JP2007149960A - Plasma processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide plasma processing technology capable of suppressing the generation of abnormality during transferring a specimen as a wafer or the like, and operating stably for a long period of time. <P>SOLUTION: The plasma processor is provided with a vacuum processing chamber 106 equipped with a specimen mounting table 204 for sucking and retaining the mounted specimen 203, and a plasma producing means for producing plasma on the specimen mounting table 204; and a vacuum transfer means 201 arranged in a buffer chamber 105 to mount the specimen 203 transferred into a load lock chamber on the specimen mounting table 204 through the buffer chamber 105, and to transfer an already processed specimen 203 mounted on the specimen mounting table 204 into a load lock chamber through the buffer chamber 105. Sensors 202a, 202b for detecting the position of the already transferred specimen 203 are equipped in the transfer route of the specimen 203 by the vacuum transfer means 201. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma processing technique, and more particularly, to a plasma processing technique that can suppress the occurrence of abnormality during processing of a sample.

  In the process of manufacturing a semiconductor device, when a sample such as a semiconductor wafer is transported, it is desirable to perform processing with low dust generation and less occurrence of abnormality. When dust is generated before wafer processing during wafer transfer, the dust adheres to an object to be processed such as a semiconductor wafer and causes a device pattern defect (such as a wiring short), resulting in a decrease in manufacturing yield. .

  Further, when a transfer abnormality occurs during the transfer of a wafer, the transfer may be stopped after recognizing that it is a serious failure, and then the processing chamber may be released to the atmosphere for repair or maintenance. In such a case, it takes time for the processing chamber to be evacuated, so that the time during which the processing is not performed, so-called down time, is increased, and the overall processing efficiency of the apparatus is impaired.

  Concerning such a problem, a conveyance abnormality such as a wafer misalignment during wafer conveyance is detected, and correction is performed before the abnormality reaches a more serious abnormality such as a drop, dropout, or an installation abnormality of the wafer. A technique for informing and suppressing the occurrence of a serious abnormality has been studied. For example, the amount of deviation of the wafer center position from the reference position on the hand of the robot arm holding (supporting) the wafer is detected immediately before being transferred to the processing chamber, and the wafer is placed on the mounting table based on the detection result. There has been proposed a technique for correcting the positional deviation by adjusting the movement of the hand that is transported to the front.

Further, Patent Document 1 discloses a semiconductor processing apparatus as a semiconductor processing cluster tool structure system including a polygonal vacuum transfer module and a plurality of processing chambers arranged around the polygonal vacuum transfer module. In this apparatus, a plurality of position sensors are arranged in the vicinity of the connection portion with the processing chamber in the vacuum transfer module so as to cross the semiconductor wafer transfer direction, and the position of the semiconductor wafer being transferred is shifted by this position sensor. Is detected, and the wafer position is adjusted based on the detection result, and then placed on a predetermined position in the processing chamber.
Japanese Patent Laid-Open No. 2001-210698

  The prior art described above corrects the wafer misalignment before wafer processing. However, no consideration has been given to wafer positional deviations that occur after wafer processing, or means for suppressing the occurrence of positional deviations.

  That is, according to the above-described prior art, even when the wafer is installed in accordance with the reference position of the mounting table in the processing chamber, when the wafer is unloaded from the mounting table, for example, due to the interaction between the wafer and the mounting table, The wafer may be displaced from the reference position. In this case, the wafer falls during the unloading of the wafer, or is damaged by collision with other members, or dust is generated.

  The present invention has been made in view of these problems, and provides a plasma processing technique that can suppress the occurrence of abnormality during the transfer of a sample such as a wafer and can operate stably for a long period of time. .

  In order to solve the above problems, the present invention employs the following means.

  A sample mounting table for sucking and holding the mounted sample and a plasma generating means for generating plasma on the sample mounting table, a vacuum processing chamber, a buffer chamber, and a sample transported to the load lock chamber A vacuum transfer means for transferring the processed sample mounted on the sample mounting table to the load lock chamber through the buffer chamber and the sample stored in the cassette. And an atmospheric transfer unit for storing the processed sample transferred to the load lock chamber and storing the processed sample in a cassette, and the sample stage once pushes the sample onto the sample mounting table, A push-up pin placed on the hand portion of the vacuum transfer means that has entered the lower part of the sample is provided, and a sensor for detecting the position of the sample to be transferred is provided in the sample transfer path by the vacuum transfer means. With.

  Since the present invention has the above-described configuration, it is possible to provide a plasma processing technique that can suppress the occurrence of abnormality during the transfer of a sample such as a wafer and can operate stably for a long period of time.

  Hereinafter, the best embodiment will be described with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a plasma processing apparatus according to the present embodiment. The plasma processing apparatus 100 includes a plurality (two) of cassette stands 102 on the front side (the lower side in the figure). For example, cassettes 101 that can store, for example, about 25 semiconductor wafers having a diameter of 200 mm are installed on the cassette base. The wafers stored in the cassette are transferred into the plasma processing apparatus 100 and processed, and the processed wafers are returned to the cassette.

  On the back side (upper side in the drawing) of the atmospheric transfer unit 103, load lock chambers 104 and 104 ′ are arranged for switching between transfer in the atmosphere and transfer in vacuum when transferring the wafer in the cassette 101. . The pressure in the load lock chambers 104 and 104 'can be adjusted between the atmospheric pressure and the vacuum pressure.

  For example, after the wafer is transferred from the cassette to the load lock chamber by the atmospheric transfer unit 103, the load lock chamber is adjusted to the vacuum pressure. Thereafter, the transfer device is switched to a vacuum transfer robot installed in the buffer chamber 105, and the wafers transferred into the load lock chamber are transferred into the etching processing chambers 106 and 106 'or the ashing processing chambers 107 and 107'.

  The wafers processed in the etching chambers 106 and 106 'or the ashing chambers 107 and 107' are returned to the cassette according to the reverse procedure. In the passage connecting the buffer chamber 105 and each processing chamber, gate valves 111 and 111 ′ as partitions for opening and closing the passage and partitioning them are arranged on the inlet side or the outlet side of the passage. Yes. In the example shown in the figure, a plurality of sensors for detecting the position of the wafer in the buffer chamber are provided, thereby monitoring the wafer conveyance. These sensors can use electromagnetic waves such as lasers, infrared rays, or highly directional radio waves. A sound wave can also be used.

  FIG. 2 is a diagram illustrating details of the etching chamber and the buffer chamber shown in FIG. FIG. 3 is a cross-sectional view of FIG. Hereinafter, description will be made with reference to FIGS.

  First, the wafer 203 is carried into the etching chamber 106 by the vacuum transfer robot 201 disposed in the buffer chamber 105. In FIG. 2, both the processing chambers are the etching processing chambers 106 and 106 ′, but one of them can be the ashing processing chamber 107, for example. In these processing chambers, gate valves 111 and 111 ′ for partitioning the inner space and the space in the buffer chamber 105 are arranged. As shown in FIG. 3, these gate valves 111 and 111 ′ include a valve body 112, and the valve body is driven up and down by an air cylinder 304 to open and close a passage between the processing chamber and the buffer chamber 105. .

  That is, when the unprocessed wafer 203 is carried into the etching processing chamber 106, the valve 112 is moved downward to open the communicating path. Then, after the wafer is loaded, the valve body 112 is moved upward to close the passage.

  While the wafer 203 is being processed, the passage is closed by the valve body 112. When the processing is completed and the wafer 203 is unloaded, the valve body 112 is moved downward again to open the passage.

  On the transfer path of the wafer 203 in the buffer chamber 105, a light shielding sensor 202 having a light emitting unit 202a and a light receiving unit 202b is arranged. When the wafer 203 placed on and held on the hand 205 of the vacuum transfer robot 201 passes between the light emitting unit 202a and the light receiving unit 202b of the light shielding sensor, the light passing between the light emitting units 202a and 202b is blocked by the wafer 203. At this time, by referring to the light shielding time by the wafer 203 and the trajectory of the vacuum transfer robot 201 set in advance, the center position of the wafer 203 and the center position of the wafer 203 placed on the hand 205 can be determined. It is possible to calculate whether or not they are separated from each other.

  It should be noted that when the wafer 203 is loaded into each processing chamber (the etching processing chamber 106 in the case of FIG. 2) based on the positional deviation amount thus calculated, the wafer 203 is transferred while correcting the trajectory of the vacuum transfer robot 201. can do. Alternatively, after transporting and reaching a predetermined position, the positional deviation amount is corrected, and the center of the wafer and the center of the mounting tables 204 and 204 ′ in the etching chamber 106 (106 ′) are aligned with each other. be able to.

  When adjusting the position of the wafer 203, first, a signal from the control unit 302 receiving the output of the light shielding sensor 202 is transmitted to the control device 301 that controls the overall movement, and the arithmetic unit in the control device 301 causes the wafer 203 to be adjusted. The amount of positional deviation is calculated. Information on the amount of misalignment is transmitted to a control device 303 that controls the vacuum transfer robot 201, and the control device 303 operates the vacuum transfer robot 201 in accordance with the amount of misalignment based on the received information on misalignment. The position where the hand 205 finally reaches is adjusted to a desired position, and the wafer is placed at this position.

  The mounting table 204 in the etching chamber 106 is configured to be able to suck and hold the mounted sample (wafer) by electrostatic force. When a predetermined etching process is completed while the wafer 203 is attracted and held on the mounting table 204, the electrostatic chucking is released, and a plurality of push-up pins provided in a push-up mechanism (not shown) arranged in the mounting table 204 are operated. Then, the wafer 203 is pushed up onto the mounting table 204.

  Thereafter, the vacuum transfer robot 201 is operated, and the hand 205 enters under the pushed-up wafer 203. Next, the push-up pin of the push-up mechanism is moved downward to place the wafer 203 on the hand 205. Thereafter, when the push-up pin continues to descend, the push-up pin can be stored in the mounting table 204. As a result, the wafer 203 is transferred from the push-up pin to the hand 205.

  In this way, the vacuum transfer robot 201 receives the wafer 203 by the hand 205 and carries the received wafer from the etching chamber 106 to the buffer chamber 105. At this time, the wafer 203 passes over the light shielding sensor 202 again. The position of the wafer at this time is detected. As for the detection signal, the amount of displacement is detected in the same manner as when the wafer 204 is carried into the etching chamber 16. In this way, it is possible to detect the amount of wafer misalignment that occurs during the operation of unloading the wafer 203 from the etching processing chamber 106.

  As described above, the inventors have obtained the knowledge that the cause of the positional deviation of the wafer during unloading is due to the form of wafer removal from the mounting table that holds the wafer by electrostatic adsorption. It was. That is, the mounting table 204 is generally provided with an insulator for the purpose of accumulating charges so as to electrostatically attract the wafer 203, and the insulator has a thickness, an area, a specific resistance of a material constituting the insulator, and the like. It is manufactured by adjusting to a predetermined value. However, once electrostatically attracted, an operation called static elimination may become unstable. This unstable phenomenon is considered to be caused by variations in the characteristics of the “electrostatic adsorption film containing an insulator” that constitutes the installation surface of the wafer 203 disposed on the mounting table 204.

  The electrostatic adsorption film includes an electrode made of an insulating member film having a predetermined thickness and one or more conductive member films such as tungsten disposed therein. The variation in the characteristics is caused by, for example, a variation in the distribution of the characteristics of the electrostatic adsorption film due to a difference in film thickness or a variation in the balance of the distribution of the contact surface between the wafer 203 and the electrostatic adsorption film. . Even if the balance is slightly lost in this way, this collapse appears when the wafer 203 is pushed up by the push-up pins, in the form of an inclination with respect to the installation surface of the wafer 203, that is, a single lift. That is, the wafer 203 tilts with the operation of the pins of the push-up mechanism due to a deviation in the magnitude of the local attraction force of the wafer 203, that is, a variation in the surface direction adsorption characteristics of the wafer 203.

  When such a single lift occurs, the wafer comes into contact with a ring-shaped component arranged so as to cover the mounting table 204 on the outer peripheral side of the mounting surface of the wafer 203 of the mounting table 204, or due to this contact. The wafer may be damaged and cause dust generation. In some cases, the wafer may be shifted beyond a level that can be transferred by the transfer robot. Further, when the variation becomes large, the position of the wafer may be shifted beyond an allowable range in which the wafer 203 can be stably transported when the wafer 203 is pushed up and peeled off from the mounting table. In such a case, the operation of the apparatus must be stopped and the wafer must be collected, and the apparatus operating rate is greatly reduced.

  The inventors have found that the amount of displacement (movement) of the wafer 203 during such a peeling operation of the wafer 203 has a correlation with the state of the installation surface of the wafer 203. That is, by monitoring the amount of wafer misalignment that occurs during unloading, the state inside the etching chamber 106, particularly the state of the mounting table 204, can be monitored. When the wafer 203 is lifted up and the position of the center of the wafer 203 is shifted as a result of further lifting, the amount of deviation varies, and in general, when the processing is performed for a long time, the amount changes greatly. It turns out. When the etching process is continued for a long time, reaction products generated along with the etching process accumulate in the processing chamber 106. This reaction product is similarly deposited on the mounting table 204. Thereby, the property of the electrostatic adsorption film, for example, the surface roughness of the electrostatic adsorption film or the specific resistance value of the electrostatic adsorption film changes.

  The inventors continuously perform processing using an unused mounting table 204 and measure the change in the state of the mounting surface of the wafer 203 on the mounting table 204 and the amount of positional deviation when the wafer 203 is peeled off. The correlation between these was examined. As a result, it has been found that as the time used for the processing increases, the wafer 203 is likely to be misaligned, and the amount of the misalignment increases. In particular, it has been found that when the predetermined cumulative time is exceeded, the amount of deviation of the position of the wafer 203 suddenly increases, and the allowable range that can be placed and held on the hand 205 is exceeded within a short time.

  For this reason, in this embodiment, the displacement amount of the position of the wafer 203 at the time of unloading from the etching processing chamber 106 is divided into a plurality of stages according to the size, and the processing to be performed in the processing chamber according to the displacement amount. The conditions were set to restore or improve the surface of the mounting table 204.

  FIG. 4 is a diagram for explaining a process for recovering or improving the surface of the mounting table 204 based on the amount of deviation of the wafer position during unloading. First, after the wafer 203 is carried into the processing chamber, the wafer is adsorbed onto the installation surface of the mounting table 204, and in this state, an etching process is performed while supplying high-frequency power to the mounting table 204 (step 401). After the etching process is completed, static electricity is removed from the wafer 203 by plasma (step 402). Thereafter, the inside of the processing chamber is evacuated to remove unnecessary gases and products (step 403), and then the gate bubble 111 is opened to connect the buffer chamber 105 and the processing chamber (step 404).

  Next, the push-up mechanism is operated to push the wafer 203 up from the upper surface of the mounting table 204 (step 405), and the arm of the vacuum robot is extended to the space between the setting surface generated in this state and the back surface of the wafer 203. 205 is arranged (step 406). With the position of the hand 205 fixed, the push-up pin that has pushed up the wafer 203 is lowered and the wafer 203 is placed on the upper surface of the hand 205 of the vacuum transfer robot 201. Subsequently, when the push-up pin is moved further downward, the wafer 203 is left on the hand 205 and the wafer 203 is delivered (step 406).

  The vacuum transfer robot 201 that has received the wafer 203 performs an arm contraction operation and returns to the buffer chamber 105 while holding the wafer 203 on the hand 205. Thereby, the wafer 203 is unloaded from the etching chamber 106 (step 408). During the movement of the wafer 203 accompanying the arm contraction operation, the wafer 203 passes between the light emitting portion and the light receiving portion constituting the light shielding sensor 202 (step 409). At this time, the amount of misalignment of the wafer is calculated by the control device 302 based on the operating speed of the vacuum transfer robot, the light shielding time of the sensor, etc., and the amount of misalignment accompanying the unloading of the wafer 203 is calculated (step 410).

  The calculation result is compared with a preset setting value in the control device 302. Based on the comparison result, the presence or absence of the wafer 203 or the degree of the position deviation is determined, and the wafer 203 is not displaced. If it is determined that the number is small (step 411), the process proceeds to step 415.

  If it is determined in step 4111 that the wafer 203 has a positional shift, the shift amount is determined (step 412). If the shift amount is determined to be small, the high frequency power (RF bias power) is set to a small value. Plasma processing (cleaning processing) is executed (step 413). If it is determined that the amount of deviation is large, plasma processing (cleaning processing) is performed with the high-frequency power (RF bias power) set to a large value (step 414). The cleaning process may be performed using no wafer or a dummy wafer. In the cleaning process, in order to use the sputtering effect caused by the collision of ions, the magnitude of the electric power applied from the RF bias power source 305 to the wafer 203 or the mounting table 204 is adjusted to be large and small, and is supplied on the mounting table 204. The reaction product is removed.

  As described above, when the positional deviation amount of the wafer 203 is small, a process in which the RF bias power amount is set small is executed (step 413). When the positional deviation of the wafer 203 is large, the RF bi-ice power is set larger. The process is executed (step 414). As a result, even if the position of the wafer 203 is greatly shifted during unloading, the position shift of the wafer 203 during unloading is suppressed during the processing of the next wafer 203 that is actually processed. Is possible.

  When the cleaning process in step 413 or 414 is completed, the operation of the apparatus is set to a predetermined wafer processing condition, and then another wafer is processed (step 415). When it is determined that the wafer position deviation is again larger than a predetermined value after the processing of this other wafer, the occurrence of abnormality is notified by an informing means (such as an alarm display on the CRT or a buzzer sound), and this processing chamber by the apparatus is used. In this case, the cleaning process may be stopped or a cleaning process may be performed again.

  As described above, after the processing in the processing chamber, the cause of the position of the sample wafer is analyzed, and when the wafer position shift is detected based on the analysis result, the position shift depends on the degree of the position shift. A cleaning process is performed. Thereby, in the conventional technology, it is possible to suppress the occurrence of an abnormality of the apparatus that has lowered the operation rate of the apparatus due to the apparatus stop or maintenance. That is, it is possible to suppress the wafer position shift that occurs when the wafer is unloaded from the processing chamber. In addition, it is possible to reduce the wafer dropping caused by the wafer misalignment, the contact with peripheral components, or the dust generation caused by these. As a result, it is possible to lengthen work intervals for repair, maintenance, inspection, etc. for stopping the apparatus and releasing the atmosphere inside the vacuum vessel, etc., thereby improving the overall processing efficiency.

It is a figure explaining the plasma processing apparatus concerning this embodiment. It is a figure explaining the detail of an etching process chamber and a buffer chamber. FIG. 3 is a cross-sectional view of FIG. 2. It is a figure explaining the recovery or improvement process of the mounting table surface performed based on the deviation | shift amount of the wafer position in the case of carrying out.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Storage cassette 102 Cassette insertion unit 103 Atmospheric transfer unit 104,104 'Load lock chamber 105 Buffer chamber 106, 106' Etching chamber 107, 107 'Ashing chamber 111, 111' Gate valve 201 Vacuum transfer robot 202 Light shielding sensor 203 Wafer 204 Mount Table 205 Hand 301 Control device 302 Control unit 303 Control device for vacuum transfer robot 304 Air cylinder 305 High frequency bias power supply

Claims (5)

A vacuum processing chamber comprising a sample mounting table for sucking and holding the mounted sample, and a plasma generating means for generating plasma on the sample mounting table;
A sample placed in the buffer chamber and transported to the load lock chamber is placed on the sample placement table via the buffer chamber, and the processed sample placed on the sample placement table is loaded via the buffer chamber. Vacuum conveying means for conveying to,
A sample housed in the cassette is taken out and transported to the load lock chamber, and an atmospheric transport unit for storing the processed sample transported to the load lock chamber in the cassette is provided.
The sample stage includes a push-up pin that pushes the sample once onto the sample placing table and places the sample on the hand portion of the vacuum transfer means that has entered the lower part of the sample.
A plasma processing apparatus comprising a sensor for detecting a position of a sample to be carried out in a sample carrying path by the vacuum carrying means. The plasma processing apparatus according to claim 1,
A plasma processing apparatus comprising a gate valve for partitioning between the vacuum processing chamber and the buffer chamber, and a light shielding sensor for detecting the position of the sample to be carried out on the buffer chamber side of the gate valve. The plasma processing apparatus according to claim 2, wherein
A control device for controlling the entire device, the control device comprising calculation means for calculating a deviation amount between a center of the sample to be conveyed and a conveyance center of the hand unit based on an output of the light shielding sensor; A plasma processing apparatus, wherein a cleaning process is performed on the vacuum processing chamber when the amount is a predetermined value or more. A vacuum processing chamber for generating plasma on the sample mounting table and performing plasma processing on the sample mounted on the sample mounting table;
A sample placed in the buffer chamber and transported to the load lock chamber is placed on the sample placement table via the buffer chamber, and the processed sample placed on the sample placement table is loaded via the buffer chamber. Vacuum conveying means for conveying to,
A sample housed in the cassette is taken out and transported to the load lock chamber, and an atmospheric transport unit for storing the processed sample transported to the load lock chamber in the cassette is provided.
A plasma processing apparatus that once pushes a processed sample by a push-up pin onto a sample mounting table, places the sample on the hand portion of the vacuum transfer means that has entered the lower part of the sample, and transfers the placed sample to a load lock chamber In the driving method of
A plasma processing method characterized by comprising a sensor for detecting a positional deviation of a sample to be carried out in a sample conveying path by a vacuum conveying means, and performing a cleaning process on the vacuum processing chamber when the positional deviation is a predetermined value or more. How to operate the device. In the operating method of the plasma processing apparatus according to claim 4,
An operation method of a plasma processing apparatus, wherein the sensor is provided on a buffer chamber side of a gate valve that partitions a vacuum processing chamber and a buffer chamber.

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