Laser processing device

Abstract

A laser processing apparatus is provided for forming a modified region in an object by irradiating laser light to the object, the laser processing apparatus including: a support portion for supporting the object; a light source for emitting the laser light; a spatial light modulator for modulating the laser light emitted from the light source according to a modulation pattern and emitting the laser light; a condensing portion including a condensing lens for condensing the laser light emitted from the spatial light modulator toward the object; and a control portion for causing the spatial light modulator to display the modulation pattern corresponding to an image signal by inputting the image signal to the spatial light modulator.

Description

Technical Field

[0001] This invention relates to laser processing apparatus. Background Technology

[0002] Patent document 1 (Japanese Patent Application Publication No. 2015-223620) discloses a laser processing apparatus. This laser processing apparatus includes a spatial light modulator for modulating laser light emitted from a light source. In the spatial light modulator, a modulation pattern is displayed on the liquid crystal layer based on a voltage applied to the liquid crystal layer, thereby modulating the laser light. Summary of the Invention

[0003] In Patent Document 1, the spatial light modulator is constructed by sequentially stacking a driving circuit layer, a pixel electrode layer, a reflective film, an alignment film, a liquid crystal layer, an alignment film, a transparent conductive film, and a transparent substrate on a semiconductor substrate.

[0004] In such a spatial light modulator, when a signal representing a modulation pattern is input to the driving circuit layer, a voltage corresponding to that signal is applied to each pixel electrode, creating an electric field between each pixel electrode and the transparent conductive film. When this electric field is formed, the alignment direction of the liquid crystal molecules changes in each region corresponding to each pixel electrode (hereinafter sometimes referred to as a "pixel") in the liquid crystal layer, and the refractive index changes in each region corresponding to each pixel electrode. This state is the state in which the modulation pattern is displayed in the liquid crystal layer.

[0005] When a modulation pattern is displayed on the liquid crystal layer, laser light is incident on the liquid crystal layer from the outside through a transparent substrate and a transparent conductive film. It is reflected by the reflective film and exits from the liquid crystal layer through the transparent conductive film and the transparent substrate to the outside. The laser light is modulated according to the modulation pattern displayed on the liquid crystal layer. Thus, by appropriately setting the modulation pattern displayed on the liquid crystal layer using a spatial light modulator, laser light modulation can be achieved.

[0006] Furthermore, an image signal can be used as the signal used to display the modulation pattern in the spatial light modulator. In this case, a voltage corresponding to the grayscale value of the image signal input to the spatial light modulator is applied to the liquid crystal layer, generating a refractive index change corresponding to the voltage value, thereby displaying the modulation pattern. Furthermore, the laser incident on the spatial light modulator is phase-modulated according to the modulation pattern. Therefore, in this case, the image signal and the modulation pattern, and the phase modulation amount imparted to the laser by the grayscale value of the image signal and the modulation pattern, correspond to each other. Hereinafter, the phase modulation amount imparted to the laser by the modulation pattern will sometimes be simply referred to as the phase modulation amount of the modulation pattern.

[0007] However, the actual phase modulation amount of the modulation pattern sometimes becomes passivated relative to the ideal state. The inventors have gained insight into how this passivation of phase modulation amount can sometimes lead to the following problems.

[0008] That is, for a spatial light modulator with a phase modulation capability of up to 2π, when displaying a modulation pattern containing a region with a phase modulation amount greater than 2π, the modulation pattern is reproduced by reflecting back the region exceeding 2π. In this case, due to passivation of the phase modulation amount, sometimes the modulation state of the laser differs between the reflected region (reversed region) and the non-reflected region (forward region) in the modulation pattern. Therefore, if there is a deviation in the ratio of the reversed region to the forward region in the modulation pattern, the change in this ratio becomes larger when the modulation pattern changes, resulting in a larger change in the modulation state of the laser. Furthermore, as an example, when the modulation pattern is a diffraction grating pattern, the modulation state of the laser refers to the diffraction efficiency of the laser.

[0009] On the other hand, according to the inventors, it has been observed that the presence of a folded-back portion of the phase modulation amount biased towards a portion of the modulation pattern sometimes causes the following problem: If the folded-back portion of the phase modulation amount is biased towards a portion of the modulation pattern, then sometimes the focusing state of the laser is deviated between the portion modulated via this folded-back bias and the portion modulated without this folded-back bias. Therefore, it is desirable to suppress the passivation effect of the phase modulation amount of the modulation pattern and the bias of the folded-back portion of the phase modulation amount in the modulation pattern.

[0010] Therefore, the object of the present invention is to provide a laser processing apparatus that can suppress the passivation effect of the phase modulation amount of the modulation pattern and the bias of the folded-back portion of the phase modulation amount in the modulation pattern.

[0011] The laser processing apparatus of the present invention is a laser processing apparatus for forming a modified region on an object by irradiating the object with a laser. The laser processing apparatus includes: a support for supporting the object; a light source for emitting laser light; a spatial light modulator for modulating and emitting the laser light emitted from the light source according to a modulation pattern; a focusing unit including a focusing lens for focusing the laser light emitted from the spatial light modulator onto the object; and a control unit that, by inputting an image signal to the spatial light modulator, causes the spatial light modulator to display a modulation pattern corresponding to the image signal, and the control unit performs an operation by controlling the movement of at least one of the support and the focusing unit to... The laser focusing point moves relative to the object along the X direction of the laser incident surface while irradiating the object with laser. In the processing of the image signal, gray level values ​​corresponding to the phase modulation amount in the modulation pattern are set in each region. In the processing, the control unit inputs the image signal containing the first signal into the spatial light modulator, so that the spatial light modulator displays a modulation pattern containing the first pattern corresponding to the first signal. The gray level value of the first signal changes from the minimum value to the maximum value at a certain slope from the region corresponding to one end of the modulation pattern in the first direction to the region corresponding to the other end of the modulation pattern in the first direction.

[0012] In this laser processing apparatus, the control unit inputs an image signal into a spatial light modulator, causing the spatial light modulator to display a modulation pattern. Laser modulation is then performed based on this modulation pattern, and processing is executed. In the image signal, a grayscale level value corresponding to the phase modulation amount at each position of the modulation pattern is set for each region constituting the image signal. That is, in the spatial light modulator, by setting the phase modulation amount at each position of the modulation pattern to an amount corresponding to the grayscale level value of each region of the image signal, the desired pattern is displayed as a whole. Furthermore, the image signal includes a first signal whose grayscale level value changes at a certain slope from the region corresponding to one end of the modulation pattern to the region corresponding to the other end of the modulation pattern. As a result, the modulation pattern displayed on the spatial light modulator includes a first pattern in which the phase modulation amount changes at a certain slope along a direction according to the first signal. According to the inventors, when the modulation pattern includes such a first pattern, the passivation effect of the phase modulation amount of the modulation pattern and the bias of the reflected portion of the phase modulation amount in the modulation pattern can be suppressed.

[0013] In the laser processing apparatus of the present invention, during processing, the control unit may input an image signal containing a second signal corresponding to the second pattern into the spatial light modulator in a manner that displays a modulation pattern including a second pattern for branching the laser into multiple processing beams on the spatial light modulator. In this case, the modulation pattern overlaps with the second pattern. In such a case, deviations between the multiple processing beams can be suppressed.

[0014] In the laser processing apparatus of the present invention, the first direction may also be a direction corresponding to the direction intersecting the branching direction of the laser. In this case, deviations between processing beams can be suppressed more effectively.

[0015] In the laser processing apparatus of the present invention, during processing, the control unit may input an image signal containing a third signal corresponding to the third pattern into the spatial light modulator in a manner that displays a modulation pattern including the third pattern on the spatial light modulator, wherein the third signal is used to change the focusing position of the laser according to the radial position of the condenser lens. In this case, the third pattern can suppress the reflection portion of the phase modulation amount from deflecting in a manner corresponding to a specific radial position of the condenser lens, thereby suppressing deviations in the focusing state of the laser.

[0016] In the laser processing apparatus of the present invention, the control unit may, in the first signal, cause the grayscale value to change from a region corresponding to one end of a second direction intersecting the modulation pattern and the first direction, to a region corresponding to the other end of the second direction of the modulation pattern, from a minimum value to a maximum value with a certain slope. In this case, the grayscale value of the image signal changes with a certain slope in two intersecting directions. Therefore, within the plane of the spatial light modulator corresponding to these two directions, the passivation effect of the phase modulation amount and the bias of the reflected portion of the phase modulation amount can be suppressed.

[0017] In the laser processing apparatus of the present invention, the control unit may also vary the grayscale level value in the first signal in a manner having multiple cycles in at least one direction. In this case, the passivation effect of the phase modulation amount and the bias of the reflected portion of the phase modulation amount can be suppressed more reliably.

[0018] According to the present invention, a laser processing apparatus can be provided that can suppress the effects of passivation of the phase modulation amount of a modulation pattern and the bias of the folded-back portion of the phase modulation amount in the modulation pattern. Attached Figure Description

[0019] Figure 1 This is a schematic diagram showing the laser processing apparatus of this embodiment.

[0020] Figure 2 yes Figure 1 A cross-sectional view of a portion of the spatial light modulator shown.

[0021] Figure 3 This is a top view of the wafer of an object used in one implementation.

[0022] Figure 4 yes Figure 3 A cross-sectional view of a portion of the wafer shown.

[0023] Figure 5 This is a cross-sectional view of a wafer used to illustrate the operation of a laser processing apparatus in the case of a 3-point branch.

[0024] Figure 6 This is a schematic diagram illustrating an example of a modulation pattern.

[0025] Figure 7 This is a schematic diagram illustrating an example of a modulation pattern.

[0026] Figure 8 This is a schematic diagram illustrating an example of a modulation pattern containing a diffraction grating pattern.

[0027] Figure 9 This is a diagram showing an example of a diffraction grating pattern.

[0028] Figure 10 This is a diagram showing the state where a deformation correction pattern is superimposed on a diffraction grating pattern.

[0029] Figure 11 This is a diagram showing an example of a diffraction grating pattern.

[0030] Figure 12 This is a diagram illustrating an example of an averaged pattern.

[0031] Figure 13 This is a diagram illustrating an example of a modulation pattern formed by overlapping and averaging a diffraction grating pattern.

[0032] Figure 14 This is a diagram illustrating an example of a modulation pattern formed by overlapping and averaging a deformation correction pattern.

[0033] Figure 15 This is a schematic diagram illustrating the relationship between a condenser lens and a laser.

[0034] Figure 16 This is a diagram showing an example of a shaping pattern.

[0035] Figure 17 It shows the use of Figure 16 A cross-sectional photograph of the processing result in the case of the shaping pattern shown.

[0036] Figure 18 It shows the... Figure 16 The overlapping of the shaping patterns shown Figure 12 The diagram shows a modulation pattern formed by the averaging pattern shown.

[0037] Figure 19 It shows the use of Figure 16 The shaping pattern shown and Figure 18 A cross-sectional photograph of the processing result under the modulated pattern shown.

[0038] Figure 20 This is a diagram showing a variation of the averaged pattern.

[0039] Figure 21 This is a diagram used to illustrate a variation of a shaping pattern.

[0040] Figure 22 This is a diagram used to illustrate a variation.

[0041] Figure 23 This is a diagram used to illustrate a variation. Detailed Implementation

[0042] Hereinafter, one embodiment will be described in detail with reference to the accompanying drawings. Furthermore, in the various drawings, the same or equivalent parts are labeled with the same reference numerals, and repeated descriptions are omitted.

[0043] [Structure of laser processing equipment]

[0044] Figure 1 This is a schematic diagram illustrating the laser processing apparatus of this embodiment. Figure 1 As shown, the laser processing apparatus 1 includes: a support unit 2, a light source 3, an optical axis adjustment unit 4, a spatial light modulator 5, a focusing unit 6, an optical axis monitoring unit 7, a visual imaging unit 8, an infrared imaging unit 9, and a control unit 10. The laser processing apparatus 1 is a device that forms a modified region 12 on an object 11 by irradiating it with a laser beam L. In the following description, the three mutually orthogonal directions are referred to as the X direction, Y direction, and Z direction. In this embodiment, the X direction is the first horizontal direction, the Y direction is the second horizontal direction perpendicular to the first horizontal direction, and the Z direction is the vertical direction.

[0045] The support part 2 supports the object 11, for example, by adsorbing and pasting a film (not shown) onto the object 11, such that the surface 11a of the object 11 is orthogonal to the Z direction. The support part 2 can move along either the X or Y direction, and can rotate about an axis parallel to the Z direction.

[0046] The light source 3 emits laser L, for example, through pulse oscillation. Laser L is transmissive relative to the object 11.

[0047] The optical axis adjustment unit 4 adjusts the optical axis of the laser L emitted from the light source 3. In this embodiment, the optical axis adjustment unit 4 adjusts the optical axis of the laser L while changing the travel direction of the laser L emitted from the light source 3 to the Z direction. The optical axis adjustment unit 4 is, for example, composed of multiple reflectors whose position and angle can be adjusted.

[0048] A spatial light modulator 5 is disposed within the housing H. The spatial light modulator 5 modulates the laser L emitted from the light source 3. In this embodiment, the laser L, which travels downward along the Z direction from the optical axis adjustment section 4, is incident into the housing H. The laser L incident into the housing H is horizontally reflected by the reflector M1 at an angle relative to the Y direction, and the laser L reflected by the reflector M1 is incident into the spatial light modulator 5. The spatial light modulator 5 modulates the incident laser L while reflecting it horizontally along the Y direction.

[0049] A focusing unit 6 is mounted on the bottom wall of the housing H. The focusing unit 6 focuses the laser L modulated by the spatial light modulator 5 along the Z-direction from the surface 11a side onto the object 11 supported by the support unit 2. In this embodiment, the laser L, horizontally reflected along the Y-direction by the spatial light modulator 5, is reflected downwards along the Z-direction by the dichroic mirror M2, and the laser L reflected by the dichroic mirror M2 is incident on the focusing unit 6. The focusing unit 6 focuses the incident laser L onto the object 11. In this embodiment, the focusing unit 6 is constructed by mounting a focusing lens unit 61 on the bottom wall of the housing H via a drive mechanism 62. The drive mechanism 62 moves the focusing lens unit 61 along the Z-direction, for example, by the driving force of a piezoelectric element.

[0050] Furthermore, within the housing H, an imaging optical system (not shown) is disposed between the spatial light modulator 5 and the focusing section 6. This imaging optical system is a telecentric optical system on both sides of the reflecting surface of the spatial light modulator 5 and the entrance pupil surface of the focusing section 6 (the focusing lens 61a described later), which are in an imaging relationship. Thus, the image of the laser L on the reflecting surface of the spatial light modulator 5 (the image of the laser L modulated by the spatial light modulator 5) is transmitted (imaged) onto the entrance pupil surface of the focusing section 6.

[0051] On the bottom wall of the housing H, a pair of range sensors S1 and S2 are mounted on both sides of the condenser lens unit 61 in the X direction. Each range sensor S1 and S2 emits range-measuring light (e.g., laser) to the surface 11a of the object 11, and obtains the displacement data of the surface 11a by detecting the range-measuring light reflected from the surface 11a.

[0052] An optical axis monitoring unit 7 is disposed within the housing H. The optical axis monitoring unit 7 detects a portion of the laser L that passes through the dichroic mirror M2 (e.g., 0.5% to 5% of the laser L incident on the dichroic mirror M2). The detection result from the optical axis monitoring unit 7 indicates, for example, the relationship between the optical axis of the laser L incident on the condenser lens unit 61 and the optical axis of the condenser lens unit 61.

[0053] A visual camera unit 8 is disposed within the housing H. The visual camera unit 8 emits visible light V and acquires an image of the object 11 formed by the visible light V as an image. In this embodiment, the visible light V emitted from the visual camera unit 8 is irradiated onto the surface 11a of the object 11 via the dichroic mirror M2 and the condenser 6, and the visible light V reflected from the surface 11a is detected by the visual camera unit 8 via the condenser 6 and the dichroic mirror M2.

[0054] An infrared camera 9 is mounted on the side wall of the housing H. The infrared camera 9 emits infrared light and acquires an image of the object 11 formed by the infrared light as an image. In this embodiment, the housing H and the infrared camera 9 can move integrally along the Z direction.

[0055] The control unit 10 controls the operation of each part of the laser processing apparatus 1. The control unit 10 includes a processing unit 101, a storage unit 102, and an input receiving unit 103. The processing unit 101 is configured as a computer device including a processor, memory, storage, and communication devices. In the processing unit 101, the processor executes software (programs) loaded into memory, controls the reading and writing of data in the memory and storage, and controls communication based on the communication devices. The storage unit 102 is, for example, a hard disk, which stores various types of data. The input receiving unit 103 is an interface unit that receives various types of data input from the operator. In this embodiment, the input receiving unit 103 is configured as a GUI (Graphical User Interface).

[0056] In the laser processing apparatus 1 configured as described above, if the laser L is focused inside the object 11, the laser L is absorbed at the point corresponding to the focusing point C of the laser L, forming a modified region 12 inside the object 11. The modified region 12 is a region whose density, refractive index, mechanical strength, and other physical properties differ from the surrounding unmodified region. Examples of modified regions 12 include melt-processed regions, cracked regions, insulation-damaged regions, and regions with refractive index changes. The modified region 12 has the characteristic that cracks easily extend from the modified region 12 towards the incident side of the laser L and the opposite side. This characteristic of the modified region 12 is used for cutting the object 11.

[0057] As an example, the operation of the laser processing apparatus 1 in the case where a modified region 12 is formed inside the object 11 along the line 15 used to cut the object 11 will be described.

[0058] First, the laser processing apparatus 1 rotates the support 2 with the line 15 set on the object 11 parallel to the X direction and the axis parallel to the Z direction as the center line. Next, based on the image acquired by the infrared camera 9 (e.g., an image of the functional element layer of the object 11), the laser processing apparatus 1 moves the support 2 along both the X and Y directions such that the focusing point C of the laser L is located on the line 15 when viewed from the Z direction. Hereinafter, this "alignment of the focusing part 6 relative to the processing start position on the line 15" will be referred to as "alignment".

[0059] Next, based on the image acquired by the visual imaging unit 8 (e.g., an image of the surface 11a of the object 11), the laser processing apparatus 1 moves the housing H (i.e., the focusing part 6) along the Z direction such that the focusing point C of the laser L is located on the surface 11a. Hereinafter, this "alignment of the focusing part 6 relative to the surface 11a" will be referred to as "height setting". Then, using this position as a reference, the laser processing apparatus 1 moves the housing H (i.e., the focusing part 6) along the Z direction such that the focusing point C of the laser L is located at a predetermined depth from the surface 11a.

[0060] Next, the laser processing apparatus 1 emits laser L from the light source 3, and moves the support 2 along the X direction such that the focusing point C of laser L moves relative to the line 15. Hereinafter, the "relative movement direction of laser L relative to object 11" will be referred to as "relative movement direction A of laser L". At this time, based on the displacement data of surface 11a obtained by the distance sensor located on the front side of the relative movement direction A of the pair of distance sensors S1 and S2, the laser processing apparatus 1 actuates the drive mechanism 62 of the focusing part 6 such that the focusing point C of laser L is located at a predetermined depth from surface 11a.

[0061] Based on the above, a row of modified regions 12 is formed along line 15 at a certain depth from the surface 11a of the object 11. When laser L is emitted from the light source 3 via pulse oscillation, multiple modified points 12s are formed in a row along the X direction. A modified point 12s is formed by irradiation with a single pulse of laser L. A row of modified regions 12 is a collection of multiple modified points 12s arranged in a row. Adjacent modified points 12s are sometimes connected and sometimes separated depending on the pulse spacing of laser L (the value obtained by dividing the relative moving speed of the focusing point C relative to the object 11 by the repetition frequency of laser L).

[0062] [Structure of a spatial light modulator]

[0063] The spatial light modulator 5 in this embodiment is a spatial light modulator (SLM) of reflective liquid crystal on silicon (LCOS). Figure 2 yes Figure 1 A cross-sectional view of a portion of the spatial light modulator shown. Figure 2 As shown, the spatial light modulator 5 is constructed by sequentially stacking a driving circuit layer 52, a pixel electrode layer 53, a reflective film 54, an alignment film 55, a liquid crystal layer 56, an alignment film 57, a transparent conductive film 58, and a transparent substrate 59 on a semiconductor substrate 51.

[0064] The semiconductor substrate 51 is, for example, a silicon substrate. The driving circuit layer 52 forms an active matrix circuit on the semiconductor substrate 51. The pixel electrode layer 53 includes a plurality of pixel electrodes 53a arranged in a matrix along the surface of the semiconductor substrate 51. Each pixel electrode 53a is formed, for example, from a metal material such as aluminum. A voltage is applied to each pixel electrode 53a through the driving circuit layer 52.

[0065] The reflective film 54 is, for example, a dielectric multilayer film. An alignment film 55 is disposed on the surface of the liquid crystal layer 56 on the side of the reflective film 54, and an alignment film 57 is disposed on the surface of the liquid crystal layer 56 on the opposite side to the reflective film 54. Each alignment film 55 and 57 is formed, for example, from a polymer material such as polyimide, and the contact surfaces of each alignment film 55 and 57 with the liquid crystal layer 56 are subjected to, for example, rubbing treatment. The alignment films 55 and 57 align the liquid crystal molecules 56a contained in the liquid crystal layer 56 in a certain direction.

[0066] A transparent conductive film 58 is disposed on the surface of the transparent substrate 59 on the side of the alignment film 57, and faces the pixel electrode layer 53 across the liquid crystal layer 56 or the like. The transparent substrate 59 is, for example, a glass substrate. The transparent conductive film 58 is formed of, for example, a light-transmitting and conductive material such as ITO. The transparent substrate 59 and the transparent conductive film 58 allow laser L to pass through.

[0067] In the spatial light modulator 5 configured as described above, when an image signal representing a modulation pattern is input from the control unit 10 to the drive circuit layer 52, a voltage corresponding to the image signal is applied to each pixel electrode 53a, forming an electric field between each pixel electrode 53a and the transparent conductive film 58. When this electric field is formed, the alignment direction of the liquid crystal molecules 216a changes in each region (pixel 56p) corresponding to each pixel electrode 53a in the liquid crystal layer 56, and the refractive index changes in each region corresponding to each pixel electrode 53a. This state is the state in which a modulation pattern is displayed in the liquid crystal layer 56.

[0068] When a modulation pattern is displayed on the liquid crystal layer 56, and a laser L is incident from the outside onto the liquid crystal layer 56 via the transparent substrate 59 and the transparent conductive film 58, reflected by the reflective film 54, and emitted from the liquid crystal layer 56 back to the outside via the transparent conductive film 58 and the transparent substrate 59, the laser L is modulated according to the modulation pattern displayed on the liquid crystal layer 56. Thus, according to the spatial light modulator 5, the laser L can be modulated (e.g., the intensity, amplitude, phase, polarization, etc. of the laser L can be modulated) by appropriately setting the modulation pattern displayed on the liquid crystal layer 56.

[0069] [Structure of the object]

[0070] Figure 3 This is a top view of the wafer of an object used in one implementation. Figure 4 yes Figure 3 A cross-sectional view of a portion of the wafer is shown. Figure 3 and Figure 4 As shown, the object 11 in this embodiment is a wafer 20. The wafer 20 has a first surface 20a and a second surface (laser incident surface) 20b opposite to the first surface 20a. The wafer 20 is constructed by stacking a functional element layer 22 on a semiconductor substrate 21.

[0071] The semiconductor substrate 21 is, for example, a silicon substrate. The semiconductor substrate 21 has a first surface 21a and a second surface 21b opposite to the first surface 21a. The second surface 21b is the second surface 20b of the wafer 20. A notch 21c indicating the crystal orientation is provided on the semiconductor substrate 21. Alternatively, an orientation flat may be provided on the semiconductor substrate 21 instead of the notch 21c.

[0072] A functional element layer 22 is disposed on the first surface 21a of the semiconductor substrate 21. The functional element layer 22 has a plurality of functional elements 22a arranged in a matrix along the first surface 21a of the semiconductor substrate 21. Each functional element 22a is, for example, a light-receiving element such as a photodiode, a light-emitting element such as a laser diode, or a circuit element such as a memory. The functional elements 22a may also be stacked in multiple layers and configured in three dimensions.

[0073] For each functional element 22a, the wafer 20 is cut along each of the plurality of lines 15. The plurality of lines 15 extend in a lattice pattern along the second surface 21b of the wafer 20 in a manner that, when viewed from the thickness direction of the wafer 20, passes between each of the plurality of functional elements 22a (more specifically, in the center of a street region 23 extending between adjacent functional elements 22a). Each line 15 is an imaginary line set by the laser processing apparatus 1 on the wafer 20. Alternatively, each line 15 may also be a line actually led out from the wafer 20.

[0074] [An example of the operation of a laser processing device]

[0075] Figure 5 This is a cross-sectional view of a wafer used to illustrate the operation of a laser processing apparatus in the case of a three-point branch. (Example:) Figure 5 As shown, in the laser processing apparatus 1, the wafer 20 is supported by the support portion 2 such that the second surface 20b of the wafer 20 is orthogonal to the Z direction. Furthermore, the spatial light modulator 5 is controlled by the control portion 10 to display a predetermined modulation pattern (e.g., a modulation pattern including a diffraction pattern) on the liquid crystal layer 56 of the spatial light modulator 5. In this state, a laser L is emitted from the light source 3, and the focusing portion 6 focuses the laser L from the second surface 20b side onto the wafer 20. That is, the spatial light modulator 5 modulates the laser L, and the modulated laser L is focused from the second surface 20b side onto the wafer 20 by the focusing portion 6.

[0076] Thus, the laser L is branched (diffracted) into multiple processing beams L1, L2, and L3, each containing a 0th-order beam. The multiple focusing points C1, C2, and C3 of these processing beams are located at different positions in the Z and X directions. In this embodiment, processing beam L2 is a 0th-order beam. The focusing point C1 of processing beam L1 is located further forward in the relative movement direction A of the laser L than the focusing point C2 of processing beam L2, which is also a 0th-order beam. The focusing point C3 of processing beam L3 is located further backward in the relative movement direction A of the laser L than the focusing point C2 of processing beam L2, which is also a 0th-order beam. As an example, processing beam L1 is a +1st-order beam, and processing beam L3 is a -1st-order beam.

[0077] In this embodiment, the laser L is modulated by the spatial light modulator 5 such that the positional relationship of the plurality of focusing points C1, C2, and C3 in the relative movement direction A of the laser L is such that the forward side is located on the first surface 20a side of the wafer 20 in the Z direction. That is, the laser L is modulated by the spatial light modulator 5 such that focusing point C2 is located on the first surface 20a side of the wafer 20 in the Z direction more than focusing point C3, and focusing point C1 is located on the first surface 20a side of the wafer 20 in the Z direction more than focusing point C2. Furthermore, in this embodiment, the laser L is modulated by the spatial light modulator 5 such that the processing light L1, which branches out to the foremost side in the relative movement direction A of the laser L among the plurality of processing lights L1, L2, and L3, has the largest output (energy, intensity). Furthermore, even if there is a processing light among the multiple processing lights L1, L2, L3 that has an output equal to that of processing light L1, the case where the output of other processing lights is less than that of processing light L1 is also included in the case where processing light L1 has the largest output.

[0078] With the laser L branched into multiple processing beams L1, L2, and L3, each containing a zero-order beam, the support unit 2 is controlled by the control unit 10 in a manner where the X-direction is aligned with the extension direction of line 15 and multiple focusing points C1, C2, and C3 move relative to each other along line 15. As a result, three rows of modified regions 12 are formed along one line 15. The distances from the second surface 20b of the wafer 20 to each modified region 12 are different, and the depth of each modified region 12 corresponds to the depth of each focusing point C1, C2, and C3. This is one example of the operation of the laser processing apparatus 1 and one example of the processing performed by the control unit 10. Furthermore, in the above example, the example of branching the laser L into three processing beams L1, L2, and L3 has been described, but in processing, it is not limited to this; the laser L may be branched into two or four or more processing beams, or the laser L may be used without branching.

[0079] Insights into the problems and solutions of spatial light modulators

[0080] Next, the inventors' insights related to the first problem and the solution to the first problem in the case of using the spatial light modulator 5 as described above will be explained. Figure 6 This is a diagram showing an example of a modulation pattern displayed on a spatial light modulator. Figure 6 (a) shows the ideal modulation pattern Pi. Figure 6 (b) shows the actual modulation pattern Pr. (e.g.) Figure 6 As shown, for example, between pixels 56p adjacent to each other at pixel spacing D, the actual modulation pattern Pr sometimes exhibits passivation relative to the phase modulation amount of the ideal modulation pattern Pi. The inventors have gained insight into how this passivation of phase modulation amount sometimes leads to the following problems.

[0081] That is, such as Figure 7 As shown, in the case of displaying a modulation pattern P1 containing a region with a phase modulation amount greater than 2π (e.g., 2π to 6π) on a spatial light modulator 5 having a phase modulation capability with an upper limit of 2π (see reference 1), Figure 7 (a) is used to reproduce the modulation pattern Pl by folding back the region exceeding 2π (refer to). Figure 7 (b) In this case, due to the passivation of the phase modulation amount, sometimes a region with a reflection (reverse region) and a region without a reflection (forward region) are generated in the modulation pattern Pl, and the modulation state of the laser L is different. This will be explained in more detail.

[0082] First, an image signal can be used as the signal for displaying the modulation pattern in the spatial light modulator 5. In this case, a voltage corresponding to the gray level value of the image signal input to the spatial light modulator 5 is applied to the liquid crystal layer 56, generating a refractive index change corresponding to the value of the voltage, thereby displaying the modulation pattern. Then, the laser incident on the spatial light modulator 5 is phase-modulated according to the modulation pattern. Therefore, in this case, the image signal and the modulation pattern, as well as the phase modulation amount imparted to the laser L by the gray level value of the image signal and the modulation pattern, correspond to each other. Therefore, the gray level value and the phase modulation amount will sometimes be described in the same sense below.

[0083] Here, the modulation pattern includes a diffraction grating pattern for branching the laser L into three processing beams L1, L2, and L3. Figure 8 This is a schematic diagram illustrating an example of a modulation pattern containing a diffraction grating pattern. Figure 8 In the examples, the spatial light modulator 5 has a phase modulation capability of 2π. When the gray level value is 0, the phase modulation amount (phase difference) is 0 [rad], and when the gray level value is 256, the phase modulation amount (phase difference) is 2π [rad].

[0084] exist Figure 8 In the example shown in (a), only the diffraction grating pattern Pg with a gray level value T1 of 82 is shown. In this case, the gray level value T1 in the diffraction grating pattern Pg does not exceed 256, that is, the phase modulation amount does not exceed 2π, so no inversion region is produced.

[0085] In addition, Figure 8 In the example shown in (b), a modulation pattern Pc1 is formed by overlapping an offset pattern Pb1 with a gray level value T1 of 82 and an offset value Q1 of 100. In this case, the total gray level value T2 (gray level value T1 + offset value Q1) in the modulation pattern Pc1 is 182, which does not exceed 256, that is, the phase modulation amount does not exceed 2π, so no inversion region is generated. In addition, the offset pattern is used to schematically represent the case where a modulation pattern (e.g., a diffraction grating pattern) is superimposed with other modulation patterns (e.g., the deformation correction pattern or aberration correction pattern of the spatial light modulator 5).

[0086] On the other hand, Figure 8In the example shown in (c), a modulation pattern Pc2 is formed by overlapping an offset pattern Pb2 with a diffraction grating pattern Pg having a gray level value T1 of 82 and an offset value Q2 of 200. In this case, the total gray level value (gray level value T1 + offset value Q2) in the modulation pattern Pc2 becomes 282, resulting in an excess amount T3 exceeding 256 (i.e., the portion of phase modulation exceeding 2π). This excess amount T3 is calculated as "offset value Q2 + gray level value T1 - 256". Therefore, in this modulation pattern Pc2, a phase modulation amount reflection occurs, resulting in a reversal region.

[0087] The grayscale value T4 of the modulation pattern Pc2 in the inverted region is calculated by subtracting the excess T3 from the offset value Q2. That is, the grayscale value T4 of the modulation pattern Pc2 is calculated as "offset value Q2 - (offset value Q2 + grayscale value T1 - 256)". Therefore, the grayscale value T4 here is 174. Furthermore, hereinafter, the grayscale value T1 is sometimes referred to as the grayscale value of the forward rotation region, and the grayscale value T4 is sometimes referred to as the grayscale value of the inverted region.

[0088] When laser L is branched into three processing beams L1, L2, and L3, and without passivation by phase modulation, in the forward rotation region of the diffraction grating pattern Pg, when the gray level value T1 is 82 (phase modulation is 0.64π), the diffraction efficiencies of processing beams L1 and L3 (±1st order) are consistent with those of processing beam L2 (0th order), resulting in output balance among processing beams L1, L2, and L3. Furthermore, under the same conditions, in the reverse rotation region, when the gray level value T4 is 174 (phase modulation is 1.36π), the diffraction efficiencies of processing beams L1, L2, and L3 are also consistent, resulting in output balance.

[0089] On the other hand, in the actual case of passivation due to phase modulation, when the gray level value T1 in the forward rotation region is 89 (with a phase modulation of 0.70π), the diffraction efficiencies of the processing lights L1 and L3, which are ±1st order lights, are consistent with the diffraction efficiency of the processing light L2, which is the 0th order light, resulting in an output balance of processing lights L1, L2, and L3. When the gray level value T1 in the forward rotation region is 89, the gray level value T4 in the reverse rotation region, which corresponds to this gray level value T1, is 167 (refer to the calculation formula above). Moreover, when the gray level value T4 in the reverse rotation region is 167 (with a phase modulation of 1.30π), the output balance of the three processing lights L1, L2, and L3 collapses significantly, and the 0th order light becomes relatively weaker. That is, in the case of passivation due to phase modulation, a deviation in diffraction efficiency occurs between the forward rotation region and the reverse rotation region.

[0090] Here, in relation to Figure 9In the case of the modulation pattern Pc3 formed by the deformation correction pattern Pd that overlaps at least a portion of the diffraction grating pattern Pg as the aforementioned offset patterns Pb1 and Pb2 (adding offset values ​​Q1 and Q2 to the diffraction grating pattern Pg), (refer to...) Figure 10 The forward rotation region R1 and the reverse rotation region R2 coexist. As mentioned above, even if there is a deviation in the diffraction efficiency between the forward rotation region R1 and the reverse rotation region R2, the gray level value can be recalculated based on actual measurements when using the diffraction grating pattern Pg alone, or when the overall gray level value of the modulation pattern is constant.

[0091] However, as Figure 10 As shown, multiple modulation patterns are actually combined or various modulation patterns are switched, making such corrections difficult. Furthermore, when laser L is branched into two processing beams at equal ratios, the grayscale value T1 in the forward rotation region R1 and the grayscale value T4 in the reverse rotation region R2 are both 128, without causing a problem. However, when laser L is branched into two processing beams at different ratios, the same problem occurs.

[0092] In particular, in the context of Figure 11 The diffraction grating pattern Pg shown in (a) imparts a relatively small offset value to the modulation pattern Pc1 (refer to) Figure 11 (b) In this case, the ratio of the forward rotation region R1 to the reverse rotation region R2 is 1:0 (the entire region is the forward rotation region R1). In contrast, in the modulation pattern Pc2 with a relatively large offset value (refer to...), Figure 11 (c) The ratio of the forward rotation region R1 to the reverse rotation region R2 is 0:1 (the entire region is the reverse rotation region R2). Due to the overlap of the pattern and region with the diffraction grating pattern Pg, the deviation in diffraction efficiency increases. Furthermore, Figure 11 The horizontal axis of each curve represents the number (number) of pixels 56p in the liquid crystal layer 56 as the position of the modulation pattern. That is, 256 on the horizontal axis represents the position of the modulation pattern corresponding to the 256th pixel 56p from one end of the liquid crystal layer 56.

[0093] From this perspective, it is argued that if the bias in the ratio of the forward rotation region R1 to the reverse rotation region R2 is suppressed, then the deviations in diffraction efficiency corresponding to the type of synthesized modulation pattern, and the deviations in diffraction efficiency corresponding to each region of the modulation pattern, are suppressed, and the passivation effect of the phase modulation amount is mitigated. Therefore, here, an averaging pattern is used to average the ratio of the forward rotation region R1 to the reverse rotation region R2.

[0094] Figure 12 This is a diagram illustrating an example of an averaging pattern. (For example...) Figure 12As shown, the averaging pattern Ps is a modulation pattern from one end of the averaging pattern Ps to the other end, with the gray level value changing from the minimum value (0) to the maximum value (256) (the phase modulation amount changes from 0 to 2π) at a certain slope.

[0095] Figure 13 This is a diagram illustrating an example of a modulation pattern formed by overlapping and averaging a diffraction grating pattern. Figure 13 (a) shows the modulation pattern Pc4 formed by overlapping and averaging the diffraction grating pattern Pg with the pattern Ps. Figure 13 (b) shows the modulation pattern Pc5 formed by overlapping the diffraction grating pattern Pg with the offset pattern Pb1 and the averaged pattern Ps. Figure 13 (c) shows the modulation pattern Pc6 formed by overlapping the diffraction grating pattern Pg with the offset pattern Pb2 and the averaged pattern Ps.

[0096] In modulation pattern Pc4, the ratio of the forward rotation region R1 to the reverse rotation region R2 is 0.67:0.33; in modulation pattern Pc5, the ratio is 0.67:0.33; and in modulation pattern Pc6, the ratio is 0.73:0.27. In all cases, compared to the case without using the averaging pattern Ps, the ratio of the forward rotation region R1 to the reverse rotation region R2 is averaged. As a result, the bias in the ratio of the forward rotation region R1 to the reverse rotation region R2 is suppressed, the deviation in diffraction efficiency corresponding to the type of synthesized modulation pattern and the deviation in diffraction efficiency corresponding to each region of the modulation pattern are suppressed, and the passivation effect of the phase modulation amount is mitigated.

[0097] Here, the degree of averaging can be adjusted by changing the slope (return period) of the gray level values ​​of the averaging pattern Ps. Figure 12 An example is an example with a slope of 0.5 and a period of 1, where the gray level value increases from 0 to 256 during the period when the position of the averaging pattern Ps changes from 0 to 512. On the other hand, with a period of 2, the slope of the gray level value of the averaging pattern Ps becomes twice that of the averaging pattern Ps. During the period when the position of the averaging pattern Ps changes from 0 to 256, the gray level value increases from 0 to 256, and during the period when the position of the averaging pattern Ps changes from 257 to 512, the gray level value again increases from 0 to 256.

[0098] Figure 14 This is a diagram illustrating an example of a modulation pattern formed by overlapping and averaging a deformation correction pattern. Figure 14 (a) shows the case where the averaging pattern Ps is not used. Figure 14 (b) shows the case where an averaged pattern Ps with a period of 1 is used. Figure 14(c) shows the case where an averaged pattern Ps with a period of 2 is used. Figure 14 (d) shows the case where an averaged pattern Ps with a period of 4 is used. Figure 14 (e) shows the case where an averaged pattern Ps with a period of 8 is used. Figure 14 As shown, the larger the period of the averaging pattern Ps (the greater the slope of the gray level values), the more the phase modulation amount is reflected back, and the bias of the ratio of the forward rotation region R1 to the reverse rotation region R2 is dispersed and averaged. In addition, as an example, the averaging pattern Ps is a shift pattern that has the function of shifting the focus point C of the laser L.

[0099] Next, the inventors' insights related to the second problem and the solution to the second problem in the case of using the spatial light modulator 5 will be explained. Figure 15 This is a schematic diagram illustrating the relationship between a condenser lens and a laser beam. For example... Figure 15 As shown, the focusing lens unit 61 of the focusing section 6 includes a focusing lens 61a for focusing the laser L onto the wafer 20. In the laser processing apparatus 1, by modulating the laser L by the spatial light modulator 5, the focusing position of the laser L can be changed according to the NA region (the radial Kd position of the focusing lens 61a) of the incident laser L, and the focusing point C of the laser L can be shaped into an elongated shape.

[0100] Here, by using Figure 16 The shaping pattern Pf modulates the laser L such that, as the incident position of the laser L at the condenser lens 61a moves further away from the center in the radial direction Kd, the focusing position of the laser L becomes a deeper position in the Z direction (a position further away from the condenser lens 61a). This changes the focusing position of the laser L in the Z direction, thereby shaping the focusing point C of the laser L into an elongated shape in the Z direction. In this shaping pattern Pf, the reflected portion B of the phase modulation amount is formed as concentric circles relative to the region where the laser L is incident (the region corresponding to the incident pupil plane of the condenser lens 61a). That is, in such a shaping pattern Pf, the reflected portion B of the phase modulation amount is biased towards a portion of the shaping pattern Pf.

[0101] Therefore, sometimes the focusing state of laser L deviates between the portion modulated by the portion deflected by the folded portion B in the shaping pattern Pf and the portion modulated without being deflected by the folded portion B. As a result, if other modulation patterns are superimposed on the shaping pattern Pf, and an offset is given to the phase modulation amount of the shaping pattern Pf, the processing result may vary depending on the magnitude of the offset value.

[0102] Figure 17 (a) is an example showing the processing result when the offset value is 64. Figure 17 (b) is an example showing the processing result when the offset value is 96. For example... Figure 17 As shown, the processing result varies depending on the magnitude of the offset value. It is believed that this is because the modulated laser L in the biased portion of the folded-back section B in the shaping pattern Pf becomes an undesirable focused state.

[0103] In contrast, Figure 18 It shows the... Figure 16 The overlapping of the shaping patterns shown Figure 12 A diagram showing a modulation pattern formed by averaging the pattern as shown. (Example) Figure 18 As shown, in the modulation pattern Pe formed by overlapping and averaging the pattern Ps with the shaping pattern Pf, compared with the shaping pattern Pf, the reflected portion B of the phase modulation amount is dispersed to the entire region of the laser L incident in the modulation pattern Pe, and the position of the reflected portion B is averaged.

[0104] Figure 19 This shows that they were used respectively Figure 16 The shaping pattern shown and Figure 18 A cross-sectional photograph of the processing result under the modulated pattern shown. Figure 19 (a) shows the machining result when an offset value of 64 is assigned to the shaping pattern Pf. Figure 19 (b) shows the processing result when an offset value of 96 is assigned to the shaping pattern Pf. Additionally, Figure 19 (c) shows the processing result when the modulation pattern Pe is given an offset value of 64. Figure 19 (d) shows the processing result when the modulation pattern Pe is given an offset value of 96.

[0105] like Figure 19 As shown in (a) and (b), when the averaging pattern Ps is not overlapped with the shaping pattern Pf, the processing result changes if the offset value changes. In contrast, as... Figure 19 As shown in (c) and (d), when the shaping pattern Pf is superimposed with the averaging pattern Ps, the change in the processing result relative to the change in the offset value is small. Thus, by utilizing the averaging pattern Ps, the bias of the folded-back portion B of the phase modulation amount in the modulation pattern can also be suppressed, resulting in the suppression of deviations in the processing result. In the laser processing apparatus 1 of this embodiment, laser processing can be performed using the above insights.

[0106] [An example of laser processing in this embodiment]

[0107] First, as described above, the laser processing apparatus 1 of this embodiment includes: a support 2 for supporting an object 11 (here, a wafer 20); a light source 3 for emitting a laser L; a spatial light modulator 5 for modulating and emitting the laser L emitted from the light source 3 according to a modulation pattern; a focusing unit 6 including a focusing lens 61a for focusing the laser L emitted from the spatial light modulator 5 onto the wafer 20; and a control unit 10 for controlling each part of the laser processing apparatus 1. The control unit 10 inputs an image signal to the spatial light modulator 5, causing the spatial light modulator 5 to display a modulation pattern corresponding to the image signal.

[0108] In this laser processing apparatus 1, during laser processing, the wafer 20 is first supported by a support 2 with its second surface 20b orthogonal to the Z direction. Next, the control unit 10 inputs an image signal to a spatial light modulator 5, causing the liquid crystal layer 56 of the spatial light modulator 5 to display a predetermined modulation pattern. In this state, the control unit 10 controls the light source 3 to emit a laser L, which is then focused onto the wafer 20 from the second surface 20b side by a focusing lens 61a. That is, the laser L is modulated by the spatial light modulator 5, and the modulated laser L is focused onto the wafer 20 from the second surface 20b side by the focusing lens 61a. Thus, a focusing point C of the laser L is formed inside the wafer 20.

[0109] Meanwhile, the control unit 10 controls the movement of the support unit 2 such that the focusing point C of the laser L moves relative to the wafer 20 along the line 15 in the X direction. Thus, while the focusing point C of the laser L moves relative to the wafer 20 in the X direction, the wafer 20 is irradiated with the laser L (performing processing).

[0110] When it is desired to branch the laser L, the control unit 10 can, in this processing, input an image signal containing a second signal corresponding to the diffraction grating pattern Pg into the spatial light modulator 5 in such a way that a modulation pattern containing a diffraction grating pattern Pg (second pattern) for branching the laser L into multiple processing beams L1, L2, L3 is displayed on the spatial light modulator 5. The branching direction of the laser L at this time is, for example, the X direction, which is the processing direction. Furthermore, the image signal corresponding to a certain modulation pattern refers to an image signal in which a gray level value corresponding to the phase modulation amount of each pixel 56p is set in each region of the image signal corresponding to each pixel 56p of the liquid crystal layer 56 of the spatial light modulator 5.

[0111] On the other hand, when it is desired to set the focusing point C of the laser L to be elongated, the control unit 10 can, during the processing, input an image signal containing a third signal corresponding to the shaping pattern Pf into the spatial light modulator 5 in such a way that the modulation pattern containing the shaping pattern Pf (third pattern) for changing the focusing position of the laser L according to the position on the radial Kd of the focusing lens 61a is displayed on the spatial light modulator 5.

[0112] In any of the above-described cases, during processing, the control unit 10 inputs an image signal containing the first signal into the spatial light modulator, causing a modulation pattern containing an averaging pattern Ps (first pattern) corresponding to the first signal to be displayed on the spatial light modulator 5. The grayscale value of the first signal changes from a minimum to a maximum value at a certain slope from the region corresponding to one end of the modulation pattern in the first direction to the region corresponding to the other end of the modulation pattern in the first direction. Therefore, the modulation pattern displayed on the spatial light modulator 5 at this time becomes a modulation pattern composed of at least overlapping diffraction grating patterns Pg and / or shaping patterns Pf and averaging patterns Ps. Similarly, at this time, the image signal input to the spatial light modulator 5 contains grayscale values ​​that at least overlap the grayscale values ​​of the second signal and / or the third signal with the grayscale value of the first signal.

[0113] In particular, during processing, when the laser L is branched into multiple processing beams L1, L2, and L3, the control unit 10 can set the first direction, which is the direction of change of the gray level value of the averaging pattern Ps, to a direction corresponding to the direction intersecting the branching direction of the laser L (or a direction parallel to the branching direction). That is, when the branching direction of the laser L is the X direction, the first direction can be set to a direction corresponding to the Y direction intersecting the X direction (or a direction corresponding to the X direction).

[0114] Alternatively, the control unit 10 may, in the first signal, cause the grayscale level value to change from a region corresponding to one end of the averaged pattern Ps in the second direction, which intersects the first direction, to a region corresponding to the other end of the averaged pattern Ps in the second direction, from a minimum value to a maximum value with a certain slope. As described above, when the first direction is the direction corresponding to the Y direction, the second direction is, for example, the direction corresponding to the X direction. In this case, the spatial light modulator 5 can display an averaged pattern Ps in which the phase modulation amount changes with a certain slope in at least two directions. Furthermore, the slope of the grayscale level value in the first direction and the slope of the grayscale level value in the second direction may be the same or different. For example, when the number of pixels 56p in the liquid crystal layer 56 of the spatial light modulator 5 is different in the two directions, and the phase modulation amount changes from one end to the other in each direction with a certain slope (with the same period), the slope of the grayscale level value in the first direction and the slope of the grayscale level value in the second direction are different in the image signal.

[0115] Furthermore, during processing, the control unit 10 can generate / input an image signal by overlapping other modulation patterns such as the deformation correction pattern and aberration correction pattern of the spatial light modulator 5. In this case, in the spatial light modulator 5, the diffraction grating pattern Pg and the shaping pattern Pf are given offsets corresponding to these other modulation patterns, and the averaging pattern Ps is further overlapped.

[0116] Furthermore, during the processing, when the modulation pattern displayed on the spatial light modulator 5 is superimposed on the averaged pattern Ps as a shift pattern, the focusing point C of the laser L within the wafer 20 sometimes shifts from line 15. Therefore, in this case, the control unit 10 can control the optical axis adjustment unit 4 so that the focusing point C of the laser L is located on line 15. At this time, the control unit 10 can refer to the image acquired by the visual imaging unit 8 (e.g., an image of the second surface 20b of the wafer 20).

[0117] As explained above, in the laser processing apparatus 1, the control unit 10 inputs an image signal into the spatial light modulator 5, causing the spatial light modulator 5 to display a modulation pattern, and performs processing while modulating the laser L according to the modulation pattern. In the image signal, a gray level value corresponding to the phase modulation amount at each position of the modulation pattern is set for each region constituting the image signal. That is, in the spatial light modulator 5, the desired modulation pattern is displayed as a whole by setting the phase modulation amount at each position of the modulation pattern to an amount corresponding to the gray level value of each region of the image signal. Furthermore, the image signal includes a first signal whose gray level value changes at a certain slope from the region corresponding to one end of the modulation pattern to the region corresponding to the other end of the modulation pattern. As a result, the modulation pattern displayed in the spatial light modulator 5 includes an averaging pattern Ps (first pattern) in which the phase modulation amount changes at a certain slope along a direction according to the first signal. As described above, when the modulation pattern includes such an averaging pattern Ps, the passivation effect of the phase modulation amount of the modulation pattern and the bias of the reflected portion B of the phase modulation amount in the modulation pattern can be suppressed.

[0118] Alternatively, in the laser processing apparatus 1, during processing, the control unit 10 may input an image signal containing a second signal corresponding to the diffraction grating pattern Pg into the spatial light modulator 5, in a manner that displays a modulation pattern containing a diffraction grating pattern Pg (second pattern) for branching the laser L into multiple processing beams. In this case, the diffraction grating pattern Pg is superimposed on the modulation pattern. In this case, deviations between the multiple processing beams L1, L2, and L3 can be suppressed.

[0119] Alternatively, in the laser processing apparatus 1, the first direction can also be the direction that intersects with the branch direction of the laser L. In this case, deviations between the processing beams L1, L2, and L3 can be suppressed more effectively.

[0120] Alternatively, in the laser processing apparatus 1, during processing, the control unit 10 may display a modulation pattern, including a shaping pattern Pf (third pattern) that varies the focusing position of the laser L according to the position on the radial Kd of the condenser lens 61a, on the spatial light modulator 5, and input an image signal containing a third signal corresponding to the shaping pattern Pf into the spatial light modulator 5. In this case, in the shaping pattern Pf, it is possible to suppress the deflection of the phase modulation amount B in a manner corresponding to a specific position on the radial Kd of the condenser lens 61a, and to suppress deviations in the focusing state of the laser L.

[0121] Alternatively, in the laser processing apparatus 1, the control unit 10 may, in the first signal, cause the grayscale value to change from a region corresponding to one end of the modulation pattern in the second direction, which intersects the first direction, to a region corresponding to the other end of the modulation pattern in the second direction, from a minimum value to a maximum value with a certain slope. In this case, the grayscale value of the image signal changes with a certain slope in two intersecting directions. Therefore, within the plane of the spatial light modulator 5 corresponding to these two directions, the passivation effect of the phase modulation amount and the bias of the reflected portion of the phase modulation amount can be suppressed.

[0122] Furthermore, in the laser processing apparatus 1, the control unit 10 may change the grayscale level value in the first signal in a manner having multiple cycles in at least one direction. In this case, the passivation effect of the phase modulation amount and the bias of the folded-back portion of the phase modulation amount can be suppressed more reliably.

[0123] The above embodiments illustrate one aspect of the present invention. Therefore, the present invention can be modified without being limited to the above-described embodiments.

[0124] For example, in the above embodiments, in Figure 12 The example given is one where the slope of the grayscale level values ​​is 0.5 and the period is 1. However, the averaged pattern Ps is not limited to this. Figure 20 This is a diagram showing a variation of the averaged pattern. Figure 20 The averaging pattern Ps of the variation of (a) is an example with a slope of 0.25 and a period of 1, such that the gray level value increases from 0 to 256 during the period when the position of the averaging pattern Ps changes from 0 to 1024. Figure 20 The averaging pattern Ps of variation (b) is as follows: During the period when the position of the averaging pattern Ps changes from 0 to 256, the gray level value increases from 0 to 256; during the period when the position of the averaging pattern Ps changes from 257 to 512, the gray level value again increases from 0 to 256, resulting in a slope of 1 and a period of 2. In this example, one foldback occurs. Similarly, in Figure 20 In (c), an example with a slope of 2 and a period of 4 is shown. Thus, the slope and period of the averaging pattern Ps can be arbitrarily set. Furthermore, the direction with period is not limited to one direction; it can also be two directions.

[0125] Furthermore, in the above embodiments, in Figure 16 The example illustrates a shaping pattern Pf used to shape the focusing point C of laser L into an elongated strip in the Z direction. However, the shaping pattern Pf is not limited to this, such as... Figure 21 As shown in the figures, it can be arbitrarily deformed in a way that reshapes the focal point C.

[0126] Here, when processing is performed by branching the laser L into multiple processing beams as described above, the aforementioned countermeasure (first countermeasure) against the deviation in output balance between the processing beams is effective. On the other hand, when processing is performed in this way, the countermeasure (second countermeasure) against the influence of the unmodulated light in the laser L that is not modulated by the spatial light modulator 5 on the focusing state of the 0th order light (e.g., processing light L2) generated by the branching is effective.

[0127] The averaging pattern Ps has the function of shifting the focus point C of the laser L. In the processing, when the wafer 20 is arranged with the street region 23 along the X direction, and the focus point C of the laser L is moved relatively in the X direction within the street region 23, the first countermeasure and the second countermeasure mentioned above can be addressed by setting the averaging pattern Ps to shift the focus point C in the Y direction.

[0128] However, as a first countermeasure, the averaging pattern Ps can shift the focal point C in the Y direction by a relatively small amount, such as 2 μm. In contrast, as a second countermeasure, the averaging pattern Ps is more effective at shifting the focal point C in the Y direction by a relatively large amount, such as 5 μm or more. Moreover, from the viewpoint of suppressing interference between the 0th order light and the unmodulated light, the second countermeasure is only needed when using the 0th order light.

[0129] Therefore, in the first case where branching is not performed, in the second case where branching is performed but no 0th-order light is used, and in the third case where branching is performed using 0th-order light, the required displacement in the Y direction differs. More specifically, in the first case, it is not necessary to shift the focus point C in the Y direction to address at least the first and second countermeasures; in the second case, the second countermeasure is not required, so the displacement in the Y direction can be suppressed to the level of 2 μm for the first countermeasure; and in the third case, it is desirable to further consider the second countermeasure and set the displacement in the Y direction to the level of 5 μm or more. Therefore, the laser processing apparatus 1 is configured to handle these first to third cases.

[0130] That is, in the laser processing apparatus 1, the optical axis is adjusted by using the state of the averaged pattern Ps with a displacement of 5 μm in the Y direction as the default, thereby using the state in which all the focusing points of the laser L are shifted by 5 μm in the Y direction as the reference position. Thus, in all cases from the first to the third, the necessary countermeasures in the first and second countermeasures can be dealt with.

[0131] However, in this situation, the following new problem may arise. That is, if the width of street area 23 in the Y direction is narrow, such as... Figure 22As shown, if the focus points C1, C2, and C3 of the multiple processing beams L1, L2, and L3 of laser L are shifted in the Y direction by a displacement of 6 μm by a distance Ds, the focus point C0 of the unmodulated beam is located on the functional element 22a (active region) facing the street area 23, which may cause light leakage problems.

[0132] As a countermeasure to this new problem, in the laser processing apparatus 1, firstly, the optical axis is adjusted by default using an averaged pattern Ps with a Y-direction shift of 2 μm, thereby addressing the first countermeasure. This appropriately addresses the first case of not performing branching processing and the second case of not using level 0 light. On the other hand, in the third case of performing branching processing using level 0 light in the laser processing apparatus 1, relative to the default averaged pattern Ps with a Y-direction shift of 2 μm, the grayscale level is further set to produce an X-direction shift of 5 μm, thereby achieving the desired effect. Figure 23 As shown, the focusing points C1, C2, and C3 can be shifted in both the X and Y directions. In this case, the shift in the Y direction can be suppressed, and the total shift Ds in the X and Y directions can be sufficiently increased to address the second problem.

[0133] Furthermore, in laser processing apparatuses, the shift direction of the focal point C in the X direction can be switched, for example, by reversing the sign of the slope of the grayscale level values ​​of the averaging pattern Ps, depending on whether the shift direction (processing direction) of the focal point C is in the positive X direction or the negative X direction. As an example, when the processing direction is in the positive X direction, the shift direction of the focal point C can also be set to the positive X direction, and when the processing direction is in the negative X direction, the shift direction of the focal point C can also be set to the negative X direction.

[0134] Furthermore, in the above embodiments, it was explained that the averaging pattern Ps has the function of shifting the focusing point C of the laser L along the X or Y direction, but the averaging pattern Ps can also have the function of shifting the focusing point C of the laser L along the Z direction.

Claims

1. A laser processing apparatus, wherein, It is a laser processing apparatus used to form a modified region on an object by irradiating the object with a laser. The laser processing apparatus includes: A support portion, which is used to support the object; A light source, which is used to emit the laser; A spatial light modulator for modulating and emitting laser light emitted from the light source according to a modulation pattern; A focusing section includes a focusing lens for focusing the laser emitted from the spatial light modulator toward the object; as well as The control unit inputs an image signal into the spatial light modulator, causing the spatial light modulator to display a modulation pattern corresponding to the image signal. The control unit, by controlling the movement of at least one of the support unit and the focusing unit, performs a processing procedure in which the focusing point of the laser is moved relative to the object along the X direction along the laser incident surface of the object while irradiating the object with the laser. In each region constituting the image signal, a gray level value corresponding to the phase modulation amount of the modulation pattern is set. In the processing, the control unit inputs the image signal containing the first signal into the spatial light modulator, causing the spatial light modulator to display the modulation pattern containing the first pattern corresponding to the first signal, wherein the gray level value of the first signal changes from a minimum value to a maximum value at a certain slope from the region corresponding to one end of the modulation pattern in the first direction to the region corresponding to the other end of the modulation pattern in the first direction.

2. The laser processing apparatus according to claim 1, wherein, In the processing, the control unit inputs an image signal containing a second signal corresponding to the second pattern into the spatial light modulator in such a way that the modulation pattern, which includes a second pattern for branching the laser into multiple processing beams, is displayed on the spatial light modulator.

3. The laser processing apparatus according to claim 2, wherein, The first direction is the direction that intersects with the branching direction of the laser.

4. The laser processing apparatus according to any one of claims 1 to 3, wherein, In the processing, the control unit inputs an image signal containing a third signal corresponding to the third pattern into the spatial light modulator in such a way that the modulation pattern containing the third pattern is displayed on the spatial light modulator, wherein the third pattern is used to change the focusing position of the laser according to the radial position of the focusing lens.

5. The laser processing apparatus according to any one of claims 1 to 4, wherein, The control unit, in the first signal, causes the grayscale level value to change from a minimum to a maximum value at a certain slope from the region corresponding to one end of the second direction intersecting the modulation pattern and the first direction to the region corresponding to the other end of the second direction of the modulation pattern.

6. The laser processing apparatus according to any one of claims 1 to 5, wherein, The control unit, in the first signal, causes the grayscale level value to change in a manner having multiple cycles in at least one direction.

Images