JP2006173520A - Laser fracture method and member to be fractured which can be fractured by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the variation of the formation of an internal work area in fracturing a member to be fractured provided with a structure on a surface by condensing a laser beam to the inside. <P>SOLUTION: The surface of the member to be fractured is irradiated with a laser beam such that the structure 2F provided on the surface of the member to be fractured does not enter the luminous flux of the laser beam LB made incident on the surface of the member 10 to be fractured. In the case of defining the height of the end part of the structure 2F on the side of the laser beam flux emitted toward the inside of the member to be fractured as h, an angle formed by the laser beam with the perpendicular of the surface 12 outside the member to be fractured as θ1, an angle formed by the laser beam with the perpendicular of the surface 12 inside the member to be fractured as θ2, and a distance from the laser beam irradiation surface of the surface 12 of the member to be fractured to a laser condensing point A inside as L, when a distance between a fracture line C and the structure 2F as (a), (a)>h×tanθ1+L×tanθ2 is defined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser cleaving method that condenses laser light inside a laser cleaving member and cleaves the laser cleaving member so that the surface of the laser cleaving member is separated into a plurality of regions, and a laser cleaving member that can be cleaved by the method. It is about.

  There is a technique for separating the surface of a member to be cut into a plurality of regions by condensing the laser beam inside the member to be cut and cleaving it. For example, when a semiconductor substrate such as a silicon wafer is precisely cut into a chip shape, for example, a circumferential blade having a width of several tens to several hundreds of μm is conventionally rotated at high speed, and the abrasive on the blade surface is the substrate. A blade dicing method is known which cuts by grinding. At this time, in order to reduce heat generation and wear associated with cutting, cooling water is sprayed on the cut surface. Chips of the substrate itself, fine particles of abrasive material generated by cutting, adhesive for fixing the substrate and the processing table are fixed. Garbage such as adhesive particles on the tape mixes with the cooling water and scatters over a wide area. In particular, when the substrate is a semiconductor substrate, a large number of fine functional elements are formed on the surface of the substrate, which may seriously affect the reliability of the functional elements themselves.

In order to solve this problem, it is desirable that the cutting can be performed in a dry environment without using cooling water. Therefore, a processing method for cutting the substrate by condensing a highly absorbing laser beam inside the substrate has been proposed. For example, the methods disclosed in Patent Document 1 and Patent Document 2 are applied to a substrate that is a material to be processed. This is because the internal modified layer formed by condensing laser light with a specific wavelength with high transparency inside the glass substrate or silicon substrate is used as the starting point for cutting, and it does not form a melting region on the substrate surface. It is possible to cut with less.
JP 2002-192370 A JP 2002-205180 A JP 2003-334675 A

  However, in the laser cleaving method described above, it is necessary to irradiate the laser beam so that it is focused inside the cleaved member after passing through the objective lens. When trying to cleave by condensing the laser beam inside, there was a variation in the size of the internal processing area formed by laser light irradiation inside the cleaved member, and the size was smaller than the desired size In some cases, the processing region or a portion where the processing region itself is not formed may occur, which may cause a problem that the cutting / separation of the member to be cut is hindered or the member is cleaved / separated at an unexpected position. This was remarkable in the case of processing by condensing the laser beam deep inside the member to be cut.

  In particular, what is disclosed in Patent Documents 1 and 2 is a silicon substrate having a thickness of 350 μm, on which no structures such as semiconductor circuits, wiring patterns, or electrodes are formed on the front and back surfaces. Using such a silicon substrate, the laser beam is simply condensed inside the silicon substrate to form an internal modified layer and cleaved. In other words, until now, when a silicon substrate is cleaved as a member to be cleaved, the focus is on the search for irradiation conditions such as the wavelength of the laser beam, energy, and pulse frequency as to how thick the substrate can be cleaved. It has been done.

  In practice, however, when such a silicon substrate is cleaved, it is usual that a large number of elements such as semiconductor circuits are arranged on the surface thereof. When such a silicon substrate is cleaved by laser light irradiation, a cleavage line is assumed on the surface of the silicon substrate exposed between the structures formed on the silicon substrate surface. Then, the laser beam is irradiated along the breaking line. At this time, it is necessary to consider the existence of a structure provided on the surface irradiated with the laser beam. In particular, in the case where the substrate is not so thick and in the case where the substrate is relatively thick, the height of the structure from the substrate surface also has a significant effect on good substrate cleaving. In particular, when the member to be cut that is thicker than the silicon substrate is cut, the above-described problem becomes particularly significant.

  The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and in particular, has been made paying attention to the height from the surface of the structure provided on the surface of the member to be cut. . In the present invention, when a member to be cleaved having a structure formed on the surface is cleaved between the structure and the structure by laser light irradiation, the cleaved member is surely cut at a place intended to be cleaved. An object is to provide a laser cleaving method that can be separated and a cleaved member that can be cleaved by the method.

  In order to achieve the above object, the laser cleaving method of the present invention is configured such that a laser beam is incident from one surface of a cleaved member provided with a plurality of structures on each of the front and back opposing surfaces. An internal processing region is formed by condensing light to a condensing point at a predetermined depth inside, and the member to be cut is cut along a cutting line so that the surface of the member to be cut is separated into a plurality of regions. In the laser cleaving method, the interval between the structures provided on the one surface is wider than the interval between the structures provided on the other surface. The member to be cut is irradiated with laser light so that the structure does not enter. Furthermore, the height of the end of the structure on the laser beam side irradiated toward the inside of the member to be cut is h, the angle between the laser beam and the perpendicular of the surface outside the member to be cut is θ1, and the laser When the angle between the light and the perpendicular to the surface inside the cleaved member is θ2, and the distance from the laser light irradiation surface on the surface of the cleaved member to the internal laser focusing point is L, the cleaved line A> h × tan θ1 + L × tan θ2, where a is the distance between the structure and the structure.

  Moreover, the to-be-cut member of this invention has the 1st structure provided in the surface, and the several 2nd structure provided in the back surface facing the said surface, Said 1st structure A member to be cut along a cutting line connecting between the body and the second structure, and the member to be cut is cleaved by condensing laser light from the surface to the inside. The height of the end of the second structure on the side of the laser beam irradiated toward the inside of the member to be cut is h, and the laser beam is perpendicular to the back surface outside the member to be cut. In the case where θ1 is an angle, θ2 is an angle between the laser beam and the perpendicular to the back surface inside the cleaved member, and L is a distance from the laser light irradiation surface on the back surface to the internal laser focusing point, Assuming that the distance between the breaking line and the second structure is a, a> h × tan θ1 + × characterized in that it is a tan [theta] 2.

  According to the present invention, when cleaving by condensing a laser beam inside a cleaved member having a structure formed on the surface, a desired internal processing region can be formed, and cleaving is performed at a predetermined position. Can do.

  Embodiments of the present invention will be described below with reference to the drawings. In the description of the present invention, the present invention will be described with reference to a member to be cut according to the present invention, in which the member to be cut is of a form that requires higher cutting accuracy when cleaving by condensing laser light inside. explain.

  1A, the first member 1F is formed on the front surface 11 of the silicon substrate 10 and the second structure 2F is formed on the back surface 12, and the first structure 1F on the front side and the first structure 1F on the back side. A plurality of elements E each having two structures 2F are formed on the silicon substrate 10 in a grid pattern. As shown in FIG. 1B, on the surface of the silicon substrate 10, there is a breaking line C between the element E and the element E, which is a position where the breaking for separating each element from the silicon substrate 10 is performed. Assumed. In the following, the breaking line is assumed to exist in an arbitrary direction on the section after the breaking. For example, it may be a breaking line along the substrate surface or a breaking line along the thickness direction of the substrate.

  Furthermore, FIG. 1C schematically shows a cross section taken along line AA in FIG. The first structure 1F of the element E includes a logic circuit 1 that drives a liquid ejection head (inkjet head) that ejects a liquid such as ink, a flow path forming member 2, and an ejection port 3, while the element E The second structure 2F has bumps 4 that are wiring electrodes. A through electrode 6 is formed between the first structure 1F and the second structure 2F so as to penetrate the silicon substrate 10 from the front to the back. By electrically connecting the bump 4 and the logic circuit 1 to each other, an electric signal can be obtained. The driving power can be supplied to the logic circuit 1 from outside the head.

  The first structure 1 </ b> F is a structure in which the flow path forming member 2 occupies most of the size. In order to obtain a large number of elements E from one silicon substrate 10, the interval between the first structures 1 </ b> F. Is set narrow in a range that does not interfere with the cleaving performed in the subsequent process. On the other hand, since the member that determines the size of the second structure 2F is the bump 4, the interval between the second structures 2F is larger than the interval between the first structures 1F. As a result, the distance between the first structure 1F and the breaking line C is smaller than the distance between the second structure 2F and the breaking line C (see FIG. 1C). The wider the interval between the structures, the more the laser beam having a constant incident angle can be condensed deep inside the member to be cut so as not to hit the structure. For such structural reasons, the laser beam LB is irradiated and condensed from the back surface 12 side of the silicon substrate 10.

  Next, an embodiment of the present invention will be described with reference to FIG.

  Phenomena such as variations in the size of internal processing regions and defective processing formation that may have occurred when concentrating a laser beam inside a member to be cut having a structure formed on the surface are broken by the present inventors. According to these experiments and examinations, when the structure formed on the surface of the member to be cut is irradiated with laser light and condensed inside the object to be cut, a part of the laser beam is blocked by the surface structure. Because the loss of laser power occurs when passing through the structure and the energy at the condensing point is reduced, the size of the internal processing area formed inside the object to be cut varies. I found out.

  Therefore, in order to perform good cleaving without the occurrence of such a phenomenon, a structure provided on the surface of the member to be cut is included in the light beam of the laser light incident on the surface of the member to be cut. It was found that the laser beam should be applied to the irradiated surface of the member to be cut so as not to enter. That is, when the case where the laser beam is irradiated perpendicularly to the irradiation surface of the member to be cut is considered, along the back-side surface 12 from the end of the second structure on the side of the light beam of the laser beam LB to the light beam of the laser beam LB. Α is the shortest allowable distance, h is the height of the highest portion of the second structure end on the laser beam side, θ1 is the angle that the laser beam LB is perpendicular to the back surface 12 outside the substrate, and the laser beam LB is the substrate The angle formed with the perpendicular to the back surface 12 inside is θ2, the substrate thickness at the cleaving position is t, the distance between the condensing point A closest to the surface of the laser beam LB on the output side and r is the laser beam irradiation When the distance from the surface (the surface of the member to be cut irradiated to the laser beam and also referred to as the laser beam incident surface) to the laser focusing point A is L, the cutting line C and the second structure 2F L <tr, and a ≧ h × tan θ Good cleaving can be performed by irradiating and condensing the laser beam under conditions determined so that the relationship of 1 + L × tan θ2 + α is established. Here, α takes into consideration the manufacturing error of each structure and the error in the positional accuracy of the irradiation system of the laser beam LB. Therefore, at least L <tr and a> h × tan θ1 + L × tan θ2. If it is good.

  Next, the laser beam LB is irradiated and condensed at a predetermined depth inside the silicon substrate 10 aiming at the breaking line C assumed between the second structure 2F and the second structure 2F. Let And while forming the internal crack 14 (14a-14c) and the internal process area | region formed, it scans along the cutting line C (relative movement), condensing the laser beam LB inside a board | substrate, and a breaking line A crack group including a plurality of cracks arranged in a strip shape along C is formed.

After or before the formation of such a crack group, a concave surface processing mark 13 which is a linear processed portion by scribing or the like is formed on the back surface 12 of the substrate along the breaking line C (C ₁ , C ₂ ). Surface treatment is performed.

  When an external force for cleaving is applied to the silicon substrate 10 after the formation of the surface processing mark 13 and the formation of the internal processing region by the laser beam LB, stress concentrates on the surface processing mark 13 and the surface processing mark 13 and the internal crack 14c. Are connected by cracks, so that the actual breaking line generated on the back surface 12 does not deviate from the breaking line C.

  A silicon substrate 10 shown in FIGS. 1A and 1B is, as shown in FIG. 1C, single crystal silicon having a (100) surface and a silicon wafer 10 having a thickness of 200 μm as a base, On the front surface 11 of the silicon wafer 10, there are a logic circuit 1 that drives an energy generator for discharging liquid such as ink, a flow path forming member 2 that is a structure made of an epoxy resin containing wiring and the like, and an ink discharge port 3. It arrange | positions and comprises the 1st structure 1F. The corresponding back side surface 12 is provided with wirings and bumps 4 electrically connected to the logic circuit 1 through the through electrodes 6 penetrating the inside of the silicon substrate, and constitutes the second structure 2F.

  In this way, a liquid supply port (ink supply port) 5 that is an opening is formed by dry etching of a silicon wafer (silicon substrate) 10 immediately below the flow path forming member 3 containing a liquid discharge energy generator and the like. . The flow path forming member 2 is arranged with a breaking line C sandwiched therebetween so that the silicon wafer 10 can be broken into the element chips E at the end of the manufacturing process. The breaking line C is formed along the crystal orientation of the silicon wafer 10, and the interval S1 between the adjacent flow path forming members 2 is about 20 μm at the minimum. The distance S2 between the wirings or bumps 4 arranged on the back surface 12 side is 150 μm, which is larger than S1.

  Here, the element E is formed on the silicon wafer 10 so that the direction of the orientation flat 10b and the short side of the element E are parallel to each other as shown in FIG. The shape of each element E is, for example, a short side of 0.5 mm to 1.0 mm and a long side of 25 mm to 35 mm.

  FIG. 5 is a flowchart for explaining a cleaving process for separating the silicon substrate 10 into individual element chips E. This process includes a tape mounting process in Step 1, a wafer correction process in Step 2, and a surface recess processing process in Step 3. (Surface processing trace formation process), Step 4 includes internal crack formation process (internal processing region formation process), Step 5 cleaving process, Step 6 repair process, and Step 7 pickup process.

  Each step will be described below in order.

[Tape mounting process]
As shown in FIG. 6, the silicon substrate 10 is first tape-mounted to prevent the element E from being separated from the silicon substrate 10 in the process up to cleaving. In the tape mount, the first structure 1F including the ink discharge port 3 and the logic circuit 1 of the silicon substrate 10 is attached to the dicing tape T on which the dicing frame M is attached and the adhesive layer 201 is held on the tape base material 202. This is achieved by pasting the front side surface 11 on which is formed. This is because the laser beam LB is irradiated from the side of the back surface 12 where the second structure 2F is provided, where the distance between the breaking line C and the structure provided on the silicon surface is wide.

  As the dicing tape, an adhesive tape coated with an ultraviolet curable or pressure sensitive adhesive or an adhesive tape having a self-adhesive layer is used. The first structure 1F having the flow path forming member 2 on the silicon substrate 10 has a thickness of 20 μm, and the uppermost surface of the flow path forming member on which the ink discharge ports 3 are formed discharges liquid. The water-repellent treatment is applied for stabilization, and the adhesiveness with the adhesive material having the characteristic that the adhesiveness is lowered by ultraviolet rays is not so good. Therefore, in order to attach the dicing tape T to the front surface 11 of the silicon substrate 10, the adhesive layer 201 having a thickness of 40 μm is used. Accordingly, the adhesive layer 201 can be in contact with the side surface of the flow path forming member 2 that has not been subjected to the silicon substrate 10 or the water repellent treatment, and the element E described later can be easily separated.

[Wafer correction (warp correction) process]
As described above, the flow path forming member 2 that is a resin layer formed on the surface of the silicon substrate 10 undergoes thermal shrinkage at the time of curing, so that the entire silicon substrate 10 is deformed as shown in FIG. . When the laser irradiation described later is performed in such a deformed state, the incident angle is locally different on the back surface 12 and it cannot be processed with high accuracy. Therefore, it is necessary to correct this deformation in advance. Therefore, as shown in FIG. 7B, the silicon substrate 10 is sucked from the dicing tape T side using the suction stage D, thereby flattening the silicon substrate 10 and correcting the deformation.

[Surface recess processing step]
Subsequently, in order to cleave each element E of the silicon substrate 10 with high accuracy, a surface processing mark 13 is formed on the back surface 12 of the substrate, which is a recess that induces propagation of cracks in the cleaving line C. That is, by forming the surface processing mark 13 along the cutting line C, stress concentration occurs when cleaving by an external force, and a crack is induced to the surface processing mark 13. Or the surface processing trace 13 becomes a starting point, and a crack progresses inside. Therefore, unnecessary cracks that destroy the logic circuit 1 and the like do not occur.

  As shown in FIG. 8, the surface processing trace 13 may be formed by marking with a scriber using a tool 40 such as a cemented carbide blade or a diamond blade along the breaking line C. The surface processing mark 13 preferably has a width of 2 μm or more and a depth of 1 μm or more. However, it is necessary to have a size that does not interfere with the optical path of the laser beam LB for processing the internal crack 14. As the processing depth, a depth that causes stress concentration between the surface processing mark 13 and the crack 14 at the time of cleaving is suitable.

  The surface processing trace 13 may be formed after the internal crack formation step by the laser beam LB. In this case, the influence of the vignetting of the laser beam LB at the time of the internal crack formation (the surface of the concave recess on the surface on which the surface processing trace is formed) Since there is no phenomenon in which the amount of laser light that reaches the inside of the substrate by reflecting the irradiated laser light does not occur, internal cracks can be formed more efficiently.

[Internal crack formation process]
The internal crack (internal processing region) 14 shown in FIG. 3 is formed using the processing apparatus 50 shown in FIG. This processing apparatus 50 includes a light source optical system having a light source 51, a beam expanding system 51a, a mirror 51b, a condensing optical system 52 having a microscope objective lens 52a, a mirror 52b, and the like, an X stage 53a, a Y stage 53b, An automatic stage 53 having an adjustment stage 53c and the like and an alignment optical system (not shown) that performs alignment by the orientation flat 10b (see FIG. 1) of the silicon substrate 10 as the work W are provided.

  As the light source 51, a fundamental wave (1064 nm) of a pulse YAG laser is used. The pulse width is around 15 nsec to 1000 nsec, and the frequency is 10 KHz to 100 KHz. The laser excitation source is a semiconductor laser, and the power of the laser can be changed by an injection current to the semiconductor laser. The pulse width can be changed by changing the amount and frequency of the injected current.

  The selection of the laser light is determined by the spectral transmittance of the silicon substrate. For this reason, light having a wavelength range in which a strong electric field can be formed at the condensing point and silicon permeability is not necessary.

  The laser beam LB emitted from the light source 51 enters the condensing optical system 52 through the beam expanding system 51a and the like.

  As the microscope objective lens 52a of the condensing optical system 52, for example, one having a magnification of 20NA0.42 or a magnification of 50NA0.55 is used. In addition, in consideration of the refractive index of silicon, it is possible to use a condensing lens optimal for silicon internal processing that can be applied to microscopic observation. As shown in FIG. 4, the laser light LB focused on the workpiece W by the focusing optical system 52 and the second structures 2 </ b> F and the second structures 2 </ b> F on the back surface 12 of the silicon substrate 10 that are the workpiece W on the automatic stage 53. Incident from between the structures 2F.

  The optical conditions at this time are set so that the surface processing mark 13 may exist on the back side surface 12. That is, measures are taken such as increasing the power in consideration of energy loss due to the surface processing mark 13 or selecting the light flux so as to be incident while avoiding the surface processing mark 13. The light beam of the laser beam LB incident from the back surface 12 of the substrate is refracted in the silicon substrate 10 and is condensed at a condensing point A at a predetermined depth L inside to generate an internal crack 14. The internal crack 14 is a crack extending from the condensing point A of the laser beam LB in a direction approaching and separating from the substrate surface, and reforms the material at the condensing point (dissolution, change in crystal structure, cracks). It is formed in the internally processed region.

  According to the experiment, the processing conditions are set according to the condensing position, the laser wavelength to be used, etc. so that the crack tip of the innermost crack 14c shown in FIG. 3 is separated from the back surface 12 of the substrate by 10 μm or more. Is desirable. This is because the internal crack 14c and the back side surface 12 may be inadvertently connected during processing, or the back side surface 12 may be damaged depending on the laser irradiation conditions.

  The depth L of the condensing point A can be controlled by moving either the work W, which is the silicon substrate 10, or the condensing optical system 52 in the optical axis direction and shifting the condensing position. When the refractive index with respect to the wavelength of 1064 nm of the silicon substrate 10 is n and the mechanical movement amount (movement amount when either the silicon substrate 10 or the condensing optical system 52 is moved in the optical axis direction) is p, The optical movement amount of the condensing point A is np. The refractive index of the silicon substrate 10 is near 3.5 at a wavelength of 1.1 μm to 1.5 μm, and n is close to 3.5 when compared with the refractive index value actually measured in the experiment. That is, when the mechanical movement amount is 100 μm, the condensing point A of the laser beam LB is formed at a position of 350 μm from the surface.

In addition, the fact that the refractive index is in the vicinity of 3.5 indicates that the reflectance is large. In general, the reflection at normal incidence is ((n−1) / (n + 1)) ² , and is about 30% in the silicon substrate. Although the remaining energy reaches the inside, the final energy at the condensing point is further reduced because there is also light absorption of the silicon substrate. When measured on a silicon substrate having a thickness of 200 μm, the transmittance was about 30%.

  When the laser beam LB is condensed at the condensing point A, the crystal state of silicon partially changes, and as a result, the internal crack 14 runs. In the experimental results, the crack length d was about 2 μm to 100 μm. Here, the size of the internal processing region 14 inside the substrate by the laser beam LB, for example, the crack length d can be changed by changing the oscillation pulse width of the laser beam LB. In the semiconductor laser pumped YAG laser, the crack length d can be changed by changing the current injected into the semiconductor laser and the oscillation frequency. From the experimental results, when the pulse energy of the laser was changed within the range of 2 μJ to 100 μJ and the pulse width was changed within the range of 15 nsec to 1000 nsec, it was possible to form a crack with a varying length within the range of 2 μm to 100 μm. It was.

  At this time, when the laser beam LB is irradiated perpendicularly to the back surface 12 of the silicon substrate 10, the back surface 12 from the end of the second structure on the side of the beam of the laser beam LB to the beam of the laser beam LB. Α is the shortest allowable distance along the laser beam, h is the height of the highest portion of the second structure end on the laser beam side, θ1 is the angle between the laser beam LB and the perpendicular of the back surface 12 outside the substrate, and the laser beam LB Is the perpendicular to the back surface 12 inside the substrate, θ2 is the thickness of the substrate at the cleaving position, r is the distance between the condensing point A closest to the surface of the laser beam LB on the output side and the surface on the output side, r When the distance from the light irradiation surface to the laser focusing point A is L, if the distance between the breaking line C and the second structure 2F is a, L <tr and a ≧ h × Under conditions determined so that the relationship of tan θ1 + L × tan θ2 + α is established. Irradiate and collect laser light. Here, when the condensing point of the laser beam LB is too close to the emission side surface, a crack directly formed on the emission side surface by the irradiation of the laser beam LB reaches the emission side surface, and the fine crushing dust or Since the melt is ejected to the exit side surface, it is necessary to maintain a certain distance between the condensing point A and the exit side surface. Therefore, it is preferable that the relationship of L <tr is satisfied.

  For example, a flow path forming member 2 having a height of 75 μm is formed on one surface of a silicon substrate having a thickness of 200 μm on the front side surface 11 at intervals of 20 μm, which is a design minimum value, and is formed on the corresponding back side surface 12. A bump 4 having a height of 20 μm is formed. Here, if the interval between the bumps 4 considered as the second structure 2F is 150 μm at a location across the breaking line C, the distance from the breaking line C to the bump 4 is 75 μm. The silicon substrate 10 is irradiated with a laser beam LB from the back surface 12 side in a cleaving process described later. At this time, by setting the NA of the objective lens 52a to 0.6, the angle between the laser beam LB irradiated to the silicon substrate 10 and the breaking line C outside the substrate can be set to 33 °. The angle between the laser beam LB and the breaking line C is about 9 ° from the refractive index of the light with respect to silicon. Then, by using a fundamental wave (1064 nm) of a YAG laser having a pulse width of around 15 nsec to 1000 ns and a pulse frequency of 10 KHz to 100 KHz as a laser light source, a back side surface 12 of an internal processing region formed inside the silicon substrate 10 is used. The length in the depth direction from the surface can be about 60 μm. Here, when the focal point of the laser beam LB is set to the deepest position from the back side surface 12 which is the incident side surface as much as possible, 10 μm is secured as the distance between the crack and the emission side surface 11 (described above). As described above, since the crack does not reach the exit side surface, the value of h × tan θ1 + L × tan θ2 is about 43 μm. Here, if the shortest allowable distance α along the surface is set to 10 μm, the added dimension is about 53 μm. This value is 75 μm or less, which is the distance from the breaking line to the bump on one side, and can satisfy the relationship of a ≧ h × tan θ1 + L × tan θ2 + α, at least the relationship of a> h × tan θ1 + L × tan θ2.

  As a result, the variation in the size of the internal processing region that may have occurred when the laser beam LB is condensed and cleaved inside the cleaved member such as the silicon substrate 10 on which various structures are formed, A phenomenon such as poor processing formation is caused by the fact that each of the structures formed on the surface of the silicon substrate 10 focuses the laser beam LB on the surface structure when the laser beam LB is condensed inside the substrate. Since the laser beam LB is no longer transmitted or the laser beam LB is not transmitted through the structure, desired energy can be transmitted to the condensing point, and it is not generated.

Next, the irradiation position on the substrate surface of the laser beam forming the internal processing region is relatively moved along the substrate surface, and the internal processing region is formed in a direction along the substrate surface. Specifically, the internal crack 14 is formed from one point inside the silicon substrate 10, and the condensing point A is relatively moved along the breaking line C to perform internal processing immediately below the breaking line C. As shown in FIG. 1, the breaking line C of the silicon substrate 10 includes two-direction breaking lines C ₁ and C ₂ that are orthogonal to each other with the orientation flat 10b as a reference.

  The workpiece W, which is the silicon substrate 10, is placed on an automatic stage 53 that can move in the XY directions, and can move in the optical axis direction (depth direction) toward the automatic stage side on which the workpiece W is placed or the condensing optical system side. A Z stage 52c is provided, and the interval between the condensing optical system 52 and the workpiece W is variable.

  The moving speed in the XY directions is determined in consideration of the laser oscillation frequency, crack shape, and the like, and the moving speed is generally 10 mm / sec to 100 mm / sec at a normal frequency of 10 KHz to 100 KHz. When the moving speed exceeds 100 mm / sec, the internal machining region (crack) jumps in the moving direction, and affects the subsequent cleaving, such as the gap between adjacent cracks on the same cleaving line being remarkably wide.

  Further, the condensing optical system 52 has an observation camera 52d so as to be conjugate with the workpiece irradiation point. On the other hand, the reflectance of the silicon substrate 10 is about 30%. Will be damaged. Therefore, a filter corresponding to the output of the laser is arranged. The illumination for observation uses a relay lens so that a light source can be formed at the position of the entrance pupil of the microscope objective lens 52a used for condensing so that Koehler illumination can be formed. In addition, illumination is also performed through a filter to eliminate damage to the illumination optical element as much as possible.

  In addition to the observation optical system described above, an AF optical system 54 is introduced to measure the distance from the workpiece W. The AF optical system 54 obtains the contrast of the image obtained by the observation camera 52d, and measures the focus and tilt from the obtained value. Actually, in order to measure this contrast, the distance to the workpiece W is measured while being finely fed to determine the best position. Note that it is determined whether or not the AF operation is performed in view of the parallelism of the workpiece W that is the silicon substrate 10.

  In addition, since the crack length d formed at one condensing point A is 2 μm to 100 μm and the thickness of the target silicon substrate is 200 μm, in order to cleave this silicon substrate, a plurality of times Processing is effective for good cleaving. Further, the order of internal processing at one point starts from the far side (back side) from the substrate surface on the incident side of the laser beam LB and approaches the incident side surface. Here, at the time of internal processing for forming internal cracks, processing is not performed in which internal cracks formed in the vicinity of the substrate surface reach the substrate surface having surface processing marks. Specifically, the crack group of the internal crack 14 c closest to the back side surface 12 is provided at a depth of 10 μm to 100 μm from the back side surface 12 and not communicating with the surface processing trace 13.

  In internal processing, it is effective to change the ratio of the area where the crack is formed to the substrate thickness and the position of the crack depending on the purpose. For example, the external force required for cleaving can be changed by changing the ratio of the area where the crack is formed to the substrate thickness. When a crack is formed inside a silicon substrate having a thickness of 200 μm, the external force required to cleave the portion where the area where the crack group is formed accounts for 40% or less is W Assuming [N], the external force necessary for cleaving the area where the cracked region occupies 70% or more of the substrate thickness was about 0.6 W [N]. . In order to cleave the substrate with a relatively small external force in the cleaving step, it is desirable to increase the ratio of the cracked region to the substrate thickness, for example, 70% or more. Further, after the internal processing of the silicon substrate 10 by irradiation with the laser beam LB, when the processed silicon substrate 10 is transported to a cutting station, it is preferable that the element E is not yet separated from the silicon substrate 10 at this stage. However, when importance is attached to handling stability, for example, in order not to cause inadvertent cracks, it is effective to reduce the ratio of the area where cracks are formed to the substrate thickness. For example, it is desirable to set it as 50%-70%.

  Even when the ratio of the area where cracks (internally processed areas) are formed to the substrate thickness is the same, the cracks are relatively close or continuous in the substrate when the cracks are formed at equal intervals. In some cases, the region is formed so as to have a region where a crack is relatively separated. Here, when the cracks are formed at equal intervals, there is an advantage that unintentional stress concentration is unlikely to occur in the substrate during substrate transportation, and inadvertent cracks do not occur. FIG. 9A shows a case where the cracks (internally processed regions) 14a to 14c are formed at equal intervals.

  On the other hand, when the substrate is formed so as to have a region where cracks (internally processed regions) are relatively close or continuous and a region where the cracks are relatively separated from each other, as shown in FIG. A region where the crack 14b and the crack 14c are relatively close to each other or continuous can be formed in the vicinity of the surface on the incident side of the laser beam LB. Conversely, a region where the crack 14a and the crack 14b are relatively close to each other or continuous may be formed near the surface opposite to the incident side of the laser beam LB. In particular, as shown in FIG. 9B, by forming a region in which cracks 14b and 14c formed in the vicinity of the surface processing mark 13 are relatively close or continuous, the surface processing mark 13 is formed in the cleaving step. If an external force is applied so as to concentrate the stress at the starting point, the element E can be easily cleaved and separated from the silicon substrate 10.

  Further, as shown in FIG. 9C, the cracks 14a to 14c are densely formed along the irradiation direction of the laser beam LB (the thickness direction of the substrate), and the cracks are close to or connected to each other inside the substrate. It is also possible to form only. When the ratio of the area where the crack is formed to the substrate thickness is the same, when the crack as shown in FIG. 9C is formed, when the crack is formed at equal intervals (FIG. 9A )), Or when the substrate is formed so as to have a region where the cracks are relatively close or continuous and a region where the cracks are relatively separated (FIG. 9B), the substrate can be cleaved with a smaller external force. It is.

[Cleaving process]
The silicon substrate 10 on which the surface processing marks 13 and the plurality of internal cracks (internal processing regions) 14a, 14b, 14c are formed for each breaking line C is connected to at least the surface processing marks 13 and the internal cracks 12c immediately below the surface. Therefore, the individual elements E of the silicon substrate 10 after laser processing are not cleaved or separated. The procedure for cleaving the silicon substrate 10 in this state into the element chip E is performed as follows.

  As shown in FIG. 11, the front surface 11 (dicing tape) of the silicon substrate 10 remains mounted on the dicing tape T while the silicon substrate 10 after the surface processing marks 13 and the internal cracks 14 (14a, 14b, 14c) are formed. It is placed on a rubber sheet 60 having elasticity such as silicone rubber or fluororubber of the cleaving device so that the surface of the silicon substrate on which T is stuck is up. In addition, in order to avoid that the back side surface 12 of the substrate of the silicon substrate 10 contacts the rubber sheet 60 and the dirt is attached to the back side surface 12, the back side surface 12 of the silicon substrate 10 after the formation of the internal crack is back grounded or the like. A commercially available protective tape used in the above may be attached.

The cleaving is performed by pressing the silicon substrate 10 through the dicing tape T with a stainless roller 61. First, the silicon substrate 10 is placed on the rubber sheet 60 so that one of the breaking lines C of the silicon substrate 10, preferably the first breaking direction, is substantially parallel to the roller axis. When the silicon substrate 10 is pressed while rolling the roller 61, the rubber sheet 60 immediately below the roller 61 is deformed so as to sink. In the silicon substrate 10, stress in the extending direction acts on the rubber sheet 60 side, that is, the surface side. This stress weakest point of the back surface 12 of the substrate, i.e., acts to widen the surface machining mark 13 on the cutting lines C _1.

As a result, a crack is generated starting from the surface processing mark 13, and the crack is connected from the internal crack 14 c to the internal crack 14 a to reach the front surface 11, and the silicon substrate 10 is cut along the cutting line C _1. Is done. Although the progress of the crack occurs along the crystal orientation of the silicon substrate 10, since the cleaving is performed by the connection with the surface processing trace 13, the crack does not greatly deviate from the cleaving line C ₁ on the back surface 12. As the roller 61 advances, the silicon substrate 10 is sequentially cut along the breaking line C1 in the _first breaking direction. The roller 61 is advanced from the end of the silicon substrate 10 toward the other end, or the vicinity of the center of the silicon substrate 10 is used as the starting point for pressing the roller 61 toward the end of the silicon substrate 10. Any may be sufficient.

Next, the silicon substrate 10 is rotated by 90 ° so that the breaking line C2 in the _second breaking direction and the axis of the roller 61 are substantially parallel. Similarly to the first cleaving direction, the silicon substrate 10 is pressed by the roller 61 to generate a crack starting from the surface processing mark 13 in the second cleaving direction and reach the front surface 11.

  Through the above steps, the silicon substrate 10 is separated into individual element chips E.

  The cleaving step shown in FIG. 11 applies stress on the surface of the silicon substrate due to the deformation of the rubber sheet by the hard roller. However, the silicon substrate by the roller is used so that the logic element and the nozzle layer are not destroyed. It is necessary to select the compression load, rubber sheet thickness, and rubber hardness. In addition, it is also necessary to select an appropriate dicing tape and surface protective tape material and thickness.

  Further, when the proportion of the length of the internal crack 14 formed with respect to the thickness of the substrate is large, for example, 75% or more, a tensile stress is applied in the vicinity of the breaking line C, and along the breaking line C. There is also a method of separating the elements.

  In order to give a tensile stress in the vicinity of the breaking line C, it is possible to use means for expanding the sheet on which the silicon wafer 10 is bonded. For example, it can be expanded by using a commercially available wafer expander. In general, various wafer mount sheets have means for reducing the adhesive force in order to facilitate the pick-up operation of the element. For example, a sheet having an ultraviolet curable adhesive layer can be reduced in adhesive strength by irradiation with ultraviolet rays. This means to reduce the adhesive force is implemented after the element is reliably separated, so that when the sheet is expanded, the part of the substrate with the unseparated part will not be separated from the sheet. The number of places can be reduced. In addition, depending on the shape of the element, the tensile stress applied to the long side of the element can be compared with the stress applied to the short side of the element to increase the number of unseparated portions of the element in the cleaving process. As an example of a technique for increasing the stress applied to the long side of the element as compared with the stress applied to the short side of the element, a dicing frame is fixed with a component 62 as shown in FIG. By moving T relative to the dicing frame, the sheet is radially expanded to give a predetermined tension to the sheet, and then the side surface of the component 64 having a sufficiently large diameter with respect to the width of the silicon substrate is placed on the element. It is possible by pressing so that it is parallel to the long side direction.

[Repair process]
In the cleaving step, the surface processing trace 13 and the crack caused by the internal crack 14 are connected by a new crack, and the crack also reaches the back surface side, so that the silicon substrate 10 is separated into each element chip.

  However, if there is no accidental complete separation, re-cleaving is necessary. As a re-cleaving method, for example, only the element E that has not been cleaved using the mechanism shown in FIG. 13 is cleaved completely by applying stress individually.

[Pickup process]
The logic element portion, which is the element E separated in the cleaving process and the repair process, is carried out by the suction collet 65 and the pickup pin 66 as shown in FIG. At this time, picking up with the expander or the like widening the gap between the elements can make the picking work easier. In addition, it is effective to improve the operational reliability of the element chip E by sucking and removing fine dust generated during pickup.

  The region where the internal crack 14 is formed is 50% to 70% with respect to the cross section of the substrate where the crack is formed, for example, when the thickness of the substrate is large or the number of times of laser irradiation is limited due to thermal influence on the member. In the case where only about% can be processed, it is effective for cleaving the substrate 10 to form the surface processing trace 13 on the front side surface 11 provided with the logic circuit 1 or the like. In particular, since the space between the first structures 1F is narrower than the space between the second structures 2F, the error in the position of the crack from the inside reaching the front surface 11 of the substrate is more accurate than in the case of the back surface. There is a need. Therefore, it is effective to separate the substrates in the following steps.

  As shown in FIG. 14, the second structure side (back side surface) tape mounting step in step 1, the wafer correction step in step 2, the surface linear processing step in step 3 (first structure side (front side surface) processing step), Step 4 tape peeling process, Step 5 first structure side (front surface) tape mounting process, Step 6 internal crack forming process, Step 7 cleaving process, Step 8 repair process, Step 6 picking process 7 processes Consists of. The description will focus on the changes from the first embodiment.

  First, an adhesive dicing tape T to which a dicing frame M is attached is attached to the back surface 12 provided with the second structure 2F of the silicon substrate 10, and the dicing tape T having an ultraviolet curing adhesive layer. The silicon substrate 10 is sucked by the suction stage D from the side, so that the silicon substrate 10 is flattened and the deformation is corrected.

  Then, marking the front surface 11 of the substrate with a scriber using a tool 40 such as a cemented carbide blade or a diamond blade along the breaking line C between the first structure 1F and the first structure 1F. Surface processing marks 13 are formed on the surface.

  Thereafter, the dicing tape T is irradiated with ultraviolet rays to reduce the adhesive strength. When the adhesive force is reduced, the silicon substrate 10 is peeled from the dicing tape T.

  The front-side surface 11 provided with the peeled first structure of the silicon substrate 10 is attached to an adhesive dicing tape T to which a dicing frame M is attached. Thereafter, the laser beam LB is irradiated between the second structure 2F and the second structure 2F to form the internal crack 14.

  In the cleaving step, unlike the first embodiment, the surface processing trace 13 is formed on the front side surface 11, so that the back side surface 12 is placed so that the front side surface 11 contacts the rubber sheet 60. At this time, although it presses from the back surface 12 with the roller 61, it is preferable to affix the protective tape for protecting the 2nd structure 2F provided in the back surface 12.

  The cleaving is performed by pressing the silicon substrate 10 with the stainless roller 61 through the dicing tape T, and then the elements E are cleaved and separated from the substrate 10 through a repair process and a pickup process.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a silicon substrate according to an embodiment, in which (a) is a perspective view thereof, (b) is a partially enlarged perspective view showing an enlarged portion of (a), and (c) is a sectional view of (b). It is a fragmentary sectional view shown. It is a schematic diagram explaining an Example. It is a schematic diagram of the board | substrate cross section in which the internal process area | region was formed. It is a schematic diagram of the board | substrate cross section which shows the mode of internal processing area | region formation. It is a flowchart which shows the process which cleaves a silicon substrate. It is a figure explaining a tape mounting process. It is a figure explaining the planarization process of a silicon substrate. It is explanatory drawing which forms a surface processing trace. (A) is a schematic cross-sectional view in which cracks are formed at equal intervals, and (b) is a schematic cross-sectional view having a region in which cracks are formed relatively close or continuous and a region in which cracks are formed apart from each other. c) is a schematic cross-sectional view having only a region in which cracks are relatively close or continuous. It is a schematic diagram which shows the processing apparatus which irradiates a laser beam. (A) is a figure explaining the cleaving process with a roller, (b) is a schematic diagram which shows the cross section of the silicon substrate cleaved with a roller. It is a figure explaining isolation | separation of the element by expansion. It is a figure explaining a repair process and a pick-up process. It is a flowchart which shows the other process which cleaves a silicon substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Logic circuit 1F 1st structure 2 Flow path formation member 3 Discharge port 4 Bump 5 Liquid supply port 6 Through-electrode 11 Front side surface 12 Back side surface 13 Surface processing trace 14, 14a, 14b, 14c Internal crack (internal processing area)
1F 1st structure 2F 2nd structure

Claims (10)

With respect to the member to be cut provided with a plurality of structures on the front and back surfaces, the laser beam is incident from one surface and focused on a condensing point having a predetermined depth inside the member to be cut. A laser cleaving method for cleaving the cleaved member along a cleaving line so as to form an internal processing region and the surface of the cleaved member is separated into a plurality of regions,
The interval between the structures provided on the one surface is wider than the interval between the structures provided on the other surface, so that the structures do not enter the luminous flux of the incident laser light. A laser cleaving method, wherein the cleaved member is irradiated with a laser beam.   The height of the structure end on the laser beam side irradiated toward the inside of the member to be cut is h, the angle between the laser beam and the perpendicular of the surface outside the member to be cut is θ1, and the laser beam is In the case where θ2 is an angle formed with the normal of the surface inside the cleaving member, and L is a distance from the laser light irradiation surface on the surface of the cleaved member to the laser focusing point inside, the cleaving line and the structure 2. The laser cleaving method according to claim 1, wherein a> h × tan θ1 + L × tan θ2, where a is a distance between.   The thickness of the member to be cut at the cleaving position is t, the distance between the condensing point closest to the laser beam emission side surface and the emission side surface is r, and the distance from the laser beam incident surface to the laser focusing point is L. In this case, if the distance between the breaking line and the structure is a, the laser beam is condensed inside the member to be cut so that L <tr. 2. The laser cleaving method according to 2.   4. A recess for concentrating stress when cleaving the cleaved member is formed on the surface of the cleaved member before forming the internal processing region inside the cleaved member. The laser cleaving method described in 1.   5. The concave member for concentrating stress when cleaving the cleaved member after forming an internal processing region inside the cleaved member is formed on the surface of the cleaved member. The laser cleaving method according to any one of the above.   6. The laser cleaving method according to claim 2, wherein a crack is formed by applying an external force to the member to be cut to reach the internal processing region and the recess on the surface of the member to be cut. A first structure provided on the front surface and a plurality of second structures provided on the back surface opposite to the front surface, and between the first structure and the second structure. A member to be cleaved along a cleaving line connecting
The cleaved member is a member cleaved by condensing laser light from the surface to the inside, and the end of the second structure on the laser beam side irradiated toward the inside of the cleaved member The height of the portion is h, the angle that the laser beam is perpendicular to the back surface outside the cleaved member is θ1, the angle that the laser beam is perpendicular to the back surface inside the cleaved member is θ2, and the back surface When the distance from the laser light irradiation surface to the internal laser condensing point is L, a> h × tan θ1 + L × tan θ2 where a is the distance between the breaking line and the second structure. A member to be cut.   The member to be cut according to claim 7, wherein an interval between the second structures is wider than an interval between the first structures.   The cleaved member according to claim 7 or 8, wherein a recess for concentrating stress when the cleaved member is cleaved is formed between the first structures on the surface of the cleaved member. Element.   The cleaved member according to claim 7 or 8, wherein a concave portion for concentrating stress when the cleaved member is cleaved is formed between the second structures on the surface of the cleaved member. Element.

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