microwave source 104 is introduced into the resonance container 106 through the waveguide 105. A gas introduction system (not shown) is connected to the vacuum vessel 101.

  A sample mounting table 107 (sample mounting electrode) on which a wafer is mounted on the upper surface of the vacuum vessel 101 is disposed at the lower center of the vacuum vessel 101, and a bias voltage can be applied to the sample mounting table 107 by a bias power source 108. . The sample mounting table 107 is connected to a heater that controls the temperature of the wafer, a power source 109 for the heater, and a temperature controller 110 that circulates and supplies a coolant for cooling the sample mounting table. The heater power supply 109, the bias power supply 108, and the temperature controller 110 are connected to the user interface 112 via the controller 111.

  The gas introduced into the vacuum vessel 101 through the gas introduction system is turned into plasma by microwaves, and a predetermined plasma treatment can be performed on the wafer. The plasma generating means is not limited to the means using the microwave, but may be a plasma generating means using electrostatic coupling means or inductive coupling means using high frequency.

FIG. 2 is a diagram for explaining details of the sample mounting table 107 arranged in the vacuum vessel 101. The sample mounting table includes a base material portion 201 made of a metal such as Al or Ti, and a dielectric film 202 made of a dielectric material such as Al ₂ O ₃ . Here, the thickness of the base material part 201 is about 30 mm. In addition, a coolant groove 203 that is a flow path through which a coolant for cooling the substrate portion 201 flows is formed inside the substrate portion 201.

Further, the dielectric film 202 made of Al ₂ O ₃ or the like is formed by, for example, thermal spraying. An electrode film 204 having a heater function is disposed inside the dielectric film 202, and the dielectric film 202 covers the upper and lower sides thereof. The electrode film 204 is formed by thermal spraying, for example. The metal used for thermal spraying is W, a nickel-chromium alloy or nickel-aluminum alloy whose resistivity is controlled, or a metal whose resistivity is controlled such as a suitable additive metal mixed with W. Is used.

  The thickness of the dielectric film 202 sandwiching the electrode film 204 is about 0.5 mm, which is thinner than the substrate part 201 and has a low heat capacity. Therefore, the temperature of the dielectric film 202 can be changed stepwise by the electrode film 204 having a heater function.

  The base material part 201 has an opening for attaching a temperature sensor 205 for measuring the temperature of the base material part 201, and the temperature sensor 205 is attached to this opening part. As an element used for the temperature sensor 205, a platinum resistance thermometer or a thermocouple is used. In order to maintain good contact between the temperature sensor 205 and the base material part 201, a compression spring 206 is attached to the lower part of the temperature sensor 205, and the contact is maintained by compressing the compression spring 208 by the pressing part 207. Yes. The tip of the sensor is located on a surface between the passage and the surface on which the dielectric film is disposed. The temperature sensor 205 is connected to the user interface 112 through the controller 111.

  The controller 111 estimates the temperature of the wafer on the dielectric film 202 based on the temperature of the base material portion 201 obtained through the temperature sensor 205, and the heater power supply 109 so as to obtain a wafer temperature distribution suitable for processing. To control.

  In order to control the wafer temperature distribution with high accuracy, it is important to accurately obtain the temperature of the base material portion 201. The contact state between the base material portion 201 and the temperature sensor 205 due to a change over time or looseness of attachment or the like is important. When a change occurs, the temperature measurement accuracy may decrease with the change, and the wafer processing accuracy may decrease.

  FIG. 3 and FIG. 4 are diagrams for explaining a method for detecting a decrease in temperature measurement accuracy accompanying a change with time of the measurement system of the temperature sensor.

  First, the electrode 107 is adjusted to a constant temperature with a refrigerant. When constant power is supplied from the heater power supply 109 to the electrode film 204 having a heater function, the temperature of the dielectric film 202 rises in a stepped manner. The base material portion 201 is warmed by the dielectric film 202 whose temperature has increased, and the temperature indicated by the temperature sensor 205 also increases.

  FIG. 3 is a diagram showing a temporal change in temperature detected by the temperature sensor. From this relationship, a time constant τ specific to the contact portion between the base material portion and the temperature sensor can be obtained from the relationship described later. This value is a constant value unless the contact state changes. For this reason, it is possible to detect a decrease in temperature measurement accuracy due to a change with time by examining the change tendency of the time constant τ.

  FIG. 4 is a diagram illustrating an abnormality detection procedure. First, at time t1, after the temperature of the electrode is adjusted to be constant by the refrigerant, an abnormality detection execution command is output via the user interface. Note that the execution command may be output every predetermined period (step S401). Next, the temperature of the electrode 107 (starting temperature: T0) is acquired by the temperature sensor 205 (step S402). Thereafter, a constant power is supplied to the electrode film 204 by the heater power supply 109, and the temperature (attainment temperature: T1) of the electrode 107 is acquired at a time t2 after a predetermined time has elapsed (steps S403 and 404).

  Next, the amount of temperature change (ΔT) is obtained from the start temperature (T0) and the reached temperature (T1), and the time required for the temperature to change by a certain rate after applying power by the heater power supply 109 (time constant: (τ1) is obtained (step S406). As shown in FIG. 3, the time constant τ can be obtained as a time t (= t1−t0) required to reach about 63% of the temperature change amount ΔT.

  Next, the acquired time constant (τ1) is compared with the time constant (τ0) acquired at the start of operation of the plasma processing apparatus, for example. If the amount of change from the time constant at the start of operation exceeds the reference, it is determined that the temperature measurement accuracy has decreased due to changes over time, and it is determined that the sensor is abnormal (steps S408a and 409). If the amount of change is within the reference, it is determined as normal (steps S408b and 409). The determination result is displayed on the display (step S409).

Note that the temperature T0 of the sample mounting electrode at the start of measurement is desirably set to the same temperature T0 for each measurement. A table for measuring the time constant at the temperature Tn and converting the time constant at the temperature Tn into the time constant at the start temperature T0 is prepared, and correction is made according to this table (step S406).
FIG. 5 is a diagram illustrating an example of a change with time of the time constant τ. The amount of change from the reference is shown based on the time constant acquired at the start of operation of the plasma processing apparatus. In the example of the figure, the amount of change in the time constant from the initial stage to the 11th time after the start of operation is within the reference range obtained by the measurement error, and the temperature measurement accuracy is normal. However, the change amount of the time constant exceeded the reference at the 12th time after the start of operation, and it was detected that the temperature measurement accuracy was lowered. After the abnormality was detected, the temperature sensor 205 was readjusted to prevent a decrease in wafer processing accuracy.

  As described above, according to the present embodiment, it is possible to monitor the change over time of the temperature sensor based on the change in the time constant τ inherent in the contact portion between the base material portion and the temperature sensor, and the wafer processing accuracy It is possible to detect a decrease in temperature measurement accuracy without lowering.

DESCRIPTION OF SYMBOLS 101 Vacuum container 103 Processing chamber 104 Microwave source 107 Sample mounting base 109 Heater power supply 201 Base material part 202 Dielectric film 203 Refrigerant groove 204 Electrode film (heater)
205 Temperature sensor 206 Compression spring 207 Presser

Claims (5)

A vacuum processing chamber, a high-frequency wave power source for generating plasma that supplies high-frequency energy to the introduced processing gas and generates plasma, and a sample mounting table disposed in the vacuum processing chamber; A plasma processing apparatus comprising a high-frequency bias power source for supplying a high-frequency voltage to the sample mounting table, and performing plasma processing on the sample mounted on the sample mounting table by attracting ions in the plasma.
The sample mounting table includes a metal base material, a dielectric film disposed on the top surface of the base material on which the sample is placed, a film-like heater disposed in the film, A passage disposed inside the base material through which a refrigerant flows, and a sensor inserted into the base material to detect the temperature of the base material, from the sensor when a predetermined electric power is supplied to the heater A plasma processing apparatus for detecting an abnormality of the sensor based on a temporal change in output. The plasma processing apparatus according to claim 1,
The plasma processing apparatus, wherein the sensor has its tip pressed against a surface formed inside the substrate. The plasma processing apparatus according to claim 1,
The plasma processing apparatus according to claim 1, wherein a tip of the sensor is located on a surface between the passage and a surface on which the dielectric film is disposed. The plasma processing apparatus according to claim 1,
An abnormality of the sensor is detected based on a change with time of a time constant calculated based on a change with time of an output from the sensor when a predetermined power is supplied to a heater.   A metal base material, a dielectric film disposed on the top surface of the base material on which the sample is placed, a film-like heater disposed in the film, and a base material disposed in the base material A sensor abnormality detection method for detecting an abnormality of the sensor in a sample mounting table including a passage through which a refrigerant flows and a sensor inserted into the substrate to detect the temperature of the substrate, Based on the change over time of the output from the sensor when a predetermined power is supplied to the heater and the change over time, the change over time of the time constant specific to the contact portion between the base material part and the temperature sensor is acquired, and the sensor An abnormality detection method for a sensor, characterized by detecting an abnormality in the sensor.

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