JP6012185B2 - Manufacturing method of semiconductor device - Google Patents

Manufacturing method of semiconductor device Download PDF

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JP6012185B2
JP6012185B2 JP2012016802A JP2012016802A JP6012185B2 JP 6012185 B2 JP6012185 B2 JP 6012185B2 JP 2012016802 A JP2012016802 A JP 2012016802A JP 2012016802 A JP2012016802 A JP 2012016802A JP 6012185 B2 JP6012185 B2 JP 6012185B2
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semiconductor substrate
region
cutting
semiconductor
laser
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JP2013157451A (en
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剛志 坂本
剛志 坂本
いく 佐野
いく 佐野
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浜松ホトニクス株式会社
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  The present invention relates to a method for manufacturing a semiconductor device.
  Conventionally, in a semiconductor device manufacturing process, a semiconductor substrate is irradiated with laser light to modify the inside of the semiconductor substrate, thereby forming a gettering region inside the semiconductor substrate for capturing impurities such as heavy metals. Is known (see, for example, Patent Documents 1 to 3).
JP 2009-272440 A JP 2003-264194 A JP 58-44726 A
  In such a semiconductor device manufacturing process, a gettering region is formed in a semiconductor substrate, and further, the semiconductor substrate is irradiated with laser light to modify the inside of the semiconductor substrate, thereby cutting the semiconductor substrate. It is conceivable to form a cutting start region that is a starting point of cutting in the semiconductor substrate. In this case, the gettering region and the cutting start region are formed in the semiconductor substrate, and the positional relationship in which these two regions are formed is important for reliably cutting the semiconductor substrate.
  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device that can more reliably cut a semiconductor substrate.
In the method for manufacturing a semiconductor device of the present invention, a semiconductor substrate having a front surface for forming a plurality of functional elements and a back surface opposite to the front surface is irradiated with a first laser beam to modify the inside of the semiconductor substrate. Thus, the first step of forming a gettering region for trapping impurities inside the semiconductor substrate and the position after the first step between adjacent functional elements are set. By irradiating the semiconductor substrate with the second laser beam along the planned cutting line to modify the inside of the semiconductor substrate, a cutting starting region for generating a crack in the thickness direction of the semiconductor substrate is formed. After the second step of forming the inner surface of the gettering region and the second step, at least the semiconductor substrate is cut for each functional element along the planned cutting line, And a third step of obtaining a plurality of semiconductor devices including a modified region which serves as a gettering region formed by modifying the interior of the semiconductor substrate by irradiating a first laser beam is a semiconductor The modification spot in the modification region in the thickness direction of the substrate is formed to have a modification spot width of 1 to 10 μm, and is formed by modifying the inside of the semiconductor substrate by irradiating a second laser beam. The modified spot distance in the case of forming the modified region functioning as the cutting start region satisfies 3.75 to 7.5 μm, and the modified spot distance in the case of forming the modified region functioning as the gettering region is 5 When the modified region that satisfies ˜20 μm and functions as the gettering region is formed, the modified spot distance forms the modified region that functions as the cutting start region. Longer than reforming spot distance in the case of.
  In this semiconductor device manufacturing method, after the gettering region is formed, the cutting start region is formed at a position on the surface side of the gettering region inside the semiconductor substrate. Thereby, in addition to the crack generated from the cutting start region, the gettering region can also be used as the starting point of cutting, and the semiconductor substrate can be cut more reliably. In addition, when the gettering region is formed, higher accuracy is required for laser light adjustment and the like than when the cutting start region is formed. Therefore, by forming the gettering region first, the gettering region can be satisfactorily formed without being influenced by the cutting start region. In addition, when the semiconductor substrate is cut starting from the cutting start region, the cutting start region remains on the outer surface of the semiconductor device. Therefore, the cutting start region remaining on the outer surface of the semiconductor device also exhibits the same function as the gettering region, and can capture impurities more reliably.
  In the first step, it is preferable that a gettering region is formed at a position on the back surface side of the semiconductor substrate with respect to the thickness of the semiconductor substrate when formed as a semiconductor device. According to this, a space for forming the cutting start region can be secured between the gettering region and the functional element, and the cutting starting region can be easily formed.
  In the third step, it is preferable to polish the back surface of the semiconductor substrate so that the semiconductor substrate has a predetermined thickness. According to this, even if the polished surface reaches a crack generated from the cutting start region, the cut surfaces of the semiconductor substrates cut by the crack are in close contact with each other. The semiconductor substrate can be thinned while suppressing the generation.
  In the second step, it is preferable to irradiate the semiconductor substrate with the second laser beam using the back surface of the semiconductor substrate as the laser beam incident surface. According to this, it is possible to suppress the thermal effect or the like due to the irradiation of the laser beam on the functional element formed on the surface of the semiconductor substrate.
  In the second step, it is preferable to irradiate the semiconductor substrate with the second laser light so that the crack generated from the cutting start region reaches at least the surface of the semiconductor substrate. According to this, the cutting accuracy of the functional element side portion of the semiconductor substrate can be further improved.
  In the first step, it is preferable that the gettering region is formed inside the semiconductor substrate so as not to intersect with the planned cutting line. According to this, it is possible to accurately cut the semiconductor substrate along the planned cutting line while suppressing the influence of the gettering region on the semiconductor substrate along the planned cutting line.
  According to the present invention, the semiconductor substrate can be cut more reliably.
It is a schematic block diagram of the laser processing apparatus used for formation of a modification area | region. It is a top view of the process target object used as the object of formation of a cutting | disconnection start area | region. It is sectional drawing along the III-III line of the workpiece of FIG. It is a top view of the processing target after laser processing. It is sectional drawing along the VV line of the workpiece of FIG. It is sectional drawing along the VI-VI line of the processing target object of FIG. It is sectional drawing of the semiconductor substrate in which formation of a gettering area | region is implemented. It is sectional drawing of the semiconductor substrate in which the gettering area | region was formed, and a semiconductor device. It is sectional drawing of the semiconductor substrate in which the gettering area | region was formed, and a semiconductor device. It is a top view which shows the formation aspect of a gettering area | region. It is the top view and sectional drawing of a semiconductor substrate with which the manufacturing method of the semiconductor device of one Embodiment of this invention is enforced. It is the top view and sectional drawing of a semiconductor substrate with which the manufacturing method of the semiconductor device of one Embodiment of this invention is enforced. It is the top view and sectional drawing of a semiconductor substrate with which the manufacturing method of the semiconductor device of one Embodiment of this invention is enforced. It is the top view and sectional drawing of a semiconductor substrate with which the manufacturing method of the semiconductor device of one Embodiment of this invention is enforced. It is the top view and sectional drawing of a semiconductor substrate with which the manufacturing method of the semiconductor device of one Embodiment of this invention is enforced. It is a top view of the semiconductor substrate with which the manufacturing method of the semiconductor device of other embodiment of this invention is implemented. It is a top view of the semiconductor substrate with which the manufacturing method of the semiconductor device of other embodiment of this invention is implemented. It is a top view of the semiconductor substrate with which the manufacturing method of the semiconductor device of other embodiment of this invention is implemented. It is a top view of the semiconductor substrate with which the manufacturing method of the semiconductor device of other embodiment of this invention is implemented.
  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.
  In the semiconductor device manufacturing method of the present embodiment, the semiconductor substrate is irradiated with laser light to modify the inside of the semiconductor substrate, thereby generating a crack in the thickness direction of the semiconductor substrate along the planned cutting line. In some cases, a cutting starting region (that is, a modified region functioning as a cutting starting region) is formed inside the semiconductor substrate. Therefore, the formation of the cutting start region for a plate-like workpiece is not limited to a semiconductor substrate, and will be described with reference to FIGS.
  As shown in FIG. 1, a laser processing apparatus 100 includes a laser light source 101 that oscillates a laser beam L, a dichroic mirror 103 that is arranged so as to change the direction of the optical axis (optical path) of the laser beam L, and A condensing lens 105 for condensing the laser light L. Further, the laser processing apparatus 100 includes a support base 107 for supporting the workpiece 1 irradiated with the laser light L condensed by the condensing lens 105, and a stage 111 for moving the support base 107. And a laser light source control unit 102 for controlling the laser light source 101 in order to adjust the output, pulse width, etc. of the laser light L, and a stage control unit 115 for controlling the drive of the stage 111.
  In this laser processing apparatus 100, the laser light L emitted from the laser light source 101 has its optical axis changed by 90 ° by the dichroic mirror 103, and the inside of the processing object 1 placed on the support base 107. The light is condensed by the condensing lens 105. At the same time, the stage 111 is moved, and the workpiece 1 is moved relative to the laser beam L along the planned cutting line 5. As a result, a modified region along the planned cutting line 5 is formed on the workpiece 1.
  As the workpiece 1, plate-like members (for example, substrates, wafers, etc.) made of various materials (for example, glass, semiconductor material, piezoelectric material, etc.) are used. As shown in FIG. 2, a scheduled cutting line 5 for cutting the workpiece 1 is set in the workpiece 1. The planned cutting line 5 is a virtual line extending linearly. When forming a modified region inside the workpiece 1, as shown in FIG. 3, the laser beam L is projected along the planned cutting line 5 in a state where the focused point P is aligned with the inside of the workpiece 1. It moves relatively (that is, in the direction of arrow A in FIG. 2). As a result, as shown in FIGS. 4 to 6, the modified region 7 that functions as the cutting start region 8 is formed inside the workpiece 1 along the planned cutting line 5.
  In addition, the condensing point P is a location where the laser light L is condensed. Further, the planned cutting line 5 is not limited to a straight line, but may be a curved line, or may be a line actually drawn on the surface 3 of the workpiece 1 without being limited to a virtual line. In addition, the modified region 7 may be formed continuously or intermittently. Further, the modified region 7 may be in the form of a line or a dot. In short, the modified region 7 only needs to be formed at least inside the workpiece 1. In addition, a crack may be formed starting from the modified region 7, and the crack and modified region 7 may be exposed on the outer surface (front surface, back surface, or outer peripheral surface) of the workpiece 1.
  Incidentally, the laser light L here passes through the workpiece 1 and is particularly absorbed near the condensing point inside the workpiece 1, thereby forming the modified region 7 in the workpiece 1. (Ie, internal absorption laser processing). Therefore, since the laser beam L is hardly absorbed on the surface 3 of the workpiece 1, the surface 3 of the workpiece 1 is not melted. In general, when a removed portion such as a hole or a groove is formed by being melted and removed from the front surface 3 (surface absorption laser processing), the processing region gradually proceeds from the front surface 3 side to the back surface side.
  By the way, the modified region refers to a region in which density, refractive index, mechanical strength, and other physical characteristics are different from the surroundings. Examples of the modified region include a melt treatment region, a crack region, a dielectric breakdown region, a refractive index change region, and the like, and there is a region where these are mixed. Furthermore, as the modified region, there are a region in which the density of the modified region in the material to be processed is changed as compared with the density of the non-modified region, and a region in which lattice defects are formed (collectively these are high-density regions). Also known as the metastatic region).
In addition, the area where the density of the melt treatment area, the refractive index change area, the modified area has changed compared to the density of the non-modified area, and the area where lattice defects are formed are further included in these areas and the modified areas. In some cases, cracks (cracks, microcracks, etc.) are included in the interface between the non-modified region and the non-modified region. The included crack may be formed over the entire surface of the modified region, or may be formed in only a part or a plurality of parts. Examples of the processing object 1 include a substrate or wafer made of silicon, glass, LiTaO 3 or sapphire (Al 2 O 3 ), or a material including such a substrate or wafer.
  The modified region 7 is a region in which a plurality of modified spots (processing marks) are formed along the planned cutting line 5. The modified spot is a modified portion formed by one pulse shot of pulsed laser light (that is, one pulse of laser irradiation: laser shot). Examples of the modified spot include a crack spot, a melting treatment spot, a refractive index change spot, or a mixture of at least one of these. Considering the required cutting accuracy, required flatness of the cut surface, thickness of the workpiece, type, crystal orientation, etc., the size of the modified spot and the length of the crack to be generated are appropriately determined. It is preferable to control.
  In the semiconductor device manufacturing method of the present embodiment, the semiconductor substrate is irradiated with laser light to modify the inside of the semiconductor substrate, thereby obtaining a gettering region (that is, functioning as a gettering region). A modified region to be formed) is formed inside the semiconductor substrate. Therefore, formation of the gettering region for the semiconductor substrate will be described with reference to FIGS.
  As shown in FIG. 7, a semiconductor substrate 2 such as a silicon wafer is prepared. The semiconductor substrate 2 has a front surface 2a for forming a plurality of functional elements 25 and a back surface 2b opposite to the front surface 2a. The functional element 25 means a light receiving element such as a photodiode, a light emitting element such as a laser diode, or a circuit element formed as a circuit.
  Subsequently, the surface 2a of the semiconductor substrate 2 is used as the laser beam incident surface, and the semiconductor substrate 2 is irradiated with the laser beam L with the focusing point P aligned with the interior of the semiconductor substrate 2, thereby forming the modified region 17 functioning as the gettering region 18 in the semiconductor. It is formed inside the substrate 2. More specifically, in the thickness direction of the semiconductor substrate 2, the semiconductor substrate is opposed to the formation region 15 a of each functional element 25 (region in which each functional element 25 is formed on the surface 2 a of the semiconductor substrate 2). A gettering region 18 is formed inside 2. In forming the gettering region 18, the back surface 2b of the semiconductor substrate 2 may be a laser light incident surface. Further, the gettering region 18 may be formed continuously or intermittently as long as it faces at least the respective formation regions 25a.
  Subsequently, a plurality of functional elements 25 are formed on the surface 2a of the semiconductor substrate 2, and then the semiconductor substrate 2 is cut for each functional element 25 to obtain a plurality of semiconductor devices. The gettering region 18 may be formed after the functional element 25 is formed, or may be formed both before and after the functional element 25 is formed.
  The gettering region 18 formed as described above exhibits a gettering effect for collecting and capturing impurities such as heavy metals inside the semiconductor substrate 2. Thereby, it is possible to suppress an adverse effect on the functional element 25 due to impurities such as heavy metals. Here, the modified region 17 functioning as the gettering region 18 is a region in which density, refractive index, mechanical strength, and other physical characteristics are different from the surroundings, and is, for example, a melt processing region.
  When it is necessary to reduce the thickness of the semiconductor substrate 2 to a predetermined thickness, the semiconductor substrate 2 has a predetermined thickness after the functional element 25 is formed and before the semiconductor substrate 2 is cut. The back surface 2b of the substrate 2 is polished. At this time, as shown in FIG. 8A, if the gettering region 18 is formed on the surface 2a side of the semiconductor substrate 2 with respect to the polishing end planned surface 16, as shown in FIG. The gettering region 18 remains in the semiconductor device 20. On the other hand, as shown in FIG. 9A, if the gettering region 18 is formed on the back surface 2b side of the semiconductor substrate 2 with respect to the polishing end planned surface 16, the semiconductor as shown in FIG. The gettering region 18 does not remain in the device 20. Here, the polishing is a thinning process comprising one or a combination of mechanical polishing (cutting, grinding, dry polishing, etc.), chemical polishing (chemical etching, etc.), chemical mechanical polishing (CMP), and the like.
  Incidentally, when the gettering region 18 is formed, the above-described laser processing apparatus 100 can be used. However, the modified region 7 that functions as the cutting start region 8 needs to be easily cracked in the thickness direction of the semiconductor substrate 2, whereas the modified region 17 that functions as the gettering region 18 It is necessary that such cracks are difficult to occur. Therefore, it is necessary to make the irradiation condition of the laser beam L different between the case where the modified region 7 functioning as the cutting start region 8 is formed and the case where the modified region 17 functioning as the gettering region 18 is formed.
  For example, when the modified region 7 that functions as the cutting start region 8 is formed, the output of the laser light L is about 10 to 40 μJ, whereas when the modified region 17 that functions as the gettering region 18 is formed. The output of the laser beam L is about 0.2 to 3 μJ. As a result, in the modified region 17 that functions as the gettering region 18, the width of the modified spot in the thickness direction of the semiconductor substrate 2 is 1 to 10 μm (more preferably 4 to 6 μm). The modified region 17 composed of the modified spot having such a width hardly causes a crack in the thickness direction of the semiconductor substrate 2 and sufficiently exhibits the gettering effect. As described above, the output of the laser beam L when forming the modified region 17 that functions as the gettering region 18 is lower than the output of the laser beam L when forming the modified region 7 that functions as the cutting start region 8. It is preferable.
  Further, for example, in the case of forming the modified region 7 that functions as the cutting starting region 8, the modified spot distance (distance between the nearest modified spots) is about 3.75 to 7.5 μm, In the case where the modified region 17 that functions as the gettering region 18 is formed, the modified spot distance is about 5 to 20 μm. The modified region 17 composed of the modified spots having such modified spot distances makes it difficult to extend cracks between the nearest modified spots and sufficiently exhibits the gettering effect. As described above, the modified spot distance when the modified region 17 that functions as the gettering region 18 is formed is longer than the modified spot distance when the modified region 7 that functions as the cutting start region 8 is formed. preferable.
  It should be noted that the adjustment of the modified spot distance when the modified region 17 functioning as the gettering region 18 is formed can be performed as follows. For example, as shown in FIG. 10A, a plurality of modified spots along the moving direction of the laser light L (the direction in which the condensing point P of the laser light L is moved relative to the semiconductor substrate 2). When the 17a is arranged in a line, the pulse pitch of the laser beam L (relative movement of the laser beam L) is set so that the modified spot distance d is difficult to extend the crack and can sufficiently exhibit the gettering effect. Speed / Repetition frequency of laser beam L) may be set.
  Further, as shown in FIG. 10B, one laser beam L is branched along the direction intersecting the moving direction of the laser beam L and condensed at a plurality of locations, and the modified spot 17a is formed at each location. In the case of forming, one laser beam L may be branched and condensed at a plurality of locations so as to have the above-described modified spot distance d. Further, as shown in FIG. 10C, when the plurality of modified spots 17a are arranged in a plurality of rows along the moving direction of the laser light L, the modified spot distance d is set as described above. What is necessary is just to set the distance between the modification | reformation spots 17a over an adjacent row | line | column. In these cases, in the moving direction of the laser light L, the distance between the adjacent modified spots 17a can be increased, so that it is difficult to extend the crack along the direction.
  Next, the manufacturing method of the semiconductor device of one Embodiment of this invention is demonstrated. First, as shown in FIG. 11, the semiconductor substrate 2 is prepared. The semiconductor substrate 2 has a front surface 2a for forming a plurality of functional elements 25 and a back surface 2b opposite to the front surface 2a. The functional elements 25 are arranged on the surface 2 a of the semiconductor substrate 2 so as to be arranged in a matrix along a direction substantially parallel to and substantially perpendicular to an orientation flat (hereinafter referred to as “OF”) 19 of the semiconductor substrate 2. The formation area 25a is set. The semiconductor substrate 2 is a silicon wafer having a diameter of 12 inches and a thickness of 775 μm, for example.
  Subsequently, the gettering region 18 is formed inside the semiconductor substrate 2 using the laser processing apparatus 100 described above as follows. That is, the semiconductor substrate 2 is placed on the support 107 of the laser processing apparatus 100 so that the surface 2a of the semiconductor substrate 2 becomes a laser beam incident surface, and the formation lines 15 for forming the gettering region 18 are latticed. Set the shape. Here, the formation line 15 is formed along each of the columns of the formation regions 25a arranged in a direction substantially parallel to the OF 19 and each of the columns of the formation regions 25a arranged in a direction substantially perpendicular to the OF 19. It passes through the center of the formation region 25a.
  Then, the surface 2a of the semiconductor substrate 2 is used as a laser beam incident surface, and the light collecting point P1 is aligned with the inside of the semiconductor substrate 2 (here, the surface 2a side of the semiconductor substrate 2 with respect to the surface 16 to be polished), and gettering is performed. The semiconductor substrate 2 is irradiated with a laser beam (first laser beam) L1 under irradiation conditions in the case of forming the modified region 17 that functions as the region 18. At this time, the condensing point P1 of the laser beam L1 is moved along each planned formation line 15 while the optical axis of the laser beam L1 is positioned on each planned formation line 15. However, when the optical axis of the laser light L1 passes through the portion where the planned formation line 15 and the planned cutting line 5 intersect, the irradiation of the laser light L1 is turned off, and each formation region 25a is set to the optical axis of the laser light L1. When the laser beam passes, the laser beam L1 is turned on. Note that the scheduled cutting lines 5 are set in a lattice shape in a subsequent process so as to pass between the adjacent functional elements 25 (that is, between the adjacent formation regions 25a).
  The gettering region 18 is located on the back surface 2b side with respect to the center position T of the distance from the front surface a of the semiconductor substrate 2 to the planned polishing end surface 16, that is, on the semiconductor substrate 2 when formed as the semiconductor device 20. In the inside, the semiconductor substrate 2 is formed at a position closer to the back surface 2b side than the center position T of the thickness.
  As described above, by irradiating the semiconductor substrate 2 with the laser beam L1 and modifying the inside of the semiconductor substrate 2, when viewed from the thickness direction of the semiconductor substrate 2, it does not intersect with the planned cutting line 5. A gettering region 18 is formed inside the semiconductor substrate 2 (first step). Here, since the condensing point P1 is aligned with the surface 2a side of the semiconductor substrate 2 with respect to the polishing end surface 16, the gettering region 18 is also formed on the surface 2a side of the semiconductor substrate 2 with respect to the polishing end surface 16. Is done. In order to move the condensing point P1 of the laser light L1 relative to the semiconductor substrate 2, the support 107 may be moved, or the laser light source 101 side (the laser light source 101, the dichroic mirror 103, and the light collecting point). The optical lens 105 or the like) may be moved, or both the support base 107 and the laser light source 101 side may be moved.
  Subsequently, as shown in FIG. 12, a plurality of functional elements 25 are formed on the surface 2 a of the semiconductor substrate 2. At this time, the gettering region 18 formed in a cross shape along the formation line 15 is opposed to the formation region 25 a of the functional element 25 in the thickness direction of the semiconductor substrate 2.
  Subsequently, as shown in FIG. 13, the cutting start region 8 is formed inside the semiconductor substrate 2 using the laser processing apparatus 100 described above as follows. That is, after the protective film 22 is attached to the front surface 2a of the semiconductor substrate 2 so as to cover all the functional elements 25, the support base 107 of the laser processing apparatus 100 so that the back surface 2b of the semiconductor substrate 2 becomes the laser light incident surface. The semiconductor substrate 2 is placed thereon, and the cutting lines 5 are set in a lattice shape so as to pass between the adjacent functional elements 25 (that is, between the adjacent formation regions 25a).
  Then, the back surface 2b of the semiconductor substrate 2 is used as a laser light incident surface, and the light is condensed inside the semiconductor substrate 2 (here, on the surface 2a side of the gettering region 18, that is, between the gettering region 18 and the functional element 25). The semiconductor substrate 2 is irradiated with a laser beam (second laser beam) L2 under the irradiation condition of the laser beam when the modified region 7 that functions as the cutting start region 8 is formed by combining the points P2. At this time, the condensing point P2 of the laser beam L2 is moved along each planned cutting line 5 while the optical axis of the laser beam L2 is positioned on each planned cutting line 5.
  As described above, the semiconductor substrate 2 is irradiated with the laser beam L2 to modify the inside of the semiconductor substrate 2, thereby forming the cutting start region 8 in the semiconductor substrate 2 along the planned cutting line 5 ( Second step). Then, by irradiating the semiconductor substrate 2 with the laser beam L2, the crack 21 generated from the cutting start region 8 is caused to reach the surface 2a of the semiconductor substrate 2. In order to move the condensing point P2 of the laser beam L2 relative to the semiconductor substrate 2, the support 107 may be moved, the laser light source 101 side may be moved, or You may move both the support stand 107 and the laser light source 101 side.
  Subsequently, as shown in FIG. 14, the semiconductor substrate 2 to which the protective film 22 is attached is placed on the support base 207 of the polishing apparatus, and the back surface 2 b of the semiconductor substrate 2 reaches the polishing scheduled end surface 16. The back surface 2b of the semiconductor substrate 2 is polished. As a result, the polishing surface reaches the crack 21 generated from the cutting start region 8 and extending toward the back surface 2 b of the semiconductor substrate 2, and the semiconductor substrate 2 is cut along the planned cutting line 5. The thickness of the semiconductor substrate 2 after polishing is, for example, 75 μm.
  Subsequently, as shown in FIG. 15, an expanded film 23 is attached to the back surface 2 b of the semiconductor substrate 2, and then the protective film 22 is removed from the front surface 2 a of the semiconductor substrate 2. Then, in order to pick up a plurality of semiconductor devices 20 obtained by cutting the semiconductor substrate 2, the expanded film 23 is expanded radially outward to separate the plurality of semiconductor devices 20 from each other. As described above, the back surface 2b of the semiconductor substrate 2 is polished so that the cutting start region 8 does not remain, and the semiconductor substrate 2 is cut for each functional element 25 along the planned cutting line 5, and one functional element 25 is formed. A plurality of semiconductor devices 20 are obtained (third step).
  As described above, in the method for manufacturing the semiconductor device 20, after the gettering region 18 is formed, the cutting start region 8 is formed at a position closer to the surface 2 a than the gettering region 18 inside the semiconductor substrate 2. Thereby, in addition to the crack 21 generated from the cutting start region 8 as a starting point, the gettering region 18 can also be used as a starting point of cutting, and the semiconductor substrate 2 can be cut more reliably. By using the gettering region 18 as a starting point for cutting in addition to the crack 21 generated from the starting point region 8 for cutting, even a thick semiconductor substrate 2 can be reliably divided.
  Further, when the gettering region 18 is formed, higher accuracy is required for adjustment of the laser light L1 and the like than when the cutting start region 8 is formed. Therefore, by forming the gettering region 18 first, it is possible to satisfactorily form the gettering region 18 without being affected by the cutting start region 8. When the semiconductor substrate 2 is cut using the cutting start region 8 as a starting point, the cutting starting region 8 remains on the outer surface of the semiconductor device 20. Therefore, the cutting starting region 8 remaining on the outer surface of the semiconductor device 20 also exhibits the same function as the gettering region 18, and impurities can be more reliably captured by the cutting starting region 8.
  Further, the gettering region 18 is formed inside the semiconductor substrate 2 when formed as the semiconductor device 20 at a position closer to the back surface 2b than the center position T of the thickness of the semiconductor substrate 2. It is possible to secure a space for forming the cutting start region 8 between the functional element 25 and the functional element 25, and the cutting starting region 8 can be easily formed.
  Further, the back surface 2b of the semiconductor substrate 2 is polished to the position of the polishing end planned surface 16. Thus, even if the polished surface reaches the crack 21 generated from the cutting start region 8, the cut surfaces of the semiconductor substrate 2 cut by the crack 21 are in close contact with each other. The semiconductor substrate 2 can be thinned while suppressing the occurrence of cracking.
  Further, when forming the cutting start region, the semiconductor substrate 2 is irradiated with the laser beam L2 with the back surface 2b of the semiconductor substrate 2 as the laser beam incident surface. Thereby, it can suppress that the thermal influence etc. by irradiation of the laser beam L2 reach to the functional element 25 formed in the surface 2a of the semiconductor substrate 2.
  Further, when the cutting start region 8 is formed, the semiconductor substrate 2 is irradiated with the laser light L2 so that the crack 21 generated from the cutting start region 8 reaches at least the surface 2a of the semiconductor substrate 2. Thereby, the cutting precision of the part by the side of the functional element 25 in the semiconductor substrate 2 can be improved further.
  Further, the gettering region 18 is formed inside the semiconductor substrate 2 so as not to intersect the planned cutting line 5. Thereby, it is possible to suppress the influence of the gettering region 18 on the portion along the planned cutting line 5 in the semiconductor substrate 2 and to cut the semiconductor substrate 2 along the planned cutting line 5 with high accuracy.
  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, when the semiconductor substrate 2 is cut along the planned cutting line 5, a stacked portion such as an oxide film may be formed on the surface 2 a of the semiconductor substrate 2 so as to extend between the adjacent functional elements 25. In that case, the laminated portion may be cut along with the semiconductor substrate 2 along the cutting line 5.
  In the above embodiment, the semiconductor substrate 2 is not completely cut along the planned cutting line 5 before the back surface 2b of the semiconductor substrate 2 is polished, and the semiconductor substrate 2 is polished after the back surface 2b of the semiconductor substrate 2 is polished. Although the board | substrate 2 was cut | disconnected completely along the cutting planned line 5, it is not limited to this. That is, the polishing of the back surface 2b of the semiconductor substrate 2 and the cutting of the semiconductor substrate 2 along the scheduled cutting line 5 may proceed simultaneously, or the cutting may be performed after the polishing, The polishing may be performed later. Among them, even when the semiconductor substrate 2 was completely cut along the planned cutting line 5 before polishing the back surface 2b of the semiconductor substrate 2, it occurred from the modified region 7 functioning as the cutting start region 8. When the crack 21 is extended and the semiconductor substrate 2 is cut, the cut surfaces of the semiconductor substrate 2 cut by the crack 21 are in close contact with each other. Therefore, the semiconductor substrate 2 can be thinned while suppressing occurrence of chipping and cracking of the semiconductor substrate 2 due to polishing.
  Further, the modified region 17 functioning as the gettering region 18 and the modified region 7 functioning as the cutting start region 8 are not limited to the case where they are formed only due to multiphoton absorption, and correspond to multiphoton absorption. It may be formed due to other light absorption such as light absorption or thermal influence. That is, multiphoton absorption is an example of a phenomenon that can form a modified region.
  Further, the modified region 17 functioning as the gettering region 18 may have various shapes depending on the formation pattern of the functional element 25 as long as the modified region 17 faces the formation region 25 a of the functional element 25 in the thickness direction of the semiconductor substrate 2. Can be taken.
  As an example, as shown in FIG. 16, the gettering regions 18 may be formed in a plurality of rows vertically and horizontally with respect to one forming region 25a. Further, as shown in FIG. 17A, the laser beam L1 is moved in the radial direction of the semiconductor substrate 2 while rotating the semiconductor substrate 2, so that one formation region is formed as shown in FIG. The curved gettering region 18 may be formed in at least one row with respect to 25a. Thus, when the formation line 15 for forming the gettering region 18 is spiral with respect to the semiconductor substrate 2, the modified spot distance (distance between the nearest modified spots) is substantially constant. It is desirable to change the rotation speed of the semiconductor substrate 2 and the repetition frequency of the laser light L1 so that And in any case shown in FIG.16 and FIG.17, by performing ON / OFF control of the laser beam L1, when it sees from the thickness direction of the semiconductor substrate 2, it does not cross | intersect the cutting planned line 5. A gettering region 18 may be formed inside the semiconductor substrate 2.
  Further, the modified regions 7 functioning as the cutting start region 8 may be formed in a plurality of rows so as to be aligned in the thickness direction of the semiconductor substrate 2 with respect to one cutting scheduled line 5.
  In the above embodiment, the semiconductor substrate 2 is cut by irradiating the semiconductor substrate 2 with the laser beam L2 to form the cutting start region 8 and then polishing the back surface 2b of the semiconductor substrate 2. The semiconductor substrate 2 may be cut by a method. That is, as shown in FIG. 18A, before the cutting start region 8 is formed in the semiconductor substrate 2, the back surface 2b of the semiconductor substrate 2 is polished to the polishing end planned surface 16. Then, as shown in FIG. 18B, an expand film 23 is attached to the surface 2a side of the semiconductor substrate 2, and inside the semiconductor substrate 2 (here, between the gettering region 18 and the functional element 25). A cutting starting point region 8 is formed. The plurality of semiconductor devices 20 can also be obtained by expanding the expand film 23 outward in the radial direction and cutting the semiconductor substrate 2 starting from the cutting start region 8 and the crack 21.
  Further, in the above embodiment, the gettering region 18 is formed so as not to intersect with the planned cutting line 5, but the gettering region 18 may be formed so as to intersect with the planned cutting line 5.
  Moreover, in the said embodiment, as shown in FIG.11 and FIG.12, after forming the gettering area | region 18 in the semiconductor substrate 2, the functional element 25 shall be formed, but the timing which forms the functional element 25 is as follows. It is not limited to this. For example, as shown in FIG. 19, first, the functional element 25 is formed on the surface 2 a of the semiconductor substrate 2, and the protective film 22 is attached to the surface 2 a of the semiconductor substrate 2 so as to cover all the functional elements 25. Thereafter, the back surface 2b of the semiconductor substrate 2 functions as a gettering region 18 inside the semiconductor substrate 2 (here, on the surface 2a side of the semiconductor substrate 2 with respect to the polishing end planned surface 16) with the laser light L1 incident surface. The modified region 17 may be formed.
  In addition, according to the said embodiment, the invention of the following laser processing methods and the invention of the manufacturing method of a semiconductor device are materialized.
  That is, the invention of the laser processing method modifies the inside of the semiconductor substrate by irradiating a semiconductor substrate having a front surface for forming a plurality of functional elements and a back surface opposite to the front surface with a first laser beam. Thus, the laser processing method includes a step of forming a gettering region for trapping impurities inside the semiconductor substrate. According to this laser processing method, the gettering effect can be sufficiently exerted when a plurality of functional elements are formed on the surface of the semiconductor substrate in a later step.
  In another laser processing method, a semiconductor substrate having a front surface for forming a plurality of functional elements and a back surface opposite to the front surface is irradiated with a first laser beam to modify the inside of the semiconductor substrate. Preparing a semiconductor substrate having a gettering region for trapping impurities therein, and forming a cutting line that is set to pass between positions where adjacent functional elements are formed. A cutting start region for generating a crack in the thickness direction of the semiconductor substrate is formed by irradiating the semiconductor substrate with a second laser beam to modify the inside of the semiconductor substrate. It is a laser processing method provided with the process formed in the position of the said surface side rather than the said gettering area | region inside. According to this laser processing method, the cutting start region is formed at a position on the surface side of the gettering region inside the semiconductor substrate. As a result, when the semiconductor substrate is cut in a later step, the gettering region can be used as the starting point of the cutting in addition to the crack generated from the starting point region of the cutting, and the semiconductor substrate can be cut more reliably. it can.
  In addition, the invention of the method for manufacturing a semiconductor device modifies the inside of the semiconductor substrate by irradiating a semiconductor substrate having a front surface for forming a plurality of functional elements and a back surface opposite to the front surface with a first laser beam. The gettering region for trapping impurities is formed inside, and the semiconductor substrate along the planned cutting line set so as to pass between the positions where the adjacent functional elements are formed By irradiating a second laser beam on the semiconductor substrate, the inside of the semiconductor substrate is modified to cause a crack in the thickness direction of the semiconductor substrate at a position on the surface side of the gettering region inside the semiconductor substrate. Preparing the semiconductor substrate on which a cutting start region for generation is formed, cutting at least the semiconductor substrate for each of the functional elements along the planned cutting line; Comprising a plurality obtaining step a semiconductor device comprising the functional element, a manufacturing method of a semiconductor device. According to this method of manufacturing a semiconductor device, when a semiconductor substrate is cut, in addition to the cracks that start from the cutting start region, the gettering region can also be the starting point of cutting, so that the semiconductor substrate can be cut more reliably. It can be carried out.
  DESCRIPTION OF SYMBOLS 2 ... Semiconductor substrate, 2a ... Front surface, 2b ... Back surface, 5 ... Scheduled cutting line, 8 ... Cutting origin area, 18 ... Gettering area, 20 ... Semiconductor device, 21 ... Crack, 25 ... Functional element, L1 ... Laser beam ( First laser beam), L2 ... Laser beam (second laser beam), T ... Center position.

Claims (6)

  1. Irradiating a semiconductor substrate having a front surface for forming a plurality of functional elements and a back surface opposite to the front surface with a first laser beam to modify the inside of the semiconductor substrate, thereby capturing impurities A first step of forming a gettering region within the semiconductor substrate;
    After the first step, the semiconductor substrate is irradiated with a second laser beam along a planned cutting line set so as to pass between positions where the adjacent functional elements are formed. By modifying the inside of the semiconductor substrate, a cutting start region for generating a crack in the thickness direction of the semiconductor substrate is formed at a position closer to the surface side than the gettering region inside the semiconductor substrate. Process,
    After the second step, a third step of cutting at least the semiconductor substrate for each functional element along the planned cutting line to obtain a plurality of semiconductor devices including one functional element ,
    The modified region functioning as the gettering region formed by modifying the inside of the semiconductor substrate by irradiating the first laser beam is a modification of the modified region in the thickness direction of the semiconductor substrate. Formed so that the width of the quality spot is 1-10 μm,
    The modified spot distance in the case of forming a modified region that functions as the cutting starting region formed by modifying the inside of the semiconductor substrate by irradiating the second laser light is 3.75 to 7. The modification spot distance in the case of forming a modified region that satisfies 5 μm and functions as the gettering region is 5 to 20 μm, and the modification in the case of forming a modified region that functions as the gettering region A method for manufacturing a semiconductor device , wherein a spot distance is longer than the modified spot distance when a modified region that functions as the cutting start region is formed .
  2.   In the first step, the gettering region is formed at a position closer to the back surface than a center position of the thickness of the semiconductor substrate inside the semiconductor substrate when formed as the semiconductor device. A method for manufacturing a semiconductor device according to claim 1.
  3.   The method of manufacturing a semiconductor device according to claim 1, wherein, in the third step, the back surface of the semiconductor substrate is polished so that the semiconductor substrate has a predetermined thickness.
  4.   4. The method of manufacturing a semiconductor device according to claim 1, wherein, in the second step, the semiconductor substrate is irradiated with the second laser light using the back surface of the semiconductor substrate as a laser light incident surface. 5. .
  5.   The said 2nd process WHEREIN: By irradiating the said 2nd laser beam to the said semiconductor substrate, the said crack generated from the said cutting | disconnection start area | region reaches | attains the said surface of the said semiconductor substrate at least. A manufacturing method of a semiconductor device given in any 1 paragraph.
  6.   6. The method of manufacturing a semiconductor device according to claim 1, wherein in the first step, the gettering region is formed inside the semiconductor substrate so as not to intersect with the scheduled cutting line.
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