Laser irradiation device, laser irradiation method, and method for manufacturing compound semiconductor device

Abstract

A laser irradiation device (1) according to the present embodiment irradiates a wafer comprising a compound semiconductor with laser light in order to form a rear surface electrode of a semiconductor device formed on the wafer. The laser irradiation device comprises: a stage (110) that holds the wafer (W); a chamber (80) that houses the stage (110) and a laser light source (10) that generates the laser light (L1); a window unit (50) that is provided in the chamber (80) and includes a window (502) through which the laser light passes; and a dust collector (60) that is provided directly below the window unit (50) and is provided with a supply port (603) for supplying a gas and an exhaust port (602) for discharging dust.

Description

Laser irradiation apparatus, laser irradiation method, and compound semiconductor device manufacturing method

[0001] The present disclosure relates to a laser irradiation apparatus, a laser irradiation method, and a method for manufacturing a compound semiconductor device.

[0002] Patent Document 1 discloses a laser annealing device using an excimer laser. In Patent Document 1, a levitation unit levitates a substrate, and a transport unit transports the substrate. A line-shaped laser beam is irradiated onto the substrate during transport. Furthermore, this laser irradiation device has a line sensor provided on the substrate. The line sensor captures an image of the substrate during transport.

[0003] JP 2018-64048 A

[0004] In such a device, it is desirable to irradiate the laser light appropriately.

[0005] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

[0006] According to one embodiment, the laser irradiation apparatus is a laser irradiation apparatus that irradiates laser light to form a back electrode of a semiconductor device formed on a wafer made of a compound semiconductor, and includes: a stage that holds the wafer; a laser light source that generates the laser light; a chamber that houses the stage; a window unit that is provided in the chamber and includes a window through which the laser light passes; and a dust collector that is provided directly below the window unit and that has a supply port that supplies gas toward the wafer and an exhaust port that discharges dust generated by laser irradiation.

[0007] According to one embodiment, a laser irradiation method is a laser irradiation method using a laser irradiation apparatus that irradiates a wafer with laser light to form a back electrode of a compound semiconductor device, and includes the steps of: (A1) generating laser light; and (A2) irradiating the wafer with the laser light through a window provided above the wafer, wherein the laser irradiation apparatus includes: a stage that holds the wafer; a laser light source that generates the laser light; a chamber that houses the stage; a window unit that is provided in the chamber and includes the window through which the laser light passes; and a dust collector that is provided directly below the window unit and has a supply port that supplies gas toward the wafer and an exhaust port that discharges dust generated by the laser irradiation.

[0008] According to one embodiment, a method for manufacturing a compound semiconductor device includes irradiating a wafer with laser light using a laser irradiation apparatus to form a backside electrode, the method comprising: (S1) generating laser light; and (S2) irradiating the wafer with the laser light through a window provided above the wafer, wherein the laser irradiation apparatus includes: a stage for holding the wafer; a laser light source for generating the laser light; a chamber for accommodating the stage; a window unit provided in the chamber and including a window through which the laser light passes; and a dust collector provided directly below the window unit, the dust collector having a supply port for supplying gas toward the wafer and an exhaust port for discharging dust generated by the laser irradiation.

[0009] According to the embodiment, it is possible to provide a laser irradiation apparatus, a laser irradiation method, and a method for manufacturing a compound semiconductor device that can appropriately irradiate a substrate with laser light.

[0010] FIG. 1 is a side cross-sectional view schematically showing a laser irradiation device. FIG. 2 is a top view schematically showing the configuration inside a chamber of the laser irradiation device. FIG. 3 is a top view schematically showing a laser irradiation device. FIG. 4 is a schematic view for explaining an example of scanning laser light by driving a stage. FIG. 5 is a top view showing the configuration of a light shielding plate. FIG. 6 is a view for explaining the operation of a stage unit. FIG. 7 is a view for explaining the operation of a stage unit. FIG. 8 is a view showing the configuration of a dust collector. FIG. 9 is a view showing the configuration of a distribution ring. FIG. 10 is a cross-sectional view showing steps in a method for manufacturing a semiconductor device according to the present embodiment. FIG. 11 is a cross-sectional view showing steps in a method for manufacturing a semiconductor device according to the present embodiment.

[0011] The laser irradiation apparatus according to this embodiment is, for example, an excimer laser annealing apparatus (ELA apparatus) that uses excimer laser light. The ELA apparatus irradiates a substrate with laser light to form a backside electrode of a compound semiconductor. The substrate is a wafer made of a compound semiconductor. For example, a nickel film formed on a semiconductor wafer such as SiC is irradiated with the laser light. This silicides the nickel, forming an ohmic contact layer. Then, a metal electrode is formed on the nickel silicide ohmic contact layer to form a backside electrode. Hereinafter, the laser irradiation apparatus, laser irradiation method, and manufacturing method according to this embodiment will be described with reference to the drawings.

[0012] In the figures shown below, an XYZ three-dimensional Cartesian coordinate system is shown where appropriate to simplify the explanation. The Z direction is the vertical direction, which is perpendicular to the main surface of the substrate. The XY plane is a plane parallel to the main surface of the substrate. The Z direction is perpendicular to the vertical direction. In addition, when viewed from above, the Y direction is parallel to the longitudinal direction of the line beam, and the X direction is perpendicular to it.

[0013] (Overall Configuration) The configuration of the laser irradiation device according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a side cross-sectional view that schematically shows the configuration of the laser irradiation device 1. Fig. 2 is a plan view that shows the configuration inside the chamber of the laser irradiation device 1. Fig. 3 is a top view that shows the configuration of the laser irradiation device.

[0014] The laser irradiation device 1 includes a laser light source 10, an optical system 20, a slit 30, a beam damper 40, a window unit 50, a dust collector 60, displays 70 and 71, a chamber 80, and a control device 90. The chamber 80 houses a stage unit 100 and the like. The stage unit 100 has two stages 110 and 120 for holding two substrates W.

[0015] The stage 110 and the stage 120 each hold a substrate W. Each of the stages 110 and 120 is an xyz stage that drives the substrate W. Therefore, the irradiation position of the laser light on the substrate W is scanned by moving the stages 110 and 120. The detailed configuration and operation of the stage unit 100 will be described later.

[0016] The laser light source 10 is an excimer laser light source and generates a laser beam L1. The laser beam L1 is pulsed light with a center wavelength of 308 nm and a repetition rate of 300 Hz. The laser beam L1 enters an optical system 20.

[0017] The optical system 20 includes a variable attenuator 21, a beam shaping unit 22, and a projection lens 23. The variable attenuator 21 functions as a pulse adjusting unit that adjusts the pulse intensity of the laser light L1. For example, the variable attenuator 21 adjusts the pulse intensity by attenuating the laser light. Alternatively, the pulse waveform may be adjusted using a pulse stretcher that extends the pulse length. A control device 90, which will be described later, can adjust the pulse waveform and laser power of the laser light L1.

[0018] The laser light L1 from the variable attenuator 21 enters the beam shaping unit 22. The beam shaping unit 22 shapes the cross-sectional profile of the laser light L1 in a plane perpendicular to the optical axis. The beam shaping unit 22 includes a homogenizer for homogenizing the laser light L1 and a condenser lens for focusing the laser light L1. As shown in FIG. 3 , the laser light L1 forms a linear irradiation area 15 on the substrate W. The irradiation area 15 is linear, with the Y direction as the longitudinal direction and the X direction as the transverse direction. That is, the beam shaping unit 22 shapes the laser light L1 into a line beam extending along the Y direction. Furthermore, the beam shaping unit 22 may, for example, shape the profile of the laser light L1 into a flat-top distribution. The laser light L1 shaped by the beam shaping unit 22 enters the projection lens 23.

[0019] The projection lens 23 has a plurality of lenses for projecting the laser light L1 onto the substrate W. The projection lens 23 focuses the laser light L1 onto the substrate W. On the substrate W, the laser light L1 forms a linear irradiation area. The Y direction is the longitudinal direction of the irradiation area, and the X direction is the transverse direction. For example, the line length in the Y direction is 40 mm, and the beam width in the X direction is 0.5 mm. Furthermore, the laser light L1 has a flat-top distribution. Of course, the beam size is not limited to the above values. For example, the line length in the Y direction can be 10 mm or more.

[0020] A slit 30 is provided directly below the optical system 20. The laser light L1 from the projection lens 23 is incident on the slit 30. The slit 30 has an opening along the Y direction. The laser light L1 that passes through the opening of the slit 30 is incident on the window unit 50. The slit 30 may be a variable slit in order to change the beam size.

[0021] A beam damper 40 is provided diagonally above the slit 30. The laser light L1 blocked by the slit 30 is incident on the beam damper 40. That is, a portion of the laser light L1 reflected by the slit 30 is absorbed by the beam damper 40. The beam damper 40 may be provided with a cooling pipe or the like for circulating cooling water.

[0022] The laser light L1 from the slit 30 is incident on the window unit 50. The window unit 50 is attached to the top of the chamber 80. In other words, the window unit 50 is disposed outside the chamber 80. The window unit 50 includes a transparent window, a holder for holding the window, and the like. The laser light L1 passes through the window of the window unit 50 and propagates within the chamber 80. The window unit 50 is provided so as to be replaceable for maintenance purposes. The configuration of the window unit 50 will be described later.

[0023] A dust collector 60 is disposed directly below the window unit 50. The dust collector 60 is installed in the chamber 80. The dust collector 60 collects dust generated by laser irradiation. An air supply pipe 61 and an exhaust pipe 62 are connected to the dust collector 60. The configuration of the dust collector 60 will be described later. The laser light L1 that has passed through the dust collector 60 is incident on the substrate W.

[0024] The substrate W is placed on stages 110 and 120. The stages 110 and 120 are, for example, chuck stages that suction the substrate W. For example, suction holes or the like are provided on the surfaces of the stages 110 and 120 for vacuum suctioning the substrate W. Furthermore, the stages 110 and 120 are three-dimensional drive stages that can move in the x, y, and z directions.

[0025] For this purpose, the stage 110 is equipped with an X drive mechanism 111X, a Y drive mechanism 111Y, and a Z drive mechanism 111Z. Similarly, the stage 120 is equipped with an X drive mechanism 121X, a Y drive mechanism 121Y, and a Z drive mechanism 121Z. The stages 110 and 120 drive the substrate W, thereby moving the position of the laser light L1 relative to the substrate W. The stages 110 and 120 move the substrate W in the x and y directions, thereby scanning the substrate W with the laser light L1. As a result, the entire surface of the substrate W is irradiated with the laser light L1. The Z drive mechanisms 111Z and 121Z perform lifting and lowering operations to load and unload the substrate W. Since the operation and configuration of the stage 110 and the stage 120 are similar, the following description will mainly focus on the stage 110.

[0026] The stage 110 is provided with a power monitor 117 and a beam profiler 118. The power monitor 117 and the beam profiler 118 move together with the stage 110. The stage 120 is provided with a power monitor 127 and a beam profiler 128. The power monitor 127 and the beam profiler 128 move together with the stage 120.

[0027] The power monitors 117 and 127 are photodetectors that measure the power of the laser beam. Slit light-blocking plates 117a and 127a are provided on the incident sides of the power monitors 117 and 127. The slit light-blocking plates 117a and 127a have elongated openings with the Y direction as their longitudinal direction. The power monitor 117 detects the laser beam L1 that has passed through the slit light-blocking plate 117a. The power monitor 127 detects the laser beam L1 that has passed through the slit light-blocking plate 127a. This detects the power of the pulsed laser beam. The power monitors 117 and 127 can be used to monitor for dirt on the windows.

[0028] The beam profilers 118, 128 are photodetectors having multiple pixels and detect the beam profile of the laser light. The beam profilers 118, 128 measure the beam size and spatial distribution of the laser light. As described above, the stages 110, 120 are provided with power monitors 117, 127 and beam profilers 118, 128. The power monitors 117, 127 and beam profilers 118, 128 detect the laser light L1 and output detection signals indicating the detection results to the control device 90. The beam profilers 118, 128 can be used to monitor the contamination of the window.

[0029] The control device 90 performs feedback control of the laser light source 10, the variable attenuator 21, or the beam shaping unit 22 based on the detection results. In this way, the laser light L1 can be adjusted to a power and profile suitable for the irradiation process. For example, if the laser light intensity becomes low, the control device 90 controls the laser light source 10 or the variable attenuator 21 to increase the laser light intensity. This makes it possible to irradiate the laser light with an appropriate intensity. In addition, the displays 70 and 71 may display the detection results such as the beam profile and laser power.

[0030] (Stage Driving) The scanning of the laser light L1 by driving the stages 110 and 120 will be described with reference to FIG. 4. FIG. 4 is an XY plan view for explaining an example of scanning the laser light L1. As described above, the laser light L1 forms a linear irradiation area with the Y direction as the longitudinal direction. The line length in the Y direction is 40 mm, and the beam width in the X direction is 0.5 mm. In addition, although the substrate W is circular in the figure, an orientation flat or a notch may be formed.

[0031] Here, the stage 110 moves in a zigzag pattern in the X and Y directions, thereby irradiating the entire surface of the substrate W with the laser light L1. That is, the stage 110 moves in the X direction while the substrate W is being irradiated with the line-shaped laser light L1 whose longitudinal direction is in the Y direction. When the laser light L1 is scanned from one end of the substrate W to the other, a strip-shaped region extending in the X direction (e.g., region 15a) is irradiated with the laser light L1. Then, the stage 110 moves in the Y direction, thereby shifting the irradiation region 15 on the substrate W in the Y direction. The stage 110 repeatedly moves in the X and Y directions, thereby irradiating the entire surface of the substrate W with the laser light.

[0032] In the Y direction, while the laser beam L1 is irradiating the irradiation position 15-1, the stage 110 moves the substrate W in the -X direction. When the laser beam L1 scans from one end of the substrate W to the other, scanning of one line is completed. When scanning of the first line is completed, a belt-shaped region 15a becomes the irradiated region. Note that approximately half of the belt-shaped region 15a extends beyond the substrate W in the Y direction.

[0033] Next, the stage 110 moves in the +Y direction at the other end of the substrate W. Here, the stage 110 moves in the +Y direction by half the pitch of the line length. As a result, the laser light L1 is irradiated onto the substrate W at the irradiation position 15-2 in the Y direction. With the laser light L1 irradiated onto the irradiation position 15-2, the stage 110 moves the substrate W in the +X direction. When the laser light L1 scans from the other end to the one end of the substrate W, scanning of one line is completed. When scanning of the second line is completed, the band-shaped region 15b becomes the irradiated region.

[0034] At the other end of the substrate W, the stage 110 moves in the +Y direction. Here, the stage 110 moves in the +Y direction by half the pitch of the line length. As a result, the laser beam L1 is irradiated onto the substrate W at irradiation position 15-3 in the Y direction. When the stage 110 moves the substrate W in the -X direction while irradiation position 15-2 is being irradiated, the band-shaped region 15c becomes the irradiated region. In this way, the stage 110 repeatedly moves in the X and Y directions.

[0035] Then, in the Y direction, the laser beam L1 is irradiated onto the substrate W at the irradiation position 15-11. With the irradiation position 15-11 being irradiated, the stage 110 moves the substrate W in the +X direction. When the laser beam L1 has scanned from one end of the substrate W to the other end, scanning of the final line is completed. When scanning of the final line is completed, a band-shaped region 15k becomes the irradiated region. Note that, in the Y direction, approximately half of the band-shaped region 15k extends beyond the substrate W. In this case, the substrate W is an 8-inch wafer with a line length of 40 mm, and therefore the stage 110 scans 11 lines.

[0036] Here, the stage 110 moves in the Y direction so that adjacent irradiation positions overlap. Specifically, the stage 110 moves in the Y direction so that approximately half of the line length overlaps. Furthermore, because the laser light L1 is a pulsed laser light, the stage 110 moves in the X direction so that the pulsed laser light also overlaps. Specifically, the movement speed of the stage 110 in the X direction is determined by the repetition frequency and line width of the pulsed laser light. Here, the movement speed of the stage 110 is set so that approximately 80% of the irradiation area overlaps between two consecutive pulses in the X direction. Of course, the line length, line width, scanning speed, overlap amount, etc. of the laser light are not limited to the above values.

[0037] As shown in Fig. 1, the stage 110 is equipped with an X drive mechanism 111X and a Y drive mechanism 111Y. The stage 120 is equipped with an X drive mechanism 121X and a Y drive mechanism 121Y. The X drive mechanisms 111X and 121X move the substrate W back and forth in the X direction so that the laser light L1 scans the substrate W. The Y drive mechanisms 111Y and 121Y move the substrate W in the line direction of the laser light L1. The laser light L1 scans the substrate W so that part of the irradiation area of ​​adjacent scan lines overlaps. In this way, the substrate W can be uniformly irradiated with the laser light L1.

[0038] (Light Shielding Plate) Furthermore, the stages 110 and 120 are provided with light shielding plates 116 and 126, respectively. The substrate W is placed below the light shielding plates 116 and 126. The light shielding plates 116 and 126 cover the peripheral edge of the substrate W. The light shielding plate 116 is attached to the stage 110 via a mount 115. Furthermore, the light shielding plate 126 is attached to the stage 120 via a mount 125.

[0039] The light-shielding plates 116 and 126 are made of a material that absorbs or reflects the laser light L1. The light-shielding plates 116 and 126 are made of a metal multilayer reflective film or the like so as to reflect UV light with a wavelength of 308 nm. The mounts 115 and 125 are made of ceramic or the like. The mounts 115 and 125 are frames for fixing the light-shielding plates 116 and 126.

[0040] 4, the laser light L1 is a line beam, and is therefore also irradiated onto areas outside the substrate W. The light shielding plate 116 is disposed above the substrate W, and covers the peripheral edge and the outside of the substrate W. By providing the light shielding plate 116, it is possible to prevent the laser light L1 from being irradiated onto the upper surface of the stage 110. This makes it possible to prevent damage to the stage 110.

[0041] 5 is a top view showing the configuration of the light-shielding plate 116. The light-shielding plate 116 has an opening 116a through which the laser light L1 passes. Therefore, the laser light L1 passes through the opening 116a and is irradiated onto the substrate W. The opening 116a has a circular shape that is slightly smaller than the outer diameter of the substrate W. Therefore, the peripheral edge of the substrate W is covered by the light-shielding plate 116.

[0042] 1, alignment cameras 119, 129 are installed above the stages 110, 120. For example, the cameras 119, 129 are disposed directly above the stages 110, 120 at the positions where the substrate W is loaded. The cameras 119, 129 are attached to the chamber 80, for example. As shown in FIG. 5, the field of view 119a of the camera 119 includes the edge portion of the substrate W. The field of view 119a also includes the boundary between the light shielding plate 116 and the opening 116a. When the substrate W is loaded, the camera 119 captures an image of the substrate W and the light shielding plate 116, thereby enabling the position of the substrate W relative to the light shielding plate 116 to be detected. This makes it possible to prevent misalignment during loading.

[0043] The light-shielding plate 116 is preferably made of a material that transmits visible light. That is, the light-shielding plate 116 is made of a material that has high reflectivity for the laser wavelength of the laser light L1 and high transmittance for visible light. This allows the camera 119 to capture an image of the edge of the substrate W through the light-shielding plate 116. The camera 119 may be fixed to the chamber 80 so that it is positioned above the light-shielding plate 116 at the substrate W loading position.

[0044] The camera 119 outputs the captured image to the control device 90. The control device 90 can measure the relative positional relationship between the light shielding plate 116 and the substrate W. For example, the control device 90 controls the loading position of the substrate W based on the captured image of the camera 119. This allows a substrate loading robot or the like to load the substrate W to an appropriate position on the stage 110.

[0045] In this way, the cameras 119, 129 detect the relative position of the substrate W with respect to the light-shielding plate 116. The stages 110, 120 align the substrate W based on the detection result of the camera 119. For example, the loading position may be adjusted by the X drive mechanisms 111X, 121X and the Y drive mechanisms 111Y, 121Y. Alternatively, the stages 110, 120 may be provided with alignment mechanisms for fine adjustment separate from the X drive mechanisms 111X, 121X and the Y drive mechanisms 111Y, 121Y. The displays 70, 71 may display the results of imaging by the cameras.

[0046] (Stage unit 100) Furthermore, in this embodiment, in order to efficiently irradiate the substrate W with laser light, the stage unit 100 is provided with two stages 110, 120. While the substrate W is being irradiated with the laser light L1 on one stage 110, the substrate W is loaded and unloaded on the other stage. In this way, it is possible to reduce the waiting time for loading and unloading the substrate W. Therefore, it is possible to shorten the takt time and improve productivity.

[0047] The operation of the stages 110 and 120 will be described in detail with reference to Figures 6 and 7. Figures 6 and 7 are diagrams for explaining the operation of the twin stage. Note that Figures 6 and 7 are schematic top views of the stages 110 and 120, and the configuration has been appropriately simplified. For example, the window unit 50 and the like have been omitted. In Figures 6 and 7, the substrates W placed on the stage 110 are referred to as substrates W1 and W3, and the substrates W placed on the stage 120 are referred to as substrates W2 and W4.

[0048] The substrate W1 is the first substrate to be irradiated with the laser by the stage 110, and the substrate W3 is the next substrate to be irradiated with the laser by the stage 110. The substrate W2 is the first substrate to be irradiated with the laser by the stage 120, and the substrate W3 is the next substrate to be irradiated with the laser by the stage 120. The laser irradiation process is carried out on the substrates W1, W2, W3, and W4 in this order.

[0049] The substrate W1 is loaded onto the stage 110 (step 1). For example, the Z drive mechanism 111Z of the stage 110 raises and lowers the mounting surface of the stage 110, thereby allowing the substrate W1 to be received from a substrate loading robot. Here, the stages 110 and 120 are at substrate loading / unloading positions. Here, the loading and unloading positions are described as being the same, but they may be different. The loading and unloading positions are shifted in the Y direction from the irradiation area 15. Specifically, the loading and unloading position of the stage 110 is on the -Y side of the irradiation area 15. The loading and unloading position of the stage 120 is on the +Y side of the irradiation area 15. Furthermore, the substrate W1 is loaded onto the stage 110 by a robot hand or the like moving the substrate W1 in the +X direction from outside the chamber 80. At this time, the camera 119 may capture an image of the edge of the substrate W1 to perform alignment.

[0050] After the substrate W1 is loaded onto the stage 110, the stage 110 is driven in the +Y direction, thereby moving the substrate W1 to the irradiation region 15 of the laser light L1 (step 2). Furthermore, in this step, the substrate W2 is loaded onto the stage 120. That is, the movement of the stage 110 and the loading of the substrate W2 are carried out in parallel. In this way, the substrate W2 is loaded onto the stage 120 while the stage 110 is moving.

[0051] Then, the stage 110 is driven in the X and Y directions, whereby the laser light L1 is irradiated onto the substrate W1 (step 3). As a result, a portion of the substrate W1 becomes the irradiated region 150. As described above, the stage 110 moves the substrate W1 in a zigzag manner. Of course, the stage 110 may scan the substrate W1 by raster scanning or the like. At this time, the stage 120 waits at the load / unload position. Then, when the scanning by the stage 110 is completed, the laser light L1 is irradiated onto almost the entire surface of the substrate W1. As a result, almost the entire surface of the substrate W1 becomes the irradiated region 150 (step 4). Furthermore, as described above, the alignment camera 129 may capture an image of the edge of the substrate W2 to perform alignment.

[0052] When the laser irradiation process for the substrate W1 is completed, the stage 110 moves in the -Y direction. The stage 110 retreats to the loading / unloading position and unloads the substrate W1 (step 5). At this time, the stage 120 is also moving in the -Y direction. Therefore, the stage 120 moves to the irradiation area 15 of the laser light L1. In this way, the unloading operation of the substrate W1 and the movement of the stage 120 are performed simultaneously.

[0053] Then, the stage 120 is driven in the X and Y directions, whereby the laser light L1 is irradiated onto the substrate W2 (step 6). As a result, a portion of the substrate W2 becomes the irradiated region 150. As described above, the stage 120 moves the substrate W2 in a zigzag manner. Of course, the stage 120 may scan the substrate W2 by raster scanning or the like. At this time, the stage 110 is in the loading / unloading position, and the loading operation of the next substrate W3 is performed. When the scanning by the stage 120 is completed, the laser light L1 is irradiated onto almost the entire surface of the substrate W2 (step 7). As a result, almost the entire surface of the substrate W2 becomes the irradiated region 150. Alternatively, the camera 119 may capture an image of the edge of the substrate W3 to perform alignment.

[0054] When the laser irradiation process for substrate W2 is completed, the stage 120 moves in the +Y direction. That is, the stage 120 retreats to the loading / unloading position and unloads the substrate W2 (step 8). At this time, the stage 110 is moving in the +Y direction. Therefore, the stage 110 moves to the irradiation area 15 of the laser light L1. In this way, the unloading operation of the substrate W2 and the movement of the stage 110 are performed simultaneously.

[0055] Then, the stage 110 is driven in the X and Y directions, whereby the laser light L1 is irradiated onto the substrate W3 (step 9). As a result, a portion of the substrate W3 becomes the irradiated region 150. As described above, the stage 110 moves the substrate W1 in a zigzag manner. At this time, the stage 120 is at the loading / unloading position, and the next substrate W4 has been loaded. In this way, the loading operation of the substrate W4 and the movement of the stage 110 are performed simultaneously.

[0056] In this way, the control device 90 controls the stage unit 100 so that the stage 110 and the stage 120 alternately perform the laser irradiation process. While one of the stages 110 and 120 is performing a loading / unloading operation, the other of the stages 110 and 120 moves. For example, while substrate W3 is being loaded onto the stage 110 or while substrate W1 is being unloaded, the stage 120 is driven to irradiate substrate W2 with laser light. Also, while substrate W4 is being loaded onto the stage 120 or while substrate W2 is being unloaded, the stage 110 is driven to irradiate substrate W3 with laser light L1. In this way, waiting time can be shortened, thereby improving productivity.

[0057] (Guide Mechanism Cover) The stages 110 and 120 are xyz-driven stages. Therefore, the stages 110 and 120 slide in the x and y directions, thereby moving the substrate W. Dust generated when the stages 110 and 120 slide may affect the laser irradiation process. If the laser irradiation process is performed with dust attached to the substrate W or the window of the window unit, part of the laser light may be absorbed or reflected by the dust. In this case, there is a risk that proper alloying (silicidation) may not be achieved. Therefore, in this embodiment, a cover is provided on the guide mechanism to suppress dust.

[0058] 1, for example, Y drive mechanisms 111Y, 121Y have guide mechanisms 132. Guide mechanisms 132 are, for example, guide rails or the like, and are provided along the Y direction. Guide mechanisms 132 guide the movement of stages 110, 120 in the Y direction. Movable parts of Y drive mechanisms 111Y, 121Y move along guide mechanisms 132. Guide mechanisms 132 are covered with covers 130. Covers 130 have, for example, an expandable bellows structure.

[0059] For example, one end of the cover 130 is attached to an end of the guide mechanism 132, and the other end is attached to a movable part. Therefore, the cover 130 expands and contracts with the movement of the movable part. Dust generated by sliding between the guide mechanism 132 and the movable parts of the Y drive mechanisms 111Y and 121Y can be prevented from floating inside the chamber 80. This prevents dust from adhering to the surface of the substrate W.

[0060] Similarly, X drive mechanisms 111X and 121X have guide mechanisms 133. Guide mechanisms 133 guide the movement of stages 110 and 120 in the X direction. Guide mechanisms 133 are covered by cover 135. Guide mechanisms 133 are, for example, guide rails and are provided along the X direction. Cover 135 has, for example, an expandable bellows structure.

[0061] For example, one end of the cover 135 is attached to the guide mechanism 132, and the other end is attached to the movable part. Therefore, the cover 130 expands and contracts in response to the driving of the X drive mechanisms 111X, 121X. This prevents dust generated by sliding between the guide mechanism 133 and the movable parts of the X drive mechanisms 111X, 121X from floating inside the chamber 80. This prevents dust from adhering to the surface of the substrate W.

[0062] As described above, the laser irradiation device 1 is provided with the covers 130 and 135. Since the covers 130 and 135 cover the guide mechanisms 132 and 133, scattering of dust can be prevented, and the laser irradiation process can be stably carried out.

[0063] (Window Unit 50) The window unit 50 is provided so as to be replaceable for maintenance purposes. When the window of the window unit 50 becomes dirty, the entire window unit 50 can be replaced. As shown in FIG. 3, the window unit 50 is disposed directly below the slit 30 and the optical system 20. There is not enough space directly below the optical system 20, making replacement difficult. For this reason, in this embodiment, the window unit 50 is provided so as to be movable to a replacement position.

[0064] Specifically, the window unit 50 is attached to a replacement rail 51. The replacement rail 51 is a mechanism for replacing the window unit 50. The replacement rail 51 is a guide mechanism provided along the Y direction. The replacement rail 51 extends along the Y direction and is attached to the upper surface of the chamber 80. The window unit 50 moves in the Y direction along the replacement rail 51.

[0065] The window unit 50 moves to the replacement position (the position of the window unit 50a). As a result, the window unit 50 is displaced from the position directly below the optical system 20 and the slit 30. This makes it easy to replace the window unit 50. During the laser irradiation process, a cylinder or the like presses the window unit 50 against the chamber 80. During maintenance, the cylinder's pressing force is released.

[0066] In this way, the window unit 50 moves in the Y direction along the replacement rails 51. Therefore, the window unit 50 can be retracted from the position directly below the optical system 20. Since a work space for replacement can be secured, the worker can efficiently perform the replacement work. This reduces the maintenance time, thereby improving productivity.

[0067] (Dust Collector) If dust is generated in the chamber 80, it may affect the laser irradiation process. For example, laser irradiation may evaporate metal materials such as a nickel film provided on the substrate W and turn into dust. If the dust adheres to the window, it will affect the laser irradiation process. To address this, in this embodiment, as shown in FIG. 2 and other figures, a dust collector 60 is provided around the irradiation region 15. As shown in FIG. 1, the dust collector 60 is disposed directly below the window unit 50. In other words, the dust collector 60 is disposed directly above the irradiation region 15. The dust collector 60 collects dust such as metal dust generated from the substrate W by laser irradiation.

[0068] 1 and 2, an air intake pipe 61 and an exhaust pipe 62 are connected to the dust collector 60. The air intake pipe 61 and the exhaust pipe 62 are pipes that extend to the outside of the chamber 80. The air intake pipe 61 is connected to a gas cylinder or the like outside the chamber 80. Gas from the gas cylinder or the like is supplied to the dust collector 60 through the air intake pipe 61. The exhaust pipe 62 is connected to an exhaust pump or the like outside the chamber 80. Gas inside the dust collector 60 is exhausted to the outside of the chamber 80 through the exhaust pipe 62.

[0069] The configuration of the dust collector 60 will be described in detail with reference to Fig. 8. Fig. 8 shows a front view, a top view, and a cross-sectional view of the dust collector 60. Furthermore, the cross-sectional view and the front view of Fig. 8 show the dust collector 60 together with the window unit 50. The window unit 50 is disposed on top of the dust collector 60.

[0070] The dust collector 60 includes a case 601 and a conductance ring 607. The case 601 is hollow. A cylindrical space 610 is formed inside the case 601. The laser light L1 passes through the space 610 and is incident on the substrate W. An exhaust port 602 and a supply port 603 are formed on the inner peripheral side surface of the case 601. The exhaust port 602 and the supply port 603 penetrate the case 601 so as to face the space 610.

[0071] The window unit 50 has a holder 501 and a window 502. The window 502 is a transparent circular plate made of resin, glass, or the like. The laser light L1 passes through the window 502. The holder 501 holds the window 502. A space 610 is disposed directly below the window 502. The laser light L1 is irradiated onto the substrate W through the window 502 disposed above the substrate W.

[0072] In addition, joints 604 and 605 are connected to the outer peripheral side surface of the case 601. An exhaust port 602 is connected to the joint 604. The exhaust pipe 62 shown in FIG. 1 and other figures is connected to the joint 604. The exhaust pipe 62 can exhaust air from the space 610 to the outside through the exhaust port 602. In this way, the exhaust port 602 is provided for the purpose of not only exhausting dust generated by laser irradiation but also for the purpose of exhausting dust generated by laser irradiation.

[0073] The supply port 603 is connected to a joint 605. The gas supply pipe 61 shown in FIG. 1 and other figures is connected to the joint 605. The gas supply pipe 61 can supply gas from the supply port 603 to the space 610. Specifically, a clean gas such as air or nitrogen is ejected from the supply port 603 into the space 610. The supply port 603 can supply the gas toward the substrate W.

[0074] The exhaust port 602 and supply port 603 are disposed above the substrate W. The supply port 603 is disposed above the exhaust port 602. The gas ejected from the supply port 603 flows downward and is discharged from the exhaust port 602. Therefore, in the space 610, the gas flows downward, preventing the evaporated metal material from adhering to the window. In other words, the supply port 603 generates a downflow, so the evaporated metal material flows downward and is discharged from the exhaust port 602. In this manner, it is possible to prevent metal dust from adhering to the window 502, etc.

[0075] A conductance ring 607 is provided on the underside of the case 601. The conductance ring 607 is a plate arranged to face the substrate W. The conductance ring 607 is fixed to the case 601 with bolts or the like. An opening 607a is provided in the center of the conductance ring 607, through which the laser light L1 passes. The opening 607a is a slit opening having a longitudinal direction. The laser light L1 passes through the opening 607a and is irradiated onto the substrate W.

[0076] Furthermore, the conductance ring 607 has a plurality of collection openings 607b to define the conductance between the substrate W and the dust collector 60. That is, the conductance can be adjusted by changing the number, size, and shape of the collection openings 607b. For example, a plurality of conductance rings 607 each having a different number, size, and shape of collection openings 607b are prepared in advance. Then, the conductance rings 607 are attached to the case 601 so as to achieve the desired conductance. This makes it possible to control the flow of gas above the substrate W.

[0077] 8, a distribution ring 510 is provided below the window 502. The configuration of the distribution ring 510 will be described in detail with reference to FIG.

[0078] FIG. 9 shows a plan view and a front view of the distribution ring 510. The distribution ring 510 is formed in an annular shape with a hollow portion 510b. The hollow portion 510b is located directly above the space 610. The distribution ring 510 is provided with a plurality of gas outlet holes 510a. The gas outlet holes 510a are formed on the inner circumferential side of the distribution ring 510. The gas outlet holes 510a may also be provided on the upper surface side (window side) of the distribution ring 510. The gas outlet holes 510a are arranged along the circumferential direction. The plurality of gas outlet holes 510a are connected inside the distribution ring 510.

[0079] The distribution ring 510 is also connected to the gas supply pipe 61. Therefore, gas is ejected from the gas ejection holes 510a. The gas ejected from the gas ejection holes 510a flows into the space 610 through the hollow portion 510b.

[0080] The gas ejected from the distribution ring 510 creates a downflow in the space 610. This prevents the evaporated metal from adhering to the window 502.

[0081] It should be noted that the laser irradiation apparatus does not necessarily have all of the above-described components. That is, some components of the laser irradiation apparatus 1 may be omitted. For example, a laser irradiation apparatus according to one aspect of the present embodiment includes a stage for holding a wafer, a laser light source for generating the laser light, a chamber for accommodating the stage, a window unit provided in the chamber and including a window through which the laser light passes, and a dust collector provided directly below the window unit, the dust collector having a supply port for supplying gas toward the wafer and an exhaust port for discharging dust generated by laser irradiation. Each of the above-described components may be added to this laser irradiation apparatus.

[0082] A laser irradiation method according to another aspect of the present embodiment includes the following steps (A1) to (A2): A laser irradiation method using a laser irradiation apparatus that irradiates a wafer with laser light to form a backside electrode of a compound semiconductor device, the method including: (A1) generating laser light; and (A2) irradiating the wafer with the laser light through a window provided above the wafer. The laser irradiation apparatus includes: a stage that holds the wafer; a laser light source that generates laser light; a chamber that houses the stage; a window unit that is provided in the chamber and includes the window through which the laser light passes; and a dust collector that is provided directly below the window unit and has a supply port that supplies gas toward the wafer and an exhaust port that discharges dust generated by laser irradiation. Processing according to each of the above configurations may be added to this laser irradiation method.

[0083] The above-described laser irradiation method is applicable to a method for manufacturing a compound semiconductor device. The laser irradiation apparatus 1 is used in a process for forming a back electrode of a semiconductor device. For example, the laser irradiation apparatus 1 irradiates a wafer made of a compound semiconductor with laser light. This allows the back electrode of the semiconductor device formed on the wafer to be formed.

[0084] A method for manufacturing a compound semiconductor device will be described with reference to Figures 10 and 11. Figure 10 is a cross-sectional view showing the manufacturing process. Figures 10 and 11 schematically show the configuration in the laser irradiation process.

[0085] The substrate W includes a metal film 301, a wafer 302, a semiconductor device 303, an adhesive 304, and a glass substrate 305. The wafer 302 is a semiconductor wafer made of a compound semiconductor such as silicon carbide (SiC). The wafer 302 has semiconductor devices 303 such as transistors. The semiconductor devices 303 are SiC power devices. A metal film 301 is formed on the back surface of the wafer 302. Furthermore, after the devices are formed, the wafer 302 may be thinned by grinding, polishing, or the like.

[0086] A glass substrate 305 is attached to the front side of the wafer 302 via an adhesive 304. The metal film 301 is, for example, a nickel film. Of course, the metal film 301 may be formed of molybdenum (Mo), titanium (Ti), or tungsten (W) in addition to nickel (Ni). The metal film 301 may also be an alloy film containing these metal materials.

[0087] The laser irradiation device 1 irradiates the metal film 301 with laser light L1. As a result, the metal film 301 is silicided to form an ohmic contact layer 310 (see FIG. 11 ). The ohmic contact layer 310 may be thinned by polishing, etching, or the like. Then, a metal film 311 is formed on the ohmic contact layer 310, thereby forming a back electrode 312. Since the metal film 301 is a nickel film, the ohmic contact layer 310 is a nickel silicide film. The metal film 311 may be made of titanium (Ti), aluminum (Al), silver (Ag), gold (Au), or the like, or may have a laminated structure of these materials.

[0088] In this embodiment, the laser light L1 is an excimer laser light with a wavelength of 308 nm. Therefore, the light absorption rate in nickel is higher than that of a solid-state laser with a wavelength of 532 nm. This allows for efficient annealing of the metal film 301, improving throughput. Furthermore, the pulse width of the excimer laser light can be made shorter than that of a solid-state laser with a wavelength of 532 nm. This prevents damage to the semiconductor device 303. It also prevents temperature increases in the adhesive 304 and the like. This allows for appropriate laser light irradiation, improving productivity.

[0089] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention.

[0090] REFERENCE SIGNS LIST 1 Laser irradiation device 10 Laser light source 15 Irradiation area 20 Optical system 21 Variable attenuator 22 Beam shaping unit 23 Projection lens 30 Slit 40 Beam damper 50 Window unit 60 Dust collector 61 Air supply pipe 62 Exhaust pipe 70 Display 71 Display 80 Chamber 90 Control device 100 Stage unit 110 Stage 111X X drive mechanism 111Y Y drive mechanism 111Z Z drive mechanism 115 Mount 116 Light shielding plate 117 Power monitor 117a Slit light shielding plate 118 Beam profiler 119 Camera 120 Stage 121X X drive mechanism 121Y Y drive mechanism 121Z Z drive mechanism 125 Mount 126 Light shielding plate 127 Power monitor 127a Slit light shielding plate 128 Beam profiler 129 Camera 130 Cover 132 Guide mechanism 133 Guide mechanism 135 Cover 301 Metal film 302 Wafer 303 Semiconductor device 304 Adhesive 305 Glass substrate 310 Ohmic contact layer 311 Metal film 312 Back electrode 501 Holder 502 Window 510 Distribution ring 510a Gas outlet 510b Hollow portion 601 Case 602 Exhaust port 603 Supply port 604 Joint 605 Joint 607 Conductance ring 610 Space

Claims

1. A laser irradiation apparatus that irradiates laser light to form a back electrode of a semiconductor device formed on a wafer made of a compound semiconductor, comprising: a stage for holding the wafer; a laser light source for generating the laser light; a chamber for accommodating the stage; a window unit provided in the chamber and including a window through which the laser light passes; and a dust collector provided directly below the window unit, the dust collector having a supply port for supplying gas toward the wafer and an exhaust port for discharging dust generated by laser irradiation.

2. A laser irradiation device as described in claim 1, wherein the window unit further comprises a distribution ring arranged above the supply port, and the distribution ring has a plurality of gas outlet holes on its inner circumference side and on its window side.

3. A laser irradiation device as described in claim 1 or 2, further comprising a conductance ring on the underside of the dust collector that defines the conductance between the dust collector and the wafer, and the laser light passes through an opening in the center of the conductance ring to irradiate the wafer.

4. A laser irradiation device as described in claim 3, wherein the opening of the conductance ring is a slit opening having a longitudinal direction, and the laser light shaped into a line passes through the slit opening and is irradiated onto the wafer.

5. A laser irradiation device according to claim 1 or 2, wherein the chamber is provided with a window exchange mechanism for guiding the movement of the window unit.

6. The laser irradiation device according to claim 1 or 2, wherein the laser light scans the wafer by moving a stage that holds the wafer.

7. A laser irradiation method for irradiating laser light using a laser irradiation apparatus in order to form a back electrode of a semiconductor device formed on a wafer made of a compound semiconductor, comprising: (A1) a step of generating laser light; and (A2) a step of irradiating the wafer with the laser light through a window provided above the wafer, wherein the laser irradiation apparatus comprises: a stage for holding the wafer; a laser light source for generating laser light; a chamber for accommodating the stage; a window unit provided in the chamber and including the window through which the laser light passes; and a dust collector provided directly below the window unit, the dust collector having a supply port for supplying gas toward the wafer and an exhaust port for discharging dust generated by laser irradiation.

8. A laser irradiation method as described in claim 7, wherein the window unit further comprises a distribution ring arranged above the supply port, and the distribution ring has a plurality of gas outlet holes on its inner circumference side and on its window side.

9. A laser irradiation method as described in claim 7 or 8, further comprising a conductance ring on the underside of the dust collector that defines the conductance between the dust collector and the wafer, and the laser light passes through an opening in the center of the conductance ring to irradiate the wafer.

10. A laser irradiation method as described in claim 9, wherein the opening of the conductance ring is a slit opening having a longitudinal direction, and the laser light shaped into a line passes through the slit opening and is irradiated onto the wafer.

11. The laser irradiation method according to claim 7 or 8, wherein the chamber is provided with a window exchange mechanism for guiding the movement of the window unit.

12. A laser irradiation method according to claim 7 or 8, wherein in step (A2), the stage holding the wafer is moved so that the laser light scans the wafer.

13. A method for manufacturing a compound semiconductor device in which laser light is irradiated using a laser irradiation apparatus in order to form a back electrode of a semiconductor device formed on a wafer made of a compound semiconductor, comprising: (S1) a step of generating laser light; and (S2) a step of irradiating the wafer with the laser light through a window provided above the wafer, wherein the laser irradiation apparatus comprises: a stage for holding the wafer; a laser light source for generating laser light; a chamber for accommodating the stage; a window unit provided in the chamber and including a window through which the laser light passes; and a dust collector provided directly below the window unit, the dust collector having a supply port for supplying gas toward the wafer and an exhaust port for discharging dust generated by laser irradiation.

14. The method for manufacturing a compound semiconductor device as described in claim 13, wherein the window unit further comprises a distribution ring arranged above the supply port, and the distribution ring has a plurality of gas outlet holes on its inner circumference side and on its window side.

15. A method for manufacturing a compound semiconductor device as described in claim 13 or 14, further comprising a conductance ring on the underside of the dust collector that defines the conductance between the dust collector and the wafer, and the laser light passes through an opening in the center of the conductance ring to irradiate the wafer.

16. A method for manufacturing a compound semiconductor device as described in claim 15, wherein the opening of the conductance ring is a slit opening having a longitudinal direction, and the laser light shaped into a line passes through the slit opening and is irradiated onto the wafer.

17. The method for manufacturing a compound semiconductor device according to claim 13 or 14, wherein the chamber is provided with a window replacement mechanism for guiding the movement of the window unit.

18. A method for manufacturing a compound semiconductor device according to claim 13 or 14, wherein in the step (S2), a stage holding the wafer is moved so that the laser light scans the wafer.