JP2002313725A - Laser annealing method for semiconductor film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excimer laser annealing method(ELA) for obtaining a p-Si good in crystallinity in the ELA for forming the p-Si for p-Si TFT LCDs. SOLUTION: In a scanning direction of a laser beam, it has an energy region exceeding a threshold energy Eth which maximizes the grain size comparatively in the front of a beam profile and an energy region not exceeding the threshold energy at sufficiently back. As the beam moves, the irradiation energy goes from up to down the threshold energy level and, in this process, the best annealing is performed in an energy region sufficiently increasing the grain size just under the threshold energy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly, to a liquid crystal display (LCD).
The present invention relates to a method of manufacturing a peripheral drive circuit integrated type LCD in which a thin film transistor (TFT) using a polycrystalline semiconductor layer is formed in a display portion and a peripheral portion.

[0002]

2. Description of the Related Art In recent years, LCDs have been put to practical use in the fields of OA equipment, AV equipment, and the like due to their advantages of small size, thinness, low power consumption, and the like. TFT as switching element to control
The active matrix type in which is disposed is capable of displaying a large screen and a high-definition moving image, and is therefore used for displays of various televisions and personal computers.

A TFT is a field effect transistor (FET) obtained by forming a semiconductor layer in a predetermined shape together with a metal layer on an insulating substrate.
tor). In an active matrix LCD, a TFT is connected to one electrode of each capacitor, which is a pixel for driving liquid crystal, formed between a pair of substrates sandwiching liquid crystal.

In particular, LCDs using polycrystalline silicon (p-Si) as a semiconductor layer instead of amorphous silicon (a-Si), which has been widely used, have been developed.
Annealing using laser beam irradiation has been performed to form or grow Si crystal grains (grains).
Generally, p-Si has higher mobility than a-Si,
The FT is downsized, and a high aperture ratio and high definition are realized. In addition, since miniaturization by the gate self-aligned structure and speeding-up by reducing the parasitic capacitance are achieved, the n-ch
Electrically Complementary Connection Structure of TFT and p-ch TFT, That is, CM
By forming the OS, a high-speed driving circuit can be formed. Therefore, by forming the drive circuit portion integrally with the display pixel portion on the same substrate, reduction in manufacturing cost,
The size of the LCD module can be reduced.

As a method of forming p-Si on an insulating substrate, there are a recrystallization by annealing a-Si generated at a low temperature at a high temperature, and a solid phase growth method at a high temperature. In any case, since the treatment is performed at 900 ° C. or higher, an inexpensive alkali-free glass substrate cannot be used as an insulating substrate in terms of heat resistance. For this reason, an expensive quartz glass substrate is required as a substrate, which is costly. In contrast, using laser annealing,
A method of using a non-alkali glass substrate as an insulating substrate by performing silicon crystallization at a relatively low temperature of 600 ° C. or lower has been developed. A process in which the processing temperature is set to 600 ° C. or lower in all the steps of manufacturing a TFT substrate is called a low-temperature process, and is an essential process for mass production of low-cost LCDs.

FIG. 22 is a configuration diagram of a laser beam irradiation apparatus for performing such laser annealing. In the figure,
(51) is a laser beam oscillation source, (52, 61) is a mirror, (53, 54, 55, 56) is a cylindrical lens, (57, 58, 59, 62, 63) is a condenser lens,
(60) is a slit in the line width direction, and (65) is a slit in the line length direction. (64) is a stage for supporting the substrate (70) on which a-Si is formed on the surface.

The laser light is, for example, an excimer laser, and the laser light emitted from the laser light source (51) is transmitted by two sets of condenser lenses composed of cylindrical lenses (53, 55) and (54, 56). The output distribution of the irradiation energy in each of the vertical and horizontal directions is transformed into flat parallel light. As shown in FIG. 23, the parallel light is transmitted through lenses (58, 59, 62, 63).
Is converged in one direction, and as shown in FIG. 24, is elongated in another direction by a lens (57).
The region to be irradiated is shaped into a band-like line and is irradiated onto the substrate to be processed (70). Also, slits (60, 65)
Is to clearly define the shape of the irradiation area by blocking both end portions in the line width and line length directions, and to make the intensity of the effective irradiation area constant. The stage (64) on which the substrate to be processed (70) is mounted is movable in the (X, Y) direction, is scanned by an irradiation line beam, performs large-area processing, and realizes high-throughput laser annealing. . In the present apparatus, it is possible to irradiate a sheet beam in which the irradiation area is shaped into a rectangle or a square, etc., by designing an optical system such as a lens.

FIG. 25 shows a state of a substrate to be processed in excimer laser annealing (hereinafter referred to as ELA) using the apparatus shown in FIG. The substrate to be processed (1) is an ordinary non-alkali glass substrate, and a-Si is formed on the surface thereof. The substrate (1) includes a pixel portion (2) in which display pixels are arranged in a matrix, a gate driver (3) and a drain driver (4) to be arranged around the pixel portion (2). Is a mother glass substrate that includes a plurality of active matrix substrates (5) constituting an LCD made of the liquid crystal display. In the pixel portion (2), display electrodes, which are one electrode of a pixel capacitor for driving liquid crystal, are arranged and formed in a matrix, and a TFT is connected to each of them. The gate driver (3) mainly consists of a shift register, and the drain driver (4) mainly consists of a shift register and a sample and hold circuit. These drivers are formed by an array of TFTs such as CMOS.

Each TFT is, as shown in FIG.
Is formed using p-Si obtained by crystallization from a-Si as an operation layer. That is, a non-doped channel region (CH), a lightly doped LD region (LD), and a heavily doped source / drain region (S, D) are formed in the p-Si (11) etched in an island shape.
A gate electrode (13) is provided on the channel region (CH) with a gate insulating film interposed therebetween. A source electrode and a drain electrode are connected to the source and drain regions (S, D), respectively. Wiring such as CMOS is formed in the peripheral driver circuit portion, and a connection structure to the signal line and the pixel electrode is formed in the pixel portion. Is done.

[0010]

The line beam generated by the apparatus shown in FIG. 22 is shown in FIG. 25 in such a manner that the edge line of the band-shaped irradiated area on the substrate (1) is indicated by C in FIG. By shifting the irradiation laser pulse by a predetermined overlap amount, scanning is performed as indicated by an arrow, and the whole is annealed. However,
After such a line beam is scanned, the formed p
In the -Si, as shown by R in the figure, crystallization is not sufficiently performed, and a poorly crystallized region in which the grain remains small is formed in a line shape along the long direction of the line of the irradiated region, It was present with a striped pattern. Since the poor crystallization region (R) has low mobility and high resistance, the TFT formed in this region has poor characteristics. When the characteristics of the TFT are deteriorated, in the pixel portion, the pixel capacitor is not sufficiently charged and the contrast ratio is lowered, and in the peripheral drive circuit portion, a malfunction is caused.

The occurrence of such a poor crystallization region (R) is presumed to be caused by the variation in the energy of the irradiation laser beam as shown in FIG. The figure shows
3 shows an energy profile related to an irradiation position in a scanning direction of a laser beam. At both ends of the line width A, the energy is reduced due to light diffraction or the like, and the edges are blurred over the width B. In laser annealing, the grain size increases as the irradiation energy increases, but decreases rapidly beyond a certain value. For this reason, if the energy Eu exceeds the sharply reduced grain size Eu as shown by X in the figure due to the variation in the irradiation laser energy, the corresponding region becomes a poorly crystallized region (R).

In an optical system composed of a plurality of lenses as shown in FIG. 22, diffraction, scattering, interference, etc. of light occur due to minute irregularities or foreign matter present on the lens surface.
Further, the light is condensed in the line width direction and is elongated in the line length direction, so that a thinner line-shaped poorly crystallized region may be generated in the line-shaped irradiated region. For example, even if there is a small amount of foreign matter adhering to the lens surface in the clean room, it has a great effect during laser annealing.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and a laser annealing method of a semiconductor film for improving the film quality by irradiating a semiconductor film on a substrate with a laser beam. The energy change in the irradiated region is a laser annealing method for a semiconductor film that changes in the order of an edge, a relatively high crystallization region, a relatively low crystallization region, and an edge. In the laser annealing method for a semiconductor film in which an amorphous semiconductor film on a substrate is irradiated with a laser beam to obtain a polycrystalline semiconductor film, a change in energy of a position in a region to be irradiated with the laser beam is relatively high at an edge. This is a laser annealing method for a semiconductor film that changes in the order of a crystallization region, a relatively low crystallization region, and an edge. Further, the relatively low crystallization region of the laser beam is a method for laser annealing a semiconductor film that is sufficiently smaller than an energy value that maximizes a crystal grain size.

As described above, after the high-energy portion located relatively forward in the traveling direction of the laser beam passes through the semiconductor layer, an energy portion smaller than the high-energy portion sequentially passes. For this reason, after large crystal grains are initially formed with large energy, crystallization of the remaining poorly crystallized region is performed with relatively small energy while maintaining the large crystal grains previously formed, and the crystallinity is reduced. Improvement is achieved.

[0015] Further, it is possible to prevent the semiconductor crystal from being re-amorphized when the energy exceeds a value that maximizes the crystal grain size sufficiently behind the irradiation laser beam passing through the semiconductor layer in the traveling direction. Since the crystallization of a region having poor crystallinity is performed to some extent, a polycrystalline semiconductor layer having a substantially uniform crystal grain size over the entire region is obtained.

Further, the irradiation laser beam passing over the semiconductor layer is annealed before exceeding the energy near the threshold value for maximizing the crystal grain size, but thereafter the energy gradually decreases, and the threshold energy decreases. Annealing with a sufficiently high optimum energy that does not exceed the maximum, ie, the best annealing in an energy range where the crystal grain size is sufficiently large. Therefore, a polycrystalline semiconductor layer having a large crystal grain size and excellent uniformity is formed. Further, in the method for laser annealing a semiconductor film of the present invention, the laser beam is obtained by shaping a laser beam emitted from an oscillation source into a predetermined shape in an irradiation area thereof by an optical system including a plurality of lenses, A laser annealing method for a semiconductor film in which energy related to a position in a region to be irradiated with the laser beam is controlled by adjusting a distance between an amorphous semiconductor film on a substrate and a focal position of the optical system.

By changing the distance between the substrate on which the amorphous semiconductor film to be laser-annealed is formed and the focal position of the optical system, a laser beam having a suitable irradiation position-energy distribution can be obtained. And good laser annealing is performed.

[0018]

FIG. 1 is a plan view showing a state of a substrate to be processed in an ELA according to an embodiment of the present invention. The substrate to be processed (1) is an ordinary non-alkali glass substrate, and a-Si is formed on the surface thereof. The substrate (1) constitutes an LCD comprising a pixel section (2) in which display pixels are arranged in a matrix and a gate driver (3) and a drain driver (4) arranged around the pixel section (2). The mother glass substrate includes six active matrix substrates (5). The pixel portion (2) has a structure in which display electrodes, which are one electrode of a pixel capacitor for driving liquid crystal, are arranged in a matrix and a TFT is connected to each of them. The gate driver (3) mainly consists of a shift register, and the drain driver (4) mainly consists of a shift register and a sample and hold circuit. These drivers are formed by an array of TFTs such as a CMOS.
The FT is formed by using p-Si formed by the ELA method of the present invention for the channel and the source / drain layers.

ELA is irradiation of a line (sheet) beam and scanning thereof realized by the laser light irradiation apparatus shown in FIG. In FIG. 1, a line beam is applied to the substrate (1) with a predetermined overlap so that each line-shaped irradiation laser pulse has a predetermined overlap, as shown by C in FIG. , The scanning is performed as shown by the arrow in the figure, and the entire surface is annealed. In the ELA apparatus shown in FIG. 22, for example, the line beam has a line length of 80 to 300.
mm, the line width is about 0.1 to 1 mm, and this line is moved on the substrate to be processed (1), and is scanned a plurality of times (here, twice) in the line width direction to obtain the substrate ( The entire area of 1) is annealed to enable large area processing.

FIG. 2 is a beam profile showing the position-energy relationship of the irradiation line (sheet) beam in the line (sheet) width direction according to the embodiment of the present invention.
5 to FIG. FIG. 2 shows a case where a basic beam profile is shaped into a trapezoid, and FIG. 3 shows a case where one edge is blurred in the same trapezoidal beam profile.
5 shows a case where the beam profile is not clearly defined. In any case, the energy exceeds the threshold energy Eth for microcrystallizing silicon grains relatively forward in the traveling direction of scanning of the beam, and the energy does not exceed the threshold energy Eth behind it. ing. For this reason, the best laser annealing is performed by the optimal region (GR) of the beam which is just below the threshold energy and within the energy range for obtaining a sufficiently large grain size.

FIG. 6 shows the relationship between the crystallinity and the film temperature during laser irradiation in ELA. The temperature is a value measured by optical observation of a well-known lattice state such as a pyrometer, and is related to the energy of ELA. In the figure, the crystallization mode of the starting film, a-Si,
It is shown that the film temperature increases as time elapses after the start of each irradiation, and decreases after the irradiation ends. In FIG. 7A, the highest point of the film temperature does not exceed the polycrystallization temperature Tg, which is the film temperature at which the grains start to be formed, and the film temperature decreases and remains a-Si even after inactivation. ing. In b, the highest temperature of the film temperature exceeds the polycrystallization temperature Tg, and after the film temperature is lowered and inactivated, p-Si (S) having a small grain size is formed. c
In this case, the highest point of the film temperature is further increased, and p-Si (L) having a large grain size is formed. And in d,
After the start of irradiation, the temperature exceeds the polycrystallization temperature Tg, and further exceeds the microcrystallization temperature TM at which the grains are reduced, and after the temperature is lowered and inactivated, the microcrystal silicon, that is, microcrystal (M-cry) Is formed. These, a,
The difference between b, c, and d appears due to the ELA energy. P-Si with large grain size by performing good annealing
It can be seen that in order to obtain (L), it is necessary to raise the temperature as high as possible without exceeding the film temperature TM.

FIG. 7 shows the relationship between the irradiation time, that is, the number of shots of the irradiation laser pulse and the grain size. FIG.
, The grain size increases as the number of shots and the ELA energy increase. However, the increase in the grain size is large up to the first few shots, and thereafter, the grain size gradually increases.

Such a property of ELA was derived from the following experiment and its consideration.

First, as described later in detail, a p-Si film formed by relatively high energy ELA was subjected to Secco etching, and the film state was examined by SEM, optical microscope, etc., and as a result, as shown in FIG. The properties of ELA were found. The upper part of the figure is a beam profile showing the relationship between the irradiation position of the laser beam and the energy, where the position is the width direction of the line beam, that is, the front and rear positions with respect to the traveling direction, and the temperature is the film measured by optical observation of the lattice state Temperature is related to beam energy. The lower part of the figure is a state diagram of the ELA processing film corresponding to the beam profile. The beam profile has a trapezoidal shape, the top of which has exceeded the microcrystallization temperature TM, and the film state corresponding to this is microcrystal (M-cry). In addition, on the side of the trapezoidal profile, the film temperature is a straight line or a steep slope with a gentle curve. With respect to the position, the film temperature rises as it approaches the top, that is, the microcrystal region, and the polycrystallization temperature Tg, Next, the temperature exceeds the microcrystallization temperature TM. The state of the outermost film to be processed corresponding to a temperature region equal to or lower than the polycrystallization temperature Tg of the beam profile is a-Si, and is in a temperature region from the polycrystallization temperature Tg to the microcrystallization temperature TM. The corresponding film state to be processed is p-Si. However, p-S
The grain size of i increases continuously from the a-Si region as the film temperature rises above Tg. The most characteristic point is that the grain size increases as the temperature rises up to the film temperature TM, but when the temperature exceeds the film temperature TM, the grain size sharply decreases to form microcrystals. Then, it can be seen that the maximum grain size is obtained in the highest temperature region MX not exceeding the film temperature TM.

FIG. 9 shows a film state diagram (middle stage) found by scanning a line beam having the energy profile shown in FIG. 8 and observing the film to be processed with an optical microscope.
FIG. 11 is a corresponding diagram (lower part) of the corresponding relationship between the beam scanning advancing direction position and the grain size. The line beam whose energy profile is shown in the upper part shows that each irradiation laser pulse position is sequentially shifted from the left side of the figure and advances, and is presently at the illustrated position. In this experiment, line beam scanning was performed by 20 shots overprinting with 95% laser pulse overlap. In each shot of the laser pulse, a film corresponding to the MX region at the edge portion of the beam profile is formed with p-Si having a sufficiently large grain size GM sequentially, but at the same time, a film located forward of the MX region of the energy profile in the traveling direction. M-cry is formed in a temperature region equal to or higher than the temperature TM, and has a striped pattern. That is, the M-cry formed in the earlier shot is crystallized by the subsequent shot, but has the largest grain size GM.
In the film region, the temperature region MX is only p-Si formed in a thin line shape. In other regions, the grain size of the previously formed M-cry is further increased. Energy is not given. Note that there is also an MX region for obtaining a sufficiently large grain size GM at the front edge in the scanning direction of the beam profile, but M-cry is formed while the top of the subsequent beam profile passes.

Further, the p-Si film formed by the relatively low energy ELA was subjected to secco etching and optical observation using an SEM, an optical microscope or the like was performed. As a result, the ELA shown in FIG.
I understood the nature of As in FIG. 8, the upper part of the figure is an energy profile related to the irradiation position in the laser beam scanning traveling direction, and the lower part is a state diagram of the ELA processing film corresponding to this beam profile. Although the beam profile has a trapezoidal shape, since the energy is relatively low, the top does not exceed the microcrystallization temperature TM, and is not so large in the film region corresponding to the temperature region exceeding the polycrystallization temperature Tg. No grain size p
-Si is formed. Below the polycrystallization temperature Tg, a
-Si region.

FIG. 11 is a film state diagram (middle stage) found by scanning a line beam having the energy profile shown in FIG. 10 and observing the film to be processed with an optical microscope.
FIG. 4 is a diagram (lower part) showing a relationship between a beam scanning advancing direction position and a grain size corresponding thereto. The line beam whose energy profile is shown in the upper part of FIG.
In the same manner as in the above, the laser beam is advanced from the left side of the drawing and is at the position shown in the drawing by 20 shots of 95% laser pulse overlap scanning. In this case, since the laser energy does not exceed the microcrystallization temperature TM, no microcrystal is formed by re-amorphization, and the crystal is crystallized as the number of shots increases, and the grain size increases. Go. After the p-Si having the grain size Gg is formed in the first four shots, the grain size relatively increases gradually as the shots are stacked. At the twelfth shot, the maximum grain size Gp obtained by this ELA energy is obtained, and there is no significant change thereafter.

The following has been found from the above experiments. EL
In A, in order to increase the grain size of silicon, it is necessary to increase the energy. However, if the energy value exceeds a certain value, re-amorphization occurs, and the grain size decreases sharply to generate microcrystals. You. That is, as shown in FIG. 12, the relationship between the ELA energy and the grain size is shown. As the energy increases, the grain size increases. When the energy exceeds the energy Ed for obtaining a sufficiently large grain size GM, the grain size increases. Will be the largest. As the energy is further increased, the grain size decreases and eventually decreases rapidly. Here, it is not known whether the threshold energy and the energy for maximizing the grain size are exactly the same, but the energy for maximizing the grain size is extremely close to the threshold energy, and In the following description, the energy that maximizes the grain size and the threshold energy that sharply reduces the grain size are considered to be practically the same, and the following description will mainly focus on the threshold energy. .

From FIG. 12, it is sufficient that the energy is within the range between Ed and Eu in order to obtain the grain size GM or more. In particular, in order to obtain the maximum grain size,
It can be seen from the shape of the relationship curve in the figure that the laser energy should be as large as possible within a range not exceeding the re-amorphization threshold energy. However, as shown in FIG. 27, since the variation in the irradiation laser energy is inevitable, when the grain size exceeds the threshold energy at which the grain size sharply decreases, the corresponding region becomes a poorly crystallized region. This degrades the characteristics of the TFT formed in this region.

Therefore, as shown in FIGS. 2 to 5, the threshold energy Eth at which the grain size is sharply reduced, the energy gradually decreases from the front to the rear in the scanning direction of the irradiation laser beam, and the profile decreases. By setting the energy profile so that the edge crosses from a region above the threshold energy Eth to a region below the threshold energy Eth, good ELA is performed. That is, since the energy exceeds the threshold energy Eth in front of the beam profile, annealing is performed with the maximum energy not exceeding the threshold energy Eth in a region (GR) immediately after the intersection of the profile edge with the threshold energy Eth. , A p-Si film having the largest grain size is formed. In other words, in the energy region immediately below the threshold energy Eth at which the grain size is sharply reduced, there is an energy region (GR) where the grain size is maximized. Microcrystals are formed in a region exceeding the threshold energy Eth in front of the GR region, but the grain size is maximized by passing the GR region thereafter. In addition, since the threshold energy Eth does not exceed the rear of the GR region, the once formed grains are not microcrystallized. Therefore, by setting the amount of overlap and the pulse frequency so that the GR region is shot a predetermined number of times in the same region of the film to be processed, good annealing is performed over the entire region of the film to be processed, and the maximum grain size is reduced. It becomes possible to form a p-Si film.

[0031]

FIG. 13 shows a first embodiment of the present invention.
5 is a beam profile when the distance between the focal position of the laser beam and the substrate to be processed is set to 300 μm in the ELA apparatus of FIG. On the left side of the profile, it has a shape in which energy jumps. FIG.
14 is an optical microscope photograph when scanning is performed with the traveling direction of the line beam having the energy profile of FIG. By performing Seco etch so that the interference light resulting from the difference in grain size represents a different color,
The state of the film can be examined. (A) and (b) of FIG.
(C) shows an energy of 390 mJ / square cm and 40, respectively.
0 mJ / square cm and 410 mJ / square cm. Further, FIG. 15 is a similar optical microscope photograph when scanning is performed with the traveling direction of the line beam in FIG. FIG. 14 shows that the p-Si
It can be seen that a film has been obtained. In contrast, FIG.
In (a) and (b), it is recognized that the poorly-crystallized region is vertically striped black. In (c), furthermore, the poorly crystallized region is conspicuous in black, which indicates that the film quality is considerably poor.

The following can be inferred from these observations.
That is, in the line beam whose energy profile is shown in FIG. 13, the portion where the energy jumps up easily exceeds the microcrystallization temperature, that is, the threshold energy Eth at which the grain size is sharply reduced. In particular, the higher the laser energy, the higher the laser energy. , The probability increases. For this reason, the line beam traveling rightward in FIG. 13 is annealed while performing microcrystallization at the rear end of the irradiation region, so that p-Si formed in front of the beam is converted into microcrystals behind the beam. Then, as shown in FIG. 15, it remains as a poor crystallization region. Such a problem is more likely to occur as the energy is higher, and causes a problem that microcrystals are generated instead if a large grain size is to be obtained.

On the other hand, when the traveling direction of the line beam is set to the left direction in FIG. 13, microcrystals are easily generated in front of the beam. Good crystallization is performed in the energy region, and a large grain size p
-Si is formed. In FIG. 14 (c), it is recognized that the poorly crystallized region is slightly blackened, and it can be seen that there is a threshold energy Eth at which the laser energy sharply decreases near 410 mJ / cm 2.

Therefore, the line beam whose energy profile is shown in FIG. 13 has an energy of 410 mJ /
It can be seen that the best crystallization annealing can be performed by setting the scanning direction to about square cm and taking the traveling direction to the left in the figure. That is, at this time, a microcrystal is formed at the front of the beam, and thereafter, from the center of the beam to the rear, from the energy region higher than the threshold energy Eth for rapidly reducing the grain size,
There is a portion that shifts to an energy region lower than the threshold energy Eth, and there is an optimum beam region (GR) where the best annealing is performed, as shown in FIG.
In this embodiment, 20 shots are overshot, and the number of shots in the optimum beam area (GR) is smaller than that. However, as shown in FIG. 6, FIG. 7, and FIG. Since it is almost completed in a few shots,
By appropriately setting the overlap amount and frequency of the laser pulse so that a desired number of shots can be obtained, favorable annealing can be performed.

Next, as a second embodiment, FIG.
2 is a beam profile when the distance between the focal position of the laser beam and the substrate to be processed is set to 600 μm in the ELA apparatus No. 2. As described above, by changing the focal length, the beam profile can be deformed by utilizing the minute deviation of light at the time of diffraction and interference. FIG.
Is a photomicrograph when the traveling direction of the line beam whose energy profile is shown in FIG. 16 is taken to the left of the figure,
FIG. 18 is also a right-side micrograph. 17 and 18, (a), (b), and (c) show the cases where the laser energy is 390 mJ / square cm, 400 mJ / square cm, and 410 mJ / square cm, respectively. Both figures show favorable crystal states in (a) and (b), but in comparison with (c), poorly crystallized regions are conspicuous in FIG. That is, energy 410 mJ / square c
In the vicinity of m, there is a threshold energy that sharply reduces the grain size. In this beam profile, as shown in FIG. 16, since there is a region where the energy is relatively high on the right side, when scanning to the left, a microcrystal is formed at the rear of the laser beam, and then the grain is formed. The optimum beam region (GR) for performing good annealing immediately below the threshold energy Eth for rapidly reducing the size is shortened, and the microcrystal is not sufficiently crystallized, and a poorly crystallized region is generated as shown in FIG. Would.

On the other hand, when the line beam is scanned rightward, at the beginning of the laser energy irradiation,
Threshold energy Eth for rapidly reducing grain size
Since the optimum beam region (GR) in which the best annealing immediately below the threshold energy Eth is performed becomes sufficiently long as in FIG. 4, the crystallinity as shown in FIG. As a result, a p-Si film can be obtained.

Next, as a third embodiment, FIG.
This is a beam profile when the distance between the focal position of the laser and the substrate to be processed is 900 μm. FIGS. 20 and 21 are micrographs when the traveling direction of the line beam having the energy profile of FIG. 19 is taken to the left and right, respectively. (A), (b) and (c) show that the laser energy was 390 mJ /
Square cm, 400 mJ / square cm, 410 mJ / square c
m. Both FIG. 20 and FIG. 21 show good crystallinity. Looking at the beam profile in FIG. 19, there is a part where the energy protrudes slightly to the right in the center,
With this as the top, the energy gradually decreases on both sides, and the shape is similar to FIG. Therefore, regardless of whether the scanning direction of the line beam is the left direction or the right direction, the energy E that maximizes the grain size is obtained.
There is an optimum beam region (GR) for sufficiently increasing the grain size, which transitions from a region higher than th to a region lower than the energy Eth, and favorable annealing is performed.

[0038]

As is apparent from the above description, the present invention relates to a method of manufacturing a semiconductor device using a polycrystalline semiconductor layer obtained by crystallizing an amorphous semiconductor layer formed on a substrate by laser annealing. With respect to the scanning progress position of the irradiation laser beam, there is an energy region that exceeds the threshold energy that maximizes the grain size relatively ahead, and an energy region that does not exceed the threshold energy that maximizes the grain size sufficiently behind. Is irradiated with a laser beam exhibiting a position-energy relationship profile in which. Thereby, the best annealing is performed in an energy region just below the threshold energy and in which the grain size is sufficiently large, and a polycrystalline semiconductor layer with extremely good crystallinity can be formed.
Therefore, in a driving circuit integrated type liquid crystal display device in which a peripheral driving circuit portion is formed on the same substrate together with a pixel portion, characteristics of a polycrystalline silicon thin film transistor forming the pixel portion and the driving circuit portion are improved, and display with high display quality is achieved. A device is obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a substrate to be processed during ELA according to an embodiment of the present invention.

FIG. 2 is a beam profile showing a position-energy relationship of a laser beam in a scanning traveling direction according to an embodiment of the present invention.

FIG. 3 is a beam profile showing a position-energy relationship in a scanning traveling direction of a laser beam according to the embodiment of the present invention.

FIG. 4 is a beam profile showing a position-energy relationship in a scanning traveling direction of a laser beam according to the embodiment of the present invention.

FIG. 5 is a beam profile showing a position-energy relationship in a scanning traveling direction of a laser beam according to the embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between irradiation time (number of pulse shots) and film temperature in ELA according to the embodiment of the present invention.

FIG. 7 is a graph showing a relationship between irradiation time (number of pulse shots) and grain size in ELA according to the embodiment of the present invention.

FIG. 8 is a diagram showing a correspondence relationship between a beam profile and a film state in ELA according to the embodiment of the present invention.

FIG. 9 is a correspondence diagram of a beam profile, a film state, and a position-grain size relationship in ELA according to the embodiment of the present invention.

FIG. 10 is a diagram showing a correspondence relationship between a beam profile and a film state in ELA according to the embodiment of the present invention.

FIG. 11 is a correspondence diagram of a beam profile, a film state, and a position-grain size relationship in ELA according to the embodiment of the present invention.

FIG. 12 is a graph showing a relationship between laser energy and grain size in ELA according to the embodiment of the present invention.

FIG. 13 is a beam profile showing a position-energy relationship in ELA according to the first example of the present invention.

FIG. 14 is a micrograph of a p-Si film formed by ELA according to the first example of the present invention.

FIG. 15 is a micrograph of a p-Si film formed by ELA according to the first example of the present invention.

FIG. 16 is a beam profile showing a position-energy relationship in ELA according to the second example of the present invention.

FIG. 17 is a photomicrograph of a p-Si film formed by ELA according to the second example of the present invention.

FIG. 18 is a photomicrograph of a p-Si film formed by ELA according to the second example of the present invention.

FIG. 19 is a beam profile showing a position-energy relationship in ELA according to the third example of the present invention.

FIG. 20 is a micrograph of a p-Si film formed by ELA according to a third example of the present invention.

FIG. 21 is a photomicrograph of a p-Si film formed by ELA according to a third example of the present invention.

FIG. 22 is a plan view of a substrate to be processed in a conventional ELA.

FIG. 23 is a configuration diagram of an ELA apparatus.

FIG. 24 is a diagram illustrating the principle of the optical system of the ELA apparatus.

FIG. 25 is a diagram illustrating the principle of an optical system of an ELA apparatus.

FIG. 26 is a plan view of a TFT section.

FIG. 27 is a beam profile showing an irradiation position-energy relationship in ELA.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate to be processed 2 Pixel part 3 Gate driver 4 Drain driver 5 Active matrix substrate CH Channel region D Drain region S Source region

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kiyoshi Yoneda 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Yoshihiro Morimoto 2-chome Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Tsutomu Yamada 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture (72) Inventor Kazuhiro Imao 2 Keihan Motodori, Moriguchi City, Osaka Prefecture 5-5-5 Sanyo Electric Co., Ltd. (72) Inventor Takashi Kuwahara 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term (reference) 2H092 JA24 JA34 JA37 JA41 JB69 KA04 KA05 MA29 MA30 NA25 PA01 PA07 5F052 AA02 BA01 BA02 BA04 BA07 BB07 DA01 JA01 5F110 AA01 AA30 BB02 BB04 DD02 GG02 GG13 NN72 PP03 PP05 PP06

Claims (5)

[Claims] 1. A laser annealing method for a semiconductor film, in which a semiconductor film on a substrate is irradiated with a laser beam to improve the film quality, the energy change in a region to be irradiated with the laser beam includes an edge, a relatively high crystallization region, A laser annealing method characterized by transition in the order of a relatively low crystallization region and an edge. 2. A laser annealing method for a semiconductor film in which a polycrystalline semiconductor film is obtained by irradiating an amorphous semiconductor film on a substrate with a laser beam, wherein a change in energy with respect to a position in a region to be irradiated with the laser beam is an edge, A laser annealing method characterized by transitioning in the order of a relatively high crystallization region, a relatively low crystallization region, and an edge. 3. The laser beam according to claim 1, wherein the relatively low crystallization region of the laser beam is sufficiently smaller than an energy value for maximizing a crystal grain size.
The laser annealing method according to the above. 4. The method according to claim 1, wherein the relatively high crystallization area of the laser beam is equal to or exceeds the energy for maximizing the crystal grain size. Laser annealing method. 5. The laser beam obtained by shaping a laser beam emitted from an oscillating source into a predetermined shape in a region to be irradiated by an optical system including a plurality of lenses, and forming an amorphous semiconductor film on the substrate. The laser according to claim 1, wherein an energy of a position of the laser beam in a region to be irradiated with the laser beam is controlled by adjusting a distance between the laser beam and a focal position of the optical system. Annealing method.