JP2012004250A - Device and method for forming low-temperature polysilicon film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-temperature polysilicon film in which the growth direction of crystal grains can be randomly adjusted according to the position to be polycrystallized and at the position, the growth direction of the crystal grains is uniform in a certain direction.SOLUTION: A mask 3 is provided with a shield region 31 and a transparent region 32 against laser light extended to one direction which are adapted to be adjacent in the vertical direction relative to the one direction. Laser light is irradiated on an expected region 7 in which a channel region is formed, with a microlense 5 via the mask 3. The laser light transmitted through the transparent region 32 is irradiated on an a-Si:H film to anneal and polycrystallize the a-Si:H film. After that, removal of the mask 3 and irradiation of laser light across the expected region 7 cause no fusion of the already polycrystallized region due to the increased fusion point, thereby dissolving and solidifying the region that remains amorphous to be polycrystallized.

Description

  The present invention relates to a low-temperature polysilicon film that crystallizes a-Si into polycrystalline silicon (hereinafter referred to as polysilicon) by irradiating an amorphous silicon film (hereinafter referred to as a-Si film) with laser light and annealing. The present invention relates to a forming apparatus and method.

  As a thin film transistor having an inverted stagger structure, a gate electrode is formed of a metal layer such as Cr or Al on an insulating substrate, and then, for example, a SiN film is formed as a gate insulating film on the substrate including the gate electrode. A hydrogenated amorphous silicon (hereinafter referred to as a-Si: H) film is formed on the entire surface, and the a-Si: H film is patterned in an island shape in a predetermined region on the gate electrode. There is an amorphous silicon transistor in which a drain electrode is formed.

  However, since this amorphous silicon transistor uses an a-Si: H film for the channel region, there is a drawback that the mobility of charges in the channel region is small. Therefore, an amorphous silicon transistor can be used as a pixel transistor in a pixel portion of a liquid crystal display device, for example. However, as a drive transistor in a peripheral drive circuit that requires high-speed rewriting, the charge mobility in the channel region is high. It is too small and difficult to use.

  On the other hand, when a polycrystalline silicon film is formed directly on a substrate, it is formed by LPCVD (Low Pressure Chemical Vapor Deposition), which is a high temperature process of about 1500 ° C. A polycrystalline silicon film cannot be directly formed on a transparent glass substrate (softening point is 400 to 500 ° C.).

  Therefore, once an a-Si: H film is formed in the channel region, and then this a-Si: H film is irradiated with a laser beam such as a YAG excimer laser to perform laser annealing, thereby melting in an extremely short time. Due to the solidification phase transition, a low-temperature polysilicon process for crystallizing an a-Si: H film into a polysilicon film has been adopted. As a result, the channel region on the glass substrate can be formed of a polysilicon film that has high charge mobility and can speed up the transistor operation (Patent Document 1).

JP-A-5-63196

  However, the conventional low-temperature polysilicon film forming method described above is based on melting and solidification of the amorphous silicon film by laser annealing while scanning the entire amorphous silicon film formed on the glass substrate of the liquid crystal display device. Since the transistor is polycrystallized, a region for forming a transistor that does not require high speed, such as a pixel transistor in a display portion, is also polycrystallized, and thus processing is wasted.

  Moreover, there is a problem that the characteristics of the polysilicon film formed by laser annealing fluctuate locally, which is an obstacle to practical use. Such local fluctuations in the characteristics of the low-temperature polysilicon film cause uneven display on the screen of the liquid crystal display device.

  As a factor that the characteristics of the a-Si film locally fluctuate, the crystal grain size of the crystallized Si fluctuates locally, and the electric conductivity in the polysilicon film depends on the density or state of the crystal grain boundary. The electrical conductivity of the entire polysilicon film changes. Even if only the peripheral circuit portion of the liquid crystal display device is polycrystallized, the rate at which crystal grain boundaries appear locally differs in the direction in which the drive current of the peripheral circuit flows in relation to the crystal grain growth direction. . For this reason, the easy conductivity of the current varies depending on the location where the transistor is formed, the speed of the transistor varies, and the design of the transistor in the peripheral circuit becomes difficult.

  The present invention has been made in view of such problems, and the growth direction of crystal grains can be arbitrarily adjusted according to the position to be polycrystallized. An object of the present invention is to provide an apparatus and a method for forming a low-temperature polysilicon film that can obtain a low-temperature polysilicon film aligned in a certain direction.

  An apparatus for forming a low-temperature polysilicon film according to the present invention includes a plurality of microlenses arranged one-dimensionally or two-dimensionally, a generation source of laser light, and a laser beam from the generation source to the microlens. A light guide portion for condensing the laser light on the amorphous silicon film by the microlens; and a plurality of masks arranged for each microlens, wherein each of the masks shields the laser light. The light-shielding region and the transmission region that transmits the laser light are provided so as to extend in one direction and to be adjacent to each other in a direction perpendicular to the one direction.

In this low temperature polysilicon film forming apparatus, for example, a plurality of the light shielding regions and the transmission regions are provided for each mask, and the light shielding regions and the transmission regions are alternately arranged. In addition, for example, one or a plurality of transistors are formed in each polysilicon film formed by annealing an amorphous silicon film with laser light that has passed through each microlens.

  A first low-temperature polysilicon film forming method according to the present invention uses any one of the above-described low-temperature polysilicon film forming apparatuses, and first, laser light is converted into an amorphous silicon film by the microlens through the mask. A first step of irradiating the amorphous silicon film with a laser beam transmitted through the transmission region by irradiation to form a polysilicon region; and then, using the microlens without using the mask, the laser beam is emitted from the amorphous silicon film. And a second step of polycrystallizing the remaining amorphous silicon film using the polysilicon film as a crystal nucleus by irradiating the film.

  In the first low-temperature polysilicon film forming method, for example, the first step and the second step can be configured such that the laser light emission conditions by the laser light source are the same.

  A second low-temperature polysilicon film forming method according to the present invention uses any one of the above-described low-temperature polysilicon film forming apparatuses, and irradiates the amorphous silicon film with laser light through the mask through the microlens. The irradiation condition of the laser beam is sufficient to melt and polycrystallize the portion of the amorphous silicon film corresponding to the light-shielding region. A temperature difference exists between a portion corresponding to the light shielding region and a portion corresponding to the transmission region.

  These low-temperature polysilicon film formation methods can be applied to a low-temperature polysilicon film formation method in a peripheral circuit of a liquid crystal display device. In this case, the method of the present invention uses any one of the above-described low-temperature polysilicon film forming apparatuses. For example, each transistor group including one or a plurality of transistors in the peripheral circuit is associated with a microlens, By determining the one direction of the mask in accordance with the transistor group, the crystallization direction (main growth direction of crystal grains) of the amorphous silicon film of the transistor group is adjusted.

  According to the present invention, each microlens is provided with a mask, and each of the masks has a light shielding region and a transmission region extending in one direction and adjacent to each other in a direction perpendicular to the one direction. It is provided as follows. For this reason, when laser light is irradiated to the amorphous silicon film by the microlens using this mask, the portion of the amorphous silicon film corresponding to the light shielding region (hereinafter referred to as the first portion) is not irradiated with laser light. Alternatively, the amount of irradiation is small and the applied energy is small, and the portion of the amorphous silicon film corresponding to the transmission region (hereinafter referred to as the second portion) is irradiated with laser light and the applied energy is large.

  In the first method of forming a low-temperature polysilicon film of the present invention, in the first step, the mask is used to irradiate the laser beam, and the second part of the amorphous silicon film is heated and melted. Thereafter, it is crystallized by solidification, and the second portion of the amorphous silicon film is turned into polysilicon. Next, in the second step, the entire amorphous silicon film is heated by irradiation with laser light without using the mask. However, since the polysilicon portion (second portion) formed in the first step has a high melting point, it does not melt in the second step and remains in the amorphous state in the first step (first portion). ) Melts and solidifies and crystallizes. When this first portion is crystallized, solidification proceeds with the already crystallized second portion as a nucleus, so that the crystal grains are perpendicular to the direction in which the second portion extends (the direction in which the transmission region of the mask extends). That is, the second portion grows from the second portion toward the other second portion facing the first portion. Therefore, crystal grains grow from the two opposing second parts, and the first part solidifies and crystallizes. As a result, a low-temperature polysilicon film in which the main growth direction of crystal grains is aligned in a direction perpendicular to one direction is obtained.

  In the second method for forming a low-temperature polysilicon film of the present invention, the condition of laser beam irradiation is sufficient for the amorphous silicon film portion (first portion) corresponding to the light shielding region to be melted and polycrystallized. It is a thing. At this time, the portion (second portion) of the amorphous silicon film corresponding to the transmission region is irradiated with laser light that has passed through the transmission region, so that the first portion is heated with energy larger than that of the first portion. Higher than the temperature. Thereby, when the amorphous silicon film is polycrystallized, there is a temperature difference between the first portion corresponding to the light shielding region and the second portion corresponding to the transmission region in the amorphous silicon film. Therefore, solidification is started from the first portion, and solidification proceeds from the first portion toward another first portion facing the second portion. Accordingly, a low-temperature polysilicon film in which crystal grains extend in a direction perpendicular to the one direction in which the first portion extends and the crystal grains are aligned in a direction perpendicular to the one direction is obtained.

  The above-described method of the present invention can be used for forming a channel region of a transistor in a peripheral circuit of a liquid crystal display device. In this case, by determining the one direction as an appropriate direction for each transistor group, the direction in which the driving current determined by the structure of the transistor flows can be matched with the main growth direction of the crystal grains. Since the growth direction of the crystal grains is aligned with the direction in which the current flows, the number of crystal grain boundaries where the drive current intersects is small. Thereby, the resistance in the direction in which the drive current flows can be reduced, and the current consumption can be reduced and the speed can be increased. In addition, by setting one direction in which the light shielding region and the transmission region of the mask corresponding to each microlens extend according to the position irradiated by each microlens, for each irradiation region of the laser light corresponding to each microlens, An appropriate crystal grain growth direction can be set.

  A third method for forming a low-temperature polysilicon film according to the present invention includes a plurality of one-dimensionally or two-dimensionally arranged microlenses, a laser light source, and a laser beam from the source. A light guide unit that guides the laser light to the amorphous silicon film by the microlens and a plurality of masks arranged for each microlens, and each mask transmits the laser light A low-temperature polysilicon film forming apparatus is used in which a linear transmission region extending in one direction that transmits the laser light is provided in a light-shielding region that shields light, and the mask is the micro In the projection area on the amorphous silicon film projected by the lens, the linear laser beam transmitted through the transmission area scans the projection area in a direction perpendicular to the one direction. And features.

  Thus, by scanning the linear irradiation area on the amorphous silicon film of the laser light that has passed through the mask within the projection area on the amorphous silicon film on which the mask is projected, the laser light is irradiated. The melting linear region moves in a direction perpendicular to this line. Then, the melted region by laser light irradiation is cooled and solidified by the separation of the laser light, and becomes polycrystallized, and the heat flow of heat and cooling of the crystal grains is in a direction perpendicular to the one direction. Since it is originally formed, the growth direction of crystal grains is the direction perpendicular to the one direction, that is, the scanning direction of the laser beam. Thereby, also in the present invention, the crystal growth direction of the polysilicon film becomes a constant and uniform direction in a minute region corresponding to each microlens.

  In this low temperature polysilicon film forming method, for example, the laser light irradiation system including the microlens and the mask of the low temperature polysilicon forming apparatus and the substrate on which the amorphous silicon film is formed are relatively moved. Thus, the laser beam can be scanned in the projection area.

  According to the present invention, when microareas are crystallized using a microlens, for each microlens, a transmission area extending in one direction and a light shielding area are provided adjacent to each other in a direction perpendicular to the one direction. Since the prepared mask is used, when the crystal grains are grown by melting and solidification by irradiating the amorphous silicon with the laser beam, a polysilicon film in which the growth directions of the crystal grains are aligned is obtained. The crystal grain growth direction can be arbitrarily adjusted by simply setting the mask arrangement position so that the one direction faces a predetermined direction. Therefore, according to the present invention, the growth direction of crystal grains can be easily adjusted to the direction of current at the position, the design of the transistor becomes easy, and the power consumption of the transistor and the driving speed can be increased. Become.

1 is a schematic perspective view showing a low-temperature polysilicon film forming apparatus according to a first embodiment of the present invention. In this embodiment, it is a typical expansion perspective view which shows the one micro lens and a corresponding mask. It is a figure which shows the laser irradiation apparatus which uses a micro lens. It is a schematic diagram which shows operation | movement of this embodiment. It is a figure which shows the modification of a laser irradiation apparatus. It is a schematic plan view which shows the display part and peripheral circuit part of a liquid crystal display device. (A), (b) is a schematic diagram which shows the relationship between a crystal grain growth direction and the direction through which an electric current flows. It is a typical expansion perspective view which shows the mask used in the formation apparatus of the low temperature polysilicon film which concerns on 2nd Embodiment of this invention. It is a schematic diagram which shows operation | movement of this embodiment. It is a figure which shows the laser irradiation apparatus by the micro lens used for the formation method of the low-temperature polysilicon film which concerns on 3rd Embodiment of this invention. In this embodiment, it is a typical expansion perspective view which shows the one micro lens and a corresponding mask. It is a schematic diagram which shows operation | movement of this embodiment.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a schematic perspective view showing an apparatus for forming a low-temperature polysilicon film according to an embodiment of the present invention, FIG. 2 is a schematic enlarged perspective view showing one microlens and a corresponding mask, and FIG. It is a figure which shows the laser irradiation apparatus using a micro lens. In the manufacturing process of a semiconductor device such as an inverted staggered thin film transistor, the laser irradiation apparatus shown in FIG. 3 is annealed by irradiating only the channel region formation scheduled region with laser light, for example. This is an apparatus for polycrystallizing and forming a polysilicon film. In the laser annealing apparatus using this microlens, the laser light emitted from the light source 1 is shaped into a parallel beam by the lens group 2 and irradiated to the irradiated object 6 through the microlens array including a large number of microlenses 5. To do. The laser light source 1 is, for example, an excimer laser that emits laser light having a wavelength of 308 nm or 353 nm at a repetition period of, for example, 50 Hz. In the microlens array, a large number of microlenses 5 are arranged on the lower surface of the transparent substrate 4a, and the laser light is condensed on a thin film transistor formation scheduled area set on a thin film transistor substrate as an irradiated body 6. . The transparent substrate 4a is arranged in parallel to the irradiated body 6, and the microlenses 5 are arranged at a predetermined pitch corresponding to the transistor formation scheduled area. The irradiated body 6 of the present embodiment is, for example, an a-Si film formed uniformly on a glass substrate of a liquid crystal display device. The low-temperature polysilicon film forming apparatus of the present embodiment is an a-Si film. A polysilicon channel region is formed by irradiating a region where a transistor channel region is to be formed in the peripheral circuit of the film with laser light.

  The microlens 5 is provided on the lower surface of the transparent substrate 4 a with the focal position downward, and the light shielding member 8 is provided on the upper surface of the transparent substrate 4 a corresponding to each microlens 5. The light shielding member 8 has an opening for irradiating the laser beam only to the channel formation scheduled region. The opening of the light shielding member 8 is disposed above each microlens 5. A channel region of silicon is defined. A transparent substrate 4c is arranged above the transparent substrate 4a in parallel with the transparent substrate 4a, and a mask 3 to be described later is formed at a position corresponding to each microlens 5 on the lower surface of the transparent substrate 4c. Has been.

For example, when a pixel driving transistor is formed as a peripheral circuit of a liquid crystal display device, a gate electrode made of a metal film such as Al is formed on a glass substrate by sputtering. Then, a gate insulating film made of a SiN film is formed on the entire surface by low-temperature plasma CVD at 250 to 300 ° C. using silane, NH ₃ and H ₂ gases as source gases. Thereafter, an a-Si: H film is formed on the gate insulating film by, for example, a plasma CVD method. This a-Si: H film is formed using a gas obtained by mixing silane and H ₂ gas as a source gas. The region on the gate electrode of the a-Si: H film is set as a channel formation planned region, and one microlens 5 is arranged in each channel region, and only the channel formation planned region is irradiated with laser light and annealed. Then, this channel formation scheduled region is polycrystallized to form a polysilicon channel region. 3A and 1 only show a state in which the microlenses 5 are arranged one-dimensionally, this is for simplification of illustration, and in fact, FIG. ), The microlenses 5 are two-dimensionally arranged. However, the microlenses 5 may be arranged one-dimensionally in accordance with the arrangement of regions to be polycrystallized.

  Thus, in the present embodiment, as shown in FIGS. 1, 2, and 3 (a), one mask 3 is provided above each microlens 5 for each microlens 5. . The mask 3 is provided so that, for example, a plurality of laser light shielding regions 31 having a rectangular shape as a whole and forming a linear shape extend in one direction. The linear light shielding regions 31 are arranged at an appropriate length interval, and a laser light transmission region 32 is formed between the light shielding regions 31. Accordingly, the light shielding region 31 and the transmission region 32 both extend in one direction, and the light shielding region 31 and the transmission region 32 are adjacent to each other in a direction perpendicular to the one direction. At least one light shielding region 31 is provided for each mask 3. The width of the light shielding region 31 and the width of the transmission region 32 can be arbitrarily determined in order to control the crystal growth direction described later. By irradiating the irradiated object 6 with the laser light through the mask 3 through the microlens 5, an irradiation region of the laser light is formed in the a-Si: H film corresponding to the channel region formation scheduled region 7. Is done. The irradiation pattern of the laser light in the planned area 7 corresponds to the pattern of the transmission area 32 of the mask 3.

  Note that the transparent substrate 4a on which the microlens 5 and the light shielding member 8 are formed and the transparent substrate 4c on which the mask 3 is formed have a transparent substrate 4b disposed between them as shown in FIG. The substrates 4a, 4b, and 4c may be integrated by bonding to each other.

  Next, a method for forming a low-temperature polysilicon film using the forming apparatus configured as described above will be described. As shown in FIG. 6, the liquid crystal display device 10 forms pixel transistors in a matrix in the display unit 11, outputs a signal to the gate of each pixel transistor, and outputs a drain signal to each pixel transistor. The drive unit 13 is provided in the peripheral part of the display unit 11 and forms a peripheral circuit. By scanning the drain signal and the gate signal, each pixel transistor operates to control light transmission and light shielding from the backlight.

Conventionally, an amorphous silicon film formed on a glass substrate of a liquid crystal display device is scanned with a linear light source of laser light in one direction to melt and solidify the amorphous silicon film to be polycrystallized. For this reason, as shown in FIGS. 7A and 7B, the crystal grain growth direction is the same in any position on the glass substrate, and the crystal grains are in this crystal growth direction. It has a flat shape. Accordingly, in a region where the drive unit 13 is formed of, for example, the drain signal of the peripheral circuit, the signal current i ₁ is, as shown in FIG. 7 (a), results Tsuryu the crystal growth direction, the current i ₁ passes through the crystal The number of grain boundaries is small, current conductivity is high, and resistance is low. However, in the region where the transistor is formed, for example, in the region where the gate signal driver 12 is formed, the signal current i2 flows in a direction perpendicular to the crystal growth direction as shown in FIG. Has a large number of crystal grain boundaries, low electrical conductivity, and high resistance.

  In contrast, in this embodiment, the growth direction of crystal grains can be locally controlled, and the growth direction of crystal grains can be adjusted to the direction in which current flows at any position on the glass substrate. it can. First, an operation for controlling the growth direction of crystal grains according to the present embodiment will be described. In the first step, the object 6 is irradiated with laser light using the mask 3. The parallel beam of the laser light passes through the mask 3, is collected by each microlens 5, and is irradiated to the channel formation scheduled region 7 in the a-Si: H film of the irradiated body 6. At this time, the laser light is shielded in the light shielding region 31 of the mask 3, and only the portion that has passed through the transmission region 32 is irradiated to the planned region 7, and the laser light irradiation region has a lattice pattern similar to the mask 3. It is formed. In this planned region 7, only the portion irradiated with the laser light is melted and solidified to be crystallized, and this portion is transformed into polysilicon. This polysilicon portion is a portion where the transmission region 32 of the mask 3 is reduced and projected by the microlens 5, and the laser beam is irradiated only to the reduced and projected portion. Therefore, as shown in FIG. The polysilicon portion 3 a is linear corresponding to the transmissive region 32.

  Next, in the second step, the mask 3 is removed, and then the irradiated body 6 is irradiated with laser light, whereby the entire planned area 7 is irradiated with the laser light for each channel area formation planned area 7. . Then, since the melting point of the polysilicon portion 3a is higher than that of the amorphous silicon portion, the polycrystallized portion in the first step does not remelt. In the first step, the portion corresponding to the light-shielding region 31 of the mask 3 in the a-Si: H film remains amorphous. This amorphous portion is melted and solidified by laser irradiation in the second step. To polycrystallize. Since the portion to be polycrystallized in the second step is a portion where the light shielding region 31 in the a-Si: H film is projected in a reduced scale, the polysilicon portion 3b polycrystallized in the second step is the light shielding region 31. Corresponds to the line.

  In this way, in the channel formation planned region 7, first, the portion 3a is polycrystallized to become a polysilicon portion, and then the portion 3b is polycrystallized with a delay. At this time, the amorphous silicon film of the portion 3b Then, the portion 3a is crystallized using the polysilicon film as a nucleus. For this reason, in the portion 3b, crystal grains grow from the portion 3a toward the other portion 3a facing the portion 3b, and the growth of the crystal grains proceeds to an intermediate portion between the two portions 3a. To do. Therefore, after the end of the second step, as shown in FIG. 4, a polysilicon film is obtained in which the growth direction (flat direction) of the crystal grains 9 is aligned in a certain direction in the channel formation scheduled region 7. For this reason, in other channel formation scheduled regions 7, by changing the extending direction of the light shielding region 31 and the transmission region 32 of the mask 3, a polysilicon film having a crystal grain growth direction different from that in FIG. 4 can be obtained. it can. That is, as shown in FIG. 1, the channel formation is performed by appropriately setting the extending directions of the light shielding regions 31 and the transmission regions 32 of the large number of masks 3 provided for each microlens 5 according to the location. The crystal grain growth direction (flattening direction) can be arbitrarily adjusted for each planned region 7. Therefore, unlike the case shown in FIG. 7B, in all the transistors formed in the peripheral circuit, the growth direction of the crystal grains 9 can be matched with the direction in which the current flows. The speed can be increased and the transistor characteristics can be made uniform. Note that one transistor may be formed or a plurality of transistors in which current flows in the same direction may be formed in a channel formation region that is annealed by being irradiated with laser light through each microlens. You can also. That is, one or a plurality of transistors can be formed on one low-temperature polysilicon island formed by one microlens.

  The laser light transmitted through the transmission region 32 of the mask 3 is not irradiated with a width that is strictly reduced at the reduction projection ratio in the channel formation scheduled region 7. In addition, a strictly polycrystalline region is not formed by the irradiation width of the laser beam that is transmitted through the transmission region 32 and applied to the planned region 7. In the amorphous silicon film, there is heat conduction from the part irradiated with laser light to the part not irradiated, non-uniformity of energy density in the part irradiated with laser light, and errors in the reduction projection system also exist. To do. However, in the present embodiment, apart from the strict width of the polysilicon portion 3a, once the polysilicon portion 3a is formed in a linear shape, the next crystallization proceeds with the polysilicon portion 3a as a nucleus. Therefore, in the subsequent crystallization, a polysilicon portion 3b in which the flat direction of crystal grains in a certain direction is aligned is obtained.

  In the above embodiment, the laser light emission conditions, that is, the conditions for heating the a-Si: H film can be the same in the first step and the second step. This light emission condition is that the amorphous silicon film can be melted and solidified by irradiation with laser light. In the above embodiment, since the portion 3a serves as a nucleus at the time of polycrystallization in the portion 3b, in order to make the region where the crystal grains are aligned as wide as possible, the portion 3a is usually a portion. It is assumed that the width is narrower than 3b. Further, the interval between the portions 3a is such that the size of the thin film transistor is about 10 tens μm to several tens of μm in one side length, so that the size of the crystal grains in the channel polysilicon region is 1 μm or less. Preferably. With such small crystal grains (even in the flat direction), more sufficiently stable transistor characteristics can be obtained. Therefore, it is preferable that the interval between the transmission regions 32 of the mask 3 is such that the length of the flat crystal grains is about 1 μm or less in the region projected on the irradiated body 6 in a reduced scale.

  In the first embodiment, the shape of the mask 3 is not limited to a rectangular shape as shown in FIG. 2, and various shapes such as a circle can be used. The direction in which the light shielding region 31 and the transmission region 32 extend is not limited to being parallel to the sides of the rectangular mask 4 and may be inclined. The direction in which the light shielding region 31 and the transmission region 32 extend may be changed for each mask 3.

  In the above-described embodiment, the mask other than the light shielding region that defines the channel region is not used in the second step. However, the mask is used in the second step, and the light shielding is performed in the first step. The portion that was the region was used as the transmission region, and the portion that was the transmission region was used as the light-shielding region. Only the portion that remained amorphous in the first step in the a-Si: H film was irradiated with laser light, and this portion was annealed. It is good to do. In this case, the width of the transmission region in the second step is made larger than the width of the light shielding region in the first step, so that the laser light irradiation region in the second step is larger than the laser light irradiation region in the first step. You may make it larger and overlap in part. Thereby, when the amorphous silicon region is polycrystallized in the second step, the entire region remaining as amorphous silicon can be surely heated, and the polysilicon already polycrystallized in the first step Crystal growth starting from the portion 3a can be promoted.

  Next, a second embodiment of the present invention will be described. In this embodiment, laser light irradiation is performed in one step. In this embodiment, a mask 14 shown in FIG. 8 is used. The mask 14 has basically the same configuration as the mask 3 of the first embodiment, but the mask 14 of the present embodiment has a light-shielding region 141 having a narrow width and a transmissive region 142 having a wide width. The width relationship between the regions is opposite to that of the mask 3. In this embodiment, as shown in FIG. 9, the laser light irradiation conditions are sufficient to melt and polycrystallize the amorphous silicon film portion 14b corresponding to the light shielding region 141. The portion 14 a of the channel formation scheduled region 7 corresponding to the light shielding region 141 is narrow like the width of the light shielding region 141, and the portion 14 b of the channel formation scheduled region 7 corresponding to the transmission region 142 is the width of the transmission region 142. It is as wide as The portion 14a is basically not irradiated with laser light, and the portion 14b is irradiated with laser light. As a result, a temperature difference occurs between the portion 14 a corresponding to the light shielding region 141 and the portion 14 b corresponding to the transmission region 142 in the amorphous silicon film. However, even in the portion 14a that is not irradiated with the laser light, when the portion 14b that is irradiated with the laser light is heated and melted, the heat of the portion 14b is also transmitted to the portion 14a, and the temperature of the portion 14a is also increased. And melt.

  In the present embodiment, heat is transferred from the center of the portion 14b irradiated with the laser light toward the portion 14a that does not receive the irradiation of the two laser beams facing each other across the portion 14b. The portion 14a is melted and solidified by this transfer heat and solidifies to be polycrystallized. However, since this portion 14a has the lowest temperature, it is first solidified from the portion 14a to be polycrystallized. Move sequentially toward. In this case, solidification proceeds under a temperature gradient in which the portion 14a is the lowest and the center of the portion 14b is the highest. Therefore, as shown in FIG. 9, after solidification and polycrystallization, the crystal grains become flattened from the portion 14a toward the center of the portion 14b, and the growth of crystal grains is the same as in the first embodiment. A polysilicon film having a uniform direction can be obtained.

  In the first and second embodiments described above, by using the mask 3 or the mask 14, the crystal grain growth direction is made constant in each channel formation scheduled region 7 corresponding to each mask. A polysilicon film having crystal grains flattened in a certain direction can be obtained. For this reason, the masks 3 and 14 and the microlens 5 are provided for each transistor, and the directions of the light-shielding region and the transmission region in the mask are set appropriately for each mask. Depending on the position of the silicon channel region, the growth direction of the crystal grains can be arbitrarily set. Therefore, in the peripheral circuit of the liquid crystal display device, the crystal grain growth direction can be aligned with the direction in which the channel current flows in the channel region of each transistor, and the resistance and speed of all the transistors in the peripheral circuit can be reduced. In addition, the transistor characteristics can be made uniform.

  At this time, each transistor and each microlens and mask do not correspond to 1: 1, but one or a plurality of transistors can correspond to one set of microlens and mask. That is, the direction in which the driving currents of the plurality of transistors flow can be matched with the direction in which the polysilicon crystal grains extend determined by a set of microlenses and mask. Thus, since the growth direction of crystal grains is aligned with the direction in which the drive current flows in the peripheral circuit, the number of crystal grain boundaries where the drive current intersects can be reduced, thereby reducing the resistance in the direction in which the drive current flows. It can be made small, and low current consumption and high speed can be achieved. In addition, the crystal growth direction is controlled for each channel region by individually setting the direction in which the light-shielding region and transmissive region of the mask corresponding to each microlens extends in accordance with the position irradiated by each microlens. Thus, the growth direction of the crystal grains can be surely matched with the direction in which the channel current of each channel region flows.

  Next, a third embodiment of the present invention will be described. In this embodiment, as shown in FIGS. 10 and 11, the mask 3 corresponding to each microlens 5 is entirely a light shielding region 31 for laser light, and extends in one direction in the light shielding region 31. One linear light-transmitting region 32 is formed. For this reason, one linear laser beam irradiation region is formed in the projection region of the amorphous silicon film, that is, the mask 3 corresponding to each microlens 5 in the irradiation object 6.

  Then, as shown in FIG. 12, the linear irradiation region 3c is scanned in a direction perpendicular to the one direction in which the line extends. For example, a laser beam irradiation system including a microlens 5 and a mask 3 of a laser irradiation apparatus is fixed, and a substrate (irradiated body 6) on which an amorphous silicon film is formed is oriented in a direction perpendicular to the one direction. The substrate may be fixed and the laser light irradiation system may be moved in a direction perpendicular to the one direction.

  Then, the amorphous silicon film is melted in the laser light irradiation region 3c, and then, when the irradiation region 3c moves by scanning and moves in the direction of the arrow in the figure, the heat source leaves, so it is once melted. The part is rapidly cooled and solidifies and crystallizes. As a result, crystal grains 9 grown in a direction perpendicular to the one direction are formed behind the linear irradiation region 3c of the laser beam that is moved by scanning.

  Therefore, also in this embodiment, the growth direction of crystal grains is made uniform in a certain direction in a minute region (for example, a region where one transistor is to be formed) corresponding to each microlens in the irradiation object 6.

  The present invention is not limited to one microlens corresponding to the channel region of one transistor formation region, but a laser so that one microlens corresponds to a plurality of transistor formation regions. You may irradiate light.

  The present invention is useful for manufacturing a semiconductor device having stable transistor characteristics.

1: laser light source 3, 14: mask 3a: (polycrystalline) portion 3b: (amorphous) portion 3c: laser light irradiation regions 4a, 4b, 4c: transparent substrate 5: microlens 6: irradiated object 7: channel region formation Planned area 8: Transmission member 9: Crystal grain 31, 141: Light shielding area 32, 142: Transmission area

Claims (9)

A plurality of microlenses arranged one-dimensionally or two-dimensionally, a generation source of laser light, laser light from the generation source is guided to the microlens, and the laser light is collected on the amorphous silicon film by the microlens. And a plurality of masks arranged for each microlens, and each mask has a light shielding region for shielding the laser light and a transmission region for transmitting the laser light. The low-temperature polysilicon film forming apparatus is characterized in that both are provided so as to extend in one direction and to be adjacent in a direction perpendicular to the one direction. 2. The formation of a low-temperature polysilicon film according to claim 1, wherein a plurality of the light shielding regions and the transmission regions are provided for each mask, and the light shielding regions and the transmission regions are alternately arranged. apparatus. 3. One or a plurality of transistors are formed in each polysilicon film formed by annealing an amorphous silicon film with laser light that has passed through each microlens. The low-temperature polysilicon film forming apparatus described in 1. The low-temperature polysilicon film forming apparatus according to any one of claims 1 to 3, wherein the amorphous silicon film is irradiated with laser light from the microlens through the mask first, thereby transmitting the transmission region. A first step of irradiating the amorphous silicon film with a laser beam that has passed through and forming a polysilicon region, and then irradiating the amorphous silicon film with the laser beam by the microlens without using the mask. And a second step of polycrystallizing the remaining amorphous silicon film using the polysilicon film as a crystal nucleus, and forming a low-temperature polysilicon film. 5. The method of forming a low-temperature polysilicon film according to claim 4, wherein the first step and the second step have the same laser light emission conditions by the laser light source. Using the low-temperature polysilicon film forming apparatus according to any one of claims 1 to 3, and irradiating an amorphous silicon film with laser light through the mask by the microlens, The irradiation condition of the laser beam is sufficient for the portion of the amorphous silicon film corresponding to the light shielding region to be melted and polycrystallized, and the portion corresponding to the light shielding region in the amorphous silicon film upon polycrystallization And a portion corresponding to the transmissive region has a temperature difference. A method of forming a low-temperature polysilicon film in a peripheral circuit of a liquid crystal display device, wherein a microlens is associated with each transistor group of one or more transistors in the peripheral circuit, and the one direction of the mask 7. The method for forming a low-temperature polysilicon film according to claim 4, wherein the crystallization direction of the amorphous silicon film of the transistor group is adjusted by determining according to the transistor group. A plurality of microlenses arranged one-dimensionally or two-dimensionally, a generation source of laser light, laser light from the generation source is guided to the microlens, and the laser light is collected on the amorphous silicon film by the microlens. A light guide portion that emits light, and a plurality of masks arranged for each microlens, wherein each mask transmits the laser light in a light shielding region that shields the laser light. In the projection region on the amorphous silicon film on which the mask is projected by the microlens, the transmission device uses a low-temperature polysilicon film forming apparatus in which one linear transmission region extending in the direction is provided. A method of forming a low-temperature polysilicon film, wherein linear laser light transmitted through a region scans the projection region in a direction perpendicular to the one direction. The laser light is scanned in the projection region by relatively moving the laser light irradiation system including the microlens and the mask of the low-temperature polysilicon forming apparatus and the substrate on which the amorphous silicon film is formed. The method of forming a low-temperature polysilicon film according to claim 8.

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