JP2000200783A - Apparatus and method for plasma treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor a plasma treatment surely and precisely by a method wherein a plasma treatment apparatus is provided with an optical fiber so that the formation of a film on a substrate by the plasma treatment, and the state of an etching operation are observed directly. SOLUTION: A window 8 as a transparent member which is used to observe a film formed on a substrate 4 from the rear side of the substrate 4 is formed in a substrate holder 3. An optical fiber 9 is installed on the rear side. Magnesium fluoride is used as a material for the window 8. A fine aluminum alloy mesh is formed on the surface so as to eliminate the influence on a potential on the surface of the substrate 4 due to the window 8. The glass substrate 4 is placed on the substrate holder 3, and a silicon nitride film is formed by a plasma CVD operation. Light which is irradiated from the rear of the substrate 4 through the optical fiber 9 is reflected by the surface so as to be returned to the optical fiber 9. The light causes an interference by a film which is being formed, and the color of the reflected light is changed. It is fetched as a color image by a color image input device 10 so as to be digitally processed by an image information processor 11. Then, it is changed into a numerical value as the intensity of three primary colors of red, green and blue.

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 such as a plasma CVD apparatus and a dry etching apparatus used for manufacturing a liquid crystal display device or a semiconductor integrated circuit having a thin film transistor, and more particularly to monitoring a vacuum plasma process. About technology.

[0002]

2. Description of the Related Art In a process of manufacturing a large-scale integrated circuit or a liquid crystal display device equipped with a thin film transistor, a plasma processing process of forming or etching a thin film using vacuum discharge such as plasma CVD or dry etching. Are heavily used.

In each process, a substrate temperature, a degree of vacuum,
Monitor the flow of raw material gas and etching gas, the input (input power) from the high frequency power supply for generating plasma, the intensity of reflected wave, the state of impedance matching, etc., and monitor whether the process is normal. To stabilize production.

[0004]

However, these monitors are related to process conditions, and are not indirect monitors because they are not monitors of a film actually formed on a substrate or a state of etching itself. It is generally recognized that these monitors are inadequate.

[0005] In addition to these, in plasma CVD, attempts have been made to mount a film thickness gauge on a plasma processing apparatus (see Japanese Patent Application Laid-Open No. 9-143743).

The film thickness gauge in plasma CVD is exposed to high temperature and high frequency, so it has to be optical type.
The film adheres strongly to the monitor window, making it difficult to accurately measure the film thickness, making mass production and practical use difficult.

In dry etching, an emission spectrum from plasma is measured as an end point monitor for etching. However, this luminescence monitor does not always monitor the substrate itself, but it is difficult to accurately monitor whether the plasma processing is performed correctly, and it has been difficult to put it to practical use.

Further, in the thin film process for manufacturing a large-scale integrated circuit or a thin film transistor, dust is disliked. Therefore, it is common to provide an advanced clean room and perform the manufacturing in the clean room. Is dust from human beings, and the dust that occurs when a person disturbs airflow and rolls up dust. Therefore, at these manufacturing sites, there is a tendency to eliminate opportunities for human intervention as much as possible, advance automation, and become unmanned. For this reason, in the past, there has been an increasing number of cases where abnormalities that could be found by direct observation of the substrate by direct observation of the substrate during production can no longer be found, or the discovery is delayed, and a large number of defective products are generated. .

SUMMARY OF THE INVENTION An object of the present invention is to directly and easily take in information of a film to be formed or dry-etched on a substrate by plasma processing, and to reliably and accurately monitor whether or not the plasma processing is properly performed on the substrate. It is an object of the present invention to provide a plasma processing apparatus and method capable of performing the above-described processes.

[0010]

According to the present invention, an optical fiber is provided in a plasma processing apparatus so that a state in which a film is formed on a substrate by plasma processing or a film is etched can be directly observed. Is the gist.

However, if the optical fiber is placed in a place where the substrate surface can be observed, the optical fiber is exposed to the plasma during the plasma processing, and a film is formed on the light entrance portion of the optical fiber or the optical fiber is corroded. The backside of the substrate that is not exposed is the best location. For example, a small hole is provided in a holder (support stand, susceptor) holding a substrate, a transparent window is provided in the hole, and the substrate is observed from behind by an optical fiber through this window. In a liquid crystal display element for forming a thin film transistor, since a transparent material such as transparent glass is used as a substrate, the surface to be processed can be observed from the back side through the substrate. On the other hand, in a large-scale integrated circuit or the like, the substrate is opaque such as a silicon wafer. However, also in this case, there is a region through which light is transmitted in the infrared region, and it is possible to use infrared light in this region. Recently, integrated circuits have been made by growing crystals on transparent substrates such as glass, quartz, and diamond.
In such a case, it is of course possible to observe through the substrate.

Although the area for taking in an image through an optical fiber is limited to an extremely narrow area, the color, shape, reflected light intensity and the like can be displayed on a display screen and observed. Further, image information processing for digitizing image information is performed,
For a transparent material, the change in film thickness can be estimated. It is not necessary to quantitatively determine the film thickness by a numerical value, but it is sufficient to confirm that the progress of the process is progressing as planned. Since the change in color captured as image information is the data of the received light intensity of each of the three primary colors, if the time change is tracked, it can be used for process management as a parameter that changes in accordance with the progress of the process. Becomes If the progress of the process is correctly performed, the change repeats almost the same change. Therefore, if the change is the same as the previous pattern, it can be determined that the pattern is normal. If the change is slow, the progress of the process is slow, that is, the film formation rate and the etching rate are slow. If the change is completely different, it means that a different phenomenon is occurring. In either case, it can be detected as abnormal, and it works well as process monitoring.

Also, a film made of an opaque material such as a metal film can be used for detecting the end point of etching based on information from the substrate. That is, the point where the film disappears and becomes transparent may be determined as the end point. The emission of the plasma transmitted through the substrate may be observed, or the reflected light may be observed by inputting light from a fiber.
In the case of reflected light, the reflected light becomes weak at the end point.

When a hole is formed in the holder as an electrode, and a window or an optical fiber is placed in the hole as described above, the potential of the portion is different, so that the etching and film forming speeds are different from those of the other portions. Therefore, it is desirable to impart conductivity to the window provided in the holder. For example, the upper surface of the window material whose hole is covered may be covered with a transparent conductive film, or may be covered with a fine mesh pattern made of a conductive material.
By establishing continuity between the transparent conductive film or conductive mesh and the surface of the holder and setting both of them to the same potential, the speed of etching and film formation in the window can be made uniform with other places.

In the case of CVD or the like, the holder temperature is 300 ° C.
It may reach more than this. Therefore, in this case, it is necessary to use an optical fiber having a heat-resistant temperature of 300 ° C. or higher. In addition, fluorine plasma processing that is common in dry cleaning such as etching and plasma CVD requires fluorine plasma processing resistance. The heat resistance of the optical fiber is 30
There is no problem because it withstands 0 ° C. sufficiently, but the fluorine plasma resistance is not sufficient. Therefore, it is desirable to take measures such as sealing the optical fiber and sealing with an inert gas so as not to be exposed to fluorine radicals.

The portion to be observed via the optical fiber may be a portion having a pattern necessary for the product, or a pattern dedicated to observation convenient for observation may be separately provided. As a pattern for observation, for example, half of the observation window is covered with a metal film to cause strong reflection, and a method of evaluating the relative reflected light intensity or transmitted light intensity by comparing with a part to observe the film surface or For comparison, there is a method in which a portion without a pattern is formed, and a state in which a film is formed is simply observed with reflected light or transmitted light. In addition, for etching, for example, an easy-to-understand pattern is made to appear at the end point of etching, or if half etching is necessary, a pattern is formed so that only half of the part visible from the window is etched, and it is not made a part to be etched There is a method of observing and evaluating by comparing parts.

Although only one optical fiber may be provided, it is desirable to provide a plurality of optical fibers if possible, so that variations in plasma processing, for example, at the center and the periphery can be evaluated. By providing a plurality of optical fibers, it is possible to cope with multi-product production.

Although it is effective for a person to view and observe the image obtained through the optical fiber and to control the process, the production of semiconductors and liquid crystal display elements is often carried out all day and night, so that automation is preferred. Is desirable. For that purpose, the captured image is processed so that the computer can detect the end point or the abnormality. Available image processing technologies include, for example, processing technology for correcting images, such as removing noise on hardware that captures images and regular signals generated by hardware, and extracting contours and lines from captured images. Processing technology to identify the pattern to be measured and recognize the place to be measured, processing to capture the time-varying pattern of the reflected and transmitted light intensities at the place to be measured, or processing to compare specific points of the pattern And the like. By these processes, the image data is converted into simple numerical data suitable for computer processing, and the process end point management and the process abnormality judgment can be automatically performed.

In this way, when the end point of the process or the process abnormality is determined, for example, the operation to be performed next is programmed in advance, and a signal is sent to the controller of the plasma processing apparatus, so that the detailed process can be performed. Management becomes possible.

Although the end of the process by detecting the end point has already been put to practical use in a dry etching apparatus or the like, according to the present invention, for example, from the information that the film becomes thinner and the transmitted light intensity increases, the end point of the process is close. If you can reduce the discharge power and leave the etched surface with less damage, terminate the process, or perform low-power deposition until some film is formed even in CVD, and confirm that the film is attached. It is possible to perform more detailed management than the conventionally performed control of feeding back information obtained by a monitor to process conditions, such as increasing the power and forming a film at a high speed.

In the actual operation, the type of process abnormality and
By accumulating the correspondence of the combination of abnormal values of numerical data as data, when an abnormal value occurs, it becomes possible to determine what kind of process abnormality has occurred based on the pattern of the appearance of the abnormal value.

That is, the plasma processing apparatus of the present invention comprises:
A vacuum container, a unit for exhausting the inside of the container, a unit for introducing a plasma processing gas into the container, an electrode for discharge, a holder for holding a substrate to be subjected to plasma processing, and emission of light into the container. And an optical fiber provided with at least a leading end for taking in the light.

A vacuum vessel; means for evacuating the vessel; means for introducing a plasma processing gas into the vessel; a discharge electrode; a holder for holding a substrate to be plasma-processed; A window portion provided in the substrate mounting portion of
Emission of light under the window portion, an optical fiber provided with a tip portion for performing at least capturing among capturing, a unit for capturing an image as an electric signal, a unit for processing information of the image, and a unit for displaying the image Means for sending a signal to the controller of the plasma processing apparatus based on the result of the information processing.

The signal sent to the controller may be a signal for increasing or decreasing discharge power, a signal for stopping supply of discharge power, or a signal for notifying the end of the process.

Further, the upper surface of the window is covered with a transparent conductive film or a mesh made of a conductive material, and the window is electrically equipotential with the holder.

Further, the window is made of a fluorine plasma resistant material such as MgF ₂ or LiF.

Further, the image information is digitized and image information processing is performed, and when the pattern shape resulting from the plasma processing is within a specified range, the process end point is determined, or it is determined that the process proceeds normally. It is characterized by.

Further, a temporal change pattern of a parameter obtained by processing the information of the image is accumulated and averaged to obtain a typical example of the progress of the plasma processing. Is determined.

[0029] In addition, including the window portion and the optical fiber,
The heat resistance of a portion installed in the container is 300 ° C. or higher.

Further, the window and the optical fiber disposed thereunder are provided at a plurality of positions of the substrate mounting portion of the holder.

Further, the plasma processing method of the present invention is characterized in that the front side of the substrate to be subjected to plasma processing is observed through the substrate from the back side.

Further, a special pattern for comparison monitoring is provided on a portion of the substrate to be observed.

[0033]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the drawings described below, those having the same functions are denoted by the same reference numerals, and the repeated description thereof will be omitted. The process monitor according to the following embodiments is characterized in that process abnormalities can be classified for each change pattern by accumulating soft data.

Embodiment 1 Embodiment 1 is an example in which the present invention is applied to a case where a silicon nitride film is formed on a glass substrate for manufacturing a liquid crystal display element by plasma CVD.

FIG. 1 shows plasma CVD according to the first embodiment.
It is a figure showing the outline of a device.

Reference numeral 1 denotes a vacuum vessel, 2 denotes a cathode electrode, 3 denotes a substrate holder (support base, susceptor), 4 denotes a transparent glass substrate for producing a liquid crystal display element, for example, 5 denotes a material gas, 6 denotes vacuum evacuation, and 7 denotes high frequency. A power supply, 8 is a substrate observation window provided in the substrate holder 3, 9 is an optical fiber, 10 is a color image input device such as a color image pickup tube, 13 is a reference color image input device, 11
Denotes an image information processing device, and 12 denotes an image display device.

The substrate 4 is placed on the substrate holder 3 from behind the substrate 4.
A window 8 made of a transparent member is provided so that the film provided on the substrate 4 can be observed through the optical fiber, and an optical fiber 9 is provided behind the window 8. The window 8 is made of, for example, magnesium fluoride, and a fine aluminum alloy mesh is formed on the surface (upper surface) of the window 8 so that the window 8 does not affect the surface potential of the substrate 4. A glass substrate 4 was placed on the substrate holder 3, and a silicon nitride film was formed by plasma CVD.

The light emitted from the back surface of the substrate 4 through the optical fiber 9 is reflected on the surface of the substrate 4 and returns to the optical fiber 9, but causes interference in the film being formed, and the color of the reflected light is changed. Change.

When the image is taken as a color image by the color image input device 10 and digitally processed by the image information processing device 11, the intensity is converted into a numerical value as the intensity of the three primary colors of red, green and blue light.

FIG. 2 is a diagram showing an example of how the intensity of the reflected light of the three primary colors changes at that time. The horizontal axis represents the film forming time, and the vertical axis represents the reflected light intensity.

By recording the temporal change of the reflected light intensity accompanying such film formation and comparing it with a typical change, it can be determined whether or not the film formation is performed normally. A slow change corresponds to a low deposition rate, and a decrease in the fluctuation width corresponds to an abnormality in which the film becomes turbid.

When the process proceeds normally and reaches a point to be an end point, a process end signal may be sent to a controller of the plasma processing apparatus to end the process. In the case of an abnormality, an alarm may be issued to notify the abnormality.

This method is also effective when continuously forming different types of films. For example, when the amorphous silicon film is formed on the upper layer, the film forming speed and film abnormality can be similarly detected from the monitor color change abnormality.

When monitoring the interference color of such a film,
The part to be observed must be able to pass light,
There must be no opaque patterns such as wiring. Therefore, at the stage of designing the wiring pattern, it is necessary to make sure that there is no opaque pattern such as wiring in the observation window.
In addition, the observation window must be provided at a portion where wiring and other patterns do not come, such as at the end of the substrate or between the patterns. You may.

Embodiment 2 Embodiment 2 is an example in which the present invention is applied to dry etching of a metal film.

FIG. 3 is a diagram showing an outline of the dry etching apparatus according to the second embodiment.

The material of the window 8 provided in the substrate holder 3 was a material in which the surface (upper surface) of quartz glass was covered with a transparent conductive film of indium and tin oxide (indium tin oxide). In the second embodiment, the product metal film pattern is observed, and the moment when the plasma emission is transmitted is monitored and set as the end point, thereby providing a highly sensitive endpoint monitor. In the contour extraction pattern recognition, a point at which the contrast has been binarized is detected as the end point of the etching.

When the end point is detected, an end point signal is sent to the plasma processing apparatus, or a signal is sent with a delay of the overetch time to end the process.

It is also possible to monitor the processing width of a pattern formed by image processing. If the processing width does not meet the standard, an alarm is issued to notify the abnormality.

By arranging a plurality of observation points, it is possible to cope with many kinds and to obtain an in-plane distribution of the processing accuracy. This is stored as quality control data, and if any of the data does not conform to the standard, an alarm is also issued to notify the abnormality.

Embodiment 3 Embodiment 3 is an example in which the present invention is applied to etching of an n ⁺ impurity layer of amorphous silicon of a thin film transistor.

As a constituent material of the window 8 provided on the substrate holder 3 shown in FIG. 3, a quartz glass surface coated with a transparent conductive film of indium and tin oxide (indium tin oxide) was used.

FIG. 4 is a diagram showing an example of the test pattern according to the third embodiment.

In the third embodiment, only a half of the field of view from the window 8 is etched, as shown in FIG.
And a test pattern 13 comprising 13b, and monitoring that the film disappeared by half of the visual field due to etching.

The Naf line monochromatic light is irradiated from the optical fiber 9, and the progress of the etching is monitored from the change in the contrast of the reflected light intensity between the etched portion 13a and the non-etched portion 13b, and the end point is accurately detected. I was able to.

When the end point is detected, an end point signal is sent to the controller of the plasma processing apparatus to end the process. The method of the present invention is very effective for such a process in which the film is partially etched and stopped.

Although the present invention has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments, and it is needless to say that various changes can be made without departing from the gist of the present invention. It is. For example, in the above embodiment, one optical fiber 9 is used, but a fiberscope formed by bundling a plurality of optical fibers may be used.

[0058]

As described above, according to the present invention,
Direct information on film formation and etching performed on the substrate can be obtained, and by monitoring the film formation and etching processes, the process can be performed more reliably and accurately. ,
This is effective in improving reliability.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a plasma CVD apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of how the intensity of reflected light of three primary colors changes with the film formation time.

FIG. 3 is a diagram showing an outline of a plasma CVD apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an example of a test pattern according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 2 ... Cathode electrode, 3 ... Substrate holder, 4
... substrate, 5 ... material gas, 6 ... vacuum exhaust, 7 ... high frequency power supply, 8 ... substrate observation window, 9 ... optical fiber, 10 ... color image input device, 11 ... image information processing device, 12 ... image display device, 13 ... Reference color image input device.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05H 1/46 H01L 21/302 BF Term (Reference) 4K030 FA01 KA37 KA39 KA41 KA46 KA49 4K057 DA14 DA16 DA19 DD01 DJ10 DM02 5F004 AA16 BA04 BB02 BB18 BC08 CA09 CB09 5F045 AA08 BB10 EB03 EH04 EH08 EH14 EH19 GB09 GB10 GB17

Claims (12)

[Claims] 1. A vacuum vessel, means for evacuating the vessel, means for introducing a plasma processing gas into the vessel, electrodes for discharge, a holder for holding a substrate to be plasma-processed, and the vessel An optical fiber in which a tip portion for taking at least one of light emission and capture is disposed. 2. A vacuum vessel, means for evacuating the vessel, means for introducing a plasma processing gas into the vessel, an electrode for discharge, a holder for holding a substrate to be plasma-processed, and the holder A window portion provided on the substrate mounting portion, an optical fiber provided with a tip portion for performing at least capture of light emission and capture below the window portion, a means for capturing an image as an electric signal, and image information , A means for displaying an image, and a means for sending a signal to a controller of the plasma processing apparatus based on a result of the information processing. 3. The plasma processing according to claim 2, wherein the signal sent to the controller is a signal for instructing an increase or a decrease in discharge power, a signal for instructing a stop of the supply of discharge power, or a signal notifying the end of the process. apparatus. 4. The plasma according to claim 2, wherein the upper surface of the window is covered with a transparent conductive film or a mesh made of a conductive material, and the window is electrically equipotential with the holder. Processing equipment. 5. The plasma processing apparatus according to claim 2, wherein said window portion is made of a fluorine plasma resistant material. 6. The plasma processing apparatus according to claim 5, wherein said fluorine plasma resistant material is MgF ₂ or LiF. 7. A method according to claim 1, wherein the information of the image is digitized to perform image information processing, and the end of the process is determined when the pattern shape resulting from the plasma processing is within a specified range, or it is determined that the process proceeds normally. 3. The plasma processing apparatus according to claim 2, wherein: 8. A typical example of the progress of the plasma processing is obtained by accumulating and averaging a temporal change pattern of a parameter obtained by processing the information of the image, and comparing with this, an abnormality of the plasma processing is obtained. The plasma processing apparatus according to claim 2, wherein the determination is made. 9. The plasma processing apparatus according to claim 2, wherein a portion including the window and the optical fiber, which is provided in the container, has a heat resistance of 300 ° C. or more. 10. A method according to claim 10, wherein:
3. The plasma processing apparatus according to claim 2, further comprising: the window and the optical fiber disposed below the window. 11. A plasma processing method comprising observing the front side of a substrate to be subjected to plasma processing from the back surface of the substrate through the substrate. 12. A special pattern for comparison monitoring is provided on a portion of the substrate to be observed.
The plasma processing method as described above.