JP2004152999A - Method and system for plasma processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a system for plasma processing in which a decision can be made in the early stage whether maintenance is performed normally or not, and the cause can be specified when the plasma processing rate is abnormal. <P>SOLUTION: When the normal system state and each element of chamber conditions, e.g. high frequency power conditions or gas conditions, are varied, impedance and processing rate under each state are measured and a variation curve (relation) is created previously for these measurements. Power conditions are measured after maintenance, and a decision is made whether the measurements fall within a predetermined range or not. Depending on the decision results, an abnormality is detected in the early stage and the cause of failure is specified. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma processing method and a plasma processing apparatus, and more particularly to a check method after maintenance.
[Prior art]
[0002]
In recent years, the size of semiconductor wafers, especially silicon wafers, glass substrates for liquid crystals, and the like has been rapidly increasing. For this reason, in plasma processing such as etching and film formation in the manufacture of semiconductor devices and liquid crystal display devices, uniform etching or film formation over the entire surface of the substrate has become a very important issue.
[0003]
In particular, in the field of semiconductor devices, as semiconductor devices become more highly integrated, the miniaturization of semiconductor devices continues to increase. For this reason, high quality and highly reliable processes are required in the field of etching or film formation.
[0004]
Therefore, there is a plasma treatment using plasma as a method capable of performing high-precision processing at a relatively low temperature. Even in such plasma processing, it is necessary to always maintain a stable plasma state in order to perform high-precision processing. Therefore, conventionally, various methods have been proposed for monitoring the plasma state.
[0005]
(1) A method in which a laser beam or the like is applied to the plasma to measure the state of the plasma using atomic absorption of a specific spectrum. (2) Using a mass analyzer, the molecules in the vacuum vessel are judged based on the mass and what is output. (3) A method in which a measuring probe is protruded into a plasma state and a plasma state is measured with a current flowing through the measuring probe (4) A detector for measuring high-frequency power is provided between a lower electrode and a matching device. There is a method of measuring the plasma state from the impedance of the plasma by inserting it.
[0006]
Above all, currently, the method of monitoring the state of plasma by the methods (3) and (4) is mainly used.
[0007]
However, there is a limit in time and labor to monitor the uniformity over a large area by such a method, and various methods have been proposed for efficient monitoring in a short time.
[0008]
For example, in a conventional plasma etching apparatus, high-frequency power, chamber pressure, gas flow rate, matching position, and the like, which are control parameters of the apparatus, are monitored. An interlock system that determines that there is a device and stops the operation of the device is generally employed.
Further, a method has been devised in which a Mahalanobis distance is calculated from such measured values, and when the Mahalanobis distance exceeds a predetermined value, it is determined that an abnormal operation has occurred (see Patent Document 1).
[0009]
[Patent Document 1]
Japanese Patent Application No. 2000-114130 [0010]
As shown in FIG. 4, a conventional plasma processing apparatus includes an upper electrode 102 mounted on an upper portion of a chamber 101 and a lower electrode 103 provided opposite to the upper electrode 102 and provided with a substrate to be processed. A vacuum pump (not shown) for evacuating the chamber 101, a gas supply source (not shown) for supplying a desired reactive gas into the chamber 101, and the upper electrode 102 and the lower electrode 103. A high-frequency power supply 107 for supplying a high-frequency voltage between them and generating plasma. The lower electrode 103 is connected to a high-frequency power source 107 via a high-frequency matching device 108. By applying an RF high-frequency (13.56 MHz) between the lower electrode 103 and the upper electrode 104, the vacuum processing tank 101 is formed. It is configured to excite plasma inside and perform surface treatment such as etching or film formation.
[0011]
At the time of the plasma processing, the upper electrode 102 is connected to a ground potential (GND) and the high-frequency power source 107 is connected to the lower electrode 103 via the matching unit 108 with respect to the electrode arranged inside the chamber 101. Keep it.
[0012]
First, the inside of the chamber 101 is evacuated by a vacuum pump and the pressure is reduced until a desired degree of vacuum is obtained.
Next, a reactive gas required for the process is flowed to keep the inside of the chamber 101 at a constant pressure, and high-frequency power is applied from the high-frequency power source 102 to the lower electrode 103 to generate plasma. Here, the high-frequency power applied to the lower electrode 103 is matched by a matching unit 108 including a coil and a variable capacitor.
[0013]
For example, when used in an etching process, as the etching process proceeds, a reaction product accumulates on the inner wall of the chamber, and when the reaction product reaches a certain degree or more, the reactive product drops as particles on the wafer. For this reason, in the case of the etching apparatus, when the RF discharge time reaches a predetermined time, the chamber is opened, and wiping maintenance and replacement of parts in the chamber where the reaction product is deposited are performed.
[0014]
For example, conventionally, as an example of the procedure for starting up the apparatus after the maintenance (step 1001), as shown in FIG. 5, an example of the process is as follows. First, vacuum evacuation (step 1002) is performed for several hours, and then seasoning is performed. (Step 1003), a maintenance test is performed (Step 1006), and finally, an etching rate and a particle are measured (Step 1007), and it is determined whether or not it is OK (Step 1005).
[0015]
Therefore, when an error such as forgetting to tighten a bolt or mounting a part upside down occurs during maintenance or the like, an error may not be found until the final etching rate measurement.
If an abnormality is found during the final measurement of the etching rate, it must be repaired and the maintenance (step 2008) performed again.
[0016]
[Problems to be solved by the invention]
As described above, the re-maintenance further extends the production stop time, which is a factor in reducing productivity. Further, even when an abnormality is found in the rate measurement, it is difficult to identify the cause, and it takes time.
[0017]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a plasma processing method and a plasma processing apparatus capable of early determining whether maintenance has been performed normally.
[0018]
It is another object of the present invention to provide a plasma processing method and a plasma processing apparatus capable of specifying a cause when there is an abnormality in a plasma processing rate.
[0019]
[Means for Solving the Problems]
As a result of various experiments, the present inventors have found that the relationship between the impedance and the processing speed depends on the change of each element in the chamber conditions, such as the power condition and the gas condition of the high-frequency power, in order to achieve the above object. The present invention has been made by focusing on the fact that the change curve not only changes but also has a slope corresponding to each element.
[0020]
In the present invention, the impedance and the processing speed for each state when the normal apparatus state and each of the chamber conditions such as the power condition and the gas condition of the high-frequency power are changed are measured, and the relationship between these conditions is determined in advance. Create a change curve (relational expression), measure the power condition after maintenance, judge whether the measured value is within a predetermined range, and detect abnormalities early according to the judgment result And the cause of the failure is specified.
[0021]
That is, in the first aspect of the present invention, a plasma processing method for introducing a reactive gas into an evacuated chamber, applying high-frequency power from a high-frequency power generation source to excite plasma, and performing plasma processing on a substrate to be processed. In, the impedance in a normal processing state, and measuring the processing speed of the substrate to be processed at that time, and defining a range of the normal state, prior to performing the plasma processing, impedance using a dummy wafer, A measuring step of measuring a processing speed of the dummy wafer; and a determining step of determining whether the processing condition is within the range in the measuring step.
[0022]
According to such a configuration, the impedance and the processing speed in a normal processing state are measured in advance, and the range is defined.Before performing the processing, the impedance and the processing speed are measured using a dummy wafer. An abnormality can be found at an early stage, and the time required for processing can be reduced. Here, if a bare silicon wafer is used as the dummy wafer, the processing can be easily performed without being influenced by other factors such as the shape of the mask pattern. Note that the impedance corresponds to the plasma density. That is, the low impedance means that the plasma contains many electrons and ions and the plasma density is high.
[0023]
Further, in advance, a change curve is formed for an impedance change with respect to each processing condition change when at least two processing conditions are changed from a normal processing state and a processing speed change of the substrate to be processed at that time. Comprising a step of creating, and when it is determined in the determination step that the value is out of the range, the measured value of the impedance and the processing speed when using the dummy wafer is compared with the change curve. Accordingly, by including the step of specifying the cause, the cause of the abnormality can be easily specified, and the repair can be performed with good workability.
[0024]
Desirably, if this measurement step is performed after maintenance, the measurement can be performed on the dummy wafer at an early stage, and the processing can be performed with good workability.
[0025]
In addition, if this measurement step is performed every time a predetermined number of wafers are processed, it is possible to quickly detect an abnormality.
Furthermore, the impedance can be easily detected by measuring the current and the voltage and calculating based on these values.
[0026]
In a second aspect of the present invention, a chamber formed so as to be evacuated, exhaust means for evacuating the chamber to a desired pressure, and reactive gas introduction for introducing a reactive gas into the chamber Means, and a high-frequency power generation source for generating high-frequency power between two electrodes disposed so as to face each other in the chamber to excite the reactive gas into plasma, one of the electrodes. A plasma processing apparatus for performing plasma processing of a substrate to be processed mounted on a current / voltage detector for detecting a current and a voltage of the high-frequency power, and a converter for calculating impedance from an output of the current / voltage detector A speed detector for detecting a processing speed of the plasma processing; and an output of the converter and the speed detector in a normal processing state as a reference value range. A value range is stored, and from a normal processing state, an impedance change with respect to each processing condition change when at least two processing conditions are changed, and a processing speed change of the substrate to be processed at that time, A change curve is created, a database storing the change curve, a comparator for comparing and comparing the outputs of the speed detector and the converter with the data extracted from the database, and an abnormality of the comparison result of the comparator. It is characterized in that the cause is specified.
[0027]
According to such a device, abnormality detection can be performed at an early stage, and an abnormality factor can be easily detected.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
The plasma processing apparatus according to the embodiment of the present invention is an etching apparatus. A voltage is applied between the electrode 103 and the impedance matching unit 108 connected to the high-frequency power supply 107 in the conventional plasma processing apparatus shown in FIG. And a current / voltage detector 109 for detecting current and voltage, a converter 110 for converting the current / voltage detected by the current / voltage detector 109 into a phase and impedance in addition to current / voltage, and a converter An apparatus in which the output of 110 is stored in advance with data on impedance and processing speed in a normal state in the apparatus and relation data of a change curve for each element when elements of chamber conditions such as gas conditions and power conditions are changed. Comparison for comparing and collating the relationship between the database 112 and the actual measured value and the change curve read out from this device database Adding a coupling device 111, it is characterized in that to be able to detect the maintenance failure and cause early. Other portions are formed in the same manner as the conventional plasma processing apparatus shown in FIG.
[0029]
In this chamber 101, parallel plate electrodes are arranged as in the conventional plasma processing apparatus shown in FIG. The lower electrode 103 serves as a stage on which a semiconductor wafer as a substrate to be processed 104 to be etched is placed, and the upper electrode 102 faces the lower electrode 103. High frequency power is applied to the lower electrode 103 and the upper electrode 102 by a high frequency power supply 107. A matching device 108 is provided between the high-frequency power supply 107 and the lower electrode 103 to match high-frequency power applied to the semiconductor wafer on the lower electrode 103.
[0030]
The matching unit 108 includes a variable coil wired in series and a variable capacitor. A gas supply system (not shown) is connected to an upper part of the chamber 101. A vacuum pump (not shown) is connected to the chamber 101. A constant flow rate of an etching gas is flowed, the interior of the vacuum vessel 1 is evacuated to a constant pressure by evacuating the vacuum vessel 10, high-frequency power is applied to the lower electrode 103 from a high-frequency power supply 107, and matching is performed by a matching unit 108. To produce good plasma conditions.
[0031]
Hereinafter, a method of performing dry etching using the plasma processing apparatus will be described with reference to a flowchart of FIG.
[0032]
First, a database is created prior to the actual operation.
When creating a database, first, a bare semiconductor wafer is loaded into the chamber 101 as the substrate to be processed 104 by the loading / unloading means, and is placed on the lower electrode 103.
[0033]
Then, a gas is introduced into the chamber 101 by a reactive gas introduction unit, and a gas in the chamber 101 is exhausted by an exhaust unit (not shown), and the inside of the chamber 101 is adjusted to a predetermined pressure by a pressure control unit 102. maintain.
[0034]
Next, high frequency power is applied to the lower electrode 103 from the high frequency power supply 107.
The gas in the chamber 101 is turned into plasma by the high-frequency power applied to the lower electrode 103, and the film to be etched on the substrate to be processed 104 is plasma-etched by the electrons and radicals in the plasma.
[0035]
Here, exhaust gas components and reaction products generated by the etching reaction are exhausted by exhaust means (not shown).
[0036]
With this operation, the application condition of the high-frequency power is changed, and a relational expression between the measured value of the current / voltage detector 109 and the etching rate is created. Here, a measurement value and an etching rate when each of the gas flow rate, the RF power, and the like is changed by about ± 10% with respect to the standard condition are measured, and a relational expression is created. Here, bare silicon was used as the semiconductor wafer, and the variation factor was reduced as much as possible to detect the etching rate. The device database 112 is created in this way. A part of this database is shown in FIG. The vertical axis indicates the etching rate (square dot), the impedance (triangular dot), and the horizontal axis indicates the change in the flow rate of C ₅ F ₈ , the change in the flow rate of oxygen O ₂ , the lower electrode temperature BTM, the upper electrode temperature TOP, the chamber internal pressure Pre, and the room temperature. B. Indicates temp.
[0037]
In this state, etching is started, and maintenance is performed after a predetermined period has elapsed (step 1001).
[0038]
First, a dummy semiconductor wafer as the substrate to be processed 104 is loaded into the chamber 101 by the loading / unloading means, and is placed on the lower electrode 103 in the same manner. A gas is introduced into the chamber 101 by the reactive gas introduction unit, the gas in the chamber 101 is exhausted by the exhaust unit (not shown), and the inside of the chamber 101 is maintained at a predetermined pressure by the pressure control unit 102. (Step 1002).
[0039]
Next, high frequency power is applied to the lower electrode 103 from the high frequency power supply 107.
The gas in the chamber 101 is turned into plasma by the high-frequency power applied to the lower electrode 103, and the film to be etched on the dummy substrate is plasma-etched by the electrons and radicals in the plasma. ) Is detected (step 1003S).
[0040]
Then, comparison and collation with the device database are performed (step 1004). Here, the converter 110 converts the current / voltage into a phase and an impedance from the detection value detected by the current / voltage detector 109, and compares the current / voltage with the device database 112 to determine the maintenance quality.
[0041]
Then, it is determined whether or not it is OK (step 1005). If it is OK, maintenance is performed (step 1006). Here, the gas flow rate, pressure, presence / absence of chamber leak, and the like for plasma processing are detected.
[0042]
Then, the etching rate and the particles are measured (step 1006), and the etching process of the next batch is executed.
If it is determined in the determination step 1005 that there is a problem with the maintenance, a measure is taken for the cause (step 1008). At this time, by collating the database, it is possible to specify the cause such as whether the cause is a gas flow deviation, a pressure deviation, or a part assembly error.
For example, when the impedance is 105.9 ohms and the etching rate is 410 nm / min, this value is out of the etching rate of 395 nm / min and the impedance of 106.55 ohms, and it is determined that there is an abnormality. Further, this point is determined on the curve in FIG. 3 and the cause is examined.
In this case, it is determined that it is closest to the point A on the curve in FIG. 3 and is therefore similar to the change when the flow rate of C5F8 is increased, and it is determined that the abnormal factor is caused by the increase in the flow rate of C5F8.
When the impedance is 105.5 ohms and the etching rate is 400 nm / min, the presence / absence of an abnormality and the factor are similarly examined.
In this case, it is located at point B on the curve in FIG. 3 and is determined to be similar to the change at the time of pressure drop, and it is determined that the abnormal factor is due to the pressure drop.
[0043]
In this way, the above identified factors are restored, and the process returns to the chamber evacuation step 1002 again to make a pass / fail judgment.
According to this method, the quality of the maintenance is determined before the maintenance test is performed, so that an abnormality is found at an early stage, so that the processing can be made more efficient.
[0044]
This monitoring enables efficient and early detection of abnormalities such as gas temperature, pressure, and the presence or absence of chamber leaks for plasma processing, so that high-precision and stable measurement can be performed over a long period with good workability. .
[0045]
In the above embodiment, the etching process has been described. However, it is needless to say that the present invention can be applied to a film forming process such as plasma CVD and plasma sputtering.
[0046]
【The invention's effect】
As described above, according to the present invention, it is determined whether the current, voltage, phase, and impedance detected after maintenance are within a predetermined range. By comparing and collating with the relational expression, it can be determined at an early stage whether or not the maintenance has been performed normally, and the cause can be specified.
[Brief description of the drawings]
FIG. 1 is a diagram showing a plasma processing apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a flowchart of a plasma processing step according to the embodiment of the present invention.
FIG. 3 is an explanatory diagram showing impedance and etching rate change curve data of a database used in the embodiment of the present invention.
FIG. 4 is a diagram showing a conventional plasma processing apparatus.
FIG. 5 is a view showing a flowchart of a conventional plasma processing step.
[Explanation of symbols]
Reference Signs List 101 Chamber 102 Upper electrode 103 Lower electrode 104 Substrate to be processed 107 High frequency power supply 108 Matching device 109 Current / voltage detector 110 Transformer 111 Comparative matching device 112 Device database

Claims (6)

In a plasma processing method of introducing a reactive gas into a vacuum-evacuated chamber, applying high-frequency power from a high-frequency power generation source, exciting plasma, and performing plasma processing on a substrate to be processed,
Measuring the impedance in a normal processing state and the processing speed of the substrate to be processed at that time, and defining a range of the normal state;
Prior to performing the plasma processing, impedance using a dummy wafer, a measuring step of measuring the processing speed of the dummy wafer,
A determining step of determining whether the processing condition is within the range in the measuring step. Further, in advance, a change curve is formed for an impedance change with respect to each processing condition change when at least two processing conditions are changed from a normal processing state and a processing speed change of the substrate to be processed at that time. Including the step of creating,
In the determining step, when it is determined that the value is out of the range, the measured value of the impedance and the processing speed when the dummy wafer is used, and comparing and comparing the change curve, to identify the cause 2. The plasma processing method according to claim 1, comprising: The method according to claim 1, wherein the measuring step is performed after maintenance. 4. The plasma processing method according to claim 1, wherein the measuring step is performed every time a predetermined number of wafers are processed. The plasma processing method according to any one of claims 1 to 4, wherein the impedance is obtained by measuring a current and a voltage and calculating based on these values. A chamber formed to be evacuated,
Exhaust means for evacuating the chamber to a desired pressure,
Reactive gas introduction means for introducing a reactive gas into the chamber,
A high-frequency power generation source that generates high-frequency power and excites the reactive gas into plasma between two electrodes disposed so as to face each other in the chamber, and is mounted on one of the electrodes; In the plasma processing apparatus for performing the plasma processing of the substrate to be processed,
A current / voltage detector for detecting a current and a voltage of the high-frequency power,
A converter for calculating impedance from the output of the current / voltage detector,
A speed detector for detecting a processing speed of the plasma processing,
The output of the converter and the speed detector in a normal processing state is set as a reference value range, and this reference value range is stored, and each processing when at least two processing conditions are changed from the normal processing state For a change in impedance with respect to a change in condition and a change in processing speed of the substrate at that time, a change curve is created, and a database storing the change curve
A comparator for comparing the output of the speed detector and the converter with data retrieved from the database;
A plasma processing apparatus characterized in that the cause of the abnormality is specified from the comparison result of the comparator.

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