JP2014072496A - Manufacturing method of crystal semiconductor film, and manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of irradiation non-uniformity when crystallizing a non-single crystal semiconductor film by irradiating it with a pulse laser.SOLUTION: A manufacturing method of a crystal semiconductor film includes: a first step of irradiation with a pulse laser of an irradiation pulse energy density E1 which is lower than such an irradiation pulse energy density as to finely crystallize a non-single semiconductor film by irradiating it with a pulse laser and equal to an irradiation pulse energy density E0 when an irradiation pulse energy density suitable for crystallization by irradiation of multiple times N is defined as E0; and a second step of irradiation with the pulse laser of irradiation pulse energy E2 which is lower than the irradiation pulse energy E1 and equal to or higher than an irradiation energy density required for remelting the crystal. The total number of times of irradiation to the same irradiation surface in the first step and the second step is made equal to or more than N times.

Description

  The present invention relates to a method for producing a crystalline semiconductor film in which a semiconductor laser is crystallized or modified by moving a pulse laser having a rectangular cross section while being irradiated with a plurality of times (overlap irradiation). And a manufacturing apparatus.

  Thin film transistors generally used in TVs and PC displays are composed of amorphous (non-crystalline) silicon (hereinafter referred to as a-silicon), but silicon is crystallized (hereinafter referred to as p-silicon) by some means. The performance as a TFT can be remarkably improved. At present, excimer laser annealing technology has already been put into practical use as a Si crystallization process at low temperature, and is frequently used for small displays such as smartphones, and further applied to large screen displays. ing.

In this laser annealing method, by irradiating an amorphous semiconductor film with an excimer laser with high pulse energy, the semiconductor that absorbed the light energy becomes molten or semi-molten, and then crystallizes when cooled and solidified. It is. At this time, in order to process a wide area, a pulse laser shaped into a line beam shape is irradiated while scanning in a relatively short axis direction. Usually, scanning with a pulsed laser is performed by moving an installation table on which an amorphous semiconductor film is installed.
In the scanning with the pulse laser, the pulse laser is moved in the scanning direction at a predetermined pitch so that the same position of the amorphous semiconductor film is irradiated with the pulse laser a plurality of times (overlap irradiation). Thereby, a laser annealing process of a semiconductor film having a large size is enabled.

In the laser annealing process using the conventional line beam, the beam width in the scanning direction of the laser pulse is fixed to about 0.35 to 0.4 mm, for example, and the substrate feed amount for each pulse is set to 3% to 8% of the beam width. It is considered that it is necessary to increase the number of times of laser irradiation as much as possible in order to ensure the uniformity of the performance of a plurality of thin film transistors.
For example, in a semiconductor film for LCD (Liquid Crystal Display), the overlap rate is 92 to 95% (12 to 20 times of irradiation, scanning pitch is 32 to 20 μm when the beam width is 0.4 mm), OLED (Organic) In the semiconductor film for light-emitting diodes, the overlap rate is set to 93.8 to 97% (the number of irradiations is 16 to 33 times, and the scanning pitch is 25 to 12 μm when the beam width is 0.4 mm).

  In such a laser annealing process, normally, the intensity distribution of the beam cross section is made flat to achieve uniformity in the process in the minor axis direction and the major axis direction. On the other hand, in Patent Document 1, it is assumed that a poorly crystallized region is generated according to the variation in laser energy, and sufficient crystal or activation is achieved by irradiating the laser with lower energy after sufficient crystallization treatment. There has been proposed a method of recrystallizing or reactivating a portion where the film quality has deteriorated due to the variation in energy intensity while maintaining the portion where the film is formed.

Japanese Patent Laid-Open No. 10-12548

  The variation in laser energy, which is a problem in Patent Document 1, is caused by the variation in the output of the laser light source. The variation in the output of the laser light source has been considerably improved by improving the oscillation circuit, the laser light source itself, and the like, and the problem of crystallization failure due to the variation in the output is gradually becoming smaller. . Moreover, due to the multiple overlaps, the same irradiated surface is irradiated with the pulse laser several times, so that the defective crystallization region caused by the output variation is remelted and crystallized, resulting in a defect. The area can be eliminated.

However, according to the careful observations of the present inventors, even in the present situation, the semiconductor crystallized by the irradiation of the pulsed laser has an irradiation unevenness, and this causes the performance when it is used as a device. I know that.
According to the study by the inventors of the present application, the irradiation unevenness is caused by the formation of the bulge of the polysilicon film at the edge portion (the rear end side in the scanning direction) of the line beam in the scanning direction (usually the short axis direction). it is conceivable that. This portion corresponds to the boundary between the melted portion of the semiconductor film by laser irradiation and the portion that is not irradiated with the laser and remains solid. This rise is considered to increase in proportion to the intensity of irradiation energy. That is, as the irradiation energy increases, melting progresses in the film thickness direction of the semiconductor film, and the temperature of the semiconductor film layer that becomes liquid increases even after the entire film has melted. When this liquid phase part is crystallized as the temperature decreases, the liquid is solidified while being sucked to the solid-liquid interface, that is, the edge of the short axis of the line beam, so that the swell is considered to occur. . In addition, fluctuations in the laser energy, changes in the shape of the short axis of the line beam, disturbances in the position of the semiconductor film that moves relative to the beam, etc. are recognized as irradiation unevenness as disturbances in the height and spacing of the above-mentioned `` protruding part ''. The
Therefore, if the irradiation energy density is lowered and the pulse laser is irradiated, the irradiation unevenness can be reduced. For this purpose, it is necessary to irradiate the laser on the same irradiation surface more times, and the production efficiency is improved. Deteriorate. Further, if the irradiation pulse energy density becomes too low, there arises a problem that the crystal grain size does not become sufficiently large.

  The present invention has been made against the background of the above circumstances, and manufacture of a crystalline semiconductor film that can eliminate unevenness of irradiation on the semiconductor film due to an edge portion in the scanning direction of the pulse laser while suppressing a decrease in productivity as much as possible. An object is to provide a method and a manufacturing apparatus.

That is, in the method for manufacturing a crystalline semiconductor film according to the present invention, the first aspect of the present invention is to crystallize a non-single crystal semiconductor film by overlapping irradiation while relatively scanning a pulse laser in the minor axis direction. In the method for manufacturing a crystalline semiconductor film,
E0 is an irradiation pulse energy density that is lower than an irradiation pulse energy density at which microcrystallization occurs in the non-single-crystal semiconductor film by the irradiation of the pulse laser and suitable for crystallization by a plurality of N times of irradiation.
A first step of irradiating the pulsed laser with the same irradiation pulse energy density E1 as the irradiation pulse energy density E0;
A second step of irradiating the pulse laser with an irradiation pulse energy E2 that is lower than the irradiation pulse energy density E1 and equal to or higher than an irradiation energy density necessary for remelting the crystal;
The total number of irradiations in the first step and the second step with respect to the same irradiation surface is N or more.

  The method for producing a crystalline semiconductor film according to the second aspect of the present invention is the irradiation pulse energy according to the first aspect of the present invention, wherein the irradiation pulse energy suitable for the crystallization is such that the crystal grain size growth is saturated by N times of irradiation a plurality of times. The density E is in the range of E × 0.98 to E × 1.03.

  The method for producing a crystalline semiconductor film according to a third aspect of the present invention is characterized in that, in the first or second aspect of the present invention, the irradiation pulse energy density E2 is E1 × 0.95 or more.

  According to a fourth aspect of the present invention, there is provided the method for producing a crystalline semiconductor film according to any one of the first to third aspects, wherein the total number of irradiations is N × 1.5 or less.

  According to a fifth aspect of the present invention, there is provided a method for manufacturing a crystalline semiconductor film according to any one of the first to fourth aspects of the invention, wherein the pulse laser is scanned by the first step and N1 times for the same irradiation surface. Irradiation is sequentially performed, and then, the predetermined surface is scanned with the pulsed laser in the second step while performing N2 multiple times of irradiation on the same irradiation surface sequentially, and N1 + N2 is set to the total number of irradiations N times. It is characterized by the above.

  The method for manufacturing a crystalline semiconductor film according to a sixth aspect of the present invention is characterized in that, in the fifth aspect of the present invention, the N1 is set to a number equal to or greater than the N2.

  According to a seventh aspect of the present invention, there is provided a method for manufacturing a crystalline semiconductor film according to any one of the first to sixth aspects of the present invention, wherein the pulse laser is applied to the rear end in the scanning direction in the beam cross-sectional intensity distribution in the scanning direction. The rear side has an intensity lower than the intensity on the front side in the scanning direction, the irradiation of the first step is performed according to the intensity on the front side in the scanning direction, and the second step is performed on the rear side in the scanning direction according to the intensity. It is characterized by being irradiated.

  According to an eighth aspect of the present invention, there is provided the method for producing a crystalline semiconductor film according to the seventh aspect, wherein a scanning direction width on the front side in the scanning direction is equal to or larger than a scanning direction width on the rear side in the scanning direction. .

  According to a ninth aspect of the present invention, there is provided the method for producing a crystalline semiconductor film according to any one of the first to eighth aspects, wherein the wavelength of the pulse laser is 400 nm or less.

  The method for producing a crystalline semiconductor film according to a tenth aspect of the present invention is characterized in that in any one of the first to ninth aspects of the present invention, the half width of the pulse laser is 200 ns or less.

  According to an eleventh aspect of the present invention, there is provided the method for producing a crystalline semiconductor film according to any one of the first to tenth aspects of the present invention, wherein the non-single-crystal semiconductor is silicon.

A crystal semiconductor film manufacturing apparatus according to a twelfth aspect of the present invention comprises one or more laser light sources that output a pulse laser;
An optical system for shaping the pulsed laser into a non-single crystal semiconductor;
An energy adjusting unit for adjusting the irradiation energy density of the pulse laser;
A scanning device for scanning the pulse laser relative to the non-single crystal semiconductor;
A control unit for controlling the laser light source, the energy adjustment unit and the scanning device,
The control unit controls the energy adjusting unit to be lower than an irradiation pulse energy density at which microcrystallization occurs in the non-single crystal semiconductor film by pulse laser irradiation, and is suitable for crystallization by N times of irradiation a plurality of times. The irradiation pulse energy density E1 is adjusted to the same irradiation pulse energy density E1, and the scanning device is controlled with the irradiation pulse energy density E1 to scan the pulse laser N1 times (however, N1 <N) a first step of sequentially performing a plurality of irradiations, and a semiconductor irradiated with the pulse laser in the first step by controlling the energy adjusting unit to be lower than the irradiation pulse energy density E1, and a crystal The irradiation pulse energy density E2 is adjusted to an irradiation pulse energy E2 higher than the irradiation energy density necessary for remelting. And performing the second step of sequentially irradiating the non-single crystal semiconductor a plurality of times N2 times (where N2 <N, N1 + N2 ≧ N) while controlling the scanning device and scanning the pulse laser. It is characterized by.

A crystal semiconductor film manufacturing apparatus according to a thirteenth aspect of the present invention comprises one or more laser light sources that output a pulse laser;
An optical system for shaping the pulsed laser into a non-single crystal semiconductor;
In the beam cross-sectional intensity distribution in the scanning direction of the pulse laser, the intensity on the rear side in the scanning direction applied to the rear end in the scanning direction is lower than the intensity on the front side in the scanning direction, and the irradiation pulse energy density due to the intensity on the rear side in the scanning direction is scanned. An intensity adjusting unit that adjusts the intensity distribution to be 0.95 times or more of the irradiation pulse energy density due to the intensity on the front side in the direction;
An energy adjusting unit for adjusting the irradiation energy density of the pulse laser;
A scanning device for scanning the pulse laser relative to the non-single crystal semiconductor;
A control unit for controlling the laser light source, the energy adjustment unit and the scanning device,
The control unit controls the energy adjusting unit to be lower than an irradiation pulse energy density at which microcrystallization occurs in the non-single-crystal semiconductor film in irradiation in the scanning direction front side of the pulse laser, and a plurality of times N times. The irradiation pulse energy density E1 is the same as the irradiation pulse energy density E0 suitable for crystallization by irradiation, and is lower than the irradiation pulse energy density E1 in the irradiation on the rear side in the scanning direction of the pulse laser, and the crystal is remelted. Therefore, adjustment is made so that the irradiation pulse energy E2 is equal to or higher than the required irradiation energy density, and the non-single crystal semiconductor is sequentially irradiated with a plurality of N times or more while controlling the scanning device and scanning the pulse laser. The step of performing is performed.

  According to a fourteenth aspect of the present invention, there is provided the crystal semiconductor film manufacturing apparatus according to the twelfth or thirteenth aspect of the present invention, wherein the control section is configured such that the irradiation pulse energy suitable for the crystallization is irradiated with N times a plurality of times. The irradiation pulse energy density E at which the diameter growth is saturated is set within a range of E × 0.98 to E × 1.03.

  In the present invention, microcrystals are not generated in the first step and the second step as in the case of irradiating the non-single crystal semiconductor film with the pulse laser energy density suitable for crystallization by N irradiations. As described above, the non-single-crystal semiconductor film can be favorably crystallized. Moreover, in the present invention, the height of the raised portion on the semiconductor film by the edge portion of the pulse laser can be reduced. Note that the crystallization may be performed by converting a non-single-crystal crystalline semiconductor film into a single crystal, or converting an amorphous semiconductor film into a polycrystalline semiconductor film. The film may be a single crystal semiconductor film.

  The irradiation pulse energy density is a pulse energy density on the semiconductor film. In the first step, irradiation can be performed with the irradiation pulse energy density being the same as the irradiation energy density suitable for crystallization by N irradiations. Thereby, in the first step, microcrystallization is avoided. The energy density suitable for crystallization in the first step can be appropriately selected within the range intended for crystallization. For example, the irradiation pulse energy density can be set to the same level as the irradiation pulse energy density E at which the crystal grain size growth is saturated by N times of multiple times of irradiation. Specifically, a range of E × 0.98 to E × 1.03 is desirable. If the irradiation pulse energy density in step 1 exceeds E × 1.03, variations due to coarsening of the crystal grain size tend to occur. On the other hand, when it is less than E × 0.98, crystal grain growth becomes insufficient, and variations in crystal grain size tend to occur.

Further, in the second step, the irradiation pulse energy density E1 or less and the irradiation energy density necessary for re-melting the crystal are set to be higher than the irradiation energy density necessary for the first step, so that the raised portion on the semiconductor film due to the edge portion of the pulse laser generated in the first step. In addition, the crystallinity can be lowered and good crystallinity can be maintained. Here, the irradiation pulse energy density E2 in the second step needs to satisfy the above-mentioned conditions, but is more preferably E1 × 0.95 or more. Thereby, the crystal grain size after the pulse laser irradiation in the first step and the second step can be made uniform and the crystal can be sufficiently grown. If the irradiation pulse energy density in the second step is too low, the rise cannot be reduced unless the melting energy density range is reached, and even if the melting energy density range is reached, the rise relaxation effect can be obtained. Sufficient crystal growth cannot be obtained, and the crystal grain size becomes small.
Further, it is desirable that the irradiation pulse energy density E2 is less than E1 × 0.98. If the irradiation pulse energy density E2 is equal to the irradiation pulse energy density E1, an equivalent bulge is formed again on the semiconductor film, and the bulge mitigating action cannot be obtained.

In addition, when the total number of irradiations is N times or more, the crystal grain size can be sufficiently grown. Note that the numerical value of N is not particularly limited, but a certain number of times is desirable in terms of preventing deterioration in film quality due to output variations, for example, eight or more.
Furthermore, the total number of irradiations is desirably N × 1.5 or less. Increasing the total number of irradiations leads to a decrease in productivity. The most desirable total number of irradiations from the viewpoint of productivity is N, but can be selected in consideration of the state of crystallization.
Furthermore, it is desirable that the number of irradiations N1 in the first step is the same as or larger than the number of irradiations N2 in the second step. Thereby, the total number of irradiations can be reduced as much as possible.

In the invention of the present application, the wavelength of the pulse laser is not limited to a specific one, but may be, for example, 400 nm or less.
Furthermore, although the half width of the pulse laser in the present invention is not limited to a specific one, it can be, for example, 200 ns or less.

Further, the pulse laser irradiation in the first step and the second step may be performed by irradiating the non-single crystal semiconductor film with a different pulse laser at different times. The pulse laser irradiation of the second step may be performed. The pulse laser may be synthesized in a pseudo manner by irradiating two or more pulse lasers onto the non-single-crystal semiconductor film at the same time.
That is, in the beam cross-sectional intensity distribution in the scanning direction, the pulse laser has an intensity at the rear side in the scanning direction applied to the rear end in the scanning direction that is lower than the intensity at the front side in the scanning direction. Accordingly, the irradiation of the first step is performed, and the irradiation of the second step is performed according to the intensity on the rear side in the scanning direction.

  As described above, according to the present invention, there is an effect that the crystal can be sufficiently grown by the pulse laser irradiation in the first step and the second step, and a high-quality crystal semiconductor film with little irradiation unevenness can be obtained.

It is a figure which shows the manufacturing apparatus of the crystalline semiconductor film of one Embodiment of this invention. Similarly, it is a figure which shows the beam cross-sectional intensity distribution which has a step in beam intensity by the beam cross-sectional intensity distribution in a scanning direction. Similarly, it is a figure which shows the optical system which shapes the pulse laser which has a step in beam intensity by the beam cross-sectional intensity distribution in the scanning direction. Similarly, it is a figure explaining the synthesis | combination of the pulse laser which has a step in beam intensity by the beam cross-sectional intensity distribution in a scanning direction. Similarly, it is a figure which shows the state of the semiconductor film surface in an Example. Similarly, it is a figure which shows the result of the nonuniformity evaluation in an Example.

Below, the manufacturing apparatus and manufacturing method of the crystalline semiconductor film of one Embodiment of this invention are demonstrated.
The crystal semiconductor film manufacturing apparatus 1 includes a processing chamber 2, and includes a scanning device 3 that can move in the XY direction in the processing chamber 2, and a stage 5 is provided in the scanning device 3. At the time of processing, an amorphous silicon film 100 or the like is installed on the stage 5 as a non-single crystal semiconductor film, and the atmosphere in the processing chamber 2 is adjusted as desired. The silicon film 100 is formed on a substrate (not shown) with a thickness of, for example, 40 to 100 nm. Note that in the present invention, the thickness of the non-single-crystal semiconductor film is not particularly limited. The non-single crystal semiconductor film can be formed by a conventional method, and the method for forming the semiconductor film is not particularly limited in the present invention. Further, the semiconductor film to be processed is preferably an amorphous film, but the present invention is not limited to an amorphous film and includes a non-single crystal film or a crystal in part. Even in these cases, the present apparatus can be applied as a modification of crystals.
The scanning device 3 is driven by a motor (not shown) or the like, and the operation of the motor is controlled by a control unit 8 described later to set the scanning speed of the scanning device 3. The processing chamber 2 is provided with an introduction window 6 for introducing a pulse laser from the outside.

  A pulse laser oscillator 10 is installed outside the processing chamber 2. The pulse laser oscillator 10 is composed of an excimer laser oscillator. The pulse laser oscillator 10 is connected to the control unit 8 in a controllable manner. In response to a command from the control unit 8, the pulse laser oscillator 10 outputs a pulse laser with a predetermined output. In the present invention, the type of oscillation device and the oscillation medium are not limited as long as the semiconductor film can be irradiated with a desired pulse laser.

The pulse laser 15 that is output after being pulsated by the pulse laser oscillation device 10 has, for example, a wavelength of 400 nm or less and a pulse half width of 200 ns or less. However, the present invention is not limited to these.
The pulse energy density of the pulse laser 15 is adjusted by the attenuator 11. The attenuator 11 is connected to the control unit 8 in a controllable manner, and is set to a predetermined attenuation rate according to a command from the control unit 8. In the control unit 8, the attenuation rate is adjusted so that a predetermined irradiation pulse energy density is obtained on the irradiation surface of the semiconductor film. Preferably, the energy density can be adjusted to 100 to 500 mJ / cm ² on the irradiation surface of the silicon film 100.

The pulse laser 15 transmitted through the attenuator 11 is beam-shaped by an optical system 12 including a lens, a reflection mirror, a homogenizer, and the like, and is irradiated to the silicon film 100 in the processing chamber 2 through the introduction window 6 provided in the processing chamber 2. The pulse laser 15 is guided as follows. In the figure, a reflection mirror 12a and a condenser lens 12b are shown as one of the optical systems 12. In the present invention, the type and number of optical members included in the optical system are not particularly limited.
The irradiation surface shape at the time of irradiation is a cross-sectional angle shape, and the square shape includes a line shape.

Next, a method for manufacturing a crystal semiconductor film using the crystal semiconductor film manufacturing apparatus 1 will be described.
For the silicon film 100, an irradiation pulse energy density E0 that is lower than an irradiation pulse energy density at which microcrystallization is generated by irradiation of the pulse laser 15 and is suitable for crystallization by N times of irradiation a plurality of times is determined. As the irradiation pulse energy density E0 suitable for crystallization, one equivalent to the irradiation pulse energy density E at which the crystal grain size growth is saturated by N times of irradiation can be selected. As an equivalent thing, Ex0.98-Ex1.03 can be illustrated. In this embodiment, the same crystallization is obtained as when the pulse laser is irradiated with the irradiation pulse energy density E0 by the overlap irradiation N times.
The irradiation pulse energy density E0 is determined as the irradiation pulse energy density E1 in the first step. Further, the irradiation pulse energy density E2 in the second step is determined to be an irradiation pulse energy density E2 that is lower than the irradiation pulse energy density E1 and is equal to or higher than the irradiation energy density necessary for the crystal to be remelted. Set to. The irradiation pulse energy density E2 is preferably E1 × 0.95 or more.
E0, E1, and E2 described above can be obtained empirically.

  Next, the number of irradiations N1 in the overlap in the first step and the number of irradiations N2 in the overlap in the second step are determined and set in the control unit 8. The sum of N1 and N2 is N or more. N1 ≧ N2 is desirable, and N1 + N2 ≦ 1.5N is desirable. The number of N1 and N2 can be determined empirically.

  Based on the above settings, the pulse laser 15 is output from the pulse laser oscillator 10 while the silicon film 100 is moved in one direction by the scanning device 3 under the conditions of the first step, and the processing chamber is passed through the optical system 12 and the introduction window 6. The silicon film 100 in 2 is processed by overlapping irradiation with the pulse laser 15. Note that the number of overlaps is determined by the scanning speed of the scanning device 3, the repetition frequency of the pulse laser, and the short axis width of the pulse. For this reason, the control unit 8 determines the scanning speed of the scanning device 3 so as to be overlapped N1 times on the assumption of the repetition frequency of the pulse laser. The scanning speed can be selected in the range of 6 to 16 mm / second, for example. In the present invention, the scanning speed is not limited to a specific one, and can be selected in the range of 1 to 100 mm / second, for example. The attenuation rate of the attenuator 11 is adjusted by the control unit 8 so that the irradiation pulse energy E1 on the silicon film 100 becomes a set value. The adjustment can be performed in accordance with this relationship by obtaining a relationship between the attenuation rate and the irradiation pulse energy in advance. Further, the pulse energy density of the pulse laser 15 can be measured by a measuring device (not shown), and the attenuator 11 can be controlled so that the pulse energy density becomes a predetermined value.

  Next, when processing of a predetermined area of the silicon film 100 is completed, the scanning device 3 is operated so as to move in the reverse direction, and the second step of overlap irradiation is performed. The controller 8 determines the scanning speed of the scanning device 3 so that the overlap is performed N2 times on the assumption of the repetition frequency of the pulse laser. The scanning speed can be selected in the range of 6 to 16 mm / second, for example. In the present invention, the scanning speed is not limited to a specific one, and can be selected in the range of 1 to 100 mm / second, for example. The attenuation rate of the attenuator 11 is adjusted by the control unit 8 so that the irradiation pulse energy E2 of the silicon film 100 becomes a set value. The adjustment can be performed in the same manner as in the first step. In addition, the number of times of overlap can be changed by using pulse lasers having different pulse widths in the second step, and a desired number of times of overlap may be obtained by combining the scanning speed and the like.

  The predetermined area of the silicon film 100 that has been subjected to the first-step pulse laser irradiation and the second-step pulse laser irradiation is crystallized as well as the case where N overlap irradiations are performed at the irradiation pulse energy density E0. Is done. Furthermore, in the present embodiment, the irradiation of the first step and the irradiation of the second step are performed, so that the height of the raised portion on the semiconductor film by the edge portion of the pulse laser is reduced, and uneven irradiation is eliminated. It becomes possible to provide a higher quality semiconductor device.

In the above embodiment, the first step scan irradiation is performed in a predetermined area and then the second step scan irradiation is performed in the area. However, the first step is performed using two pulse lasers. The second step of irradiation may be performed immediately after the irradiation at. In this case, the two pulse lasers that are output from the two pulse laser light sources can be used, and the pulse laser output from one pulse laser light source is divided to perform energy adjustment or delay adjustment. Two pulsed lasers may be obtained.
Note that the pulse laser may be a laser whose pulse width is adjusted by combining a plurality of pulse lasers.

In the above embodiment, the silicon film of a predetermined area is processed by one pulse laser in the first step, and then the processing is performed by another pulse laser in the second step. The first step and the second step may be performed at the same time. One pulse includes a pseudo one.
That is, in the beam cross-sectional intensity distribution in the short axis direction, the pulse laser has a lower intensity in the scanning direction applied to the rear end in the scanning direction than the intensity in the scanning direction front side. Irradiation of the first step is performed according to the intensity, and irradiation of the second step is performed according to the intensity on the rear side in the scanning direction.

FIG. 2 shows the beam cross-sectional intensity distribution in the scanning direction of the pulse laser used in this embodiment.
The beam cross section has a stepped beam intensity having a height of the pulse irradiation energy E1 on the front side in the scanning direction and a height of the pulse irradiation energy E2 toward the rear end on the rear side in the scanning direction. In this embodiment, the same region of the silicon film 100 is irradiated N1 times with the pulse portion having the height of the pulse irradiation energy E1, and the same portion of the silicon film 100 is irradiated with the pulse portion having the height of the pulse irradiation energy E2. The region is irradiated N2 times with pulsed laser. The number of times N1 and N2 is determined by the partial length L1 in the scanning direction having the height of the pulse irradiation energy E1, the partial length L2 in the scanning direction having the height of the pulse irradiation energy E1, and the pitch for each pulse. For example, if L1 = L2 (for example, 200 μm), N1 and N2 are basically the same number of times.
That is, the number of times N1 can be increased by relatively increasing the length L1. For this reason, it is desirable that L1 ≧ L2. Therefore, N1 and N2 depend on the sizes of the lengths L1 and L2, and also depend on the scanning speed and the repetition frequency of the pulse laser as in the above embodiment. N1 and N2 in this form are determined by these settings.

The pulse laser having the beam cross-sectional intensity distribution in the scanning direction having the above shape can be provided by various methods.
For example, as shown in FIG. 3A, by disposing a member that blocks or transmits part of the laser beam on the upstream side or downstream side of the optical member on the optical path of the optical system, FIG. As shown in FIG. 5, a pulse laser having a beam cross-sectional intensity distribution in which the beam intensity in the scanning direction is partially reduced and the beam intensity is stepwise can be obtained.
Further, as shown in FIG. 4A, by combining or pseudo-synthesizing two pulses, the beam intensity is stepwise (scanning direction widths L1 and L2) as shown in FIG. 4B. A pulse c having a beam cross-sectional intensity distribution is obtained. For example, a pulse a and a pulse b having different beam intensities can be combined by an optical system with a time difference, and the combined pulse can be irradiated onto a non-single-crystal semiconductor film. Further, a pulse a and a pulse b having different beam intensities can be made to be a single pulse by irradiating the non-single crystal semiconductor film with the positions shifted simultaneously.

Next, using a pulse laser light source (product number LSX540C), an amorphous silicon film having a film thickness of 50 nm is formed with a wavelength of 308 nm, a pulse width of 70 nm, a repetition frequency of 300 Hz, and a major axis length of 465 mm × minor axis length of 400 μm in the beam cross section. An annealing process was performed by irradiating a line beam-shaped excimer pulse laser.
As a conventional example, an irradiation energy density E0 (OED (Optinum energy density); in this example, 370 mJ / cm ² ) suitable for crystallization with an overlap rate of 95% (overlap irradiation 20 times) was set. At this time, the scanning speed and the repetition frequency of the pulse laser were set so that the pitch would be 20 μm. The energy density E0 was set to be the same as the irradiation energy density E at which the crystal grain size is saturated by the overlap irradiation without generating microcrystals.
In addition, as an invention example and a comparative example, the irradiation energy density E1 (370 mJ / cm ² ) that is the same as the irradiation energy density E0 was set in the first step with an overlap rate of 90% (overlap irradiation 10 times). At this time, the scanning speed was set to be 40 μm pitch.

Furthermore, as an example of the invention, an irradiation energy density E2 (352 mJ / cm ² ) that is -5% of the irradiation energy density E1 at an overlap rate of 90% (10 times of overlap irradiation) in the second step was set. At this time, the scanning speed was set to be 40 μm pitch.
Furthermore, as a comparative example, the irradiation energy density was set to −10%, −15%, or −20% of the irradiation energy density E1 at the overlap ratio of 90% (overlap irradiation 10 times) in the second step. Also at this time, the scanning speed and the repetition frequency of the pulse laser were set so that the pitch was 40 μm.

Under the above conditions, the amorphous silicon film was irradiated with a pulse laser in an overlapping manner, and the irradiation unevenness and crystallinity of the crystalline silicon film after the treatment were evaluated. In the conventional example and the invention example, the surface irregularities of the crystalline silicon film were observed with an AFM (Atomic Force Microscope).
FIG. 5 shows a schematic view of the surface cross section of the crystalline silicon film. In the conventional example, as shown in FIG. 5B, a relatively large bulge is formed corresponding to the edge portion by the final irradiation of the pulse laser. On the other hand, in the example of the invention, as shown in FIG. 5 (a), it is recognized that the bulge corresponding to the above is low, and the bulge is mitigated by irradiation of the first step and the second step. I understand.

Irradiation unevenness evaluation of the crystalline silicon film was performed by the following method.
In each example, the inspection light is irradiated to the crystalline silicon film at five points, the reflected light is received to obtain a color image, the color component of the color image is detected, and the color image is detected based on the detected color component. Monochrome. Next, convolution of the monochrome image data is performed to obtain image data in which the image density is emphasized, the image data in which the image density is emphasized is projectively converted, and surface unevenness is corrected based on the image data subjected to the projective conversion. evaluated. Monochrome can be performed using the main color components among the detected color components, and the main color components are color components having a light distribution that is relatively larger than other color components. be able to.
Monochrome image data is indicated by matrix data in which the laser beam direction is a row and the laser scanning direction is a column. In convolution, a matrix of predetermined coefficients is multiplied by a monochrome image data matrix. went.
The matrix of predetermined coefficients obtains image data that emphasizes the image density in the beam direction and image data that emphasizes the image density in the scan direction by using those that emphasize the beam direction and those that emphasize the scan direction, respectively. did.
Specifically, the following convolution was performed. Note that the matrix of the predetermined coefficients is not limited to the following.

For image data in which the density of the image is emphasized, projections in the respective directions are obtained using the fact that streaks gathered in the scan direction and the shot direction appear.
Specifically, projective transformation is performed in the shot direction and the scan direction according to the following expressions.
Shot direction = (Max (Σf (x) / Nx) −Min (Σf (x) / Nx)) / Average Scan direction = (Max (Σf (y) / Ny) −Min (Σf (y) / Ny)) Where x is the position of the image in the shot direction, y is the position of the image in the scan direction, f (x) is the image data at the x position, f (y) is the image data at the y position, and Nx is the image in the shot direction , Ny indicates the number of images in the scanning direction.

The unevenness score in FIG. 6 is a numerical representation of unevenness in the scan direction. The higher the value, the greater the unevenness.
As can be seen from FIG. 6, in the conventional example, the unevenness score is 0.2 to 0.3, and the unevenness is large. As described above, this is considered to be due to the surface bulge caused by the edge of the pulse laser.
On the other hand, in the inventive example, after the first step, the unevenness is large as in the conventional example, but after the second step, the unevenness score is 0.06 to 0.13, and the unevenness is reduced. Note that, in the case where the irradiation in the second step is performed with irradiation pulse energy of −10% E0, −15% E0, and −20% E0, the unevenness is smaller than the conventional example, but the unevenness is reduced. The point was not enough.

Next, the crystallinity of the crystalline silicon films of the conventional example, the invention example, and the reference example was observed with SEM (Scanning Electron Microscope) photographs.
As a result, uniform crystal grains were equally formed in both the conventional example and the invention example. On the other hand, in the reference examples having −15% E0 and −20% E0, sufficient crystal growth was not achieved and the crystal grain size was small. At −10% E0, the crystal grain size was slightly smaller than −15% E0 and −20% E0.

  As described above, according to the example of the present invention, excellent crystal grain growth can be obtained and unevenness can be reduced by reducing the rise due to the edge of the pulse laser. In addition, it is possible to perform processing with almost no reduction in productivity as compared with the conventional case.

  The present invention has been described based on the above-described embodiments and examples. However, the present invention is not limited to these descriptions, and appropriate modifications can be made without departing from the scope of the present invention. It is.

DESCRIPTION OF SYMBOLS 1 Crystal semiconductor film manufacturing apparatus 2 Processing chamber 3 Scanning apparatus 5 Stage 8 Control part 10 Pulse laser oscillation apparatus 11 Attenuator

Claims (14)

In a method for manufacturing a crystalline semiconductor film, on a non-single crystal semiconductor film, crystallization is performed by overlapping irradiation while relatively scanning a pulse laser in the minor axis direction.
E0 is an irradiation pulse energy density that is lower than an irradiation pulse energy density at which microcrystallization occurs in the non-single-crystal semiconductor film by the irradiation of the pulse laser and suitable for crystallization by a plurality of N times of irradiation.
A first step of irradiating the pulsed laser with the same irradiation pulse energy density E1 as the irradiation pulse energy density E0;
A second step of irradiating the pulse laser with an irradiation pulse energy E2 that is lower than the irradiation pulse energy density E1 and equal to or higher than an irradiation energy density necessary for remelting the crystal;
A method of manufacturing a crystalline semiconductor film, wherein the total number of irradiations in the first step and the second step with respect to the same irradiation surface is N or more.   The irradiation pulse energy suitable for the crystallization is within the range of E × 0.98 to E × 1.03 as the irradiation pulse energy density E at which the crystal grain size growth is saturated by N times of multiple times of irradiation. The method for producing a crystalline semiconductor film according to claim 1, wherein:   3. The method of manufacturing a crystalline semiconductor film according to claim 1, wherein the irradiation pulse energy density E2 is E1 × 0.95 or more.   The method for producing a crystalline semiconductor film according to claim 1, wherein the total number of irradiations is N × 1.5 or less.   While the pulse laser is scanned in the first step, N1 multiple times of irradiation are sequentially performed on the same irradiation surface, and then the same irradiation is performed on the predetermined surface while scanning the pulse laser in the second step. 5. The method of manufacturing a crystalline semiconductor film according to claim 1, wherein a plurality of N2 irradiations are sequentially performed on the surface, and the N1 + N2 is set to N times or more as the total number of irradiations.   6. The method of manufacturing a crystalline semiconductor film according to claim 5, wherein N1 is set to a number equal to or greater than N2.   In the beam cross-sectional intensity distribution in the scanning direction, the pulse laser has an intensity on the rear side in the scanning direction applied to the rear end in the scanning direction that is lower than the intensity on the front side in the scanning direction. The crystal semiconductor film manufacturing method according to claim 1, wherein the irradiation of the first step is performed, and the irradiation of the second step is performed according to the intensity on the rear side in the scanning direction. Method.   8. The method of manufacturing a crystalline semiconductor film according to claim 7, wherein a scanning direction width on the front side in the scanning direction is equal to or larger than a scanning direction width on the rear side in the scanning direction.   The method for producing a crystalline semiconductor film according to claim 1, wherein a wavelength of the pulse laser is 400 nm or less.   The method for producing a crystalline semiconductor film according to claim 1, wherein a half width of the pulse laser is 200 ns or less.   The method for manufacturing a crystalline semiconductor film according to claim 1, wherein the non-single-crystal semiconductor is silicon. One or more laser light sources that output a pulsed laser;
An optical system for shaping the pulsed laser into a non-single crystal semiconductor;
An energy adjusting unit for adjusting the irradiation energy density of the pulse laser;
A scanning device for scanning the pulsed laser relative to the single crystal semiconductor;
A control unit for controlling the laser light source, the energy adjustment unit and the scanning device,
The control unit controls the energy adjusting unit to be lower than an irradiation pulse energy density at which microcrystallization occurs in the non-single crystal semiconductor film by pulse laser irradiation, and is suitable for crystallization by N times of irradiation a plurality of times. The irradiation pulse energy density E1 is adjusted to the same irradiation pulse energy density E1, and the scanning device is controlled with the irradiation pulse energy density E1 to scan the pulse laser N1 times (however, N1 <N) a first step of sequentially performing a plurality of irradiations, and a semiconductor irradiated with the pulse laser in the first step by controlling the energy adjusting unit to be lower than the irradiation pulse energy density E1, and a crystal The irradiation pulse energy density E2 is adjusted to an irradiation pulse energy E2 higher than the irradiation energy density necessary for remelting. And performing the second step of sequentially irradiating the non-single crystal semiconductor a plurality of times N2 times (where N2 <N, N1 + N2 ≧ N) while controlling the scanning device and scanning the pulse laser. An apparatus for producing a crystalline semiconductor film characterized by the above. One or more laser light sources that output a pulsed laser;
An optical system for shaping the pulsed laser into a non-single crystal semiconductor;
In the beam cross-sectional intensity distribution in the scanning direction of the pulse laser, the intensity on the rear side in the scanning direction applied to the rear end in the scanning direction is lower than the intensity on the front side in the scanning direction, and the irradiation pulse energy density due to the intensity on the rear side in the scanning direction is scanned. An intensity adjusting unit that adjusts the intensity distribution to be 0.95 times or more of the irradiation pulse energy density due to the intensity on the front side in the direction;
An energy adjusting unit for adjusting the irradiation energy density of the pulse laser;
A scanning device for scanning the pulse laser relative to the non-single crystal semiconductor;
A control unit for controlling the laser light source, the energy adjustment unit and the scanning device,
The control unit controls the energy adjusting unit to be lower than an irradiation pulse energy density at which microcrystallization occurs in the non-single-crystal semiconductor film in irradiation in the scanning direction front side of the pulse laser, and a plurality of times N times. The irradiation pulse energy density E1 is the same as the irradiation pulse energy density E0 suitable for crystallization by irradiation, and is lower than the irradiation pulse energy density E1 in the irradiation on the rear side in the scanning direction of the pulse laser, and the crystal is remelted. Therefore, adjustment is made so that the irradiation pulse energy E2 is equal to or higher than the required irradiation energy density, and the non-single crystal semiconductor is sequentially irradiated with a plurality of N times or more while controlling the scanning device and scanning the pulse laser. An apparatus for manufacturing a crystalline semiconductor film, wherein the step of performing is performed.   The control unit has a range of E × 0.98 to E × 1.03 as an irradiation pulse energy density E at which the irradiation pulse energy suitable for the crystallization is saturated with crystal grain size growth by N times of irradiation a plurality of times. The crystal semiconductor film manufacturing apparatus according to claim 12, wherein the crystal semiconductor film manufacturing apparatus is set within the range.

Images