TW201910038A - Laser processing method - Google Patents

Abstract

The subject of the present invention is to provide a laser processing method capable of easily determining whether a workpiece can be formed with a modified layer inside under the processing conditions before performing the laser processing. According to this invention, the solution at least comprises the following steps: a first detection step of providing a condenser of a laser beam irradiation mechanism to face the power meter and irradiating a laser beam to detect a first power; a second detection step of positioning the workpiece between the condenser and the power meter and irradiating the laser beam to detect a second power; a transmittance calculating step of calculating an index indicating a transmittance of the workpiece from the first power and the second power; a modified layer forming determination step of determining whether a modified layer can be formed inside the workpiece from the index indicating the transmittance; and a modified layer forming step of forming a modified layer by positioning a condensing point of the laser beam inside the workpiece determined to be capable of forming the modified layer by the modified layer forming determination step to irradiate to form a modified layer. Accordingly, this invention can easily determine whether a workpiece can be formed with a modified layer and can carry out the laser processing truly forming the modified layer.

Description

Laser processing method

FIELD OF THE INVENTION The present invention relates to a laser processing method capable of reliably forming a modified layer on a workpiece.

BACKGROUND OF THE INVENTION A wafer divided by a predetermined division line to form a plurality of devices such as ICs and LSIs on the front side is divided into individual devices by a dicing device, a laser processing device, and the like. Personal computer and other electrical equipment.

Laser processing devices are roughly classified into the following types: a type in which a light-condensing point of laser light having a wavelength of transmissiveness to a part to be processed is positioned inside the object to be irradiated to form a modified layer, and internal processing is performed (Refer to, for example, Patent Document 1), and a type in which an abrasion process is performed by positioning a condensing point of laser light having a wavelength that is absorptive to the object on the upper surface of the object to be irradiated (see, for example, Patent Document 2) ). Prior Art Literature Patent Literature

Patent Document 1: Japanese Patent No. 3408805 Patent Document 2: Japanese Patent Laid-Open No. 10-305420

SUMMARY OF THE INVENTION The problem to be solved by the invention is as described above. A type of mine that performs internal processing by locating a light-condensing point of laser light having a wavelength of transmissivity to a part to be processed inside the object to be irradiated to form a modified layer. In the laser processing, for example, a laser processing is performed using a silicon (Si) wafer as a workpiece. However, when a silicon wafer is formed, a so-called doping in which a small amount of impurities are added in order to change the physical properties of the crystal is performed. Depending on the manufacturer of the substrate on which the silicon wafer is formed, or the type of devices formed on the silicon wafer, the type of the substance to be doped or the amount of the substance to be doped will be different. As a laser light having a wavelength that is transmissive to silicon, there are still cases in which the irradiated laser light is not sufficiently transmitted through the object to be processed, even if laser processing is performed in accordance with a preset processing condition. Poor processing.

In addition, it is not limited to the above-mentioned case where the degree of transmittance changes due to different doping. For example, when a period of time has passed after the silicon wafer is manufactured, an oxide film or the like may be formed on the surface and the like. Changes in transmittance cause the same problem. Such problems are not limited to silicon wafers, and may also occur on processed objects made of other materials.

The present invention has been made in view of the above-mentioned facts, and its main technical problem is to provide a laser processing method that can easily determine whether it can be formed internally under the processing conditions before the laser processing is implemented. The object to be modified. Means to solve the problem

In order to solve the above-mentioned main technical problems, according to the present invention, a laser processing method using a laser processing device may be provided. The laser processing device is provided with at least: a holding mechanism to hold a workpiece, and a laser light irradiation mechanism. Equipped with a condenser, which condenses a spot of laser light having a wavelength of transmissivity to an object to be processed held by the holding mechanism, is positioned inside the object to be irradiated to form a modified layer And a processing feed mechanism for processing and feeding the holding mechanism opposite to the laser light irradiation mechanism, the laser processing method is composed of at least the following steps: a first detection step for the laser light irradiation mechanism The condenser is opposite to the power meter to irradiate the laser light to detect the first power; the second detection step is to position the object to be processed between the condenser and the power meter to irradiate the laser light to detect the second power Power; transmittance calculation step, calculating an index representing the transmittance of the processed object from the first power and the second power; determining step of forming a modified layer, judging whether or not from the index representing the transmittance A reformed layer can be formed inside the processed object; and a reformed layer forming step, positioning the focused point of the laser light on the processed object determined by the reformed layer formation determining step to be capable of forming a reformed layer. The interior is irradiated to form a modified layer.

The power meter is arranged adjacent to the work clamp, and the concentrator and the holding mechanism can be moved relatively to implement the first detection step.

It can also be set to hold the workpiece on the work clamp so as to reach the power meter beyond the work clamp of the holding mechanism, and implement the second detection step. In addition, it can be assumed that the object to be processed is a silicon wafer, and the wavelength of the laser light is near infrared. Invention effect

The laser processing method of the present invention is a laser processing method using a laser processing device. The laser processing device is provided with at least: a holding mechanism to hold a workpiece, and a laser light irradiation mechanism with a condenser. The concentrator is a condensing point of laser light having a wavelength of transmissivity to a workpiece held by the holding mechanism, is positioned inside the workpiece to be irradiated to form a modified layer; and a processing feed mechanism , Processing and feeding the holding mechanism opposite to the laser light irradiation mechanism, the laser processing method is composed of at least the following steps: a first detection step, making the condenser and power of the laser light irradiation mechanism A meter is used to irradiate the laser light to detect the first power; a second detection step is to position the object to be processed between the concentrator and the power meter to irradiate the laser light to detect the second power; the transmittance calculation step , Calculating an index representing the transmittance of the object from the first power and the second power; a step of determining a reformed layer formation, judging from the index representing the transmittance whether a modification can be formed inside the object And a reforming layer forming step, for the processed object determined to be able to form a reforming layer by the reforming layer formation determining step, locating the light-condensing point of the laser light inside to form a reforming layer, by This makes it possible to easily determine whether or not the object to be processed can form a modified layer, and it is possible to perform laser processing capable of reliably forming the modified layer.

Modes for Carrying Out the Invention The laser processing method according to the present invention will be described in detail below with reference to the attached drawings.

FIG. 1 shows an overall perspective view of a laser processing apparatus 2 for implementing a laser processing method constructed in accordance with the present invention, and a perspective view of a silicon wafer (100, 110) as a workpiece. In addition, the processed object for detecting transmittance by the present invention may be a silicon wafer 100 (refer to (a) in the figure, hereinafter referred to as a "fake wafer") before a device or the like is formed on the front surface, or it may be A silicon wafer 110 having a device 114 is formed in a region defined by a predetermined division line 112 on the front surface 110a of the dummy wafer 100 ((b) in the figure).

The laser processing apparatus 2 shown in FIG. 1 includes a holding mechanism 22 for holding a workpiece, a moving mechanism 23 disposed on the stationary base 2a and moving the holding mechanism 22, and a laser light irradiation mechanism 24 for holding the object to be held. The object to be processed of the holding mechanism 22 is irradiated with laser light; and the frame 50 is composed of a vertical wall portion 51 and a horizontal wall portion 52. The vertical wall portion 51 is erected on the stationary base in the Z direction indicated by the arrow Z. On the side of the moving mechanism 23 on the table 2a, the horizontal wall portion 52 extends from the upper end portion of the vertical wall portion 51 in the horizontal direction. An optical system of a laser light irradiation mechanism 24 constituting a main part of the laser processing apparatus 2 of the present invention is built into the horizontal wall portion 52 of the frame 50, and a constituent laser is disposed on the lower surface side of the front end portion of the horizontal wall portion 52. The light ray illuminates the condenser 241 of the mechanism 24, and a photographing mechanism 26 is arranged at a position adjacent to the condenser 241 in a direction indicated by an arrow X in the figure. The imaging mechanism 26 includes a general imaging element (CCD) for imaging with visible light, an infrared irradiation mechanism for irradiating an object with infrared rays, an optical system for capturing infrared rays emitted by the infrared irradiation mechanism, and an optical system corresponding to An imaging device (infrared CCD) that outputs electrical signals of infrared rays captured by this optical system.

The holding mechanism 22 includes a rectangular X-direction movable plate 30 mounted on the base 2a in the X direction indicated by the arrow X in the figure, and freely moved in the Y direction indicated by the arrow Y in the figure. A rectangular Y-direction movable plate 31 mounted on the X-direction movable plate 30, a cylindrical pillar 32 fixed to the upper surface of the Y-direction movable plate 31, and a rectangular cover plate 33 fixed to the upper end of the pillar 32. The cover plate 33 is provided with a work clamping table 34 extending upward through a long hole formed in the cover plate 33. The work clamping table 34 is a workpiece to be held in a circular shape. The rotation drive mechanism shown is rotatably configured. A suction holding mechanism made of a porous suction chuck 35 made of a porous material and extending substantially horizontally is arranged on the upper surface of the work chuck 34. The suction chuck 35 is connected to a suction mechanism (not shown) through a flow path passing through the stay 32. A power meter 36 is provided on the cover plate 33 and at a position adjacent to the work clamp table 34 in the X direction. The power meter 36 detects the power of the laser light irradiated from the laser light irradiation mechanism 24 (output ). The power meter 36 is connected to a control device 20 to be described later by a cable (not shown), and is composed of a plurality of light receiving elements. The plurality of light receiving elements are areas configured to receive the total light amount of the laser light to be measured. And output the power of the received laser light to the control device 20. The X direction is a direction indicated by an arrow X in FIG. 1, and the Y direction is a direction indicated by an arrow Y and is a direction orthogonal to the X direction. The planes defined by the X and Y directions are essentially horizontal.

The control device 20 is composed of a computer, and includes a central processing unit (CPU) that performs calculation processing according to a control program, a read-only memory (ROM) that stores a control program, and the like, and temporarily stores the detected detection values. Read and write random access memory (RAM), input interface, and output interface (such as the details shown).

The moving mechanism 23 is a mechanism controlled by the control device 20 and includes an X-direction moving mechanism 40 and a Y-direction moving mechanism 42. The X-direction moving mechanism 40 converts the rotary motion of the motor into a linear motion through a ball screw and transmits it to the X-direction movable plate 30, so that the X-direction movable plate 30 advances and retreats in the X direction along the guide track on the base 2a. The Y-direction moving mechanism 42 converts the rotary motion of the motor into a linear motion through a ball screw and transmits it to the Y-direction movable plate 31, so that the Y-direction movable plate 31 follows the guide track on the X-direction movable plate 30 in the Y direction. advance and retreat. In addition, although not shown in the drawings, the X-direction moving mechanism 40 and the Y-direction moving mechanism 42 are each provided with a position detection mechanism, so that the position in the X direction and the Y direction of the work clamp 34 can be accurately detected. And the rotation position in the circumferential direction, and the X-direction moving mechanism 40, the Y-direction moving mechanism 42, and a rotation driving mechanism (not shown) can be driven according to the signal indicated by the control device 20, so that the work clamp table 34 can be set. Correctly position to any position and angle. In addition, the entire laser processing apparatus 2 and the moving mechanism 23 are configured to be covered by a cover, a bellows, etc. (not shown), which are omitted for convenience of explanation, in a general processing state to prevent dust or dust. Wait to get inside.

The laser processing device 2 for carrying out the present invention is configured as described above, and the laser processing method of the present invention will be described below.

FIG. 2 is a flowchart showing steps of a laser processing method implemented by the present invention. The laser processing method of the present invention will be described with reference to this flowchart.

(First Detection Step) When implementing the laser processing method of the present invention, first, the first detection step (S1) is performed. In order to implement the first detection step, alignment of the power meter 36 and the condenser 241 of the laser light irradiation mechanism 24 arranged on the cover plate 33 is performed first. The alignment is controlled by the X-direction moving mechanism 40 and the Y-direction moving mechanism 42 that move the holding mechanism 22 in the X and Y directions, and the center position of the power meter 36 is captured by the imaging mechanism 26 and the position is detected. By moving the condenser 241 and the power meter 36 relatively, the condenser 241 and the power meter are relatively opposed. In addition, the alignment of the condenser 241 and the power meter 36 is not necessarily limited to the method implemented by using the imaging mechanism 26, and the irradiation of the laser light emitted from the condenser 241 can be visually confirmed by the operator Position one side.

When the alignment of the condenser 241 and the power meter 36 has been implemented, as shown in FIG. 3 (a), the laser light LB is oscillated by the laser oscillator (not shown) of the laser light irradiation mechanism 24, and The power meter 36 is irradiated from the condenser 241 to output the power of the laser beam LB to the control device 20. At this time, the light-condensing position P of the laser light LB is not a position that matches the height of the light-receiving element of the power meter 36, but is positioned upward (defocused) by a predetermined distance. Thereby, the power density of the condensing spot formed at the power meter 36 is not excessively increased to suppress deterioration of the power meter 36. The defocus amount of the laser beam LB is such that the total light amount of the laser beam LB radiated to the power meter 36 can be received by the power meter 36. The power of the laser beam LB radiated at this time should preferably be lower than the power when the workpiece is actually processed.

The irradiation conditions of the laser light irradiated in the first detection step can be set to, for example, the following. Wavelength: 1342nm Repetition frequency: 90kHz Average output: 1000mW

As can be understood from FIG. 3 (a), the power of the laser light detected in the first detection step is the power of the laser light LB radiated from the laser light irradiating mechanism 24, and in this embodiment , The detection is 1000mW (1W). The detected power is stored in the memory of the control device 20 as "first power (P1)". In addition, the power of a laser oscillator (not shown) mounted on the laser light irradiation mechanism 24 may be reduced due to changes over time, etc., or due to variations in the quality of the laser oscillator. By implementing this first detection step, the first power (P1) of the laser beam LB can be accurately detected.

(Second Detection Step) As described above, if the first detection step has been performed and the first power (P1) has been stored in the memory of the control device 20, the second detection step (S2) shown in FIG. 2 can be performed. Specifically, the dummy wafer 100 shown in FIG. 1 is prepared, and as shown in FIG. 3 (b), the dummy wafer 100 is positioned so as to cover the light receiving element of the power meter 36. At this time, it is desirable to place the dummy wafer 100 beyond the work clamp table 34 and reach the power meter 36, and activate a suction mechanism (not shown) connected to the suction chuck 35 to hold the dummy wafer 100 into Not offset. If the dummy wafer 100 has been positioned in this way, the power meter 36 can be irradiated with the laser light LB under the same irradiation conditions as in the first detection step described above. The dummy wafer 100 described above is a substrate of the silicon wafer 110 that is processed as a workpiece, and is produced from the same ingot and the same manufacturing process as the substrate of the silicon wafer 110. According to this, the transmittance of the substrate of the silicon wafer 110 can be known by knowing the transmittance of the dummy wafer 100.

When the laser beam LB is irradiated toward the power meter 36 with the dummy wafer 100 held as described above, the laser beam LB transmitted without being absorbed by the dummy wafer 100 is received by the power meter 36. In this embodiment, it is detected as 600 mW, and the detected power is stored in the memory of the control device 20 as "second power (P2)".

(Transmittance Calculation Step) As described above, if the first detection step (S1) and the second detection step (S2) have been performed, the transmittance calculation step (S3) shown in FIG. 2 can be performed. In this transmittance calculation step (S3), an index indicating the transmittance of the workpiece is calculated from the first power (P1 = 1000mW) and the second power (P2 = 600mW) stored in the control device 20. Specifically, the following calculations are performed. Transmittance (R) = (2nd power (P2) / 1st power (P1)) × 100 = (600 (mW) / 1000 (mW)) × 100 = 60 (%)

By performing the above-mentioned transmittance calculation step (S3), the transmittance (R = 60%) of the dummy wafer 100 in this embodiment can be calculated and stored in the memory of the control device 20. The transmittance (R) calculated in the transmittance calculation step (S3) is not limited as long as it is an index indicating the transmittance, and is not limited to the method of calculation by the above-mentioned calculation. For example, it may be an index for calculating the absorptivity of the laser light LB absorbed by the dummy wafer 100. When calculating the absorptivity, the value (P1-P2) of the first power (P1) minus the second power (P2) is used as the numerator, and the first power (P1) is used as the denominator. . This absorptance is an index showing a lower value when the transmittance is higher, and a higher value when the transmittance is lower, and it can be used substantially as an index showing the transmittance in the present invention.

(Modified layer formation determination step) If the above-mentioned transmittance calculation step (S3) has been performed, a modified layer formation determination step (S4) for determining whether or not a modified layer can be formed can be performed. Specifically, it is a step of determining a predetermined transmittance, for example, a step of determining whether the wavelength (1342 nm) of the laser light LB radiated from the laser light irradiating mechanism 24 is 30% or more, and from In the case where the transmittance measured in this embodiment is R = 60% (≧ 30%), it can be seen that the determination criterion is satisfied, that is, it is determined that the modified layer can be formed in the modified layer determination step (S4) ( "Yes"). When the absorptivity is used as an index indicating the transmittance, it is only necessary to set whether or not the absorptivity is 70% or less as a determination criterion. The determination criterion may be appropriately determined in consideration of the processing conditions of the laser processing device to be used, the physical properties and thickness of the workpiece.

(Modified layer formation step) If it is determined as "YES" in the above-mentioned modified layer formation determination step (S4), the modified layer formation step (S5) is performed next. As described above, although the calculation of the transmittance (R) is a calculation based on the dummy wafer 100, the actual formation of the modified layer is performed on the silicon wafer 110 on which the device 14 is formed. Specifically, laser processing is performed on the silicon wafer 110 that is transported from a cassette (not shown) that contains a plurality of silicon wafers 110 and is placed on the work table 34. Although the laser light LB ′ radiated at this time is a laser light having the same wavelength as the laser light LB irradiated in the first detection step (S1) and the second detection step (S2), it is for practical purposes. The modified layer is formed on the ground to set the output higher than the laser light LB when the transmittance is calculated.

In this modified layer forming step (S5), first, the back surface 110b side of the silicon wafer 110 is set as an upper surface to be placed on the work table 34 of the laser processing apparatus 2 shown in FIG. 1 described above. As shown in FIG. 4, the silicon wafer 110 is sucked and held on the suction chuck 35 of the work chuck 34 by the suction mechanism not shown. In addition, a protective tape may be affixed to the front surface 110a side of the silicon wafer 110, and the protective tape may be attached to the adsorption chuck 35 via the protective tape. In this way, the work clamp stage 34 that has attracted and held the silicon wafer 110 is positioned directly below the photographing mechanism 26 by the moving mechanism 23.

When the work clamp table 34 holding the silicon wafer 110 has been positioned directly below the photographing mechanism 26, the calibration of the processing area where the silicon wafer 110 should be laser-processed is performed by the photographing mechanism 26 and the control device 20 operation. That is, the imaging mechanism 26 and the control device 20 execute a predetermined division line 112 for forming the semiconductor wafer 2 in a predetermined direction and a laser light irradiation mechanism 24 for radiating laser light along the predetermined division line 112. Concentrator 241 performs image processing, such as pattern matching, to complete alignment of the laser light irradiation position. In addition, the alignment of the laser light irradiation position is similarly completed for the planned division line 112 formed on the silicon wafer 110 and extending in a direction orthogonal to the predetermined direction. At this time, although the front surface 110a of the silicon wafer 110 on which the planned division line 112 is formed is located on the lower side, as described above, the imaging mechanism 26 is an infrared illumination mechanism, an optical system that captures infrared rays, and outputs a signal corresponding to the infrared rays. It is configured by an imaging element (infrared CCD) or the like of an electric signal, so that it can penetrate through the back surface 110b side and shoot the division line 112 on the front side 110a side.

As long as the above is performed to detect the planned division line 112 formed on the silicon wafer 110 held on the work clamp stage 34 and the laser light irradiation position is calibrated, the work clamp stage can be shown in FIG. 4 34 moves to the laser light irradiation area where the condenser 241 is located, and positions one end of the predetermined division line 112 directly below the condenser 241 of the laser light irradiation mechanism 24. Next, the light-condensing point of the laser light LB 'irradiated from the condenser 241 is positioned from the front surface 110b of the semiconductor wafer 2 to a predetermined depth position. In addition, the silicon wafer 110 is irradiated from the condenser 241 with the same wavelength as the laser light LB irradiated in the first detection step (S1) and the second detection step (S2), and a larger laser light LB is output. ', While moving the work clamp 34 at a predetermined processing feed rate in a direction indicated by an arrow X in FIG. 4. After the other end of the dividing line 112 reaches the irradiation position of the condenser 241, the irradiation of the laser light LB 'is stopped, and the movement of the work clamp 34 is stopped. In this way, the laser processing for forming the modified layer 120 is performed, and the modified layer shown in FIG. 4 is formed inside the silicon wafer 110 while rotating and moving the work table 34 by the moving mechanism 22. 120, and finally the modified layer 120 is formed along all the predetermined division lines 112.

The laser processing conditions performed in the modified layer forming step (S5) are set to, for example, the following. Wavelength: Pulsed laser of 1342nm Repetition frequency: 90kHz Average output: 1.7W Processing feed rate: 700mm / s

Furthermore, in the above-mentioned first detection step (S1), second detection step (S2), and modified layer formation step (S5), laser light LB, LB 'having a wavelength of 1342 nm is irradiated, but the present invention It is not limited to laser light with a wavelength of 1342 nm, but can be selected from the near-infrared wavelength region, such as a laser light with a wavelength of 1000 nm to 2500 nm, according to the physical properties of the workpiece and the selected laser light irradiation mechanism 24 Select any wavelength.

(Laser processing suspension step) Returning to FIG. 3 and continuing the description, in the modified layer formation determination step (S4), if the calculated transmittance (R) does not satisfy a predetermined condition (30% or more), it is determined If "No", the modified layer forming step (S5) is not performed, but the laser processing is stopped (S6). In such a silicon wafer 110 having a transmittance (R), because the transmittance is too low, it is determined that even if laser processing is performed in accordance with a set condition, that is, a processing condition, a good formation cannot be formed inside the silicon wafer 110.的 modified 层 120。 The modified layer 120. As a result, the laser processing set thereafter is stopped. Furthermore, even if the laser processing has been suspended by the laser processing suspension step (S6), it can be set to be performed when the laser processing conditions can be changed. After the laser processing is reset (the wavelength of the laser light, the output is changed, etc.), the modified layer forming step is performed to form the modified layer 120.

The present invention is not limited to the embodiments described above, and various modifications are conceivable as long as they belong to the technical scope of the present invention.

For example, in the above-mentioned embodiment, although the dummy wafer 100 constituting the silicon wafer 110 to be processed is used to calculate the transmittance and determine whether the silicon wafer 110 is suitable for the formation of the modified layer, the present invention is not Limited to this. The silicon wafer 110 has a peripheral region 110c where the device 114 is not formed, and the silicon wafer 110 is placed instead of the dummy wafer 100 in the above-mentioned second inspection step, and at this time, it is arranged and maintained so that the peripheral region 110c covers the light receiving element of the power meter 36. In addition, the peripheral area 110c of the silicon wafer 110 may be irradiated with laser light LB, and the transmitted laser light may be received by the power meter 36 to detect the second power, thereby calculating the silicon wafer 110 actually processed. Transmission. As long as this is done, the transmittance becomes a transmittance that also incorporates a change in transmittance that is actually generated during the process of forming the device 114 on the substrate, and the transmittance can be grasped more precisely and reflected in the determination of the formation of the modified layer.

2‧‧‧laser processing equipment

2a‧‧‧ abutment

14, 114‧‧‧ devices

20‧‧‧Control device

22‧‧‧ holding agency

23‧‧‧ mobile agency

24‧‧‧Laser light irradiation mechanism

26‧‧‧ Filming Agency

30‧‧‧X-direction movable plate

31‧‧‧Y-direction movable plate

32‧‧‧ Pillar

33‧‧‧ Hood

34‧‧‧Work clamp table

35‧‧‧ Suction Chuck

36‧‧‧Power Meter

40‧‧‧X-direction moving mechanism

42‧‧‧Y-direction moving mechanism

50‧‧‧Frame

51‧‧‧Vertical wall

52‧‧‧Horizontal wall section

100‧‧‧ fake wafers

110‧‧‧ silicon wafer

110a‧‧‧front

110b‧‧‧ back

110c‧‧‧peripheral area

112‧‧‧ divided scheduled line

120‧‧‧ Modified layer

241‧‧‧Condenser

LB, LB’‧‧‧ laser light

P‧‧‧ Condensing position

Steps S1 ~ S6‧‧‧‧

X, Y, Z‧‧‧ directions

FIG. 1 is a perspective view showing the entire laser processing apparatus used in the practice of the present invention, and a perspective view showing a silicon wafer of a workpiece. FIG. 2 is a flowchart showing steps of a laser processing method implemented according to the present invention. 3 is a schematic diagram (a) illustrating the operation of the first detection step and a schematic diagram (b) illustrating the operation of the second detection step according to the present invention. FIG. 4 is a schematic diagram for explaining a modified layer forming step of the present invention.

Claims (4)

A laser processing method is a laser processing method using a laser processing device. The laser processing device is provided with at least: a holding mechanism to hold a workpiece; a laser light irradiating mechanism having a condenser; The optical device is a light condensing point of laser light having a wavelength of transmissivity to the object held by the holding mechanism, positioned inside the object to be irradiated to form a modified layer; and a processing feed mechanism, The holding mechanism is processed and fed in opposition to the laser light irradiation mechanism, and the laser processing method is composed of at least the following steps: A first detection step is to make a condenser of the laser light irradiation mechanism and a power meter phase The laser beam is irradiated on the beam to detect the first power; the second detection step is to position the object to be processed between the condenser and the power meter to irradiate the laser beam to detect the second power; the transmittance calculation step is from The first power and the second power are calculated to indicate an index of the transmittance of the object to be processed; and a modified layer formation determining step is used to determine whether the modified layer can be formed inside the object from the index of the transmittance. ; And a reforming layer forming step, irradiating a processed light spot which is determined to be capable of forming a reforming layer by the reforming layer formation determining step, by locating the light-condensing point of the laser light inside to form a reforming layer. For example, the laser processing method of claim 1, wherein the power meter is disposed adjacent to the work clamp table, and the concentrator and the holding mechanism are relatively moved to implement the first detection step. For example, the laser processing method of claim 2, wherein the object to be processed is held on the work clamp so as to exceed the work clamp of the holding mechanism and reach the power meter, and the second detection step is performed. The laser processing method according to any one of claims 1 to 3, wherein the object to be processed is a silicon wafer, and the wavelength of the laser light is near infrared.