Laser irradiation device and laser irradiation method

Abstract

This laser irradiation device comprises a laser oscillator, an optical system for propagating laser light oscillated from the laser oscillator, and a lens that irradiates an irradiation target with the laser light propagated from the optical system. The optical system comprises a first detection unit. The first detection unit comprises: a photoelectric element that receives the laser light and performs photoelectric conversion; and an oscilloscope that receives an electric signal from the photoelectric element and outputs a waveform of voltage variation over time.

Description

Laser irradiation device and laser irradiation method

[0001] This disclosure relates to a laser irradiation device and a laser irradiation method.

[0002] Patent Document 1 discloses a laser processing apparatus that can monitor the output of the laser beam during processing without interrupting the processing while processing a workpiece.

[0003] Japanese Patent Application Publication No. 2021-030283

[0004] The technology described herein appropriately irradiates the target object with laser light.

[0005] One aspect of the present disclosure is a laser irradiation device comprising: a laser oscillator; an optical system for propagating laser light emitted from the laser oscillator; and a lens for irradiating a target with the laser light propagated from the optical system, wherein the optical system comprises a first detection unit, the first detection unit comprising a photoelectric element that receives the laser light and converts it into photoelectric energy, and an oscilloscope that receives an electrical signal from the photoelectric element and outputs a waveform of the time change of voltage.

[0006] According to this disclosure, laser light can be appropriately irradiated onto the target object.

[0007] This is an explanatory diagram of a polymerized wafer as an example of a processing target. This is a plan view showing the general configuration of the wafer processing system. This is a side view showing the general configuration of the first laser irradiation device (second laser irradiation device, third laser irradiation device). This is a plan view showing the general configuration of the first laser irradiation device (second laser irradiation device, third laser irradiation device). This is an explanatory diagram showing the general configuration of the laser irradiation unit. This is an explanatory diagram showing an example of a waveform detected by an oscilloscope. This is an explanatory diagram showing an enlarged portion of the waveform detected by an oscilloscope. This is a flowchart showing the main steps of a wafer processing method according to one embodiment. This is a flowchart showing the main steps of a method for monitoring laser characteristics according to one embodiment. This is an explanatory diagram showing an example of the state of a polymerized wafer in the main steps of a wafer processing method according to one embodiment. This is an explanatory diagram showing the general configuration of a laser irradiation unit according to one modification. This is an explanatory diagram showing the general configuration of a laser irradiation unit according to one modification.

[0008] The technology disclosed herein enables appropriate laser processing of a substrate. Hereinafter, a wafer processing system as a substrate processing system and a wafer processing method as a substrate processing method according to this embodiment will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, thus omitting redundant explanations.

[0009] In the wafer processing system 1 described later according to this embodiment, as an example of a processing target, processing is performed on a polymerized wafer T, which is a polymerized substrate formed by bonding a first wafer W as a first substrate and a second wafer S as a second substrate, as shown in Figure 1. Hereinafter, in the first wafer W, the side that is bonded to the second wafer S will be called the surface Wa, and the side opposite to the surface Wa will be called the back surface Wb. Similarly, in the second wafer S, the side that is bonded to the first wafer W will be called the surface Sa, and the side opposite to the surface Sa will be called the back surface Sb.

[0010] The first wafer W is a semiconductor wafer such as a silicon substrate, and at least one film is formed on the surface Wa side by lamination. Hereinafter, the film formed on this surface Wa side will be referred to as the "laminated film". In this embodiment, the laminated film includes a device layer Dw and a bonding film Fw. The device layer Dw includes a plurality of devices. The bonding film Fw includes, for example, an oxide film (THOX film, SiO ２ A film (TEOS film), SiC film, SiCN film, or adhesive can be used. The first wafer W is then bonded to the second wafer S via a bonding film Fw.

[0011] The second wafer S has a configuration similar to that of the first wafer W, for example. That is, a device layer Ds and a bonding film Fs are formed as a laminated film on the surface Sa side, and the peripheral edge is chamfered. Note that the second wafer S does not have to be a device wafer on which the device layer Ds is formed; for example, it may be a support wafer that supports the first wafer W.

[0012] In Figure 1, an example is shown where a device layer and a bonding film are formed as a laminated film on the surfaces of the first wafer W and the second wafer S. However, the type and number of layers of the laminated film are not limited to this.

[0013] As shown in Figure 2, the wafer processing system 1 has a configuration in which an loading / unloading station 2 and a processing station 3 are integrally connected. At the loading / unloading station 2, for example, a hoop F capable of accommodating multiple polymerized wafers T is loaded and unloaded to and from the outside. The processing station 3 is equipped with various processing devices for performing desired processing on the polymerized wafers T.

[0014] The loading / unloading station 2 is equipped with a hoop mounting table 10 on which multiple hoops F are placed. Adjacent to the hoop mounting table 10, on the positive X-axis side, is a wafer transport device 20. The wafer transport device 20 moves along a transport path 21 extending in the Y-axis direction and is configured to transport the superimposed wafer T between the hoops F on the hoop mounting table 10 and the transition device 30 described later.

[0015] At the loading / unloading station 2, a transition device 30 is provided adjacent to the wafer transport device 20 on the positive X-axis side of the wafer transport device 20 for transferring the polymerized wafer T between the loading / unloading station 2 and the processing station 3.

[0016] The processing station 3 is equipped with a wafer transport device 40, a periphery removal device 50, a cleaning device 60, a first laser irradiation device 70, a second laser irradiation device 80, and a third laser irradiation device 90. The wafer transport device 40 is located on the positive X-axis side of the transition device 30. The periphery removal device 50, the first laser irradiation device 70, and the third laser irradiation device 90 are located on the positive Y-axis side of the wafer transport device 40, while the cleaning device 60 and the second laser irradiation device 80 are located on the negative Y-axis side of the wafer transport device 40. Note that the number and arrangement of the periphery removal device 50, cleaning device 60, first laser irradiation device 70, second laser irradiation device 80, and third laser irradiation device 90 are not limited to this embodiment and can be determined arbitrarily.

[0017] The wafer transport device 40 is configured to move freely along a transport path 41 extending in the X-axis direction, and is capable of transporting polymerized wafers T to the transition device 30, edge removal device 50, cleaning device 60, first laser irradiation device 70, second laser irradiation device 80, and third laser irradiation device 90.

[0018] The edge removal device 50 removes the peripheral portion We of the first wafer W, i.e., edge trims it, using the peripheral modification region N formed in the first laser irradiation device 70 (described later) and the bonding force reduction region R formed in the second laser irradiation device 80 (described later) as starting points.

[0019] The cleaning device 60 cleans the first wafer W and the second wafer S after the edges have been trimmed by the edge removal device 50, and removes particles from these wafers. The cleaning method can be arbitrarily selected.

[0020] The first laser irradiation device 70 irradiates the interior of the first wafer W, which is the target of irradiation, with a first laser beam L1 (modification laser beam, such as a fiber laser or YAG laser) to form a peripheral modification layer M (see Figure 10 described later) and a peripheral modification region N (see Figure 10 described later) which serves as the starting point for peeling off the peripheral portion We. The first laser irradiation device 70 also has a control device 71, which will be described later.

[0021] The second laser irradiation device 80 emits a second laser beam L2 (interface laser beam, for example CO2) at the interface between the first wafer W and the second wafer S, which are the targets of irradiation. ２ A laser is irradiated to form a bonding force reduction region R (see Figure 10, described later) in the peripheral portion We where the bonding force between the first wafer W and the second wafer S is reduced. In the technology described herein, the "interface between the first wafer W and the second wafer S" includes the interfaces of the first wafer W, the device layers Dw and Ds, the bonding films Fw and Fs, and the second wafer S, as well as the interiors of each. In other words, the formation location of the bonding force reduction region R is not particularly limited as long as the bonding force between the first wafer W and the second wafer S can be reduced. Furthermore, as shown in Figure 2, the second laser irradiation device 80 has a control device 81, which will be described later.

[0022] The third laser irradiation device 90 irradiates the target to be irradiated with a third laser beam L3 (removal laser beam, for example, a UV femtosecond laser) and removes the target by laser ablation. The target to be irradiated is, as will be described later, for example, a surface film (bonding film Fw, Fs and device layer Dw, Ds) on the surface Sa of the second wafer S. Furthermore, as shown in Figure 2, the third laser irradiation device 90 has a control device 91, which will be described later.

[0023] As shown in Figure 2, the wafer processing system 1 is equipped with control units: a control unit 71, a control unit 81, a control unit 91, and at least one control unit 100. The control unit 71 individually controls the operation of the first laser irradiation device 70. The control unit 81 individually controls the operation of the second laser irradiation device 80. The control unit 91 individually controls the operation of the third laser irradiation device 90. The control unit 100 oversees the control of a series of wafer processing operations in the wafer processing system 1.

[0024] Control devices 71, 81, 91, and 100 each process computer-executable instructions causing the first laser irradiation device 70, the second laser irradiation device 80, the third laser irradiation device 90, and the wafer processing system 1 to perform the various processes described herein. Control devices 71, 81, 91, and 100 can each be configured to control the elements of the first laser irradiation device 70, the second laser irradiation device 80, the third laser irradiation device 90, and the wafer processing system 1 to perform the various processes described herein. In one embodiment, some or all of control device 71 may be included in the first laser irradiation device 70, some or all of control device 81 may be included in the second laser irradiation device 80, some or all of control device 91 may be included in the third laser irradiation device 90, and some or all of control device 100 may be included in the wafer processing system 1.

[0025] Control devices 71, 81, 91, and 100 may each include a processing unit, a storage unit, and a communication interface. Control devices 71, 81, 91, and 100 may each be implemented, for example, by a computer. The processing unit may be configured to read a program from the storage unit that provides logic or routines enabling various control operations, and to perform various control operations by executing the read program. This program may be stored in the storage unit in advance, or it may be obtained via a medium when needed. The obtained program is stored in the storage unit and read from the storage unit and executed by the processing unit. The medium may be various storage media readable by a computer, or it may be a communication line connected to a communication interface. The storage medium may be temporary or permanent. The processing unit may be a CPU (Central Processing Unit), or it may be one or more circuits. The storage unit may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface may communicate with the first laser irradiation device 70, the second laser irradiation device 80, the third laser irradiation device 90, and the wafer processing system 1 via a communication line such as a LAN (Local Area Network).

[0026] In this embodiment, control devices 71, 81, and 91 are individually installed for the first laser irradiation device 70, the second laser irradiation device 80, and the third laser irradiation device 90, respectively. However, these control devices 71, 81, and 91 may be integrated with the control device 100. In other words, the operation of the first laser irradiation device 70, the second laser irradiation device 80, and the third laser irradiation device 90 may be controlled by the control device 100.

[0027] The following describes examples of configurations applicable to the first laser irradiation device 70, the second laser irradiation device 80, and the third laser irradiation device 90. The following description will focus on the case where the first laser beam L1 is irradiated using the first laser irradiation device 70, but the same applies when the second laser beam L2 and the third laser beam L3 are irradiated using the second laser irradiation device 80 and the third laser irradiation device 90. When applying the following configuration to the second laser irradiation device 80, the first laser beam L1 will be replaced with the second laser beam L2, and the control device 71 will be replaced with the control device 81, as appropriate. When applying the following configuration to the third laser irradiation device 90, the first laser beam L1 will be replaced with the third laser beam L3, and the control device 71 will be replaced with the control device 91, as appropriate.

[0028] As shown in Figures 3 and 4, the first laser irradiation device 70 has a chuck 140 as a substrate holding part that holds the polymerized wafer T, which is the target of irradiation, on its upper surface. The chuck 140 holds the back surface Sb of the second wafer S by suction when the first wafer W is positioned on top and the second wafer S is positioned on the bottom. The chuck 140 is supported by a slider table 142 via an air bearing 141. A rotation mechanism 143 is provided on the lower side of the slider table 142. The rotation mechanism 143 incorporates, for example, a motor as a drive source. The chuck 140 is configured to rotate freely around a vertical axis via the air bearing 141 by the rotation mechanism 143. The slider table 142 is configured to move freely along a rail 146 that extends in the Y-axis direction on a base 145 via a moving mechanism 144 provided on its lower side. The drive source for the moving mechanism 144 is not particularly limited, but for example, a linear motor can be used.

[0029] In one embodiment, the control device 71 controls the slider table 142 to move the irradiated object so that a desired processing position P on the surface of the irradiated object is positioned at the focal position of the first laser beam L1.

[0030] A first power meter 147 is provided on the side of the chuck 140. The first power meter 147 is supported on a slider table 142 so as to be able to move in and out of the optical axis of the first laser beam L1, as shown by the double-ended arrow AR1 in Figure 5. In one embodiment, the control device 71 controls the slider table 142 to move the first power meter 147 so that it is positioned at the irradiation position of the first laser beam L1. Note that the means for moving the power meter 147 is not limited to the slider table 142; the power meter 147 may be fixed directly below the lens 152 or it may be movable as long as it is movable. When moving it, for example, any desired means of moving independently of the slider table 142 can be used.

[0031] The first power meter 147 is, for example, a calorimeter, and is configured to detect characteristics including the average power (unit W; hereinafter referred to as "terminal power") of the pulses of the first laser light L1 irradiated onto the processing position P on the irradiated object, and output it to the control device 71.

[0032] The first laser irradiation device 70 is provided with a laser irradiation unit 150. As shown in Figure 5, the laser irradiation unit 150 has a laser engine 151, a lens 152, and a first optical system 153.

[0033] The laser engine 151 includes a laser head 201 equipped with a laser oscillator 200 that emits a first laser beam L1 in a pulsed manner, and a second optical system 202, which will be described later. The laser head 201 may also include other devices besides the laser oscillator 200, such as an amplifier.

[0034] The lens 152 focuses and irradiates the interior of the first wafer W held by the chuck 140 with the first laser beam L1. This modifies the processing position P where the first laser beam L1 is focused and irradiated inside the polymerized wafer T, forming a peripheral modified layer M (see Figure 10, described later).

[0035] The first optical system 153 includes a first detection unit 211 and a second detection unit 212. The first detection unit 211 and the second detection unit 212 are configured to propagate the first laser beam L1 output from the laser engine 151 to the lens 152, and detect a plurality of characteristics related to the first laser beam L1.

[0036] The first detection unit 211 includes a first mirror 221, a photoelectric element 222, and an oscilloscope 223. The first mirror 221 is configured to transmit a part of the first laser beam L1 traveling from the laser engine 151 to the first detection unit 211, and reflect the remaining part. The first laser beam L1 transmitted through the first mirror 221 travels to the photoelectric element 222. The first laser beam L1 reflected by the first mirror 221 travels to the second detection unit 212.

[0037] The photoelectric element 222 receives the first laser beam L1 transmitted through the first mirror 221, performs photoelectric conversion, and outputs an electrical signal to the oscilloscope 223. For example, a PIN photodiode can be used as the photoelectric element 222. A PIN photodiode is preferable because it has a response speed capable of appropriately performing photoelectric conversion following the pulses of the first laser beam L1.

[0038] The oscilloscope 223 is configured to receive the electrical signal from the photoelectric element 222, and output the time change of voltage as the pulse waveform of the first laser beam L1 to, for example, the control device 71. The oscilloscope 223 may be installed outside the first laser irradiation device 70, for example, together at the installation site of the control device 71. When at least a part of the oscilloscope 223 is implemented by computer software, at least a part of the oscilloscope 223 may be incorporated in the control device 71.

[0039] The pulse waveform of the first laser beam L1 output from the oscilloscope 223 to the control device 71 can be visualized as shown in FIGS. 6 and 7 for convenience of explanation. FIG. 7 is an enlarged view of one period λ of the pulse shown in FIG. 6 along the time axis. In one embodiment, the control device 71 calculates characteristics including the average power Pa (W), frequency (kHz), and pulse width w (sec) of the pulse of the first laser beam L1 based on the pulse waveform. The average power Pa can be calculated as an integral value of voltage over one period of the pulse (the area of the hatched portion in FIG. 7). The pulse width w can be calculated as the time width at half the peak voltage Pk of the pulse (Pk / 2).

[0040] The second detection unit 212 includes a second mirror 231 and a first profiler 232. The second mirror 231 is configured to transmit a part of the first laser beam L1 that has traveled to the second detection unit 212 and reflect the remainder. The first laser beam L1 reflected by the second mirror 231 travels to the lens 152. The first laser beam L1 transmitted through the second mirror 231 travels to the first profiler 232.

[0041] The first profiler 232 is, for example, a camera-type beam profiler, and is configured to receive the first laser beam L1 transmitted through the second mirror 231, detect the profile of the first laser beam L1, and output the detected profile to, for example, the control device 71.

[0042] In one embodiment, the control device 71 may calculate characteristics including the beam diameter, beam shape (intensity distribution), and spot size (μm ２ ) of the first laser beam L1 based on the profile of the first laser beam L1 output from the first profiler 232.

[0043] In one embodiment, the control device 71 calculates pulse energy (μJ) from the average power Pa and the frequency, and further calculates peak power density (W / μm ２ ) from the pulse energy, the pulse width w and the spot size.

[0044] The first optical system 153 may also include a third mirror 241 configured to reflect the first laser beam L1 output from the laser engine 151 to the first detection unit 211. The number and arrangement of the third mirrors 241 are not limited to the illustrated example and can be changed as appropriate, and it is also possible to configure the first optical system 153 without providing the third mirrors 241.

[0045] The first optical system 153 may also include a second profiler 243 as a fourth detection unit, which is configured to receive the first laser light L1 reflected by the second mirror 231 and output a profile of the first laser light L1 to, for example, a control device 71. The configuration of the second profiler 243 may be the same as that of the first profiler 232.

[0046] The second profiler 243 can be configured to be retractable in the direction shown by the double-ended arrow AR2 in Figure 5, so as to switch between a state in which the second profiler 243 is not positioned on the optical axis of the first laser beam L1 between the second mirror 231 and the lens 152, and a state in which it is positioned on the optical axis. When the second profiler 243 is not positioned on the optical axis of the first laser beam L1 between the second mirror 231 and the lens 152, the first laser beam L1 travels to the lens 152. When the second profiler 243 is positioned on the optical axis of the first laser beam L1 between the second mirror 231 and the lens 152, the second profiler 243 receives the first laser beam L1 and detects the profile of the first laser beam L1. The means for retracting the second profiler 243 are not particularly limited, and a moving mechanism using a motor and rails may be used, for example.

[0047] In one embodiment, the control device 71 calculates the characteristics of the first laser beam L1, including its beam diameter and beam shape, based on the profile of the first laser beam L1 output to the control device 71 from the second profiler 243. The control device 71 may also calculate the diffusion angle (directivity) of the first laser beam L1 based on the beam diameter and beam shape of the first laser beam L1 output from the first profiler 232 and the second profiler 243, respectively. Furthermore, the control device 71 may adjust the diffusion angle to a desired value by controlling the expander 255 of the second optical system 202, which will be described later.

[0048] The second optical system 202 includes a fourth detection unit 251, a fifth detection unit 252, a sixth detection unit 253, an attenuator 254, and an expander 255. The fourth to sixth detection units 251, 252, and 253 are configured to propagate the first laser beam L1 emitted from the laser head 201 to the attenuator 254 and to detect multiple characteristics related to the first laser beam L1.

[0049] The fourth detection unit 251 includes a fourth mirror 261 and a second power meter 262. The fourth mirror 261 can be moved in and out in the direction shown by the double-ended arrows AR3 in Figure 5, so as to switch between a state in which the fourth mirror 261 is not positioned on the optical axis of the first laser beam L1 between the laser head 201 and the fifth detection unit 252, and a state in which the fourth mirror 261 is positioned on the optical axis. When the fourth mirror 261 is not positioned on the optical axis, the first laser beam L1 travels to the fifth detection unit 252. When the fourth mirror 261 is positioned on the optical axis, the first laser beam L1 is reflected by the fourth mirror 261 and travels to the second power meter 262. The means for moving the fourth mirror 261 in and out are not particularly limited, and a moving mechanism using a motor and rails may be used, for example.

[0050] The second power meter 262 is, for example, a calorimeter, and is configured to detect characteristics including the average power (unit W; hereinafter referred to as "starting power") of the pulses of the first laser light L1 emitted from the laser head 201, and output them to, for example, the control device 71.

[0051] In one embodiment, the control device 71 may control the laser head 201 to adjust the initial power of the first laser beam L1 from the laser head 201 to a desired level.

[0052] The fifth detection unit 252 includes a fifth mirror 271 and a third profiler 272. The sixth detection unit 253 includes a sixth mirror 281 and a fourth profiler 282. The fifth mirror 271 is configured to transmit a portion of the first laser beam L1 that has traveled to the fifth detection unit 252 and reflect the remainder. The first laser beam L1 that has passed through the fifth mirror 271 travels to the sixth detection unit 253. The first laser beam L1 reflected by the fifth mirror 271 travels to the third profiler 272. The sixth mirror 281 is configured to transmit a portion of the first laser beam L1 that has traveled to the sixth detection unit 253 and reflect the remainder. The first laser beam L1 that has passed through the sixth mirror 281 travels to the sixth detection unit 253. The first laser beam L1 reflected by the fifth mirror 271 travels to the attenuator 254.

[0053] The third profiler 272 and the fourth profiler 282 are configured to receive the first laser beam L1 and output a profile of the first laser beam L1 to, for example, the control device 71. The configuration of the third profiler 272 and the fourth profiler 282 may be the same as that of the first profiler 232.

[0054] In one embodiment, the control device 71 calculates characteristics including the direction of propagation (optical axis position) of the first laser beam L1 based on the profiles of the first laser beam L1 output to the control device 71 from the third profiler 272 and the fourth profiler 282. Furthermore, the control device 71 may control the laser head 201 based on the direction of propagation of the first laser beam L1 to adjust it so that the direction of propagation is desired.

[0055] The attenuator 254 is configured to variably attenuate the power of the first laser beam L1. In one embodiment, the control device 71 may calculate the attenuation rate of the first laser beam L1 from the laser head 201 to the processing position P of the irradiated object based on the ratio of the termination power of the first laser beam L1 detected by the first power meter 147262 and the starting power of the first laser beam L1 detected by the second power meter. Alternatively, the control device 71 may adjust the attenuation rate to a desired value by controlling the attenuator 254. In one embodiment, the control device 71 may determine the soundness of the laser irradiation unit 150 by comparing the calculated attenuation rate with a predetermined threshold.

[0056] The expander 255 is configured to change the diffusion angle of the first laser beam L1. In one embodiment, as described above, the control device 71 may control the expander 255 to adjust the diffusion angle of the first laser beam L1 to a desired value.

[0057] The second optical system 202 may also include a seventh mirror 291 and an eighth mirror 292 configured to propagate the first laser beam L1 output from the laser head 201. The number and arrangement of the seventh mirror 291 and the eighth mirror 292 are not limited to the illustrated example and can be changed as appropriate, and it is also possible to configure the second optical system 202 without the seventh mirror 291 and the eighth mirror 292.

[0058] Furthermore, the configuration of the laser engine 151, which includes the laser head 201 and the second optical system 202, is not limited to the above configuration and may have any other desired known configuration.

[0059] The propagation by transmission and reflection in the various mirrors provided in the first optical system 153 and the second optical system 202 is not limited to the illustrated example, and transmission and reflection may be interchanged as appropriate. Furthermore, other desired mirrors may be provided on the optical axis to propagate the first laser beam L1 through different paths.

[0060] Next, a wafer processing procedure performed using the wafer processing system 1 configured as described above will be explained. In this embodiment, the wafer processing procedure involves edge trimming, which removes the peripheral portion We of the first wafer W. In this embodiment, the first wafer W and the second wafer S are bonded together to form a polymerized wafer T in advance.

[0061] First, a hoop F containing multiple polymerized wafers T is placed on the hoop mounting table 10 of the loading / unloading station 2 (St11 in Figure 8).

[0062] Next, the wafer transport device 20 removes the polymerized wafer T from the hoop F and transports it to the transition device 30 (St12 in Figure 8).

[0063] Next, the polymerized wafer T is transported to the second laser irradiation device 80 by the wafer transport device 40. In the second laser irradiation device 80, the polymerized wafer T held in the chuck 140 is irradiated with a second laser beam L2 along the interface between the first wafer W and the second wafer S (in the illustrated example, the interface between the bonding film Fw and the bonding film Fs), as shown in Figure 10(a). This second laser beam L2 forms a bonding force reduction region R at the interface between the first wafer W and the second wafer S (St13 in Figure 8). The irradiation of the second laser beam L2 is performed while rotating the chuck 140, and the bonding force reduction region R is formed in an annular shape in plan view. The irradiation direction of the second laser beam L2 is arbitrary, but for example, it is irradiated from the radial outside to the inside. The radial width of the irradiation region of the second laser beam L2 is set to a width that can appropriately remove the peripheral portion We of the first wafer W. The characteristics of the second laser beam L2 irradiated using the second laser irradiation device 80 in St13 can be predetermined according to the purpose of the processing. For example, the terminal power of the second laser beam L2 can be determined according to the purpose of the processing, and the attenuation rate required to generate that terminal power can be determined. In St13, the terminal power at the irradiated object is expected to be the desired value by irradiating with the second laser beam L2 at the determined attenuation rate. Furthermore, the characteristics of the second laser beam L2 irradiated using the second laser irradiation device 80 in St13 can be monitored by a method described later.

[0064] Next, the polymerized wafer T on which the bonding strength reduction region R is formed is transported to the first laser irradiation device 70 by the wafer transport device 40. In the first laser irradiation device 70, as shown in Figure 10(b), the polymerized wafer T held in the chuck 140 is irradiated with first laser light L1 into the interior of the first wafer W along the boundary between the peripheral portion We and the central portion Wc of the first wafer W. The boundary between the peripheral portion We and the central portion Wc is, for example, a boundary that extends in the thickness direction of the first wafer W. When the peripheral modified layer M is formed by this laser light L1, a crack C extends from the peripheral modified layer M along the boundary between the peripheral portion We and the central portion Wc. Then, a peripheral modified region N including the peripheral modified layer M and the crack C is formed (St14 in Figure 8). The crack C connects to the bonding strength reduction region R, and the peripheral modified region N extends between the back surface Wb of the first wafer W and the bonding strength reduction region R. Furthermore, the irradiation of the first laser beam L1 is performed while rotating the chuck 140, and the peripheral modification region N is formed in an annular shape in a plan view. The characteristics of the first laser beam L1 irradiated using the first laser irradiation device 70 in St14 can be predetermined according to the purpose of the processing. The determination of these characteristics is the same as the determination of the characteristics of the second laser beam L2 in St13. The characteristics of the first laser beam L1 irradiated using the first laser irradiation device 70 in St14 can be monitored by a method described later.

[0065] Next, the polymerized wafer T on which the peripheral modification region N has been formed is transported to the peripheral removal device 50 by the wafer transport device 40. In the peripheral removal device 50, as shown in Figure 10(c), an insertion blade 120 is inserted between the first wafer W and the second wafer S with respect to the polymerized wafer T held in the chuck 110, and the peripheral portion We is removed from the first wafer W (St15 in Figure 8). At this time, the peripheral portion We is peeled off and removed from the central portion Wc of the first wafer W, with the peripheral modification region N and the bonding force reduction region R as the starting points.

[0066] Next, the polymerized wafer T from which the peripheral portion We has been removed is transported to the third laser irradiation device 90 by the wafer transport device 40. In the third laser irradiation device 90, the polymerized wafer T held in the chuck 140 is irradiated with the third laser beam L3 on the surface film (bonding films Fw, Fs and device layers Dw, Ds) on the peripheral portion of the surface Sa of the second wafer S, as shown in Figure 10(d). This third laser beam L3 removes the surface film on the peripheral portion of the surface Sa of the second wafer S by laser ablation (St16 in Figure 8). The characteristics of the third laser beam L3 irradiated using the third laser irradiation device 90 in St16 can be determined in advance according to the purpose of the process. The determination of these characteristics is the same as the determination of the characteristics of the second laser beam L2 in St13. The characteristics of the third laser beam L3 irradiated using the third laser irradiation device 90 in St16 can be monitored by a method described later.

[0067] Next, the polymerized wafer T from which the surface film of the second wafer S has been removed is transported to the cleaning device 60 by the wafer transport device 40. In the cleaning device 60, the first wafer W and the second wafer S are cleaned (St17 in Figure 8).

[0068] Subsequently, the polymerized wafer T, after all processing has been completed, is transported to the transition device 30 by the wafer transport device 40, and then further transported to the hoop F of the hoop mounting table 10 by the wafer transport device 20 (St18 in Figure 8). In this way, the series of wafer processing in the wafer processing system 1 is completed.

[0069] The following describes an example configuration of a method for monitoring laser characteristics that can be implemented in any of St13, St14, and St16 related to the laser processing described above using the first laser irradiation device 70, the second laser irradiation device 80, and the third laser irradiation device 90. The following description will focus on the case where the monitoring method is implemented in St14, where the first laser beam L1 is irradiated using the first laser irradiation device 70, but the same applies to St13 and St16, which use the second laser irradiation device 80 and the third laser irradiation device 90. When applying the following configuration to St13, St14 shall be read as St13, the first laser irradiation device 70 as the second laser irradiation device 80, and the first laser beam L1 as the second laser beam L2 in the following description. When applying the following configuration to St16, St14 shall be read as St16, the first laser irradiation device 70 as the third laser irradiation device 90, and the first laser beam L1 as the third laser beam L3 in the following description. The average power Pa calculated based on the detection results of the first detection unit 211 is the direct target of monitoring in the method according to this embodiment, and will therefore be referred to as "monitored power" in the following description.

[0070] First, prior information acquired before executing the wafer processing method including St13 is read out (St101 in Figure 9). The prior information includes information on the combination of the termination power detected by the first power meter 147 and the monitored power calculated by the control device 71 based on the detection result of the first detection unit 211 of the first optical system 153.

[0071] As an example, the prior information is obtained in advance as described below through a preliminary experiment or the like using the first laser irradiation device 70. First, in a state where the first power meter 147 is arranged at the irradiation position of the first laser light L1, the first laser light L1 is output from the laser head 201, and the first power meter 147 is irradiated with the first laser light L1. During the irradiation of the first laser light L1, the terminal power is detected by the first power meter 147. The attenuation rate is adjusted by the attenuator 254 such that the terminal power detected by the first power meter 147 becomes a desired terminal power. The power to be monitored is calculated based on the detection result of the first detection unit 211 when the terminal power is adjusted to the desired terminal power by the first power meter 147. The combination of the terminal power and the power to be monitored obtained through the above steps is stored as one irradiation condition in the prior information. Further, the desired terminal power may be changed to another value, and the combination of the terminal power and the power to be monitored may be stored as another irradiation condition in the same manner. This allows combinations of terminal power and power to be monitored under a plurality of irradiation conditions to be stored as prior information. There are no particular limitations on the combinations of terminal power and power to be monitored that should be stored as prior information, and for example, they may be determined in accordance with the irradiation conditions of the first laser light L1 that are scheduled to be performed in a wafer processing method using the first laser irradiation device 70.

[0072] When combinations of terminal power and power to be monitored under a plurality of irradiation conditions are stored as prior information, in St14, the predetermined terminal power of the first laser light L1 to be irradiated to the processing position P of the irradiation target is read out. Then, the scheduled terminal power is collated with the prior information read in St101, and the power to be monitored corresponding to the scheduled terminal power (hereinafter referred to as "scheduled monitored power") is specified (St102 in Fig. 9). As an example, in the prior information, the terminal power value P Ｅ１ and the power to be monitored value P Ｍ１ combination, and the terminal power value P Ｅ２ and the power to be monitored value P Ｍ２ combination are stored. In this case, the value of the scheduled terminal power in St14 is P Ｅ１ in this case, in St102, the value PＥ１ The value P of the monitored power corresponding to this value. Ｍ１ This is identified as the planned monitored power. Similarly, the value of the planned termination power at St14 is P Ｅ２ If that is the case, then St102 will have the value P Ｅ２ The value P of the monitored power corresponding to this value. Ｍ２ This is identified as the power to be monitored.

[0073] Next, at St14, the first laser beam L1 is irradiated onto the processing position P of the target to be irradiated with a predetermined attenuation rate. Then, while the first laser beam L1 is irradiated, the monitored power (hereinafter referred to as "measured monitored power") is calculated based on the detection result of the first detection unit 211 of the first optical system 153 (St103 in Figure 9).

[0074] Next, the measured monitored power calculated in St103 is compared with the planned monitored power identified in St102 (St104 in Figure 9).

[0075] If the comparison determines that the measured monitored power is equal to the planned monitored power or within a predetermined tolerance range, then St13 is continued, and monitoring is returned to St103. The predetermined tolerance range for the planned monitored power is not particularly limited and may be determined to obtain the desired accuracy according to the purpose of the processing.

[0076] If the measured power being monitored is determined to be outside the tolerance range of the planned power being monitored, an abnormality determination process is performed (St105 in Figure 9).

[0077] In one embodiment, St105 may issue an alert indicating that the measured monitored power is outside the tolerance range of the planned monitored power.

[0078] In one embodiment, if St105 determines that the measured monitored power is outside the tolerance range of the planned monitored power, it may be determined that the processing in the laser irradiation unit 150 is abnormal, and St14 may be stopped to terminate the wafer processing. Here, one possible cause of abnormal processing in the laser irradiation unit 150 is a change in the power output from the laser head 201. In one embodiment, after stopping St14, the attenuation rate of the first laser beam L1 is changed by controlling the attenuator 254 so that the monitored power is within the tolerance range, or the termination power is within the desired range. Then, in St14 which is executed again, the first laser beam L1 is irradiated onto the processing position P of the target to be irradiated with the changed attenuation rate. After that, the above processing and monitoring may be continued in St14. The attenuation rate can be changed by the attenuator 254 in the following way, for example. If, as a result of the comparison in St104, the measured monitored power is below the tolerance range of the planned monitored power, the attenuation rate is reduced. Furthermore, if the measured power level exceeds the tolerance range of the planned power level, the attenuation rate will be increased.

[0079] According to the first laser irradiation apparatus 70 and laser characteristics monitoring method of the above embodiment, in the processing of the polymerized wafer T using the first laser irradiation apparatus 70 of St14, it is possible to monitor the power of the first laser beam L1 during irradiation with the first laser beam L1.

[0080] Furthermore, if the measured monitored power of the currently irradiated first laser beam L1 is outside the tolerance range of the planned monitored power, it can be estimated that the termination power of the currently irradiated first laser beam L1 will differ from the planned termination power. By estimating the termination power during irradiation of the first laser beam L1, the integrity of the processing by the first laser beam L1 can be monitored.

[0081] While a first power meter 147 can be used to actually detect the termination power, the first power meter 147 is configured to detect power at the position where the actual irradiation target should be placed. Therefore, it is not possible to detect the termination power while the first laser beam L1 is irradiating the irradiation target. Furthermore, although it is conceivable to place a power meter on the optical path of the first optical system 153, as in the first detection unit 211 of this embodiment, conventionally used calorimeters do not have sufficient response speed. For this reason, it is difficult to detect the termination power while the first laser beam L1 is irradiating using a calorimeter.

[0082] To address the above-mentioned problems, the first detection unit 211 in this embodiment is positioned on the optical path of the first optical system 153, so that it can monitor the power of the first laser beam L1 and estimate the termination power without interfering with the irradiation of the target object with the first laser beam L1. Furthermore, the photoelectric element 222 and oscilloscope 223 provided in the first detection unit 211 can detect the characteristics of the first laser beam L1 with a sufficient response speed, so that it is possible to monitor the power of the first laser beam L1 in real time while the target object is being irradiated with the first laser beam L1.

[0083] Furthermore, the combination of the photoelectric element 222 and oscilloscope 223 in the first detection unit 211 and the first profiler 232 in the second detection unit 212 allows for sufficient detection of not only the power of the first laser beam L1 but also other characteristics of the first laser beam L1 necessary for calculating the peak power density, such as pulse energy, pulse width w, and spot size.

[0084] (Modification 1) Below, a modification 1 of the above embodiment, the laser irradiation unit 300, will be described. Below, the case in which the laser irradiation unit 300 is applied to the first laser irradiation device 70 will be described, but it is not limited to this, and may be applied to either the second laser irradiation device 80 or the third laser irradiation device 90, for example. Configurations that are not specifically described in the following description can be the same as those of the laser irradiation unit 150.

[0085] As shown in Figure 11, the laser irradiation unit 300 has a configuration that further includes a beam splitter 301 and a fifth profiler 302 in the first detection unit 211 according to the above embodiment.

[0086] The beam splitter 301 is configured to spectrally separate the first laser light L1 that has passed through the first mirror 221, propagating a portion of it to the photoelectric element 222 and the remainder to the fifth profiler 302.

[0087] The fifth profiler 302 receives the first laser beam L1 and outputs a profile of the first laser beam L1 to, for example, the control device 71. The configuration of the fifth profiler 302 may be the same as that of the first profiler 232.

[0088] In one embodiment, the control device 71 calculates the characteristics of the first laser light L1, including the beam diameter and beam shape, based on the profile of the first laser light L1 output to the control device 71 from the fifth profiler 302. The control device 71 may also calculate the diffusion angle of the first laser light L1 based on the beam diameter and beam shape of the first laser light L1 output from the first profiler 232 and the fifth profiler 302, respectively. Furthermore, the control device 71 may adjust the diffusion angle to a desired value by controlling the expander 255 of the second optical system 202.

[0089] In this modified example, the diffusion angle of the first laser beam L1 can be calculated using the combination of the first profiler 232 and the fifth profiler 302, instead of the combination of the first profiler 232 and the second profiler 243. Therefore, in this modified example, the second profiler 243 does not need to be provided.

[0090] (Modification 2) Below, a second modification of the above embodiment, the laser irradiation unit 310, will be described. Below, the case in which the laser irradiation unit 310 is applied to the first laser irradiation device 70 will be described, but it is not limited to this, and may be applied to either the second laser irradiation device 80 or the third laser irradiation device 90, for example. Configurations that are not specifically described in the following description can be the same as those of the laser irradiation unit 150.

[0091] As shown in Figure 12, the laser irradiation unit 310 has a configuration that includes a seventh detection unit 311 above the chuck 140 that holds the polymerized wafer T to be irradiated. The seventh detection unit 311 includes a photoelectric element 312 and an oscilloscope 313.

[0092] The photoelectric element 312 receives the scattered light L1' of the first laser light L1 scattered at the processing position P of the polymerized wafer T to be irradiated, performs photoelectric conversion, and outputs an electrical signal to the oscilloscope 313. The oscilloscope 313 receives the electrical signal from the photoelectric element 312 and is configured to output the time change of the voltage as a pulse waveform of the first laser light L1 to, for example, the control device 71. The control device 71 calculates the characteristics of the first laser light L1, including the average power Pa, frequency, pulse width w, and peak power of the pulse, based on the pulse waveform, in the same manner as the control related to the first detection unit 211 in the above embodiment.

[0093] In this modified example, the pulse waveform can be acquired by the seventh detection unit 311 and the characteristics of the first laser light L1 can be calculated, so at least the photoelectric element 222 and the oscilloscope 223 of the first detection unit 211 do not need to be provided. In this case, the first detection unit 211 may be provided with a fifth profiler 302 instead of the photoelectric element 222 and the oscilloscope 223. Furthermore, noise may be removed from the detected scattered light L1' signal by any known method.

[0094] The technology of this disclosure is not limited to edge trimming of a polymerized wafer T according to the above embodiment, but can be applied to a laser irradiation device for irradiating the entire surface of a polymerized wafer T with laser light to obtain the same effects as described above. Furthermore, the technology is not limited to processing a polymerized wafer T, but can be applied to a laser irradiation device that processes a desired workpiece such as a wafer or chip using a pulsed laser to obtain the same effects as described above.

[0095] The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims. For example, the constituent elements of the embodiments described above can be combined in any way. Such any combination will naturally yield the functions and effects of each constituent element in the combination, as well as other functions and effects that will be apparent to those skilled in the art from the description herein.

[0096] Furthermore, the effects described herein are merely descriptive or illustrative and not limiting. In other words, the technology relating to this disclosure may produce other effects that will be apparent to those skilled in the art from the description herein, in addition to or in lieu of the effects described herein.

[0097] 70 First laser irradiation device 71 Control device 80 Second laser irradiation device 81 Control device 90 Third laser irradiation device 91 Control device 150 Laser irradiation unit T Polymerized wafer

Claims

1. A laser irradiation device comprising: a laser oscillator; an optical system for propagating laser light emitted from the laser oscillator; and a lens for irradiating a target with the laser light propagated from the optical system, wherein the optical system includes a first detection unit, and the first detection unit comprises a photoelectric element that receives the laser light and converts it into photoelectric energy, and an oscilloscope that receives an electrical signal from the photoelectric element and outputs a waveform of the time change of voltage.

2. The laser irradiation device according to claim 1, wherein the photoelectric element is a PIN photodiode.

3. The laser irradiation device according to claim 2, wherein the first detection unit includes a first mirror that transmits a portion of the laser light and reflects the remainder, and the photoelectric element of the first detection unit receives the laser light propagated from the first mirror.

4. The laser irradiation device according to claim 2, wherein the photoelectric element of the first detection unit receives scattered light of the laser light scattered by the irradiated object.

5. A laser irradiation device according to any one of claims 1 to 4, comprising a control unit, wherein the oscilloscope is configured to output the waveform to the control unit, and the control unit performs control including calculating at least one characteristic of the laser light based on the waveform while performing control to irradiate the target with the laser light.

6. The laser irradiation device according to claim 5, wherein the characteristics of the laser light calculated by the control unit include a monitored power, which is the power of the laser light calculated based on the waveform.

7. The laser irradiation apparatus according to claim 6, wherein the control unit performs control including estimating the terminal power, which is the power of the laser beam at the processing position of the irradiated object, based on the monitored power.

8. The laser irradiation device according to claim 7, wherein the control unit performs control to irradiate the target object with the laser light, and while performing control to irradiate the target object with the laser light, it performs control to compare the measured monitored power, which is the calculated monitored power of the laser light, with the planned monitored power, which is the predetermined monitored power, and determines that the processing by the laser light is abnormal if the measured monitored power is outside the tolerance range of the planned monitored power.

9. A laser irradiation device according to claim 8, comprising a first power meter for detecting the termination power of the laser beam at a processing position of the irradiation target, wherein the control unit stores prior information including a combination of the termination power detected by the first power meter and the monitored power at the time the termination power is detected, and the planned termination power of the laser beam to be irradiated in a control for irradiating the irradiation target with the laser beam, and prior to the comparison, the control unit performs control including reading out the prior information and the planned termination power, and identifying the monitored power corresponding to the planned termination power as the planned monitored power by comparing the read-out planned termination power with the prior information.

10. The laser irradiation device according to claim 8, wherein the optical system includes an attenuator that variably attenuates the power of the laser light, and the control unit performs control including adjusting the attenuation rate of the laser light in the attenuator when it determines that the processing by the laser light is abnormal.

11. The laser irradiation device according to claim 5, wherein the optical system comprises a second detection unit, the second detection unit comprises a second mirror that transmits a portion of the laser light and propagates by reflecting the remainder, and a first profiler that receives the laser light propagated from the second mirror and detects a first profile of the laser light, the first profiler is configured to output the first profile to the control unit, and the control unit performs control that includes calculating at least one characteristic of the laser light based on the first profile while performing control to irradiate the target with the laser light.

12. The laser irradiation device according to claim 11, wherein the first detection unit comprises a beam splitter for spectrally analyzing the laser light and a second profiler, the beam splitter is configured to propagate a portion of the laser light to the photoelectric element and the remainder to the second profiler, and the second profiler detects a second profile of the laser light by receiving the laser light propagated from the beam splitter.

13. The laser irradiation apparatus according to claim 12, wherein the second profiler is configured to output the second profile to the control unit, and the control unit performs control that includes calculating the diffusion angle of the laser light based on the first profile and the second profile while performing control to irradiate the target with the laser light.

14. The laser irradiation apparatus according to claim 13, wherein the optical system comprises an expander for variably adjusting the diffusion angle of the laser light, and the control unit performs control including adjusting the diffusion angle in the expander based on the diffusion angle calculated based on the first profile and the second profile.

15. The laser irradiation device according to claim 6, wherein the optical system comprises a third detection unit and a fourth detection unit, the third detection unit comprises a third mirror that propagates by transmitting a portion of the laser light and reflecting the remainder, and a third profiler that receives the laser light propagated from the third mirror and detects a third profile of the laser light, the fourth detection unit comprises a fourth mirror that propagates by transmitting a portion of the laser light and reflecting the remainder, and a fourth profiler that receives the laser light propagated from the fourth mirror and detects a fourth profile of the laser light, and the control unit performs control including calculating the direction of propagation of the laser light based on the third profile and the fourth profile.

16. The laser irradiation apparatus according to claim 5, wherein the irradiation target is a polymerized substrate in which a first substrate and a second substrate are joined, and the apparatus comprises a substrate holding portion for holding the polymerized substrate.

17. A laser irradiation method using a laser irradiation device, wherein the laser irradiation device comprises a laser oscillator, an optical system for propagating laser light emitted from the laser oscillator, and a lens for irradiating a target with the laser light propagated from the optical system, the optical system comprises a first detection unit, the first detection unit comprises a photoelectric element for receiving the laser light and performing photoelectric conversion, and an oscilloscope for receiving an electrical signal from the photoelectric element and outputting a waveform of voltage change over time, and the laser irradiation method comprises calculating at least one characteristic of the laser light based on the waveform while irradiating the target with the laser light.

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