JP2008283066A - Apparatus and method for heat treatment for activation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an activating heat treatment apparatus and a heat treatment method which can perform uniform heat treatment by irradiating a treatment target with light of a required intensity distribution without generating deformation or distortion in a mask member. <P>SOLUTION: The activating heat treatment apparatus is provided with a holding stand for holding the treatment target, a lamp unit for performing the heat treatment of the treatment target by irradiating the treatment target with light and a mask member arranged between the lamp unit and the treatment target, having a scattering area for controlling the intensity distribution of light with which the treatment target is irradiated on a surface opposite to the treatment target or in the vicinity of the treatment target and composed of a transparent material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an activation heat treatment apparatus and a heat treatment method used in a heat treatment step in a manufacturing process or the like of a display device such as a liquid crystal display device.

  As a display device such as a liquid crystal display device, an active matrix type in which each pixel is provided with a thin film transistor (TFT) which is a thin film semiconductor device in order to drive a large number of pixels arranged in a matrix on a glass substrate. The display device is known. In the manufacturing process of TFT used for such applications, heat treatment such as activation of impurity ions in the semiconductor layer is required.

  In TFTs of liquid crystal display devices, 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, since the resistivity differs particularly in the source and drain regions depending on the activation state, an efficient activation process is required.

  Such a heat treatment step for the activation treatment has been conventionally performed by so-called furnace annealing, in which a target object into which impurities for forming source and drain regions are ion-implanted is placed in a heat treatment furnace and heated. .

  However, in this furnace annealing, since the strain point of the glass substrate is about 670 ° C., the heating temperature has to be lower than this temperature, which causes a problem that the resistivity of the source and drain regions is not sufficiently lowered. Yes.

  Therefore, in order to improve the efficiency of the heat treatment, lamp annealing is performed by using a flash lamp as a light source, irradiating light to the irradiated object instantaneously, and locally raising the semiconductor layer that absorbs light to a high temperature of 1000 ° C. or higher. The law is used.

  The object to be processed is formed by crystallizing an amorphous semiconductor film through a base insulating film on a glass substrate, and then cutting into a predetermined pattern to form a plurality of island-shaped semiconductor films on the glass substrate. Then, a transistor is formed in alignment with the island-shaped semiconductor film.

However, when the activation process is performed by the lamp annealing method in this transistor formation process, when the size of the island-shaped semiconductor film of the object to be processed has a large pattern exceeding 100 μm and a small pattern of several tens of μm, There was such a problem. That is, when the irradiation intensity of light is controlled so that the large-pattern island-shaped semiconductor film is heated to a predetermined temperature, the small-pattern island-shaped semiconductor film is not heated to the predetermined temperature, and the small-pattern island-shaped semiconductor film is heated. If the irradiation intensity of light is controlled so that the film is heated to a predetermined temperature, there arises a problem that the temperature of the large pattern rises too much and the material is dissolved.
In order to solve such a problem, a method has been proposed in which light is irradiated to the object to be processed through a light shielding mask, and a part of the object to be processed is selectively shielded and heated (for example, Patent Documents). 1).
JP 2000-77349 A

  However, the heat treatment method proposed in Patent Document 1 uses, as a light shielding mask, a metal plate such as tungsten provided with an opening, or a transparent substrate such as quartz glass covered with a light shielding film. Yes. When light is irradiated with a lamp having a high energy density such as a flash lamp through such a light shielding mask, the metal plate or the light shielding film constituting the light shielding mask absorbs a part of the light and generates heat, and the deformation or pattern of the light shielding mask. There is a problem of causing distortion.

  Further, in the lamp annealing, it was found that each island-like semiconductor film on the glass substrate irradiated with light has a lower temperature rise at the peripheral portion than a temperature rise at the central portion. It has been found that a transistor manufactured by aligning the source / drain region in the region having the temperature difference causes a difference in activation treatment in each source / drain region and deteriorates the transistor characteristics. This difference in activation treatment appears as a difference in contact resistance value.

  The present invention has been made under the circumstances as described above, and an object thereof is to provide an activation heat treatment apparatus and an activation heat treatment method in which uniform activation of each island-like semiconductor film is realized.

  In order to solve the above-described problem, a first aspect of the present invention includes a holding table that holds a target object, a lamp unit that heats the target object by irradiating the target object with light, and It is arranged between the lamp unit and the object to be processed, and has a plurality of discrete scattering regions for controlling the intensity distribution of the light irradiated to the object to be processed on or near the surface facing the object to be processed. Provided is an activation heat treatment apparatus comprising a mask member made of a transparent material.

  A second aspect of the present invention is a method for heat-treating the object to be processed by irradiating the object to be processed with light from a lamp unit, wherein the irradiation with the light is at or near the surface facing the object to be processed. In addition, a mask member made of a transparent material having a plurality of discrete scattering regions for controlling the intensity distribution of light applied to the object to be processed is interposed between the lamp unit and the object to be processed. A heat treatment method is provided.

  In such an activation heat treatment apparatus and heat treatment method, a flash lamp can be used as the lamp unit. In addition, quartz can be used as the transparent material.

  A large number of fine grooves can be used as the scattering region of the mask member. These many fine grooves can be formed by etching.

  An uneven surface can be used as the scattering region of the mask member. This uneven surface can be formed by sandblasting.

  Furthermore, microcracks formed in the vicinity of the surface facing the object to be processed can be used as the scattering region of the mask member. This micro crack can be formed by laser light irradiation.

  Furthermore, the distance between the mask member and the surface of the object to be processed can be set to 10 to 100 μm.

  According to the present invention, each island-like semiconductor film has a uniform temperature rise in both the peripheral part and the central part, and has an effect of being uniformly activated and heat-treated.

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

  FIG. 1 is a diagram illustrating the configuration of an activation heat treatment apparatus according to an embodiment of the present invention. In FIG. 1, a holding table 2 for holding an object to be processed is disposed inside an apparatus main body 1 composed of a processing container, for example, an airtight container, and the object to be processed 3 is aligned on the holding table 2. Is automatically loaded and placed. On the processing surface of the object 3 to be processed, the mask member 4 is arranged with a minute interval, for example, 10 to 100 μm. Above the mask member 4 and outside the apparatus main body 1, a lamp unit 5 is disposed that emits instantaneous light and emits energy light necessary for activating the workpiece 3.

  The lamp unit 5 includes, for example, a plurality of flash lamps 6 and a reflector 7, and the flash lamp 6 emits light by discharging an inert gas such as xenon. The reflector 7 is provided to uniformly reflect the light emitted upward from the flash lamp 6 toward the object 3 to be processed.

  As the flash lamp 6, for example, a xenon flash lamp having a length in the vicinity of the length of one side of the rod-shaped object 3 can be used. The xenon flash lamp 6 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. A high voltage is applied to the electrode, ionizing part of the xenon gas in the glass tube and breaking the insulation between the anode and cathode, 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 glass tube.

 Flash lamp light has a wavelength sensitivity characteristic that shows a maximum in the visible region from ultraviolet light, and it is efficient in a short time by irradiating a semiconductor layer with xenon flash lamp light having a pulse width of 0.1 ms to 100 ms. By performing the annealing treatment, the activation treatment of impurity ions contained in the semiconductor layer can be performed. The island-like semiconductor film irradiated by the xenon flash lamp light is irradiated instantaneously for 0.1 ms to 100 ms (milliseconds), and is instantaneously heated to about 1400 ° C. Since the glass substrate is instantaneous irradiation between 0.1 ms and 100 ms (milliseconds), changes such as melting and deformation do not occur. As the xenon flash lamp, a lamp having a light intensity in the ultraviolet to visible light region is suitable.

  For example, when an activation process of a thin film semiconductor device provided on a glass substrate is performed as the object to be processed 3, a semiconductor layer pattern such as an island-shaped semiconductor region (silicon) is usually provided on the surface. It has been found that the state of heat generation upon irradiation is not uniform within the surface of the workpiece 3.

  2A and 2B are views for explaining the configuration of the object 3 to be activated, in which FIG. 2A is a partially cutaway sectional view, and FIG. 2B is a plan view of an island-like silicon layer. The object to be processed 3 has a configuration in which a base insulating film 22 such as a silicon oxide film is provided on a substrate such as a glass substrate 21, and an island-like silicon layer 23 is provided on the base insulating film 22.

  Thus, when the to-be-processed object 3 which formed the island-like silicon film on the board | substrate 21 was heat-processed with the activation processing apparatus shown in FIG. 1, it turned out that it has the heat processing characteristic as shown in FIG.

  In particular, the heat outflow from the peripheral part of the island-like silicon layer 23 is surprisingly large, and the heating temperature in the region less than 25 μm from the peripheral edge 24 tends to be lower than that in the pattern central part as shown in FIG. The heat treatment state of the semiconductor layer near 24 is deteriorated. In FIG. 3, the horizontal axis indicates the distance from the peripheral edge 24 of the island-like silicon layer 23, and the vertical axis indicates the Raman spectral peak height corresponding to the abundance of crystalline silicon (the degree of activation treatment, in particular, recrystallization). Is equivalent to the degree). The higher the peak height, the greater the amount of crystalline silicon present, that is, it was heated at a higher temperature. From FIG. 3, it can be seen that the peak height of Raman spectroscopy tends to decrease in the region 25 less than 25 μm from the peripheral edge 24, and the heating temperature near the pattern edge is lower than the other portions. Here, if light irradiation is performed so that the region of the peripheral edge 24 is sufficiently heated, the central portion of the island-like silicon layer 23 is excessively heated to cause melting and aggregation of silicon, and the uniformity of the heat treatment state is improved. The problem of being damaged arises. Therefore, in order to improve the uniformity in each pattern surface and further improve the uniformity of the heat treatment state in the surface of the object 3, the light irradiation intensity distribution in the surface of the object 3 is changed. Need to control. The mask member 4 bears the control function.

  The mask member 4 used in the activation heat treatment apparatus according to an embodiment of the present invention is provided with discretely arranged scattering regions on the surface facing the object 3 or in the vicinity thereof. The light scattering region corresponds to a region 26 excluding the region 25 less than 25 μm from the peripheral edge 24 of each island-like silicon layer 23 discretely arranged on the substrate of the object 3 to be processed. That is, it corresponds to a region excluding the region 25 where the temperature decrease near the peripheral edge 24 occurs. Since the light from the lamp unit 5 is scattered by the light scattering region and the intensity of the light applied to the region of the object 3 corresponding to the light scattering region is reduced, the region of the peripheral edge 24 can be sufficiently set. Even if light irradiation is performed so as to heat, the region 26 in the center of the pattern is not excessively heated. The arrangement of the light scattering region of the mask member 4 is designed according to the pattern arrangement of the island-like silicon layer 23 of the object 3 to be processed. When the length of at least one side of the pattern of the object 3 is less than 25 μm In some cases, a light scattering region corresponding to the pattern may not be provided.

  As shown in FIG. 4, the light scattering region formed in the mask 3 can be configured by forming fine grooves 8 on the lower surface facing the surface of the object 3 to be processed. The light from the lamp unit 5 is scattered by being reflected by the inner surface of the groove 8, and a part of the light is scattered on the lamp unit 5 side, and the object to be processed 4 facing the light scattering region where the groove 8 is formed. The intensity of light that irradiates the surface area of is reduced.

  Such a groove 8 can be formed in the quartz glass substrate by etching, particularly dry etching. Alternatively, a fine uneven surface may be used instead of the groove 8. Such a fine uneven surface can be formed by, for example, sandblasting.

  Another example of the light scattering region is a microcrack 9 formed in the vicinity of the surface of the workpiece 3 as shown in FIG. Even with such a microcrack 9, the light is scattered and returned to the lamp unit 5, and the intensity of the light applied to the surface region of the object 3 facing the light scattering region where the microcrack 9 is formed is reduced. Decrease.

  Such a microcrack 9 can be generated by thermal stress by irradiating a high-intensity laser beam to a position where the microcrack 9 near the surface of the mask member 4 is to be provided. The method of forming the microcracks 9 by irradiating such laser light is similar to a technique called laser marking, which is conventionally known as a method of applying a pattern to a glass product.

  A desirable material for the mask member 4 is quartz. The reason for this is that quartz has a low light absorptivity from the near infrared to a part of the ultraviolet region and a high transmittance, so that the heat generation at the mask member 4 due to the incidence of flash lamp light is small, and the thermal expansion coefficient. Therefore, the deformation of the mask member 4 due to heat generation hardly occurs.

  Since the mask member 4 is entirely made of the same material, unlike the conventional mask member 4 including a light-shielding film made of a different material, the mask member is not distorted due to a difference in heat generation. .

  As described above, the mask member 4 is disposed on the incident surface of the object 3 to be processed with a small interval, for example, 10 to 100 μm. If this interval is large, the flash lamp light is directly incident on the incident surface of the workpiece 3 from the lateral direction, and the light intensity reduction effect is impaired. On the other hand, if the interval is too narrow, the mask member 4 may come into contact with the object 3 to be processed, and the surface of the object 3 may be contaminated.

  For example, when the object 3 having a large pattern and a small pattern is heat-treated using the activation heat treatment apparatus described above, the mask member 4 is interposed between the object 3 and the lamp unit 5 and the temperature is increased. When the pattern to be processed is irradiated with light from the lamp unit 5 so as to cover a pattern having a large size that is likely to rise with the scattering region of the mask member 4, the object to be processed 3 is made uniform, for example, a polycrystalline silicon layer of about 1400. It can be heated to 0C. As a result, the heat treatment of the object to be processed, for example, activation of impurities contained in the polycrystalline silicon layer can be effectively performed in a short time.

  As described above, according to an embodiment of the present invention, an accurate irradiation intensity distribution can be realized on the irradiated surface of the object to be processed 3, and partial irradiation of the irradiated surface or improvement in heating uniformity can be achieved. Therefore, it is possible to accurately control the light heating, such as adjusting the irradiation intensity distribution.

  Next, an embodiment applied to a manufacturing process of a thin film transistor circuit will be described with reference to FIG. The same parts as those in FIGS. 1 to 5 are denoted by the same reference numerals, and detailed description thereof will be omitted because it is duplicated.

  As shown in FIG. 6A, a base insulating film 22 is formed on the glass substrate 21, and an amorphous semiconductor layer 27 is formed on the base insulating film 22. The amorphous semiconductor layer 27 is irradiated with laser light to be crystallized. Next, as shown in FIG. 6B, the amorphous semiconductor layer 27 is selectively etched using a photolithography technique to form a plurality of island-like silicon layers 23.

Next, as shown in FIG. 6C, a gate oxide film 28, for example, a SiO ₂ film having a thickness of about 20 nm to 100 nm is formed on the island-like silicon layer 23. A gate electrode 29 is formed on each island-like silicon layer 23 on the gate oxide film 28 as shown in FIG. These gate electrodes 29 are formed by patterning a metal film such as MoW.

Next, as shown in FIG. 6E, impurities for forming the source region 30 and the drain region 31 are ion-implanted using the gate electrode 29 as a mask. The impurity ions are N-type impurities such as phosphorus if N-channel thin film transistors are formed, and P-type impurities such as boron if P-channel thin film transistors are formed. As a result, a channel region 32 is formed in each island-like silicon layer 23 under the gate electrode 29.

  Next, when carrying out the activation processing step, the object 3 shown in FIG. 6 (e) is carried into the activation processing apparatus shown in FIG. 1 and the activation processing is carried out. In this activation processing step, the activation light incident on the central part from the peripheral edge 24 to 25 μm is attenuated through the scattering surface for each island-like silicon layer 23 having a side of 50 μm or more from FIG. Process.

Next, an interlayer insulating film made of, for example, SiO ₂ is formed on the gate insulating film 28 including the gate electrode 29. A part of the interlayer insulating film and the gate insulating film 28 is removed by selective etching to form a contact hole. Through this contact hole, the source region 30, the drain region 31, and the gate electrode and the wiring layer are electrically connected to complete the thin film semiconductor device.

  In the above example, the case where the activation light incident on the central portion of the island-like silicon layer 23 is attenuated through the scattering surface and activated is shown. However, as shown in FIG. An object to be processed in which the element 30 and the semiconductor element 33 having a small gate width are mixed can be carried into the activation processing apparatus shown in FIG. In this way, light irradiation is performed on a region where the semiconductor element 30 having a large gate width and the semiconductor element 33 having a small gate width are mixed, and the impurity ions in the silicon patterns 31a and 31b in which the gates 32a and 32b are formed are activated. In some cases, the central portion of the semiconductor element 30 having a large gate width tends to be heated more strongly than the semiconductor element 33 having a small gate width, and light irradiation is performed with an intensity suitable for heating the semiconductor element 33 having a small gate width. In some cases, the central portion of the semiconductor element 30 having a large gate width is excessively heated, and the film quality of the silicon pattern 31a is deteriorated. In order to prevent such a problem, a light scattering region 34 that scatters incident light incident on the central portion of the semiconductor element 30 having a large gate width is provided in the mask so that the intensity of the incident light is attenuated. Good.

  In the above embodiment, the activation process of the thin film transistor formed on the island-like silicon layer 23 has been described. However, the thin film transistor may be applied to a heat treatment process of another electronic component formed on the glass substrate. In the above embodiment, the flash lamp is used as the light source of the lamp unit 6, but CW-YAG laser light may be irradiated, for example, scanned instead of the light irradiation by the flash lamp.

Sectional drawing which shows the activation heat processing apparatus which concerns on one Embodiment of this invention. The figure for demonstrating the structure of the to-be-processed object of FIG. The characteristic view for demonstrating the characteristic which a temperature difference produces in a center part and a peripheral part, when the area of an island-like silicon layer becomes large when the to-be-processed object of FIG. 2 is heat-processed. The figure which expands and shows the structure of the mask of FIG. The figure for demonstrating other embodiment of the mask of FIG. Sectional drawing for demonstrating embodiment applied to the manufacturing process of the thin-film transistor as a to-be-processed object of FIG. 2 in order of a process. The top view of the to-be-processed object for demonstrating other embodiment.

Explanation of symbols

 DESCRIPTION OF SYMBOLS 1 ... Apparatus main body, 2 ... Holding stand, 3 ... To-be-processed object, 4 ... Mask member, 5 ... Lamp unit, 6 ... Flash lamp, 7 ... Reflector, 8 ... Fine groove, 9 ... Micro crack, 10 ... Gate width Large semiconductor elements, 11a, 11b ... silicon patterns, 12a, 12b ... gate electrodes, 13 ... semiconductor elements with small gate width, 14 ... light scattering regions.

Claims (11)

  A holding table for holding the object to be processed, a lamp unit provided opposite to the holding table for irradiating the object to be processed to activate the object to be processed, the lamp unit and the holding A mask made of a transparent material, which is arranged between a table and has a plurality of discrete scattering regions for controlling the intensity distribution of light irradiated to the object to be processed on or near the surface facing the object to be processed An activation heat treatment apparatus comprising: a member.   The heat treatment apparatus for activation according to claim 1, wherein the lamp unit is a flash lamp.   The heat treatment apparatus for activation according to claim 1, wherein the transparent material is quartz.   The heat treatment apparatus for activation according to claim 1, wherein the scattering region of the mask member is a region in which a large number of fine grooves are formed.   5. The activation heat treatment apparatus according to claim 4, wherein the plurality of fine grooves are formed by etching.   The heat treatment apparatus for activation according to claim 1, wherein the scattering region of the mask member is an uneven surface region.   The heat treatment apparatus for activation according to claim 6, wherein the uneven surface is formed by sandblasting.   The heat treatment apparatus for activation according to claim 1, wherein the scattering region of the mask member is a microcrack formed in the vicinity of a surface facing the object to be processed.   The activation heat treatment apparatus according to claim 8, wherein the microcracks are formed by irradiation.   An activation heat treatment apparatus, wherein a distance between the mask member and the surface of the object to be processed is 10 to 100 μm.   A method of irradiating the object to be processed by irradiating the object to be processed with light from a lamp unit, wherein the object is irradiated on the surface facing the object to be processed or in the vicinity thereof. A heat treatment method comprising: performing a mask member made of a transparent material having a plurality of discrete scattering regions for controlling the intensity distribution of light to be interposed between the lamp unit and the object to be processed.

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