JP3990711B2 - Laser processing equipment - Google Patents

Description

  The present invention relates to a laser processing apparatus and a laser processing method for cutting a semiconductor substrate along a planned cutting line.

  In a semiconductor device manufacturing process, it is common to form a plurality of functional elements on a semiconductor substrate such as a silicon wafer and then cut the semiconductor substrate into functional elements with a diamond blade (cutting) to obtain a semiconductor chip. (For example, see Patent Document 1).

Further, instead of cutting with the diamond blade, the semiconductor substrate may be irradiated with a laser beam having an absorptivity for the semiconductor substrate, and the semiconductor substrate may be cut by heating and melting (heating and melting processing) (for example, Patent Document 2).
JP 2001-7054 A Japanese Patent Laid-Open No. 10-163780

  However, since the cutting of the semiconductor substrate by the above-described cutting process or heat-melting process is performed after the functional element is formed on the semiconductor substrate, the functional element may be destroyed due to heat generated during the cutting, for example.

  Therefore, the present invention has been made in view of such circumstances. For example, even if a plurality of functional elements are formed on a semiconductor substrate, the functional elements are prevented from being destroyed, and the semiconductor substrate An object of the present invention is to provide a laser processing apparatus that makes it possible to accurately cut a wire along a planned cutting line.

In order to achieve the above object, a laser processing apparatus according to the present invention is a laser processing apparatus for forming a modified region serving as a starting point of cutting inside a semiconductor substrate, and a mounting table on which the semiconductor substrate is mounted And a laser light source that emits laser light, and the laser light emitted from the laser light source is condensed inside the semiconductor substrate placed on the mounting table, and the modified region is at the position of the condensing point of the laser light A condensing lens for forming a laser beam and a modified region along the semiconductor substrate in a state where the condensing point of the laser beam is located inside the semiconductor substrate in order to form the modified region inside the semiconductor substrate. A control unit that moves a condensing point of laser light, infrared transmission illumination that illuminates the semiconductor substrate placed on the mounting table with infrared rays, and the modified region in the semiconductor substrate that is illuminated with infrared rays by infrared transmission illumination an imaging device capable of imaging and the Characterized in that it obtain.

  According to these laser processing apparatuses, the modified region is formed inside the semiconductor substrate by the laser beam irradiation, but the laser beam is hardly absorbed by the surface of the semiconductor substrate in such laser beam irradiation. The surface of the semiconductor substrate does not melt. Therefore, for example, even when a plurality of functional elements are formed on the semiconductor substrate, it is possible to prevent the functional elements from being destroyed. Furthermore, according to these laser processing apparatuses and laser processing methods, the modified region is formed inside the semiconductor substrate. When the modified region is formed inside the semiconductor substrate, the semiconductor substrate is cracked with a relatively small force starting from the modified region, so the semiconductor substrate is divided and cut along the planned cutting line with high accuracy. be able to. Therefore, the semiconductor substrate can be cut with high precision along the planned cutting line.

The laser processing apparatus according to the present invention prevents the functional elements from being destroyed even if a plurality of functional elements are formed on the semiconductor substrate, for example, and accurately cuts the semiconductor substrate along the planned cutting line. Make it possible to do.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. When configuring the semiconductor substrate and the semiconductor chip according to the present embodiment, the semiconductor substrate is irradiated with laser light with the focusing point aligned inside, and a modified region by multiphoton absorption is formed inside the semiconductor substrate. Use laser processing methods. This laser processing method, particularly multiphoton absorption, will be described first.

Photon energy hν is smaller than the band gap E _G of absorption of the material becomes transparent. Therefore, a condition under which absorption occurs in the material is hv> E _G. However, even when optically transparent, increasing the intensity of the laser beam very Nhnyu> of _{E G} condition (n = 2,3,4, ···) the intensity of laser light becomes very high. This phenomenon is called multiphoton absorption. In the case of a pulse wave, the intensity of the laser beam is determined by the peak power density (W / cm ² ) at the condensing point of the laser beam. For example, the multiphoton is obtained under conditions where the peak power density is 1 × 10 ⁸ (W / cm ² ) or more. Absorption occurs. The peak power density is determined by (energy per pulse of laser light at the condensing point) / (laser beam cross-sectional area of laser light × pulse width). In the case of a continuous wave, the intensity of the laser beam is determined by the electric field intensity (W / cm ² ) at the condensing point of the laser beam.

  The principle of laser processing according to this embodiment using such multiphoton absorption will be described with reference to FIGS. FIG. 1 is a plan view of the semiconductor substrate 1 during laser processing, FIG. 2 is a cross-sectional view taken along the line II-II of the semiconductor substrate 1 shown in FIG. 1, and FIG. 3 shows the semiconductor substrate 1 after laser processing. 4 is a cross-sectional view taken along line IV-IV of the semiconductor substrate 1 shown in FIG. 3, and FIG. 5 is a cross-sectional view taken along line V-V of the semiconductor substrate 1 shown in FIG. FIG. 6 is a plan view of the cut semiconductor substrate 1.

  As shown in FIGS. 1 and 2, there is a desired cutting line 5 on the surface 3 of the semiconductor substrate 1 where the semiconductor substrate 1 is to be cut. The planned cutting line 5 is a virtual line extending in a straight line (the actual cutting line 5 may be used as the planned cutting line 5 on the semiconductor substrate 1). In the laser processing according to the present embodiment, the modified region 7 is formed by irradiating the semiconductor substrate 1 with the laser beam L while aligning the condensing point P inside the semiconductor substrate 1 under the condition that multiphoton absorption occurs. In addition, a condensing point is a location where the laser beam L is condensed.

  The condensing point P is moved along the planned cutting line 5 by relatively moving the laser light L along the planned cutting line 5 (that is, along the direction of the arrow A). Thereby, as shown in FIGS. 3 to 5, the modified region 7 is formed only inside the semiconductor substrate 1 along the planned cutting line 5, and the modified starting region 9 (scheduled cutting portion) 9 is formed by the modified region 7. Is formed. In the laser processing method according to the present embodiment, the modified region 7 is not formed by causing the semiconductor substrate 1 to generate heat when the semiconductor substrate 1 absorbs the laser light L. The modified region 7 is formed by transmitting the laser beam L through the semiconductor substrate 1 and generating multiphoton absorption inside the semiconductor substrate 1. Therefore, since the laser beam L is hardly absorbed by the surface 3 of the semiconductor substrate 1, the surface 3 of the semiconductor substrate 1 is not melted.

  In the cutting of the semiconductor substrate 1, if there is a starting point at the cutting position, the semiconductor substrate 1 breaks from the starting point, so that the semiconductor substrate 1 can be cut with a relatively small force as shown in FIG. 6. Therefore, the semiconductor substrate 1 can be cut without causing unnecessary cracks in the surface 3 of the semiconductor substrate 1.

  Note that the following two methods are conceivable for cutting the semiconductor substrate starting from the cutting start region. One is a case where after the cutting start region is formed, an artificial force is applied to the semiconductor substrate, so that the semiconductor substrate is cracked from the cutting start region and the semiconductor substrate is cut. This is cutting when the thickness of the semiconductor substrate is large, for example. An artificial force is applied when, for example, bending stress or shear stress is applied to the semiconductor substrate along the cutting start region of the semiconductor substrate, or thermal stress is generated by applying a temperature difference to the semiconductor substrate. That is. The other one is a case where by forming the cutting start region, the semiconductor substrate is naturally cracked from the cutting start region to the cross-sectional direction (thickness direction) of the semiconductor substrate, and as a result, the semiconductor substrate is cut. . For example, when the thickness of the semiconductor substrate is small, the cutting start region is formed by one row of modified regions, and when the thickness of the semiconductor substrate is large, a plurality of regions can be formed in the thickness direction. This is made possible by forming the cutting start region by the reformed regions formed in a row. In addition, even when this breaks naturally, in the part to be cut, the part corresponding to the part where the cutting starting point region is formed without cracking ahead on the surface of the part corresponding to the part where the cutting starting point region is not formed Since it is possible to cleave only, the cleaving can be controlled well. In recent years, since the thickness of a semiconductor substrate such as a silicon wafer tends to be thin, such a cleaving method with good controllability is very effective.

  Now, as the modified region formed by multiphoton absorption in the present embodiment, there is a melting processing region described below.

A condensing point is set inside the semiconductor substrate, and laser light is irradiated under conditions where the electric field intensity at the condensing point is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is 1 μs or less. As a result, the inside of the semiconductor substrate is locally heated by multiphoton absorption. By this heating, a melt processing region is formed inside the semiconductor substrate. The melt processing region is a region once solidified after melting, a region in a molten state, a region in which the material is re-solidified from a molten state, and can also be referred to as a phase-changed region or a region in which the crystal structure has changed. The melt treatment region can also be said to be a region in which one structure is changed to another structure in a single crystal structure, an amorphous structure, or a polycrystalline structure. In other words, for example, a region changed from a single crystal structure to an amorphous structure, a region changed from a single crystal structure to a polycrystalline structure, or a region changed from a single crystal structure to a structure including an amorphous structure and a polycrystalline structure. To do. When the semiconductor substrate has a silicon single crystal structure, the melt processing region has, for example, an amorphous silicon structure. The upper limit value of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). The pulse width is preferably 1 ns to 200 ns, for example.

  The inventor has confirmed through experiments that a melt-processed region is formed inside a silicon wafer. The experimental conditions are as follows.

(A) Semiconductor substrate: silicon wafer (thickness 350 μm, outer diameter 4 inches)
(B) Laser
Light source: Semiconductor laser pumped Nd: YAG laser
Wavelength: 1064nm
Laser light spot cross-sectional area: 3.14 × 10 ⁻⁸ cm ²
Oscillation form: Q switch pulse
Repeat frequency: 100 kHz
Pulse width: 30ns
Output: 20μJ / pulse
Laser light quality: TEM ₀₀
Polarization characteristics: Linearly polarized light (C) Condensing lens
Magnification: 50 times
N. A. : 0.55
Transmittance with respect to laser beam wavelength: 60% (D) Moving speed of mounting table on which semiconductor substrate is mounted: 100 mm / second

  FIG. 7 is a view showing a photograph of a cross section of a part of a silicon wafer cut by laser processing under the above conditions. A melt processing region 13 is formed inside the silicon wafer 11. The size in the thickness direction of the melt processing region 13 formed under the above conditions is about 100 μm.

  The fact that the melt processing region 13 is formed by multiphoton absorption will be described. FIG. 8 is a graph showing the relationship between the wavelength of the laser beam and the transmittance inside the silicon substrate. However, the reflection components on the front side and the back side of the silicon substrate are removed to show the transmittance only inside. The above relationship was shown for each of the thickness t of the silicon substrate of 50 μm, 100 μm, 200 μm, 500 μm, and 1000 μm.

  For example, when the thickness of the silicon substrate is 500 μm or less at the wavelength of the Nd: YAG laser of 1064 nm, it can be seen that the laser light is transmitted by 80% or more inside the silicon substrate. Since the thickness of the silicon wafer 11 shown in FIG. 7 is 350 μm, the melt processing region 13 by multiphoton absorption is formed near the center of the silicon wafer, that is, at a portion of 175 μm from the surface. The transmittance in this case is 90% or more with reference to a silicon wafer having a thickness of 200 μm, so that the laser beam is hardly absorbed inside the silicon wafer 11 and almost all is transmitted. This is not because the laser beam is absorbed inside the silicon wafer 11 and the melt processing region 13 is formed inside the silicon wafer 11 (that is, the melt processing region is formed by normal heating with laser light) It means that the melt processing region 13 is formed by multiphoton absorption. The formation of the melt processing region by multiphoton absorption is described in, for example, “Evaluation of processing characteristics of silicon by picosecond pulse laser” on pages 72 to 73 of the 66th Annual Meeting of the Japan Welding Society (April 2000). Are listed.

  Silicon wafers are cracked in the cross-sectional direction starting from the cutting start region formed by the melt processing region, and the cracks reach the front and back surfaces of the silicon wafer, resulting in cutting. Is done. The cracks that reach the front and back surfaces of the silicon wafer may grow naturally or may grow by applying force to the silicon wafer. In addition, when a crack naturally grows from the cutting start region to the front and back surfaces of the silicon wafer, the case where the crack grows from a state where the melt treatment region forming the cutting starting region is melted, and the cutting start region There is a case where cracks grow when the solidified region is melted from the melted region. However, in both cases, the melt processing region is formed only inside the silicon wafer, and the melt processing region is formed only inside the cut surface after cutting as shown in FIG. When the cutting start region is formed in the semiconductor substrate by the melt processing region, unnecessary cracks that are off the cutting start region line are unlikely to occur during cleaving, so that cleaving control is facilitated.

  As described above, the case of the melt processing region has been described as the modified region formed by multiphoton absorption. However, if the cutting origin region is formed as follows in consideration of the crystal structure of the semiconductor substrate and its cleavage property, the It becomes possible to cut the semiconductor substrate with a smaller force and with high accuracy starting from the cutting start region.

  That is, in the case of a substrate made of a single crystal semiconductor having a diamond structure such as silicon, the cutting start region is formed in a direction along the (111) plane (first cleavage plane) or the (110) plane (second cleavage plane). Is preferred. In the case of a substrate made of a zinc-blende-type III-V group compound semiconductor such as GaAs, it is preferable to form the cutting start region in the direction along the (110) plane.

  Note that the semiconductor substrate is oriented along a direction in which the above-described cutting start region is to be formed (for example, a direction along the (111) plane in the single crystal silicon substrate) or a direction perpendicular to the direction in which the cutting start region is to be formed. If a flat is formed, it becomes possible to easily and accurately form the cutting start region along the direction in which the cutting start region is to be formed on the semiconductor substrate by using the orientation flat as a reference.

  A laser processing apparatus used in the laser processing method described above will be described with reference to FIG. FIG. 9 is a schematic configuration diagram of the laser processing apparatus 100.

  The laser processing apparatus 100 includes a laser light source 101 that generates laser light L, a laser light source control unit 102 that controls the laser light source 101 to adjust the output and pulse width of the laser light L, and the reflection function of the laser light L. And a dichroic mirror 103 arranged to change the direction of the optical axis of the laser light L by 90 °, a condensing lens 105 for condensing the laser light L reflected by the dichroic mirror 103, and a condensing lens The mounting table 107 on which the semiconductor substrate 1 irradiated with the laser beam L condensed by the lens 105 is mounted, the θ stage 108 for rotating the mounting table 107, and the mounting table 107 are moved in the X-axis direction. An X-axis stage 109, a Y-axis stage 111 for moving the mounting table 107 in the Y-axis direction orthogonal to the X-axis direction, and the mounting table 107 in the X-axis and Y-axis directions A Z-axis stage 113 for moving in the orthogonal Z-axis direction and a stage control unit 115 for controlling the movement of these four stages 108, 109, 111, 113 are provided.

  The mounting table 107 transmits infrared light through the semiconductor substrate 1 so that the semiconductor substrate 1 is illuminated with infrared rays by the infrared transmission illumination 116 and the infrared transmission illumination 116 that generates infrared rays to illuminate the semiconductor substrate 1 with infrared rays. And a support portion 107a supported on the illumination 116.

  Since the Z-axis direction is a direction orthogonal to the surface 3 of the semiconductor substrate 1, it is the direction of the focal depth of the laser light L incident on the semiconductor substrate 1. Therefore, by moving the Z-axis stage 113 in the Z-axis direction, the condensing point P of the laser light L can be adjusted to the surface 3 or the inside of the semiconductor substrate 1. Further, the converging point P is moved in the X (Y) axis direction by moving the semiconductor substrate 1 in the X (Y) axis direction by the X (Y) axis stage 109 (111).

The laser light source 101 is an Nd: YAG laser that generates pulsed laser light. Other lasers that can be used for the laser light source 101 include an Nd: YVO ₄ laser, an Nd: YLF laser, and a titanium sapphire laser. In the case of forming the melt processing region, it is preferable to use an Nd: YAG laser, an Nd: YVO ₄ laser, or an Nd: YLF laser. In this embodiment, pulsed laser light is used for processing the semiconductor substrate 1, but continuous wave laser light may be used as long as multiphoton absorption can be caused.

  The laser processing apparatus 100 further includes an observation light source 117 that generates visible light to illuminate the semiconductor substrate 1 mounted on the mounting table 107 with visible light, and the same optical axis as the dichroic mirror 103 and the condensing lens 105. And a visible light beam splitter 119 disposed above. A dichroic mirror 103 is disposed between the beam splitter 119 and the condensing lens 105. The beam splitter 119 has a function of reflecting about half of visible light and transmitting the other half, and is arranged so as to change the direction of the optical axis of visible light by 90 °. About half of the visible light generated from the observation light source 117 is reflected by the beam splitter 119, and the reflected visible light passes through the dichroic mirror 103 and the condensing lens 105, and passes through the planned cutting line 5 of the semiconductor substrate 1. Illuminate the containing surface 3.

  The laser processing apparatus 100 further includes an imaging element 121 and an imaging lens 123 disposed on the same optical axis as the beam splitter 119, the dichroic mirror 103, and the condensing lens 105. An example of the image sensor 121 is a CCD camera. The reflected light of the visible light that illuminates the surface 3 including the line 5 to be cut passes through the condensing lens 105, the dichroic mirror 103, and the beam splitter 119, is imaged by the imaging lens 123, and is imaged by the imaging device 121. And becomes imaging data. If the semiconductor substrate 1 is illuminated with infrared rays by the infrared transmission illumination 116 and the imaging data processing unit 125 described later aligns the observation surface of the imaging lens 123 and the imaging element 121 with the inside of the semiconductor substrate 1, the semiconductor substrate 1. The imaging data inside the semiconductor substrate 1 can be obtained by imaging the inside of the semiconductor substrate 1.

  The laser processing apparatus 100 further includes an imaging data processing unit 125 to which imaging data output from the imaging element 121 is input, an overall control unit 127 that controls the entire laser processing apparatus 100, and a monitor 129. The imaging data processing unit 125 calculates focus data for focusing the visible light generated by the observation light source 117 on the surface 3 based on the imaging data. The stage control unit 115 controls the movement of the Z-axis stage 113 based on the focus data so that the visible light is focused on the surface 3. Therefore, the imaging data processing unit 125 functions as an autofocus unit. Further, the imaging data processing unit 125 calculates image data such as an enlarged image of the surface 3 based on the imaging data. This image data is sent to the overall control unit 127, where various processes are performed by the overall control unit, and sent to the monitor 129. Thereby, an enlarged image or the like is displayed on the monitor 129.

  Data from the stage control unit 115, image data from the imaging data processing unit 125, and the like are input to the overall control unit 127. Based on these data, the laser light source control unit 102, the observation light source 117, and the stage control unit are input. By controlling 115, the entire laser processing apparatus 100 is controlled. Therefore, the overall control unit 127 functions as a computer unit.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Example 1 of Semiconductor Substrate]
Example 1 of the semiconductor substrate according to the present invention will be described with reference to FIGS. 10 is a perspective view of the semiconductor substrate 1 according to the first embodiment, FIG. 11 is a cross-sectional view taken along the line XI-XI of the semiconductor substrate 1 shown in FIG. 10, and FIG. 12 is a semiconductor substrate 1 shown in FIG. FIG. 13 is a view showing a photograph of a laser mark provided on the surface of the semiconductor substrate 1 shown in FIG. 10.

  The semiconductor substrate 1 according to Example 1 is a disc-shaped silicon wafer having a thickness of 350 μm and an outer diameter of 4 inches, and is cut so that a part of the peripheral portion of the semiconductor substrate 1 is a straight line as shown in FIG. An orientation flat (hereinafter referred to as “OF”) 15 is formed to be missing.

  As shown in FIG. 11, a cutting start region 9 a extending in a direction parallel to the OF 15 is provided inside the semiconductor substrate 1 at a predetermined distance from the center of the outer diameter (hereinafter referred to as “reference origin”) inside the semiconductor substrate 1. A plurality are formed for each. In addition, a plurality of cutting starting point regions 9b extending in a direction perpendicular to the OF 15 are formed in the semiconductor substrate 1 at predetermined intervals from the reference origin. As shown in FIG. 12, the cutting start region 9 a is formed only inside the semiconductor substrate 1 and does not reach the front surface 3 and the back surface 17 of the semiconductor substrate 1. The same applies to the cutting start region 9b. Each of the cutting starting point region 9 a and the cutting starting point region 9 b is formed by a melt processing region formed in one row inside the semiconductor substrate 1.

  As shown in FIG. 10, a laser mark 19 is provided at a position immediately above the reference origin on the surface 3 of the semiconductor substrate 1. By both the laser mark 19 and the OF 15, the positions of the cutting start region 9 a and the cutting start region 9 b formed inside the semiconductor substrate 1 can be grasped. That is, both the laser mark 19 and the OF 15 function as identification marks for identifying the positions of the cutting start area 9 a and the cutting start area 9 b formed inside the semiconductor substrate 1. In addition to providing the laser mark 19 on the cutting start region, the laser mark 19 is formed in a place other than a functional part such as a circuit formed on the semiconductor substrate, or a part not used as a semiconductor device in the peripheral part of the semiconductor substrate. May be. The laser mark 19 is formed by melting the surface 3 of the semiconductor substrate 1 using a clean laser marking method called soft marking that does not generate dust or heat, and the laser mark 19 has a diameter as shown in FIG. 1 μm concave shape.

  Next, a method for manufacturing the semiconductor substrate 1 using the laser processing apparatus 100 described above will be described with reference to FIGS. FIG. 14 is a flowchart for explaining a method for manufacturing the semiconductor substrate 1.

  First, the light absorption characteristics of the semiconductor substrate 1 are measured with a spectrophotometer or the like (not shown). Based on this measurement result, a laser light source for generating a laser beam for forming the laser mark 19 on the surface 3 of the semiconductor substrate 1 and a laser beam L having a wavelength transparent to the semiconductor substrate 1 or a wavelength with little absorption. 101 is selected (S101). Subsequently, the thickness of the semiconductor substrate 1 is measured. Based on the measurement result of the thickness and the refractive index of the semiconductor substrate 1, the amount of movement of the semiconductor substrate 1 in the Z-axis direction is determined (S103). This is because the laser beam L positioned on the surface 3 of the semiconductor substrate 1 in order to position the condensing point P of the laser beam L having a wavelength transparent to the semiconductor substrate 1 or a wavelength with little absorption in the semiconductor substrate 1. The amount of movement of the semiconductor substrate 1 in the Z-axis direction with reference to the condensing point P. This movement amount is input to the overall control unit 127.

  The semiconductor substrate 1 is mounted on the support member 107 a of the mounting table 107 of the laser processing apparatus 100. Then, visible light is generated from the observation light source 117 to illuminate the semiconductor substrate 1 (S105). The surface 3 of the illuminated semiconductor substrate 1 is imaged by the image sensor 121. Imaging data captured by the imaging element 121 is sent to the imaging data processing unit 125. Based on this imaging data, the imaging data processing unit 125 calculates focus data such that the visible light focus of the observation light source 117 is located on the surface 3 (S107).

  This focus data is sent to the stage controller 115. The stage controller 115 moves the Z-axis stage 113 in the Z-axis direction based on the focus data (S109). Thereby, the focal point of the visible light of the observation light source 117 is positioned on the surface 3 of the semiconductor substrate 1. The imaging data processing unit 125 calculates enlarged image data of the surface 3 of the semiconductor substrate 1 based on the imaging data. This enlarged image data is sent to the monitor 129 via the overall control unit 127, whereby an enlarged image of the surface 3 of the semiconductor substrate 1 is displayed on the monitor 129.

  Subsequently, the semiconductor substrate 1 is rotated by the θ stage 108 so that the direction of the OF 15 of the semiconductor substrate 1 coincides with the stroke direction of the Y stage 111 (S111). Further, the X-axis stage 109 and the Y-axis stage 111 are arranged so that the condensing point of the laser beam for forming the laser mark 19 on the surface 3 of the semiconductor substrate 1 is a position immediately above the reference origin on the surface 3 of the semiconductor substrate 1. Then, the semiconductor substrate 1 is moved by the Z-axis stage 113 (S113). In this state, laser light is irradiated to form a laser mark 19 at a position immediately above the reference origin on the surface 3 of the semiconductor substrate 1 (S115).

  Thereafter, the movement amount data determined in step S103 and input in advance to the overall control unit 127 is sent to the stage control unit 115. The stage control unit 115 moves the semiconductor substrate 1 in the Z-axis direction by the Z-axis stage 113 to a position where the condensing point P of the laser light L is inside the semiconductor substrate 1 based on the movement amount data (S117). .

  Subsequently, laser light L is generated from the laser light source 101 and the semiconductor substrate 1 is irradiated with the laser light L. Since the condensing point P of the laser beam L is located inside the semiconductor substrate 1, the melting processing region is formed only inside the semiconductor substrate 1. Then, the semiconductor substrate 1 is moved by the X-axis stage 109 and the Y-axis stage 111, and the cutting start point region 9 a extending in the direction parallel to the OF 15 and the cutting start point region 9 b extending in the direction perpendicular to the OF 15 inside the semiconductor substrate 1. Are formed at predetermined intervals from the reference origin (S119), and the semiconductor substrate 1 according to the first embodiment is manufactured.

  If the semiconductor substrate 1 is illuminated with infrared rays by the infrared transmission illumination 116 and the imaging data processing unit 125 aligns the imaging lens 123 and the observation surface of the imaging element 121 with the inside of the semiconductor substrate 1, the inside of the semiconductor substrate 1. The cutting start area 9a and the cutting start area 9b formed in the above can be imaged to acquire imaging data and can be displayed on the monitor 129.

As described above, in the semiconductor substrate 1 according to the first embodiment, the condensing point P is aligned inside the semiconductor substrate 1, and the peak power density at the condensing point P is 1 × 10 ⁸ (W / cm ² ) or more. In addition, the laser beam L is irradiated under the condition that the pulse width is 1 μs or less, thereby forming a melt processing region by multiphoton absorption inside the semiconductor substrate 1. In the irradiation with the laser beam L that can generate multiphoton absorption, the laser beam L is hardly absorbed by the surface 3 of the semiconductor substrate 1, so that the surface 3 of the semiconductor substrate 1 is not melted. Therefore, in the semiconductor device manufacturing process, a functional element can be formed on the surface 3 of the semiconductor substrate 1 by a conventional process. Since the back surface 17 of the semiconductor substrate 1 is not melted, it is needless to say that the back surface 17 of the semiconductor substrate 1 can be handled in the same manner as the front surface 3 of the semiconductor substrate 1.

  Further, in the semiconductor substrate 1 according to the first embodiment, the cutting start region 9 a and the cutting start region 9 b are formed inside the semiconductor substrate 1 in the melting processing region. If the melt processing region is formed inside the semiconductor substrate 1, the semiconductor substrate 1 is cracked with a relatively small force starting from the melt processing region, so that it is high along the cutting start region 9a and the cutting start region 9b. The semiconductor substrate 1 can be broken and cut with accuracy. Therefore, in the manufacturing process of the semiconductor device, it is not necessary to perform cutting and heating / melting processing after forming the functional element as in the conventional case. For example, the semiconductor device 1 is formed on the back surface 17 of the semiconductor substrate 1 along the cutting start region 9a and the cutting start region 9b. The semiconductor substrate 1 can be cut only by applying a knife edge. Therefore, it is possible to prevent the functional element from being broken by cutting the semiconductor substrate 1 after the functional element is formed.

  Further, in the semiconductor substrate 1 according to the first embodiment, both the laser mark 19 and the OF 15 serve as a reference for the positions of the cutting start region 9 a and the cutting start region 9 b formed in the semiconductor substrate 1. Therefore, in the manufacturing process of the semiconductor device, based on the laser mark 19 and the OF 15, the positions of the cutting start region 9a and the cutting start region 9b formed in the semiconductor substrate 1 are grasped, and the patterning of the functional elements is performed. The semiconductor substrate 1 can be cut or the like.

  Note that, when the melt processing region is formed inside the semiconductor substrate 1, the melt processing region is used as a starting point (that is, along the cutting starting region 9a and the cutting starting region 9b) without intentionally applying an external force. In some cases, cracks may occur inside the semiconductor substrate 1. Whether or not this crack reaches the front surface 3 and the back surface 17 of the semiconductor substrate 1 depends on the position of the melt processing region in the thickness direction of the semiconductor substrate 1, the size of the melt processing region with respect to the thickness of the semiconductor substrate 1, and the like. Involved. Therefore, by adjusting the position, size, etc. of the melt processing region formed inside the semiconductor substrate 1, the semiconductor substrate 1 is handled or subjected to a heat cycle in the manufacturing process of the semiconductor device. Various controls can be performed so that cracks do not reach the front surface 3 and the back surface 17 of the semiconductor substrate 1 or so that cracks reach the front surface 3 and the back surface 17 of the semiconductor substrate 1 immediately before cutting.

[Example 2 of semiconductor substrate]
Example 2 of the semiconductor substrate according to the present invention will be described with reference to FIGS. The semiconductor substrate 1 according to Example 2 is a disc-shaped GaAs wafer having a thickness of 350 μm and an outer diameter of 4 inches, and is cut so that a part of the peripheral edge of the semiconductor substrate 1 is a straight line as shown in FIG. The OF 15 is formed as a result.

  This semiconductor substrate 1 has an outer edge portion 31 (the outer portion of the two-dot chain line in FIG. 15) along the outer edge, and is inside the inner portion 32 (the inner portion of the two-dot chain line in FIG. 15) of this outer edge portion 31. As in the semiconductor substrate 1 according to the first embodiment, a plurality of cutting start region 9a extending in a direction parallel to the OF 15 and a plurality of cutting starting regions 9b extending in a direction perpendicular to the OF 15 are formed. . As described above, the cutting start regions 9 a and 9 b are formed in a lattice shape inside the inner portion 32, so that the inner portion 32 is partitioned into a large number of rectangular partitions 33.

  In the manufacturing process of the semiconductor device, a functional element is formed for each partition 33, and then the semiconductor substrate 1 is cut along the cutting start regions 9a and 9b so that each partition 33 corresponds to an individual semiconductor chip. Will be.

  And in the corner | angular part 33a by the side of the outer edge 31 of the division part 33 located in the outer edge part 31 side among the many division parts 33, as shown in FIG. 16, the cutting origin area | region 9a and the cutting origin area | region 9b cross | intersect. Is formed. That is, in the corner portion 33a, the cutting start area 9a ends beyond the cutting start area 9b, and the cutting start area 9b ends beyond the cutting start area 9a. In addition, “the partition portion 33 positioned on the outer edge portion 31 side among the many partition portions 33” means, in other words, “the partition portion 33 formed adjacent to the outer edge portion 31 among the many partition portions 33. It can also be said.

  Next, a method for manufacturing the semiconductor substrate 1 according to the second embodiment will be described. As shown in FIG. 17, a mask 36 is prepared in which an opening 35 having a shape equivalent to the inner portion 32 of the semiconductor substrate 1 is formed. Then, a mask 36 is overlaid on the semiconductor substrate 1 so that the inner portion 32 is exposed from the opening 35. As a result, the outer edge 31 of the semiconductor substrate 1 is covered with the mask 36.

  In this state, for example, by using the laser processing apparatus 100 described above, the laser beam is irradiated with the focusing point inside the semiconductor substrate 1 to form a melt processing region by multiphoton absorption inside the semiconductor substrate 1. Thus, the cutting origin regions 9a and 9b are formed at a predetermined distance from the laser light incident surface of the semiconductor substrate 1 (that is, the surface of the semiconductor substrate 1 exposed from the opening 35 of the mask 36).

  At this time, the planned cutting lines 5 serving as the laser light scanning lines are set in a lattice pattern with the OF 15 as a reference. If the starting point 5a and the end point 5b of each planned cutting line 5 are positioned on the mask 36, the semiconductor substrate Thus, the laser beam is reliably applied to the inner portion 32 of the first laser beam under the same conditions. As a result, the melt processing region formed inside the inner portion 32 can be formed in almost the same state at any location, and it is possible to form the precise cutting start regions 9a and 9b.

  In addition, without using the mask 36, the start point 5 a and the end point 5 b of each planned cutting line 5 are positioned in the vicinity of the boundary between the inner portion 32 and the outer edge portion 31 of the semiconductor substrate 1, and the laser is cut along each planned cutting line 5 It is also possible to form the cutting start regions 9a and 9b inside the inner portion 32 by irradiating light.

  As described above, according to the semiconductor substrate 1 according to the second embodiment, functional elements are formed on the surface of the semiconductor substrate 1 in the semiconductor device manufacturing process for the same reason as the semiconductor substrate 1 according to the first embodiment. In addition, it is possible to prevent the functional element from being broken by cutting the semiconductor substrate 1 after the functional element is formed.

  In addition, since the cutting start regions 9 a and 9 b are formed inside the inner portion 32 of the semiconductor substrate 1 and the cutting start regions 9 a and 9 b are not formed on the outer edge portion 31, the mechanical strength of the semiconductor substrate 1 as a whole. Will be improved. Therefore, it is possible to prevent the semiconductor substrate 1 from being unexpectedly cut in the transporting process of the semiconductor substrate 1 or the heating process for forming the functional element.

  Further, in the corner portion 33a of the partition portion 33 located on the outer edge portion 31 side, the cutting starting point regions 9a and 9b are formed so as to intersect with each other, so that the corner portion 33a is also different from other portions of the partition portion 33. Similarly, the formation of the cutting starting point regions 9a and 9b is reliable and satisfactory. Therefore, it is possible to prevent chipping or cracking from occurring in the semiconductor chip corresponding to the partition portion 33 when the semiconductor substrate 1 is cut.

  Further, as shown in FIG. 18, since the cutting start regions 9a and 9b are accommodated inside the semiconductor substrate 1 and are not exposed to the outside, the gas is generated when forming the melt processing regions constituting the cutting start regions 9a and 9b. Occurrence is also prevented.

  Further, since the melt processing regions constituting the cutting start regions 9a and 9b are formed inside the semiconductor substrate 1, a gettering effect for capturing the impurities is expected, and impurities such as heavy metals are expected in the semiconductor device manufacturing process. Can be removed from the device active region. The same applies to the semiconductor substrate 1 according to the first embodiment.

[Embodiments of Semiconductor Chip and Semiconductor Device Manufacturing Method]
An embodiment of a semiconductor chip and a method for manufacturing a semiconductor device according to the present invention will be described with reference to FIG. FIG. 19 is a perspective view of the semiconductor chip 21 according to the embodiment.

  The semiconductor chip 21 according to the first embodiment is formed as follows. That is, using the semiconductor substrate 1 according to Example 1 or Example 2 described above, the laser mark 19 indicates the positions of the cutting start region 9a and the cutting start region 9b formed in the semiconductor substrate 1 in the semiconductor device manufacturing process. And a plurality of functional elements 23 are formed on the surface 3 of the semiconductor substrate 1 by patterning. Then, after an inspection process such as a probe test, the semiconductor substrate 1 is cut by applying a knife edge to the back surface 17 of the semiconductor substrate 1 along the cutting start region 9a and the cutting start region 9b based on the laser mark 19 and the OF 15. Then, the semiconductor chip 21 is obtained.

  As shown in FIG. 19, the peripheral portion of the semiconductor chip 21 formed in this way is surrounded by the cutting surface 25, and the cutting starting point region 9 a or the cutting starting point region is formed on the cutting surface 25 of the end surface of the semiconductor chip 21. 9b. Since both the cutting start region 9a and the cutting start region 9b are formed by the melting processing region, the semiconductor chip 21 has the melting processing region on the cut surface 25.

  As described above, according to the semiconductor chip 21 according to the embodiment, since the cut surface 25 is protected by the melt processing region, occurrence of chipping and cracking in the cut surface 25 can be prevented. In addition, since the peripheral portion of the semiconductor chip 21 is surrounded by the cut surface 25, the peripheral portion of the semiconductor chip 21 is surrounded by the melt processing region, thereby improving the bending strength of the semiconductor chip 21. it can.

  As mentioned above, although embodiment of this invention was described in detail, it cannot be overemphasized that this invention is not limited to the said embodiment.

  In the above embodiment, the laser mark and OF are provided on the surface of the semiconductor substrate as an identification mark for identifying the position of the cutting start region formed inside the semiconductor substrate.For example, a plurality of laser marks may be provided, Alternatively, an identification mark can be provided on the surface of the semiconductor substrate by various methods such as drawing a line.

  Moreover, although the said embodiment was a case where a cutting | disconnection origin area | region was formed in the inside of a semiconductor substrate at the grid | lattice form, since a cutting | disconnection origin area | region is formed by laser processing, it is a cutting | disconnection origin on the line of arbitrary shapes. Regions can be formed.

  Furthermore, although the semiconductor chip of the above embodiment has a peripheral portion surrounded by a cut surface, even if only a part of the peripheral portion is a cut surface, chipping and cracking on the cut surface is caused by the melt processing region. Generation | occurrence | production is prevented and the bending strength of a semiconductor chip will improve.

It is a top view of a semiconductor substrate under laser processing by a laser processing method concerning this embodiment. It is sectional drawing along the II-II line of the semiconductor substrate shown in FIG. It is a top view of the semiconductor substrate after the laser processing by the laser processing method concerning this embodiment. FIG. 4 is a cross-sectional view of the semiconductor substrate shown in FIG. 3 taken along line IV-IV. FIG. 5 is a cross-sectional view taken along line VV of the semiconductor substrate shown in FIG. 3. It is a top view of the semiconductor substrate cut | disconnected by the laser processing method which concerns on this embodiment. It is a figure showing the photograph of the section in the part of silicon wafer cut by the laser processing method concerning this embodiment. It is a graph which shows the relationship between the wavelength of the laser beam and the transmittance | permeability inside a silicon substrate in the laser processing method which concerns on this embodiment. It is a schematic block diagram of the laser processing apparatus which concerns on this embodiment. 1 is a perspective view of a semiconductor substrate according to Example 1. FIG. It is sectional drawing along the XI-XI line of the semiconductor substrate shown in FIG. It is sectional drawing along the XII-XII line | wire of the semiconductor substrate shown in FIG. It is the figure showing the photograph of the laser mark provided in the surface of the semiconductor substrate shown in FIG. 3 is a flowchart for explaining a method of manufacturing a semiconductor substrate according to the first embodiment. 6 is a plan view of a semiconductor substrate according to Example 2. FIG. FIG. 16 is an enlarged view of a main part of the semiconductor substrate shown in FIG. 15. FIG. 16 is a plan view for illustrating the method for manufacturing the semiconductor substrate shown in FIG. 15. It is sectional drawing along the XVIII-XVIII line of the semiconductor substrate shown in FIG. It is a perspective view of the semiconductor chip which concerns on an Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 5 ... Planned cutting line, 7 ... Modification | denaturation area | region, 13 ... Melting process area | region, 100 ... Laser processing apparatus, 101 ... Laser light source, 105 ... Condensing lens, 107 ... Mounting stand, 115 ... Stage control Part (control part), 116 ... infrared transmission illumination, 121 ... imaging element, 127 ... overall control part (control part), L ... laser beam, P ... condensing point.

Claims (2)

A laser processing apparatus for forming a modified region that is a starting point of cutting inside a semiconductor substrate,
A mounting table on which the semiconductor substrate is mounted;
A laser light source for emitting laser light;
A condensing lens for condensing the laser light emitted from the laser light source inside the semiconductor substrate placed on the mounting table and forming the modified region at the position of the condensing point of the laser light. When,
In order to form the modified region inside the semiconductor substrate, the laser beam is focused along a cutting line of the semiconductor substrate with a laser beam focusing point positioned inside the semiconductor substrate. A control unit for moving the point;
Infrared transmission illumination for illuminating the semiconductor substrate mounted on the mounting table with infrared rays;
An imaging device capable of imaging the modified region in the semiconductor substrate illuminated with infrared by the infrared transmission illumination;
A laser processing apparatus comprising:   The laser processing apparatus according to claim 1, wherein the control unit controls movement of at least one of the mounting table and the condensing lens.

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