JPH09323300A - Substrate dividing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make dicing performable with small cutting allowance without receiving any restriction of this cutting allowance due to the edge width of a rotary blade and also the nonlinear dicing achievable as well as to make any damage to a divided substrate so as to get off with smallness in an easy manner, in regard to a dividing method of brittle substrates such as a glass substrate, a ceramic substrate, a silicon wafer, a compound semiconductor wafer or the like, especially a substrate dividing method dividing a semiconductor wafer, where plural pieces of elements are set up, and an optical element substrate into each individual element unit. SOLUTION: A groove 12 is formed in the surface of a substrate, putting a photoabsorber 15 provided with an optical characteristic to absorb a specified wavelength of light into a bottom part of this groove 12, and then a laser beam 16 is irradiated and it is absorbed in the photoabsorber 15 on the bottom part of the groove 12, through which the substrate 10 is divided along the groove 12 by the volumetric heat expansion of the photoabsorber 15 and the vicinity of the bottom part at that time. In brief, a medium absorbing, for example, a laser beam and an infrared ray is reapplied to the surface of a brittle substrate with light permeability, whereby the substrate is divided into pieces by way of making the medium absorb the light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dividing a brittle substrate such as a glass substrate, a ceramic substrate, a silicon wafer, a compound semiconductor wafer, etc., and particularly to a semiconductor wafer having a plurality of elements arranged thereon or an optical element substrate as individual elements. The present invention relates to a board dividing method for dividing into units.

[0002]

2. Description of the Related Art Conventionally, as a method of separating and dividing a semiconductor wafer into element units such as chips and pellets, for example,
Generally, a dicing groove is formed by a dicer using a rotating blade, and cracking is performed along the groove (see JP-A-51-28754, JP-A-56-135007, etc.).

[0003]

However, although a diamond grindstone blade is generally used in the dicer, the width of the dicing groove is regulated by the blade width, so that a cutting margin of 50 μm or more is required and The area of the dicing area occupying the whole becomes large and the wafer 1
It was hindering the improvement in the number of chips taken per sheet. Conversely, if a narrow blade is used, there is a problem that microcracks tend to occur in the lateral direction.

In manufacturing a laser diode, as shown in FIG. 5, after forming each laser diode element 51 on a substrate wafer 50 and exposing an active layer 53 of each element by etching to form a reflecting surface. A predetermined portion 55 on the bottom surface of the etching groove was cut by a diamond blade 54 and divided into elements along a predetermined direction 56. In this case, since the blade width of the blade 54 is about the etching groove, the center of the groove bottom which is separated by a distance T from the reflection surface is avoided while avoiding the corner of the element, but is emitted from the reflection surface. There has been a problem that the laser light L is reflected on a protruding portion of the distance T and causes interference. Of course, as shown by the one-dot chain line, it is practically impossible to bring the cut position closer to the vicinity of the element end face because the element end face is cut. Furthermore, the fragments cannot be scattered at the time of division to damage the reflection surface of the element, or the fragments adhere to the end faces, so that a predetermined reflectance cannot be obtained. In particular,
Recently sapphire that it is going to be used for the blue laser diode manufacturing (Al2 _{O 3)} substrate is greater Mohs hardness 9
(Reference: Since diamond has a hardness of 10), when it is separated by a mechanical cutting force, cracks are likely to occur and it is extremely difficult to perform dicing with the above dicer.

Moreover, the conventional dicing with a rotary blade usually forms a linear groove and is limited to a rectangular divided shape. Therefore, dicing is performed non-linearly along a zigzag cleavage direction different from the orthogonal direction. It wasn't the case. By the way, if dicing is performed on these brittle substrates only with a dicer, a dicing groove for dividing the pellet is formed in advance on the surface of the semiconductor wafer to a point where wafer cracking occurs, and then water is injected into the groove. A method has been proposed in which a wafer is solidified at a low temperature and the wafer is divided by volume expansion at that time (Japanese Patent Laid-Open No. 57-713).
No. 7). However, in this case, complicated equipment for low-temperature solidification is required, and the low-temperature solidification treatment may cause cooling damage to the entire wafer.

In view of the above conventional problems, an object of the present invention is to make the dicing area of the cutting margin as small as possible.
Another object of the present invention is to provide a substrate dividing method that can perform non-linear dicing and that can easily and less damage a substrate to be divided.

[0007]

The inventor of the present application has found that glass is a transparent body and cannot be cleaved only by a laser, but a medium for absorbing laser light is applied to the surface of the glass and the laser light is applied to the medium. Focusing on the fact that glass can be broken by absorbing the (machine tool technology study group, edited by Takeshi Yasui "Machine tool series"
Laser processing "P127-134," Glass cutting processing by YAG laser "(written by Toshiji Kurobe) Ohkita Publishing, published September 10, 1990).

In order to solve the above-mentioned problems, the substrate dividing method of the invention according to claim 1 forms a groove in the substrate and uses a light absorbing material having optical characteristics for absorbing light of a predetermined wavelength. And then irradiate with the light to be absorbed by the light absorbing material at the bottom of the groove, and the substrate is divided along the groove by the volume thermal expansion of the light absorbing material and the vicinity of the bottom at that time. It is characterized by doing.

Further, in the substrate dividing method according to the invention of claim 2, after forming the groove, a resist is applied to be buried in the bottom portion of the groove, and then the carbide generated by the heat treatment is left, and The charcoal-based material is used as the absorbent. Furthermore, the substrate dividing method according to claim 3 is
The invention according to claim 1 or 2 is characterized in that a substrate having a cleavage orientation different from a right angle is used, and the groove is formed along the cleavage orientation to divide the substrate into a shape different from a rectangular shape in a plan view. It is suitable for manufacturing other triangular or hexagonal polygonal chips.

As the substrate in the present invention, for example, a silicon wafer is used when a silicon semiconductor is used, and a substrate having an epitaxial growth layer is used. In addition, laser light, infrared light, or the like can be used as irradiation light, and a high-output light is preferable. Further, the light absorbing material is an organic pigment generally used for a printing ink or the like, for example, an azo pigment,
Alternatively, a phthalocyanine-based condensed polycyclic pigment or the like, or more specifically, a synthetic dye used in a commercially available magic ink (trade name) may be used.

The light irradiation is preferably performed from the back side of the substrate, but may be performed from the front side as long as it does not affect the element forming region on the front side. Further, the depth and width of the groove are determined by the breaking property of the brittle substrate, the expandability of the light absorbing material during light irradiation, and the like.

[0012]

According to the present invention, a relatively shallow groove is previously formed in such a brittle substrate by etching or the like, and the groove can be divided by light irradiation. , Chip or pellet substrate 1
The number of pieces per sheet can be remarkably improved. In addition, since it can be applied if it is a brittle substrate having light transmittance,
The substrate can be divided without damaging the substrate, that is, without affecting the quality, without cooling or heating the entire substrate. Furthermore, as in the conventional dicer, only linear dicing is performed, but in the present invention, at least a groove pattern can be appropriately selected, and for example, division along the cleavage direction can be easily performed without separately using complicated equipment. .
In particular, when applied to the manufacture of a laser diode chip in which a reflecting surface is formed by etching, the groove according to the present invention can be easily formed by utilizing the etching process and can be divided as a groove for cleaving. It is possible to realize a flat reflecting surface without causing interference.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example in which the present invention is applied to a laser diode manufacturing process. The substrate 10 is made of a light-transmissive GaAs material for manufacturing a laser diode, and the active layer 1 is formed on the substrate 10 according to a normal laser element forming process (not shown).
After the element regions such as 3 are formed, the substrate dividing processing step of the present invention is performed for dividing each chip 11.

First, the division groove 12 corresponding to a predetermined chip division pattern is formed by a dry etching technique to a depth enough to expose the reflection surface of each chip. Also,
The groove 12 is formed in a direction along the cleavage plane direction of the GaAs substrate.
A groove 12 having a width of about 2 μm is used. Next, the light absorbing material 15 is put in the groove 12. As the light absorbing material 15, an ink solution containing the above-described pigment is used. This ink solution has a pigment of a color that absorbs the laser light used in the next laser irradiation step. For example, when an Ar laser is used, the wavelength is 0.49 μm.
Has a material that absorbs the light of, or the He-Ne laser has a wavelength of 0.63 μm, and the YAG laser has a wavelength of 0.63 μm.
It is only necessary to absorb 1.06 μm light (refer to the above-mentioned document “Glass cutting by YAG laser”)
Blue coating ink is said to be suitable for the AG laser. ). The light absorbing material 15 is injected or buried in the groove by spin-coating the surface of the substrate in advance, then wiping off the excess solution on the surface and removing the light absorbing material 15 only at the bottom of the groove 12.

With the light absorbing material 15 remaining as described above, the laser light is irradiated from the back surface of the substrate 10. At this time, in order to avoid the influence on the element formation region on the substrate surface side as much as possible, the focus point of the laser light 16 is adjusted by the optical lens system 17 so as to be aligned with the bottom of the groove 12, and the residual light absorber 15 is exposed to the laser light 16. Focus. As a result, the light absorbing material 15 absorbs the laser light 16 that has passed through the substrate 10 to locally and rapidly expand, and the surrounding substrate 10 portion is also heated and expanded.
Cracks grow in the direction of the back surface of the substrate 10 and along the direction of formation of the grooves, and each chip 11 can be divided. Thus, in the manufacture of the laser diode chip in which the reflecting surface is formed by etching, the groove 12 can be easily formed by using the etching process for forming the reflecting surface. As a result, it is possible to divide the surface in a direction substantially the same as that of the reflection surface, and it is possible to eliminate a protrusion caused by an extra cutting margin generated when a diamond blade is used. That is, it is possible to obtain a laser diode chip having a flat reflecting surface without causing interference of reflected light caused by the protruding portion. Further, by setting the groove 12 in the cleavage direction, cleavage can be facilitated, and a smooth division can be performed with an optimum chip size.

FIG. 2 shows an example of cutting a sapphire (Al ₂ O ₃ ) substrate for manufacturing a blue laser diode. The substrate 1 is made of single crystal sapphire having excellent light transmittance, and the surface thereof has an epitaxial layer 2 as an element forming region of a laser diode.
Is provided. This epitaxial layer 2 is made of Ga
It has a multilayer structure composed of N, InGaN, AlGaN, and GaN, and has a total thickness of about 4 μm. The thickness D of the substrate 1 is about 80 μm including the epitaxial layer 2.

After the laser diode elements are formed on the substrate 1 (the element forming step is omitted), the laser diode chips are separated and divided in the same manner as in FIG. Also in this case, the dividing grooves 3 corresponding to the predetermined chip dividing pattern are formed on the substrate 1 by using the dry etching technique.
In this example, the width W of the groove 3 is 4 μm and the depth S is 8 μm. Next, the light absorbing material 4 is put in the groove 3. As the light absorbing material 4, an ink solution containing the above-described pigment is used. Then, the laser light 5 is irradiated from the back surface of the substrate 1, and the laser light 5 is focused on the residual light absorbing material 4 by the optical lens system 6. As a result, the light absorbing material 4 and the peripheral portion of the substrate 1 absorb the laser light 5 that has passed through the substrate 1, and as shown in FIG.
Since the thermal expansion locally increases rapidly to C, the crack grows along the back surface direction A of the substrate 1, and the substrate can be divided along the formation direction of the groove 3.

In the embodiments shown in FIGS. 1 and 2, the light absorbing material is applied to the bottom of the groove, but a photoresist material which has been used in the semiconductor manufacturing process in the past may be used. That is, after the groove is formed, coating is performed by a spin coating method, and then ashing (ash) is performed so that the groove remains only at the bottom of the groove.
ing) treatment, and heat treatment in a nitrogen gas atmosphere to carbonize the remaining resist may be used as a light absorbing material. Further, the above-described substrate dividing method is applied to a silicon substrate or a GaAs substrate whose main wafer surface is the {100} face 30 as shown in the dividing groove pattern of FIG. be able to.

Further, according to the present invention, as shown in FIG.
The present invention can also be applied to a 1｝ wafer main surface substrate. That is, in the case of FIG. 4, the cleavage direction is <110>, and the rectangular division in the right angle direction is suitable, but in the case of FIG.
Since it is inclined in the direction of 60 degrees as compared with the above, division of the honeycomb shape is suitable. To this end, a honeycomb-shaped dividing groove pattern 20 of FIG. 3 along the cleavage direction is formed in advance, so that a hexagonal chip division in plan view is divided according to the dividing procedure of the embodiment of FIG. 1 or FIG. It can be carried out. Of course, a triangular chip in plan view can be manufactured by forming grooves in a repetitive pattern of a triangle other than the hexagon. Note that, in addition to such a honeycomb shape different from a grid, even a more complicated groove pattern can be arbitrarily formed by using an etching technique to divide a chip into a desired planar shape.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a method of dividing a laser diode substrate that is an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a method of dividing a sapphire substrate which is an embodiment of the present invention.

FIG. 3 is a wafer plan view showing an example of honeycomb division of the present invention.

FIG. 4 is a wafer plan view showing an example of rectangular division of the present invention.

FIG. 5 is a wafer sectional view showing an example of division of a conventional laser diode substrate.

[Explanation of symbols]

 1 Substrate 2 Epitaxial Layer 3 Groove 4 Light Absorbing Material 5 Laser Light 12 Groove 15 Light Absorbing Material 16 Laser Light

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location H01L 21/78 Q

Claims (3)

[Claims] 1. A groove is formed on a substrate, and a light absorbing material having an optical characteristic of absorbing light of a predetermined wavelength is placed at the bottom of the groove,
Then, the light is irradiated to be absorbed by the light absorbing material at the bottom of the groove, and the substrate is divided along the groove by volume thermal expansion of the light absorbing material and the vicinity of the bottom at that time. Board dividing method. 2. After forming the groove, a resist is applied to be buried in the bottom of the groove, and then the carbide generated by the heat treatment is left, and the carbide is used as the light absorbing material. The substrate dividing method according to claim 1. 3. A substrate whose cleavage direction is different from a right angle is used.
3. The substrate dividing method according to claim 1, wherein the groove is formed along the cleavage direction to divide the groove into a shape different from a rectangular shape in plan view.