JP2019145810A - Laser doping apparatus and laser doping method - Google Patents

Abstract

To reduce the electrical properties of semiconductor materials used in power devices such as SiC, diamond, and GaN, and achieves sufficient doping depth.SOLUTION: A laser doping apparatus for performing doping by irradiating a predetermined region of a semiconductor material with a pulsed laser beam includes, in a predetermined area, a solution supply system 46 that supplies a solution containing a dopant, at least one laser device 2 that outputs a pulsed laser beam that passes through the solution containing the dopant, and a pulse time waveform adjusting device that adjusts a pulse time waveform of the pulse laser beam.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a laser doping apparatus and a laser doping method.

  Silicon carbide (SiC) is being developed as a next-generation power device material. SiC has a large band gap, a high dielectric breakdown electric field (approximately 10 times that of Si), excellent thermal conductivity, etc., as compared to silicon (Si), which is conventionally used as a semiconductor material. It is characterized by being stable.

  In order to construct a transistor using SiC, it may be necessary to dope impurities into SiC. In the case of doping impurities into Si, it has been conventionally performed by irradiating Si with an impurity ion beam and activating it at a high temperature. However, when doping impurities into SiC by such a conventional method, thermal damage is applied to SiC, defects are formed, and electrical characteristics may be degraded.

In the following Non-Patent Documents 1 to 5, doping of impurities by irradiating SiC with pulsed laser light in a solution containing a dopant is studied. However, in these non-patent documents 1 to 5, a sufficient doping depth may not be obtained as follows.
(1) Regarding n-type dopants, it has been reported that nitrogen (N) doping depth of 100 to 200 nm can be achieved, but phosphorus (P) doping depth of only about 30 nm can be achieved. .
(2) As for the p-type dopant, an example in which the doping depth of aluminum (Al) has reached about 40 nm has been reported, but no example in which a doping depth higher than that has been achieved has been reported.

Akihiro Ikeda, Koji Nishi, Hiroshi Ikenoue, Tanemasa Asano, Phosphorus doping of 4H SiC by liquid immersion excimer laser irradiation, APPLIED PHYSICS LETTERS 102, 052104 (2013) Koji Nishi, Akihiro Ikeda, Hiroshi Ikenoue, and Tanemasa Asano, Phosphorus doping into 4H-SiC by Irradiation of Excimer Laser in Phosphoric Solution, Japanese Journal of Applied Physics 52 (2013) Daichi Marui, Akihiro Ikeda, Koji Nishi, Hiroshi Ikenoue, Tanemasa Asano, Aluminum doping of 4H-SiC by irradiation of excimer laser in aluminum chloride solution, Japanese Journal of Applied Physics 53 (2014) Akihiro Ikeda, Daichi Marui, Hiroshi Ikenoue, Tanemasa Asano, Nitrogen doping of 4H-SiC by KrF excimer laser irradiation in liquid nitrogen, Japanese Journal of Applied Physics 54 (2015) Yuki Inoue, Hiroshi Ikegami, Akihiro Ikeda, Daisuke Nakamura, Tatsuo Okada, Tanemasa Asano, Diffusion characteristics of 4H-SiC by chemical laser irradiation, 61st JSAP Spring Meeting (2014)

Japanese Patent No. 4387091 Japanese Patent No. 4409231 Special table 2010-525554 International Publication No. 2014/156818

Overview

  A laser doping apparatus according to an aspect of the present disclosure is a laser doping apparatus that performs doping by irradiating a predetermined region of a semiconductor material with a pulsed laser beam; and a solution supply system that supplies a solution containing a dopant to the predetermined region; You may provide the laser system containing the at least 1 laser apparatus which outputs the pulse laser beam which permeate | transmits the solution containing a dopant, and the pulse time waveform adjustment apparatus which adjusts the pulse time waveform of pulse laser light.

  A laser doping apparatus according to another aspect of the present disclosure is a solution supply system that supplies a solution containing boron to a predetermined region in a laser doping apparatus that performs doping by irradiating a predetermined region of a semiconductor material with pulsed laser light. And at least one laser device that outputs pulsed laser light that passes through a solution containing boron.

  A laser doping method according to another aspect of the present disclosure is a laser doping method that performs doping by irradiating a predetermined region of a semiconductor material with a pulsed laser beam, and supplying a solution containing a dopant to the predetermined region; The method may include outputting pulsed laser light that passes through the solution containing the dopant and adjusting a pulse time waveform of the pulsed laser light.

Several embodiments of the present disclosure are described below by way of example only and with reference to the accompanying drawings.
FIG. 1 schematically shows a configuration of a laser doping apparatus according to a comparative example. FIG. 2 schematically illustrates the configuration of the laser doping apparatus according to the first embodiment of the present disclosure. FIG. 3A shows the configuration of the optical pulse stretcher shown in FIG. FIG. 3B is a graph showing a pulse time waveform of pulse laser light when the optical pulse stretcher is not used and when the optical pulse stretcher is used. FIG. 4A is a graph showing the relationship between the concentration of aluminum doped into 4H—SiC and the doping depth. FIG. 4B is a graph showing diode characteristics when a p-type layer is formed by doping aluminum into a part of an n-type 4H—SiC substrate. FIG. 5 schematically illustrates a configuration of a laser doping apparatus according to the second embodiment of the present disclosure. FIG. 6A shows the configuration of the optical pulse stretcher shown in FIG. FIG. 6B shows a state in which the beam splitter is moved to a position different from that in FIG. 6A and the posture of the concave mirror is different from that in FIG. 6A. FIG. 6C shows a state in which the posture of the concave mirror is different from that in FIG. 6B. FIG. 6D is a view of the beam splitter, the holder, the arm, the moving table, and the single-axis stage as seen from the direction perpendicular to the reflecting surface of the beam splitter. FIG. 6E shows a state in which the beam splitter is moved to a position different from that in FIG. 6D. FIG. 7 is a flowchart showing a doping control process by the doping control unit shown in FIG. FIG. 8A is a flowchart showing details of a process of reading the pulse time waveform generation parameter shown in FIG. FIG. 8B is a flowchart showing details of the processing for setting the pulse time waveform generation parameter shown in FIG. FIG. 8C is a flowchart showing details of processing for setting the target pulse energy shown in FIG. FIG. 9 is a flowchart showing a modification of the doping control process by the doping control unit shown in FIG. FIG. 10A is a flowchart showing details of processing for reading the irradiation condition parameters shown in FIG. FIG. 10B is a flowchart showing details of the processing for setting the pulse time waveform generation parameter shown in FIG. FIG. 10C is a flowchart showing details of processing for setting the target pulse energy shown in FIG. FIG. 11 shows an example of the dopant concentration distribution with respect to the depth direction of the semiconductor that can be produced in the modification shown in FIGS. 9 and 10A to 10C. FIG. 12 schematically illustrates a configuration of a laser doping apparatus according to the third embodiment of the present disclosure. FIG. 13 is a flowchart showing a doping control process by the doping control unit shown in FIG. FIG. 14A is a flowchart showing details of processing for reading the irradiation condition parameters shown in FIG. FIG. 14B is a flowchart showing details of a process for controlling the variable slit 42a shown in FIG. FIG. 15A schematically shows a semiconductor device that can be fabricated in the third embodiment. FIG. 15B is a cross-sectional view taken along line XVB-XVB shown in FIG. 15A. FIG. 16A shows a configuration of an optical pulse stretcher used in a laser doping apparatus according to the fourth embodiment of the present disclosure. FIG. 16B is a view of a plurality of beam splitters used in the optical pulse stretcher shown in FIG. 16A as viewed from a direction perpendicular to the reflecting surfaces of these beam splitters. FIG. 17 schematically illustrates a configuration of a laser doping apparatus according to the fifth embodiment of the present disclosure. FIG. 18 shows a timing chart of the trigger signal and pulsed laser light in the laser doping apparatus shown in FIG. FIG. 19 is a flowchart showing a doping control process by the doping control unit shown in FIG. FIG. 20A is a flowchart showing details of the processing for reading the irradiation condition parameters shown in FIG. FIG. 20B is a flowchart showing details of the processing for setting the pulse time waveform generation parameter shown in FIG. FIG. 21 shows the relationship between the concentration of boron doped in 4H—SiC and the doping depth when a solution containing boron is used as the solution containing dopant in the laser doping apparatus according to the sixth embodiment of the present disclosure. It is a graph which shows. FIG. 22 shows a specific configuration of the above laser apparatus. FIG. 23 shows the internal configuration of the laser chamber shown in FIG. 22 and the configuration of the pulse power module. FIG. 24 is a perspective view showing an example of a fly-eye lens 41a included in the beam homogenizer 41 described above. FIG. 25 is a perspective view showing a modification of the fly-eye lens included in the beam homogenizer 41 described above. FIG. 26 is a block diagram illustrating a schematic configuration of the control unit.

Embodiment

<Contents>
1. Outline 2. Laser doping apparatus according to comparative example 2.1 Configuration of laser doping apparatus 2.2 Operation of laser doping apparatus 2.3 Problem 3. Laser doping apparatus including optical pulse stretcher (first embodiment)
3.1 Configuration 3.2 Operation 3.3 Details of Optical Pulse Stretcher 3.4 Operation of First Embodiment 4. Laser doping apparatus capable of varying pulse time waveform (second embodiment)
4.1 Configuration 4.2 Details of Optical Pulse Stretcher 4.3 Processing of Doping Control Unit 4.3.1 Main Flow 4.3.2 Details of S110 4.3.3 Details of S140 4.3.4 S170 4.4 Details of Processing of Doping Control Unit 4.4.1 Main Flow 4.4.2 Details of S110a 4.4.3 Details of S140a 4.4.4 Details of S170a Laser doping apparatus capable of changing shape and size of irradiation region (third embodiment)
5.1 Configuration 5.2 Processing of Doping Control Unit 5.2.1 Main Flow 5.2.2 Details of S110b 5.2.3 Details of S180 Variations of beam splitter (fourth embodiment)
7). Laser doping apparatus including a plurality of laser units (fifth embodiment)
7.1 Configuration and Operation 7.2 Processing of Doping Control Unit 7.2.1 Main Flow 7.2.2 Details of S110c 7.2.3 Details of S140c 7.3 Action 8. Laser doping apparatus using a solution containing boron (sixth embodiment)
9. Others 9.1 Details of laser device 9.2 Configuration of fly-eye lens 9.3 Configuration of control unit

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Embodiment described below shows some examples of this indication, and does not limit the contents of this indication. In addition, all the configurations and operations described in the embodiments are not necessarily essential as the configurations and operations of the present disclosure. In addition, the same referential mark is attached | subjected to the same component and the overlapping description is abbreviate | omitted.

1. SUMMARY The present disclosure relates to a laser doping apparatus or a laser doping method for doping a semiconductor material by irradiating the semiconductor material with a pulsed laser beam in an ultraviolet region in a solution containing a dopant.

2. 2. Laser doping apparatus according to comparative example 2.1 Configuration of laser doping apparatus FIG. 1 schematically shows a configuration of a laser doping apparatus according to a comparative example. The laser doping apparatus may include a laser system 3 and a doping apparatus 4.

  The laser system 3 may include a laser device 2 and an attenuator 18. The laser device 2 may be an excimer laser device that outputs pulsed laser light in the ultraviolet region. The wavelength of the pulsed laser beam is preferably a wavelength that transmits the solution containing the dopant used in the doping apparatus 4 with a high transmittance, and is a wavelength that causes little damage to the semiconductor material that is an object to be irradiated. For example, the laser device 2 may be a laser device using KrF or XeCl as a laser medium. The pulse width of the output pulsed laser light may be about 50 ns. In the case of a KrF excimer laser device, the wavelength of the pulsed laser light may be about 248.4 nm. In the case of a XeCl excimer laser device, the wavelength of the pulsed laser light may be about 308 nm.

  The attenuator 18 is disposed in the optical path of the pulsed laser light output from the laser device 2, and may include two partial reflection mirrors 18a and 18b and rotation stages 18c and 18d of these partial reflection mirrors. . The two partial reflection mirrors 18a and 18b may be optical elements whose transmittance varies depending on the incident angle of the pulse laser beam.

  The doping apparatus 4 may include a slit 42, a high reflection mirror 43a, a transfer optical system 43d, a table 43f, an XYZ stage 43g, a container 43h, a solution supply system 46, and a monitor device 44. Good. The slit 42 may be disposed in the optical path of the pulse laser beam that has passed through the attenuator 18. The slit 42 may be a slit having two axes substantially orthogonal to each other. The slit 42 may be arranged so that a region having a uniform light intensity distribution in the beam cross section of the pulsed laser light passes through.

  The high reflection mirror 43a may be a dichroic mirror that reflects the pulsed laser light in the ultraviolet region output from the laser device 2 with high reflectivity and transmits visible light. The high reflection mirror 43a may be arranged so as to reflect the pulse laser beam that has passed through the slit 42 and to enter the transfer optical system 43d. The transfer optical system 43d may be an optical system including one or a plurality of convex lenses, or may be an optical system including one or a plurality of convex lenses and one or a plurality of concave lenses. The transfer optical system 43d may be a lens that corrects chromatic aberration with respect to the wavelengths of visible light and ultraviolet light. For example, the transfer optical system 43d may include a plurality of lenses made of synthetic quartz and calcium fluoride materials.

  The table 43f may support the container 43h. The container 43h may be configured so that a solution containing the dopant can be stored therein. This solution may be, for example, an aluminum chloride aqueous solution containing aluminum as a dopant, an ammonia aqueous solution containing nitrogen as a dopant, a phosphoric acid aqueous solution containing phosphorus as a dopant, or a solution containing other dopants.

  The irradiated object 43e may be a semiconductor material used for a power device such as SiC, diamond, GaN, or the like. Although the crystal structure of SiC is not particularly limited, for example, the irradiation object 43e may be 4H—SiC. 4H-SiC may be SiC having a hexagonal crystal structure in which one layer is composed of four layers. The irradiated object 43e may be accommodated in the bottom of the container 43h so as to be immersed in the solution stored in the container 43h. The surface of the irradiation region of the pulse laser beam on the irradiation object 43e may be substantially parallel to the liquid level of the solution stored in the container 43h. At least the region irradiated with the pulse laser beam of the irradiation object 43e may be located below the liquid level of the solution stored in the container 43h.

The solution supply system 46 may include a pump 46a, a solution supply pipe 46b, a plate 46c, a window 46d, and a solution discharge pipe 46e. The output of the pump 46a may be connected to a solution supply pipe 46b fixed to the plate 46c. The solution supply pipe 46b may be fixed to the plate 46c in an inclined state with respect to the liquid surface so that the solution flows along the region irradiated with the pulse laser beam of the irradiation object 43e. In the solution supply pipe 46b, the outlet of the solution supply pipe 46b may be directed to a region irradiated with the pulse laser beam of the irradiation object 43e. A solution discharge pipe 46e for discharging a part of the solution may be further fixed to the plate 46c. The solution discharged through the solution discharge pipe 46e may be purified as necessary and then stored in a tank (not shown). This tank may be connected to the input of the pump 46a.
The XYZ stage 43g may support the table 43f. The XYZ stage 43g may be capable of adjusting the position of the irradiation object 43e accommodated in the container 43h by adjusting the position of the table 43f.

  The window 46d may be fixed to the plate 46c and disposed in the optical path of pulsed laser light that irradiates the irradiated object 43e. The material of the window 46d may be synthetic quartz that transmits excimer laser light. The lower surface of the window 46d may be in contact with the solution. The upper surface of the window 46d may be located above the liquid level of the solution. Alternatively, the plate 46c may surround the window 46d, and the upper surface of the plate 46c may be positioned above the liquid level of the solution, so that the solution does not flow into the upper surface of the window 46d.

  The monitor device 44 may include a beam splitter 44a, an illumination device 44b, and a two-dimensional sensor 44c. The beam splitter 44a may be a half mirror that transmits about 50% of visible light and reflects about 50%. The illumination device 44b may be a lamp that emits visible light.

  The transfer optical system 43d may be configured such that a transfer image of the slit 42 by light in the ultraviolet region is formed at a first predetermined position via the window 46d and a solution containing a dopant. When the position of the surface of the irradiated object 43e substantially coincides with the first predetermined position, the transfer optical system 43d causes the transfer image of the surface of the irradiated object 43e by visible light to pass through the high reflection mirror 43a and the beam splitter 44a. The image may be formed at the second predetermined position. The two-dimensional sensor 44c may be arranged so that the position of the light receiving surface of the two-dimensional sensor 44c substantially coincides with the second predetermined position.

2.2 Operation of Laser Doping Apparatus The two partial reflection mirrors 18a and 18b included in the attenuator 18 are configured so that the incident angles of the pulse laser light are substantially equal to each other, and the transmittance of the pulse laser light is a desired transmittance. The posture may be controlled by the rotary stages 18c and 18d. Thereby, the pulsed laser light output from the laser device 2 can be attenuated to a desired pulse energy and pass through the attenuator 18.

The pulsed laser light that has passed through the attenuator 18 may pass through two orthogonal axes 42 and enter the transfer optical system 43d via the high reflection mirror 43a.
On the other hand, at least a part of the visible light output from the illumination device 44b is reflected by the beam splitter 44a, passes through the high reflection mirror 43a, and passes through the solution including the transfer optical system 43d, the window 46d, and the dopant. The surface of the irradiated object 43e may be illuminated.

  Even if the XYZ stage 43g adjusts the position of the table 43f so that the transfer optical system 43d forms a transfer image of the surface of the irradiated object 43e with visible light on the position of the light receiving surface of the two-dimensional sensor 44c. Good. When such adjustment is made, the transfer optical system 43d can form a transfer image of the slit 42 by light in the ultraviolet region on the surface of the irradiation object 43e. That is, the pulse laser beam can pass through the window 46d and the solution containing the dopant, and can be irradiated on the surface of the irradiation object 43e. As a result, in the region where the image of the slit 42 is transferred, the dopant can diffuse in the depth direction from the surface of the irradiated object 43e.

As described above, the lower surface of the window 46d is in contact with the solution, and the upper surface of the window 46d may not be in contact with the solution. Thereby, it can be suppressed that the liquid surface is shaken by the solution flow generated by the solution supply system 46 and the transfer image by the transfer optical system 43d is distorted or the transfer position is changed.
The flow rate of the pump 46a may be controlled so that a solution flow is formed inside the container 43h. Even when bubbles are generated in the solution by the energy of the pulse laser beam, the bubbles can be removed from the irradiation region of the pulse laser beam by the flow of the solution. Thereby, it can suppress that the imaging performance of the transfer optical system 43d falls by a bubble.

2.3 Problem When a power device is configured using SiC, the impurity doping depth is preferably 100 nm or more. However, it can be difficult to diffuse the p-type dopant to SiC to a depth of 100 nm or more.

  In the embodiment described below, in order to solve this problem, a pulse time waveform adjusting device such as an optical pulse stretcher may be arranged in the optical path of the pulse laser beam output from the laser device. For example, a pulse laser beam having a long pulse time width may be generated by the pulse time waveform adjusting device and irradiated on the surface of the irradiation object 43e in the solution.

3. Laser doping apparatus including optical pulse stretcher (first embodiment)
3.1 Configuration FIG. 2 schematically illustrates the configuration of the laser doping apparatus according to the first embodiment of the present disclosure. In the laser doping apparatus according to the first embodiment, the laser system 3a includes an optical pulse stretcher 16, a pulse time waveform measuring unit 19, and a laser system in addition to the configuration of the laser system described with reference to FIG. And a control unit 31. In addition, in the laser doping apparatus according to the first embodiment, the doping apparatus 4a may include a doping control unit 45 in addition to the configuration of the doping apparatus described with reference to FIG.

  The optical pulse stretcher 16 may be disposed in the optical path of the pulsed laser light between the laser device 2 and the attenuator 18. The optical pulse stretcher 16 may include a beam splitter and a delay optical system. The optical pulse stretcher 16 may correspond to the pulse time waveform adjustment device in the present disclosure.

  The pulse time waveform measurement unit 19 may be disposed in the optical path of the pulse laser beam between the attenuator 18 and the doping apparatus 4a. The pulse time waveform measurement unit 19 may include a beam splitter 19a, a condensing optical system 19b, and an optical sensor 19c. The beam splitter 19a may transmit the pulse laser beam that has passed through the attenuator 18 with high transmittance, and may reflect a part of the pulse laser beam toward the condensing optical system 19b. The condensing optical system 19b may condense the light reflected by the beam splitter 19a on the photosensitive surface of the optical sensor 19c. The optical sensor 19c may be a high-speed photodiode or a biplanar tube.

3.2 Operation The doping control unit 45 may receive the image data from the two-dimensional sensor 44c of the monitor device 44, and may control the XYZ stage 43g so that the contrast of the image data is increased. When the XYZ stage 43g is controlled so that the contrast of the image data is maximized, the image of the surface of the irradiation object 43e may be transferred to the light receiving surface of the two-dimensional sensor 44c by the transfer optical system 43d. Thus, when the XYZ stage 43g is controlled, the image of the slit 42 can be transferred onto the surface of the irradiation object 43e by the transfer optical system 43d.
The doping control unit 45 transmits data of the target pulse energy Et of the pulse laser light that has passed through the attenuator 18 to the laser system control unit 31 so that the fluence of the pulse laser light in the irradiation object 43e becomes a predetermined value. Also good.

The laser system control unit 31 may transmit the target pulse energy EL1 of the pulse laser beam output from the laser device 2 to the laser device 2. Next, the laser system control unit 31 transmits a signal for controlling the transmittance T2 of the attenuator 18 so that the target pulse energy Et of the pulse laser beam that has passed through the attenuator 18 becomes a value obtained by the following expression. Also good.
Et = T1, T2, EL1
Here, T1 may be the transmittance of the optical pulse stretcher 16.

The doping controller 45 may drive the pump 46a so that the solution flows between the irradiation region of the pulsed laser light on the irradiation object 43e and the window 46d.
The doping control unit 45 may transmit a light emission trigger signal to the laser device 2 via the laser system control unit 31. When a light emission trigger signal is input to the laser device 2, pulse laser light having pulse energy near the target pulse energy EL <b> 1 can be output from the laser device 2. The output pulsed laser light enters the optical pulse stretcher 16 and can be pulse stretched.

  The pulse-stretched pulse laser beam may be attenuated by the attenuator 18 so as to have a pulse energy near the target pulse energy Et. Thereafter, the pulsed laser light is partially reflected by the beam splitter 19a of the pulse time waveform measuring unit 19 and can enter the optical sensor 19c via the condensing optical system 19b.

  The laser system control unit 31 may receive a signal from the optical sensor 19c and measure the pulse time waveform of the pulsed laser light. Alternatively, the pulse time waveform may be integrated to calculate the pulse energy to confirm whether the pulse energy is near the target pulse energy Et. Further, the measured pulse time waveform data may be transmitted to the doping control unit 45.

  The pulsed laser beam that has passed through the pulse time waveform measuring unit 19 can enter the slit 42 of the doping apparatus 4a. The pulse laser beam that has passed through the slit 42 may be reflected by the high reflection mirror 43a and may enter the irradiation object 43e via the transfer optical system 43d, the window 46d, and the solution. Thereby, the dopant in the solution can be doped in the irradiation region of the irradiation object 43e.

3.3 Details of Optical Pulse Stretcher FIG. 3A shows the configuration of the optical pulse stretcher shown in FIG. The optical pulse stretcher 16 may include a beam splitter 16y and concave mirrors 16a to 16h.

The beam splitter 16y may include a substrate that transmits the pulsed laser light with high transmittance. The first surface 161 of the substrate may be coated with a reduced reflection film, and the second surface 162 of the substrate may be coated with a partial reflection film. The beam splitter 16y may be supported by the holder 16o.
The concave mirrors 16a to 16h can constitute a delay optical system. Each of the concave mirrors 16a to 16h may be a concave mirror having substantially the same focal length F. The focal length F may correspond to, for example, the distance from the beam splitter 16y to the concave mirror 16a.

  The pulsed laser light incident on the beam splitter 16y from the left side in the figure can pass through the first surface 161 with high transmittance and can enter the partial reflection film on the second surface 162. The pulsed laser light incident on the second surface 162 can be branched into a first optical path and a second optical path. That is, a part of the pulsed laser light incident on the beam splitter 16y from the left side in the drawing is transmitted and proceeds to the first optical path to become the first output pulse P1. The other part of the pulsed laser light incident on the beam splitter 16y from the left side in the drawing is reflected, proceeds to the second optical path, and can be reflected by the concave mirror 16a.

  The pulsed laser light reflected by the concave mirror 16a may be reflected in the order of the concave mirrors 16d, 16e, 16h, 16g, 16f, 16c, and 16b and may enter the beam splitter 16y from the upper side in the drawing. A part of the pulsed laser light incident on the beam splitter 16y from the upper side in the drawing is reflected and can travel to the first optical path to become the second output pulse P2. Another part of the pulsed laser light incident on the beam splitter 16y from the upper side in the drawing can pass through the beam splitter 16y and travel again to the second optical path.

  The first output pulse P1 incident on and transmitted through the beam splitter 16y from the left side in the figure and the second output pulse P2 incident on and reflected from the beam splitter 16y from the upper side in the figure are substantially the same optical path axis. Thus, it can be output from the optical pulse stretcher 16 toward the right side in the figure. The optical path length of the delayed optical path via the concave mirrors 16a to 16h can correspond to 16 times the focal length F of each of the concave mirrors 16a to 16h. In this case, the delay time of the second output pulse P2 with respect to the first output pulse P1 can be 16 F / c, where c is the speed of light. Further, when the image of the beam cross section of the pulse laser beam on the second surface 162 of the beam splitter 16y is incident on the second surface 162 again through the delay optical path, it is rotated forward on the second surface to form an image. Can do.

  The pulse laser beam that has entered the beam splitter 16y from the upper side in the drawing and is transmitted is reflected again by the concave mirror 16a, passes through the same delay optical path as described above, and again enters the beam splitter 16y from the upper side in the drawing. Good. A part of the pulse laser beam incident on the beam splitter 16y again from the upper side in the figure can be reflected and output from the optical pulse stretcher 16 toward the right side in the figure. By repeating this, third and fourth output pulses (not shown) may be output on the optical path axes substantially the same as the first and second output pulses P1 and P2, and the pulse laser beam may be pulse stretched.

  Although FIG. 3A shows an example in which eight concave mirrors are used, the present disclosure is not limited to this example, and a larger number of concave mirrors may be similarly arranged. Alternatively, fewer than eight concave mirrors, for example, four concave mirrors may be arranged.

FIG. 3B is a graph showing a pulse time waveform of pulse laser light when the optical pulse stretcher is not used and when the optical pulse stretcher is used. The optical path length of the delay optical path of the optical pulse stretcher was 7 m, and the reflectance of the beam splitter 16y was 62%. When the optical pulse stretcher was not used, the pulse time width ΔT _TIS of the pulse laser beam was about 50 ns. When the optical pulse stretcher was used, the pulse time width ΔT _TIS of the pulse laser beam was about 80 ns. Here, the pulse time width ΔT _TIS of the pulse laser beam may be calculated by the following equation.
ΔT _TIS = [∫I (t) dt] ² / ∫I (t) ² dt

3.4 Operation of the First Embodiment As described above, the irradiation of the semiconductor material irradiation object 43e with the pulse-stretched pulsed laser light in the solution containing the dopant is performed as compared with the case where the pulse stretching is not performed. The depth can be increased.

FIG. 4A is a graph showing the relationship between the concentration of aluminum doped into 4H—SiC and the doping depth. As the solution containing the dopant, a saturated aluminum chloride aqueous solution was used. As the pulse laser beam, KrF excimer laser beam was used, the fluence per pulse was 4.5 J / cm ² , the repetition frequency was 100 Hz, and the number of irradiation shots at one place was 10 pulses. The pulse time waveform and the pulse time width are as described with reference to FIG. 3B both when the optical pulse stretcher is not used and when the optical pulse stretcher is used.

The concentration of aluminum doped in 4H—SiC was measured by secondary ion mass spectrometry (SIMS).
As shown in FIG. 4A, the doping time of aluminum was improved from 40 nm to 120 nm by extending the pulse time width of the pulse laser beam from 50 ns to 80 ns using an optical pulse stretcher.
Although FIG. 4A illustrates the case where 4H—SiC is doped with aluminum, the present disclosure is not limited thereto. Even in the case of doping to diamond or GaN, it can be expected that the doping depth is increased by extending the pulse time width of the pulse laser beam irradiated in the aluminum chloride aqueous solution.

  FIG. 4B is a graph showing diode characteristics when a p-type layer is formed by doping aluminum into a part of a 4H—SiC n-type substrate. The horizontal axis represents a value obtained by subtracting the voltage applied to the n-type substrate from the voltage applied to the p-type layer. The vertical axis represents current. Since the value on the horizontal axis is 0 or more, FIG. 4B shows the characteristics of the forward bias.

  As shown in FIG. 4B, when doping was performed without using the optical pulse stretcher, the ON voltage, which is the voltage at which the forward current starts to flow, was about 1V. On the other hand, when doping was performed using an optical pulse stretcher, the on-voltage was about 2V. In general, when a pn junction is formed using SiC, it is known that the ON voltage is 2V to 3V. Therefore, the result shown in FIG. 4B can prove that a pn junction is formed by using an optical pulse stretcher to form a p-type layer and can be used as a semiconductor device.

4). Laser doping apparatus capable of varying pulse time waveform (second embodiment)
4.1 Configuration FIG. 5 schematically illustrates a configuration of a laser doping apparatus according to the second embodiment of the present disclosure. In the laser doping apparatus according to the second embodiment, the laser system 3b may include an optical pulse stretcher 16α instead of the optical pulse stretcher 16 described with reference to FIG. In the laser doping apparatus according to the second embodiment, the doping apparatus 4b may include a beam homogenizer 41 in addition to the configuration of the doping apparatus described with reference to FIG.

  The beam homogenizer 41 may be disposed in the optical path of the pulse laser beam between the pulse time waveform measuring unit 19 and the slit 42. The beam homogenizer 41 may include a fly-eye lens 41a and a condenser optical system 41b. The condenser optical system 41 b may be arranged so that the position of the rear focal point substantially coincides with the position of the slit 42. The fly-eye lens 41a may be arranged such that the position of the focal plane including the front focal point of the plurality of lenses included in the fly-eye lens 41a substantially coincides with the position of the front focal plane of the condenser optical system 41b.

  The pulse laser beam incident on the doping device 4 b can Koehler illuminate the slit 42 by the beam homogenizer 41. As a result, the light intensity distribution of the pulse laser beam can be made uniform.

4.2 Details of Optical Pulse Stretcher FIG. 6A shows the configuration of the optical pulse stretcher shown in FIG. The optical pulse stretcher 16α may include a beam splitter 16n instead of the beam splitter 16y described with reference to FIG. 3A. Of the concave mirrors 16a to 16h, the concave mirrors 16c, 16d, 16e, and 16f may be supported by the rotary stages 16i, 16j, 16k, and 16m, respectively.

  The first surface 161 of the beam splitter 16n may be coated with a reduced reflection film, and the second surface 162 may be coated with a partial reflection film having a reflectance distribution in the arrow B direction. The beam splitter 16n may be supported by the arm 16p via the holder 16o. The arm 16p may be supported by the moving table 16q, and the moving table 16q may be supported by the uniaxial stage 16r.

  6D and 6E are views of the beam splitter 16n, the holder 16o, the arm 16p, the moving table 16q, and the uniaxial stage 16r viewed from a direction perpendicular to the reflecting surface of the beam splitter 16n. 6B, 6C, and 6E show a state in which the beam splitter 16n and the like are moved to positions different from those in FIGS. 6A and 6D. The uniaxial stage 16r may be configured to reciprocate the beam splitter 16n, the holder 16o, the arm 16p, and the moving table 16q in the arrow B direction. The single axis stage 16r may be controlled by the laser system control unit 31 (FIG. 5). Thereby, the beam splitter 16n may be configured to be able to reciprocate in the direction of the arrow B while maintaining the incident angle of the pulse laser beam.

  Referring to FIG. 6A again, the rotary stages 16i, 16j, 16k, and 16m may be configured to control the respective postures by rotating the concave mirrors 16c, 16d, 16e, and 16f in the plane of the paper. . The rotary stages 16i, 16j, 16k, and 16m may be controlled by the laser system control unit 31 (FIG. 5).

  When the concave mirrors 16c, 16d, 16e, and 16f are in the state shown in FIG. 6A, the optical path of the pulse laser light when the pulse laser light is incident on the optical pulse stretcher 16α has been described with reference to FIG. 3A. It may be the same as that.

  FIG. 6B shows a state in which the postures of the concave mirrors 16c, 16d, 16e, and 16f are different from those in FIG. 6A. When the postures of the concave mirrors 16c, 16d, 16e, and 16f are in the state shown in FIG. 6B, the pulse laser light reflected by the concave mirror 16a is reflected in the order of the concave mirrors 16d, 16e, 16f, 16c, and 16b. Also good. That is, the concave mirrors 16h and 16g may be skipped. The optical path length of the delay optical path in this case can correspond to about 12 times the focal length F of each of the concave mirrors 16a to 16h.

  FIG. 6C shows a state in which the postures of the concave mirrors 16c, 16d, 16e, and 16f are different from those in FIGS. 6A and 6B. When the postures of the concave mirrors 16c, 16d, 16e, and 16f are in the state shown in FIG. 6C, the pulsed laser light reflected by the concave mirror 16a may be reflected in the order of the concave mirrors 16d, 16c, and 16b. That is, the concave mirrors 16e, 16h, 16g, and 16f may be skipped. In this case, the optical path length of the delay optical path may correspond to about 8 times the focal length F of each of the concave mirrors 16a to 16h.

  Thus, the optical path length of the delay optical path can be varied to 8F, 12F, and 16F depending on the posture of the concave mirrors 16c, 16d, 16e, and 16f. In any of these cases, a transfer image of the beam cross section of the pulsed laser light incident on the second surface 162 of the beam splitter 16n can be formed on the second surface 162 of the beam splitter 16n. By changing the optical path length of the delay optical path, the delay time of the second output pulse P2 relative to the first output pulse P1 and the third and fourth output pulses described above can be changed. The time waveform of the pulse laser beam to be applied can be changed.

  When the uniaxial stage 16r reciprocates the position of the beam splitter 16n in the direction of arrow B, the reflectance of the pulsed laser light at the beam splitter 16n can be changed. The intensity ratio of the second output pulse P2 and the third and fourth output pulses to the first output pulse P1 can be changed by changing the reflectance of the pulsed laser light in the beam splitter 16n, so that the optical pulse stretcher The pulse time waveform of the pulse laser beam output from 16α can be changed.

As described above, by changing the reflectance of the beam splitter included in the optical pulse stretcher 16α and the optical path length of the delay optical path, the pulse time intervals of the first to fourth output pulses, and the first to fourth output pulses are changed. The light intensity ratio of the output pulses can be changed.
Other points may be the same as those of the laser doping apparatus described with reference to FIGS. 2 and 3A.

4.3 Processing of Doping Control Unit 4.3.1 Main Flow FIG. 7 is a flowchart showing processing of doping control by the doping control unit shown in FIG. The doping control unit 45 may perform doping using pulsed laser light having a desired pulse time waveform by the following processing.

  First, in S100, the doping control unit 45 may determine whether or not the pulse time waveform generation parameter data has been received. The pulse time waveform generation parameter data may be received by an operator, for example, or may be received from a computer system (not shown) through a network. The pulse time waveform generation parameter is a parameter necessary for generating the pulse time waveform. In this case, the target value of the reflectance of the beam splitter 16n and the target of the optical path length of the delay optical path of the optical pulse stretcher 16α. And a value.

  When the pulse time waveform generation parameter data is received, the doping control unit 45 may advance the process to S110. When the pulse time waveform generation parameter data is not received, the doping control unit 45 may wait until the pulse time waveform generation parameter data is received.

  When the pulse time waveform generation parameter data is received (S100; YES), in S110, the doping control unit 45 may read the received pulse time waveform generation parameter. Details of this processing will be described later with reference to FIG. 8A.

  Next, in S120, the doping control unit 45 may control the pump 46a (FIG. 5) so as to start supplying a solution containing the dopant to the surface of the irradiation object.

Next, in S130, the doping control unit 45 may control the XYZ stage 43g with reference to the image of the two-dimensional sensor 44c (FIG. 5) so as to be positioned in a desired irradiation region.
Next, in S140, the doping control unit 45 may set the laser system 3b to the received pulse time waveform generation parameter. That is, the doping control unit 45 may transmit the target value of the optical path length of the delay optical path of the optical pulse stretcher 16α and the target value of the reflectance of the beam splitter 16n to the laser system control unit 31. Details of this processing will be described later with reference to FIG. 8B.

  Next, in S150, the doping control unit 45 may determine whether or not the data of the fluence target value F and the shot number S have been received. The data of the fluence target value F and the shot number S may be received by an operator, for example, or may be received from a computer system (not shown) through a network.

  When the data of the fluence target value F and the shot number S are received, the doping control unit 45 may advance the process to S160. When the data of the fluence target value F and the shot number S are not received, the doping control unit 45 may wait until the data of the fluence target value F and the shot number S are received.

  When the data of the fluence target value F and the shot number S are received (S150; YES), the doping control unit 45 may read the received data of the fluence target value F and the shot number S in S160.

  Next, in S <b> 170, the doping control unit 45 may set the target pulse energy so that the fluence approaches the target value F. The doping control unit 45 may transmit the target pulse energy data to the laser system control unit 31. Details of this processing will be described later with reference to FIG. 8C.

  Next, in S <b> 190, the doping control unit 45 may output S light emission trigger signals to the laser system control unit 31. Thereby, pulsed laser light including S pulses may be generated from the laser system 3b. These pulsed laser beams may be applied to the irradiated object 43e.

  Next, in S200, the doping control unit 45 may determine whether the data of the pulse time waveform generation parameter has been changed. When the data of the pulse time waveform generation parameter is changed (S200; YES), the doping control unit 45 may return the process to S100 described above and receive the data of the pulse time waveform generation parameter again.

  When the data of the pulse time waveform generation parameter is not changed (S200; NO), the doping control unit 45 may advance the process to S210. In S210, the doping control unit 45 may determine whether or not to stop the laser irradiation. When laser irradiation is not stopped (S210; NO), the doping control unit 45 may return the process to the above-described S130 to control the XYZ stage 43g, output a light emission trigger signal, or the like. When the laser irradiation is stopped (S210; YES), the doping control unit 45 may end the process of this flowchart.

4.3.2 Details of S110 FIG. 8A is a flowchart showing details of a process for reading the pulse time waveform generation parameters shown in FIG. The process shown in FIG. 8A may be performed by the doping control unit 45 as a subroutine of S110 shown in FIG.

In S112, the doping control unit 45 may read the target value R of the reflectance of the beam splitter 16n and the target value L of the optical path length of the delay optical path.
After S112, the doping control unit 45 may end the processing of this flowchart and return to the main flow.

4.3.3 Details of S140 FIG. 8B is a flowchart showing details of the processing for setting the pulse time waveform generation parameters shown in FIG. The process shown in FIG. 8B may be performed by the doping control unit 45 as a subroutine of S140 shown in FIG.

  First, in S141, the doping control unit 45 may transmit the target value R of the reflectance of the beam splitter 16n to the laser system control unit 31. Accordingly, the laser system control unit 31 may control the uniaxial stage 16r that moves the beam splitter 16n so that the reflectance of the beam splitter 16n approaches the target value.

Next, in S <b> 142, the doping control unit 45 may transmit the target value L of the optical path length of the delay optical path to the laser system control unit 31. Thereby, the laser system control unit 31 rotates the concave mirrors 16c, 16d, 16e, and 16f of the optical pulse stretcher 16α so that the optical path length of the delay optical path of the optical pulse stretcher 16α approaches the target value. 16i, 16j, 16k, and 16m may be controlled.
After S142, the doping control unit 45 may end the process of this flowchart and return to the main flow.

4.3.4 Details of S170 FIG. 8C is a flowchart showing details of processing for setting the target pulse energy shown in FIG. The process shown in FIG. 8C may be performed by the doping control unit 45 as a subroutine of S170 shown in FIG.

First, in S171, the doping control unit 45 may calculate the target pulse energy Et based on the received target value F of the fluence. The target pulse energy Et may be calculated as follows.
Et = F · A / Tt
Here, A may be the area of the image of the slit 42 formed on the irradiation object 43e. Tt may be the transmittance in the optical path of the pulse laser beam output from the laser system 3b via the pulse time waveform measuring unit 19 until the irradiated object 43e is irradiated.

Next, in S <b> 172, the doping control unit 45 may transmit the target pulse energy Et to the laser system control unit 31. Thereby, the laser system control unit 31 may calculate the target pulse energy EL1 of the pulse laser beam to be output by the laser device 2, and may control the laser device 2 based on the calculation result. Further, the laser system control unit 31 may calculate a target value of the transmittance T2 of the attenuator 18 based on the target pulse energy Et. This target value may be calculated so that the following expression holds for the transmittance T2 of the attenuator 18.
T2 = Et / (T1 · EL1)
Here, T1 may be the transmittance of the optical pulse stretcher 16α. The laser system control unit 31 may control the attenuator 18 based on the calculation result of the target value of the transmittance T2 of the attenuator 18. Thereby, the pulse energy of the pulse laser beam output from the laser system 3b can approach the target pulse energy Et.

  After S172, the doping control unit 45 may end the process of this flowchart and return to the main flow.

4.4 Modification Example of Processing of Doping Control Unit 4.4.1 Main Flow FIG. 9 is a flowchart showing a modification example of processing of doping control by the doping control unit shown in FIG. The doping control unit 45 may perform doping under a plurality of irradiation conditions by the following process.

The doping control unit 45 may receive and read a plurality of combinations of irradiation condition parameters in S100a and S110a. The doping control unit 45 may receive and read irradiation condition parameters of Nmax combinations. The irradiation condition parameter may include a fluence target value and the number of shots in addition to the above-described pulse time waveform generation parameter.
Details of the processing of S110a will be described later with reference to FIG. 10A, but the other points may be the same as S100 and S110 described with reference to FIG. The next processing of S120 and S130 may be the same as that described with reference to FIG.

Next, in S135, the doping control unit 45 may set the value of the number N to 1.
Next, in S140a, the doping control unit 45 may set the laser system 3b as the Nth pulse time waveform generation parameter. That is, the doping control unit 45, the N-th target value L _N of the optical path length of the delay optical path of the optical pulse stretcher 16Arufa, the N-th reflectivity of the beam splitter 16n and the target value R _N, the laser system control unit You may transmit to 31. Details of this processing will be described later with reference to FIG. 10B.

Next, in S170a, the doping control unit 45 may set the target pulse energy so that the fluence approaches the _Nth target value FN. The doping control unit 45 may transmit the target pulse energy data to the laser system control unit 31. Details of this processing will be described later with reference to FIG. 10C.
Next, in S <b> 190 a, the doping control unit 45 may output _SN light emission trigger signals to the laser system control unit 31. As a result, pulsed laser light including S _N pulses may be generated from the laser system 3b. These pulsed laser beams may be irradiated on the surface of the irradiation object 43e.

Next, in S195, the doping control unit 45 may determine whether or not the value of the number N is greater than or equal to Nmax.
When the value of the number N is not equal to or greater than Nmax (S195; NO), the doping control unit 45 may update the value of the number N by adding 1 to the value of the number N in S196. After S196, the doping control unit 45 may return the process to S140a described above.
When the value of the number N is equal to or greater than Nmax (S195; YES), the doping control unit 45 outputs the light emission trigger signal for all irradiation condition parameters from the number N = 1 to the number N = Nmax. May be advanced to S200a.

Next, in S200a, the doping control unit 45 may determine whether or not a plurality of types of irradiation condition parameter data has been changed. When the data of a plurality of irradiation condition parameters is changed (S200a; YES), the doping control unit 45 may return the process to the above-described S100a and receive the data of the plurality of irradiation condition parameters again.
When the data of a plurality of irradiation condition parameters are not changed (S200a; NO), the doping control unit 45 may advance the process to S210.
S210 and the subsequent processing may be the same as those described with reference to FIG.

4.4.2 Details of S110a FIG. 10A is a flowchart showing details of processing for reading the irradiation condition parameters shown in FIG. The processing shown in FIG. 10A may be performed by the doping control unit 45 as a subroutine of S110a shown in FIG.

First, in S111a, the doping control unit 45 may set the value of the number N to 1.
Next, at S112a, the doping control unit 45 reads the N-th target value R _N of the reflectivity of the beam splitter 16n, the N-th optical path length of the delay optical path of the optical pulse stretcher 16α the target value L _N But you can.
Next, at S113a, the doping control unit 45, the N-th target value _{F N} fluence, and N-th shot number _{S N,} may be read to.

Next, in S115a, the doping control unit 45 may determine whether or not the value of the number N is greater than or equal to Nmax.
When the value of the number N is not equal to or greater than Nmax (S115a; NO), the doping control unit 45 may update the value of the number N by adding 1 to the value of the number N in S116a. After S116a, the doping control unit 45 may return the process to S112a described above.
When the value of the number N is greater than or equal to Nmax (S115a; YES), the doping control unit 45 has received all irradiation condition parameters from the number N = 1 to the number N = Nmax. May be terminated to return to the main flow.
Not limited to the process shown in FIG. 10A, the doping control unit 45 may read Nmax irradiation condition parameters at once as table data.

4.4.3 Details of S140a FIG. 10B is a flowchart showing details of the processing for setting the pulse time waveform generation parameters shown in FIG. The process shown in FIG. 10B may be performed by the doping control unit 45 as a subroutine of S140a shown in FIG.

First, in S141a, the doping control unit 45 may transmit the _Nth target value RN of the reflectance of the beam splitter 16n to the laser system control unit 31. Accordingly, the laser system control unit 31 may control the uniaxial stage 16r that moves the beam splitter 16n so that the reflectance of the beam splitter 16n approaches the _Nth target value RN.

Next, in S142a, the doping control unit 45 may transmit the _Nth target value LN of the optical path length of the delay optical path to the laser system control unit 31. Thereby, the laser system control unit 31 moves the concave mirrors 16c, 16d, 16e, and 16f of the optical pulse stretcher 16α so that the optical path length of the delay optical path of the optical pulse stretcher 16α approaches the _Nth target value _LN. The rotary stages 16i, 16j, 16k, and 16m that are rotated may be controlled.
After S142a, the doping control unit 45 may end the process of this flowchart and return to the main flow.

4.4.4 Details of S170a FIG. 10C is a flowchart showing details of processing for setting the target pulse energy shown in FIG. The process shown in FIG. 10C may be performed by the doping control unit 45 as a subroutine of S170a shown in FIG.

First, in S171a, the doping control unit 45 may calculate the Nth target pulse energy Et based on the received Nth target value F _N of the fluence. The calculation of the Nth target pulse energy Et may be the same as that described with reference to FIG. 8C.

  Next, in S <b> 172 a, the doping control unit 45 may transmit the Nth target pulse energy Et to the laser system control unit 31. The operation of the laser system control unit 31 that has received the Nth target pulse energy Et may be the same as that described with reference to FIG. 8C.

  After S172a, the doping control unit 45 may end the processing of this flowchart and return to the main flow.

  FIG. 11 shows an example of the dopant concentration distribution with respect to the depth direction of the semiconductor that can be produced in the modification shown in FIGS. 9 and 10A to 10C. In this modification, semiconductors having different dopant concentration distributions in the depth direction can be manufactured by irradiating the same irradiation region with different fluences and shot numbers with different pulse waveforms. For example, the irradiation condition parameter of number N = 1 may be a condition that the doping depth is shallow and the dopant concentration is high. Conversely, the irradiation condition parameter of number N = 3 may be a condition that the doping depth is deep and the dopant concentration is low. The irradiation condition parameter with the number N = 2 may be intermediate between the irradiation condition parameters with the doping depth and the dopant concentration of the number N = 1 and the number N = 3, respectively. The doping depth may be mainly controlled by the pulse time width. The dopant concentration may be mainly controlled by the fluence and the number of shots.

5. Laser doping apparatus capable of changing shape and size of irradiation region (third embodiment)
5.1 Configuration FIG. 12 schematically illustrates a configuration of a laser doping apparatus according to the third embodiment of the present disclosure. In the laser doping apparatus according to the third embodiment, the doping apparatus 4c may include a variable slit 42a instead of the slit 42 described with reference to FIG. The laser system 3b and other configurations may be the same as those described with reference to FIG.

  The variable slit 42a is a slit having two axes that are substantially orthogonal to each other, and may be configured such that the slit width of the two axes can be changed. The slit width may be controlled by a control signal output from the doping control unit 45. The range of uniform illumination by the beam homogenizer 41 is preferably larger than the area defined by the maximum width of the two axes of the variable slit 42a.

5.2 Processing of Doping Control Unit 5.2.1 Main Flow FIG. 13 is a flowchart showing processing of doping control by the doping control unit shown in FIG. The process shown in FIG. 13 includes the process described with reference to FIG. 9 in that it includes not only the pulse time waveform generation parameter, the fluence, and the number of shots as the irradiation condition parameters, but also the slit width of the variable slit 42a. May be different.

  The doping control unit 45 may read a plurality of combinations of irradiation condition parameters according to S110b instead of S110a described with reference to FIG. Details of this process will be described later with reference to FIG. 14A. In S110b, the irradiation condition parameter may include a target value of the slit width of the variable slit 42a. The slit width of the variable slit 42a may be a biaxial slit width substantially perpendicular to each other.

Further, the doping control unit 45 controls the variable slit 42a so that the slit width of the variable slit 42a approaches the _Nth target value DN between S170a and S190a described with reference to FIG. (S180). Details of this processing will be described later with reference to FIG. 14B.
Other processes may be the same as those described with reference to FIG.

5.2.2 Details of S110b FIG. 14A is a flowchart showing details of processing for reading the irradiation condition parameters shown in FIG. The process shown in FIG. 14A may be performed by the doping control unit 45 as a subroutine of S110b shown in FIG.

First, the processing from S111a to S113a may be the same as that described with reference to FIG. 10A.
Next, in S114b, the doping control unit 45 may read the _Nth target value DN of the slit width of the variable slit 42a.
Subsequent processing may be the same as that described with reference to FIG. 10A.

5.2.3 Details of S180 FIG. 14B is a flowchart showing details of processing for controlling the variable slit 42a shown in FIG. The process shown in FIG. 14B may be performed by the doping control unit 45 as a subroutine of S180 shown in FIG.
In S181, the doping control unit 45 may control the variable slit 42a so that the slit width of the variable slit 42a approaches the _Nth target value DN.
After S181, the doping control unit 45 may end the processing of this flowchart and return to the main flow.

  FIG. 15A schematically shows a semiconductor device that can be fabricated in the third embodiment. FIG. 15B is a cross-sectional view taken along line XVB-XVB shown in FIG. 15A. In these drawings, illustration of various contact electrodes, insulating films, wirings, and the like is omitted. The irradiated object 43e shown in these drawings may be obtained by doping a part of a 4H—SiC n-type substrate with aluminum to form a plurality of p-type layers 431 and 432. The p-type layer 431 may be a p-type layer having a relatively low concentration, a deep doping depth, and a narrow doping region. The p-type layer 432 may be a p-type layer having a relatively high concentration, a shallow doping depth, and a wide doping region.

  As described above, according to the third embodiment, the pulse concentration waveform generation parameter, the target value of fluence, the number of shots, and the target value of the slit width are controlled separately, so that the dopant concentration, the doping depth are controlled. And the doping region can be controlled separately.

  In the third embodiment, the doping region is varied by controlling the variable slit 42a, but the present disclosure is not limited to this. Instead of the variable slit 42a, a mask on which a desired pattern is formed may be arranged so that the mask can be exchanged. Then, a semiconductor element having a desired concentration distribution in both the depth direction and the surface direction of the irradiated object can be manufactured by exchanging the mask and controlling the irradiation condition parameters.

6). Variations of beam splitter (fourth embodiment)
FIG. 16A shows a configuration of an optical pulse stretcher used in a laser doping apparatus according to the fourth embodiment of the present disclosure. FIG. 16B is a view of a plurality of beam splitters used in the optical pulse stretcher shown in FIG. 16A as viewed from a direction perpendicular to the reflecting surfaces of these beam splitters.

  The optical pulse stretcher 16z used in the fourth embodiment may include a plurality of beam splitters 16s, 16t, 16u, and 16v. The plurality of beam splitters 16s, 16t, 16u, and 16v may have different reflectances. The plurality of beam splitters 16s, 16t, 16u, and 16v may be supported by a holder 16w, and the holder 16w may be rotatably supported by a step motor 16x.

The laser system control unit 31 (FIG. 2) may selectively arrange the beam splitters 16s, 16t, 16u, and 16v in the optical path of the pulsed laser light by controlling the step motor 16x. Even when any of the beam splitters 16s, 16t, 16u, and 16v is located in the optical path of the pulse laser beam, the incident angle of the pulse laser beam may be constant and only the reflectance may be different from each other. Thereby, the time waveform of the pulse laser beam output from the optical pulse stretcher 16z can be changed.
About another point, it may be the same as that of 1st Embodiment. In the second or third embodiment, the optical pulse stretcher 16z shown in FIGS. 16A and 16B may be used.

7). Laser doping apparatus including a plurality of laser units (fifth embodiment)
7.1 Configuration and Operation FIG. 17 schematically illustrates a configuration of a laser doping apparatus according to the fifth embodiment of the present disclosure. In the laser doping apparatus according to the fifth embodiment, the laser system 3c includes first, second, and third laser units 2a, 2b, and 2c, a delay circuit 5, high reflection mirrors 6a and 6b, and a knife edge. Mirrors 6c and 6d may be provided. In the laser doping apparatus according to the fifth embodiment, the laser system 3c may not include the optical pulse stretcher.
About another point, it may be the same as that of the structure of the 1st-3rd embodiment.

  Each of the first, second, and third laser units 2a, 2b, and 2c may have the same configuration as the laser device 2 described above. Each laser unit may receive target pulse energy data from the laser system control unit 31. The target pulse energy data may be different between the first, second, and third laser units 2a, 2b, and 2c. In each laser unit, a charging voltage of a charging capacitor (described later) may be set based on the received target pulse energy data.

  The delay circuit 5 may receive delay time setting data from the laser system control unit 31. The delay circuit 5 may receive the light emission trigger signal output from the doping control unit 45 via the laser system control unit 31. The delay circuit 5 applies the first, second, and third laser units 2a, 2b, and 2c to the first, second, and third laser units 2a, 2c in this order at the timing when the set delay time has elapsed since the light emission trigger signal was received. You may output the 1st, 2nd, 3rd trigger signal.

  The high reflection mirror 6a and the knife edge mirror 6c may change the optical path by reflecting the pulse laser beam output from the first laser unit 2a with a high reflectance. The pulse laser beam output from the first laser unit 2a and whose optical path has been changed may be output toward the attenuator 18 substantially in parallel with and close to the pulse laser beam output from the second laser unit 2b. Good.

  The high reflection mirror 6b and the knife edge mirror 6d may change the optical path by reflecting the pulse laser beam output from the third laser unit 2c with a high reflectance. The pulse laser beam whose optical path is changed by being output from the third laser unit 2c may be output toward the attenuator 18 substantially in parallel with and close to the pulse laser beam output from the second laser unit 2b. Good.

  The pulse laser beams output from the first, second, and third laser units 2a, 2b, and 2c may enter the beam homogenizer 41 via the attenuator 18 and the pulse time waveform measurement unit 19. When the slit 42 is Koehler-illuminated by the beam homogenizer 41, the optical paths of these pulsed laser beams overlap at the slit 42, and the light intensity profile of the beam at the opening of the slit 42 can be made uniform.

  FIG. 18 shows a timing chart of the trigger signal and pulsed laser light in the laser doping apparatus shown in FIG. In the fifth embodiment, pulse laser beams having a desired pulse time waveform are irradiated by superimposing pulse laser beams output from the first, second, and third laser units 2a, 2b, and 2c. An object may be irradiated.

The first trigger signal output from the delay circuit 5 to the first laser unit 2a may have a delay time Tr1 with respect to the light emission trigger signal output from the laser system control unit 31 to the delay circuit 5. .
The second trigger signal output from the delay circuit 5 to the second laser unit 2b may have a delay time Tr2 with respect to the light emission trigger signal output from the laser system control unit 31 to the delay circuit 5. .
The third trigger signal output from the delay circuit 5 to the third laser unit 2c may have a delay time Tr3 with respect to the light emission trigger signal output from the laser system control unit 31 to the delay circuit 5. .

  Upon receiving the first trigger signal, the first laser unit 2a may output a first pulse that is a pulsed laser beam. The reception timing of the first trigger signal and the rising timing of the first pulse may substantially coincide.

  Upon receiving the second trigger signal, the second laser unit 2b may output a second pulse that is a pulsed laser beam. The reception timing of the second trigger signal and the rising timing of the second pulse may substantially coincide. Therefore, the pulse time interval Td2 of the second pulse with respect to the first pulse can substantially correspond to the difference between the delay time Tr1 of the first trigger signal and the delay time Tr2 of the second trigger signal.

  Upon receiving the third trigger signal, the third laser unit 2c may output a third pulse that is a pulsed laser beam. The reception timing of the third trigger signal and the rising timing of the third pulse may substantially coincide. Therefore, the pulse time interval Td3 of the third pulse with respect to the first pulse can substantially correspond to the difference between the delay time Tr1 of the first trigger signal and the delay time Tr3 of the third trigger signal.

  The first to third pulses respectively output from the first to third laser units 2a to 2c may have different pulse time waveforms. In particular, the first to third laser units 2a to 2c may be set with the charging voltage of the charging capacitor in accordance with the set target pulse energy. For example, the peak value of the light intensity I2 of the second pulse output from the second laser part 2b is less than 1 with respect to the peak value of the light intensity I1 of the first pulse output from the first laser part 2a. It may be set to have a light intensity ratio Er2. Further, the peak value of the light intensity I3 of the third pulse output from the third laser part 2c is the peak value of the light intensity I1 of the first pulse output from the first laser part 2a. It may be set to have a smaller light intensity ratio Er3.

  These first to third pulses may be brought close to each other by the high reflection mirrors 6 a and 6 b and the knife edge mirrors 6 c and 6 d and further superposed by the beam homogenizer 41. Thereby, the irradiation object 43e may be irradiated with pulsed laser light having an extended pulse time width by superimposing the waveforms of the first to third pulses having different delay times. The delay circuit 5 may correspond to the pulse time waveform adjustment device in the present disclosure.

7.2 Processing of Doping Control Unit 7.2.1 Main Flow FIG. 19 is a flowchart showing processing of doping control by the doping control unit shown in FIG. The doping control unit 45 may perform doping with a pulsed laser beam having a desired pulse time waveform by the following processing.

The doping control unit 45 may receive and read the pulse time waveform generation parameter in S100c and S110c. Here, the pulse time waveform generation parameter includes the target value of the pulse time interval of the pulse laser light output from the first, second, and third laser units 2a, 2b, and 2c, and the first, second, and third parameters. And a target value of the light intensity ratio of the pulse laser beam output from the laser units 2a, 2b, and 2c.
Details of the processing of S110c will be described later with reference to FIG. 20A, but the other points may be the same as S100 and S110 described with reference to FIG. The next processing of S120 and S130 may be the same as that described with reference to FIG.

Next, in S140c, the doping control unit 45 may set the laser system 3c to the read pulse time waveform generation parameter. That is, the doping control unit 45 includes the target value of the pulse time interval of the pulse laser light output from the first, second, and third laser units 2a, 2b, and 2c, and the first, second, and third lasers. The target value of the light intensity ratio of the pulsed laser light output from the units 2a, 2b, and 2c may be transmitted to the laser system control unit 31. Details of this processing will be described later with reference to FIG. 20B.
Subsequent processing may be the same as that described with reference to FIG.

7.2.2 Details of S110c FIG. 20A is a flowchart showing details of processing for reading the irradiation condition parameters shown in FIG. The process shown in FIG. 20A may be performed by the doping control unit 45 as a subroutine of S110c shown in FIG.

First, in S111c, the doping control unit 45 may read the target value of the light intensity ratio Er2 of the second pulse output from the second laser unit 2b with respect to the first pulse output from the first laser unit 2a. .
Next, in S112c, the doping control unit 45 reads the target value of the light intensity ratio Er3 of the third pulse output from the third laser unit 2c with respect to the first pulse output from the first laser unit 2a. Good.

Next, in S113c, the doping control unit 45 reads the target value of the pulse time interval Td2 of the second pulse output from the second laser unit 2b with respect to the first pulse output from the first laser unit 2a. Good.
Next, in S114c, the doping control unit 45 reads the target value of the pulse time interval Td3 of the third pulse output from the third laser unit 2c with respect to the first pulse output from the first laser unit 2a. Good.
After S114c, the doping control unit 45 may end the process of this flowchart and return to the main flow.

7.2.3 Details of S140c FIG. 20B is a flowchart showing details of the processing for setting the pulse time waveform generation parameters shown in FIG. The process shown in FIG. 20B may be performed by the doping control unit 45 as a subroutine of S140c shown in FIG.

  First, in S141c, the doping control unit 45 may transmit the target pulse energy EL1 of the first laser unit 2a to the laser system control unit 31. Accordingly, the laser system control unit 31 may control the first laser unit 2a so that the pulse energy of the first pulse approaches the target pulse energy EL1.

Next, in S142c, the doping control unit 45 may transmit the target pulse energy EL2 of the second laser unit 2b to the laser system control unit 31. The target pulse energy EL2 of the second laser unit 2b may be calculated as follows.
EL2 = EL1 × Er2
Accordingly, the laser system control unit 31 may control the second laser unit 2b so that the pulse energy of the second pulse approaches the target pulse energy EL2.

Next, in S143c, the doping control unit 45 may transmit the target pulse energy EL3 of the third laser unit 2c to the laser system control unit 31. The target pulse energy EL3 of the third laser unit 2c may be calculated as follows.
EL3 = EL1 × Er3
Thereby, the laser system control unit 31 may control the third laser unit 2c so that the pulse energy of the third pulse approaches the target pulse energy EL3.

  In each laser unit, the charging voltage of each charging capacitor may be set so that the pulse energy of the pulse laser beam output from each laser unit approaches each target pulse energy. As a result of setting the charging voltage in this way, the light intensity ratio of the pulsed laser light output from each laser unit may approach the target value of the light intensity ratio. If the pulse energy of the pulsed laser beam cannot be brought close to the target pulse energy within the set range of the charging voltage, it is brought close to the target pulse energy by controlling the pressure of the laser gas in the laser chamber. Also good.

  Next, in S <b> 144 c, the doping control unit 45 may transmit the target value of the delay time Tr <b> 1 of the first pulse output from the first laser unit 2 a to the laser system control unit 31. Thereby, the laser system control unit 31 may control the delay circuit 5 so that the delay time Tr1 of the first pulse becomes the set target value.

Next, in S145c, the doping control unit 45 may transmit the target value of the delay time Tr2 of the second pulse output from the second laser unit 2b to the laser system control unit 31. The target value of the delay time Tr2 of the second pulse may be calculated as follows.
Tr2 = Tr1 + Td2
Thereby, the laser system control unit 31 may control the delay circuit 5 so that the delay time Tr2 of the second pulse becomes the set target value.

Next, in S146c, the doping control unit 45 may transmit the target value of the delay time Tr3 of the third pulse output from the third laser unit 2c to the laser system control unit 31. The target value of the delay time Tr3 of the third pulse may be calculated as follows.
Tr3 = Tr1 + Td3
Thereby, the laser system control unit 31 may control the delay circuit 5 so that the delay time Tr3 of the third pulse becomes the set target value.
After S146c, the doping control unit 45 may end the process of this flowchart and return to the main flow.

7.3 Operation As described above, in the fifth embodiment, the output timing of the pulse laser beam from the plurality of laser units can be set by the delay circuit 5. Further, the light intensity ratio of the pulsed laser light by the plurality of laser units can be set by the charging voltage of the charging capacitor of each laser unit.

  In the fifth embodiment, the target pulse energy for the first to third laser units 2a to 2c is set in order to control the light intensity ratio of the first to third pulses. In addition to this, the attenuator 18 may be separately controlled in order to control the fluence of the pulse laser beam irradiated to the irradiation object.

  According to the fifth embodiment, it is possible to individually set the output timing and the light intensity ratio of the pulse laser light from the plurality of laser units. Therefore, the degree of freedom of the time waveform of the pulse laser beam obtained by superimposing these pulse laser beams can be improved as compared with the first to fourth embodiments.

8). Laser doping apparatus using a solution containing boron (sixth embodiment)
FIG. 21 shows the relationship between the concentration of boron doped in 4H—SiC and the doping depth when a solution containing boron is used as the solution containing dopant in the laser doping apparatus according to the sixth embodiment of the present disclosure. It is a graph which shows. Although illustration of the laser doping apparatus according to the sixth embodiment is omitted, an apparatus similar to the laser doping apparatus described with reference to FIG. 1 may be used except that a solution containing boron is used. In other words, in the sixth embodiment, pulse stretching of the pulse laser beam may not be performed.

A saturated concentration boric acid aqueous solution was used as the solution containing the dopant. As the pulse laser beam, KrF excimer laser beam was used, the fluence per pulse was 4.5 J / cm ² , and the number of irradiation shots at one place was one pulse. The pulse time width ΔT _TIS was 50 ns.

  In doping impurities by irradiating SiC with laser light in a solution containing a p-type dopant, aluminum was used as the p-type dopant, but a doping depth of 40 nm or more could not be achieved. According to the sixth embodiment, by using boron as the p-type dopant, it has been found that doping can be performed to a depth of about 400 nm without pulse stretching.

  Although FIG. 21 illustrates the case where 4H—SiC is doped with boron, the present disclosure is not limited thereto. Even in the case of doping to diamond or GaN, it is expected that the doping depth can be increased by irradiating a pulse laser beam in a solution containing boron without extending the pulse time width of the pulse laser beam. .

9. Others 9.1 Details of Laser Device FIG. 22 shows a specific configuration of the laser device described above. The laser apparatus 2 shown in FIG. 22 may include a laser chamber 10, a pair of electrodes 11a and 11b, a charger 12, and a pulse power module (PPM) 13. FIG. 22 shows the internal configuration of the laser chamber 10 viewed from a direction substantially perpendicular to the traveling direction of the laser light.

  The laser device 2 may further include a cross flow fan 21 and a motor 22. The laser device 2 may further include a high reflection mirror 14, an output coupling mirror 15, a pulse energy measurement unit 17, a laser control unit 30, and a laser gas supply / exhaust device 23.

  The laser chamber 10 may be a chamber in which the above-described laser medium is enclosed. The pressure sensor 24 may be connected to the laser chamber 10 via a pipe so as to measure the pressure of the laser gas in the laser chamber 10. The pair of electrodes 11a and 11b can be arranged in the laser chamber 10 as electrodes for exciting the laser medium by discharge. An opening may be formed in the laser chamber 10, and the opening may be closed by the electrical insulating unit 20. The electrode 11 a may be supported by the electrical insulating unit 20, and the electrode 11 b may be supported by the internal partition plate 10 c of the laser chamber 10. The electrically insulating portion 20 may be embedded with a conductive portion 20a. The conductive part 20a may electrically connect the high voltage terminal of the pulse power module 13 and the electrode 11a so that the high voltage supplied from the pulse power module 13 is applied to the electrode 11a. The laser chamber 10 may be connected to the laser gas supply / exhaust device 23 by gas piping.

  The rotational axis of the cross flow fan 21 may be connected to a motor 22 disposed outside the laser chamber 10. The laser gas may circulate inside the laser chamber 10 by the motor 22 rotating the cross flow fan 21.

  The power supply device may include a charger 12 and a pulse power module 13. The pulse power module 13 may include a charging capacitor and a switch 13a. The output of the charger 12 is connected to a charging capacitor, and the charger 12 can hold electric energy for applying a high voltage between the pair of electrodes 11a and 11b. When the switch 13a controlled by the laser controller 30 is turned from OFF to ON, the pulse power module 13 generates a pulsed high voltage from the electric energy held in the charging capacitor, and this high voltage is used as the pair of electrodes 11a. And 11b may be applied.

  When a high voltage is applied between the pair of electrodes 11a and 11b, a discharge may occur between the pair of electrodes 11a and 11b. Due to the energy of this discharge, the laser medium in the laser chamber 10 can be excited to shift to a high energy level. When the excited laser medium subsequently moves to a low energy level, light having a wavelength corresponding to the energy level difference can be emitted.

  Windows 10 a and 10 b may be provided at both ends of the laser chamber 10. The light generated in the laser chamber 10 can be emitted to the outside of the laser chamber 10 through the windows 10a and 10b.

The high reflection mirror 14 may reflect the light emitted from the window 10 a of the laser chamber 10 with a high reflectance and return it to the laser chamber 10.
The surface of the output coupling mirror 15 may be coated with a partial reflection film. Therefore, the output coupling mirror 15 may transmit a part of the light output from the window 10 b of the laser chamber 10 and output it, and reflect the other part and return it to the laser chamber 10.

  The high reflection mirror 14 and the output coupling mirror 15 can constitute an optical resonator. The light emitted from the laser chamber 10 reciprocates between the high reflection mirror 14 and the output coupling mirror 15 and can be amplified every time it passes through the laser gain space between the electrode 11a and the electrode 11b. A part of the amplified light can be output as pulsed laser light via the output coupling mirror 15.

  The pulse energy measurement unit 17 may include a beam splitter 17a, a condensing optical system 17b, and an optical sensor 17c. The beam splitter 17a may transmit the pulsed laser light transmitted through the output coupling mirror 15 with high transmittance, and may reflect a part of the pulsed laser light toward the condensing optical system 17b. The condensing optical system 17b may condense the light reflected by the beam splitter 17a on the photosensitive surface of the optical sensor 17c. The optical sensor 17 c may detect the pulse energy of the laser light focused on the photosensitive surface and output the pulse energy detection data to the laser controller 30.

  For example, the laser control unit 30 may transmit a charging voltage setting signal to the charger 12 or may transmit a light emission trigger signal for switching ON or OFF to the pulse power module 13. Further, the laser control unit 30 may control the laser gas supply / exhaust device 23 based on the detection value of the pressure sensor 24 in order to control the pressure of the laser gas in the laser chamber 10.

  The laser control unit 30 may receive pulse energy detection data from the pulse energy measurement unit 17 and refer to the pulse energy detection data to determine the charging voltage of the charger 12 and the pressure of the laser gas in the laser chamber 10. You may control. The pulse energy of the pulse laser beam may be controlled by controlling the charging voltage of the charger 12 and the pressure of the laser gas. The laser control unit 30 may count the number of oscillation pulses of the excimer laser device based on the data received from the pulse energy measurement unit 17.

  FIG. 23 shows the internal configuration of the laser chamber shown in FIG. 22 and the configuration of the pulse power module. FIG. 23 shows the internal configuration of the laser chamber 10 viewed from a direction substantially parallel to the traveling direction of the laser light. The conductive member including the internal partition plate 10c of the laser chamber 10 may be connected to the ground potential. The electrode 11b may be connected to the ground potential via the internal partition plate 10c.

  In addition to the pair of electrodes 11 a and 11 b and the cross flow fan 21, a heat exchanger 26 may be disposed inside the laser chamber 10. As the cross flow fan 21 rotates, the laser gas may circulate inside the laser chamber 10 as indicated by an arrow A. The heat exchanger 26 may discharge the thermal energy of the laser gas that has become a high temperature due to the discharge to the outside of the laser chamber 10.

  The pulse power module 13 may include a charging capacitor C0, a switch 13a, a step-up transformer TC1, a plurality of magnetic switches Sr1 to Sr3, and a plurality of capacitors C1, C2, and C3.

  Any of the magnetic switches Sr1 to Sr3 may include a saturable reactor. Each of the magnetic switches Sr1 to Sr3 may have a low impedance when the time integration value of the voltage applied to both ends thereof reaches a predetermined value determined by the characteristics of each magnetic switch.

A charging voltage may be set in the charger 12 by the laser control unit 30. The charger 12 may charge the charging capacitor C0 based on the set charging voltage.
A light emission trigger signal may be input to the switch 13 a of the pulse power module 13 by the laser control unit 30. When the light emission trigger signal is input to the switch 13a, the switch 13a may be turned on. When the switch 13a is turned on, a current can flow from the charging capacitor C0 to the primary side of the step-up transformer TC1.

  When a current flows on the primary side of the step-up transformer TC1, a reverse current can flow on the secondary side of the step-up transformer TC1 due to electromagnetic induction. When a current flows through the secondary side of the step-up transformer TC1, the time integral value of the voltage applied to the magnetic switch Sr1 may eventually reach the threshold value.

When the time integral value of the voltage applied to the magnetic switch Sr1 reaches a threshold value, the magnetic switch Sr1 becomes magnetically saturated and the magnetic switch Sr1 can be closed.
When the magnetic switch Sr1 is closed, a current flows from the secondary side of the step-up transformer TC1 to the capacitor C1, and the capacitor C1 can be charged.

When the capacitor C1 is charged, the magnetic switch Sr2 eventually becomes magnetically saturated and the magnetic switch Sr2 can be closed.
When the magnetic switch Sr2 is closed, a current flows from the capacitor C1 to the capacitor C2, and the capacitor C2 can be charged. At this time, the capacitor C2 may be charged with a pulse width shorter than the pulse width of the current when the capacitor C1 is charged.

When the capacitor C2 is charged, the magnetic switch Sr3 eventually becomes magnetically saturated and the magnetic switch Sr3 can be closed.
When the magnetic switch Sr3 is closed, a current flows from the capacitor C2 to the capacitor C3, and the capacitor C3 can be charged. At this time, the capacitor C3 may be charged with a pulse width shorter than the pulse width of the current when the capacitor C2 is charged.

  As described above, the current flows sequentially from the capacitor C1 to the capacitor C2 and from the capacitor C2 to the capacitor C3, whereby the pulse width of the current can be compressed and the voltage can be increased.

  When the voltage of the capacitor C3 reaches the breakdown voltage of the laser gas, dielectric breakdown may occur in the laser gas between the pair of electrodes 11a and 11b. As a result, the laser gas is excited, laser oscillation is performed, and pulsed laser light can be output. By repeating such a discharge operation by the switching operation of the switch 13a, the pulse laser beam may be output at a predetermined oscillation frequency.

9.2 Configuration of Fly Eye Lens FIG. 24 is a perspective view showing an example of the fly eye lens 41a included in the beam homogenizer 41 described above. In the fly-eye lens 41a, a plurality of concave cylindrical surfaces 411 may be arranged in the Y direction on the first surface of the substrate that transmits light in the ultraviolet region with high transmittance. A plurality of concave cylindrical surfaces 412 may be arranged in the X direction on the second surface opposite to the first surface of the substrate. The position of the front focal plane of the cylindrical surface 411 and the position of the front focal plane of the cylindrical surface 412 may substantially coincide.

  FIG. 25 is a perspective view showing a modification of the fly-eye lens included in the beam homogenizer 41 described above. The fly-eye lens is not limited to one in which cylindrical surfaces are formed on two surfaces of a single substrate, and may be one in which cylindrical surfaces 413 and 414 are formed on two substrates 41c and 41d, respectively. The cylindrical surfaces 413 and 414 are not limited to being concave surfaces, and may be convex surfaces. Other points may be the same as those described with reference to FIG.

9.3 Configuration of Control Unit FIG. 26 is a block diagram illustrating a schematic configuration of the control unit.
Control units such as the doping control unit 45 and the laser system control unit 31 in the above-described embodiments may be configured by general-purpose control devices such as a computer and a programmable controller. For example, it may be configured as follows.

(Constitution)
The control unit includes a processing unit 1000, a storage memory 1005, a user interface 1010, a parallel I / O controller 1020, a serial I / O controller 1030, A / D, and D / A connected to the processing unit 1000. And a converter 1040. Further, the processing unit 1000 may include a CPU 1001, a memory 1002 connected to the CPU 1001, a timer 1003, and a GPU 1004.

(Operation)
The processing unit 1000 may read a program stored in the storage memory 1005. The processing unit 1000 may execute the read program, read data from the storage memory 1005 in accordance with execution of the program, or store data in the storage memory 1005.

  The parallel I / O controller 1020 may be connected to devices 1021 to 102x that can communicate with each other via a parallel I / O port. The parallel I / O controller 1020 may control communication using a digital signal via a parallel I / O port that is performed in the process in which the processing unit 1000 executes a program.

  The serial I / O controller 1030 may be connected to devices 1031 to 103x that can communicate with each other via a serial I / O port. The serial I / O controller 1030 may control communication using a digital signal via a serial I / O port that is performed in a process in which the processing unit 1000 executes a program.

  The A / D and D / A converter 1040 may be connected to devices 1041 to 104x that can communicate with each other via an analog port. The A / D and D / A converter 1040 may control communication using an analog signal via an analog port that is performed in the process in which the processing unit 1000 executes a program.

  The user interface 1010 may be configured such that an operator displays a program execution process by the processing unit 1000, or causes the processing unit 1000 to stop program execution or interrupt processing by the operator.

  The CPU 1001 of the processing unit 1000 may perform program calculation processing. The memory 1002 may temporarily store a program during the course of execution of the program by the CPU 1001 or temporarily store data during a calculation process. The timer 1003 may measure time and elapsed time, and output the time and elapsed time to the CPU 1001 according to execution of the program. When image data is input to the processing unit 1000, the GPU 1004 may process the image data according to the execution of the program and output the result to the CPU 1001.

Devices 1021 to 102x, which are connected to the parallel I / O controller 1020 and can communicate via the parallel I / O port, receive and transmit light emission trigger signals and timing signals of the laser apparatus 2 and other control units. May be used.
The devices 1031 to 103x that are connected to the serial I / O controller 1030 and can communicate via the serial I / O port include the laser device 2, the optical pulse stretcher 16α, the attenuator 18, the XYZ stage 43g, and other control units. It may be used for sending and receiving data. The devices 1041 to 104x connected to the A / D and D / A converter 1040 and capable of communicating via analog ports may be various sensors such as the pulse time waveform measuring unit 19 and the monitor device 44.
With the configuration as described above, the control unit may be able to realize the operation shown in each embodiment.

  The above description is intended to be illustrative only and not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the embodiments of the present disclosure without departing from the scope of the appended claims.

  Terms used throughout this specification and the appended claims should be construed as "non-limiting" terms. For example, the terms “include” or “included” should be interpreted as “not limited to those described as included”. The term “comprising” should be interpreted as “not limited to what is described as having”. Also, the modifier “one” in the specification and the appended claims should be interpreted to mean “at least one” or “one or more”.

The laser doping apparatus according to one aspect of the present disclosure, met laser doping apparatus performs doped semiconductor substrate is irradiated with the pulsed laser beam on the semiconductor substrate, a laser device for outputting first and second pulse laser beam And a control unit that controls the pulse time waveforms of the first and second pulse laser beams , the fluence, and the irradiation region, and the control unit outputs the first pulse time waveform and the first fluence. A first pulsed laser beam having a second pulse time waveform different from the first pulse time waveform and a second fluence different from the first fluence. The first and second pulse laser beams are irradiated so that the second laser beam is irradiated to the second irradiation region of the semiconductor substrate that is different from the first irradiation region. A pulse time waveform, the fluence, the irradiation region may be controlled.

Laser doping method according to another one aspect of the present disclosure, met laser doping method of performing doping the semiconductor substrate is irradiated with the pulsed laser beam on the semiconductor substrate, for outputting a first and second pulse laser beam And controlling the pulse time waveforms of the first and second pulsed laser beams , the fluence, and the irradiation region , the first pulse having the first pulse time waveform and the first fluence. The second pulse laser beam is irradiated with the pulse laser beam on the first irradiation region of the semiconductor substrate and has a second pulse time waveform different from the first pulse time waveform and a second fluence different from the first fluence. Are applied to the second irradiation region of the semiconductor substrate, which is different from the first irradiation region, so that the pulse time waves of the first and second pulse laser beams are irradiated. If the fluence, the irradiation region may be controlled.

Claims (13)

In a laser doping apparatus that performs doping by irradiating a predetermined region of a semiconductor material with pulsed laser light,
A solution supply system for supplying a solution containing a dopant to the predetermined region;
A laser system comprising: at least one laser device that outputs a pulsed laser beam that passes through the solution containing the dopant; and a pulse time waveform adjusting device that adjusts a pulse time waveform of the pulsed laser beam;
A laser doping apparatus comprising:   The laser doping apparatus according to claim 1, wherein the solution supply system includes a pump for forming a flow of the solution containing the dopant along the predetermined region.   The laser doping apparatus according to claim 1, wherein the pulse time waveform adjusting device includes an optical pulse stretcher. The laser system includes a plurality of laser devices,
The pulse time waveform adjusting device includes a delay circuit that adjusts the timing of each pulse laser beam output from the plurality of laser devices,
An optical system that irradiates a predetermined region of the semiconductor material by superimposing each pulse laser beam output from the plurality of laser devices;
The laser doping apparatus according to claim 1. The laser doping apparatus according to claim 4, further comprising a control unit that controls the plurality of laser devices such that the plurality of laser apparatuses output the pulsed laser beams having different pulse time waveforms.   The laser doping apparatus according to claim 1, wherein the semiconductor material is any one of SiC, diamond, and GaN. When the light intensity at time t of the time waveform of the pulse laser beam output from the laser system is I (t), it is defined as ΔT _TIS = [∫I (t) dt] ² / ∫I (t) ² dt The laser doping apparatus according to claim 1, wherein the pulse width is 80 ns or more.   The laser doping apparatus according to claim 1, wherein the solution containing the dopant is an aqueous aluminum chloride solution.   The laser doping apparatus according to claim 1, wherein the solution containing the dopant is an aqueous boric acid solution.   The laser doping apparatus according to claim 1, wherein a wavelength of the pulse laser beam is 248 nm or more and 308 nm or less. In a laser doping apparatus that performs doping by irradiating a predetermined region of a semiconductor material with pulsed laser light,
A solution supply system for supplying a solution containing boron to the predetermined region;
At least one laser device that outputs a pulsed laser beam that passes through the solution containing boron;
A laser doping apparatus comprising: The solution containing boron is an aqueous boric acid solution,
The laser doping apparatus according to claim 11, wherein a wavelength of the pulsed laser light is 248 nm or more and 308 nm or less. In a laser doping method of performing doping by irradiating a predetermined region of a semiconductor material with pulsed laser light,
Supplying a solution containing a dopant to the predetermined region;
Outputting the pulsed laser light that passes through the solution containing the dopant;
Adjusting the pulse time waveform of the pulsed laser light;
A laser doping method comprising:

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