WO2024018784A1

WO2024018784A1 - Laser annealing device, laser annealing method, and laser annealing program

Info

Publication number: WO2024018784A1
Application number: PCT/JP2023/022018
Authority: WO
Inventors: 康弘岡田; 雅史萬
Original assignee: 住友重機械工業株式会社
Priority date: 2022-07-19
Filing date: 2023-06-14
Publication date: 2024-01-25

Abstract

This laser annealing device comprises: a laser pulse shaping unit that shapes the cross-section of a laser pulse LP oscillated by a pulsed laser device into a substantially rectangular shape having a first edge E1 and a second edge E2 that are orthogonal to each other; and a laser pulse scanning unit that scans the laser pulse LP shaped by the laser pulse shaping unit in the plane of a semiconductor wafer 3 along a first direction (Y direction) in which the first edge E1 extends and a second direction (X direction) in which the second edge E2 extends such that a first scanning amount S1 for the laser pulse LP in the interval during which the semiconductor wafer 3 is being irradiated with the laser pulse LP being scanned along the first direction is at most 1/30 of the length of the first edge E1.

Description

Laser annealing equipment, laser annealing method, laser annealing program

The present invention relates to a laser annealing device and the like.

Patent Document 1 discloses a laser annealing technique in which a semiconductor wafer is irradiated with a laser pulse shaped into a line (hereinafter also referred to as a line beam). The line beam is scanned in the short width direction, but in order to avoid damage to the semiconductor wafer due to concentrated laser pulse irradiation in a short period of time, the scanning amount at the interval between laser pulses is set to be greater than or equal to the width of the line beam. has been done. Thus, two consecutive laser pulses are applied to adjacent non-overlapping areas on the semiconductor wafer. On the other hand, in order to achieve the intended purpose of laser annealing, it is necessary to irradiate the same spot on the semiconductor wafer multiple times, so Patent Document 1 discloses folded scanning along the width direction of the line beam (i.e., back and forth scanning). scanning) is performed repeatedly.

JP2018-67642A

Although it depends on the purpose of laser annealing and the laser equipment used, with laser annealing technology that avoids intensive overlapping irradiation as in Patent Document 1, there is a possibility that various parts of the semiconductor wafer will not be sufficiently heated, and the semiconductor wafer The intended purpose of repairing damage by melting the surface of the semiconductor wafer and activating dopants implanted into the semiconductor wafer may not be achieved.

The present invention has been made in view of these circumstances, and it is an object of the present invention to provide a laser annealing device and the like that can effectively perform annealing treatment by intensive overlapping irradiation.

In order to solve the above problems, a laser annealing device according to an aspect of the present invention provides a laser annealing device that shapes a cross section of a laser pulse emitted by a pulsed laser device into a substantially rectangular shape having a first side and a second side that are orthogonal to each other. A laser pulse scanning unit that scans the laser pulse shaped by the laser pulse shaping unit and the laser pulse shaping unit within the plane of the semiconductor wafer along a first direction in which the first side extends and a second direction in which the second side extends. and a laser pulse scanning unit in which the scanning amount of the laser pulse scanned along the first direction at an interval at which the semiconductor wafer is irradiated is 1/30 or less of the length of the first side. .

In this aspect, the same location on the semiconductor wafer is continuously irradiated 30 times or more with a laser pulse scanned along the first direction by the laser pulse scanning unit. Therefore, the temperature of the semiconductor wafer can be raised effectively, and the intended purpose of laser annealing, such as repairing damage caused by melting the semiconductor wafer surface and activating dopants implanted into the semiconductor wafer, can be efficiently achieved. can.

Another aspect of the present invention is a laser annealing method. This method includes a laser pulse shaping step of shaping a cross section of a laser pulse emitted by a pulse laser device into a substantially rectangular shape having first and second sides orthogonal to each other, and a laser pulse shaped in the laser pulse shaping step. , a laser pulse scanning step of scanning within the plane of the semiconductor wafer along a first direction in which the first side extends and a second direction in which the second side extends, wherein the laser pulse scanned along the first direction is applied to the semiconductor wafer; and a laser pulse scanning step in which the scanning amount of the laser pulse at intervals at which the wafer is irradiated is 1/30 or less of the length of the first side.

It should be noted that the present invention also encompasses any combination of the above components and the conversion of these expressions into methods, devices, systems, recording media, computer programs, etc.

According to the present invention, annealing treatment can be effectively performed by intensive overlapping irradiation.

FIG. 1 is a perspective view schematically showing the configuration of a laser annealing device. The configuration of an optical fiber, which is a main part of a fiber laser device, and the principles of laser pulse generation and amplification in the optical fiber are schematically shown. The configuration of a pulse laser device as a fiber laser device is schematically shown. 3 shows the time course of the surface temperature of a semiconductor wafer irradiated with various laser beams. 2 schematically shows a laser pulse scanned within the surface of a semiconductor wafer.

Hereinafter, modes for carrying out the present invention (hereinafter also referred to as embodiments) will be described in detail with reference to the drawings. In the description and/or drawings, the same or equivalent components, members, processes, etc. are denoted by the same reference numerals, and redundant description will be omitted. The scales and shapes of the parts shown in the drawings are set for convenience to simplify the explanation, and should not be interpreted in a limited manner unless otherwise stated. The embodiments are illustrative and do not limit the scope of the present invention. Not all features or combinations thereof described in the embodiments are necessarily essential to the present invention.

FIG. 1 is a perspective view schematically showing the configuration of a laser annealing apparatus 1 according to an embodiment of the present invention. The laser annealing device 1 is a device that performs an annealing process (heating process) by irradiating the semiconductor wafer 3 with laser pulses generated by a pulsed laser device 2 .

The semiconductor wafer 3 fixedly mounted on the wafer table 31 can be driven integrally with the wafer table 31 in the illustrated x direction by a stage device 4, which will be described later. Further, the laser pulse (laser light) oscillated by the pulse laser device 2 can be scanned in the y direction orthogonal to the x direction by a galvano scanner 14, which will be described later. Laser pulses (laser light) scanned in the y direction by the galvano scanner 14 are reflected by a mirror 16, which will be described later, and are incident on the semiconductor wafer 3 in the z direction orthogonal to the x and y directions.

Hereinafter, directions regarding the configuration and/or operation of the laser annealing apparatus 1 will be described based on a three-dimensional orthogonal coordinate system whose coordinate axes are XYZ axes that are orthogonal to each other. The x direction, which is the driving direction of the semiconductor wafer 3, is parallel to the X-axis direction (X direction), and the y direction, which is the scanning direction of the laser pulse (laser light), is parallel to the Y-axis direction (Y direction). The z direction, which is the direction of incidence of the laser pulse (laser light) on the wafer 3, is parallel to the Z-axis direction (Z direction). Hereinafter, for convenience, the x direction and the X direction will also be referred to as the vertical direction, the y direction and the Y direction will also be referred to as the horizontal direction, and the z direction and the Z direction will also be referred to as the height direction. Further, as described later, the Y direction is the first direction in this embodiment, and the X direction is the second direction in this embodiment.

The pulse laser device 2 is a laser device that oscillates laser pulses at a frequency of 100kHz or higher. In order to fully obtain the functions and effects described below of the laser annealing device 1 according to the present embodiment, the frequency of the laser pulse oscillated by the pulsed laser device 2 is, for example, between 100kHz and 10MHz, and between 500kHz and 5MHz. , more preferably between 700kHz and 3MHz. In this embodiment, unless otherwise specified, an example will be described in which the frequency of the laser pulse oscillated by the pulsed laser device 2 is 1 MHz.

The pulse laser device 2 according to the present embodiment is configured by, for example, a fiber laser device that oscillates laser pulses using an optical fiber. FIG. 2 schematically shows the configuration of an optical fiber 20, which is a main part of the fiber laser device, and the principle of generation and amplification of laser pulses LP in the optical fiber 20. The optical fiber 20 includes a core 201 in the center, a first clad 202 provided around the core 201, and a second clad 203 provided around the first clad 202. The refractive index of the core 201 is higher than the refractive index of the first cladding 202, and the refractive index of the first cladding 202 is higher than the refractive index of the second cladding 203. That is, the refractive index of the optical fiber 20 is higher as it is closer to the center (core 201) and lower as it is closer to the periphery (second cladding 203).

Excitation light EL generated by a light emitting element such as a laser diode enters from one end of the optical fiber 20 (for example, the left end in FIG. 2). This excitation light EL propagates inside the core 201 and the first cladding 202 while being totally reflected at the interface between the first cladding 202 and the second cladding 203. Each time the excitation light EL passes through the core 201, it excites a rare earth element such as Yb added to the core 201, and generates stimulated emission light that becomes the source of the laser pulse LP (laser light). The stimulated emission light generated in the core 201 propagates inside the core 201 while being totally reflected at the interface between the core 201 and the first cladding 202 . As described later, mirrors such as total reflection mirrors such as FBG (Fiber Bragg Grating) and output mirrors are formed at both ends of the core 201, and the stimulated emission light that is repeatedly reflected between these mirrors is reflected back to the core. A laser pulse LP (laser light) is formed by being amplified while reciprocating inside the 201. This laser pulse LP is output to the outside of the optical fiber 20 from an output mirror formed at one end of the core 201 (for example, the right end in FIG. 2).

FIG. 3 schematically shows the configuration of a pulse laser device 2 as a fiber laser device including an optical fiber 20 as shown in FIG. The pulse laser device 2 includes an excitation light supply section 21, a laser light generation section 22, and a laser light supply section 23. The excitation light supply unit 21 includes a light emitting element 211 such as one or more laser diodes that emits light that is the source of the excitation light EL, and when a plurality of light emitting elements 211 are provided, combines the respective lights to generate the excitation light EL. It includes an optical coupling section 212 to be formed. The excitation light supply section 21 supplies excitation light EL based on the light emitted by the light emitting element 211 to the laser light generation section 22 .

The laser light generation unit 22 includes the aforementioned optical fiber 20 to which the excitation light EL is supplied from the input end (left end in FIG. 3), and an input mirror 221 and an output mirror 222 formed at both ends thereof. The input mirror 221 and the output mirror 222 are both formed by FBG at both ends of the core 201, for example. It is preferable that the reflectance of the input mirror 221 provided on the input side (excitation light supply section 21 side) is higher than the reflectance of the output mirror 222 provided on the output side (laser light supply section 23 side). In particular, the input mirror 221 is preferably configured as a total reflection mirror that totally reflects the stimulated emission light inside the core 201, which is the source of the laser pulse LP (laser light), toward the output side. The output mirror 222 reflects a part of the stimulated emission light inside the core 201 to the input side, and outputs the rest to the laser light supply section 23 .

The laser light supply section 23 includes an optical fiber 231 that guides the laser pulse LP (laser light) generated by the laser light generation section 22 to the output point OP of the pulse laser device 2. Note that the output point of the laser beam generation section 22 may be the output point OP of the pulsed laser device 2, and in that case, it is not necessary to provide the laser beam supply section 23.

In FIG. 1, the laser pulse LP is emitted from the output point OP of the pulse laser device 2 in the X direction. A laser annealing device 1 that guides this laser pulse LP to a semiconductor wafer 3 to be irradiated includes a beam expander 11, a mirror 12, a beam shaping optical element 13, a galvano scanner 14, an fθ lens 15, and a mirror 16. .

The beam expander 11 adjusts the laser pulse LP (laser light) emitted from the output point OP of the pulse laser device 2 to a predetermined size (diameter). For example, when the cross section of the laser pulse LP (laser light) emitted from the output point OP of the pulse laser device 2 is approximately circular with a diameter D0, the beam expander 11 adjusts the cross section of the laser pulse LP (laser light) to a predetermined shape. Convert (typically enlarge) into a substantially circular shape with diameter D1. The beam expander 11 is composed of a plurality of

lenses

111, 112, and 113. Typically, lens 111 is a convex lens, lens 112 is a concave lens, and lens 113 is a convex lens. However, the number and type of lenses and other optical elements constituting the beam expander 11 are arbitrary as long as the desired function and/or effect of adjusting the size of the laser pulse LP can be obtained. For example, the beam expander 11 may be composed of two or more convex lenses and one or more concave lenses arranged in any order, or may be composed only of three or more convex lenses.

The mirror 12 reflects the laser pulse LP whose size has been adjusted by the beam expander 11, and changes its traveling direction from the X direction to the Y direction.

The beam shaping optical element 13 is a laser pulse shaping section that shapes the laser pulse LP whose size has been adjusted by the beam expander 11 to adjust its shape and/or intensity distribution. For example, the cross section of the laser pulse LP whose size has been adjusted by the beam expander 11 is approximately circular and has an intensity distribution that follows a Gaussian distribution or a normal distribution, but is shaped by the beam shaping optical element 13 to be approximately rectangular and have an approximately uniform intensity distribution. be done. Such a beam shaping optical element 13 is constituted by, for example, a diffractive optical element (DOE).

The galvano scanner 14 is a laser pulse scanning unit that scans the laser pulse LP shaped by the beam shaping optical element 13 along the y direction (Y direction), that is, the first direction. The galvano scanner 14 includes a galvano mirror 141 as a drivable optical element that reflects an incident laser pulse LP and directs it to a desired scanning position in a first direction (y direction), and a galvano mirror 141 that rotates the galvano mirror 141 around the Z axis. It includes a motor 142 that rotates. The motor 142 adjusts the rotational position or rotation angle of the galvano mirror 141 around the Z axis, so that the laser pulse LP incident on the galvano mirror 141 is reflected to an arbitrary y-direction (first direction) position.

Note that the laser pulse scanning unit that directs the incident laser pulse LP to a desired scanning position in the y direction (first direction) is not limited to the galvano scanner 14, but may also be a polygon mirror scanner equipped with a polygon mirror (optical element) that can be rotated. Alternatively, it may be configured by an optical element such as a drivable MEMS (Micro Electro Mechanical Systems) mirror. Further, the scanning direction of the laser pulse LP by the laser pulse scanning unit such as the galvano scanner 14 is not limited to the y direction (Y direction), but may be a direction intersecting the y direction (Y direction) such as the x direction (X direction). , the x direction (X direction) and the y direction (Y direction) may be used. As in the latter case, when the laser pulse scanning unit such as the galvano scanner 14 can scan the laser pulse LP within the xy plane (XY plane), that is, within the plane of the semiconductor wafer 3, the semiconductor wafer 3 and the wafer table 31 are It is not necessary to provide a stage device 4 that is driven in a direction (X direction) or the like. In this case, the galvano scanner 14 and the like constitute a laser pulse scanning unit in the first direction (Y direction) and the second direction (X direction).

The fθ lens 15 focuses the laser pulse LP scanned in the y direction (Y direction) by the galvano scanner 14 onto the semiconductor wafer 3 to be annealed. A mirror 16 provided between the fθ lens 15 and the semiconductor wafer 3 reflects the laser pulse LP in the X direction from the fθ lens 15 and irradiates the semiconductor wafer 3 in the Z direction (z direction). The laser pulse LP thus focused on the semiconductor wafer 3 by the fθ lens 15 and the mirror 16 moves in the Y direction within the plane of the semiconductor wafer 3 by scanning in the Y direction by the galvano scanner 14. Although the size of the laser pulse LP focused on the semiconductor wafer 3 can be arbitrarily designed, it is preferably between 0.10 mm square and 0.15 mm square, and more preferably between 0.12 mm square and 0.13 mm square. Furthermore, the scanning speed of the laser pulse LP in the Y direction on the semiconductor wafer 3 surface (and/or the driving speed of the semiconductor wafer 3 in the X direction by the stage device 4) can be arbitrarily designed; for example, 100 cm/s and 500 cm. It is preferably between 250 cm/s and 350 cm/s, more preferably between 250 cm/s and 350 cm/s.

Further, the stage device 4 is a drive device that drives the semiconductor wafer 3 and the wafer table 31 relative to the laser pulse LP along the x direction (X direction), that is, the second direction. A laser pulse scanning section that scans laser pulses LP along two directions is configured. By this stage device 4, the laser pulse LP is relatively moved in the X direction within the surface of the semiconductor wafer 3.

In this way, the scanning of the laser pulse LP in the y direction by the galvano scanner 14 as the laser pulse scanning section in the first direction (Y direction) and the scanning of the laser pulse LP in the y direction by the laser pulse scanning section in the second direction (X direction) are performed. By combining the driving of the semiconductor wafer 3 in the x direction, the laser pulse LP can be scanned within the xy plane (XY plane), that is, within the plane of the semiconductor wafer 3. Note that the driving direction of the semiconductor wafer 3 by the stage device 4 is not limited to the x direction (X direction), but may also be a direction intersecting the x direction (X direction) such as the y direction (Y direction), or a direction intersecting the x direction (X direction) such as the y direction (Y direction). ) and the y direction (Y direction). As in the latter case, when the stage device 4 can drive the semiconductor wafer 3 relative to the laser pulse LP within the xy plane (XY plane), a galvanometer that scans the laser pulse LP in the y direction (Y direction) etc. The scanner 14 may not be provided. In this case, the stage device 4 constitutes a laser pulse scanning section in the first direction (Y direction) and the second direction (X direction).

FIG. 4 shows the time course of the surface temperature of the semiconductor wafer 3 irradiated with various laser beams. The solid line indicates the surface temperature when the laser pulse LP of high frequency (800 kHz in the illustrated example) oscillated by the fiber laser device as the pulse laser device 2 according to the present embodiment is irradiated. The dashed line indicates the surface temperature when irradiated with a high peak power (typically several 100 kW) and low frequency (typically between 2 kHz and several 10 kHz) laser pulses emitted by conventional pulsed laser equipment. show. The dashed-dotted line indicates the surface temperature when irradiated with a low peak power (typically several kW) and low frequency laser light emitted by a conventional diode laser device. Note that the peak power is the value obtained by dividing the pulse energy by the pulse width.

A high peak power, low frequency laser pulse emitted by a conventional pulse oscillation laser device shown by a broken line is used for the purpose of repairing damage caused by dopant ion implantation by melting the surface of the semiconductor wafer 3. If the semiconductor wafer 3 is made of general silicon, the surface will be melted by heating it above its melting point (1,410° C.). In the illustrated example, the surface temperature of the semiconductor wafer 3 instantaneously rises to over 1,500°C due to the high peak power laser pulses emitted by the conventional pulsed laser device shown by the broken line. The surface of the formed semiconductor wafer 3 is melted and damage is repaired. However, since the conventional laser pulse has a low frequency, the surface temperature of the semiconductor wafer 3 drops rapidly immediately after the laser pulse is irradiated. For this reason, the interior or subsurface of the semiconductor wafer 3 into which the dopant is implanted is not sufficiently heated, and the dopant is not activated.

Therefore, for the purpose of activating the dopant implanted into the semiconductor wafer 3, a low peak power and low frequency laser beam oscillated by a conventional diode laser device shown by a dashed line is used. Since this laser beam has a low peak power, it cannot heat the surface of the semiconductor wafer 3 above its melting point, but it continuously heats the inside or under the surface of the semiconductor wafer 3 to activate the implanted dopant. can. In this way, a pulsed laser device (dashed line) is generally used for melting on the surface of the semiconductor wafer 3, and a diode laser device (dotted chain line) is used for activation below the surface of the semiconductor wafer 3. Met. Since it is necessary to prepare different laser devices for annealing for different purposes, this has led to an increase in the size and cost of the laser annealing device.

On the other hand, according to the high frequency laser pulse LP according to the present embodiment shown by the solid line, one pulse laser device 2 (fiber laser device etc.) melts the surface of the semiconductor wafer 3 and melts the surface of the semiconductor wafer 3. Activation at the bottom can be effectively achieved. Specifically, the pulsed laser device 2 according to the present embodiment performs a surface melting step (a period of "surface melting" shown in the figure) in which the surface of the semiconductor wafer 3 is heated to a temperature higher than the melting point and melted by a plurality of laser pulses LP. Continuing from the surface melting step, the semiconductor wafer 3 is irradiated with laser pulses LP, and the temperature below the surface of the semiconductor wafer 3 is raised to a predetermined activation temperature or higher for at least a predetermined period of time using a plurality of laser pulses LP. , an activation step (the illustrated "activation" period) for activating the dopant added below the surface of the semiconductor wafer 3.

In the surface melting step, the surface temperature of the semiconductor wafer 3 rises above the melting point (1,410° C.) by a large number of laser pulses LP that are intermittently irradiated at a high frequency (800 kHz in the illustrated example). Therefore, the surface of the semiconductor wafer 3 is melted, and damage caused by dopant ion implantation or the like is repaired. Note that, as shown in the figure, the individual laser pulses LP do not have sufficient power to heat the surface of the semiconductor wafer 3 above the melting point, but the semiconductor wafer 3 is heated by being irradiated with high frequency. As a result of accumulation, the surface temperature can be raised above the melting point. The surface melting step starts when the surface temperature of the semiconductor wafer 3 rises above the melting point, and ends when the surface temperature of the semiconductor wafer 3 falls below the melting point.

As mentioned above, the laser pulse LP is scanned on the semiconductor wafer 3 by the galvano scanner 14 as a laser pulse scanning unit along the Y direction (y direction), that is, the first direction, but the laser pulse LP has a width in the Y direction. The time required for the LP to pass one point on the semiconductor wafer 3 is substantially equal to the time of the surface melting step. Strictly speaking, the time from when the laser pulse LP starts hitting a point on the semiconductor wafer 3 until the surface temperature reaches the melting point, and the time from when the laser pulse LP passes a point on the semiconductor wafer 3 until the surface temperature falls below the melting point. Due to time constraints, there may be a slight time difference.

In the activation step, the semiconductor wafer 3 is irradiated with the laser pulse LP continuously from the surface melting step, so that the temperature inside or under the surface of the semiconductor wafer 3 into which the dopant is implanted is increased to a predetermined activation temperature or higher. , the dopant is activated. The activation temperature may vary depending on the type of dopant and the material of the semiconductor wafer 3 (silicon, silicon carbide, gallium nitride, etc.), but the most common method is to implant an acceptor (P-type dopant) such as boron into a silicon semiconductor wafer 3. In a typical case, the temperature is about 1,000℃. Furthermore, in order to sufficiently activate the dopant added inside or under the surface of the semiconductor wafer 3, it is necessary to maintain the temperature of that region at or above the activation temperature for a predetermined period of time. This predetermined time may also vary depending on the type and amount of dopant and the material of the semiconductor wafer 3, but is typically about 10 μs. Thus, in the activation step, the interior or subsurface region of the semiconductor wafer 3 into which the dopants have been implanted (typically up to 10 μm below the surface of the semiconductor wafer 3) is heated to 1000° C. for at least 10 μs. A typical goal is to increase the temperature above this level.

The activation step starts when the temperature of the activation region under the surface of the semiconductor wafer 3 into which the dopant is implanted rises above the activation temperature, and ends when the temperature of the activation region falls below the activation temperature. do. Since FIG. 4, which shows the surface temperature of the semiconductor wafer 3, does not show the temperature of the activation region below the surface, the start timing and end timing of the activation step are shown as a guide. Typically, the activation step is shorter than the surface fusing step, as shown. Additionally, the start timing of the activation step is typically later than the start timing of the surface melting step. Furthermore, the end timing of the activation step is substantially equal to the end timing of the surface melting step. However, strictly speaking, the temperature of the activation region in the semiconductor wafer 3 involved in the activation step is less likely to drop than the temperature of the surface of the semiconductor wafer 3 involved in the surface melting step. The timing of the end of the surface melting step (the surface temperature decreases below the melting point) is considered to be slightly later than the end timing of the surface melting step (the surface temperature decreases below the melting point).

Note that if the amount of dopant added to the activation region is larger than usual or if the activation region is deeper than 10 μm, the activation step may be made longer than 10 μs. Specifically, the activation step can be lengthened by slowing down the scanning speed of the laser pulse LP in the Y direction (y direction), that is, the first direction, by the galvano scanner 14 as the laser pulse scanning unit. Alternatively, the same effect can be obtained by setting the oscillation frequency of the laser pulse LP by the pulse laser device 2 higher than 800 kHz. If the activation step is lengthened, the surface melting step will inevitably be lengthened, but the surface of the semiconductor wafer 3 may become overheated due to heat radiation from the surface of the semiconductor wafer 3 during the non-pulse period when the intermittent laser pulse LP is not irradiated. (In the example shown, the surface temperature is kept below 2,000°C.) In this way, according to the present embodiment, the surface melting step can be appropriately performed regardless of the length of the activation step.

According to this embodiment, one pulsed laser device 2 continues to irradiate the semiconductor wafer 3 with laser pulses LP through the successive surface melting steps and activation steps, thereby combining melting on the surface and activation below the surface. You can do it.

FIG. 5 schematically shows the laser pulse LP scanned within the semiconductor wafer 3 (in the XY plane) by the laser pulse scanning unit (galvano scanner 14 and/or stage device 4). It should be noted that, due to space constraints, the number and dimensions of the scanning segments described below do not necessarily correspond to practical embodiments, but are adjusted as appropriate for illustration.

As described above, the cross section of the laser pulse LP irradiated onto the semiconductor wafer 3 is shaped into a substantially rectangular shape by the beam shaping optical element 13 as a laser pulse shaping section. This substantially rectangular cross section has a first side E1 and a second side E2 that are orthogonal to each other. The first direction in which the first side E1 extends is approximately equal to the Y direction, which is the scanning direction of the laser pulse LP by the galvano scanner 14, and the second direction in which the second side E2 extends is the scanning direction of the laser pulse LP by the stage device 4. is approximately equal to the X direction. In the illustrated example, the beam shaping optical element 13 shapes the cross section of the laser pulse LP into a substantially square shape. In this case, the length of the first side E1 in the Y direction and the length of the second side E2 in the X direction are approximately equal. In the following example, it is assumed that the lengths of the first side E1 and the second side E2 are both 100 μm (0.1 mm).

In the illustrated example, the scanning of the laser pulse LP is started from the scanning start position indicated by the dotted square in the upper left. As shown by a series of arrows in FIG. 5, the approximately square laser pulse LP is scanned in the +Y direction by the galvano scanner 14, and at the end of the semiconductor wafer 3 in the +Y direction, the stage device 4 moves the laser pulse LP in the +X direction as described later. The end of the semiconductor wafer 3 in the -Y direction is scanned by a second scanning amount S2 in the +X direction by the stage device 4, and is scanned by the galvano scanner 14 in the -Y direction. Scanned in the +Y direction.

The laser pulse LP is intermittently irradiated onto the semiconductor wafer 3 at a high frequency (for example, 1 MHz) while being scanned along the first direction (Y direction) by the galvano scanner 14 as the first laser pulse scanning unit. The illustrated first scanning amount S1 is the scanning amount in the first direction (Y direction) in the interval at which the semiconductor wafer 3 is irradiated with the laser pulse LP. In other words, each time the scanning amount in the first direction (Y direction) by the galvano scanner 14 becomes a multiple of the first scanning amount S1, the semiconductor wafer 3 is intermittently irradiated with a substantially square laser pulse LP.

The first scanning amount S1 can be adjusted by the scanning speed in the first direction (Y direction) by the galvano scanner 14 and the oscillation frequency of the laser pulse LP by the pulse laser device 2. For example, if the scanning speed in the first direction (Y direction) by the galvano scanner 14 is 333 cm/s and the oscillation frequency of the laser pulse LP by the pulse laser device 2 is 1 MHz, the first scanning amount S1 is 3.33 μm. Become. In this example, since the length of the first side E1 of the laser pulse LP is 100 μm, the galvano scanner 14 scans the laser pulse LP in the first direction (Y direction) by the length of the first side E1. Then, the laser pulse LP is sequentially applied 30 times (100 μm/3.33 μm) to positions shifted in the first direction (Y direction) by the first scanning amount S1. If the number of irradiations during which the laser pulse LP is scanned by the length of the first side E1 is M, then "E1=M×S1" (in this example, E1=100μm=30×3.33μm= M×S1) holds true.

In this embodiment, it is preferable that "M≧30". In other words, the first scan of the laser pulse LP scanned along the first direction (Y direction) by the galvano scanner 14 as the first laser pulse scanning unit at the interval at which the semiconductor wafer 3 is irradiated with the laser pulse LP. It is preferable that the amount S1 is 1/30 or less of the length of the first side E1. In this case, the overlap rate of two consecutive laser pulses LP is equal to or higher than "(E1-S1)/E1=(M-1)/M=29/30=about 97%". Although FIG. 5 shows an example where M=20 for convenience due to space limitations, the following description will be made using an example where M=30.

The laser pulse LP that is turned back at each end (lower end and/or upper end in FIG. 5) of the semiconductor wafer 3 in the first direction (Y direction) is scanned back and forth in the first direction (Y direction) by the galvano scanner 14. Ru. In such a reciprocating scan, the laser pulse LP is irradiated in the first direction (Y direction), which is the turning position of the laser pulse LP, so that different (shifted) X direction (second direction) ranges of the semiconductor wafer 3 are irradiated with the laser pulse LP. At each end, the stage device 4 scans the laser pulse LP in the second direction (X direction) by a second scanning amount S2.

The scanning speed in the second direction (X direction) by the stage device 4 as the second laser pulse scanning section is the scanning speed in the first direction (Y direction) by the galvano scanner 14 as the first laser pulse scanning section (for example, 333 cm /s) may be the same or significantly different. In a typical example, the scanning speed (driving speed) by the stage device 4 is significantly smaller than the scanning speed by the galvano scanner 14. In this case, if the oscillation frequency of the laser pulse LP remains high (for example, 1 MHz) during scanning in the first direction (Y direction), an excessive number of times will be generated during scanning in the second direction (X direction) by the stage device 4. There is a risk that the semiconductor wafer 3 may be irradiated with the laser pulse LP of ). Therefore, during scanning in the second direction (X direction) by the stage device 4, the oscillation frequency of the laser pulse LP may be lowered, or the oscillation of the laser pulse LP by the pulse laser device 2 may be temporarily stopped. Alternatively, the laser pulse LP may be temporarily evacuated from the semiconductor wafer 3 by the galvano scanner 14 or other optical element.

The second scanning amount S2 in the second direction (X direction) by the stage device 4 is preferably 1/3 or less of the length of the second side E2 of the laser pulse LP. The second scanning amount S2 in the illustrated example is 1/3 (33.3 μm) of the length (100 μm) of the second side E2. Further, it is assumed that the semiconductor wafer 3 is not irradiated with the laser pulse LP during the second scanning amount S2 (33.3 μm) by the stage device 4. In this example, while the laser pulse LP is scanned by the stage device 4 in the second direction (X direction) by the length of the second side E2, the laser pulse LP is scanned three times (100 μm / 33.3 μm). The light is sequentially irradiated to positions shifted in the second direction (X direction) by the second scanning amount S2. If the number of irradiations during which the laser pulse LP is scanned by the length of the second side E2 is N, then "E2=N×S2" (in this example, E2=100μm=3×33.3μm= N×S2) holds true. Here, the overlap rate of two consecutive laser pulses LP is equal to or higher than "(E2-S2)/E2=(N-1)/N=2/3=about 67%".

In the above example, the semiconductor wafer 3 is irradiated with M=30 laser pulses LP while the galvano scanner 14 scans the length of the first side E1, and the stage device 4 scans the length of the second side E2. During this period, the semiconductor wafer 3 is irradiated with N=3 laser pulses LP. As a result, when the semiconductor wafer 3 (XY plane) is divided into scan segments having a first side with a length of the first scan amount S1 and a second side with a length of the second scan amount S2, the end of the semiconductor wafer 3 The laser pulse LP is irradiated onto most of the scanning segments (for example, the hatched scanning segments typically shown in FIG. 5) except for the area (M×N=30×3=90 times). As mentioned above, M is preferably set to 30 or more, and N is preferably set to 3 or more, so according to the present embodiment, most of the scanning segments excluding the edge of the semiconductor wafer 3 are scanned 90 times or more. The laser pulse LP can be irradiated over the entire range. Thus, a series of surface melting and activation steps can be effectively carried out with a large number of laser pulses LP, as described with respect to FIG.

According to this embodiment, which can increase the number of times the laser pulse LP is irradiated to each scanning segment as described above, variations in the energy and profile (intensity distribution, etc.) of the laser pulse LP irradiated each scanning segment can be reduced. The influence can be reduced, and highly uniform annealing treatment (particularly the surface melting step and the activation step) can be performed over each scan segment and the entire surface of the semiconductor wafer 3. Here, the number of times M×N of irradiation of the laser pulse LP to each scanning segment is considered to have the effect of suppressing fluctuations in the fluence, which is directly linked to the uniformity of the annealing process, to “1/√(M×N)”.

The present invention has been described above based on the embodiments. It will be obvious to those skilled in the art that various modifications can be made to the combinations of components and processes in the exemplary embodiments, and such modifications are within the scope of the present invention.

Note that the configuration, operation, and function of each device and each method described in the embodiments can be realized by hardware resources or software resources, or by cooperation of hardware resources and software resources. As hardware resources, for example, a processor, ROM, RAM, and various integrated circuits can be used. As software resources, for example, programs such as operating systems and applications can be used.

The present invention relates to a laser annealing device and the like.

1 Laser annealing device, 2 Pulsed laser device, 3 Semiconductor wafer, 4 Stage device, 11 Beam expander, 13 Beam shaping optical element, 14 Galvano scanner, 20 Optical fiber, 22 Laser light generation section, E1 first side, E2 No. 2nd side, LP laser pulse.

Claims

a laser pulse shaping unit that shapes a cross section of a laser pulse emitted by the pulsed laser device into a substantially rectangular shape having a first side and a second side that are orthogonal to each other;
A laser pulse scanning unit that scans the laser pulse shaped by the laser pulse shaping unit within a plane of a semiconductor wafer along a first direction in which the first side extends and a second direction in which the second side extends. a laser pulse scanning unit, wherein the scanning amount of the laser pulse scanned along the first direction at an interval at which the semiconductor wafer is irradiated is 1/30 or less of the length of the first side; and,
A laser annealing device equipped with.
The scanning amount of the laser pulse scanned along the second direction by the laser pulse scanning section at an interval at which the semiconductor wafer is irradiated with the laser pulse is 1/3 or less of the length of the second side. A laser annealing apparatus according to claim 1.
The laser annealing apparatus according to claim 1 or 2, wherein the laser pulse shaping section shapes the cross section of the laser pulse into a substantially square shape.
The laser pulse scanning unit that scans the laser pulse along the first direction is configured by a drivable optical element that directs the incident laser pulse to a desired scanning position in the first direction. 3. The laser annealing apparatus according to 1 or 2.
1 . The laser pulse scanning unit that scans the laser pulse along the second direction is configured by a driving device that drives the semiconductor wafer relative to the laser pulse along the second direction. Or the laser annealing apparatus according to 2.
The laser pulse scanning section includes:
The semiconductor wafer is irradiated with the laser pulse shaped by the laser pulse shaping unit while scanning at least along the first direction, and the surface of the semiconductor wafer is heated to a temperature above the melting point by the plurality of laser pulses. a surface melting step of melting the
Continuing from the surface melting step, the semiconductor wafer is irradiated with the laser pulse while scanning at least along the first direction, and the plurality of laser pulses are applied under the surface of the semiconductor wafer for at least a predetermined period of time. an activation step of raising the temperature to a predetermined activation temperature or higher to activate the dopant added below the surface of the semiconductor wafer;
The laser annealing apparatus according to claim 1 or 2, wherein the laser annealing apparatus performs the following.
7. The laser annealing apparatus according to claim 6, wherein in the activation step, a region up to 10 μm below the surface of the semiconductor wafer is heated to 1000° C. or higher for at least 10 μs.
The laser annealing device according to claim 1 or 2, wherein the pulse laser device oscillates the laser pulse at a frequency of 100 kHz or more.
The laser annealing device according to claim 1 or 2, wherein the pulse laser device is a fiber laser device that oscillates the laser pulse using an optical fiber.
a laser pulse shaping step of shaping a cross section of a laser pulse emitted by the pulsed laser device into a substantially rectangular shape having first sides and second sides perpendicular to each other;
A laser pulse scanning step of scanning the laser pulse shaped in the laser pulse shaping step within the plane of the semiconductor wafer along a first direction in which the first side extends and a second direction in which the second side extends. a laser pulse scanning step in which a scanning amount of the laser pulse scanned along the first direction at an interval at which the semiconductor wafer is irradiated is 1/30 or less of the length of the first side; and,
A laser annealing method comprising:
a laser pulse shaping step of shaping a cross section of a laser pulse emitted by the pulsed laser device into a substantially rectangular shape having first sides and second sides perpendicular to each other;
a laser pulse scanning step of scanning the laser pulse shaped in the laser pulse shaping step within the plane of the semiconductor wafer along a first direction in which the first side extends and a second direction in which the second side extends; a laser pulse scanning step in which the scanning amount of the laser pulse scanned along the first direction at an interval at which the semiconductor wafer is irradiated is 1/30 or less of the length of the first side; and,
A laser annealing program that runs on a computer.