JP6581387B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

The present invention relates to a plasma processing apparatus typified by CVD and dry etching used for manufacturing semiconductors and flat panel displays, and a processing method thereof, and more particularly to performance stability of a process using the plasma processing apparatus.

In the plasma etching process in the manufacturing process of semiconductor devices, the temperature of the processing chamber structure including the processing chamber wall and the substrate to be processed is maintained in order to keep the etching rate, selectivity, shape controllability, etc. constant in the processing of a plurality of wafers. A plasma processing apparatus having a mechanism for keeping it constant is used.

  For example, a method for keeping the temperature of the substrate to be processed constant by circulating a temperature control fluid inside a sample stage for fixing the substrate to be processed in the processing chamber, and the temperature of the substrate to be processed by embedding a heater and a refrigerant pipe inside. There is known a method of keeping the temperature constant, or a method of keeping the temperature of the processing chamber constant by heating the wall surface of the processing chamber from the atmosphere with a heater.

  Further, in order to improve the response to the temperature rise of the components in the plasma processing chamber due to heat input from different plasmas in each plasma processing condition, Patent Document 1 describes that the lower electrode close to the plasma temperature directly by a thermocouple embedded in the lower electrode. A semiconductor manufacturing apparatus that measures temperature and controls fluid temperatures of a plurality of circulators including those having a small heat capacity due to a change in temperature is disclosed.

JP 2001-39883 A

However, even when the temperature control method disclosed in Patent Document 1 is used, when a plurality of wafers are processed, variations in the etching shape between the wafers to be processed exceeding the allowable range occur. The main factor is the influence from the part where the temperature is not controlled as shown below.

  In general, including the semiconductor manufacturing apparatus described in Patent Document 1, in order to perform temperature control, it is kept at a constant temperature by controlling the amount of heat flowing in and out so as to keep the measured value from the temperature sensor constant. There are many parts that cannot be measured by the temperature sensor. In the case of plasma processing equipment, the part exposed to the plasma is heated suddenly, resulting in a non-uniform temperature distribution, and the measurement site by the temperature sensor is maintained at a constant temperature. Then, the situation where the temperature is not controlled constant occurs.

  Further, when there are many portions where the temperature is not controlled, there arises a problem that the etching rate, the selection ratio, the shape control performance, etc. cannot be kept constant for the processing of a plurality of wafers.

  In view of the above-described problems, the present invention provides a plasma processing apparatus and a plasma processing method that can suppress a change over time in a plasma processing result in a plasma processing apparatus and a plasma processing method that perform plasma processing while controlling temperature.

In the present invention, a processing chamber in which a sample is plasma-processed using plasma, a high-frequency power source for supplying high-frequency power for generating the plasma, a temperature sensor and a heater are disposed inside, and the sample is mounted In a plasma processing apparatus comprising a sample stage, the plasma processing apparatus further comprises a control device for determining the start of the plasma processing based on the value of the temperature sensor and the output value of the heater, the control device having an output value of the heater When the value is within a predetermined range, the plasma processing is started, and when the output value of the heater is not a value within the predetermined range, after performing a temperature raising process for raising the temperature of the processing chamber, The start of the plasma processing is determined based on the value of the temperature sensor and the output value of the heater .

Further, the present invention provides a plasma processing method in which a sample placed on a sample stage in which a temperature sensor and a heater are disposed is subjected to plasma processing in a processing chamber , and the output value of the heater is a value within a predetermined range. In some cases, the plasma processing is started, and when the output value of the heater is not within the predetermined range, the temperature sensor is heated and the temperature of the processing chamber is increased. The start of the plasma processing is determined based on the output value.

The present invention can suppress changes in plasma processing results over time in a plasma processing apparatus and a plasma processing method that perform plasma processing while controlling temperature.

1 is a longitudinal sectional view of a microwave ECR etching apparatus according to the present invention. It is a figure which shows the processing flow which concerns on this invention. It is a figure which shows the relationship between a wafer process number and a heater output value, and the relationship between a wafer process number and an etching amount. It is a conceptual diagram which shows the difference in the magnitude | size of a heat flux when a temperature gradient is spatially different. It is a figure which shows the output value 502 of the heater in the cleaning immediately before wafer processing after temperature adjustment implementation. It is a figure which shows the change rate of the etching amount immediately after a process start and after 25 sheets continuous processing. It is a figure which shows the processing flow for correct | amending the gas flow rate at the time of wafer processing, a temperature setting value, etc. according to the heater output value of the location in which the temperature sensor was installed. It is a figure which shows the processing flow for implementing temperature adjustment beforehand so that the heater output value of the location in which the temperature sensor was installed in the tolerance | permissible_range before processing a wafer.

First, FIG. 1 shows a cross-sectional view of a plasma processing apparatus according to the present invention. This plasma processing apparatus is an Electron Cyclotron Resonance (hereinafter referred to as ECR) type plasma etching apparatus that performs etching using electron cyclotron resonance. A shower plate 102 (for example, made of quartz or yttria) and a dielectric window 103 (for example, made of quartz) for introducing an etching gas into the vacuum container 101 and a dielectric window 103 (for example, made of quartz) are installed and sealed on the upper part of the vacuum container 101 whose upper part is opened. Thus, the processing chamber 104 is formed.

  A heater 105 is installed outside the vacuum vessel 101 and is connected to a heater controller 106. A temperature sensor 107 is installed in the vacuum vessel 101, and the signal is transmitted to the heater controller 106, and the output of the heater 105 is controlled so that the inner wall of the vacuum vessel 101 reaches a desired temperature. The shower plate 102 is connected to a gas supply device 108 for supplying an etching gas. In addition, a vacuum exhaust device (not shown) is connected to the vacuum vessel 101 via a vacuum exhaust port 109.

  In order to transmit high-frequency power for generating plasma to the processing chamber 104, a waveguide 110 that transmits electromagnetic waves is provided above the dielectric window 103. The electromagnetic wave transmitted to the waveguide 110 is oscillated from the electromagnetic wave generating power supply 111. The frequency of the electromagnetic wave is not particularly limited, but a microwave of 2.45 GHz is used in this embodiment. A magnetic field generating coil 112 for forming a magnetic field is provided on the outer periphery of the processing chamber 104, and electromagnetic waves oscillated from the electromagnetic wave generating power source 111 are generated in the processing chamber 104 by interaction with the formed magnetic field. Generate plasma.

  A wafer mounting electrode 113 is provided below the vacuum vessel 101 so as to face the shower plate 102. The wafer mounting electrode 113 has an electrode surface covered with a sprayed film (not shown), and is connected to a DC power source 115 via a high frequency filter 114. Further, a high frequency power source 117 is connected to the wafer mounting electrode 113 via a matching circuit 116.

  Further, the wafer mounting electrode 113 has a refrigerant flow path 118, is connected to a temperature controller 119, has a heater 120, and is connected to a heater controller 121. Further, a temperature sensor 122 is installed on the wafer mounting electrode 113, and its signal is transmitted to the heater controller 121 to control the output of the heater 120 and the temperature of the refrigerant so that the wafer 123 temperature becomes a desired temperature. The set temperature of the device 119 is controlled.

  The wafer 123 transferred into the processing chamber 104 is adsorbed and temperature-adjusted on the wafer mounting electrode 113 by the electrostatic force of the DC voltage applied from the DC power supply 115, and a desired etching gas is supplied by the gas supply device 108. After that, plasma is generated in the processing chamber 104 with a predetermined pressure in the vacuum vessel 101. By supplying high frequency power from a high frequency power source 117 connected to the wafer mounting electrode 113, ions are drawn from the plasma into the wafer, and the wafer 123 is etched.

  In this embodiment, the inner wall temperature of the vacuum vessel 101 can be controlled to a desired temperature by the heater 105, and the temperature of the wafer mounting electrode 113 can be controlled to a desired temperature by the heater 120 and the temperature controller 119. However, the heater controller 106, the heater controller 121, and the temperature controller 119 are connected to an etching control unit 124 that is a control device that controls the entire etching apparatus. The etching control unit 124 processes the temperature signal measured by the temperature sensor 107 that monitors the temperature of the inner wall of the vacuum vessel 101 and the temperature sensor 122 that monitors the temperature of the electrode 113 for placing the wafer, and is connected to the temperature sensor 107. The heater controller 106, the heater controller 121 connected to the temperature sensor 122, and the temperature controller 119 are controlled.

  In such an etching apparatus, the present invention includes a heater output monitoring unit 125. The heater output monitoring unit 125 is connected to the heater 120 to detect the heater 120 output value, and monitors whether or not it falls within a preset allowable range based on the detected heater output value. Further, the heater output monitoring unit 125 is connected to the etching control unit 124 to control the following processing.

  Next, a processing flow using an etching apparatus provided with the heater output monitoring unit of the present invention will be described with reference to FIG. First, in step 201, the output value of the heater 120 is measured. Next, in step 202, it is determined whether or not the output value of the heater 120 is within a preset allowable range. If within the allowable range, wafer processing is executed in step 203. If it is out of the allowable range, temperature adjustment is executed in step 204, and after temperature adjustment, the output value of the heater 120 is measured in step 201, and it is determined in step 202 whether it is within the allowable range.

  In step 205, it is determined whether there are other wafers to be processed, and the above-described processing flow is repeatedly executed until there are no more wafers to be processed. When there are no more wafers to be processed, the processing flow ends. By applying this processing flow, it was possible to suppress a change in etching performance with time during continuous processing of the processing target wafer. The model for suppressing the change in etching performance with time is considered as follows.

  FIG. 3 shows a transition 301 of the output value of the heater 120 built in the wafer mounting electrode 113 with respect to the number of processed wafers. FIG. 3 shows the transition of the etching amount of the tungsten film as 302 with respect to the number of processed wafers. It can be seen from FIG. 3 that there is a correlation between the transition until the etching amount transition 302 is stabilized and the transition until the transition 301 of the heater 120 is stabilized. This correlation is considered as follows.

  FIG. 4 is a conceptual diagram for explaining the difference in the magnitude of the heat flux when the temperature gradient is spatially different. 4A shows a case where the temperature difference between the temperature sensor installation location and the temperature sensor installation location is large, and FIG. 4B shows the temperature sensor installation location and the temperature sensor installation location. The case where the temperature difference with the outside of is small is shown.

  4 (a) and 4 (b), the horizontal axis represents the coordinate axis, and A is the location where the temperature sensor is installed. For example, the attachment location of the temperature sensor 122 attached to the wafer mounting electrode 113 is shown. B is a location where temperature measurement is not possible due to the distance from the temperature sensor 122 or the temperature sensor 107. For example, the inner wall of the processing chamber 104 in the vicinity of the wafer mounting electrode 113 is shown. The vertical axes in FIGS. 4A and 4B indicate the temperatures at the respective locations, and it is assumed that A, which is the location where the temperature sensor is installed, is temperature controlled to be the set temperature.

  It is generally known that heat flux is proportional to the temperature gradient. When temperature adjustment is performed by a heater, the heater output value is large in order to compensate for heat flowing out to the outside in the case of FIG. 4A, and the heater output value is also small in the case of FIG. 4B. In other words, the heater output value also changes as the temperature difference between the location where the temperature sensor is installed and its exterior decreases, and when the temperature difference between the location where the temperature sensor is installed and its exterior becomes constant, the heater output value also becomes constant. Become.

  Therefore, it is possible to determine whether or not the external temperature is constant depending on whether or not the heater output value measured is within an allowable range in which it can be assumed that the external temperature is constant. That is, it is considered that there is a correlation between the behavior of the heater output value and the temperature distribution in the entire processing chamber. In addition, since there is a correlation between the temperature distribution in the entire processing chamber and the change in etching performance with time, the change in etching performance with time can be understood by grasping the behavior of the heater output value.

  Therefore, in the conventional temperature control that controls the amount of heat input and outflow so as to keep the measurement value from the temperature sensor constant, only the temperature control of the part measured by the temperature sensor can be performed. By using the plasma processing apparatus provided, it is possible to reduce the places where the temperature is not controlled, and to keep the etching rate, the selection ratio, the shape control performance, etc. constant over the processing of a plurality of wafers.

  Next, the setting method of the tolerance | permissible_range of a present Example is demonstrated. First, the transition of the output value of the heater 120 built in the wafer mounting electrode 113 during a predetermined operation when a plurality of wafers are processed until the etching performance becomes constant is recorded. Here, the predetermined operation refers to an operation that can always measure the output value of the heater 120 under the same condition before wafer processing. In this embodiment, the time average value in the pre-in-situ cleaning is used. The cleaning immediately before wafer processing is a cleaning process by plasma discharge for restoring and maintaining the state inside the processing chamber 104 to a certain level immediately before each wafer processing. The predetermined operation is not limited to the processing operation such as cleaning immediately before the wafer processing, but may be a case where the processing chamber 104 is in a semi-idling state at the time of wafer replacement.

  As shown in the transition 301 of the output value of the heater 120 in FIG. 3, it can be seen that the output value of the heater 120 shows a decreasing tendency until the number of wafers processed reaches about 50, and thereafter varies in the vicinity of about 743 W. This shows the same behavior as the etching amount transition 302. Therefore, in this embodiment, if the number of processed wafers is 50 or more, the heater 120 output value transition 301 and the etching amount transition 302 are both considered to be stable, and the output of the heater 120 having 50 or more wafers processed is output. The average value and standard deviation of the values were calculated, and the allowable range 303 of the output value of the heater 120 was (average value) ± (standard deviation) × 1.5.

  As shown in the processing flow of FIG. 2, it is determined whether the wafer 123 is processed or the temperature is adjusted depending on whether the output value of the heater 120 is within the allowable range 303 of the output value of the heater 120.

  FIG. 5 shows a value 501 when the output value of the heater 120 is measured according to the flow shown in FIG. Since the output value of the heater 120 at this time was out of the allowable range 303 of the output value of the heater 120, the temperature was adjusted. The temperature adjustment at this time was performed by temperature rising discharge. The temperature rising discharge refers to plasma discharge for increasing the temperature inside the processing chamber 104. As discharge conditions, 50 ml / min argon (Ar) gas, which is a low-reactivity gas, was used, the treatment pressure was 0.5 Pa, the microwave power was 1200 W, and the wafer bias was 0 W.

  In this embodiment, argon (Ar) gas is used as a low-reactivity gas, but rare gas such as helium (He) gas or neon (Ne) gas, nitrogen (N2) gas, or oxygen (O2) gas is used. May be. In this example, the temperature rising discharge time and the dependency of the output value of the heater 120 were acquired in advance, and the temperature rising discharge time required for temperature adjustment was set according to the output value of the heater 120. Depending on the output value of the heater 120, the heating discharge time may be automatically set using another method.

  FIG. 5 shows an output value 502 of the heater 120 in pre-in-situ cleaning after wafer temperature adjustment. Since the output value 502 of the heater 120 entered the allowable range 303, wafer processing was performed. FIG. 6 shows a comparison between the results of the prior art and the results of the present invention regarding the amount of change in the etching amount. FIG. 6 shows the change rate of the etching amount immediately after the start of the conventional processing and after the 25 consecutive processing, and the change rate of the etching amount immediately after the start of the processing and after the 25 consecutive processing in the present invention. By applying the processing flow shown in FIG. 2 according to the present invention, the rate of change could be reduced to about 1/10.

  In the present embodiment, the heater output monitoring unit 125 is connected to the heater 120, but the present invention is also effective when the connected heater is other than the heater 120 alone. For example, the present invention may be applied to a heater or the like inside the temperature controller 119 connected to the wafer mounting electrode 113. Since the temperature distribution in the processing chamber can be made uniform as the number of application locations of the present invention increases, it is desirable from the viewpoint of temperature control to increase the number of application locations of the present invention as much as possible.

  Furthermore, the temperature adjustment method may be optimized by deriving a portion where the temperature adjustment is necessary for the entire apparatus from each heater output value at the application point of the present invention. As a result, the temperature can be adjusted more efficiently than at each location, leading to an improvement in throughput. Further, in order to efficiently control the temperature, it is effective to perform temperature adjustment in advance at a location where the specific heat is large, such as a shower plate or a dielectric window. Thereby, the time until the heater output value is stabilized can be shortened, leading to an improvement in throughput.

  In the present embodiment, the temperature adjustment was performed by temperature rising discharge, but the present invention is also effective in cases other than temperature rising discharge. For example, the temperature may be adjusted by temporarily increasing / decreasing the heater output value. Or you may adjust the discharge conditions in temperature rising discharge according to the heater output value of each temperature sensor installation location so that it may become desired temperature distribution. Furthermore, instead of adjusting the temperature before wafer processing, a method for optimizing the processing conditions such as the gas flow rate and temperature set value during wafer processing according to the heater output value at the location where the temperature sensor is installed as shown in the processing flow of FIG. It may be used.

  In the processing flow of FIG. 7, first, in step 701, the output value of the heater 120 is measured. Next, in step 702, it is determined whether or not the output value of the heater 120 is within a preset allowable range. If within the allowable range, wafer processing is executed in step 703. If it is outside the allowable range, the parameters of the wafer processing conditions are corrected using APC, which is a control that suppresses fluctuations in plasma processing by feedback control or feedforward control in step 704, and the wafer processing is executed in step 703. .

  In step 705, it is determined whether or not there is a wafer to be processed, and the above-described flow is repeatedly executed until there is no wafer to be processed. When there are no more wafers to be processed, the processing flow ends. The processing flow shown in FIG. 2 or the processing flow shown in FIG. 7 can be used alone or in combination. By implementing the present invention, the temperature adjustment time can be shortened and the throughput can be improved.

  In this embodiment, the processing flow is just before the wafer processing, but the present invention is also effective in cases other than just before the wafer processing. For example, as shown in the processing flow of FIG. 8, temperature adjustment may be performed in advance before processing is performed so that the heater output value at the temperature sensor installation location is within the allowable range.

  In the processing flow of FIG. 8, first, in step 801, the output value of the heater 120 is measured. Next, in step 802, it is determined whether or not the output value of the heater 120 is within a preset allowable range. If it is within the permissible range, the processing flow is terminated. If it is outside the permissible range, temperature adjustment is executed at step 803. When the temperature adjustment is executed, the output value of the heater 120 is measured in step 801, and it is determined in step 802 whether it is within the preset allowable range. This processing flow is executed at regular intervals. Applying the processing flow shown in FIG. 8 is desirable from the viewpoint of throughput because the temperature adjustment time during operation of the apparatus is shortened, and is also desirable from the viewpoint of improving the apparatus life because it is not necessary to raise the apparatus temperature rapidly.

  In the present embodiment, the microwave ECR plasma etching apparatus has been described. However, the same effects as in the present embodiment can be obtained in plasma processing apparatuses using other plasma generation methods such as capacitively coupled plasma and inductively coupled plasma. It is done.

  In addition, the present invention can achieve the same effect when the heater is not a heating device but a cooling device. That is, it is considered that the mechanism equivalent to the technical idea of the present invention is established even when the temperature sensor is installed at a lower temperature than the outside, contrary to this embodiment. In this case, inflow of heat from the outside occurs, so that the amount of heat corresponding to the amount of inflow of heat must be released to the outside in order to make the temperature distribution uniform.

  For this reason, a cooling device such as a Peltier element must be present at the location where the temperature sensor is installed, but it can be considered that the output value of this cooling device corresponds to the heater output value in this embodiment. Therefore, even when the temperature of the place where the temperature sensor is installed is lower than the outside, it is considered that the mechanism equivalent to the present invention is established.

  As described above in the present embodiment, the present invention measures a heater output value in a plasma processing apparatus including a control device that performs temperature control with a temperature sensor and a heater, and the measured heater output value is preset. It is characterized in that the next operation is controlled depending on whether or not it falls within the allowable range.

DESCRIPTION OF SYMBOLS 101 ... Vacuum container, 102 ... Shower plate, 103 ... Dielectric window, 104 ... Processing chamber, 105 ... Heater, 106 ... Heater controller, 107 ... Temperature sensor, 108 ... Gas supply device, 109 ... Vacuum exhaust port, 110 ... Waveguide, 111 ... Electromagnetic wave generating power source, 112 ... Magnetic field generating coil, 113 ... Wafer mounting electrode, 114 ... High frequency filter, 115 ... DC power source, 116 ... Matching circuit, 117 ... High frequency power source, 118 ... Flow for refrigerant Path, 119 ... temperature controller, 120 ... heater, 121 ... heater controller, 122 ... temperature sensor, 123 ... wafer, 124 ... etching control unit, 125 ... heater output monitoring unit

Claims (5)

A processing chamber in which a sample is plasma-processed using plasma, a high-frequency power source for supplying high-frequency power for generating the plasma, a sample stage on which a temperature sensor and a heater are arranged and the sample is placed In the plasma processing apparatus provided,
Further comprising a control device for determining the start of the plasma processing based on the value of the temperature sensor and the output value of the heater;
The control device starts the plasma processing when the output value of the heater is within a predetermined range, and raises the processing chamber when the output value of the heater is not within the predetermined range. A plasma processing apparatus, wherein after starting a temperature raising process for heating, the start of the plasma processing is determined based on a value of the temperature sensor and an output value of the heater. A processing chamber in which a sample is plasma-processed using plasma, a high-frequency power source for supplying high-frequency power for generating the plasma, a sample stage on which a temperature sensor and a heater are arranged and the sample is placed In the plasma processing apparatus provided,
Further comprising a control device for determining the start of the plasma processing based on the value of the temperature sensor and the output value of the heater;
The control device starts the plasma processing when the output value of the heater is a value within a predetermined range, and when the output value of the heater is not a value within the predetermined range, a desired plasma processing result The plasma processing condition parameters are corrected by feedback control or feedforward control so that the plasma processing conditions are corrected, and after correcting the parameters, the plasma processing is started under the plasma processing conditions with the corrected parameters. Processing equipment. The plasma processing apparatus according to claim 1,
The plasma processing apparatus, wherein the temperature raising process is a plasma process. In a plasma processing method of performing plasma processing in a processing chamber on a sample placed on a sample stage in which a temperature sensor and a heater are arranged,
When the output value of the heater is a value within a predetermined range, start the plasma treatment,
If the output value of the heater is not within the predetermined range, after performing a temperature raising process for raising the temperature of the processing chamber, the plasma treatment is performed based on the value of the temperature sensor and the output value of the heater. A plasma processing method characterized by determining start. In a plasma processing method for plasma processing a sample placed on a sample stage in which a temperature sensor and a heater are disposed,
When the output value of the heater is a value within a predetermined range, start the plasma treatment,
If the output value of the heater is not within the predetermined range, the parameters of the plasma processing conditions are corrected by feedback control or feedforward control so that a desired plasma processing result is obtained, and then the parameters are corrected. The plasma processing method starts plasma processing under plasma processing conditions in which the parameters are corrected.

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