JP4567756B2 - Heat treatment system for crystallization of amorphous silicon. - Google Patents

Description

  The present invention relates to a heat treatment system for crystallizing an amorphous silicon thin film applied when manufacturing a thin film transistor (TFT) which is a driving element of a flat panel display. More specifically, the present invention relates to a heat treatment system for crystallizing an amorphous silicon thin film, which can increase the cooling rate of a substrate after heat treatment and improve the productivity of flat plate displays.

TFTs are roughly classified into amorphous silicon TFTs and polycrystalline silicon TFTs. The characteristics of TFT are evaluated by the value of electron mobility. Since the electron mobility of the amorphous silicon TFT is about 1 cm ² / Vs, and the electron mobility of the polycrystalline silicon TFT is about 100 cm ² / Vs, in order to manufacture a high performance flat panel display, It is preferable to employ a crystalline silicon TFT. A polycrystalline silicon TFT is formed by depositing amorphous silicon on a transparent substrate such as glass or quartz to be polycrystalline, then forming a gate oxide film and a gate electrode, implanting a dopant into the source and drain, and insulating layer. It is manufactured by forming.

  An important step in manufacturing a polycrystalline silicon TFT is a step of polycrystallizing an amorphous silicon thin film. In particular, it is preferable to lower the crystallization temperature. If the crystallization temperature is very high, it becomes impossible to use a glass substrate having a low melting point for TFT production, which causes a problem of increasing the cost of TFT production. In consideration of the possibility of using such a glass substrate, in recent years, various processes have been proposed that can quickly form a polycrystalline silicon thin film at a low temperature.

  Among these, metal-induced crystallization (MIC) or metal-induced lateral crystallization (MILC) uses amorphous metal such as Ni, Cu, and Al to form amorphous silicon. It is a method for inducing crystallization, and has the advantage that it can be crystallized at a low temperature.

  The MIC method or MILC method can be broadly divided into a step of applying a metal catalyst and a step of crystallization heat treatment of amorphous silicon coated with the metal catalyst. There is a difference in process time between the two types of processes, and generally the time required for the heat treatment process is larger. In particular, the MIC method or MILC method basically has a problem of leakage current due to metal contamination, and it is necessary to reduce the amount of metal catalyst applied as much as possible. Therefore, this process time is further shortened. Such a difference in process time between the two processes leads to an undesirable result from the viewpoint of productivity. In other words, since the time required for the crystallization heat treatment process is long, the overall time required for manufacturing the LCD is increased, so that the throughput is reduced.

  The present invention, which has been made in order to solve the problems of the prior art as described above, is an amorphous silicon thin film that can increase the cooling rate of the substrate after the crystallization heat treatment and improve the productivity of the flat panel display. An object is to provide a heat treatment system for crystallization.

  In order to achieve the above-described object, the present invention provides a system for heat-treating a substrate having amorphous silicon formed on the surface thereof in order to manufacture polycrystalline silicon, and a substrate storage unit for storing the substrate And a substrate heat treatment part for heat treating the substrate, and a substrate cooling part for cooling the substrate at a speed faster than a maximum cooling rate of the substrate heat treatment part.

  The substrate is preferably a transparent substrate such as glass or quartz.

  The number of the substrates is preferably two or more.

  The substrate is preferably loaded on the substrate heat treatment unit or unloaded from the substrate heat treatment unit while being mounted on a substrate holder for supporting the substrate.

The heat treatment temperature in the substrate heat treatment part is 400 ° C. to 750 ° C., the heat treatment time is 5 minutes to 10 hours, the heat treatment atmosphere is an inert gas atmosphere such as Ar, Ne, He, N ₂ , O ₂ , N It is preferably controlled by at least one of an oxidizing gas atmosphere such as ₂ O, H ₂ O, and ozone and a reducing gas atmosphere such as H ₂ and NH ₃ .

  The substrate cooling unit includes a substrate tray that supports a substrate holder for supporting the substrate, and the substrate tray is provided with a pin that supports the substrate through a hole formed in the substrate holder. preferable.

  It is preferable that the inside of the base frame included in the substrate cooling unit is configured to allow cooling water to flow.

  The substrate cooling unit preferably includes a cooling fan unit.

  In the substrate cooling unit, it is preferable that the substrate is cooled in a state of being separated from the substrate holder for supporting the substrate.

  The cooling fan unit preferably includes a filter having a function of removing particles contained in the air.

  The heat treatment system according to the present invention for crystallizing amorphous silicon has the effect of increasing the cooling rate of the substrate after the crystallization heat treatment and improving the productivity of the flat panel display.

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

  FIG. 1 is a diagram showing an overall configuration of an amorphous silicon crystallization system according to the present invention. The amorphous silicon crystallization system 10 of the present invention includes a substrate heat treatment unit 20, a substrate cooling unit 30, and a substrate storage unit 40.

  The substrate heat treatment part 20 is a part for heat-treating a substrate on which amorphous silicon is formed for crystallizing amorphous silicon, and corresponds to a heat treatment furnace (furnace) including a heater (not shown).

  The substrate is preferably a transparent substrate such as glass and quartz, but the present invention is not limited to this. For example, when used in a manufacturing process of a semiconductor device, the substrate can be a semiconductor wafer such as a silicon wafer.

  In the case of producing polycrystalline silicon by the MIC method or MILC method, the amorphous silicon coated with the metal catalyst is heat-treated in the substrate heat treatment part. When producing polycrystalline silicon by a solid phase reaction method, pure amorphous silicon is heat-treated. The system according to the present invention is applied to all the production of polycrystalline silicon by the MIC method, MILC method, solid phase reaction method, and the like. However, the present invention will be described below using the MIC method and MILC method as examples.

The substrate heat treatment unit 20 is configured to meet the heat treatment conditions for producing polycrystalline silicon by the MIC method or MILC method. Therefore, the substrate heat treatment unit 20 is configured to be able to appropriately adjust the heat treatment temperature, the heat treatment time, the heat treatment atmosphere, and the like. Accordingly, the heat treatment temperature is 400 ° C. to 750 ° C., the heat treatment time is 5 minutes to 10 hours, the heat treatment atmosphere is an inert gas atmosphere such as Ar, Ne, He, N ₂ , O ₂ , N ₂ O, H ₂ O. It is preferable that the substrate heat treatment unit 20 is configured so as to be controlled by at least one of an oxidizing gas atmosphere such as ozone and a reducing gas atmosphere such as H ₂ and NH ₃ .

  In the present invention, the substrate heat treatment unit 20 is a batch type that can process a plurality of substrates simultaneously, but the present invention is not limited to this, and even a single wafer type that processes one substrate at a time. Good. The batch type has an advantage that the productivity is remarkably increased as compared with the single wafer type, but a substrate transfer means (not shown) and a substrate load capable of appropriately transferring and loading a plurality of substrates to the substrate heat treatment unit 20. Means (not shown) must be provided.

  The plurality of substrates are loaded into the substrate heat treatment unit 20 while being mounted on the substrate holder for heat treatment. The reason why the substrate is loaded in the substrate holder for supporting the substrate is to prevent deformation of the substrate during the heat treatment process. As the area of a flat display such as an LCD increases, the area of the substrate also increases. Therefore, if the substrate is not properly supported by the substrate holder, a phenomenon such as bending of the substrate occurs in the heat treatment process. Therefore, it is preferable to advance the heat treatment while the substrate is supported by the substrate holder, and it is more preferable to advance the heat treatment while the entire surface of the substrate is completely supported by the substrate holder. The substrate and the substrate holder will be described in more detail with reference to FIG.

  The substrate cooling unit 30 is a part that cools the substrate on which polycrystalline silicon is formed after the heat treatment process is completed in the substrate heat treatment unit 20, and corresponds to a characteristic configuration of the present invention.

  Conventionally, when the crystallization of amorphous silicon is completed, the substrate is left in the substrate heat treatment section while the heater is turned off to cool the substrate, or the substrate is taken out from the substrate heat treatment section and left in the atmosphere. The cooling method was used. However, as described above, since such a substrate cooling method requires a lot of time, there is a problem that overall productivity is lowered. That is, even if the substrate is cooled at the maximum cooling rate with the power turned off after the heat treatment in the substrate heat treatment portion is completed, there is a limit to the cooling rate. The present invention has been made to solve such problems, and the system according to the present invention includes a substrate cooling unit 30 that is different from the substrate heat treatment unit 20, and the substrate cooling rate is set to the conventional method. It is characterized by being even faster than the thing.

  FIG. 3 is a diagram illustrating an overall configuration of the substrate cooling unit 30.

  The substrate cooling unit 30 is basically a structure including a base frame 31. The interior of the frame 31 is configured to allow cooling water to flow in order to quickly cool the substrate (not shown). A cooling fan 32 is provided on the frame 31. That is, the substrate cooling unit 30 of the present invention employs a method of cooling the substrate by combining a water cooling method and an air cooling method.

  After the heat treatment is completed, the substrate 37 on which the polycrystalline silicon is formed is transferred from the substrate heat treatment unit 20 to the substrate cooling unit 30 and placed on the frame 31 of the substrate cooling unit 30. The substrate 37 placed on the frame 31 is cooled by the cooling water flowing inside the frame 31 and the cold air sent from the cooling fan 32, and reaches room temperature within a short time (for example, within 10 minutes). Since the present invention uses a method that combines a water cooling method and an air cooling method, the cooling efficiency of the substrate can be improved.

  The cooling fan 32 is preferably a fan filter unit (FFU). Generally, the FFU is provided on the ceiling of a clean room or the like, and plays a role of creating a clean room environment by forming a laminar flow below. At this time, FFU filters the particle | grains contained in the air with a filter, and blows off air with a fan. Therefore, the FFU can prevent contamination of the substrate by particles while blowing cold air into the substrate. When the cold air is blown into the substrate by the FFU, when the air is blown in the horizontal direction so that the cold air smoothly passes between the plurality of substrates 37, it is also preferable that the FFU is disposed on the side surface of the substrate.

  In the present invention, the plurality of substrates 37 are cooled while being mounted on the substrate tray 33 of the substrate cooling unit 30. In particular, the substrate 37 is cooled while being separated from the substrate holder 36.

  FIG. 3 is a diagram illustrating a state of the substrate when being cooled in the substrate tray 33 of the substrate cooling unit 30. The substrate tray 33 includes a substrate holder support base 34 and pins 35.

  After the heat treatment, the process of transferring and cooling the substrate from the substrate heat treatment unit 30 to the substrate cooling unit 30 is as follows.

  First, when the substrate heat treatment unit 30 finishes the heat treatment, after the substrate heat treatment unit 20 is turned off, the substrate heat treatment unit 20 moves the substrate 37 to a predetermined temperature (a temperature lower by 100 ° C. to 200 ° C. than the normal heat treatment temperature). Let cool naturally. This is to prevent a phenomenon that the substrate is damaged or bent due to thermal shock or the like when the substrate 37 is rapidly cooled. Thereafter, using a boat elevator (not shown) for raising and lowering the substrate boat, the substrate boat (not shown) on which the plurality of substrates 37 are mounted is lowered, and the substrate 37 is unloaded to the outside of the substrate heat treatment unit 20. . At this time, the substrate 37 is mounted on each substrate holder 36. As a result, the substrate 37 is unloaded from the substrate heat treatment unit 20 while being mounted on the substrate holder 36. As shown in FIG. 1, the substrate 37 unloaded from the substrate heat treatment unit 20 is located in a space immediately below the substrate heat treatment unit 20. Since a configuration in which a plurality of substrates are mounted on a substrate boat and loaded into the substrate heat treatment unit and unloaded from the substrate heat treatment unit by a substrate boat elevator is a known technique, detailed description thereof will be omitted.

  Next, the substrate 27 is transferred from the substrate boat (not shown) to the substrate tray 33 of the substrate cooling unit 30 while being mounted on the substrate holder 36. As the transfer means, a means (not shown) such as a substrate transfer robot is used. The substrate holder 36 is formed with a hole through which the pin 35 of the substrate tray 33 can pass. The substrate transfer robot carries the substrate holder 36 on which the substrate 37 is mounted to the substrate tray 33 and places it on the substrate holder support 34. In this process, the pin 35 of the substrate tray 33 passes through the hole of the substrate holder 36 and the substrate 37 is positioned on the pin 35. As a result, the substrate 37 is completely separated from the substrate holder 36.

  Preferably, six pins 35 per substrate 37 (that is, three on each side of the long side of the rectangular substrate) correspond to support the substrate 37 with the smallest possible area. The present invention is not limited to this.

  Thus, since the substrate 37 is separated from the substrate holder 36 and supported by the pins with a minimum area, most of the area of the substrate 37 is exposed. Therefore, the cooling efficiency of the substrate in the substrate cooling unit 30 can be further improved.

  The substrate storage unit 40 is a part where the substrate that has been cooled by the substrate cooling unit 30 is transferred and stored. The substrate transfer robot lifts the substrate 37 on the pins 35 and transfers it to the substrate storage unit 40 for storage.

  Although the system according to the present invention has been described above with a focus on the heat treatment and subsequent processes, the substrate cooling unit 30 and the substrate storage unit 40 are also used in the process of loading a plurality of substrates onto the substrate heat treatment unit 20 for heat treatment. can do. For example, the substrate cooling unit 30 may be used as a portion to which the substrate holder is mounted before the plurality of substrates 37 are loaded into the substrate heat treatment unit 20 for heat treatment. However, in such a case, it is not necessary to operate the cooling fan 32 or the like because the cooling of the substrate is unnecessary.

  For the heat treatment, the process of transferring the substrate from the substrate storage unit 40 to the substrate heat treatment unit 20 through the substrate cooling unit 30 is as follows. The substrate transfer robot takes the substrate 37 stored in the substrate storage unit 40 and places it on the pins 35 provided on the substrate tray 33 (see FIG. 3). Thereafter, when the substrate transfer robot picks up the substrate holder 36 in the substrate arrangement state shown in FIG. 3 and lifts it, the pins 35 are removed from the substrate holder 36 and the substrate 37 is naturally mounted on the substrate holder 36. Become. Thereafter, the substrate holder 36 is loaded on the substrate heat treatment unit 20 with the substrate 37 mounted thereon, and the substrate heat treatment proceeds. The substrate 37 is heat-treated in a state where the entire surface is in close contact with the substrate holder 36. This is the same as described with reference to FIG. Of course, the substrate boat and the substrate boat elevator as described above can also be used in the process of loading the substrate 37 into the substrate heat treatment unit 20.

  The heat treatment system according to the present invention for crystallization of amorphous silicon has the effect of increasing the cooling rate of the substrate after the crystallization heat treatment and improving the productivity of flat plate displays. Therefore, it can be said that the industrial applicability of the present invention is extremely high.

  While several preferred embodiments of the present invention have been described above, many changes and modifications may be made by those skilled in the art without departing from the scope and spirit of the invention as defined in the appended claims. You will understand that it is possible.

It is drawing which shows the whole structure of the amorphous-silicon crystallization system based on this invention. It is drawing which shows the structure of the board | substrate cooling part in the amorphous silicon crystallization system of FIG. It is drawing which shows the state of the board | substrate at the time of cooling in the board | substrate cooling part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Amorphous silicon crystallization system 20 Substrate heat treatment part 30 Substrate cooling part 31 Base frame 32 Cooling pen 33 Substrate tray 34 Substrate holder support stand 35 Pin 36 Substrate holder 37 Substrate 40 Substrate storage part

Claims (7)

A heat treatment system for crystallizing the amorphous silicon by heat-treating a transparent substrate having amorphous silicon formed on the surface thereof to produce polycrystalline silicon,
A substrate storage unit for storing the substrate;
A substrate heat treatment part for heat treating the substrate;
The substrate and a substrate cooling unit for cooling,
The substrate cooling unit includes a substrate tray on which a substrate holder that supports the substrate is placed. The substrate tray is provided with a plurality of pins, and the substrate holder is formed with a plurality of holes. Therefore, when the substrate holder is placed on the substrate tray, the pins pass through the holes and the substrate is supported on the pins, and the substrate is cooled while being separated from the substrate holder and the substrate. A system characterized in that the heat treatment section is cooled at a speed faster than the cooling speed when the heat treatment is stopped. The heat treatment system according to claim 1,
The system comprising two or more substrates. The heat treatment system according to claim 1,
The system board, which is characterized to be unloaded from the substrate the load on the substrate heat treatment unit in the mounted state on a substrate holder or the substrate heat treatment unit for the support. The heat treatment system according to claim 1,
The heat treatment temperature in the substrate heat treatment part is 400 ° C. to 750 ° C.
The heat treatment time is 5 minutes to 10 hours,
The heat treatment atmosphere includes an inert gas atmosphere such as Ar, Ne, He, and N ₂ , an oxidizing gas atmosphere such as O ₂ , N ₂ O, H ₂ O, and ozone, and a reducing gas such as H ₂ and NH _3. A system characterized by being controlled by at least one of the atmospheres. The heat treatment system according to claim 1,
The substrate cooling unit includes a base frame,
The base frame is configured to allow cooling water to flow therein. The heat treatment system according to claim 1,
The substrate cooling unit includes a cooling fan unit. The heat treatment system according to claim 6 ,
The cooling fan unit includes a filter having a function of removing particles contained in air.

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