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

Abstract

This laser irradiation device comprises: a light source that generates laser light; a stage that holds a semiconductor wafer; an optical system that shapes the laser light into a line beam having a long axis along a first direction and irradiates the semiconductor wafer with the line beam; a variable slit; a slit drive mechanism that drives the variable slit so as to change the size of an irradiation region of the line beam; a stage drive mechanism that drives the stage so as to change an irradiation position of the line beam with respect to the semiconductor wafer; a sensor provided for detecting a position of the stage in a second direction; and a controller that controls the slit drive mechanism on the basis of the position of the stage.

Description

Laser irradiation apparatus, laser irradiation method, and method for manufacturing semiconductor devices

[0001] The present invention relates to a laser irradiation apparatus, a laser irradiation method, and a method for manufacturing semiconductor devices.

[0002] Patent Document 1 discloses a laser annealing apparatus using an excimer laser. In Patent Document 1, a levitation unit levitates the substrate, and a transport unit transports the substrate. A line of laser light is then irradiated onto the substrate as it is being transported. Furthermore, this laser irradiation apparatus has a line sensor mounted on the substrate. The line sensor images the substrate as it is being transported.

[0003] Japanese Patent Publication No. 2018-64048

[0004] In such devices, it is desirable to perform the laser irradiation process with high productivity.

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

[0006] According to one embodiment, the laser irradiation device includes a light source that generates laser light, a stage that holds a semiconductor wafer, an optical system that shapes the laser light into a line beam having a long axis along a first direction and irradiates the semiconductor wafer with it, a variable slit disposed in the optical path of the laser light, a slit driving mechanism that drives the variable slit to change the size of the irradiation area of ​​the line beam in the first direction on the semiconductor wafer, a stage driving mechanism that drives the stage in a second direction tilted from the first direction in a top view to change the irradiation position of the line beam on the semiconductor wafer, a sensor provided to detect the position of the stage in the second direction, and a controller that controls the slit driving mechanism based on the position of the stage detected by the sensor.

[0007] According to one embodiment, the laser irradiation method is a laser irradiation method using a laser irradiation device for irradiating a semiconductor wafer with laser light, comprising: (A1) the step of generating laser light; (A2) the step of irradiating the semiconductor wafer on a stage with the laser light as a line beam having a long axis along a first direction; and (A3) the step of a stage driving mechanism driving the stage in a second direction tilted from the first direction in a top view so as to change the irradiation position of the line beam on the semiconductor wafer, wherein the laser irradiation device comprises a variable slit disposed in the optical path of the laser light; a slit driving mechanism for driving the variable slit so as to change the size of the irradiation area of ​​the line beam in the first direction on the semiconductor wafer; a sensor provided for detecting the position of the stage in the second direction; and a controller for controlling the slit driving mechanism based on the position of the stage detected by the sensor.

[0008] According to one embodiment, a method for manufacturing a semiconductor device is a method for manufacturing a semiconductor device in which a laser beam is irradiated onto a semiconductor wafer using a laser irradiation device, comprising: (S1) the step of generating laser light; (S2) the step of irradiating the semiconductor wafer on a stage with the laser light as a line beam having a long axis along a first direction; and (S3) the step of driving the stage in a second direction tilted from the first direction in a top view so as to change the irradiation position of the line beam on the semiconductor wafer. The laser irradiation device comprises a variable slit disposed in the optical path of the laser light; a slit driving mechanism that drives the variable slit to change the size of the irradiation area of ​​the line beam in the first direction on the semiconductor wafer; a sensor provided for detecting the position of the stage in the second direction; and a controller that controls the slit driving mechanism based on the position of the stage detected by the sensor.

[0009] According to the above embodiment, the laser irradiation process can be executed with high productivity.

[0010] This is a schematic side cross-sectional view of the laser irradiation device. This is a schematic top view of the configuration inside the chamber of the laser irradiation device. This is a schematic top view of the laser irradiation device. This is a schematic XZ cross-sectional view of the slit 30 and its surrounding configuration. This is a perspective view for explaining the operation of the stage and the slit. This is a perspective view for explaining the operation of the stage and the slit. This is a perspective view for explaining the operation of the stage and the slit. This is a perspective view for explaining the operation of the stage and the slit. This is a perspective view for explaining the operation of the stage and the slit. This is a process cross-sectional view showing the manufacturing method of a semiconductor device according to this embodiment. This is a process cross-sectional view showing the manufacturing method of a semiconductor device according to this embodiment.

[0011] The laser irradiation apparatus according to this embodiment is, for example, an excimer laser annealing apparatus (ELA apparatus) using excimer laser light. The ELA apparatus irradiates a substrate with laser light to form a back electrode of a compound semiconductor. The substrate is a semiconductor wafer made of silicon or a compound semiconductor. For example, a nickel film formed on a semiconductor wafer such as SiC is irradiated. As a result, the nickel silicides and an ohmic contact layer is formed. Then, a metal electrode is formed on the ohmic contact layer of nickel silicide to form a back electrode. Alternatively, the ELA apparatus may be an annealing apparatus for crystallizing an amorphous silicon film into polycrystalline silicon. The laser irradiation apparatus, laser irradiation method, and manufacturing method according to this embodiment will be described below with reference to the drawings.

[0012] For the sake of simplicity, the following diagrams use a three-dimensional XYZ Cartesian coordinate system where appropriate. The Z direction is the vertical up-and-down direction and 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 the top view, 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 using Figure 1. Figure 1 is a schematic side cross-sectional view showing the configuration of the laser irradiation device 1. Figure 2 is a plan view showing the configuration inside the chamber of the laser irradiation device 1. Figure 3 is a top view showing the configuration of the laser irradiation device.

[0014] The laser irradiation device 1 comprises a laser light source 10, an optical system 20, a slit 30, a beam damper 40, a window unit 50, a seal box 60, display units 70 and 71, a chamber 80, and a control device 90. The chamber 80 houses a stage unit 100, etc. The stage unit 100 has two stages 110 and 120 for holding two substrates W.

[0015] Stages 110 and 120 each hold the substrate W. Each of the stages 110 and 120 is an xyz stage that drives the substrate W. Therefore, as stages 110 and 120 move, the irradiation position of the laser beam on the substrate W is scanned. The detailed configuration and operation of the stage unit 100 will be described later. In Figure 1, the stage unit 100 has two stages 110 and 120, but the stage unit 100 only needs to have one or more stages.

[0016] The laser light source 10 is an excimer laser light source that generates laser light L1. Here, the laser light L1 is pulsed light with a central wavelength of 308 nm and a repetition frequency of 300 Hz. The laser light L1 is incident on the 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 adjustment 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. The control device 90, which will be described later, can adjust the pulse waveform and laser power of the laser light L1.

[0018] The laser beam L1 from the variable attenuator 21 is incident on the beam shaping unit 22. The beam shaping unit 22 shapes the cross-sectional profile of the laser beam L1 in a plane perpendicular to the optical axis. The beam shaping unit 22 includes a homogenizer for homogenizing the laser beam L1 and a condenser lens for focusing the laser beam L1. As shown in Figure 3, the laser beam L1 forms a line-shaped irradiation region 15 on the substrate W. The irradiation region 15 is line-shaped with the Y direction as the longitudinal direction (long axis direction) and the X direction as the short axis direction (short axis direction). In other words, the beam shaping unit 22 shapes the laser beam L1 into a line beam along the Y direction. Furthermore, the beam shaping unit 22, for example, makes the profile of the laser beam L1 a top-flat distribution. The laser beam L1 shaped by the beam shaping unit 22 is incident on the projection lens 23.

[0019] The projection lens 23 has multiple lenses for projecting laser light L1 onto the substrate W. The projection lens 23 focuses the laser light L1 onto the substrate. On the substrate W, the laser light L1 forms a line-shaped irradiation area. The irradiation area is defined with the Y direction as the longitudinal direction and the X direction as the short direction. For example, the line length in the Y direction is approximately the same as the size of the substrate W, and the beam width in the X direction is 0.5 mm. Furthermore, the laser light L1 has a top-flat distribution. Of course, the beam size is not limited to the above values.

[0020] The optical system shapes the laser beam so that the line length of the line beam is greater than or equal to the size of the substrate W. When the substrate W is a semiconductor wafer with a diameter of 300 mm, it is preferable that the line length in the Y direction be 300 mm or more. When the substrate W is a semiconductor wafer with a diameter of 200 mm, it is preferable that the line length in the Y direction be 200 mm or more.

[0021] A slit 30 is provided directly below the optical system 20. The laser beam L1 from the projection lens 23 and others is incident on the slit 30. The slit 30 has an opening aligned with the Y direction. The laser beam L1 that has passed 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.

[0022] A beam damper 40 is provided diagonally above the slit 30. The laser light L2 that is blocked by the slit 30 enters the beam damper 40. In other words, a portion of the laser light L2 reflected by the slit 30 is absorbed by the beam damper 40. The beam damper 40 may be equipped with cooling pipes for circulating cooling water.

[0023] The laser beam L1 from the slit 30 enters the window unit 50. The window unit 50 is mounted on the top of the chamber 80. In other words, the window unit 50 is located outside the chamber 80. The window unit 50 includes a transparent window and a holder for holding the window. The laser beam L1 passes through the window of the window unit 50 and propagates inside the chamber 80. The window unit 50 is designed to be replaceable for maintenance. The configuration of the window unit 50 will be described later.

[0024] A seal box 60 is located directly below the window unit 50. The seal box 60 is installed inside the chamber 80. The seal box 60 is provided to create a nitrogen gas atmosphere in the area to be irradiated with the laser. An air supply pipe 61 and an exhaust pipe 62 are connected to the seal box 60. Nitrogen gas is supplied from the air supply pipe 61. The exhaust pipe 62 discharges air and nitrogen gas to the outside in order to purge the space inside the seal box.

[0025] The substrate W is placed on stages 110 and 120. Stages 110 and 120 are, for example, chuck stages that adsorb the substrate W. For example, the surfaces of stages 110 and 120 are provided with adsorption holes for vacuum adsorption of the substrate W. Furthermore, stages 110 and 120 are three-dimensional drive stages that can move in the x, y, and z directions.

[0026] Therefore, stage 110 is equipped with an X drive mechanism 111X, a Y drive mechanism 111Y, and a Z drive mechanism 111Z. Similarly, stage 120 is equipped with an X drive mechanism 121X, a Y drive mechanism 121Y, and a Z drive mechanism 121Z. By driving the substrate W with stages 110 and 120, the position of the laser beam L1 relative to the substrate W moves. By moving the substrate W in the x and y directions with stages 110 and 120, the laser beam L1 scans the substrate W. As a result, the laser beam L1 is irradiated over the entire surface of the substrate W. The Z drive mechanisms 111Z and 121Z perform lifting and lowering operations for loading and unloading the substrate W. Since the operation and configuration of stages 110 and 120 are the same, the following description will mainly focus on stage 110.

[0027] Stage 110 is equipped with a power monitor 117 and a beam profiler 118. The power monitor 117 and beam profiler 118 move together with stage 110. Stage 120 is equipped with a power monitor 127 and a beam profiler 128. The power monitor 127 and beam profiler 128 move together with stage 120.

[0028] Power monitors 117 and 127 are photodetectors that measure the power of laser light. Slit light-shielding plates 117a and 127a are provided on the incident side of power monitors 117 and 127. Slit light-shielding plates 117a and 127a have elongated openings with the Y direction as their longitudinal direction. Power monitor 117 detects the laser light L1 that has passed through the slit light-shielding plate 117a. Power monitor 127 detects the laser light L1 that has passed through the slit light-shielding plate 127a. This allows the power of the pulsed laser light to be detected. By using power monitors 117 and 127, window contamination can be monitored.

[0029] The beam profilers 118 and 128 are photodetectors with multiple pixels that detect the beam profile of the laser light. The beam profilers 118 and 128 measure the beam size and spatial distribution of the laser light. Thus, the stages 110 and 120 are equipped with power monitors 117 and 127 and beam profilers 118 and 128. The power monitors 117 and 127 and the beam profilers 118 and 128 detect the laser light L1 and output a detection signal indicating the detection result to the control device 90. By using the beam profilers 118 and 128, window contamination can be monitored.

[0030] The control device 90 provides feedback control to 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 controls the laser light source 10 or the variable attenuator 21 to increase the laser light intensity. This allows the laser light to be irradiated at an appropriate intensity. In addition, the display units 70 and 71 may display the detection results such as the beam profile and laser power. Furthermore, the control device 90 controls the slit 30 and the stage unit 100.

[0031] 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, based on the image captured by the camera 119, the control device 90 controls the loading position of the substrate W. This allows a substrate loading robot or the like to load the substrate W to the appropriate position on the stage 110. The camera 119 only needs to be fixed to the chamber 80 so that it is positioned on the substrate W.

[0032] Stages 110 and 120 may each be provided with positioning markers or the like. Cameras 119 and 129 detect the relative position of the substrate W with respect to the markers or the like. Stages 110 and 120 align the substrate W based on the detection results from cameras 119 and 129. For example, the loading position may be adjusted using X drive mechanisms 111X, 121X and Y drive mechanisms 111Y, 121Y. Alternatively, stages 110 and 120 may be equipped with a fine-tuning alignment mechanism separate from the X drive mechanisms 111X, 121X and Y drive mechanisms 111Y, 121Y. Display units 70 and 71 may display the imaging results from the cameras.

[0033] In this embodiment, the stage unit 100 is equipped with two stages 110 and 120 in order to efficiently irradiate the substrate W with laser light. While the substrate W is being irradiated with laser light L1 on one stage 110, the substrate W is loaded and unloaded on the other stage. In this way, the waiting time for loading and unloading the substrate W can be reduced. Therefore, the cycle time can be shortened, and productivity can be improved.

[0034] (Guide mechanism cover) Stages 110 and 120 are xyz driven stages. Therefore, the substrate W moves as stages 110 and 120 slide in the x and y directions. Dust generated when stages 110 and 120 slide may affect the laser irradiation process. If the laser irradiation process is performed with dust adhering to the substrate W or the window of the window unit, some of the laser light will be absorbed or reflected by the dust. In this case, proper alloying (silicide formation) may not be possible. Therefore, in this embodiment, a cover is provided on the guide mechanism to suppress dust.

[0035] For example, as shown in FIG. 1, the Y drive mechanisms 111Y and 121Y have a guide mechanism 132. The guide mechanism 132 is, for example, a guide rail or the like and is provided along the Y direction. The guide mechanism 132 guides the movement of the stages 110 and 120 in the Y direction. The movable parts of the Y drive mechanisms 111Y and 121Y move along the guide mechanism 132. The guide mechanism 132 is covered with a cover 130. The cover 130 has, for example, a telescopic bellows structure.

[0036] For example, one end of the cover 130 is attached to the end of the guide mechanism 132, and the other end is attached to the movable part. Therefore, the cover 130 expands and contracts as the movable part moves. It is possible to prevent dust generated by the sliding of the guide mechanism 132 and the movable parts of the Y drive mechanisms 111Y and 121Y from floating in the chamber 80. Thus, it is possible to prevent dust from adhering to the surface of the substrate W.

[0037] Similarly, the X drive mechanisms 111X and 121X have a guide mechanism 133. The guide mechanism 133 guides the movement of the stages 110 and 120 in the X direction. The guide mechanism 133 is covered with a cover 135. The guide mechanism 133 is, for example, a guide rail or the like and is provided along the X direction. The cover 135 has, for example, a telescopic bellows structure.

[0038] 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 and 121X. Thus, it is possible to prevent dust generated by the sliding of the guide mechanism 133 and the movable parts of the X drive mechanisms 111X and 121X from floating in the chamber 80. Thus, it is possible to prevent dust from adhering to the surface of the substrate W

[0039] As described above, the laser irradiation apparatus 1 includes covers 130 and 135. Since the covers 130 and 135 cover the guide mechanisms 132 and 133, it is possible to prevent the scattering of dust, and it becomes possible to stably execute the laser irradiation process.

[0040] (Window Unit 50) The window unit 50 is provided to be replaceable for maintenance. When the window of the window unit 50 gets 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. Since there is not enough space directly below the optical system 20, the replacement work becomes difficult. Therefore, in the present embodiment, the window unit 50 is provided to be movable to a replacement position.

[0041] Specifically, the window unit 50 is attached to the 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.

[0042] 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. Therefore, the replacement work of the window unit 50 can be easily performed. During the laser irradiation process, a cylinder or the like presses the window unit 50 against the chamber 80. During maintenance, the pressing by the cylinder is released.

[0043] Thus, the window unit 50 moves in the Y direction along the replacement rail 51. Therefore, the window unit 50 can retreat from the position directly below the optical system 20. Since a replacement work space can be secured, an operator can efficiently perform the replacement work. As a result, the maintenance time can be shortened, and the productivity can be improved.

[0044] (Slit 30) The laser beam L1 is irradiated onto the substrate W through the slit 30. The slit 30 is a variable slit with a variable opening length in the Y direction. The control device 90 changes the opening length of the slit 30 according to the stage 110 or the position of the stage 110. This makes it possible to change the size of the irradiation area 15 in the long axis direction of the laser beam L1.

[0045] The detailed configuration of the slit 30 and its surroundings will be explained using Figure 4. Figure 4 is an XZ cross-sectional view schematically showing the configuration of the slit 30 and its surroundings. Figure 4 shows the state in which the laser beam L1 is irradiated onto the substrate W on the stage 110. In other words, the stage 110 is positioned directly below the slit 30. Also, in Figure 4, some components such as the replacement rail 51 are omitted for clarity of explanation. Furthermore, the operation and configuration of the stage 110 will be described in the following explanation, but the operation and configuration of the stage 120 will be omitted as they are the same as those of the stage 110.

[0046] A seal box 60 is provided directly above the substrate W. A window unit 50 is provided above the seal box 60. A slit 30 is provided above the window unit 50. Therefore, the slit 30 is positioned directly above the window unit 50. A projection lens 23 is provided above the slit 30. The optical axis of the laser beam L1 is tilted from the Z direction.

[0047] The laser beam L1 from the projection lens 23 enters the slit 30. The laser beam L1 that passes through the opening of the slit 30 is directed towards the substrate W. The laser beam L1 that enters outside the opening of the slit 30 is blocked. The slit 30 is a variable slit, and its size in the Y direction of the laser beam L1 is defined.

[0048] Here, the upper surface of the slit 30 is formed of a multilayer reflective mirror. Furthermore, the slit 30 is positioned at an angle around the Y axis from the XY plane. Therefore, the laser light reflected by the slit 30 is directed in both the +X and +Z directions. The detailed configuration of the slit 30 will be described later.

[0049] Furthermore, the laser light L2 reflected by the slit 30 enters the beam damper 40. The beam damper 40 absorbs the laser light L1. In addition, the beam damper 40 is cooled with cooling water. This suppresses the temperature rise caused by the heat absorbed by the laser light L1.

[0050] The laser beam L1 that passes through the opening of the slit 30 enters the window unit 50. The laser beam L1 that passes through the window unit 50 enters the seal box 60. The seal box 60 creates a nitrogen gas atmosphere in the space directly above the irradiation area 15 of the substrate W. For example, the seal box 60 is a cylindrical case through which the laser beam L1 passes. An air supply pipe 61 is connected to the side of the seal box 60.

[0051] The air supply pipe 61 supplies an inert gas, such as nitrogen gas, to the space inside the seal box 60. A gap is provided between the seal box 60 and the substrate W, and nitrogen gas is discharged through this gap. The laser irradiation device 1 irradiates the substrate W with laser light L1 while flowing nitrogen gas into the seal box 60 from the air supply pipe 61. The laser light L1 from the window unit 50 passes through the hollow portion of the seal box 60 and enters the substrate W. This allows the laser annealing process to be performed on the substrate W.

[0052] Furthermore, a portion of the laser light L1 incident on the substrate W is reflected by the substrate W. The laser light L1 reflected by the substrate W is called reflected light L3. The reflected light L3 reflected by the substrate W is incident on the beam damper 40. This makes it possible to suppress the temperature rise due to the heat absorbed by the laser light L1.

[0053] The configuration and operation of the slit 30 will be explained below using Figures 4 to 9. Figures 5 to 9 are schematic perspective views showing the configuration of the slit 30 and its surroundings. In Figures 5 to 9, the configuration of the seal box 60 and other components is omitted.

[0054] The slit 30 comprises a holder 201, a slit plate 202, a slit plate 203, a guide mechanism 205, and a sliding portion 206. The holder 201 is fixed to a chamber 80 or the like and holds the slit plate 202, the slit plate 203, the guide mechanism 205, and the sliding portion 206.

[0055] The guide mechanism 205 has a guide rail provided along the Y direction. The guide mechanism 205 holds the slide portion 206 in a slidable manner. Two slide portions 206 are attached to the guide mechanism 205. A slit plate 202 is attached to one slide portion 206, and a slit plate 203 is attached to the other slide portion 206. Therefore, the two slit plates 203 can move independently.

[0056] The slit plate 202 or slit plate 203 blocks the laser beam L1. Specifically, as shown in Figure 4, when the laser beam L1 is incident on the slit plate 202 or slit plate 203, it is reflected in the direction of the beam damper 40. The slit plate 202 is positioned on the +Y side of the slit plate 203. The slit plate 202 and the slit plate 203 move in the Y direction by a slit drive mechanism, which will be described later.

[0057] As shown in Figure 6 and other figures, the laser beam L1 passes between the slit plate 202 and the slit plate 203 and is incident on the substrate W. In other words, the slit plate 202 defines one end of the linear irradiation area 15, and the slit plate 203 defines the other end. The gap between the slit plate 202 and the slit plate 203 corresponds to the opening length of the slit 30 in the longitudinal direction. The opening length of the slit 30 corresponds to the length of the irradiation area 15 in the Y direction.

[0058] When slit plate 202 and slit plate 203 come into contact or overlap, the slit 30 closes, and the laser beam L1 no longer passes through the slit 30 (see Figures 5 and 9). As slit plate 202 and slit plate 203 move apart, the aperture length in the Y direction increases. Therefore, the size of the irradiation area 15 increases (see Figure 7). As slit plate 202 and slit plate 203 move closer together, the aperture length in the Y direction decreases. The size of the irradiation area 15 decreases.

[0059] The control device 90 shown in Figure 1 controls the slit 30 and the stage 110. The control device 90 changes the distance between the slit plate 202 and the slit plate 203 according to the X-direction position of the stage 110. In this way, it is possible to prevent the laser beam L1 from irradiating the stage 110 and other parts on the outer part of the substrate W. Therefore, it is possible to prevent damage to the stage 110 and other parts due to laser beam irradiation.

[0060] For example, in the Y direction, the length of the laser beam L1 from the projection lens 23 is greater than or equal to the length of the substrate W. In other words, when the slit plate 202 and the slit plate 203 are furthest apart, the irradiation area 15 is approximately the same length as the diameter of the substrate W. For example, the optical system shapes the laser beam so that the line length of the line beam is greater than or equal to the size of the substrate W. The laser beam L1 can be irradiated over the entire surface of the substrate W by the stage 110 scanning the substrate W once in the X direction. With this in mind, an example of the stage 110 moving the substrate W in the -X direction will be explained below using Figures 5 to 9.

[0061] As shown in Figure 5, before irradiation with the laser beam L1, the slit plates 202 and 203 are closed. Therefore, the laser beam L1 cannot pass through the slit 30. In other words, the entire laser beam L1 is blocked.

[0062] As the stage 110 moves the substrate W in the X direction, and the substrate W reaches the laser beam irradiation area 15, the slit plate 202 and the slit plate 203 separate, as shown in Figure 6, and laser beam irradiation begins. In other words, a gap is formed between the slit plate 202 and the slit plate 203, and the laser beam L1 passes through this gap. The laser beam L1 passes between the slit plate 202 and the slit plate 203 and is incident on the substrate W. In addition, both ends of the laser beam L1 in the Y direction are blocked by the slit plate 202 and the slit plate 203.

[0063] As the stage 110 moves across the substrate W, the distance between the slit plate 202 and the slit plate 203 changes. As shown in Figure 7, as the irradiation area 15 approaches the center of the substrate W, the length of the irradiation area 15 increases. Specifically, as the irradiation area 15 moves in the X direction from the edge of the substrate W towards the center, the size of the irradiation area 15 in the Y direction increases. The distance between the slit plate 202 and the slit plate 203 is widest when the irradiation area 15 passes through the center of the substrate W. At this point, the irradiation area 15 becomes the same length as the size of the substrate W in the Y direction.

[0064] Furthermore, as the stage 110 moves the substrate W in the -X direction, the slit plates 202 and 203 gradually move closer together, as shown in Figure 8. As the irradiation area 15 moves in the X direction from the center to the edge of the substrate W, the Y-direction size of the irradiation area 15 decreases. The slit plates 202 and 203 close at the moment the edge of the substrate W passes through the irradiation area 15 (see Figure 9). This prevents the laser beam L1 from passing through the slit 30. The laser beam irradiation process then ends. In this way, it is possible to prevent the laser beam L1 from entering the stage 110 or other components outside the substrate W.

[0065] As described above, when the stage 110 moves the substrate W in the X direction, the opening length of the slit 30 changes. Similarly, for the stage 120, the opening length of the slit 30 changes according to the position of the stage 120 in the X direction. Here, the control device 90 shown in Figure 1 controls the slit drive mechanism according to the position of the stage 110. In other words, the opening length of the slit changes according to the position of the stage 110 or the stage 120 in the X direction. This prevents the laser beam from irradiating the stages 110 and 120. Furthermore, the laser beam L1 can be irradiated over the entire surface of the substrate W by the stage 110 scanning the substrate W only once in the X direction. Therefore, the scanning time can be shortened, and the cycle time for processing one substrate W can be shortened. Thus, productivity can be improved.

[0066] The control system for controlling the stage 110 and the slit 30 will be explained using Figure 10. Figure 10 is a control block diagram showing the control system for controlling the stage 110 and the slit 30. The control device 90 includes a motion controller 901, an X-axis servo driver 911X, a Y-axis servo driver 911Y, a servo driver 921, a servo driver 931, and the like.

[0067] The X-axis drive mechanism 111X is equipped with an X-axis encoder 912X. The X-axis encoder 912X is a sensor for detecting the X-direction position of the stage 110. For example, the X-axis encoder 912X measures the rotation angle, rotation speed, and rotation position of the motor of the X-axis drive mechanism 111X. The Y-axis drive mechanism 111Y is equipped with a Y-axis encoder 912Y. The Y-axis encoder 912Y is a sensor for detecting the Y-direction position of the stage 110. For example, the Y-axis encoder 912Y measures the rotation angle, rotation speed, and rotation position of the motor of the Y-axis drive mechanism 111Y. The X-axis encoder 912X and the Y-axis encoder 912Y output encoder signals indicating the measurement results to the motion controller 901. The sensors for detecting the position of the stage 110 are not limited to encoders.

[0068] The motion controller 901 includes a slit position calculation unit 902, a feedback unit 903, and a feedback unit 904. The functions of the motion controller 901 may be realized by a processor executing a program. Alternatively, the functions of the motion controller 901 may be realized using hardware resources such as arithmetic circuits.

[0069] The feedback unit 903 provides feedback control to the Y-axis drive mechanism 111Y based on the encoder input from the Y-axis encoder 912Y. For example, the feedback unit 903 outputs a current command value to the Y-axis servo driver 911Y. The Y-axis servo driver 911Y drives the motor of the Y-axis drive mechanism 111Y with a current corresponding to the current command value. This drives the Y-axis drive mechanism 111Y to move the stage 110 to a predetermined position at a predetermined speed.

[0070] Similarly, the feedback unit 904 provides feedback control to the X-axis drive mechanism 111X based on the encoder input from the X-axis encoder 912X. For example, the feedback unit 904 outputs a current command value to the X-axis servo driver 911X. The X-axis servo driver 911X drives the motor of the X-axis drive mechanism 111X with a current corresponding to the current command value. This drives the X-axis drive mechanism 111X to move the stage 110 to a predetermined position at a predetermined speed. Alternatively, the camera 119 may detect the loading position of the substrate W on the stage 110 based on the imaging results. Then, position correction may be performed based on the loading position.

[0071] Here, when the laser beam is irradiated, the X-drive mechanism 111X moves the stage 110 in the X direction at a constant speed. This allows the substrate W to be transported at a constant speed. While the substrate W is being transported at a constant speed, the laser beam is irradiated with a constant pulse interval and irradiation intensity. Therefore, the substrate W can be annealed with a uniform laser irradiation intensity.

[0072] The slit position calculation unit 902 calculates the slit position based on the encoder input. The slit position calculation unit 902 can determine the X-direction position of the stage 110 based on the measurement result of the X-axis encoder 912X. Based on the X-direction position of the stage 110, the slit position calculation unit 902 calculates the target positions of the slit plate 202 and the slit plate 203. The slit position calculation unit 902 may also determine the Y-direction position of the stage 110 based on the measurement result of the Y-axis encoder 912Y.

[0073] The slit position calculation unit 902 outputs command values ​​corresponding to the target position to the servo drivers 921 and 931. Motors 922 and 932 are slit drive mechanisms that drive the slit plates 202 and 203. Servo driver 921 drives motor 922 according to the command value. Motor 922 moves slit plate 202 to the target position. Servo driver 931 drives motor 932 according to the command value. Motor 932 moves slit plate 203 to the target position. This makes it possible to control the size of the irradiation area 15 of the laser beam L1 in the Y direction.

[0074] The target position Wr of slit plate 202 and the target position Wl of slit plate 203 can be calculated by the following equations (1) and (2): Wr = + (R ２ -X ２ ) １／２ (1) Wl = -(R ２ -X ２ ) １／２ (2)

[0075] The substrate W is assumed to be a circle with radius R, and the transport direction of the substrate W is the +x direction. The position of the stage 110 where the laser beam L1 strikes the origin of the substrate W is defined as the origin (0,0). In equations (1) and (2), the target position Wr of the slit plate 202 and the target position Wl of the slit plate 203 are shown, with X being the X-direction position of the stage 110. The origin of the substrate W is the center position of the circular substrate W. Here, the slit position calculation unit 902 calculates the target positions Wr and Wl without considering the Y-direction displacement of the stage 110.

[0076] As shown in Equation (1) and Equation (2), the target position is calculated according to the position of the stage 110. By driving the motor 932 with the servo driver 921, the slit plate 202 can be moved to the target position. By driving the motor 932 with the servo driver 931, the slit plate 203 can be moved to the target position. Therefore, when the position of the stage 110 changes, the positions of the slit plate 202 and the slit plate 203 change. The motion controller 901 drives the motors 922, 932, and the X drive mechanism 111X synchronously based on the stage position detected by the X-axis encoder 912X.

[0077] In addition, the slit position calculation unit 902 may calculate the position of the slit 30 based on the Y-direction position of the stage 110 detected by the Y-axis encoder 912Y. For example, during the X-axis operation, the Y-direction position of the stage  110 may fluctuate due to the influence of disturbances or the like. Alternatively, the Y-direction position of the stage 110 may shift during the X-axis operation. In such a case, the Y-direction position of the slit 30 may be corrected according to the Y-direction position of the stage 110. For example, if the Y-direction position obtained from the Y-axis encoder 912Y is Y, the target position Wr of the slit plate 202 and the target position Wl of the slit plate 203 can be calculated by the following equations (3) and (4). Wr = Y + (R ２ - X ２ ) １／２ (3) Wl = Y - (R ２ - X ２ ) １／２ (4)

[0078] Furthermore, motors 922 and 932 drive slit plate 202 and slit plate 203 in synchronous motion. For example, motion controller 901 controls servo drivers 921 and 931 so that slit plate 202 and slit plate 203 move in opposite directions at the same speed. That is, when slit plate 202 is moving in the +Y direction, slit plate 203 moves in the -Y direction at the same speed as slit plate 202. When slit plate 202 is moving in the -Y direction, slit plate 203 moves in the +Y direction at the same speed as slit plate 202. In this way, it is possible to prevent laser light from being shone on the stage 110.

[0079] Another embodiment of this laser irradiation method is a laser irradiation method using a laser irradiation device for irradiating a semiconductor wafer with laser light, and comprises the following steps (A1) to (A3): (A1) A step of generating laser light. (A2) A step of irradiating the semiconductor wafer on a stage with the laser light as a line beam having a long axis along a first direction. (A3) A step of driving the stage in a second direction tilted from the first direction in a top view, so as to change the irradiation position of the line beam on the semiconductor wafer. The laser irradiation device comprises a variable slit arranged in the optical path of the laser light, a slit driving mechanism for driving the variable slit so as to change the size of the irradiation area of ​​the line beam in the first direction on the semiconductor wafer, a sensor provided for detecting the position of the stage in the second direction, and a controller for controlling the slit driving mechanism based on the position of the stage detected by the sensor.

[0080] The laser irradiation method described above is applicable to a method for manufacturing compound semiconductor devices. The laser irradiation apparatus 1 is used in the process of forming the back electrode of a semiconductor device. For example, the laser irradiation apparatus 1 irradiates a wafer made of compound semiconductor light with laser light. This makes it possible to form the back electrode of a semiconductor device formed on the wafer.

[0081] A method for manufacturing compound semiconductor devices will be explained using Figures 11 and 12. Figure 10 is a cross-sectional view showing the manufacturing process. Figures 11 and 12 schematically show the configuration in the laser irradiation process.

[0082] The substrate W comprises 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 a semiconductor device 303 such as a transistor. The semiconductor device 303 is a SiC power device. The metal film 301 is formed on the back surface of the wafer 302. Furthermore, after device formation, the wafer 302 may be thinned by grinding, polishing, or the like.

[0083] A glass substrate 305 is bonded 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 made of molybdenum (Mo), titanium (Ti), or tungsten (W) in addition to nickel (Ni). Alternatively, the metal film 301 may be an alloy film containing these metal materials.

[0084] The laser irradiation device 1 irradiates the metal film 301 with laser light L1. This causes the metal film 301 to silicide, forming an ohmic contact layer 310 (see Figure 12). The ohmic contact layer 310 may be thinned by polishing or etching. Then, a metal film 311 is formed on the ohmic contact layer 310, forming the 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 titanium (Ti), aluminum (Al), silver (Ag), gold (Au), etc., and may be a laminated structure of these materials.

[0085] 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 compared to a solid-state laser with a wavelength of 532 nm. Thus, the metal film 301 can be annealed efficiently, and throughput can be improved. In addition, with excimer laser light, the pulse width can be shortened compared to a solid-state laser with a wavelength of 532 nm. Therefore, damage to the semiconductor device 303 can be prevented. Temperature rise of adhesives 304 and the like can be suppressed. Thus, the laser light can be irradiated appropriately, and productivity can be improved.

[0086] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention.

[0087] This application claims priority based on Japanese Patent Application No. 2024-228426, filed on 25 December 2024, and incorporates all of its disclosures herein.

[0088] 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 Seal box 61 Air intake pipe 62 Exhaust pipe 70 Display unit 71 Display unit 80 Chamber 90 Control unit 100 Stage unit 110 Stage 111X X drive mechanism 111Y Y drive mechanism 111Z Z drive mechanism 117 Power monitor 117a Slit light shield plate 118 Beam profiler 119 Camera 120 Stage 121X X drive mechanism 121Y Y drive mechanism 121Z Z drive mechanism 127 Power monitor 127a Slit light shield plate 128 Beam profiler 129 Camera 130 Cover 132 Guide mechanism 133 Guide mechanism 135 Cover 201 Holder 202 Slit plate 203 Slit plate 205 Guide mechanism 206 Slide part 301 Metal film 302 Wafer 303 Semiconductor device 304 Adhesive 305 Glass substrate 310 Ohmic contact layer 311 Metal film 312 Back electrode 901 Motion controller 902 Slit position calculation unit 903 Feedback unit 904 Feedback unit 911X X-axis servo driver 911Y Y-axis servo driver 912X X-axis encoder 912Y Y-axis encoder 921 Servo driver 931 Servo driver 922 Motor 932 Motor

Claims

1. A laser irradiation device comprising: a light source that generates laser light; a stage that holds a semiconductor wafer; an optical system that shapes the laser light into a line beam having a long axis along a first direction and irradiates the semiconductor wafer with it; a variable slit disposed in the optical path of the laser light; a slit driving mechanism that drives the variable slit to change the size of the irradiation area of ​​the line beam in the first direction on the semiconductor wafer; a stage driving mechanism that drives the stage in a second direction tilted from the first direction in a top view to change the irradiation position of the line beam on the semiconductor wafer; a sensor provided for detecting the position of the stage in the second direction; and a controller that controls the slit driving mechanism based on the position of the stage detected by the sensor.

2. The laser irradiation apparatus according to claim 1, wherein the controller controls the slit drive mechanism and the stage drive mechanism in synchronization based on the position of the stage detected by the sensor.

3. The laser irradiation device according to claim 2, wherein the variable slit comprises a first plate that defines one end of the irradiation area in the first direction and a second plate that defines the other end, and the slit driving mechanism drives the first plate and the second plate synchronously.

4. The laser irradiation apparatus according to claim 3, wherein the optical system shapes the laser light so that the line length of the line beam is greater than or equal to the size of the semiconductor wafer, and the stage driving mechanism scans the semiconductor wafer once in a second direction so that the laser light is irradiated over the entire surface of the semiconductor wafer.

5. The laser irradiation device according to claim 4, wherein the variable slit has a multilayer mirror that reflects the laser light, and a damper is provided that absorbs the laser light reflected by the variable slit.

6. The laser irradiation device according to claim 5, further comprising a chamber having a window through which the laser light passes, wherein the variable slit is positioned directly above the window.

7. A laser irradiation method using a laser irradiation device for irradiating a semiconductor wafer with laser light, comprising: (A1) a step of generating laser light; (A2) a step of irradiating the semiconductor wafer on a stage with the laser light as a line beam having a long axis along a first direction; and (A3) a step of driving the stage in a second direction tilted from the first direction in a top view so as to change the irradiation position of the line beam on the semiconductor wafer, wherein the laser irradiation device comprises: a variable slit disposed in the optical path of the laser light; a slit driving mechanism for driving the variable slit so as to change the size of the irradiation area of ​​the line beam in the first direction on the semiconductor wafer; a sensor provided for detecting the position of the stage in the second direction; and a controller for controlling the slit driving mechanism based on the position of the stage detected by the sensor.

8. The laser irradiation method according to claim 7, wherein the controller controls the slit drive mechanism and the stage drive mechanism in synchronization based on the position of the stage detected by the sensor.

9. The laser irradiation method according to claim 8, wherein the variable slit comprises a first plate defining one end of the irradiation area in the first direction and a second plate defining the other end, and the slit driving mechanism drives the first plate and the second plate synchronously.

10. The laser irradiation method according to claim 9, wherein the laser beam is shaped such that the line length of the line beam is greater than or equal to the size of the semiconductor wafer, and the laser beam is irradiated over the entire surface of the semiconductor wafer by the stage driving mechanism scanning the semiconductor wafer once in a second direction.

11. The laser irradiation method according to claim 10, wherein the variable slit has a multilayer mirror that reflects the laser light, and a damper is provided that absorbs the laser light reflected by the variable slit.

12. The laser irradiation method according to claim 11, wherein the laser irradiation device further comprises a chamber having a window through which the laser light passes and housing the stage, and the variable slit is positioned directly above the window.

13. A method for manufacturing a semiconductor device, comprising: (S1) generating laser light on a semiconductor wafer using a laser irradiation device, (S2) irradiating the semiconductor wafer on a stage with the laser light as a line beam having a long axis along a first direction, and (S3) driving the stage in a second direction tilted from the first direction in a top view, such that the stage driving mechanism changes the irradiation position of the line beam on the semiconductor wafer, wherein the laser irradiation device comprises: a variable slit disposed in the optical path of the laser light; a slit driving mechanism that drives the variable slit to change the size of the irradiation area of ​​the line beam in the first direction on the semiconductor wafer; a sensor provided for detecting the position of the stage in the second direction; and a controller that controls the slit driving mechanism based on the position of the stage detected by the sensor.

14. The method for manufacturing a semiconductor device according to claim 13, wherein the controller controls the slit drive mechanism and the stage drive mechanism in synchronization based on the position of the stage detected by the sensor.

15. The method for manufacturing a semiconductor device according to claim 14, wherein the variable slit comprises a first plate that defines one end of the irradiation area in the first direction and a second plate that defines the other end, and the slit driving mechanism drives the first plate and the second plate synchronously.

16. The method for manufacturing a semiconductor device according to claim 15, wherein the laser beam is shaped so that the line length of the line beam is greater than or equal to the size of the semiconductor wafer, and the laser beam is irradiated over the entire surface of the semiconductor wafer by the stage driving mechanism scanning the semiconductor wafer once in a second direction.

17. The method for manufacturing a semiconductor device according to claim 16, wherein the variable slit has a multilayer mirror that reflects the laser light, and a damper is provided that absorbs the laser light reflected by the variable slit.

18. The method for manufacturing a semiconductor device according to claim 17, wherein the laser irradiation device further comprises a chamber having a window through which the laser light passes and housing the stage, and the variable slit is positioned directly above the window.

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