JP2013214584A - Plasma processing apparatus and plasma processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high throughput plasma processing method which improves efficiency of plasma processing while ensuring long-term stability of the plasma processing.SOLUTION: A plasma processing method comprises: measuring at a plasma processing apparatus by a current/voltage probe 113, a current flowing into or a voltage applied to plasma from a high-frequency power source 111 via a substrate electrode 106; calculating from impedance obtained by the current/voltage probe 113, before introducing a wafer 109 which is a treatment material to a processing chamber 101, a thickness of a coating film formed in the processing chamber 101 after cleaning by plasma; and setting time for formation processing of the coating film at time capable of obtaining an intended thickness of the coating film which is calculated on the basis of obtained thickness of the coating film thereby to automatically optimize the thickness of the coating film according to processing conditions.

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method, and more particularly to a method for controlling plasma used for surface processing of a semiconductor wafer or the like.

With the recent high integration of LSI, critical accuracy required for etching (Critical
Dimension: hereinafter referred to as CD. ) Is growing more and more. In semiconductor manufacturing factories, it is important to ensure CD stability in addition to CD controllability.

  One of the causes of CD fluctuation in the etching process is a change in the state of the inner wall of the chamber due to a reaction product or the like generated during the processing. Various techniques have been studied as a method for suppressing a reduction in process performance caused by a change in the state of the inner wall of the chamber.

  Conventionally, cleaning using plasma has been performed for each wafer or lot for removing deposits generated due to process gas, resist, and the like in the course of process processing from the inner wall of the chamber. In addition, because deposits such as metal particles generated due to chamber members and wafers are difficult to remove sufficiently by plasma cleaning, techniques such as keeping the chamber atmosphere constant by using seasoning etc. in advance It has been known.

  In addition, as in the technique specified in Patent Document 1, each time before wafer processing, a film composed of Si, O, C, etc. is formed on the entire inner wall of the chamber, and a series of processes removed after the processing, A method of resetting the chamber inner wall state for each wafer is known.

  Various techniques have been studied as a method for evaluating the inner wall state of the chamber. For example, as shown in Patent Document 2, a method for measuring the current value or voltage value from the ground to the substrate electrode during plasma processing and quantifying the deposit on the inner wall of the chamber is shown in Patent Document 3. In this method, the deposit attached to the inner wall of the chamber is evaluated by obtaining the emission intensity of a specific wavelength by OES (Optical Emission Spectrometer).

JP 2011-192872 A US Patent Application Publication No. 2006/0065631 JP 2001-250812 A

Principles of Plasma Discharges and Materials Processing 2 Edition (2005)

  However, in the above prior art, the following points have not been sufficiently considered. In the technique specified in Patent Document 1, the determination method related to the thickness of the coating film formed on the inner wall of the processing chamber is not clear, and the film thickness is excessive as a process processing condition, particularly in the process processing in which the amount of coating film consumption is small Thus, there has been a problem that the throughput of the entire process is reduced.

  In addition, as a technique for measuring the thickness of the coating film formed on the inner wall of the chamber, the techniques specified in Patent Document 2 and Patent Document 3 can quantify the deposits in the chamber. It is not possible to quantify only the net wall coating film, except for deposits on the substrate electrode, coating film, and wall deposits. However, there is a problem that throughput is lowered in some cases.

  An object of the present invention is to provide a plasma processing apparatus and a plasma processing method with improved plasma processing efficiency and high throughput.

In order to solve the above problems, the following means were adopted. The plasma processing apparatus of the present invention includes a processing chamber for plasma processing a target object, plasma generating means for generating plasma in the processing chamber, an electrode disposed in the processing chamber for mounting the target object, In a plasma processing apparatus, comprising: a high-frequency power source for supplying high-frequency power to an electrode; and a voltage / current measuring means for measuring a high-frequency voltage applied to the electrode and a high-frequency current flowing through the electrode. Coating film thickness calculating means for determining the thickness of the film, wherein the coating film thickness calculating means coats the coating film in the processing chamber and then applies the voltage / voltage during the first plasma processing. By calculating the difference between the first impedance obtained by the current measuring means and the second impedance obtained by the voltage / current measuring means during the second plasma treatment The calculated thickness of the coating film, the second plasma treatment is characterized in that it is performed in a state of mounting the object to be processed to the electrode.
In addition, the plasma processing method of the present invention includes a cleaning process for plasma cleaning a processing chamber for plasma processing a target object and a coating film forming process for coating a coating film in the processing chamber after the stabilization process. In the plasma processing method of plasma-etching the processing body, the first impedance obtained during the first plasma processing after coating the coating film in the processing chamber under the same plasma processing conditions as the coating film forming processing And calculating the difference between the second impedance obtained during the second plasma treatment and the thickness of the coating film, and calculating the coating film forming process time. The stabilization process is performed for a time period corresponding to the desired thickness of the coating film calculated based on the thickness of the film.

  Since the present invention has the above-described configuration, it is possible to improve plasma processing efficiency and maintain high throughput plasma processing while maintaining the stability of the process processing.

It is a longitudinal cross-sectional view explaining the structure of the plasma processing apparatus which concerns on the 1st Example of this invention. It is an arithmetic circuit module schematic diagram which calculates the synthetic high frequency impedance from a substrate electrode to the earth. It is a correlation diagram which shows the thickness of the coating film of a process chamber inner wall, process performance, and its performance dispersion | variation. It is a figure which shows the equivalent circuit model from a high frequency power supply to a ground via a substrate electrode and plasma. It is the coating film thickness measurement flow of the processing chamber inner wall using a V / I probe. (Method of placing wafer on substrate electrode during film formation) It is the coating film thickness measurement flow of the processing chamber inner wall using a V / I probe. (Method of not placing wafer on substrate electrode during film formation) It is the calculation procedure of the optimal coating film thickness according to processing conditions. It is a longitudinal cross-sectional view which shows the structure of the plasma processing apparatus which concerns on the 2nd Example of this invention. It is a characteristic view which shows the relationship between the emitted light intensity of the specific wavelength at the time of plasma cleaning, and processing time. It is a coating film thickness measurement flow using plasma luminescence measurement. 1 is an overall configuration diagram of a processing apparatus according to a case where a wafer is placed on a substrate electrode during film formation in Example 1. FIG.

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

  1 to 7 show a first embodiment of the present invention. FIG. 1 shows a microwave ECR (Electron Cyclotron Resonance) plasma etching apparatus according to an embodiment of the present invention.

  In this figure, in the plasma processing apparatus which concerns on Example 1 of this invention, the substrate electrode installed in the process chamber inside, the electric field and magnetic field supply apparatus installed in the vacuum chamber exterior, and the power supply are shown typically. . Equipment and devices other than these are arranged according to required performance or specifications so as not to significantly impair the operation and effect of the invention according to this embodiment by those who have ordinary knowledge in the technical field according to this embodiment. Or it can be deleted.

  In the plasma processing apparatus shown in this figure, a disc-shaped shower plate 102 having a plurality of through holes for introducing a reactive gas and a dielectric window above a processing chamber 101 having a cylindrical shape with an open top. 103 (made of quartz or the like) is installed, and the processing chamber 101 is hermetically sealed by the dielectric window 103. The flow rate of the reactive gas is controlled by the gas supply device 120 and is supplied to the processing chamber 101 via the shower plate 102.

  A solenoid coil 108 that forms a magnetic field in the processing chamber 101 is disposed on the outer periphery and above the processing chamber 101, and the magnetic field in the processing chamber 101 can be controlled by the current of the solenoid coil 108. In addition, a magnetron 104 that generates a microwave and a waveguide 105 that transmits the microwave are installed in an open portion at the top of the processing chamber 101, and are connected to a cylindrical space above the dielectric window 103. .

  The electromagnetic wave used in the present embodiment is a 2.45 GHz microwave generated by the magnetron 104, but this is not particularly limited by the effect and action. The microwave oscillated by the magnetron 104 propagates through the waveguide 105, passes through the dielectric window 103, and is introduced into the processing chamber 101. A vacuum exhaust pump (not shown) is connected to the lower portion of the processing chamber 101 through a vacuum exhaust pipe 107 so that the processing chamber 101 can be evacuated. In addition, the substrate electrode 106 disposed below the processing chamber 101 so as to face the shower plate 102 above the processing chamber 101 is covered with a dielectric film (not shown).

  The wafer 109 is transferred into the processing chamber 101 by a transfer device such as a robot arm (not shown). Then, it is placed on the substrate electrode 106 and is electrostatically attracted by a DC voltage applied from the DC power source 110 to an electrode (not shown) inside the substrate electrode 106. A high frequency power source 111 connected to the substrate electrode 106 can apply a high frequency via a high frequency matching unit 112. A cylindrical earth 121 connected to the ground is installed on the side wall of the processing chamber 101, and the high-frequency current applied to the substrate electrode 106 by the high-frequency power supply 111 flows to the earth 121 through plasma. A cylindrical inner cylinder 122 (made of quartz) is installed above the ground and insulated.

  Etching (hereinafter referred to as “process processing”) in the plasma processing apparatus is started in the following flow. A process gas is introduced into the processing chamber 101 from a gas supply device, and a desired pressure is controlled. The processing gas is excited by an electromagnetic wave oscillated from the magnetron 104 and supplied into the processing chamber 101 and electron cyclotron resonance by a magnetic field formed in the processing chamber 101, and plasma is generated in the processing chamber 101. High frequency power is applied from a high frequency power supply 111 connected to the substrate electrode 106, ions are drawn into the upper surface of the wafer 109 placed on the substrate electrode 106, and an etching process is performed.

  Further, when performing the above process, a coating film forming process is performed for each wafer process. Here, the coating film forming process is arranged in the processing chamber 101 (for example, on the substrate electrode 106 or in the processing chamber 101) in order to suppress the influence on the process performance caused by the state change of the inner wall of the processing chamber 101. In the state where the wafer 109 is not placed on the substrate electrode 106, the film (hereinafter referred to as “coating film”) is coated so as to cover the deposit on the inner wall of the processing chamber 101. ). In this coating film forming process, plasma is generated in the same process as the above process, but application of high frequency power from the high frequency power supply 111 is not necessarily required. The coating film forming process includes the following steps.

  That is, there are four steps: 1) plasma cleaning step, 2) process treatment, 3) coating film forming step, and 4) plasma treatment step on the surface of the coating film. Plasma cleaning is performed in a state where the wafer 109 is not placed. Thereafter, the wafer 109 is loaded onto the substrate electrode 106 and is unloaded after being processed. Thereafter, the coating film forming step and the plasma processing of the coating film surface are performed without placing the wafer 109 thereon.

The plasma cleaning step is a step in which the inner wall of the processing chamber 101 takes into account the state where there are deposits generated during the etching process or residues such as a coating film formed by the coating film forming process, and these are removed by plasma. is there. As the cleaning gas, for example, a mixed gas of a diluted gas such as NF ₃ and Ar or a mixed gas of a diluted gas such as SF ₆ and Ar is used.

  In the coating film forming step, the entire inside of the processing chamber 101 including the substrate electrode 106 is coated with a member on the inner wall of the processing chamber 101 or a deposit such as a reaction product that cannot be completely removed by plasma cleaning. This is a step of forming a film. This coating film is a coating film containing Si, a film containing Si and oxygen (O), a film containing Si and carbon (C), or a film containing Si and nitrogen (N). Either.

Examples of the gas for forming these coating films include a film containing Si and oxygen (O), a mixed gas of SiCl ₄ and O ₂ , and a film containing Si and carbon (C). A mixed gas of SiCl ₄ and CH ₄ , and a film containing Si and nitrogen (N), a mixed gas of SiCl ₄ and N ₂ is used, and they can be diluted with a rare gas such as Ar. Good. A coating film is formed by using these gases and generating plasma. In this embodiment, a case where a film mainly composed of SiO ₂ is formed by a mixed gas of SiCl ₄ and O ₂ will be described.

The plasma treatment step on the surface of the coating film is a step of removing irregularities generated on the surface of the coating film formed in the processing chamber 101. This is because when the wafer 109 placed on the substrate electrode 106 on which the coating film is formed is attracted by the electrostatic force generated by the DC voltage applied to the substrate electrode 106 from the DC power supply 110, the coating is performed. The unevenness on the surface of the film may cause foreign matter, and the plasma treatment can reduce the unevenness on the surface of the coating film and suppress foreign matter. For example, it is effective to use a fluorine-based gas such as SF ₆ as the gas.

  In the present embodiment, in addition to the apparatus as described above, the following is mounted. That is, a voltage / current probe (hereinafter referred to as a V / I probe) 113 capable of measuring a high-frequency current value or a voltage value is connected between the high-frequency power source 111 and the substrate electrode 106, and the impedance is calculated from the measured value. Further, an arithmetic circuit module 114 capable of performing a desired calculation based on the result and a display unit 115 for displaying the calculation result are connected. The V / I probe 113 can also measure a high-frequency voltage waveform and a high-frequency current waveform applied to the substrate electrode 106, and can measure each amplitude and phase difference.

  FIG. 2 is a schematic diagram of the arithmetic circuit module 114 that calculates the synthetic high-frequency impedance from the substrate electrode 106 to the ground in the plasma processing apparatus according to the embodiment shown in FIG. In the arithmetic circuit module 114, the synthetic high frequency impedance is calculated from the current value or voltage value measured by the V / I probe 113, and the coating film formed by the coating film forming process on the inner wall of the processing chamber 101 is calculated. The thickness is calculated. The arithmetic circuit module 114 stores a storage unit 130 that can temporarily store input measurement values, a calculation unit 131 that can perform a desired calculation based on the measurement values, and reference data of parameters necessary for the calculation. The database unit 132 is configured. The calculation result is output to the display unit 115 or the parameter control unit 116.

  All of the above configurations are connected to the parameter control unit 116, and their timing and operation amount are controlled so as to operate in an appropriate sequence.

  FIG. 3 shows the relationship between the thickness of the coating film formed by the coating film forming process, process performance (for example, etching rate), and process performance variation. The process performance includes the etching rate (rate) when the wafer 109 is processed in a single shot, and the overall rate variation in each wafer process that changes over time when several tens of wafers 109 are processed continuously. Evaluation was made by measuring the etching rate variation (ΔER), which is the width.

The vertical axis in FIG. 3 shows the etching rate (rate) and the etching rate variation (ΔER) with time, and the horizontal axis shows the coating film thickness. In this experiment, an oxide film wafer 109 was used as a material to be processed. The process gas was a mixed gas of CF ₄ and a rare gas such as CHF ₃ , CH ₄ , and Ar.

In the figure, the thickness of the coating film in the above experimental results is calculated by measuring the film formation rate (the rate at which the coating film is formed) in advance, and the desired film thickness is determined by the film formation time. Is controlled by. As an example of a method for evaluating the film formation rate, a substrate on which the same material (quartz, Al ₂ O ₃ , Y ₂ O _3, etc.) as the inner wall of the processing chamber 101 is formed is attached to the inner wall of the processing chamber 101. There is a method in which after the coating film forming process is performed, the substrate is removed from the inner wall of the processing chamber 101 and the thickness of the film formed on the substrate is measured by an optical film thickness measuring instrument or the like.
In general, the factor that the process performance (etching rate) fluctuates after continuously processing several tens of wafers 109 is that the reaction product caused by the material to be etched and the process gas deposited on the inner wall of the processing chamber 101 is plasma. It is because it affects.

  As shown in FIG. 3, the influence on the process performance due to the change in the surface state of the inner wall of the processing chamber 101 is reduced by forming a coating film on the inner wall of the processing chamber 101 for each wafer and increasing the film thickness. I understand that I can do it. However, the deposition rate of the coating film to be formed has a distribution at the location of the inner wall of the processing chamber 101, and it is difficult to form the coating film on the inner wall without leakage from the viewpoint of increasing the throughput.

  Further, not all inner walls of the processing chamber 101 affect the process performance. That is, a necessary and sufficient coating film may be formed in a place where the influence on the process performance due to the change in the inner wall state of the processing chamber 101 is large. In the present embodiment, the locations that have a large influence on the process performance due to the change in the inner wall state of the processing chamber 101 are mainly the quartz shower plate 102 and the inner cylinder 122 located above the substrate electrode 106, and the processing chamber. It is known from the experimental results that the ground is 121 or the like located on the side wall of 101.

  Also, in this figure, when the film thickness is greater than or equal to film thickness B, the change in the etching rate with respect to the film thickness is small, and the amount of change in the etching rate over time with respect to the film thickness (ΔER) is less than the allowable value required for process performance. ,stable. This is because the portion of the inner wall of the processing chamber 101 that affects the plasma in the coating film B or higher was covered until the end of the etching process. That is, it can be said that a coating film having a film thickness B may be formed at the start of process processing in order to suppress the variation in process performance. With the film thickness C, the variation in process performance can be reduced, but the film thickness is excessive, leading to a reduction in processing efficiency. Further, in the film thickness A, the process performance varies.

  This means that the thickness of the coating film formed on the inner wall of the processing chamber 101 is insufficient. Therefore, in order to suppress the process variation caused by the change in the surface state of the inner wall of the processing chamber 101, it is necessary to cover the inner wall of the processing chamber 101 and the location of the member having a large influence on the plasma until the end of the process processing. In the figure, it is necessary to form a film having a thickness of B or more with good reproducibility. In addition, since the distribution of the consumption amount of the coating film and the consumption amount on the inner wall of the processing chamber 101 differ depending on the process processing, it is necessary to calculate the optimal coating film B corresponding to each process processing.

  In the present embodiment, a method for measuring the thickness of the coating film on the ground 121, which is a portion having a great influence on plasma, is presented. As described in Non-Patent Document 1, generally, when high-frequency power is applied to the substrate electrode 106, the high-frequency current flows to the ground 121 via the plasma formed in the substrate electrode 106 and the processing chamber 101. A sheath is formed on the surface of the plasma and ground 121 and the substrate electrode 106 (material to be processed). When the coating film is formed on the inner wall of the processing chamber 101 as described above, the coating film on the ground 121 and the substrate electrode 106 is formed.

For example, the main component of the coating film formed by the mixed gas of SiCl ₄ and O ₂ in this embodiment is SiO ₂ , and an insulating film is formed. Further, the high frequency impedance Z of the insulating film is described by the following equation. Here, C is a capacitance, ω is an angular frequency, ε is a relative dielectric constant of the insulating film, d is a coating film thickness, and S is a coating film area formed on the inner wall of the processing chamber 101.
Z = 1 / jωC = d / jεS

  FIG. 4 shows an equivalent circuit model from the high frequency power supply 111 to the ground 121 via the substrate electrode 106 in the present embodiment. In the drawing, Zs1 and Zs2 are sheaths, Zp is plasma, and Zc1 and Zc2 are high-frequency impedances of the coating film formed on the inner wall of the processing chamber 101 and the substrate electrode 106. Assuming that the plasma density to be formed is constant for different coating thicknesses, when the relative dielectric constant ε and the area S of the coating film are known, the substrate electrode 106 is connected to the plasma and the ground 121. By measuring the synthetic high-frequency impedance, it is possible to measure a change in the thickness of the coating film as an impedance change.

  5 and 6 show a method for evaluating the thickness of only the coating film on the inner wall of the processing chamber 101 using the V / I probe 113 in this embodiment.

  In this embodiment, the combined high frequency impedance from the ground 121 to the substrate electrode 106 is calculated by measuring a current value or a voltage value with the V / I probe 113 connected to the high frequency power supply 111. There are a method of placing a wafer during film formation and a method of not placing a wafer.

  The former procedure is as follows. First, as shown in FIG. 5A, plasma A to which a high frequency bias is applied is generated, and the impedance 1-a in the initial state of the processing chamber 101 is measured. In the initial state of the processing chamber 101, deposits such as reaction products are present in the processing chamber 101. Therefore, there is a possibility that a coating film cannot be formed with a desired film thickness due to the influence. Therefore, in the initial state of the processing chamber 101, the impedance 1-a is measured in order to determine whether the amount of deposit on the inner wall is excessive in forming the coating film with a desired film thickness.

In the experiment, a rare gas such as Ar is used as the gas for generating the plasma A because the inner wall of the processing chamber 101 and the coating film are not etched. The high frequency bias was 10 to 50W. At this time, the value of the impedance 1-a is out of the allowable value with respect to the impedance value corresponding to the amount of deposit that can be determined that the inside of the processing chamber 101 is sufficiently cleaned and the coating film can be formed with a desired film thickness. In the case of (for example, 10% or more), the inside of the processing chamber 101 is subjected to plasma cleaning with a mixed gas of a diluent gas such as NF ₃ and Ar, or a mixed gas of a diluent gas such as SF ₆ and Ar, and impedance 1 again. -Start measurement of a. When the value of the impedance 1-a falls within the allowable value, the process proceeds to the next procedure.

Next, as shown in FIG. 5B, in order to avoid the formation of a coating film on the substrate electrode 106, the film formation wafer is transferred onto the substrate electrode, plasma B is generated, and the entire processing chamber 101 is formed. A coating film having a fixed thickness is formed on the substrate. After the coating film is formed in the processing chamber 101, the film forming wafer is removed by conveyance. Here, the plasma B is generated by a mixed gas of SiCl ₄ and O ₂ and is used as the coating film forming condition of this embodiment. Moreover, in experiment, the coating film thickness was 50-100 nm.

Then, as shown in FIG. 5C, the plasma 2-A is generated, and the impedance 2-a is measured in a state where the initial coating film is formed. Further, as shown in FIG. 5D, the process wafer is transferred, and plasma C is generated to perform the process. At this time, the coating film as well as the process processing wafer is etched by the process process. Here, the process processing wafer does not need to be a wafer to be processed, and for example, a Si wafer or the like may be used. Plasma C is an actual process processing condition for which the coating film thickness should be optimized. In this experiment, the process gas was a mixed gas of CF ₄ , CHF ₃ , CH ₄ , Ar, etc., and an experiment was performed by applying a high frequency bias to the wafer.

Finally, as shown in FIG. 5E, plasma A to which a high-frequency bias is applied is generated, and impedance 3-a in a state where the coating film is etched by the process is measured. After the measurement of the impedance 3-a, in order to remove the coating film remaining in the processing chamber 101, a mixed gas of NF ₃ and a diluted gas such as Ar or a mixed gas of SF ₆ and a diluted gas such as Ar is used. Then, the plasma cleaning is performed and the inner wall of the processing chamber 101 is returned to the initial state.

  Next, a procedure (not shown in FIG. 6) for not placing a wafer will be described. First, as shown in FIG. 6A, plasma A to which a high-frequency bias is applied is generated, and impedance 1-b in the initial state of the processing chamber 101 is measured. This is the same as the method for measuring the impedance 1-b. Next, as shown in FIG. 6B, plasma B is generated without placing a wafer, and a coating film having a fixed film thickness is formed in the entire processing chamber 101. Here, the plasma B is the same as the coating film forming conditions. Then, as shown in FIG. 6C, plasma A is generated, and the impedance 2-b is measured in a state where the initial coating film is formed.

  Further, as shown in FIG. 6-d, the process wafer is transferred, and plasma C to which a high frequency bias is applied is generated to perform the process. At this time, not only the process processing wafer but also the coating film on the inner wall of the processing chamber 101 is etched by the process processing. However, it is considered that the coating film on the substrate electrode 106 is protected by the process processing wafer, is not etched, and the film thickness does not change. Here, the plasma C is the same as the above-described process conditions.

Finally, as shown in FIG. 6-e, plasma A to which a high frequency bias is applied is generated, and impedance 3-b in a state where the coating film is etched by the process is measured. After the measurement of the impedance 3-b, in order to remove the coating film remaining in the processing chamber 101, plasma cleaning is performed with a mixed gas of NF ₃ or SF ₆ and a dilution gas such as Ar, and the initial processing chamber 101 It is returned to the inner wall state.

  As described above, the impedances 2-a and 3-a (or 2-b and 3-b) measured by the procedures shown in FIGS. 5 and 6 are input to the arithmetic circuit module 114 and are targeted. In the process processing, a coating film thickness necessary and sufficient for stabilizing the process performance is calculated.

  FIG. 7 schematically shows arithmetic processing performed in the arithmetic circuit module 114. The impedances 2-a and 3-a input to the arithmetic circuit module 114 are temporarily stored in the storage unit 130 first. Then, by calculating the difference between impedances 2-a and 3-a, the calculation unit 131 calculates the variable impedance (ΔZ) corresponding to the thickness consumed by the process processing in the coating film on the inner wall of the processing chamber 101. Then, the consumption amount Δd of the coating film corresponding to the calculated variable impedance is calculated.

  Here, in the above-described coating film forming process, when the coating film is formed so that the film thickness becomes Δd, the coating film disappears simultaneously with the end of the process treatment. That is, Δd can be said to be the minimum film thickness that can cover the inner wall of the processing chamber 101 until the end of the process processing, and this corresponds to the film thickness B in FIG. When the calculated Δd is equal to or smaller than a set value (for example, 50 nm to 100 nm), the film formation time is calculated by comparing with the film thickness data necessary and sufficient for suppressing the variation in process performance accumulated in the database unit 132. . The calculation result is displayed on the display unit 115 and output to the parameter control unit 116 as necessary. Further, the obtained calculation result is stored in the database unit, and is used as reference data for calculation when newly optimizing the coating film thickness corresponding to the process processing.

  However, if the calculated consumption amount Δd is equal to or greater than the installation value, the coating film consumption amount during the process process cannot be calculated correctly, and it is determined that an error has occurred. Then, the initial coating film is automatically corrected so as to have a film thickness of 1.5 times, for example, and after the plasma cleaning in the processing chamber 101, the impedance 1 is measured again and the above procedure is performed. To start the sequence. At this time, the coating film is formed with a corrected thickness. In the plasma processing apparatus according to the present embodiment, these procedures are performed automatically and can be automatically sequenced.

  As described above, the coating film thickness is measured using the V / I probe 113, and the film thickness necessary for each process is automatically calculated and controlled, thereby maintaining the stability of the process processing and maintaining the plasma. The processing efficiency is improved, and plasma processing with high throughput is possible.

  Hereinafter, the second embodiment will be described with reference to FIG. In addition to the first embodiment, the thickness of the coating film formed on the inner wall of the processing chamber 101 can be evaluated with higher accuracy by including or implementing the following apparatus. Only the differences from the first embodiment will be described below.

  In the apparatus shown in the figure, a spectrometer 118 capable of measuring light emission such as plasma is connected to the outer wall of the processing chamber 101, and the light incident from a quartz window or the like (not shown) on the inner wall of the processing chamber 101 is spectroscope. The light can be dispersed by 118 and analyzed by the light emission data analysis device 119. The light emission analysis device 119 is connected to an arithmetic circuit module 114 that can perform a desired calculation, a display unit 115 that displays a calculation result, and a parameter control unit 116.

  With the above apparatus configuration, plasma cleaning is performed on the coating film on the inner wall of the processing chamber 101 using OES or the like, and during that time, the fluctuation in emission intensity corresponding to a specific plasma (or radical) is monitored. It is possible to detect the end point of the plasma cleaning and measure the amount of the coating film consumed in the process treatment from the emission intensity and the cleaning time.

  FIG. 9 is a diagram showing the relationship between the emission intensity of a specific wavelength and the end point time during plasma cleaning in this example. The radical emission intensity resulting from the cleaning of the coating film on the vertical axis in the figure is equivalent to the surface area of the deposit deposited on the wall, and the time on the horizontal axis is equivalent to the coating film thickness. That is, when the distribution of the coating film thickness consumed in the process does not necessarily occur, the thickness of the coating film can be evaluated based on the difference from the reference data of the plasma cleaning waveform. Further, by combining with the synthetic high-frequency impedance measurement from the substrate electrode 106 to the ground 121, more accurate evaluation can be performed.

  It is also possible to perform evaluation using plasma cleaning alone. FIG. 10 shows a processing procedure for evaluating the coating film thickness consumed in the process processing by detecting the end point of the plasma cleaning in this embodiment.

First, as shown in FIG. 10A, plasma D is generated and plasma cleaning in the processing chamber 101 is performed. This is because there is a possibility that a coating film cannot be formed with a desired film thickness due to the presence of deposits such as reaction products generated in the process process in the initial state in the processing chamber 101. Consider and do. For example, as the process gas, a mixed gas of a gas such as NF ₃ or SF ₆ and a diluent gas such as Ar is used.

Next, as shown in FIG. 10B, in order to avoid the formation of a coating film on the substrate electrode 106, the film formation wafer is transferred onto the substrate electrode 106, and plasma B is generated, A coating film having a fixed film thickness is formed on the entire surface. Thereafter, the film forming wafer is removed by conveyance. Here, the plasma B is generated by a mixed gas of SiCl ₄ and O ₂ and is used as the coating film forming condition of this embodiment.

Then, as shown in FIG. 10C, plasma cleaning is performed with the plasma D being generated and the initial coating film being formed. At this time, for example, when a coating film formed of a mixed gas of SiCl ₄ and O ₂ is formed, the emission intensity of 440 nm corresponding to SiF is acquired, and the emission intensity and time until the end point detection is monitored. .

  Further, as shown in FIG. 11-d again, in order to avoid the formation of the coating film on the substrate electrode 106, the film forming wafer is transferred onto the substrate electrode 106, and plasma B is generated. A coating film having a fixed film thickness is formed on the entire surface. Further, as shown in FIG. 10E, the process wafer is transferred, and plasma C to which a high frequency bias is applied is generated to perform the process.

At this time, the coating film as well as the process processing wafer is etched by the process process. Here, the process processing wafer does not need to be a wafer to be processed, and for example, a Si wafer or the like may be used. In this experiment, the process gas was a mixed gas of CF ₄ or CHF ₃ , CH ₄ , Ar, etc., and a high frequency bias was applied to the wafer for the experiment.

  Finally, as shown in FIG. 10-f, the plasma D is generated and the remaining coating film that has been consumed by the process treatment is plasma-cleaned. The emission intensity at a specific wavelength and the end point time are monitored until the end point of plasma cleaning is detected. As in the first embodiment, the above procedure can be applied to a method in which the film forming wafer is not placed.

  The emission intensity and time (specific measurement result α) of the specific wavelength by the plasma cleaning for the coating film in the initial stage of measurement, measured by these procedures, and the emission intensity of the specific wavelength by the plasma cleaning for the coating film consumed by the process treatment The time (measurement result β) is input to the arithmetic circuit module 114, and an optimum coating film thickness is calculated in order to stabilize the process performance in the target process.

  According to the above embodiment, in the formation of the coating film for the purpose of suppressing the process variation caused by the inner wall state of the processing chamber 101, the film thickness is such that the deposit is completely covered according to the process treatment, and It is possible to individually optimize the film thickness so as to obtain the minimum film thickness, and it is possible to improve the process stability and the processing speed.

  FIG. 11 is an overall configuration diagram of a processing apparatus according to a case where a wafer is placed on the base electrode 106 during film formation according to the first embodiment. This is because a load port 1001 in which a wafer cassette A1005 in which process processing wafers used for process processing are stored is installed, an aligner 1003 installed in a fan filter unit (FFU) 1002, and a processing chamber in which plasma processing is performed. 1009, a transfer chamber 1008 for vacuum transfer of wafers to them, and a standby chamber 1004 for waiting for a film forming wafer. A film forming wafer that plays a role in preventing film formation on the substrate electrode 106 is prepared in a wafer cassette B1010 installed in a standby chamber 1004 provided in advance in the FFU 1002 or the like. With these apparatus configurations, the procedure as shown in the first embodiment can be performed fully automatically.

  In the above-described embodiment, the embodiment of the ECR plasma apparatus has been described. However, the present invention uses other plasma generation apparatuses or methods, for example, inductively coupled plasma (ICP), capacitively coupled plasma (CCP). Has the same effect.

DESCRIPTION OF SYMBOLS 101 Processing chamber 102 Shower plate 103 Dielectric window 104 Magnetron 105 Waveguide 106 Substrate electrode 107 Vacuum exhaust pipe 108 Solenoid coil 109 Wafer 110 DC power supply 111 High frequency power supply 112 High frequency matching device 113 V / I probe 114 Arithmetic circuit module 115 Display part 116 Parameter Control Unit 117 Cavity Resonance 118 Spectroscope 119 Emission Data Analysis Device 120 Gas Supply Device 121 Earth 122 Inner Tube 130 Storage Unit 131 Calculation Unit 132 Database Unit 1001 Load Port 1002 Fan Filter Unit (FFU)
1003 Aligner 1004 Waiting room 1005 Wafer cassette A
1006 Load lock chamber 1007 Unload lock chamber 1008 Transfer chamber 1009 Processing chamber 1010 Wafer cassette B

Claims (9)

A processing chamber for plasma processing the object to be processed; plasma generating means for generating plasma in the processing chamber; an electrode disposed in the processing chamber for mounting the object to be processed; and a high frequency for supplying high frequency power to the electrode In a plasma processing apparatus comprising a power source and a voltage / current measuring means for measuring a high-frequency voltage applied to the electrode and a high-frequency current flowing through the electrode,
A coating film thickness calculating means for determining the thickness of the coating film covering the processing chamber;
The coating film thickness calculation means includes a first impedance obtained by the voltage / current measurement means during the first plasma treatment after the coating film is coated in the processing chamber, and a second plasma. By calculating the difference between the second impedance obtained by the voltage / current measuring means during the process, and determining the thickness of the coating film,
The plasma processing apparatus is characterized in that the second plasma processing is performed in a state where the object to be processed is placed on the electrode. The plasma processing apparatus according to claim 1,
A plasma processing apparatus characterized in that a thickness of the coating film is obtained before plasma processing a lot containing a plurality of objects to be processed. The plasma processing apparatus according to claim 1,
A plasma processing apparatus, wherein the coating film is coated in the processing chamber using a mixed gas of SiCl ₄ gas and O ₂ gas. The plasma processing apparatus according to claim 1,
The plasma processing apparatus is characterized in that the first plasma treatment uses any one of helium gas, neon gas, argon gas, xenon gas, and krypton gas. The plasma processing apparatus according to any one of claims 1 to 4,
The plasma processing apparatus comprises a 2.45 GHz magnetron and a magnetic field generating means for generating a magnetic field in the processing chamber. In a plasma processing method for plasma-etching the object to be processed after a stabilization process having a cleaning process for plasma-cleaning a processing chamber for plasma-processing the object to be processed and a coating film forming process for coating a coating film in the processing chamber ,
The first impedance obtained during the first plasma treatment and the second plasma treatment were obtained after coating the coating film in the processing chamber under the same plasma treatment conditions as the coating film formation treatment. By calculating the difference between the second impedance and the thickness of the coating film,
The plasma treatment is characterized in that the stabilization treatment is performed by setting the time for the coating film forming treatment to a time that becomes a desired coating film thickness calculated based on the obtained thickness of the coating film. Method. The plasma processing method according to claim 6.
A plasma processing method, wherein the stabilization processing is performed for each plasma processing of the object to be processed. The plasma processing method according to claim 6.
The plasma processing method, wherein the coating film forming process is performed using a mixed gas of SiCl ₄ gas and O ₂ gas. The plasma processing method according to claim 6.
The time for the coating film forming process is adjusted according to the plasma processing conditions of the object to be processed so that the thickness of the coating film to be coated in the processing chamber becomes a desired thickness. Plasma processing method.

Images