JP2002343774A - Device and method for plasma processing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and a method for plasma processing which control the state of variance in etching speed in a wafer surface so that it does not vary from the initial state so much and can perform etching processing with good reproducibility. SOLUTION: The plasma processor generates the plasma by introducing high-frequency electric power for plasma generation into a magnetic field by a high-frequency power source 1 for plasma generation, and applies high-frequency electric power for bias generation to a wafer 8 as a substrate by a high-frequency power source 10 for bias generation to perform the plasma processing. Evaluation sample data obtained by processing a sample substrate with plasma in advance are held in a storage device 13; and an arithmetic unit 14 performs arithmetic processing according to the evaluation sample data and a controller 16 controls parameters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus and a plasma processing method used for processing a substrate such as a semiconductor substrate by generating plasma by microwaves.

[0002]

2. Description of the Related Art In a conventional plasma processing apparatus, for example, high frequency power for plasma generation is introduced into a magnetic field to generate plasma, and high frequency power for bias generation is applied to a wafer placed on a stage electrode. The surface was etched. At that time, the high-frequency power for plasma generation and the current value to the solenoid coil for forming the magnetic field were controlled so as to keep the voltage of the high-frequency power for bias generation constant. Such control is hereinafter referred to as “constant voltage control”. For example,
It is disclosed in JP-A-6-52996.

This constant voltage control suppresses fluctuations in the plasma state due to the deposition and re-dissociation of reaction products generated in the processing chamber by repeatedly processing a large number of wafers, thereby suppressing fluctuations in the etching rate. An object of the present invention is to enable fine shape control by maintaining a balance with formation of a sidewall protective film during pattern formation.

[0004]

The constant voltage control described above has a certain effect when etching a wafer surface along a pattern defined by a mask. However, when the area to be processed is large, such as when etching back the entire surface of a wafer without a pattern, only constant voltage control is required to process each wafer as many wafers are processed. There is a problem in that the variation of the etching rate depending on the position in the plane varies, and it is difficult to suppress the variation.

[0005] The reason is that merely controlling the voltage to a constant level cannot cope with a local change in the plasma state due to a reaction product attached to the surface of a structure in the processing chamber exposed to the plasma. This is because the vicinity of the outer periphery of the wafer which is close to the structure is easily affected by the reaction products attached to the structure. In particular, when a large area is to be processed, such as in an etch-back process, the effect is significant because the amount of reaction products generated is large.

Therefore, the present invention controls the variation of the etching rate in the wafer surface so as not to fluctuate as much as possible from the initial state even when processing a large area, and can perform the etching processing with good reproducibility. It is an object to provide a plasma processing apparatus and a plasma processing method.

[0007]

In order to achieve the above object, in one aspect of the plasma processing apparatus according to the present invention, a plasma is generated by introducing high frequency power for plasma generation into a magnetic field, and a bias is generated on a substrate. A plasma processing apparatus for processing the substrate by applying high-frequency power for use, wherein parameters for controlling specific parameters for plasma processing using evaluation sample data obtained by performing plasma processing on a sample substrate in advance A control unit. By adopting this configuration, since control is performed using data obtained by actually performing plasma processing on the sample substrate in advance, processing can be performed accurately and stably up to the variation of the etching rate at each point in the wafer surface. It becomes possible.

Preferably, in the above invention, the evaluation sample data relates to a peak-to-peak voltage value of the bias generating high-frequency power required for performing a plasma process in a desired state. The peak-to-peak voltage value Vpp of the bias generating high-frequency power can be monitored for change, and there is no correlation between the voltage value Vpp and the variation of the etching rate at each point in the wafer surface. It has been confirmed that there is. Therefore, by adopting the above configuration, it is possible to indirectly control the variation of the etching rate at each point in the wafer surface which is difficult to directly observe during processing.

Preferably, in the above invention, the operation parameter for controlling the specific parameter is a value of a high frequency power for plasma generation. By employing this configuration, the peak-to-peak voltage value Vpp of the high frequency power for bias generation is controlled by manipulating the value of the high frequency power for plasma generation, but the value of the high frequency power for plasma generation is directly controlled. Since the parameters are easy to operate, the operation is easy.

[0010] In the above invention, preferably, a data holding unit for holding the evaluation sample data is provided. By adopting this configuration, by holding the evaluation sample data in the data holding unit, it becomes possible to automatically refer to the evaluation sample data and proceed with the processing. Also, the evaluation sample data can be used as a database.

In the above invention, preferably, there is provided an arithmetic unit for calculating interpolative evaluation sample data required for controlling the specific parameter based on the evaluation sample data. As the evaluation sample data, only local plasma characteristics in some plasma states can be obtained. However, by employing this configuration, the arithmetic unit can perform arithmetic processing for data interpolation, and the evaluation sample data can be obtained. Can be processed into continuous data corresponding to the processing time. As a result, the control operation can be performed with higher accuracy.

In the above invention, preferably, there is provided an operation result holding unit for holding the interpolation evaluation sample data. By adopting this configuration, necessary data can be obtained only by referring to the calculation result holding unit, so that control can be performed quickly.

In the above invention, preferably, a voltage history holding unit for holding a history of voltage fluctuation of the bias generating high-frequency power is provided. By employing this configuration, the operation parameters can be quickly operated to appropriate values at the start of wafer processing.

In another aspect of the plasma processing apparatus according to the present invention, in order to achieve the above object, plasma is generated by introducing high-frequency power for plasma generation into a magnetic field, and high-frequency power for bias generation is applied to a substrate. A plasma processing apparatus for applying and processing the substrate, wherein a parameter for controlling a specific parameter for plasma processing using a relational expression between a voltage of the bias generation high-frequency power and a processing time held in advance. A control unit. By employing this configuration, necessary data can be created without performing a process evaluation operation.

In order to achieve the above object, a plasma processing method according to the present invention comprises introducing a high-frequency power for plasma generation into a magnetic field to generate plasma, applying the high-frequency power for bias generation to the substrate, and A plasma processing method for performing processing, wherein specific parameters for plasma processing are controlled using evaluation sample data obtained by performing plasma processing on a sample substrate in advance. By adopting this method, control is performed using data obtained by actually performing plasma processing on the sample substrate in advance,
Processing can be performed accurately and stably up to the variation of the etching rate at each point in the wafer surface.

In the above invention, preferably, the evaluation sample data relates to a peak-to-peak voltage value of the bias generating high-frequency power necessary for performing a plasma process in a desired state. The peak-to-peak voltage value Vpp of the bias generating high-frequency power can be monitored for change, and there is no correlation between the voltage value Vpp and the variation of the etching rate at each point in the wafer surface. It has been confirmed that there is. Therefore, by adopting the above method, it is possible to indirectly control the variation of the etching rate at each point in the wafer surface, which is difficult to directly observe during the processing.

Preferably, in the above invention, the operation parameter for controlling the specific parameter is a value of a high frequency power for plasma generation. By adopting this method, the peak-to-peak voltage value Vpp of the bias generation radio frequency power is controlled by manipulating the value of the plasma generation radio frequency power, but the value of the plasma generation radio frequency power is directly controlled. Since the parameters are easy to operate, the operation is easy.

[0018] In the above invention, it is preferable that interpolative evaluation sample data necessary for controlling the specific parameter is calculated based on the evaluation sample data, and the interpolative evaluation sample data is used to perform plasma processing. Control specific parameters. As evaluation sample data,
Although only local plasma characteristics in some plasma states can be obtained, by employing this method, the arithmetic unit can perform arithmetic processing for data interpolation, and the evaluation sample data can be processed according to the processing time. It can be processed into continuous data. As a result, the control operation can be performed with higher accuracy.

In the above invention, preferably, the history of the fluctuation of the voltage of the high frequency power for bias generation is held,
The plasma generation high frequency power is controlled using the fluctuation history. By employing this method, the operation parameters can be quickly operated to appropriate values at the start of wafer processing.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to description of an embodiment according to the present invention, characteristics of a plasma processing apparatus will be described. 2. Description of the Related Art A plasma processing apparatus is an apparatus for processing a substrate by introducing high-frequency power for plasma generation into a magnetic field to generate plasma, and applying high-frequency power for bias generation to a substrate.

The user can directly set the high-frequency power for plasma generation. By determining the high-frequency power for plasma generation, the voltage of the high-frequency power for bias generation is determined from the plasma density in the processing chamber. Therefore, as described above, conventionally, the high frequency power for plasma generation has been controlled so that the voltage of the high frequency power for bias generation becomes constant.

On the other hand, the inventors examined how the voltage value Vpp of the bias generating high-frequency power changes when the voltage value Vpp of the bias generating high-frequency power is not controlled at all. Here, the voltage value Vpp refers to a peak-to-peak voltage value. The results are shown in FIG. That is, it has been found that the voltage value Vpp of the bias generating high-frequency power monotonically increases as the number of processed wafers increases. Further, FIG.
FIG. 2 shows the result of examining the ratio of the etching rate at each point in the wafer plane at each time point (D). The vertical axis represents not the absolute value of the etching rate at each point but the relative etching rate at each point when the etching rate near the center of the wafer is set to 1. Therefore, the etching rate in the vicinity of the center of the wafer is 1 in (A) to (D), which is consistent on the graph. The etching rate in the vicinity of the center of the wafer and the etching rate in the vicinity of the outer periphery have a difference from the point of time (A) at the beginning of the processing, and show a variation as shown by the polygonal line in FIG. This is (B) →
It can be seen that as the number of processed wafers increases (C) → (D), the variation varies as indicated by arrows. Considering FIG. 1 and FIG. 2 together, it is also possible to establish a correspondence between each value of the voltage value Vpp of the high frequency power for bias generation and how the etching rate varies at each point in the wafer surface.

Further, the inventors have found that by varying the value of the high frequency power for plasma generation, the variation of the etching rate at each point in the wafer surface changes as shown in FIG. From this, it is considered that the manner in which the etching rate varies at each point in the wafer surface can be controlled by operating the high frequency power for plasma generation as an operation parameter.

On the basis of these findings, the inventors have made the present invention. Hereinafter, embodiments according to the present invention will be specifically described.

Embodiment 1 A plasma processing apparatus according to the first embodiment of the present invention will be described with reference to FIG. In this plasma processing apparatus, a high-frequency power supply for plasma generation 1 is used as a microwave oscillation source, and the microwave oscillated here is guided to a processing chamber 3 by a waveguide 2.
The processing chamber 3 is surrounded by a bell jar (vacuum container), and separates an inner vacuum portion from an outer atmosphere portion. Microwave incident from the upper part
The bell jar is formed of quartz or the like so that it can be introduced therein. A magnetic field is applied to the inside of the processing chamber 3 by the solenoid coil 4. A ground plate 5 for high frequency power supply for bias generation is provided in the processing chamber 3.
A gas for performing an etching process is supplied by a gas supply system 6. The stage electrode 9 is for mounting a wafer 8, and the wafer 8 is fixed by a jig 7. The wafer 8 may be fixed by a method such as electrostatic attraction instead of the jig 7. The stage electrode 9 is connected to a high frequency power supply 10 for bias generation. The plasma processing apparatus further includes a vacuum pump system 11 for evacuating the inside of the processing chamber 3 under reduced pressure.

In this plasma processing apparatus, as a monitor circuit, a high-frequency voltage detector 12 for bias generation, a controller 15 for controlling the entire apparatus, and a memory for storing data obtained by process evaluation using a sample substrate. The apparatus includes a storage device 13 and an arithmetic device 14 for calculating interpolation evaluation sample data based on given intermittent data and holding the result.

According to the plasma processing apparatus of the present embodiment,
In order to obtain evaluation sample data, a process called process evaluation is performed. The process evaluation is performed before starting the processing (hereinafter, referred to as an “initial state”), at several points in the middle, and after all the wafers are processed when processing a large number of wafers. Specifically, a wafer as a sample substrate is mounted on the stage electrode 9 and the output value of the plasma generating high frequency power supply 1 (plasma generating high frequency power)
Is changed in several ways, and wafer processing is performed over a certain period of time. After the wafer processing, the removal rate at each point on the wafer surface is measured to detect the etching rate at each point under each condition. FIG. 3 is an example of the data obtained as a result. As shown in FIG.
Depending on the value of the plasma-generating high-frequency power, the manner in which the etching rate varies within the wafer surface changes. From such a graph obtained at each time point other than the initial state, a value of the high frequency power for plasma generation is determined such that the variation of the etching rate in the wafer surface becomes almost equal to the initial state. Then, the actual voltage value Vpp of the high frequency power for bias generation corresponding to the value of the high frequency power for plasma generation
Ask for. The obtained value is stored in the storage device 13 as a desired voltage value Vpp corresponding to the time. Each “time point” is specified by the number of processed sheets and the discharge time.

By collecting data on the desired voltage value Vpp obtained at several points in this way, a graph as shown in FIG. 5 is obtained. This is an example of the evaluation sample data. Here, each time point is specified by the number of processed sheets.

However, even if the data is collected in this manner, this is merely an intermittent data set. Therefore, the data is further interpolated by the arithmetic unit 14 to obtain the interpolated data. Thus, continuous evaluation sample data may be used.

In the plasma processing apparatus according to the present embodiment, the evaluation sample data obtained in advance as described above is provided in the storage device 13, and by using the evaluation sample data, the bias generating high-frequency power Is controlled to match the desired voltage value Vpp. This control is performed by operating the value of the high frequency power for plasma generation as an operation parameter.

In the plasma processing apparatus according to the present embodiment, the voltage (voltage value Vpp) of the bias generating high-frequency power
Is not simply controlled to be constant, but at each time point, the information of the voltage value Vpp desirable to maintain the same state of the etching rate at each point on the wafer surface as the initial state is maintained. Since it is obtained each time from the evaluation sample data and is controlled toward a desired value, the variation of the etching rate in the wafer surface is more reliably maintained in the same state as the initial state.

In the above example, the evaluation sample data was obtained by repeatedly performing the process evaluation in advance. However, if the relational expression between the desired power value Vpp and the processing time can be predicted, the process evaluation is performed. Instead, the relational expression may be input and held, so as to substitute for the evaluation sample data. In that case, at each point in the plasma processing, the desired power value Vp
p is determined and controlled.

Embodiment 2 FIG. A plasma processing apparatus according to a second embodiment of the present invention will be described. The configuration of this plasma processing apparatus is the same as that described in the first embodiment, and therefore, description thereof will not be repeated.

The plasma processing apparatus according to the present embodiment is different from the first embodiment in the method of constructing evaluation sample data. In the first embodiment, an example in which each “time point” is specified by the number of processed sheets is described. In the present embodiment, as shown in FIG. 7, the “time point” is specified by the non-control-time voltage value Vpp0. The “non-control-time voltage value Vpp0” means that the voltage value Vpp is naturally set when the reference processing condition is set once and the plasma processing is continuously performed without control as described at the beginning of the embodiment. , The voltage value Vpp resulting from the natural increase. In this manner, even if the number of processed sheets is unknown, the non-control voltage value Vpp
0 can be actually measured and confirmed each time, so that a desired voltage value Vpp corresponding to the non-control-time voltage value Vpp0 can be obtained by referring to the evaluation sample data. However, when the plasma processing is actually repeated for a large number of wafers, the voltage value Vpp0 at the time of no control cannot be confirmed during the plasma processing, but the discharge is restarted every time a certain number of wafers are processed. At this time, by monitoring the voltage value of the high frequency power for bias generation, it is possible to know the non-control voltage value Vpp0 at that time.

Further, in the same manner as shown in FIG. 6 in the first embodiment, interpolation data is obtained by calculation by the calculation device 14, and as shown in FIG.
Continuous evaluation sample data may be used.

Further, the variation history of the voltage value Vpp is held, and the voltage value Vpp0 is monitored at the time of cleaning or seasoning performed every time a predetermined number of sheets are processed, so that a desired voltage corresponding to this is monitored. If the value of the high frequency power for plasma generation necessary for obtaining the value Vpp is predicted in advance, the control of the voltage value Vpp can be performed more quickly.

According to each of the above-described embodiments, since the variation of the etching rate at each point in the wafer surface can be kept constant, the reliability of the device manufactured from the wafer is improved. Also, even if deposits are generated in the processing chamber, the variation in the etching rate at each point on the wafer surface can be kept constant, so that the number of sheets that can be processed during one cleaning interval of the apparatus is increased. Therefore, the frequency of cleaning can be reduced, and the operation rate can be increased.

The above-described embodiment disclosed herein is illustrative in all aspects and is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes any modifications within the scope and meaning equivalent to the terms of the claims.

[0039]

According to the present invention, by employing this configuration, control is performed using data relating to the peak-to-peak voltage value Vpp of the high frequency power for bias generation obtained by actually performing plasma processing on the sample substrate in advance. Therefore, it is possible to perform the processing stably with high accuracy. Also, the voltage value V
Since there is a correlation between pp and the variation of the etching rate at each point on the wafer surface, it is difficult to indirectly control the variation of the etching rate at each point on the wafer surface which is difficult to observe directly during processing. it can.

[Brief description of the drawings]

FIG. 1 shows the number of processed wafers and the voltage value Vp when the voltage value Vpp of the bias generating high-frequency power is not controlled at all.
6 is a graph showing a relationship with p.

FIG. 2 is a graph showing a variation in an etching rate at each point on a wafer surface, which is measured at each point in time while increasing the number of processed wafers.

FIG. 3 shows the values of the high-frequency power for plasma generation,
6 is a graph showing a variation in an etching rate at each point in a wafer surface.

FIG. 4 is a conceptual diagram of a plasma processing apparatus according to Embodiment 1 of the present invention.

FIG. 5 is a graph showing a desirable voltage value Vpp at the time of each processing number obtained by process evaluation in the first embodiment based on the present invention.

FIG. 6 shows a first embodiment according to the present invention;
7 is a graph showing a state where the data shown in FIG.

FIG. 7 is a graph showing desirable voltage values Vpp at respective values of the non-control-time voltage value Vpp0 obtained by process evaluation in the second embodiment according to the present invention.

FIG. 8 shows a second embodiment according to the present invention;
7 is a graph showing a state where the data shown in FIG.

[Explanation of symbols]

1 high frequency power supply for plasma generation, 2 waveguides, 3 processing chambers, 4 solenoid coils, 5 earth plate for high frequency power supply for bias generation, 6 gas supply system, 7 jig, 8 wafer, 9 stage electrode, 10 high frequency for bias generation Power supply, 11 Vacuum pump system, 12 High frequency voltage detector for bias generation, 13 Storage device, 14 Operation device, 15
Control device.

Claims (13)

[Claims] 1. A plasma processing apparatus for generating plasma by introducing high-frequency power for plasma generation into a magnetic field and applying high-frequency power for bias generation to a substrate to process the substrate, comprising: And a parameter control unit that controls specific parameters for plasma processing using evaluation sample data obtained by performing plasma processing on the plasma processing apparatus. 2. The plasma processing apparatus according to claim 1, wherein the evaluation sample data relates to a peak-to-peak voltage value of the bias generating high-frequency power necessary for performing a plasma process in a desired state. 3. The plasma processing apparatus according to claim 1, wherein the operation parameter for controlling the specific parameter is a value of a high frequency power for plasma generation. 4. The plasma processing apparatus according to claim 1, further comprising a data holding unit that holds the evaluation sample data. 5. The plasma processing apparatus according to claim 1, further comprising an arithmetic unit for calculating interpolation evaluation sample data necessary for controlling the specific parameter based on the evaluation sample data. . 6. The plasma processing apparatus according to claim 5, further comprising a calculation result holding unit for holding said interpolation evaluation sample data. 7. A voltage history holding unit for holding a history of voltage fluctuation of the bias generating high-frequency power.
7. The plasma processing apparatus according to any one of items 1 to 6. 8. A plasma processing apparatus for processing a substrate by introducing a high frequency power for plasma generation into a magnetic field to generate a plasma, and applying a high frequency power for bias generation to the substrate to process the substrate. A plasma processing apparatus comprising: a parameter control unit configured to control a specific parameter for plasma processing using a relational expression between a voltage of the bias generation high-frequency power and a processing time. 9. A plasma processing method for introducing a high frequency power for plasma generation into a magnetic field to generate plasma, and applying a high frequency power for bias generation to the substrate to process the substrate, comprising: A plasma processing method for controlling specific parameters for plasma processing using evaluation sample data obtained by performing plasma processing on a substrate. 10. The plasma processing method according to claim 9, wherein the evaluation sample data relates to a peak-to-peak voltage value of the bias generating high-frequency power required for performing the plasma processing in a desired state. 11. The plasma processing method according to claim 9, wherein the operation parameter for controlling the specific parameter is a value of a high frequency power for plasma generation. 12. An interpolative evaluation sample data required for controlling the specific parameter is calculated based on the evaluation sample data, and a specific parameter for plasma processing is controlled using the interpolative evaluation sample data. The plasma processing method according to claim 9, wherein: 13. The plasma generating high-frequency power according to claim 9, wherein a history of voltage fluctuation of said bias generating high-frequency power is held, and said plasma generating high-frequency power is controlled using said fluctuation history. Plasma treatment method.