CN103372720A - Laser processor and laser processing method - Google Patents

Abstract

The invention provides a laser processor and a laser processing method, and uniform laser processing can be done whatever the laser irradiated surface state of a processed object is. The laser processor that applies laser processing to the processed object is characterized in comprising a chunk table that holds the processed object; a laser beam irradiation member that includes a laser oscillator and a processing head, wherein the processing head a condenser lens that condenses laser beam oscillated by the laser oscillator; a reflected light amount detection member that detects reflected light amount of the laser beam that is irradiated from the laser beam irradiation member to the processed object held on the chunk table; and an output adjusting member that adjusts output of the laser beam oscillated by the laser oscillator based on the reflected light amount detected by the reflected light amount detection member.

Description

Laser processing device and laser processing method

technical field

The present invention relates to a laser processing device and a laser processing method for performing laser processing on a workpiece such as a semiconductor wafer. the

Background technique

Wafers such as silicon wafers and sapphire wafers, whose surface is divided by dividing lines to form multiple devices such as ICs, LSIs, and LEDs, are divided into individual devices by processing equipment, and the divided devices are widely used in mobile phones, personal computers, etc. kind of electronic equipment. the

A dicing method using a cutting device called a dicing machine is widely used for dividing a wafer. In this dicing method, a cutting blade with abrasive grains such as diamond fixed by metal or resin and having a thickness of about 30 μm cuts into the wafer while rotating at a high speed of about 30,000 rpm, thereby cutting the wafer and dividing it into individual device chips. the

On the other hand, in recent years, a method of dividing a wafer into individual device chips using a laser beam has been developed and put into practical use. As a method of dividing a wafer into individual device chips using a laser beam, there are known first and second processing methods described below. the

The first processing method is a method (for example, refer to Japanese Patent No. 3408805): the laser beam with a wavelength (for example, 1064nm) that is transparent to the wafer is positioned at the center of the wafer corresponding to the planned dividing line. Inside, the modified layer is formed inside the wafer by irradiating the laser beam along the planned dividing line, and then an external force is applied to the wafer by the dividing device, and the wafer is divided into individual device chips with the modified layer as the starting point for dividing. the

The second processing method is a method as follows (for example, refer to Japanese Patent Application Laid-Open No. 10-305420): irradiating a laser beam with an absorbing wavelength (for example, 355 nm) on the laser beam corresponding to the planned division line. In the region, processing grooves are formed by cutting, and then external force is applied to divide the wafer into individual device chips with the processing grooves as the starting point. the

Compared with the dicing method using a dicing machine, the processing method using a laser beam can increase the processing speed and can be processed relatively easily even for wafers composed of high-hardness materials such as sapphire or SiC. the

In addition, the processing method using a laser beam has the following advantages: Since the modified layer or processing groove can be formed in a narrow width such as 10 μm or less, the number of wafers per wafer can be increased compared with the case of processing by a dicing method. The amount of equipment obtained. the

In addition, an oxide film or a nitride film remains on the back surface of the semiconductor wafer before the back surface is ground by a grinding apparatus. In addition, there are semiconductor wafers with a Low-k film formed on the surface or wafers with a metal film formed on the back surface. the

When laser processing is performed by irradiating laser beams to these workpieces with a film, a part of the irradiated laser beam is reflected by the film. The reflectance differs depending on the type or thickness of the film, and the reflectance varies for each workpiece, and the reflectance also varies within one workpiece. the

The first processing method is to form a modified layer inside the workpiece using a wavelength that is transparent to the workpiece, and the second processing is to perform cutting processing on the workpiece using an absorptive wavelength to the workpiece In the case of the method, if the reflectance of the workpiece is large, the light quantity of the transmitted or absorbed laser beam decreases, so it is also necessary to increase the output of the irradiated laser beam to implement desired laser processing. the

[Patent Document 1] Japanese Patent No. 3408805

[Patent Document 2] Japanese Patent Application Laid-Open No. 10-305420

[Patent Document 3] Japanese Patent Laid-Open No. 2009-021476

[Patent Document 4] Japanese Unexamined Patent Publication No. 2010-245172

In the case where the reflectance is different for each workpiece, when laser processing is performed on multiple workpieces under a single processing condition, there is a problem that laser processing grooves formed between the workpieces by irradiation of the laser beam There is a difference in the depth of the laser beam, or a difference in the modified layer formed by the irradiation of the laser beam. the

In addition, if there is a difference in reflectance within one workpiece, when laser processing is performed under a single processing condition, there is a problem that the depth of the laser-processed groove formed by irradiation of the laser beam varies depending on the area, or the depth of the laser-processed groove formed by The modified layer formed by irradiation of the laser beam produces a difference. the

Contents of the invention

The present invention has been made in view of the above facts, and an object of the present invention is to provide a laser processing device and a laser processing method capable of performing uniform laser processing regardless of the state of a laser-irradiated surface of a workpiece. the

According to the first aspect of the invention, there is provided a laser processing device that performs laser processing on a workpiece, the laser processing device is characterized in that it includes: a chuck table that holds the workpiece; a laser beam irradiation member that includes a laser beam an oscillator and a processing head, the processing head having a condensing lens that condenses the laser beam oscillated from the laser oscillator; a reflected light amount detecting member that detects the amount of light irradiated from the laser beam irradiating member to the an amount of reflected light of the laser beam on the workpiece on the chuck table; and output adjustment means for adjusting an output of the laser beam oscillated from the laser oscillator based on the amount of reflected light detected by the reflected light amount detecting means. the

It is preferable that the laser processing apparatus further has a number of stages calculation means for calculating the number of stages implemented by the laser beam irradiation means along the thickness direction of the workpiece based on the amount of reflected light detected by the amount of reflected light detection means. Levels of laser processing. the

According to the third aspect of the invention, there is provided a laser processing method for performing laser processing on a workpiece, the laser processing method comprising: a holding step of holding the workpiece with a chuck table; and irradiating the reflected light amount with a laser beam a step of irradiating a laser beam from a laser beam irradiating member to the workpiece held on the chuck table under a first condition; a reflected light amount detecting step of processing the laser beam irradiated in the reflected light amount detecting laser beam irradiating step detecting the light quantity of the reflected light reflected from the upper surface of the object; The output of the irradiated laser beam irradiates the workpiece held by the chuck table with the laser beam from the laser beam irradiating means under the second condition, thereby performing laser processing on the workpiece. the

Preferably, the laser processing method further includes a step of calculating the number of stages, and in the step of calculating the number of stages, based on the amount of reflected light detected in the amount of reflected light detected in the step of detecting the amount of reflected light, the number of stages of laser processing performed along the thickness direction of the workpiece is calculated. In the laser processing step, multi-stage laser processing is performed along the thickness direction of the workpiece based on the number of stages calculated in the step of calculating the number of stages. the

Since the laser processing apparatus of the present invention has reflected light amount detecting means for detecting the light amount of reflected light reflected from the upper surface of the workpiece and output adjusting means for adjusting the output of the laser beam to an optimum based on the detected reflected light amount, Uniform laser processing can be performed regardless of the state of the laser-irradiated surface of the workpiece. the

The laser processing method of the present invention has a step of irradiating a laser beam for detecting the amount of reflected light, a step of detecting the amount of reflected light for detecting the amount of reflected light, setting the output of the laser beam based on the amount of reflected light detected in the step of detecting the amount of reflected light, and executing the laser beam on the workpiece. In the laser processing step of laser processing, uniform laser processing can be performed on the workpiece regardless of the state of the laser-irradiated surface of the workpiece. the

Description of drawings

FIG. 1 is a perspective view of a laser processing device. the

FIG. 2 is a block diagram of an optical system of a laser beam irradiation unit. the

Fig. 3 is a front perspective view of a semiconductor wafer. the

4 is an exploded perspective view showing a state in which the surface side of the semiconductor wafer is adhered to an adhesive tape attached to the ring frame on the outer peripheral portion. the

Fig. 5 is a partial sectional side view showing a holding step. the

6 is a partial cross-sectional side view showing a step of irradiating a reflected light amount with a laser beam. the

Fig. 7 is a graph showing the correlation between the reflectance of the workpiece and the appropriate pulse energy. the

8 is a partial cross-sectional side view showing a laser processing step of forming a modified layer inside a wafer. the

9 is a partial cross-sectional side view showing a step of irradiating a reflected light amount detection laser beam on the wafer surface side. the

10 is a partial cross-sectional side view showing an embodiment in which laser processing is performed while detecting the amount of reflected light. the

Fig. 11 is a perspective view illustrating a back grinding step. the

Label description

11: Semiconductor wafer

13: Split scheduled line

15: device

17: oxide film

19: modified layer

28: chuck table

34: Laser beam irradiation unit

36: processing head

38: camera unit

62: Laser oscillation unit

64: Laser oscillator

66: Repeat frequency setting unit

68: Output adjustment unit

69: Laser Beam

71: reflected light

74: Concentrating lens

76: half-transparent mirror

78: Reflected light detector

Detailed ways

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1 , there is shown an external perspective view of a laser processing device according to an embodiment of the present invention. The laser processing device 2 includes a first slider 6 mounted on the stationary base 4 so as to be movable in the X-axis direction. the

The first slider 6 is moved along a pair of guide rails 14 in the X-axis direction, which is the machining feed direction, by a machining feed member 12 composed of a ball screw 8 and a pulse motor 10 . the

The second slider 16 is mounted on the first slider 6 so as to be movable in the Y-axis direction. That is, the second slider 16 moves along a pair of guide rails 24 in the Y-axis direction which is the index feeding direction by the index feeding member 22 composed of the ball screw 18 and the pulse motor 20 . the

A chuck table 28 is mounted on the second slider 16 via a cylindrical support member 26 , and the chuck table 28 is movable in the X-axis direction and the Y-axis direction by the machining feed unit 12 and the index feed unit 22 . A clamp 30 for clamping the semiconductor wafer sucked and held on the chuck table 28 is provided on the chuck table 28 . the

A column 32 is erected on the stationary base 4 , and a laser beam irradiation unit 34 is attached to the column 32 . The laser beam irradiation unit 34 includes a laser oscillation unit 62 shown in FIG. 2 housed in the casing 35 and a processing head 36 attached to the front end of the casing 35 . the

As shown in FIG. 2 , the laser oscillation unit 62 includes: a laser oscillator 64 that oscillates YAG laser light or YVO4 laser light; and a repetition rate setting unit 66 . Although not particularly shown in the figure, the laser oscillator 64 has a Brewster window, and the laser beam emitted from the laser oscillator 64 is a linearly polarized laser beam. the

An imaging unit 38 is arranged at the front end portion of the housing 35 to be aligned with the machining head 36 in the X-axis direction to detect a machining area to be laser-machined. The imaging unit 38 includes an imaging element such as a general CCD that images the processing region of the semiconductor wafer with visible light. the

The imaging unit 38 also includes: an infrared irradiation member for irradiating infrared rays to the semiconductor wafer; an optical system for capturing infrared rays irradiated by the infrared irradiation member; and an infrared imaging unit for outputting an electrical signal corresponding to the infrared rays captured by the optical system. An infrared imaging device such as an infrared CCD is configured, and captured image signals are sent to a controller (control means) 40 . the

The controller 40 is composed of a personal computer, and has: a central processing unit (CPU) 42 that performs calculation processing according to a control program; a read-only memory (ROM) 44 that stores control programs, etc.; a readable and writable random memory that stores calculation results, etc. access memory (RAM) 46; counter 48; input interface 50; and output interface 52. the

Reference numeral 56 is a processing feed amount detection member composed of a linear scale 54 arranged along the guide rail 14 and an unillustrated reading head arranged on the first slider 6, and the detection signal of the processing feed amount detection member 56 is input to the control unit. The input interface 50 of the device 40. the

Reference numeral 60 is an index feed amount detecting member composed of a linear scale 58 arranged along the guide rail 24 and an unillustrated reading head arranged on the second slider 16, and the detection signal of the index feed amount detecting member 60 is input. to the input interface 50 of the controller 40 . the

The image signal captured by the camera unit 38 is also input to the input interface 50 of the controller 40 . On the other hand, control signals are output from the output interface 52 of the controller 40 to the pulse motor 10, the pulse motor 20, the laser beam irradiation unit 34, and the like. the

Referring to FIG. 2 , the optical system of the laser beam irradiation unit 34 according to the embodiment of the present invention is shown. A reflection mirror 72 and a condenser lens 74 are housed in a casing 70 of the machining head 36 . In addition, a half mirror (beam splitter) 76 is arranged between the reflection mirror 72 and the condensing lens 74 . the

The laser beam 69 oscillated from the laser beam oscillation unit 62 and further adjusted to a predetermined power by the output adjustment unit 68 is reflected by the reflector 72 of the processing head 36, and a part of it passes through the half mirror 76 and is irradiated by the condenser lens 74 to the wafer 11 as the workpiece. the

The reflected light 71 reflected by the upper surface of the wafer 11 is collected by the condenser lens 74, part of which is reflected by the half mirror 76, and the reflected light amount detector 78 composed of a light receiving element such as a light emitting diode detects the amount of reflected light. Based on this amount of reflected light, the controller 40 controls the laser beam oscillation unit 62 and the output adjustment unit 68 as described in detail later. the

The half-mirror 76 may also be arranged between the condenser lens 74 and the workpiece (wafer) 11, but the configuration of disposing the half-mirror 76 on the upstream side of the condenser lens 74 can only The reflected light reflected by the upper surface of the wafer 11 is condensed by the condensing lens 74 and is incident on the half mirror 76, so this configuration is preferable in detecting the amount of reflected light. the

Referring to FIG. 3 , there is shown a front perspective view of a semiconductor wafer 11 which is one of workpieces to be processed in the laser processing method of the present invention. The semiconductor wafer 11 is composed of, for example, a silicon wafer with a thickness of 700 μm, and a plurality of dividing lines 13 are formed in a grid pattern on the surface 11a, and devices such as ICs and LSIs are respectively formed in the regions divided by the plurality of dividing lines 13. 15. As shown in FIG. 4, on the back surface 11b of the semiconductor wafer 11, an oxide film 17 made of SiO2 is formed. the

The object to be processed in the laser processing method of the present invention is not limited to the semiconductor wafer 11 shown in FIG. 3 , but also includes an object having an oxide film, a nitride film, a metal film, a Low-k film, or the like on the surface or back. the

When implementing the laser processing method of the present invention, as shown in FIG. The back surface 11b becomes an upper side. the

In this way, as shown in FIG. 5 , the chuck table 28 of the laser processing apparatus 2 attracts and holds the semiconductor wafer 11 via the adhesive tape T, and the annular frame F is clamped and fixed by the clamp 30 . the

Next, as shown in FIG. 6 , a laser beam irradiating step for detecting the amount of reflected light is performed in which the processing head 36 of the laser beam irradiating unit 34 irradiates the wafer 11 held on the chuck table 28 with the laser beam 69 under the first condition. the

Calibration for detecting the planned dividing line 13 to be laser-processed is performed before the laser beam irradiation step for detecting the amount of reflected light is performed. In other words, the wafer 11 is photographed from the rear surface 11b side by the infrared camera of the imaging unit 38, and the planned dividing line 13 elongated in the first direction and the line perpendicular to the first direction are detected by image processing such as well-known pattern matching. A planned dividing line 13 extending in the second direction. the

As another embodiment, the holding surface of the chuck table 28 may be formed of a transparent member, and the wafer 11 may be photographed by a camera disposed below the chuck table 28 to perform calibration. the

In addition, before detecting the amount of reflected light of the wafer 11, the present invention prepares one or more reference workpieces with known reflectance in advance, uses the reference workpiece to detect the amount of reflected light, and uses the amount of reflected light at this time as reference data to store in the controller 40. of RAM46. the

In this step of irradiating the reflected light amount with a laser beam, as shown in FIG. The laser beam 69 is irradiated, and the reflected light 71 is detected by a reflected light amount detector 78 . the

For example, the reflected light amount detection laser beam is irradiated to any planned dividing line 13 , a plurality of dividing lines 13 , or all planned dividing lines 13 of the wafer 11 to detect the reflected light amount. the

The irradiation conditions of the reflected light amount detection laser beam when the modified layer is formed inside the wafer 11 by irradiation of the laser beam 69 are as follows, for example. the

Light source: LD excitation Q switch Nd: YVO4 pulsed laser

Wavelength: 1064nm

Repetition frequency: 100kHz

Average output: 0.1W

Processing feed speed: 400mm/s

In the laser beam irradiation step for detecting the amount of reflected light, when the laser beam 69 is irradiated to the back surface 11b of the wafer 11, the reflected light 71 reflected by the back surface 11b on which the oxide film 17 is formed is condensed by the condensing lens 74 shown in FIG. A part thereof is reflected by the half mirror 76 and enters a reflected light amount detector 78 composed of a light receiving element to detect the amount of reflected light reflected by the back surface 11b of the wafer 11 . The reflectance of the back surface 11 b of the wafer 11 is calculated from the detected reflected light quantity and the reflected light quantity of a reference workpiece whose reflectance is known and stored in the RAM 46 . the

The ROM 44 of the controller 40 stores a plurality of correlative maps as shown in FIG. 7 , which represent, for example, the correlation between the reflectance and the appropriate pulse energy for each type of workpiece and each type of film. 73. Accordingly, pulse energy appropriate for the reflectance can be obtained from these correlograms. the

Based on appropriate pulse energy, the average output and repetition frequency of the laser beam oscillated from the laser vibrator 64 are adjusted. For example, when the reflectivity is 50%, according to the correlation diagram in Figure 7, the appropriate pulse energy is determined to be 20uJ. Therefore, according to pulse energy (J)=average output (W)/repetition frequency (Hz), for example, if the repetition frequency is set to 100 Hz, the average output is 2W. the

Since the maximum power of the laser oscillator 64 is insufficient due to the reflectivity, a sufficient modified layer cannot be formed inside the wafer 11 by one irradiation of the laser beam. Thus, based on the reflected light amount detected in the reflected light amount detecting step, a multi-stage modified layer is formed along the thickness direction of the wafer 11 . The number of stages calculation means that calculates the necessary number of stages based on the amount of reflected light is stored in the ROM 44 of the controller 40 . the

After the detection of the reflected light amount is carried out, the following laser processing step is carried out: the output of the laser beam irradiated by the laser beam irradiation unit 34 is set based on the reflected light amount detected in the reflected light amount detection step, and the processing head 36 of the laser beam irradiation unit 34 to The second condition is to irradiate the wafer 11 held on the chuck table 28 with a laser beam to form the modified layer 19 inside the wafer 11 . the

As shown in FIG. 8, in this laser processing step, while the chuck table 28 is being processed and fed in the direction of the arrow X1, the laser beam 69 is irradiated with the second condition from the processing head 36 of the laser beam irradiation unit 34, and the laser beam 69 is irradiated on the wafer. Modified layer 19 is formed inside 11. the

While indexing the chuck table 28 in the Y-axis direction, the same modified layer 19 is gradually formed inside the wafer 11 along the planned dividing line 13 extending in the first direction. Next, after the chuck table 28 is rotated by 90 degrees, the same modified layer 19 is formed along the planned dividing line 13 extending in the second direction. the

When the divisibility is low due to the thickness and material of the wafer 11, the multi-level modifying layer 19 is formed inside the wafer. In addition, when the reflectivity of the wafer 11 is high, the maximum power of the laser beam oscillator 64 is too low, and a sufficient modified layer 19 cannot be formed inside the wafer 11 by one irradiation of the laser beam, the inside of the wafer 11 A multilevel modifying layer 19 is formed. the

The laser processing conditions in this modified layer forming step are set as follows, for example. the

Light source: LD excitation Q switch Nd: YVO4 pulsed laser

Wavelength: 1064nm

Repetition frequency: 100kHz

Average output: 2.0W

Processing feed speed: 400mm/s

Referring to FIG. 9 , there is shown a partial cross-sectional side view illustrating a step of irradiating a reflected light amount with a laser beam when ablation processing is performed on a wafer 11 . For example, when performing ablation processing on the Low-k film formed on the surface 11 a of the wafer 11 , the laser beam 69 is incident on the surface 11 a side of the wafer 11 . Also, the light quantity of the reflected light 71 reflected by the surface 11 a is detected by the reflected light quantity detector 78 . the

In the ablation process, similar to the above-mentioned modified layer forming process, the reflected light amount detection laser beam is irradiated to any planned dividing line 13 , a plurality of dividing lines 13 , or all planned dividing lines 13 of the wafer 11 to detect the reflected light amount. the

Laser beam irradiation conditions at the time of excision processing are set as follows, for example. the

Light source: LD excitation Q switch Nd: YVO4 pulsed laser

Wavelength: 355nm (the third harmonic of YVO4 pulsed laser)

Repetition frequency: 200kHz

Average output: 0.1W

Processing feed speed: 200mm/s

In the cutting process, a laser processing step of setting the output of the laser beam irradiated by the laser beam irradiation unit 34 based on the reflected light amount detected in the reflected light amount detection step is performed after the reflected light amount detection step is performed, A laser beam is irradiated from the processing head 36 of the laser beam irradiation unit 34 to the surface 11a of the wafer 11 held on the chuck table 28 under the second condition, and the cutting line 13 of the wafer 11 is subjected to cutting processing to form laser processing grooves. the

The laser processing conditions in this excision processing are set as follows, for example. the

Light source: LD excitation Q switch Nd: YVO4 pulsed laser

Wavelength: 355nm (the third harmonic of YVO4 pulsed laser)

Repetition frequency: 200kHz

Average output: 1W

Processing feed speed: 200mm/s

Due to the reflectivity of the surface 11a of the wafer 11 and the maximum power of the laser oscillator 64, in the case of ablation processing, the condensing point of the condensing lens 74 is also changed in the thickness direction of the wafer 11 to form a multi-stage laser processing groove. . The number of stages at this time is calculated by the number of stages calculation means stored in the ROM based on the reflectance detected in the reflectance detection step. the

In the second embodiment of the laser processing method of the present invention, the laser processing step may be performed simultaneously with the reflected light amount detection step. That is, as shown in FIG. 10 , while the chuck table 28 is being processed and fed in the direction of the arrow X1, the laser beam 69 is irradiated from the processing head 36 of the laser beam irradiation unit 34, and the back surface of the wafer 11 is detected by the reflected light amount detector 78. The reflected light amount of the reflected light 71 reflected by 11b. the

Based on the amount of reflected light, controller 40 causes output adjustment unit 68 to perform feedback control, and forms modified layer 19 inside wafer 11 with laser beam 69 having an optimum output based on the amount of reflected light. the

Even in the case of excision processing, the output adjustment unit 68 can be controlled according to the amount of reflected light, and the excision processing can be performed while irradiating the laser beam 69 of optimum power from the processing head 36 . After the modified layer 19 or the laser-processed grooves are formed on the wafer 11, a division step of applying an external force to the wafer 11 to divide the wafer 11 into individual chips is performed. the

In the present embodiment, after the modified layer 19 is formed inside the wafer 11 along all the planned division lines 13 , a backside grinding step of grinding the backside 11 b of the wafer 11 is performed. As shown in FIG. 11, in this backside grinding step, the backside 11b of the wafer 11 held by the chuck table 96 of the grinding device is ground with a grinding stone 94, and the wafer 11 is ground by the pressing force during grinding. Divided into individual chips. the

In FIG. 11 , the grinding unit 82 is composed of a main shaft 84 , a grinding wheel mount 86 fixed to the front end of the main shaft 84 , and a grinding wheel 88 detachably mounted on the grinding wheel mount 86 by a plurality of screws 90 . The grinding wheel 88 is formed by fixing a plurality of grinding stones 94 to the outer periphery of the lower end portion of the annular base 92 . the

In this back grinding step, while the chuck table 96 is rotated at, for example, 300 rpm in the direction of the arrow a, the grinding wheel 88 is rotated at, for example, 6000 rpm in the direction of the arrow b, and the grinding unit feed mechanism is operated to make the grinding The sharpening stone 94 contacts the back surface 11 b of the wafer 11 . the

Then, the back surface 11b of the wafer 11 is ground while the grinding wheel 88 is being ground and fed downward at a predetermined grinding feed speed. The thickness of the wafer 11 is measured by a contact or non-contact thickness gauge, and the wafer 11 is finished to a desired thickness, for example, 50 μm. the

During the grinding, since the modified layer 19 is formed inside the wafer 11 along the dividing line 13, the wafer 11 is divided into individual chips by using the modified layer 19 as a division starting point by the pressing force during grinding. the

Here, in the case of a workpiece with low divisibility, a division step of dividing the workpiece by applying an external force is performed before performing back grinding. Alternatively, after performing back grinding, a dividing step of dividing the workpiece by applying an external force is performed. the

In the above-mentioned embodiment, after the modified layer 19 is formed on a thicker (700 μm) wafer, the rear surface 11 b of the wafer 11 is ground to make the wafer thinner, and the modified layer 19 is divided by the pressing force during grinding. The starting point is to divide the wafer into individual chips, but it is also possible to grind the backside 11b in advance and form the modified layer 19 or laser-processed grooves on the thinned wafer 11 . Alternatively, the wafer 11 may be fully cut by irradiating the wafer 11 with a laser beam having an absorbing wavelength. the

Claims (4)

1. laser processing device, it implements Laser Processing to machined object,

This laser processing device is characterised in that to have:

Chuck table, it keeps machined object;

The laser beam irradiation member, it comprises laser oscillator and processing head, and this processing head has collector lens, and this collector lens is assembled the laser beam that vibrates from this laser oscillator;

The reflection light quantity detection means, it detects the reflection light quantity that shines the laser beam of the machined object that remains in this chuck table from this laser beam irradiation member; And

Member is adjusted in output, and it is based on by the detected reflection light quantity of this reflection light quantity detection means, adjusts from the vibrate output of the laser beam that of this laser oscillator.

2. laser processing device according to claim 1, wherein,

This laser processing device also has progression and calculates member, this progression calculates member based on by the detected reflection light quantity of described reflection light quantity detection means, calculates and utilizes this laser beam irradiation member to implement the progression of multistage Laser Processing along the thickness direction of machined object.

3. a laser processing is implemented Laser Processing to machined object,

This laser processing is characterised in that to have:

Keep step, utilize chuck table to keep machined object;

Reflection light quantity detects uses the laser beam irradiation step, with first condition from the laser beam irradiation member to remaining in the machined object illuminating laser beam of this chuck table;

The reflection light quantity detecting step, the catoptrical reflection light quantity after the laser beam that shines machined object in detecting with the laser beam irradiation step at this reflection light quantity reflected by the machined object upper surface detects; And

The Laser Processing step, after having implemented this reflection light quantity detecting step, based on detected reflection light quantity in this reflection light quantity detecting step, setting utilizes the output of the laser beam of this laser beam irradiation member irradiation, with second condition from this laser beam irradiation member to remaining in the machined object illuminating laser beam of this chuck table, come machined object is implemented Laser Processing.

4. laser processing according to claim 3, wherein,

This laser processing also has the progression calculation procedure, in this progression calculation procedure, based on detected reflection light quantity in described reflection light quantity detecting step, calculates the progression of implementing multistage Laser Processing along the thickness direction of machined object,

In described Laser Processing step, based on the progression that in this progression calculation procedure, calculates, implement multistage Laser Processing along the thickness direction of machined object.

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