JPH11283939A - Dicing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of a chip, when cutting a semiconductor substrate with a step on a rear surface by covering the one surface side of a work with the step at the one surface side for eliminating the step, and by cutting the work for dividing. SOLUTION: To eliminate a step due to a rear-surface electrode 5 of a semiconductor substrate 1, a rear surface 1a is covered with a convering film 14. For the covering film 14, the mixture of novolac resin and an organic solvent or the mixture of cyclized rubber and the organic solvent such as photoresist are used. The photoresist has solubility with respect to the organic solvent, such as acetone or an exclusive release solvent. Then, the semiconductor substrate 1 is placed on an adhesive 9 so that the rear surface 1a faces down. The semiconductor substrate 1 being fixed in this manner is cut for dividing into a plurality of cells. After dividing, the cells are dipped into the organic solvent or the release solvent, thus making the covering film 14 to be melted into solution for removal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dicing method for dividing a work having an uneven surface into a plurality of devices, and more particularly to a dicing method for manufacturing a solar cell on which electrodes on a semiconductor substrate are formed. Related to the dicing method.

[0002]

2. Description of the Related Art In recent years, as a power source for an artificial satellite, a space station, or the like, for example, a thin solar cell attached to a flexible substrate has been used. The solar cell is desirably lightweight, and the thickness of the solar cell is also set to about 0.05 to 0.2 mm.
A cover glass having a thickness of about 0.2 mm is used.

FIG. 3 shows a typical structure of a solar cell used in such a space environment. 1 is a semiconductor substrate, 2
Is a diffusion layer, 3 is a front electrode, 4 is an antireflection film, 5 is a back electrode, and 6 is a silicon oxide film. The back electrode 5 is formed of a plurality of metal films such as aluminum, silver or aluminum, titanium, palladium, and silver in order from the semiconductor substrate 1 side. This aluminum is for improving the solar absorptivity.

[0004] The solar cell must withstand not only the environment in outer space but also the environment until the artificial satellite is launched into outer space. by the way,
When used in a terrestrial environment, a particular problem is corrosion of the electrode material. There is no problem because the front surface electrode 3 on the light receiving surface side is protected by the cover glass, but the back surface electrode 5 is exposed and easily corroded. Therefore, as shown in FIG. 4, the aluminum is covered with another metal film 7 formed on the aluminum so as not to be directly exposed.

[0005] Next, as shown in FIGS. 5 and 6, a manufacturing process of the solar cell having the above structure is as follows. (1) For example, a silicon oxide film 6 is formed on the back surface 1a of a p-type semiconductor substrate 1 by thermal oxidation or the like. (2) An n-type diffusion layer 2 is formed on a semiconductor substrate 1 by a gas phase diffusion method, a coating diffusion method or an ion implantation method,
An n-junction is formed. (3) A mask is formed on the back surface 1a of the semiconductor substrate 1 so that a predetermined region is opened, and a window of the oxide film 6 is opened by photoetching. (4) The surface electrode 3 is formed in a strip shape on the surface of the semiconductor substrate 1 by vapor deposition of silver or the like. (5) The periphery of the disc-shaped semiconductor substrate 1 is cut by a dicing saw to make the semiconductor substrate 1 rectangular. (6) A back electrode 5 is formed on the back surface 1a of the semiconductor substrate 1 by vapor deposition of aluminum, silver, or the like so as to correspond to individual solar cells. (7) A material such as titanium dioxide is deposited on the entire surface of the semiconductor substrate 1 to form an antireflection film 4. (8) The semiconductor substrate 1 is cut along a dicing line L by a dicing saw and divided into solar cells.

[0006]

In the process of manufacturing a solar cell, dicing is usually performed to cut out a plurality of cells from the semiconductor substrate 1. In a general dicing method, as shown in FIGS. 7 and 8, a fixing adhesive tape 9 is attached to a frame 8 to be transported by a handling device or a transport device. An opening 10 larger than the semiconductor substrate 1 is formed in the frame 8, and the back surface 1 a of the semiconductor substrate 1 is attached and fixed on the adhesive tape 9 through the opening 10. Then, after the position of the dicing line L of the semiconductor substrate 1 is adjusted on the dicing table 11, the semiconductor substrate 1 is cut from the front side of the semiconductor substrate 1 by the diamond blade 12. In the drawings, surface electrodes and the like are omitted (hereinafter, referred to as “surface electrodes”).
Similar).

In the case of a normal solar cell, after cutting to a depth of about 1/2 to 2/3 of the thickness of the semiconductor substrate 1,
In many cases, a method of dividing the element (half die) is used. However, in the case of a solar cell having a thickness of 100 μm or less, the substrate 1 is thin when a half die is used.
In many cases, the cell is broken at the time of cell division, which lowers the yield. For this reason, in the case of a thin solar cell, dicing is performed using a method (full dice) of cutting to the adhesive tape 9 for fixing the semiconductor substrate 1.

By the way, in the solar cell, the back electrode 5
In order to improve the moisture resistance of the semiconductor substrate 1, a step is formed on the back surface 1a of the semiconductor substrate 1 as shown in FIG. Therefore, as shown in FIG. 8, when the semiconductor substrate 1 is bonded to the adhesive tape 9, the semiconductor substrate 1 does not contact the adhesive tape 9 between the adjacent back electrodes 5, and a gap 13 is generated. And when dividing into cells by dicing,
A portion between the adjacent back electrodes 5, that is, a portion where the semiconductor substrate 1 is not bonded to the adhesive tape 9 is cut.

When dicing such a portion, FIG.
As shown in (1), since there is a gap 13 below the semiconductor substrate 1, the thin semiconductor substrate 1 is deformed by the stress from the diamond blade 12, and chips are easily generated on the back surface 1a. Further, in the case of a solar cell having a size of 100 μm or less, since a full dice is performed, chips are easily generated not only on the back surface 1a of the semiconductor substrate 1 but also on the front surface side. If chips are present, cracks tend to occur from that location,
In a later step, the photovoltaic cells are easily broken, which lowers the yield.

In the dicing method described in JP-A-6-132396, a hard member is printed on the back surface of a wafer as a work. An adhesive tape is attached to the frame, an adhesive-attached rubber plate is attached thereto, and the wafer and the adhesive-attached rubber plate are fixed to each other with a hard member interposed therebetween. This reduces the generation of chips when the wafer is cut by the dicing saw. However, for a workpiece to be cut, a wafer having a flat back surface is targeted, and for a work in which an electrode is formed on the back surface and a step is generated, the existence of a gap has not yet been eliminated, and chips and burrs have not been removed. May occur.

In view of the above, it is an object of the present invention to provide a dicing method capable of preventing generation of chips and the like even when a semiconductor substrate having a step on a back surface is cut.

[0012]

Means for Solving the Problems According to the present invention, a work having a step on one surface side is cut off after the work is covered with a coating film on one surface side to eliminate the step. To divide the data into a plurality of devices. At this time, when fixing the work by adhering the one surface to the fixing member, first remove the step by covering one surface of the work with a coating film, and then fix the work to the fixing member. Cut from the surface side and divide into multiple devices.

After forming the coating film for eliminating the step of the work, dicing is performed by attaching the work to a fixing member such as a fixing tape or directly placing the work on a dicing table. Therefore, there is no gap between the workpiece and the fixing member or the dicing table, and by cutting a portion where there is no gap, the workpiece is not deformed even when stress is applied to the workpiece, and chips and burrs are not formed. Generation can be prevented.

Here, when the work is a semiconductor substrate of a solar battery cell, an electrode is laminated on one surface side to form a step, so that one surface is coated to eliminate the step due to the electrode on the semiconductor substrate. The semiconductor substrate is placed so that the covering film faces a fixing member such as an adhesive tape for fixing the semiconductor substrate, and the adjacent electrodes of the semiconductor substrate are cut to form a plurality of solar cells. Divide into cells.

The coating film is formed using a photoresist such as a mixture of a novolak resin and an organic solvent or a mixture of a cyclized rubber and an organic solvent that can be removed by a solvent. Since this coating film can be removed by a solvent, the post-process after dicing becomes easy.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a solar cell according to this embodiment will be described. The structure of the solar cell is the same as the conventional one shown in FIG. 3, and is manufactured by forming the front electrode 3 and the back electrode 5 on the semiconductor substrate 1 according to the manufacturing process flow shown in FIGS. However, in the present embodiment, the dicing method when the semiconductor substrate 1 is cut and divided into solar cells is different from the conventional dicing method. That is, as shown in FIG. 1, the back surface 1a is covered with the coating film 14 in order to eliminate a step due to the back surface electrode 5 on the semiconductor substrate 1.

As the coating film 14, for example, a mixture of a novolak resin and an organic solvent or a mixture of a cyclized rubber and an organic solvent, such as a photoresist, is used. The photoresist is soluble in an organic solvent such as acetone or a dedicated stripping solvent.

Then, such a photoresist is applied to the back surface 1a of the semiconductor substrate 1 by spin coating, screen printing, or the like, and cured to form a coating film 14. The entire back surface 1a of the semiconductor substrate 1 is covered with the coating film 14, and the gap 13 between the adjacent back electrodes 5 is filled, so that a step is eliminated.

Next, the semiconductor substrate 1 having no step on the back surface 1a is placed on the adhesive tape 9 attached to the frame 8 so that the back surface 1a is facing down, and the coating film 1 is formed.
The semiconductor substrate 1 is fixed to the pressure-sensitive adhesive tape 9 with the intermediary of the semiconductor substrate 1.

Then, the fixed semiconductor substrate 1 is cut along a dicing line L by a dicing saw,
Divide into multiple solar cells. By dipping the divided solar cells in an organic solvent or a stripping solvent, the coating film 14 is dissolved and can be easily removed from the semiconductor substrate 1. As described above, if a photoresist soluble in a solvent is used, the coating film 14 can be easily removed, and the adhesive tape 9 can be peeled off and the subsequent processing work can be reduced as in the related art.

Here, the dicing line L passes between the adjacent back electrodes 5 on the semiconductor substrate 1;
As shown in (1), even if stress is applied from the diamond blade 12 of the dicing saw, the semiconductor substrate 1 is not deformed because there is no gap 13 between the semiconductor substrate 1 and the adhesive tape 9. Therefore, it is not necessary to cut the semiconductor substrate 1 at a position where the semiconductor substrate 1 is not adhered to the adhesive tape 9, so that the number of chips can be significantly reduced. In addition, even if the full dicing is performed, the portion without the back electrode 5 is cut, so that no burrs are generated.

Therefore, the generation of chips can be prevented, so that the photovoltaic cells are less likely to be cracked in a later step, the yield can be improved, and cracks generated from the chips are eliminated, and the reliability of the photovoltaic cells is reduced. , Quality can also be improved.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made to the above-described embodiment within the scope of the present invention. For example, the coating film may be formed with a resin other than the above-described photoresist. Furthermore, the method of fixing the semiconductor substrate is as follows.
Instead of using an adhesive tape, an adhesive may be applied on the coating film and adhered to a support plate such as rubber.

Alternatively, the coating film may be left as it is without being removed and used as a protective film. This makes it unnecessary to remove the coating film,
It can also protect solar cells. In this case, a polyimide resin or the like may be used as the coating film.

The dicing method of the present invention is not limited to manufacturing a solar cell, but also fixing a work such as ceramics or glass having irregularities on its surface to a fixing member, or mounting the work directly on a dicing table. It can also be used in the case of placing and dicing, and there is no gap between the workpiece and the workpiece, which is very effective in preventing chips at the time of cutting.

[0026]

As is clear from the above description, according to the present invention, when a work having a step on one side is covered with a coating film on one side of the work to eliminate the step, the work is fixed when the work is fixed. Since there is no gap due to the resulting step, even a thin work is not deformed at the time of cutting, and the generation of chips and burrs can be prevented. Therefore,
The work is less likely to be cracked in a later process, and the yield can be improved. In addition, cracks generated from the chip are eliminated, and a highly reliable and high quality device can be provided.

Here, when a semiconductor substrate for a solar cell is used as a work, a step due to the electrode is formed on one side of the work. Since the step can be cut without the step, the divided solar cell can be cut. No chips or the like are generated, the yield is increased, and the manufacturing cost can be reduced. Moreover,
Cracks caused by the chips can be prevented, and the reliability of the solar cell can be improved.

Then, the coating film is formed using a photoresist such as a mixture of a novolak resin and an organic solvent or a mixture of a cyclized rubber and an organic solvent which can be removed by a solvent. Can be done. Therefore, if the coating film is removed after the dicing while also performing the cleaning, the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a state in which a semiconductor substrate to be diced according to an embodiment of the present invention is fixed.

FIG. 2 is a schematic cross-sectional view showing a semiconductor substrate during dicing.

FIG. 3 is a cross-sectional view of a solar cell.

FIG. 4 is an enlarged sectional view of a back electrode.

FIG. 5 is a cross-sectional view and a plan view showing a flow of a manufacturing process of a solar cell.

FIG. 6 is a cross-sectional view and a plan view illustrating a flow of a manufacturing process of a solar cell.

FIG. 7 is a schematic cross-sectional view showing a state in which a conventional semiconductor substrate for dicing is fixed.

FIG. 8 is a schematic sectional view showing a conventional semiconductor substrate before dicing.

FIG. 9 is a schematic sectional view showing a conventional semiconductor substrate during dicing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Diffusion layer 3 Front electrode 4 Antireflection film 5 Back electrode 6 Silicon oxide film 8 Frame 9 Adhesive tape 12 Diamond blade 14 Coating film

Claims (6)

[Claims] 1. For a work having a step on one side,
A dicing method, wherein the one side of the work is covered with a coating film to eliminate the step, and then the work is cut and divided into a plurality of devices. 2. For a work having a step on one side,
The one surface side is adhered to a fixing member to fix the work,
In the dicing method in which the work is cut from the other surface side opposite to the one surface side and divided into a plurality of devices, the work is fixed to the fixing member after covering the one surface side with a coating film to eliminate the step. And dicing the workpiece. 3. When a solar cell is manufactured by cutting a semiconductor substrate having electrodes laminated on one surface side, the one surface side is covered with a coating film to eliminate a step due to the electrodes on the semiconductor substrate. Placing the semiconductor substrate so that the coating film faces a fixing member for fixing the semiconductor substrate, and cutting between adjacent electrodes of the semiconductor substrate to divide the plurality of solar cells. Dicing method characterized by the following. 4. The dicing method according to claim 1, wherein the coating film is formed using a photoresist. 5. The dicing method according to claim 4, wherein a mixture of a novolak resin removable by a solvent and an organic solvent is used as the photoresist. 6. The dicing method according to claim 4, wherein a mixture of a cyclized rubber removable by a solvent and an organic solvent is used as the photoresist.