JP4873025B2 - Plasma processing method - Google Patents

Description

  The present invention relates to a plasma processing method according to a manufacturing technique in a thin film forming process of a semiconductor device, an electronic component or the like and an etching process using AC power and plasma.

  This type of conventional manufacturing technology is configured as shown in FIG. A conventional manufacturing technology for semiconductor devices, electronic components, and the like will be described with reference to FIG. In general, for semiconductors and electronic components, a pattern is formed on a mask film on a thin film by a film forming process for forming a thin film on a wafer 3 by a film forming apparatus 1 such as sputtering or CVD (chemical vapor deposition method) and photolithography. This is manufactured by repeating an etching process (not shown) and an etching process for processing a thin film into a fine pattern by etching a portion not masked in a state masked by the etching apparatus 2 (paragraph 49 of Patent Document 1). ~ 59).

  When forming a thin film in the film forming apparatus 1, the crystallinity, density, etc. of the thin film depend on film forming conditions such as process gas pressure, flow rate, mixing ratio, power used for the process, power applied to the wafer, and wafer temperature. The film quality is determined. In the example shown in FIG. 3, the film quality is controlled by the wafer temperature controller 9. Whether or not the etching process in the next etching process can be normally performed is determined by the film quality. As an etching apparatus for processing a thin film into a fine pattern, a dry etching apparatus is generally used in response to the recent miniaturization of devices.

  A dry etching apparatus (hereinafter referred to as an etching apparatus) converts a gas into a plasma under a reduced pressure atmosphere and chemically or physically removes a thin film using active species and ions in the gas. As shown in FIG. 3, the etching apparatus 2 has a plasma source 8 for converting the gas into plasma. As the plasma source 8, a plate electrode or coil to which a voltage of 100 V to 1000 V and a frequency of 100 kHz to 100 MHz are applied is used.

  The processing accuracy of the etching process is determined by the direction and energy when ions in the plasma collide with the thin film on the wafer 3. Therefore, in general, the etching apparatus 2 is applied with AC power to the wafer 3 in order to cause ions in the plasma to collide with the thin film on the wafer 3 with good controllability. The reason why AC is used is that an electronic device always has an insulating layer, and ions cannot be controlled by DC.

  Since the AC power applied to the wafer 3 is important with respect to the characteristics of the etching process as described above, a technique using the AC power monitoring device 6 of the measuring device that measures the voltage, current, and phase of the AC power flowing through the wafer 3 is shown. (See Patent Documents 2 and 3).

  In addition, the etched wafer 3 is sent to the next process, and the state of the etching process such as whether etching residue or excessive etching has occurred during the process is inspected. Since the inspection of the etching state takes time and there is a risk of particle adhesion, contamination of the wafer 3, etc., it is not carried out on all the etched wafers 3, but as shown in FIG. In the period, it is inspected by the sampling inspection device 4.

  If there is an abnormality in the etching state as a result of the inspection, if it is caused by the film forming apparatus 1, the film forming condition of the film forming apparatus 1, for example, the temperature of the wafer 3 is changed, and the film quality can be appropriately etched. Adjust to obtain a film.

Since the film forming apparatus 1 forms a film on the wafer 3 and deposits a film in the chamber of the film forming apparatus 1, the plasma state that determines the film quality and the temperature distribution in the chamber change with production. Therefore, a thin film having a quality that cannot be properly etched unless the film forming conditions are adjusted is formed. Therefore, it is necessary to inspect the etching state and adjust the film forming conditions. Patent Document 4 describes a specific example of inspection.
Japanese Patent Laid-Open No. 2002-296609 JP 2003-142455 A JP 2001-338917 A JP 2000-150604 A

  However, in the manufacturing technology having such a configuration, since the etching state inspection is a sampling inspection performed for a certain period of time, abnormalities such as etching residue and excessive etching due to the film quality of the thin film formed on the wafer by the film forming apparatus. When an abnormal etching state occurs, a similar abnormality has occurred in a wafer that has already been processed, and there has been a problem that adjustment of film forming conditions has been delayed.

  In addition, in the conventional configuration described in Patent Documents 2 and 3, only the technique for changing the etching conditions of the etching apparatus is disclosed, and the etching state caused by the film quality of the thin film formed on the wafer by the film forming apparatus is disclosed. In addition, the conventional configuration described in Patent Document 4 has not been able to sufficiently cope with the detection and countermeasures of abnormalities, and in the conventional configuration described in Patent Document 4 for the problem of early detection of abnormalities, inspection is performed for each processing apparatus such as a film forming apparatus and an etching apparatus Although a method for introducing a process has been disclosed, there has been a problem that the manufacturing cost becomes high.

  The present invention is directed to solving the problems of the prior art, and in an electronic device manufacturing process including a thin film forming process and an etching process using plasma, an abnormality in the thin film forming process is solved early, and An object is to provide a low-cost plasma processing method.

In order to achieve this object, a plasma processing method according to claim 1 of the present invention includes a thin film forming process for forming a thin film on a wafer, and plasma is generated after the thin film forming process to form a thin film on the wafer. A plasma processing method including an etching process step for removing an AC power monitoring device for measuring the voltage, current, and phase of AC power flowing through the wafer through a thin film in contact with plasma during the processing in the etching apparatus performing the etching process. When the value of the function including any one of the measured voltage, current, and phase falls outside the range of a predetermined value, it is detected as an abnormality of the thin film on the wafer , and the thin film formation process is completed. With the processing method that changes the film conditions, the electrical characteristics of the AC power flowing through the wafer through the thin film in contact with the plasma are measured to accurately detect abnormalities in the thin film. It is necessary to detect and detect abnormalities at an early stage by measuring all wafers to be processed, and it is necessary to add a new monitoring device for film forming equipment using a device for monitoring abnormalities in the etching process No cost can be achieved.

  The plasma processing method according to claims 2 and 3 is the plasma processing method according to claim 1, wherein the function for detecting the abnormality of the wafer is an impedance value obtained by dividing the voltage by the current, and the thin film Impedance value is equivalent to the resistance value of the thin film on the wafer by the processing method in which the forming process is a process of sputtering film formation by direct current discharge. Anomalies in film quality due to the process can be detected, and the electrical characteristics of the AC power flowing through the film on the wafer that cannot be measured with a sputtering film deposition device using DC discharge can be measured with an etching device. Abnormalities in the film quality caused by the thin film formation process can be detected accurately without adding an apparatus.

According to another aspect of the present invention, there is provided a plasma processing method comprising: a thin film forming process for forming a thin film on a wafer; and an etching process for generating a plasma after the thin film forming process to remove the thin film from the wafer. Including a plasma processing method in which the wafer is etched a plurality of times in the same apparatus, wherein the etching apparatus performing the etching process causes the voltage, current, and phase of AC power flowing through the wafer through a thin film in contact with the plasma during processing. Is a value in which the difference between the value of the function including any one of the measured voltage, current, and phase and the value of the function measured during the previous etching process on the same wafer is a predetermined value. by a method of detecting an abnormality of the thin film on the wafer when out of range, to change the film formation conditions of the thin film formation step, It can detect an abnormality in film quality due to less susceptible accurately thin film formation process the influence of the variation of the wafer because it uses the change in the electrical characteristics of the AC power flowing in the previous etching process of one wafer.

  As described above, according to the present invention, since the electrical characteristics of the AC power flowing through the wafer through the thin film in contact with the plasma are measured, the abnormality of the thin film can be accurately monitored, and the measurement is performed for all wafers to be processed. Therefore, it can be discovered early, and an apparatus for monitoring abnormalities in the etching process is used, so that it is not necessary to add a new apparatus for monitoring the film forming apparatus, and the cost can be reduced.

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

  FIG. 1 is a block diagram showing a schematic configuration of a manufacturing apparatus that performs a plasma processing method according to Embodiment 1 of the present invention. Here, components having substantially the same functions corresponding to the components described in FIG. 3 showing the conventional example are denoted by the same reference numerals.

  As shown in FIG. 1, a film forming apparatus 1 is an apparatus for sputtering film formation by direct current discharge, and forms an Al (aluminum) alloy-based thin film on a wafer 3 on which an electronic device is formed. In the sputtering apparatus (film forming apparatus 1), a target 12 made of an Al alloy is placed in a reduced pressure chamber of about 0.1 Pa to 10 Pa into which an inert gas such as Ar (argon) gas is introduced. A voltage of 100 V to 1000 V is applied to generate plasma 10. Ions in the plasma 10 are attracted to the target 12 by the voltage applied to the target 12 to cause collision and scatter the target material.

  The scattered target material adheres to the wafer 3 to form a thin film. The thin film has different etching characteristics depending on its density. A film having a high density tends to cause an etching residue, and a film having a low density tends to cause excessive etching. In the film forming apparatus 1, the wafer 3 temperature is controlled between 100 ° C. and 300 ° C. by the wafer temperature controller 9 so that an appropriate etchable film can be formed. The higher the temperature, the higher the film density.

  The etching apparatus 2 converts the gas into a plasma under a reduced pressure atmosphere of 0.1 Pa to 1000 Pa and chemically or physically removes the thin film using active species and ions in the gas. The etching apparatus 2 has a plasma source 8 for converting gas into plasma as shown in FIG. As the plasma source 8, a plate electrode or coil to which a voltage of 100 V to 1000 V and a frequency of 100 kHz to 100 MHz are applied is used.

  The processing accuracy of the etching process is determined by the direction and energy when ions in the plasma 5 collide with the thin film on the wafer 3. Therefore, in general, the etching apparatus 2 is applied with AC power from the AC power source 7 to the wafer 3 so that the ions in the plasma 5 collide with the thin film on the wafer 3 with good controllability. The reason why AC is used here is that an electronic device always has an insulating layer, and ions cannot be controlled by DC.

  Since the AC power applied to the wafer 3 is important with respect to the characteristics of the etching process, the AC power monitor device 6 that measures the voltage, current, and phase of the AC power flowing through the wafer 3 is used. In Example 1 of the first embodiment, typical conditions are a power of 600 W of the plasma source 8 and an AC power of 200 W applied to the wafer 3. The measured current is 8 A, the voltage is 384 V, and the phase is −86. It was 2 degrees.

  In the first embodiment, an impedance value obtained by dividing a measured voltage by a current is used as a function value for detecting an abnormality of the wafer 3. Since the impedance corresponds to the resistance value of the thin film on the wafer 3, the film quality abnormality caused by the thin film forming process can be detected with high accuracy and is not easily affected by the power fluctuation during the etching process. The normal impedance value in the first embodiment is 48Ω to 49Ω.

  In the film forming apparatus 1, the state of the plasma 10 changes as the target 12 is consumed. In the first embodiment, the power applied to the target 12 to be sputtered is constant at 1200 W, but the current flowing from the plasma 10 into the target 12 is 2.5 A at the start of target use and 2.85 A when the target is consumed. . As the plasma 10 changes with time, the quality of the film formed also changes. In Example 1, the film density was changed in the direction of decreasing.

  When this film was etched by the etching device 2, there was a problem that excessive etching occurred and the wafer 3 side of the pattern became thin. At this time, the impedance value was 47.5Ω, which was outside the normal range of 48Ω to 49Ω.

  Therefore, a signal is sent from the etching apparatus 2 to the wafer temperature controller 9 of the film forming apparatus 1 to increase the temperature of the wafer 3 by 30 ° C. so that the film density increases. As a result, the impedance of the wafer 3 to be processed next recovered to 48.5Ω, and excessive etching processing was not generated. If the impedance is 49Ω or more, a signal for instructing the wafer temperature controller 9 to lower the temperature may be sent.

  As described above, according to the plasma processing method of the first embodiment, since the electrical characteristics of the AC power flowing through the wafer 3 through the thin film in contact with the plasma 5 are measured, the abnormality of the thin film can be accurately monitored. Further, since all the wafers 3 to be processed are measured, they can be discovered at an early stage. Furthermore, since an apparatus for monitoring an abnormality in the etching process is used, it is not necessary to add a new apparatus for monitoring the film forming apparatus 1, and the cost can be reduced.

  Next, Example 2 in the first embodiment will be described. In the second embodiment, the abnormality of the thin film formed on the wafer 3 is detected using only the change in impedance of the wafer 3 to be etched. However, the change in impedance is caused by the abnormality of the thin film formed on the wafer 3. Not only the cause but also a change due to wear of parts in the etching apparatus 2 may occur. For this reason, it is necessary to exclude the impedance change resulting from such an etching apparatus 2.

  After detecting an abnormality in the wafer 3 with a thin film of the etching apparatus 2, the impedance is measured by etching a wafer on which a thin film such as a bare silicon wafer is not formed, and when the bare silicon wafer is etched normally. Compare with impedance. If the impedance change in this bare silicon wafer is within a normal value, it can be determined that the impedance change is due to a thin film formed on the wafer 3. Further, if the impedance change in the bare silicon wafer is outside the normal value, it can be determined that the abnormality is due to the etching apparatus 2. The width of the normal value changing in the present Example 2 was 0.5Ω or less.

  Generally, before the continuous etching process, a bare silicon wafer is processed in order to stabilize the atmosphere such as the temperature in the chamber. By measuring the impedance during processing of this bare silicon wafer and using it for the above-described determination, it is possible to detect an abnormality caused by the thin film with high accuracy.

  Next, Example 3 in the first embodiment will be described. In a plasma processing method including a step of forming a thin film on a wafer and an etching step of generating plasma after the step of forming the thin film to remove the thin film from the substrate, the wafer is processed a plurality of times by the same etching apparatus. In some cases, the manufacturing process of an electronic device having a multilayer wiring structure corresponds to this.

  In such a case, in this third embodiment, the difference between the current measured impedance and the impedance when the same wafer was measured during the previous etching process is calculated, and is outside the predetermined value range. The wafer is detected as abnormal. According to this, it is possible to detect an abnormality in the film quality caused by the thin film forming process with high accuracy and being hardly affected by the variation of the wafer.

  FIG. 2 is a block diagram showing a schematic configuration of a manufacturing apparatus that performs the plasma processing method according to Embodiment 2 of the present invention. As shown in FIG. 2, the plasma source 18 includes an electrode 15 and an AC power source 17 and includes a second AC power monitor device 16. The AC power source 7 and the AC power source 17 have different frequencies. In the second embodiment, the AC power source 7 is 300 kHz, and the AC power source 17 is 13.56 MHz. When the impedance measured by the first AC power monitoring device 6 deviates from the normal value, if the impedance measured by the second AC power monitoring device 16 is within the normal value, this abnormality is detected on the thin film on the wafer 3. It can be judged that this is due to an abnormality.

  According to the second embodiment, since the state of the etching apparatus 2 can be grasped without being affected by the thin film on the wafer 3, whether the abnormality detected in the wafer 3 with the thin film is due to the abnormality of the etching apparatus 2, It is possible to accurately determine whether the thin film is formed on the wafer 3, and as a result, it is possible to accurately detect an abnormality in the film quality caused by the thin film forming process.

  The plasma processing method according to the present invention can accurately monitor the abnormality of the film on the wafer by measuring the electric characteristics of the AC power flowing through the wafer through the film on the wafer in contact with the plasma, in addition to the thin film constituting the electronic device. Is also useful for detecting abnormalities such as resist films used in the manufacturing process and changing process conditions.

The block diagram which shows schematic structure of the manufacturing apparatus which performs the plasma processing method in Embodiment 1 of this invention. The block diagram which shows schematic structure of the manufacturing apparatus which performs the plasma processing method in Embodiment 2 of this invention. The block diagram which shows schematic structure of the manufacturing apparatus which performs the conventional thin film formation process and an etching process

DESCRIPTION OF SYMBOLS 1 Film-forming apparatus 2 Etching apparatus 3 Wafer 4 Inspection apparatus 5 Plasma (inside of etching apparatus)
6 AC power monitoring device 7 AC power source 8 Plasma source 9 Wafer temperature controller 10 Plasma (inside the film deposition system)
11 DC Power Supply 12 Target 15 Electrode 16 AC Power Monitor 17 AC Power Source 18 Plasma Source

Claims (4)

A plasma processing method comprising: a thin film forming process for forming a thin film on a wafer; and an etching process for generating plasma after the thin film forming process to remove the thin film from the wafer,
In the etching apparatus for performing the etching process, the voltage, current, and phase of the AC power flowing through the wafer through the thin film in contact with the plasma during the process are measured by the AC power monitor apparatus, and any one of the measured voltage, current, and phase is measured. A plasma processing method characterized in that when a value of a function including a value outside a predetermined value range is detected as an abnormality of the thin film on the wafer , the film forming conditions in the thin film forming step are changed.
2. The plasma processing method according to claim 1, wherein the function for detecting an abnormality of the wafer is a voltage divided by a current. The plasma processing method according to claim 1, wherein the thin film forming step is a step of performing sputtering film formation by direct current discharge. Plasma including a thin film forming process for forming a thin film on a wafer and an etching process for generating plasma after the thin film forming process to remove the thin film from the wafer. A processing method,
The etching apparatus that performs the etching process measures the voltage, current, and phase of AC power that flows through the wafer through the thin film that is in contact with the plasma during the process using the AC power monitor apparatus, and the measured voltage, current, or phase When the difference between the value of the function including the value of the function measured during the previous etching process on the same wafer is out of the predetermined value range, it is detected as an abnormality of the thin film on the wafer, A plasma processing method characterized by changing film forming conditions in a thin film forming step.

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