JP2001284292A - Chip division method for semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable easy division without requiring large pressure and improve yield by raising probability of division starting from a division groove. SOLUTION: A groove 5 for reducing the thickness is formed on the surface at a semiconductor layer formation side of a semiconductor wafer 1 and a scribe line 6 as a division groove is formed. After heating by casting a laser beam 21 on a groove lower part 8 only along a scribe line 6, liquid nitrogen 22 is immediately brought into contact with the entire semiconductor wafer 1, and thermal impact is given. Cracks are generated and proceed by the thermal impact starting from the bottom of the scribe line 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for dividing a semiconductor wafer having a semiconductor layer formed on a substrate into a number of semiconductor chips.

[0002]

2. Description of the Related Art As a method of dividing a semiconductor wafer, a groove is formed on the wafer by dicing or a scribe line is formed by scribing.
Generally, a method of breaking the wafer along the groove or the scribe line by breaking along the groove or the scribe line is used. Dicing is a method of forming a dicing groove in a wafer by relatively moving a rotary blade of a dicer (dicing saw) and a wafer. What is scribe?
This is a method of forming a scribe line on a wafer by relatively moving a sharpened blade of a scriber and a wafer. Breaking is a method of breaking a wafer by pressing the wafer with a pressing blade or a pressing roller to perform three-point bending.

[0003] High hardness materials (for example, sapphire, GaN
Semiconductor wafer using a substrate consisting of
Since it is difficult to break the wafer by breaking only by forming a shallow dicing groove or scribe line, the brakes are added after devising deep dicing or scribing after significantly thinning the substrate. Had to be done. For example, the following methods are known as methods for dividing a wafer in which a gallium nitride-based compound semiconductor is stacked on a sapphire substrate into chips.

(1) The method described in Japanese Patent No. 2859478 includes the following steps. Step of polishing the thickness of the sapphire substrate to 200 μm or less Step of scribing the wafer surface so that the shortest side of the chip is longer than the thickness, dividing the wafer along the scribe line, and dividing the chip into chips

(2) The method described in Japanese Patent No. 2765644 includes the following steps. A dicing process in which a groove is cut deeper than the thickness of the gallium nitride-based compound semiconductor layer using a dicer. A polishing process in which the thickness of the sapphire substrate is reduced by polishing. Process After the scribe process, a dividing process to divide the wafer into chips

(3) The method described in Japanese Patent No. 2914014 includes the following steps. First step of polishing and thinning the sapphire substrate Second step of exposing the p-type layer (gallium nitride-based compound semiconductor) to the n-type layer to expose the plane of the n-type layer Etching the plane of the n-type layer Or a third step of dicing to expose the plane of the sapphire substrate, a fourth step of dicing or scribing the thinned sapphire substrate, and cutting the wafer at the plane of the sapphire substrate exposed in the third step

(4) The method described in Japanese Patent No. 2780618 includes the following steps. A step of forming a first split groove from a gallium nitride-based compound semiconductor layer side in a linear manner in a desired chip shape by etching, and forming a plane on which an electrode can be formed in a part of the first split groove Wafer sapphire substrate Forming a second split groove (preferably scribe) having a line width smaller than the line width of the first split groove at a position coinciding with the line of the first split groove from the side; Dividing the wafer into chips along the second split groove

(5) The method described in Japanese Patent No. 2861991 includes the following steps. A first split groove is linearly formed (by etching) in a desired chip shape from the gallium nitride compound semiconductor layer side of the wafer, and the first split groove is penetrated through the gallium nitride compound semiconductor layer to sapphire. Step of forming to a depth excluding a part of the substrate At a position matching the line of the first split groove from the sapphire substrate side of the wafer, a second split groove having a line width smaller than the line width of the first split groove Step of Forming (preferably Scribing) Step of Dividing the Wafer into Chips Along First and Second Split Grooves

[0009]

The method of dividing a semiconductor wafer using a substrate made of a high-hardness material as described above has the following problems. Since the process of breaking the wafer by breaking is performed for each scribe line, it takes time to divide the wafer and the efficiency is low. Even if a deep dicing groove is formed or the thickness of the substrate is significantly reduced, it is not easy because a large pressing force is required for braking. Since the mechanical stress at the time of braking is quite high, it may be broken starting from a portion other than the scribe line, and the chip becomes defective, resulting in poor yield.

[0010] An object of the present invention is to solve the above-mentioned problems, to enable easy division without requiring a large pressing force, and to increase the probability of division from the dividing groove as a starting point, thereby increasing the yield. An object of the present invention is to provide a method for dividing a semiconductor wafer into chips.

[0011]

According to the present invention, there is provided a method of dividing a semiconductor wafer having a semiconductor layer formed on a substrate into a plurality of semiconductor chips, wherein a dividing groove is formed on a surface of the semiconductor wafer. And a step of generating and propagating a crack in the thickness direction of the semiconductor wafer starting from the dividing groove by applying a thermal shock to the semiconductor wafer.

The "dividing groove" may be formed on the surface of the semiconductor wafer on the side where the semiconductor layer is formed, may be formed on the surface of the semiconductor wafer on the side where the semiconductor layer is not formed, or may be formed on both surfaces. You can also.

Although the dividing groove is not particularly limited,
A groove by scribe (scribe line) and a groove by dicing, etching or blast can be exemplified. However, a V-shaped groove (typically a scribe line) or a groove having a groove bottom width of 5 μm or less is preferable in order to easily generate a crack by concentrating stress due to thermal shock.

"Dicing" may be performed by an ordinary method using, for example, a rotary blade having diamond abrasive grains attached thereto. Examples of the “etching” include dry etching such as reactive ion etching, ion milling, focused beam etching, and ECR etching, and wet etching using a mixed acid of sulfuric acid and phosphoric acid. An etching-resistant mask having a pattern that leaves an exposed portion is formed. "Blasting" means blasting a fine particle blast material having an average particle diameter of 1 to 30 [mu] m made of, for example, alumina, silicon carbide, boron, diamond or the like at a blast pressure of 0.2
A method of blasting at about 0.8 MPa can be exemplified. Before blasting, a blast-resistant mask having a pattern that leaves a grid-like exposed portion on the surface of a semiconductor wafer is formed. This is a method in which the kinetic energy of a high-speed blasted fine particle blast material is used to microscopically cut a part of a semiconductor layer or a substrate.

"Thermal shock" refers to a phenomenon in which an object (in this case, a semiconductor wafer) undergoes a large and rapid temperature change to generate a shocking thermal stress.

The width of the temperature change due to the thermal shock is not particularly limited, but is preferably 100 ° C./sec or more.
000 ° C. is more preferred. If the width of this temperature change is small, the shock thermal stress becomes small, making it difficult for cracks to occur. If the width of this temperature change is large, it becomes difficult to produce the same width in the device and medium.

The rate of temperature change upon thermal shock is not particularly limited, but is preferably 150 ° C./sec or more,
200,000 ° C./sec is more preferred. If the rate of this temperature change is low, the shock thermal stress is reduced and cracks are unlikely to occur. If the rate of this temperature change is high, it is difficult to produce the same rate in terms of equipment and medium.

The method for applying the thermal shock is not particularly limited.
For example, the following (1) and (2) can be exemplified. (1) Contacting the cooling medium with the semiconductor wafer (at about room temperature) (2) Contacting the cooling medium with the semiconductor wafer immediately after heating the semiconductor wafer

Here, the "cooling medium" is not particularly limited, but may be a low-temperature (preferably extremely low-temperature) gas, liquid or solid. The most preferred cooling medium in terms of low temperature and cost is liquid nitrogen.

The method of "heating" is not particularly limited, and examples thereof include laser beam irradiation, radiant heat, and contact with a high-temperature gas, liquid, or solid.

As a specific embodiment of the method of applying a thermal shock, the following embodiment can be exemplified. After irradiating only a portion of the semiconductor wafer below the groove along the dividing groove with a laser beam and heating, immediately contact liquid nitrogen with the entire semiconductor wafer (cooling with liquid nitrogen or the like instead of liquid nitrogen) (A low-temperature blade or the like may be brought into contact with the dividing groove.) Only the portion of the semiconductor wafer on which the dividing groove is to be formed is irradiated with a laser beam and heated, and immediately the surface of the dividing groove is to be formed. Forming a dividing groove on the substrate, and immediately contacting the entire surface of the semiconductor wafer with liquid nitrogen (instead of liquid nitrogen, a low-temperature blade cooled with liquid nitrogen or the like may be brought into contact with the dividing groove) After heating the entire semiconductor wafer to such an extent that the semiconductor layer does not deteriorate, immediately contact liquid nitrogen with the entire semiconductor wafer.

The present invention is not particularly limited by the constituent material of the substrate, but is particularly effective when the substrate is made of a high hardness material having a Mohs hardness of 8 or more. For example,
This is particularly effective for dividing a semiconductor wafer whose substrate is made of sapphire or GaN and whose semiconductor layer is made of a gallium nitride-based compound semiconductor.

[0023]

1 and 2 show a method for dividing a semiconductor wafer into chips according to an embodiment of the present invention. First, the semiconductor wafer 1 to be divided will be described. The wafer 1 is composed of a substrate 2 and a semiconductor layer 3 constituting a light emitting element (light emitting diode, laser diode, etc.) formed on the surface of the substrate 2. Main layers 11-
16 and electrodes (not shown).

The substrate 2 is made of sapphire, has a square shape of, for example, 2 inches (about 5 cm) and a thickness of 3 inches.
50 μm, the surface on which the semiconductor layer is formed is a-plane # 11-2
0｝. The optimal direction of the axis direction is C-axis 45 °
Direction. However, the substrate is not limited to this, and a material (for example, using a substrate made of GaN, etc.),
The thickness, crystal plane, and the like can be appropriately changed.

Each of the main layers 11 to 16 is a gallium nitride-based compound semiconductor (the buffer layer is made of AlN but may be made of GaN) formed by a metal organic chemical vapor deposition method. A layer 11 is formed, a Si-doped n-type GaN contact layer 12 is formed on the layer 11, an n-type GaN cladding layer 13 is formed on the layer 12, and a GaN barrier layer is formed on the layer 13. InG
A light emitting layer 14 having a multiple quantum well structure in which an aN well layer is alternately stacked is formed, and an Mg-doped p-type A
An lGaN cladding layer 15 is formed, and M
A g-doped p-type GaN contact layer 16 is formed. The thickness of the entire main layers 11 to 16 is not particularly limited, but is, for example, 2 to 15 μm.

However, the main layer is not limited to this structure. When the composition of each layer is changed, the light emitting layer is changed to, for example, a single quantum well structure, or when the substrate 2 is made of GaN, the buffer layer 11 is formed. It can be changed as appropriate, such as omitting it or providing a resonance structure in the case of a laser diode.

In order to divide the semiconductor wafer 1 into a large number of semiconductor chips, the following steps are performed. (1) As shown in FIGS. 1A and 2A, a groove 5 for reducing the thickness is formed on the surface of the semiconductor wafer 1, for example, on the semiconductor layer formation side by dicing (etching or blasting may be used). The thickness reducing groove 5 is for reducing the thickness of the divided portion of the semiconductor wafer 1 and preventing the semiconductor layer 3 from chipping. If the semiconductor layer 3 is directly scribed, chipping easily occurs in the semiconductor layer 3 itself. However, when the thickness reducing groove 5 is formed by dicing, etching or blasting, the chipping can be prevented or reduced.

The width and depth of the thickness reducing groove 5 are set so that the tip of the cutter enters the thickness reducing groove 5 in a scribe step performed later. For example, the width of the thinning groove 5 is set to 30 μm, the depth of the thinning groove 5 is removed by the entire thickness of the semiconductor layer 3, and the depth of the thinning groove 5 is further reduced to, for example, about 5 μm in the substrate 2.
A large number of the thinning grooves 5 formed have a plane lattice shape.

(2) As shown in FIG. 2 (b), the surface of the substrate 2 having a thickness of 350 μm on the side where the semiconductor layer is not formed is polished by a polishing machine to make the substrate 2 uniform in thickness. The thickness is reduced to about 100 μm.

(3) As shown in FIG. 2C, a scribe line 6 as a dividing groove is formed by scribing with a cutter (diamond point) 7 at the center in the width direction of the groove bottom of the thickness reducing groove 5. I do. The cross-sectional shape of the scribe line is substantially V-shaped (notch-shaped), and its depth is, for example, 0.1 mm.
It is about 5 μm. The planar dimensions of the chip to be split are 1
It is a square with sides of about 350 μm, and therefore, the pitch between adjacent scribe lines 6 is also 350 μm.

(4) As shown in FIG. 2D, a portion 8 below the groove along the scribe line 6 of the semiconductor wafer
Only the laser beam 21 is irradiated from the irradiator 20 to heat only the laser beam. Specifically, for example, a CO2 laser is used, the output is set to 0.7 W, and the beam diameter is set to 50 μm.
Then, the laser beam 21 is irradiated from the irradiator 20 along the scribe line 6 while relatively moving the semiconductor wafer 1 and the irradiator 20 in the surface direction of the semiconductor wafer 1. For example, the semiconductor wafer 1 may be supported on a table (not shown) movable in the x-y direction, and the table may be moved to send the semiconductor wafer 1 in the x-y direction which is the plane direction. The feed rate is, for example, 50 mm /
Seconds.

By the irradiation of the laser beam 21, the temperature of the lower portion 8 along the scribe line 6 becomes, for example, 12
The temperature is about 00 ° C., which does not affect the bottom shape of the scribe line 6. A part of the heat is conducted from the substrate 2 to the semiconductor layer 3, but does not deteriorate the semiconductor layer 3.

(5) After irradiation with the laser beam 21,
Immediately, as shown in FIG. 1 (b) and FIG. 2 (e), the semiconductor wafer 1 is brought into contact with liquid nitrogen 22 to give a thermal shock to the semiconductor wafer 1. Specifically, the semiconductor wafer 1 is placed on a liquid-permeable base 24 with porous ceramics, and the liquid nitrogen 22 jetted from the upper nozzle 23 is brought into contact with the entire semiconductor wafer 1 and, at the same time, excess liquid nitrogen 22 is passed through. Collected from the liquid base 24. The liquid permeable table 24 may be suctioned by vacuum.

The thermal shock, that is, the semiconductor wafer 1 undergoes a large and rapid cooling of being instantaneously cooled from the above-mentioned heated state to the vicinity of -196 ° C. which is the temperature of liquid nitrogen, so that a shock thermal stress is generated. Then, cracks 9 are generated and propagate from the bottom of the scribe line 6 substantially in the thickness direction of the substrate 2. The extension of the crack 9 indicates that the semiconductor wafer 1
In the case of stopping in the middle of the thickness, it is necessary to further brake, but since the crack 9 is formed, the braking can be facilitated. Further, when the extension of the crack 9 extends over the entire thickness of the semiconductor wafer 1,
Since division into a large number of semiconductor chips 10 is achieved, braking can be omitted.

According to the chip dividing method of the present embodiment, the following effects can be obtained. When chip division is achieved by thermal shock, the division is completed in an instant, so that the efficiency is very good. It can be easily divided without requiring pressing force such as braking. Further, even when chip division is not achieved due to thermal shock, since the crack 9 is formed as described above, braking can be easily performed with a small pressing force. Unlike braking, the yield is good because the probability of cracking from the scribe line 6 is high.

[0036]

EXAMPLE A group of examples schematically shown in FIGS. 3A to 3K show variations of the dividing groove, and other thermal shocks and the like are the same as those of the embodiment. Example 1 shown in FIG. 3A is an example in which a scribe line 6 is formed as a dividing groove on the semiconductor layer forming side (directly on the semiconductor layer 3). Example 2 shown in FIG. 4B is an example in which scribe lines 6 are formed as division grooves on the side where no semiconductor layer is formed. In the third embodiment shown in FIG. 3C, a groove 26 formed by dicing, etching or blasting is used as a dividing groove on the semiconductor layer forming side.
This is an example of forming. The groove 26 is preferably of a small width. Example 4 shown in FIG. 9D is an example in which a groove 26 is formed as a dividing groove by dicing, etching or blasting on the side where no semiconductor layer is formed. The groove 26 is preferably of a small width. Example 5 shown in FIG.
This is an example in which scribe lines 6 are formed as division grooves on the semiconductor layer formation side and the semiconductor layer non-formation side. Example 6 shown in FIG. 9F is an example in which grooves 26 are formed as dicing grooves by dicing, etching, or blasting on the semiconductor layer forming side and the semiconductor layer non-forming side. The groove 26 on either one (preferably on the semiconductor layer forming side) is preferably of a small width. Example 7 shown in FIG. 9G is an example in which a groove 26 formed by dicing, etching or blasting is formed as a dividing groove on the side where a semiconductor layer is formed, and a scribe line 6 is formed as a dividing groove on the side where a semiconductor layer is not formed. It is. Example 8 shown in FIG. 9H shows an example in which a scribe line 6 is formed as a dividing groove on the side where a semiconductor layer is formed and a groove 26 is formed as a dividing groove on the side where no semiconductor layer is formed by dicing, etching or blasting. It is. In Example 9 shown in FIG. 9I, dicing was performed as a groove for reducing the thickness on the semiconductor layer forming side.
In this example, a groove 5 is formed by etching or blasting, a scribe line 6 is formed as a dividing groove at the bottom of the groove, and a scribe line 6 is formed as a dividing groove on the side where no semiconductor layer is formed. Example 1 shown in FIG.
0 indicates that a scribe line 6 is formed as a dividing groove on the semiconductor layer forming side, a dicing, etching or blasting groove 5 is formed as a thickness reducing groove on the non-semiconductor layer forming side, and a dividing groove is formed at the bottom of the groove. Is an example in which the scribe line 6 is formed. Example 11 shown in FIG.
Forms a narrow groove 26 by dicing, etching or blasting as a dividing groove on the semiconductor layer forming side, and forms a wide groove 5 by dicing, etching or blasting on the non-semiconductor layer forming side as a reducing groove. In this example, a narrow groove 26 is formed at the bottom of the groove as a dividing groove by dicing, etching or blasting.

It should be noted that the present invention is not limited to the above-described embodiment, and may be embodied by appropriately changing the scope of the invention as follows, for example, as follows. (1) The order of the scribing step in FIG. 2C and the laser beam irradiation (heating) step in FIG. 2D is reversed.
That is, after irradiating only a portion of the semiconductor wafer 1 on which a dividing groove is to be formed with a laser beam and heating, a scribe line 6 as a dividing groove is immediately formed on the surface of the dividing groove.

(2) In the laser beam irradiating step of FIG. 2D, a plurality of laser beams 21 are simultaneously radiated on the lower portion 8 along the plurality of scribe lines 6 to quickly execute this step. To do.

(3) The laser beam irradiation step of FIG. 2D is replaced with a step of bringing a heating medium into contact with the entire semiconductor wafer 1 and heating the semiconductor layer 3 to such an extent that the semiconductor layer 3 is not deteriorated. As the heating medium, radiant heat from a hot plate or the like, high-temperature gas (air, nitrogen, etc.), liquid (water, oil, etc.) or solid (heating table, etc.) can be used.

(4) The contact of the liquid nitrogen in FIG. 2E with a low-temperature blade (not shown) cooled by liquid nitrogen or the like is brought into contact with the scribe line 6. The low-temperature blade rapidly removes heat and gives a thermal shock.

(3) The semiconductor chip is not limited to the light emitting element, but may be an electronic device such as a light receiving element or an FET.

[0042]

As described above in detail, according to the method of dividing a semiconductor wafer into chips according to the present invention, the chip can be easily divided without requiring a large pressing force, and the chip can be divided starting from the dividing groove. It has an excellent effect that the probability can be increased to increase the yield.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a method for dividing a semiconductor wafer into chips according to an embodiment of the present invention.

FIG. 2 is a sectional view showing steps of the chip dividing method.

FIG. 3 is a sectional view showing an embodiment of the chip dividing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor wafer 2 Substrate 3 Semiconductor layer 5 Thickening groove 6 Scribe line 8 Lower part of groove 9 Crack 10 Semiconductor chip 20 Irradiator 21 Laser beam 22 Liquid nitrogen 23 Nozzle 24 Liquid permeable table

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaki Hashimura 1 Ogatai Ogatai, Kasuga-cho, Nishikasugai-gun, Aichi F-term in Toyota Gosei Co., Ltd. (reference) 4E068 AD01 DA10

Claims (15)

[Claims] 1. A method for dividing a semiconductor wafer having a semiconductor layer formed on a substrate into a plurality of semiconductor chips, comprising: forming a dividing groove on a surface of the semiconductor wafer; A method of dividing a semiconductor wafer into chips, the method including a step of generating and propagating a crack in a substantially thickness direction of the semiconductor wafer starting from the dividing groove by applying an impact. 2. The method according to claim 1, wherein a dividing groove is formed on a surface of the semiconductor wafer on a side where a semiconductor layer is formed. 3. The semiconductor wafer chip dividing method according to claim 1, wherein a dividing groove is formed on a surface of the semiconductor wafer on a side where the semiconductor layer is not formed. 4. The range of temperature change due to the thermal shock is 2
The method according to claim 1, wherein the temperature is from 00 to 2000 ° C. 5. 5. A temperature change rate in the thermal shock,
The method according to claim 1, wherein the temperature is 200 to 200,000 ° C./sec. 6. The semiconductor wafer chip dividing method according to claim 1, wherein the method of applying the thermal shock is to bring a cooling medium into contact with the semiconductor wafer. 7. The semiconductor wafer chip according to claim 1, wherein the method of applying the thermal shock comprises contacting a cooling medium with the semiconductor wafer immediately after heating the semiconductor wafer. Split method. 8. The method according to claim 6, wherein the cooling medium is a low-temperature gas, liquid or solid. 9. The method according to claim 6, wherein the cooling medium is liquid nitrogen. 10. The semiconductor wafer chip dividing method according to claim 7, wherein the heating method is laser beam irradiation, radiant heat, or contact of a high-temperature gas, liquid or solid. 11. A method of applying a thermal shock, comprising: irradiating a laser beam only to a portion of a semiconductor wafer below a groove along a dividing groove, heating the semiconductor wafer, and immediately bringing liquid nitrogen into contact with the entire semiconductor wafer. Claims 1 to 5
The method of dividing a semiconductor wafer into chips according to any one of the above. 12. The method of applying a thermal shock, comprising: irradiating a laser beam only to a portion of a semiconductor wafer on which a dividing groove is to be formed, heating the portion, and immediately forming a dividing groove on a surface of the dividing groove to be formed. The method according to any one of claims 1 to 5, wherein liquid nitrogen is brought into contact with the entire semiconductor wafer immediately thereafter. 13. The method of applying a thermal shock, comprising: heating the entire semiconductor wafer to such an extent that the semiconductor layer is not deteriorated;
6. The method according to claim 1, wherein liquid nitrogen is immediately brought into contact with the entire semiconductor wafer. 14. The method according to claim 1, wherein the substrate is made of a high-hardness material having a Mohs hardness of 8 or more. 15. The method according to claim 1, wherein the substrate is made of sapphire or GaN, and the semiconductor layer is made of a gallium nitride-based compound semiconductor.