JP2009094404A - Heat treatment method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat treatment method and apparatus which can thermally and uniformly treat even members as processing targets including materials having different light absorption characteristics when the processing members are thermally treated by illuminating the member with lamp light. <P>SOLUTION: In the heat treatment method, members as processing targets including at least two types of materials having different absorption characteristics of light in visible and infrared light ranges are illuminated with light which is emitted from a discharge lamp and which is passed through a filter unit for removing part of the light having predetermined wavelengths according to the different light absorption characteristics. The filter unit comprises selective reflecting mirrors for reflecting at least part of ultraviolet or visible light to pass light having a wavelength range other than the wavelengths of the ultraviolet or visible light therethrough or absorbing the light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat treatment method and a heat treatment apparatus, and more particularly to a heat treatment method, a heat treatment apparatus for a semiconductor device formed on a silicon substrate or a glass substrate, and a method for manufacturing a semiconductor device using the heat treatment apparatus.

  As a display device such as a liquid crystal display device, an active matrix display device in which a thin film transistor (TFT), which is a thin film semiconductor device, is provided for each pixel to drive a large number of pixels arranged in a matrix for each pixel. Are known. The manufacturing process of the TFT used for such applications is as follows.

  First, a semiconductor layer functioning as an active layer having a predetermined pattern is formed on a glass substrate. Next, a gate insulating film and a patterned gate electrode are sequentially formed on the semiconductor layer, and impurity ions are implanted into the semiconductor layer using the gate electrode as a mask to form a source region and a drain region.

  After the implantation of impurity ions, an interlayer insulating film is formed, and impurities in the source region and the drain region are activated by furnace furnace annealing. Next, a contact hole that reaches the semiconductor layer through the interlayer insulating film is formed, and a source electrode and a drain electrode connected to the source region and the drain region are formed in the contact hole and on the interlayer insulating film, and the TFT is formed. Is completed.

  In the TFT of the liquid crystal display device manufactured by the method as described above, element miniaturization is progressing. When the element is miniaturized, the cross-sectional area of each part through which current flows is reduced, resulting in an increase in resistance. For this reason, the resistivity of the source and drain regions varies depending on the activation state, and thus heat treatment for efficient activation is required.

  However, in the furnace furnace annealing as described above, heating for activation needs to be performed at a temperature lower than the strain point temperature of the glass substrate, and since the strain point of the glass substrate is about 670 ° C., the heating temperature must be sufficiently raised. There is a problem that the resistivity of the source and drain regions is not sufficiently lowered.

  As one method for addressing the above points and improving the activation rate, the present inventor uses a flash lamp as a light source, and irradiates the irradiated object with the lamp light instantaneously to perform the activation process. A method has been developed in which the layer absorbs light and locally raises the temperature to 1000 ° C. or higher.

  According to this method, the semiconductor layer that absorbs light can be heated to about 1400 ° C., so that the impurities contained in the polysilicon layer can be activated effectively in a short time. In this step, it was found that the semiconductor layer hardly absorbs incident light, and the glass substrate does not absorb light, so that it is not heated and does not reach 600 ° C. at which distortion occurs.

  However, it has been found that the activation heat treatment using lamp light performed in the above-described thin film transistor manufacturing process has a problem that non-uniformity occurs in the heat treatment state because the light absorption characteristics and thermal properties of the semiconductor layer and the gate electrode are different. It was. That is, since the gate electrode is made of metal, its light absorption characteristic is flat regardless of the wavelength, but the semiconductor layer made of silicon has low absorptance in the wavelength region of 600 nm or more. The radiation characteristics of the flash lamps irradiated to these gate electrodes and semiconductor layers include a wide range of light from ultraviolet light to infrared light. Therefore, temperature differences occur between the gate electrodes and the semiconductor layers, and uniform heating is performed. I can't do it.

  The present invention has been made in view of the circumstances as described above, and when performing heat treatment by irradiating lamp light, heat treatment that enables uniform heat treatment even for an object to be processed including materials having different light absorption characteristics. It is an object to provide a method and a heat treatment apparatus.

  In order to solve the above-described problem, a first aspect of the present invention is to heat-treat an object to be processed including at least two kinds of materials having different light absorption characteristics in a visible region and an infrared region by irradiating light from a discharge lamp. In this case, the heat treatment method of irradiating the object to be treated with light emitted from the discharge lamp through a filter unit that removes light having a predetermined wavelength corresponding to the absorption characteristics of the different light, the filter unit Includes a selective reflection mirror that reflects at least a part of ultraviolet light or visible light and transmits or absorbs light in other wavelength ranges.

  According to a second aspect of the present invention, when the object to be processed including at least two kinds of materials having different light absorption characteristics in the visible region and the infrared region is heat-treated by irradiation with light from the discharge lamp, A heat treatment apparatus that irradiates the object to be processed through a filter unit that removes light having a predetermined wavelength corresponding to the different light absorption characteristics, wherein the filter unit includes ultraviolet light or visible light. There is provided a heat treatment apparatus comprising a selective reflection mirror that reflects at least part of the light and transmits or absorbs light in other wavelength ranges.

  In the heat treatment method and the heat treatment apparatus according to the first and second aspects of the present invention configured as described above, a flash lamp can be used as the discharge lamp. The at least two kinds of materials having different light absorption characteristics may include a semiconductor and a metal. As the object to be processed, a semiconductor thin film pattern and a metal thin film pattern formed on a glass substrate can be used.

  A third aspect of the present invention includes a step of forming a semiconductor film on a substrate, a step of forming a gate insulating film on the substrate including the semiconductor film, a step of forming a gate electrode on the gate insulating film, A step of implanting impurities into the semiconductor film using a gate electrode as a mask; and a step of activating the impurities in the semiconductor film by performing a heat treatment on the semiconductor film using the heat treatment apparatus described above. A method for manufacturing a semiconductor device is provided.

  According to the present invention, when heat treatment is performed by irradiating light from a discharge lamp, light is irradiated through a filter unit including a selective reflection mirror that removes light of a predetermined wavelength, so that light in the visible region and infrared region can be emitted. Even when an object to be processed containing at least two kinds of materials having different absorption characteristics is heat-treated, it is possible to irradiate light with controlled relative light intensity corresponding to different light absorption characteristics, and uniform heat treatment is realized. The

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

  A heat treatment method and a heat treatment apparatus according to an embodiment of the present invention provide a discharge lamp because the materials constituting the metal gate electrode and the semiconductor layer constituting the element pattern have different light absorption characteristics in the visible region and the infrared region. The problem is that when heat treatment is performed by irradiating light from the two, there is a difference in temperature between the two, and uniform heat treatment cannot be performed. This is solved by irradiating light through a filter unit having a reflecting mirror.

  According to such a heat treatment method and heat treatment apparatus, the heating temperature of the gate electrode and the semiconductor layer having different light absorption characteristics in the visible region and the infrared region can be adjusted by adjusting the band of light to be removed and the degree of removal in the filter unit. The relative intensity can be changed, and the heating state of both can be made uniform.

  FIG. 1 is a diagram showing an outline of a heat treatment apparatus according to the first embodiment of the present invention. In FIG. 1, a processing table 3 that holds an object to be processed 2 in a predetermined position is disposed in an airtight container 1. A selective reflection mirror 15 is provided in the upper part of the hermetic container 1 as means for changing the irradiation intensity of the visible light and infrared light portions. The selective reflection mirror 15 is formed by forming a dielectric multilayer mirror on an optical glass substrate that transmits infrared light. A reflector 16 is disposed between the flash lamp 3 and the object 7 so that the light 7 emitted from the flash lamp 3 is not directly irradiated onto the object 7. The light incident on the selective reflection mirror 15 directly from the flash lamp 3 or after being reflected by the reflector 16 transmits part of the visible light and infrared light through the selective reflection mirror 15, and the reflected ultraviolet light and visible light. A part of reaches the object 7 to be processed.

  In the present embodiment, the lamp unit 6 is disposed in the hermetic container 1, but the lamp unit 6 is disposed outside the hermetic container 1, and an opening is provided on the surface of the hermetic container 1 facing the lamp unit 6. Alternatively, the opening may be sealed with a plate made of a material that transmits light from the flash lamp 4 such as quartz glass, and the object to be processed 2 may be irradiated with light through the opening.

  Considering a process of forming a thin film transistor on a glass substrate, the object 2 is composed of a glass substrate 11, a silicon pattern 12, a gate insulating film 13, and a gate electrode 14 made of metal.

  FIG. 2 is a characteristic diagram showing the radiation characteristic a of the flash lamp 4, the absorption characteristic b of the silicon pattern 12, and the absorption characteristic c of the gate electrode 13. As shown in FIG. 2, the radiation characteristic a of the flash lamp 4 includes light having a wide wavelength from ultraviolet light to infrared light. On the other hand, the absorption characteristic b of the silicon pattern 12 has a low absorption rate in a wavelength region of 600 nm or more. The absorption characteristic c of the gate electrode 13 made of metal is relatively flat from the ultraviolet region to the infrared region.

  From the characteristics shown in FIG. 2, the heating state of the silicon pattern 12 is changed by changing the irradiation intensity of visible light and infrared light, for example, light having a wavelength longer than 600 nm, of the emitted light of the flash lamp 4. It can be seen that the heating state of the gate electrode 13 can be controlled with little influence.

  Therefore, in this embodiment, the selective reflection mirror 15 is used as means for changing the irradiation intensity of the visible light and infrared light portions. The selective reflection mirror 15 is formed by forming a dielectric multilayer mirror on an optical glass substrate that transmits infrared light. A reflector 16 is disposed between the flash lamp 3 and the object 7 so that the light 7 emitted from the flash lamp 3 is not directly irradiated onto the object 7. The light incident on the selective reflection mirror 15 directly from the flash lamp 3 or after being reflected by the reflector 16 transmits part of the visible light and infrared light through the selective reflection mirror 15, and the reflected ultraviolet light and visible light. A part of reaches the object 7 to be processed. If such a selective reflection mirror 15 is used, the configuration is more complicated than that of the first embodiment, but the loss of light in the selectively reflected band can be prevented.

  In this embodiment, the lamp unit 6 including the selective reflection mirror 15 is disposed in the airtight container 1. However, the lamp unit 6 is disposed outside the airtight container 1 and faces the lamp unit 6 of the airtight container 1. An opening may be provided on the surface to be processed, and the opening may be sealed with a plate made of a material that transmits light from the flash lamp 4 such as quartz glass, and the object 2 may be irradiated with light through the opening.

  By using the heat treatment apparatus as shown in FIG. 1 described above, the relative intensity of the heated state by light between different materials can be adjusted, and uniform heat treatment can be realized.

  Next, an embodiment in which the heat treatment using the heat treatment apparatus described above is applied to the activation process of the source / drain regions will be described.

FIG. 3 is a cross-sectional view of the semiconductor device for explaining the object to be processed 2 shown in FIG. In FIG. 3, a base insulating film 22 made of, for example, SiO ₂ is formed on a substrate, for example, a 2 m square glass substrate 21 by plasma CVD to prevent the permeation of impurities from the substrate 21. . On the base insulating film 22, a non-single-crystal semiconductor thin film such as an amorphous silicon film is formed by a plasma CVD method. This amorphous silicon film is irradiated with energy light for crystallization to be polycrystallized, and then plasma etched by leaving a pattern at a position where a predetermined TFT is formed as a mask to form an island shape. The polycrystalline semiconductor thin film 23 is processed.

On the island-like polycrystalline semiconductor thin film 23 and the exposed base insulating film 22, a gate insulating film 24 made of, for example, SiO ₂ is formed by plasma CVD. A conductor for forming a gate electrode, for example, a molybdenum-tungsten alloy thin film is formed on the gate insulating film 24 by a sputtering method, and a pattern at a position where a predetermined TFT is to be formed is left in an island shape as a mask. The gate electrode 25 is formed by plasma etching. Impurity implantation for forming source and drain regions in the island-like polycrystalline semiconductor thin film 23 is performed using the gate electrode 25 as a mask. In order to activate these impurities, heat treatment is performed by the heat treatment apparatus shown in FIG.

  First, the substrate to be processed after impurities are implanted into the source / drain regions of the semiconductor thin film described above is aligned in the hermetic container 1 and carried into a predetermined position of the support 3. In order to prevent the gate electrode 25 from being oxidized during light irradiation, an inert gas such as nitrogen is introduced into the hermetic container 1. Next, drive power for driving the flash lamp 4 is applied, the flash lamp 4 is turned on, and heat treatment by light irradiation is performed via the selective reflection mirror 15.

  As the selective reflection mirror 15, a dielectric multilayer mirror that transmits a part of visible light and infrared light and reflects a part of visible light and ultraviolet light can be used.

  As the plurality of flash lamps 4 constituting the lamp unit 6, for example, rod-shaped xenon flash lamps can be used. A xenon flash lamp is a quartz glass tube in which xenon gas is sealed inside, an anode and a cathode connected to a capacitor are disposed at both ends, and a trigger electrode is disposed near the outer wall of the glass tube. When high voltage is applied, part of the xenon gas in the glass tube is ionized and the insulation between the anode and cathode is broken, so that the charge stored in the capacitor of the drive power circuit flows between the anode and cathode as a current. Light is emitted by exciting the xenon gas in the tube.

  The emission wavelength range of the flash lamp light ranges from the ultraviolet range to the infrared range, and the emission time is 0.1 ms to 100 ms.

  When the xenon flash lamp 4 is turned on, the substrate 2 to be processed is instantaneously irradiated through the band elimination filter 7 or the selective reflection mirror 15 to perform an efficient annealing process in a short time. Can be activated.

  When the lamp unit 6 irradiates the object to be processed shown in FIG. 3 with light, the island-like polycrystalline semiconductor thin film 23 that absorbs light can be heated to about 1400 ° C. In this case, since the infrared wavelength is removed by the band elimination filter 7 or the selective reflection mirror 15, the temperature rises and falls below the temperature of the gate electrode 25 made of a metal that absorbs the infrared wavelength, for example, molybdenum silicide. As a result, it is possible to uniformly activate the impurities contained in the island-shaped polycrystalline semiconductor thin film 23 in a short time. In this case, since the glass substrate 21 does not absorb light, it is not heated and does not reach 600 ° C., which causes distortion.

  In this way, the activation process is completed. You may perform this process in multiple times as 1 period. The object 2 to be processed after the activation process is carried out of the hermetic container 1.

  Next, a method for manufacturing a thin film transistor (TFT) for driving a liquid crystal display device in which impurities contained in the polycrystalline semiconductor thin film 23 are activated using the heat treatment apparatus described above will be described. 4 and 5 are cross-sectional views showing the method of manufacturing the thin film transistor (TFT) in the order of steps.

First, a substrate to be processed 31 is prepared. In this embodiment, a substrate in which a base insulating layer 33 made of SiO ₂ is formed on a glass substrate 32 is used as the substrate to be processed 31. An amorphous silicon layer 34 is formed on substantially the entire surface of the glass substrate 31 (on the base insulating layer 33) so as to have a layer thickness of, for example, 50 nm. Thereafter, an annealing process is performed in an atmosphere at a temperature of 500 ° C. to release hydrogen in the amorphous silicon layer 34 (FIG. 4A).

  Next, the amorphous silicon layer 34 is crystallized to form a polysilicon layer 35 by, for example, ELA (Excimer Laser Anneal) method (FIG. 4B).

  Next, a resist mask having a predetermined shape is formed on the polysilicon layer 35 by PEP (Photo Engraving Process, so-called photolithography), and the polysilicon layer 35 is formed by CDE (Chemical Dry Etching) using the resist mask as a mask. Etching is performed to process the polysilicon layer 35 into an island shape (FIG. 4C).

Thereafter, a gate made of SiO _{2 is used} to cover the polysilicon layer (island-like polycrystalline semiconductor thin film) 35 and the base insulating layer 33 processed into an island shape by using PE-CVD (Plasma Enhanced Chemical Vapor Deposition) method. An insulating film 36 is formed (FIG. 4D).

  Next, a metal layer, for example, a molybdenum tungsten layer 37 is formed on substantially the entire surface of the gate insulating film 36 (FIG. 5A). Then, after forming a resist mask having a predetermined shape on the molybdenum tungsten layer 37 by PEP, unnecessary portions of the molybdenum tungsten layer are removed by a reactive ion etching method using the resist mask as a mask to form the gate electrode 38. (FIG. 5B).

  Next, using the gate electrode layer 38 as a mask, impurity ions (such as phosphorus or boron) are implanted into the polysilicon layer 35 to form impurity regions, for example, a source region and a drain region (FIG. 5C).

  Thereafter, using the heat treatment apparatus shown in FIG. 1, the structure shown in FIG. 5 (d) is heat-treated by light heating by the lamp unit 6 to activate the impurities contained in the polysilicon layer 35, and the source region and the drain region are formed. Form.

Next, an interlayer insulating film 39 made of SiO ₂ is formed on the entire surface (FIG. 5D).

  After that, according to a normal thin film transistor manufacturing process, a contact hole is formed so as to expose a part of the source region and a part of the drain region, and then a metal wiring layer is formed so as to fill the contact hole and patterned. Thus, the source electrode and the drain electrode are formed, and the TFT is completed.

  In the TFT for driving the liquid crystal display device manufactured as described above, the polysilicon unit 35 can be heated uniformly because the light heating is performed by the lamp unit 6 through the selective reflection mirror 15. Impurities in the silicon layer 35 can be activated efficiently.

Sectional drawing which shows the heat processing apparatus which concerns on the 1st Embodiment of this invention. The characteristic view which shows the radiation | emission characteristic of a flash lamp, and the absorption characteristic of a silicon | silicone and molybdenum silicide, respectively. FIG. 10 is a cross-sectional view of a semiconductor device for illustrating an object to be processed. Sectional drawing which shows the manufacturing method of a thin-film transistor (TFT) in order of a process. Sectional drawing which shows the manufacturing method of a thin-film transistor (TFT) in order of a process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Airtight container, 2 ... To-be-processed object, 3 ... Processing stand, 4 ... Flash lamp, 5,16 ... Reflector, 6 ... Lamp unit, 11 ... Glass substrate, 12 ... Silicon pattern, 13 ... Gate insulating film, 14 ... Gate electrode 15, selective reflection mirror 21, 32, glass substrate 22, 33, base insulating film 23, island-like polycrystalline semiconductor thin film 24, 36 gate insulating film 25 , 38 ... gate electrodes, 26, 39 ... interlayer insulating layers, 35 ... polysilicon layers.

Claims (6)

  When the object to be processed including at least two kinds of materials having different light absorption characteristics in the visible region and the infrared region is irradiated with light from the discharge lamp, the light emitted from the discharge lamp is converted into the different light. A heat treatment method of irradiating the object to be processed through a filter unit that removes light of a predetermined wavelength corresponding to the absorption characteristics of the filter, wherein the filter unit reflects at least part of ultraviolet light or visible light, and the like. A heat treatment method comprising a selective reflection mirror that transmits or absorbs light in the wavelength range of.   The heat treatment method according to claim 1, wherein the discharge lamp is a flash lamp.   The heat treatment method according to claim 1, wherein the at least two kinds of materials having different light absorption characteristics include a semiconductor and a metal.   The heat treatment method according to claim 1, wherein the object to be processed is a semiconductor thin film pattern and a metal thin film pattern formed on a glass substrate.   When heat-treating an object to be processed containing at least two kinds of materials having different light absorption characteristics in the visible region and the infrared region by irradiation with light from the discharge lamp, the light emitted from the discharge lamp is converted into the different light. A heat treatment apparatus that irradiates the object to be processed through a filter unit that removes light of a predetermined wavelength corresponding to the absorption characteristic of the filter, wherein the filter unit reflects at least part of ultraviolet light or visible light, and the like. A heat treatment apparatus comprising a selective reflection mirror that transmits or absorbs light in the wavelength range of. Forming a semiconductor film on the substrate;
Forming a gate insulating film on the substrate including the semiconductor film;
Forming a gate electrode on the gate insulating film;
Injecting impurities into the semiconductor film using the gate electrode as a mask, and heat-treating the semiconductor film using the heat treatment apparatus according to claim 5 to activate the impurities in the semiconductor film. A method of manufacturing a semiconductor device.

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