TW201636588A - Laser beam inspection method - Google Patents

Abstract

Provided is a laser beam inspection method for inspecting the status of a laser beam within a short time at low cost. The invention comprises the following steps. The inspection film setup step forms an inspection film (13) fused by absorbing the wavelengths of laser beams (L1, L2) passing through the inspection plate-shaped object on a first surface of an inspection plate-shaped object (11) having the first surface (11a) and a second surface (11b) on the opposite side of the first surface. The modified layer formation step performed after the inspection film setup step keeps the inspection film and a holding surface (4a) of a suction platform (4) facing relatively to each other so as to utilize the suction platform to hold the inspection plate-shaped object, and illuminating the laser beam from the second surface by way of internal condensation in the inspection plate-shaped object, thereby forming a modified layer (19) within the inspection plate-shaped object. The inspection step is performed after the modified layer formation step, to inspect the status of the laser beam according to fusion patterns (21, 21a, 21b) formed on the inspection film by the laser beam passing through the inspection plate-shaped object.

Description

Laser light inspection method

The present invention relates to a method of inspecting laser light used in processing a wafer or the like.

In order to divide a wafer in which an element such as an IC is formed on the surface side into a plurality of wafers, a processing method in which laser light is condensed inside the wafer to form a reforming layer which is a starting point of division has been put into practical use (refer to, for example, the patent document) 1). In this processing method, the surface of the wafer is held by the chuck platform, and the laser light of a wavelength that is hard to be absorbed by the wafer is irradiated with the inside by the exposed back side.

However, if the reforming layer is formed on the wafer by the above-described processing method, the component is damaged due to leakage of the laser light on the surface side of the wafer. Therefore, in recent years, in order to suppress the damage of the element due to the leaked light, a processing method for suppressing the occurrence of the leaked light by using a laser beam having a very short pulse width has been proposed (see, for example, Patent Document 2).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-192370

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2014-104484

The above-described damage of the element due to leakage of light is considered to be due to insufficient adjustment of the laser beam irradiated onto the wafer or unsuitability of processing conditions. For example, it is considered that the laser beam is appropriately adjusted in such a manner that the intensity distribution becomes symmetrical in a plane perpendicular to the propagation direction, or if the processing conditions are suitable, the damage of the element due to leakage light can be further reduced.

However, on the principle of using a laser beam of a wavelength that is difficult to be absorbed by the wafer, it is difficult to visually adjust the laser beam to suit the processing conditions. Although the irradiation area of the laser light can be inspected and adjusted according to the defect of the element actually occurring, in this method, there is a problem in the time and cost required for the inspection.

The present invention has been made in view of the above problems, and an object thereof is to provide a method of inspecting a laser beam which can detect a state of laser light in a short time and at low cost.

According to the present invention, there is provided a method of inspecting a laser beam, comprising: an inspection film arrangement step of the inspection sheet having a first surface and a second surface opposite to the first surface The first surface of the object forms a laser beam that absorbs the wavelength of the plate for inspection a molten inspection film; a reforming layer forming step of holding the inspection plate with the inspection film and the holding surface of the suction cup platform, and holding the inspection plate with the suction plate platform And irradiating the laser beam to the second surface side to condense the inside of the inspection plate to form a modified layer; and an inspection step after performing the reforming layer forming step The state of the laser beam is inspected based on the molten trace formed on the inspection film by the laser beam passing through the inspection plate.

In the present invention, it is preferable that in the inspection step, if a trace is melted directly under the reforming layer directly under the reforming layer, a speckle-like melting of the near crucible which forms a melting trace directly under the reforming layer is formed. When the trace is deflected, that is, the optical axis of the optical unit or lens that is opposite to the laser beam irradiation means for irradiating the laser beam is determined, the laser beam is shifted.

In the inspection method of the laser beam of the present invention, the inspection film which is melted by the absorption of the laser beam is formed on the first surface of the inspection plate member, and is irradiated by the second surface side and passes through the inspection plate. The laser light of the object forms a melting trace on the film for inspection. Therefore, the state of the laser light can be checked based on the trace of the melt.

In the method of inspecting the laser beam of the present invention, the film for inspection is formed only on the first surface of the plate for inspection, and the laser beam passing through the plate for inspection can be visually confirmed based on the trace of the melt. The position of the illumination, so that the state of the laser light can be checked in a short time and at low cost.

2‧‧‧ Laser processing equipment

4‧‧‧Sucker platform

4a‧‧‧ Keep face

6‧‧‧Clamp

8, 12 ‧ ‧ laser processing unit (laser light irradiation means)

11‧‧‧Check plate

11a‧‧‧1st

11b‧‧‧2nd

13‧‧‧Inspection film

14‧‧‧Laser oscillator

15‧‧‧Protection components

16‧‧‧稜鏡

16a‧‧‧1st reflecting surface

16b‧‧‧2nd reflecting surface

17‧‧‧Frame

18‧‧‧Space light modulator

19‧‧‧Modified layer

20‧‧‧ drive

21‧‧‧ melting traces

21a‧‧‧ Traces of melting (melting traces directly below the modified layer)

21b‧‧‧ melting traces (spotted melting traces)

22‧‧‧Control device

24, 26‧ ‧ lens

28‧‧‧Mirror

30‧‧‧With objective lens

L, L1, L2‧‧‧ laser light

Fig. 1(A) is a perspective view showing a step of arranging a film for inspection in a mode, and Fig. 1(B) is a perspective view showing a state in which a protective member is attached to a plate for inspection in a mode.

Fig. 2 (A) is a partial cross-sectional side view showing a step of forming a modified layer in a mode, and Fig. 2 (B) is an enlarged view showing a part of Fig. 2 (A) in an enlarged manner.

[Fig. 3] Fig. 3(A) is a plan view showing, in a mode, an example of a melting trace when the laser beam is shifted in the -Y direction with respect to the optical axis of the laser processing unit, and Fig. 3(B) shows the relative pattern in the mode. A plan view of an optical axis of a laser processing unit, an example of a melting trace when the laser beam is not shifted, and FIG. 3(C) shows a mode in which the laser beam is shifted in the +Y direction with respect to the optical axis of the laser processing unit. A plan view of an example of a melting trace of time.

Fig. 4 is a view showing a configuration example of a processing unit according to a modification in a mode.

Embodiments of the present invention will be described with reference to the accompanying drawings. The inspection method of the laser beam according to the present embodiment includes a film arrangement step for inspection (see FIG. 1(A)), a reforming layer forming step (see FIGS. 2(A) and 2(B)), and inspection. Step (refer to FIG. 3 (A), FIG. 3 (B), and FIG. 3 (C)).

In the film arrangement step for inspection, a film for inspection which absorbs laser light and melts is formed on the first surface of the plate for inspection. Modification layer In the forming step, the laser beam is irradiated from the second surface side of the inspection plate member to the inside of the inspection plate member, and a modified layer is formed inside the inspection plate member.

In the inspection step, the state of the laser beam is checked based on the melting trace formed on the film for inspection by the laser beam of the inspection plate. The method of inspecting the laser beam of the present embodiment will be described in detail below.

First, an inspection film disposing step of forming an inspection film for the inspection plate is carried out. Fig. 1(A) is a perspective view showing a step of arranging a film for inspection in a mode. As shown in Fig. 1(A), the inspection plate member 11 used in the present embodiment is a disk-shaped semiconductor wafer or a ceramic substrate, and has a substantially flat first surface 11a and a first surface. 11a is the second surface 11b on the opposite side. However, the present invention is not limited thereto, and a plate member of any material or shape can be used as the plate for inspection.

In the film arrangement step for inspection, the film for inspection 13 is formed on the first surface 11a of the inspection plate member 11. The inspection film 13 is formed by absorbing the material of the laser light used in the subsequent reforming layer forming step, and is melted when it reaches a predetermined temperature. By the inspection film 13, it is possible to confirm the irradiation position of the laser beam that has reached the first surface 11a of the inspection plate member 11.

Typically, the film 13 for inspection is a single layer structure of a film made of a metal material such as titanium (Ti), tantalum (Ta), tungsten (W), aluminum (Al), or tin (Sn), or Laminated structure. When the film for inspection 13 is formed in a laminated structure, a laminated structure of a titanium film (for example, a thickness of 200 nm) and a tin film (for example, a thickness of 50 nm), a titanium film (for example, a thickness of 50 nm), and an aluminum film (for example, a thickness) may be used. A layered structure of a degree of 500 nm).

The method of forming the inspection film 13 is arbitrary, and for example, a plasma CVD method, a vacuum deposition method, a sputtering method, or the like can be used. Similarly, the thickness of the film 13 for inspection is also arbitrary. However, the thickness of the film 13 for inspection must be as thin as to be melted by the laser light. However, the present invention is not limited thereto, and any film for inspection which absorbs laser light and melts can be formed.

After the inspection film arrangement step is performed, the protective member may be attached to the first surface 11a side of the inspection plate member 11 on which the inspection film 13 is formed. Fig. 1(B) is a perspective view showing a state in which a protective member is attached to the inspection plate 11 in a mode. As shown in FIG. 1(B), for example, a protective member 15 such as a resin tape is attached to the first surface 11a side (inspection film 13) of the inspection plate member 11. Further, the annular frame 17 is fixed to the outer peripheral portion of the protective member 15.

Next, a reforming layer forming step of irradiating the inspection plate 11 with the laser beam and forming the modified layer therein is performed. Fig. 2(A) is a partial cross-sectional side view showing a step of forming a modified layer in a mode, and Fig. 2(B) is an enlarged view showing a part of Fig. 2(A) in an enlarged manner. The reforming layer forming step is carried out, for example, by the laser processing apparatus 2 shown in Fig. 2(A).

The laser processing apparatus 2 is provided with a suction cup platform 4 that sucks and holds the inspection plate member 11. The suction cup platform 4 is coupled to a rotary drive source (not shown) such as a motor, and is rotated about a vertical axis. Further, a moving mechanism (not shown) is provided below the suction cup platform 4, and the suction table 4 is moved in the horizontal direction by the moving mechanism.

The upper surface of the suction cup platform 4 is formed to penetrate the protective member 15 On the other hand, the holding surface 4a on the side of the first surface 11a (on the side of the inspection film 13) for holding the inspection plate member 11 is sucked. The holding surface 4a passes through a flow path (not shown) formed inside the suction cup table 4 to apply a negative pressure of a suction source (not shown), and an attraction force of the suction inspection plate 11 occurs. A plurality of jigs 6 for holding and fixing the annular frame 17 are disposed around the suction cup platform 4.

A laser processing unit (laser light irradiation means) 8 is disposed above the suction cup platform 4. The laser processing unit 8 condenses the laser beam L1 that is pulse-oscillated by a laser oscillator (not shown) inside the inspection plate 11 that is sucked and held by the chuck table 4. The laser oscillator is configured to oscillate the laser beam L1 having a wavelength (a wavelength that passes through the inspection plate 11) that is hard to be absorbed by the inspection plate 11 .

In the reforming layer forming step, first, the inspection sheet 11 is formed so that the inspection film 13 formed on the first surface 11a side of the inspection plate 11 faces the holding surface 4a of the suction cup table 4 (and the protective member 15) is placed on the suction cup platform 4. In this state, when the negative pressure of the suction source is applied, the inspection plate member 11 is sucked and held by the suction cup table 4 while the second surface 11b side is exposed upward.

Next, the chuck table 4 is moved and rotated to position the laser processing unit 8 in an arbitrary processing area. Thereafter, the laser beam unit 11 is irradiated with the laser beam L1 toward the inspection plate 11 to move the chuck table 4 in the horizontal direction. Thereby, multiphoton absorption is caused by the near-convergence point of the laser beam L1, and the linear modified layer 19 can be formed.

Since the laser light L1 is hard to be absorbed by the inspection plate 11, as shown in FIG. 2(B), the laser light which is not absorbed at the condensing point is not absorbed. The line L2 leaks to the side of the first surface 11a of the inspection plate member 11. In the present embodiment, the inspection film 13 is provided on the first surface 11a of the inspection plate member 11, so that the laser beam L2 passing through the inspection plate member 11 is absorbed by the inspection film 13 and is changed into heat. . As a result, the molten trace 21 is formed in a part of the film for inspection 13.

After the reforming layer forming step is performed, an inspection step of inspecting the state of the laser beam L1 based on the molten trace 21 formed on the inspection film 13 by the laser beam L2 is performed. In this inspection step, the state of the laser beam L1 is determined, for example, by visually melting the trace 21 in a plane.

Fig. 3(A) is a plan view showing an example of a melting trace 21 when the laser beam L1 is shifted in the -Y direction with respect to the optical axis of the laser processing unit 8, and Fig. 3(B) shows the relative lightning in the mode. A plan view of an optical axis of the processing unit 8 and an example of a melting trace 21 when the laser beam L1 is not shifted. FIG. 3(C) shows a mode relative to the optical axis of the laser processing unit 8, and the laser beam L1 is + A plan view of an example of the melt trace 21 when the Y direction is shifted.

As shown in FIG. 3(A), FIG. 3(B), and FIG. 3(C), a linear melting trace corresponding to the modified layer 19 is formed directly under the modified layer 19 (the modified layer is positive The lower melting trace) 21a. On the other hand, a spot-like melting trace (spot-like melting trace) 21b due to the laser beam scattered by the reforming layer 19 is formed in the vicinity of the melting trace 21a.

In the present embodiment, the state of the laser beam L1 is determined based on the positional relationship of the melt marks 21a and 21b. Specifically, as shown in FIG. 3(A) and FIG. 3(C), if the melt trace 21b is deflected toward the junction, One side of the trace 21a, that is, the optical axis of the various optical units (mirrors, mirrors, etc.) (not shown) or lenses (not shown) of the laser processing unit 8 is determined, and the laser beam L1 is shifted. .

On the other hand, as shown in FIG. 3(B), when the molten traces 21b are substantially uniformly dispersed on both sides of the molten traces 21a which are the boundary, it is determined that the respective optical units of the laser processing unit 8 (mirrors, mirrors) The optical axis of the lens (not shown) or the lens (not shown) is not offset by the laser beam L1.

As described above, in the inspection method of the laser beam of the present embodiment, the inspection film 13 which is melted by the absorption of the laser beam L2 is formed on the first surface 11a of the inspection plate member 11, and therefore The molten trace 21 is formed on the inspection film 13 by the laser beam L2 which is irradiated on the side of the second surface 11b and passes through the inspection plate 11. Therefore, the state of the laser beam L1 can be checked based on the melt trace 21.

In the method of inspecting the laser beam of the present embodiment, the inspection film 13 is formed only on the first surface 11a of the inspection plate member 11, and the inspection plate can be visually confirmed based on the melting trace 21. Since the irradiation position of the laser beam L2 of 11 is made, the state of the laser beam L1 can be checked in a short time and at low cost.

However, the present invention is not limited to the description of the above embodiment. For example, the laser processing unit (laser light irradiation means) 8 of the laser processing apparatus 2 described above is a more arbitrary laser processing unit. Fig. 4 is a view showing a configuration example of a laser processing unit according to a modification in a mode.

As shown in FIG. 4, the laser processing unit of the modification (Ray The radiation illuminating means 12 includes a laser oscillator 14, a weir 16, a spatial light modulator 18, a driving device 20, a control device 22, lenses 24 and 26, a mirror 28, and a objective lens 30.

The laser oscillator 14 is configured to include a laser medium such as Nd:YAG, and can pulsing a laser beam L having a wavelength (a wavelength that passes through the inspection plate 11) that is hard to be absorbed by the inspection plate 11 oscillation. The laser beam L oscillated by the laser oscillator 14 is reflected by the first reflecting surface 16a of the crucible 16 and then input to the spatial light modulator 18.

The spatial light modulator 18 modulates the phase of the laser beam L by using a hologram for phase modulation as shown by a complex pixel in a two-dimensional array. For the hologram for phase modulation, it is sufficient to use CGH (Computer Generated Hologram) calculated from the calculation.

Here, in FIG. 4, the laser processing unit 12 using the reflective spatial light modulator 18 is exemplified, but a transmissive spatial light modulator may be used. If a transmissive spatial light modulator is used, 稜鏡 can be omitted.

The drive device 20 sets the phase modulation variable of each pixel included in the spatial light modulator 18. Thereby, the hologram for phase modulation is displayed in the spatial light modulator 18. The control device 22 is, for example, a computer that controls the operation of the drive mechanism 20 to cause the spatial light modulator 18 to display a suitable hologram. By the control device 22, the spatial light modulator 18 can display the hologram of the plurality of positions at which the laser beam L is condensed inside the inspection plate 11.

The laser beam L outputted by the spatial light modulator 18 is reflected on the second reflecting surface 16b of the crucible 16, and passes through the lenses 24, 26 and The mirror 28 is incident on the objective lens 30. The lenses 24 and 26 are arranged such that the spatial light modulator 18 and the objective lens 30 are in an imaging relationship with each other, and the image of the laser beam L in the spatial light modulator 18 is imaged on the objective lens 30.

The objective lens 30 converges the incident laser light L at a plurality of positions inside the inspection plate 11. By using the laser processing unit 12, the reforming layer 19 can be simultaneously formed at a plurality of positions.

In addition, the configuration, the method, and the like of the above-described embodiments can be appropriately changed and implemented without departing from the scope of the invention.

11‧‧‧Check plate

11a‧‧‧1st

11b‧‧‧2nd

13‧‧‧Inspection film

15‧‧‧Protection components

17‧‧‧Frame

Claims (2)

A method for inspecting a laser beam, comprising: a step of arranging a film for inspection, the step of forming a plate for inspection on a second surface having a first surface and a side opposite to the first surface One surface forms an inspection film that melts by absorbing laser light having a wavelength that passes through the inspection plate, and a reforming layer forming step is performed after the inspection film arranging step is performed, and the inspection film and the inspection film are The inspection plate is held by the suction cup platform on the surface opposite to the holding surface of the suction cup platform, and the laser beam is irradiated to the inside of the inspection plate by the second surface side. Forming a reforming layer inside the inspection plate; and an inspection step of forming the inspection film according to the laser beam passing through the inspection plate after performing the reforming layer forming step The trace of melting, check the state of the laser light. The method for inspecting a laser beam according to claim 1, wherein in the inspecting step, if a trace is melted directly under the reforming layer directly under the reforming layer, the modified layer is formed When the spot-like melting trace of the near-melting trace is deflected, that is, the optical axis of the optical unit or lens of the laser beam irradiation means for irradiating the laser beam is determined, the laser beam is shifted.