JP3708342B2 - Method for manufacturing light-emitting diode element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a light-emitting diode element, and more particularly to an improvement of an etching method after dicing into chips.
[0002]
[Prior art]
Manufacture of light-emitting diode devices using various compound semiconductors is operated in units of wafers in which n-type and p-type compound semiconductors are stacked on the surface of the substrate and electrodes are formed on the substrate or the stacked surface of the compound semiconductor. . After the electrodes are formed, the junction between the p-type layer and the n-type layer is separated into a chip, and an assembly for mounting the chip on a lead frame or a printed board is obtained.
[0003]
In the process of forming a chip from a wafer, dicing using a dicer is generally used. In this dicing, the surface of the wafer is cut by a dicing blade that moves on the wafer while rotating, and the side surface of the chip to be formed is distorted by friction and shearing by the dicing blade. This distortion causes a decrease in the reliability of the element, and in particular, causes a short circuit near the junction between the p-type layer and the n-type layer, resulting in poor light emission characteristics.
[0004]
In order to prevent the influence of the dicing on the chip, it is effective to remove the strained layer by chemically etching the cut surface of the chip including the pn junction after the dicing is finished. The removal of the strained layer by etching is described, for example, in JP-A-3-142953.
[0005]
In the method described in this publication, a wafer is attached to an ultraviolet curable adhesive sheet, and a pn junction is separated by dicing, leaving a part of the wafer, and after removing the wafer from the adhesive sheet, a strained layer is formed by etching. The chip is further separated by scribing and breaking.
[0006]
However, since dicing is performed while leaving a part of the thickness of the wafer, dicing grooves around the chip to be formed run in a lattice pattern on the entire surface of the wafer. For this reason, since the dicing groove portion has only a very thin thickness and stress tends to concentrate, the mechanical strength of the entire wafer is significantly reduced. Therefore, when removing or etching the wafer from the adhesive sheet, the wafer is easily broken, and the chip removal rate from the wafer is significantly reduced. In addition, chip cracking or chipping may occur in the scribing or breaking process.
[0007]
On the other hand, if it is what is called a full cut construction method which isolate | separates by dicing, without leaving a part of thickness of the wafer affixed on the adhesive sheet, generation | occurrence | production of the crack of a chip | tip, a chip, etc. is suppressed. However, since each chip has already been completely separated before the etching process, after the dicing process, the chip alone is handled from the etching process to the process of mounting on the lead frame or the like, the so-called dice bonding process. As a result, the process becomes complicated.
[0008]
[Problems to be solved by the invention]
Therefore, if the full cut is performed in a state of being attached to the adhesive sheet, the chip can be handled in units of the adhesive sheet from the dicing process to the die bonding process, so that the process is not complicated.
[0009]
However, etching of the cut surface of the chip must also be performed in a state of being attached to the adhesive sheet. In this case, the pressure-sensitive adhesive of the pressure-sensitive adhesive sheet is damaged by the etching solution, or water used for cleaning the etching solution penetrates the pressure-sensitive adhesive. Therefore, the adhesive strength of the pressure-sensitive adhesive sheet is reduced, and for example, chips are detached from the pressure-sensitive adhesive sheet during etching, and the chip acquisition rate from the wafer is significantly reduced.
[0010]
On the other hand, electrode pads for wire bonding formed on the surface of the chip by metal vapor deposition are generally Au or Al. When the electrode pad is made of Au, no damage is caused even if the etching solution is phosphoric acid or the like. However, in the case of Al, the electrode pad is dissolved and the deposited electrode pad is lost. For this reason, it is necessary to coat with a protective film before etching if it reacts with the etching solution, such as Al, and a step for removing this film is added after the etching. .
[0011]
As described above, in the conventional manufacturing method, the chip falls from the adhesive sheet due to swelling of the adhesive by the etching solution, and the recovery rate is reduced. Therefore, it is necessary to add a process for forming and removing the metal, which has a great influence on the product yield.
[0012]
The problem to be solved in the present invention is to provide a method for manufacturing a light-emitting diode element that can improve the chip acquisition rate from a wafer without the occurrence of chip cracking or chipping, and that does not require a step for protecting an electrode. .
[0013]
[Means for Solving the Problems]
The present invention relates to a method of manufacturing a light emitting diode device for obtaining a chip by dicing a wafer in which a wire bonding electrode pattern is formed on at least the upper surface of a laminated compound semiconductor, and bonding a primary adhesive sheet to the back surface of the wafer And cutting the entire cross section of the wafer and the pressure-sensitive adhesive layer of the primary pressure-sensitive adhesive sheet and dicing the wafer into chips, and forming all the chips held on the primary pressure-sensitive adhesive sheet into a secondary pressure-sensitive adhesive sheet. A step of transferring and immersing the electrode in an ultraviolet curable pressure-sensitive adhesive laminated on a base material of the secondary pressure-sensitive adhesive sheet, and simultaneously bonding the chip to the secondary pressure-sensitive adhesive sheet; and the primary pressure-sensitive adhesive sheet after the transfer Peeling and subsequently irradiating the secondary adhesive sheet with ultraviolet rays to cure the ultraviolet curable adhesive, and the secondary adhesive Characterized in that it comprises a step of removing the strained layer remaining cut surface of the chip by dipping the dicing in an etching bath while laminating the ultraviolet-curable pressure-sensitive adhesive and the chip to a substrate over bets.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The invention according to claim 1 is a method of manufacturing a light emitting diode device for obtaining a chip by dicing a wafer in which a wire bonding electrode pattern is formed on at least the upper surface of a laminated compound semiconductor. After pasting the adhesive sheet, cutting the entire cross section of the wafer and the adhesive layer of the primary adhesive sheet, dicing and separating the wafer into chips, and all the chips held by the primary adhesive sheet A step of transferring the electrode to a secondary pressure-sensitive adhesive sheet and immersing the electrode in an ultraviolet curable pressure-sensitive adhesive laminated on a substrate of the secondary pressure-sensitive adhesive sheet, and simultaneously bonding the chip to the secondary pressure-sensitive adhesive sheet; Peeling the primary pressure-sensitive adhesive sheet and subsequently irradiating the secondary pressure-sensitive adhesive sheet with ultraviolet rays to cure the ultraviolet curable pressure-sensitive adhesive; and A step of removing a strained layer remaining on the cut surface of the chip by immersing in an etching bath in a state where the ultraviolet curable adhesive and the chip are laminated on the base material of the secondary adhesive sheet. This is a manufacturing method that prevents chip chipping from the adhesive sheet even in the etching process without cracking or chipping of the chip, and the secondary adhesive sheet also serves as a protective film for electrodes that do not have etching resistance. The process of forming the protective film and removing the protective film is unnecessary, and the wafer after dicing can be easily handled.
[0015]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing a wafer dicing step in a method for manufacturing a light emitting diode device according to an embodiment of the present invention.
[0016]
In FIG. 1, the dicer used in the present invention is a general one composed of a dicing table 20 and a dicing frame 21 and a dicing blade 22 arranged at the upper end thereof. As described in the prior art, the dicing blade 22 moves in a direction orthogonal to the drawing while rotating, pierces the wafer, and cuts by shearing.
[0017]
The wafer 1 set on the dicing table 20 is obtained by completing the process of forming the p-type and n-type compound semiconductors on the surface of the crystal substrate and forming the p-side and n-side electrodes. A primary adhesive sheet 2 is attached in advance to the bottom surface of 1. The primary pressure-sensitive adhesive sheet 2 is composed of a thin film-like substrate 2a and a pressure-sensitive adhesive 2b laminated thereon.
[0018]
The wafer 1 uses, for example, a GaP, GaAsP, or AlGaAs compound semiconductor in the illustrated example, a p-side electrode 1a formed by metal deposition of Al on the upper surface, and Au on the bottom surface of the lower substrate. It shows as what formed the n side electrode 1b formed by vapor deposition. The p-side electrode 1a has such a size that a wire can be ball-bonded after being mounted on a lead frame or a printed wiring board.
[0019]
The wafer 1 to which the primary adhesive sheet 2 has been attached is fixed to the upper surface of the dicing table 20 using the vacuum as shown in FIG. 1 and is diced by the dicing blade 22. In this dicing, the adhesive 2b is cut from the entire cross section of the wafer 1 so that the base material 2a is not cut. As a result, the chips 3 having a uniform size by the laminate of the adhesive 2b and the wafer 1 are separated on the base material 2a of the primary adhesive sheet 2 in a pellet form. This eliminates the need for a scribe process or break process after dicing, and eliminates the occurrence of cracks or chipping of the chip 3 that occurred during the scribe process or break process.
[0020]
After dicing, the wafer 1 is removed from the dicing table 20 together with the primary pressure-sensitive adhesive sheet 2 and turned upside down and transferred onto the ultraviolet curable secondary pressure-sensitive adhesive sheet 4 as shown in FIG. Peel off. The secondary pressure-sensitive adhesive sheet 4 is obtained by applying an ultraviolet curable pressure-sensitive adhesive 4b to the surface of the substrate 4a. As the substrate 4a, resins such as vinyl chloride, polyolefin, and polyester can be used, but polyolefin or polyester is preferable in consideration of heating in an etching process described later. The ultraviolet curable pressure-sensitive adhesive 4b usually has an adhesive force, but has a characteristic that it is cured when exposed to ultraviolet rays and its adhesiveness deteriorates.
[0021]
In the transfer process of the wafer 1 and the primary adhesive sheet 2 divided into the chips 3 to the secondary adhesive sheet 4, the entire p-side electrode 1 a is submerged in the ultraviolet curable adhesive 4 b, The surface on which the side electrode 1a is formed is handled in contact with the ultraviolet curable adhesive 4b. By this transfer, the lower end surface of the chip 3 and the p-side electrode 1a in FIG. 2 are bonded and fixed to the secondary adhesive sheet 4, and then the primary adhesive sheet 2 is peeled off as shown. As a result, the adhesive 2b of the primary adhesive sheet 2 is also separated from the chip 3 at the same time, and remains on the secondary adhesive sheet 4 in a posture in which the chip 3 is turned upside down.
[0022]
When the transfer of the chip 3 is completed, as shown in FIG. 3, ultraviolet rays are irradiated from the back side of the secondary adhesive sheet 4, that is, the surface opposite to the mounting surface of the chip 3 with an ultraviolet lamp 5 using, for example, a metal halide lamp. Thereby, the ultraviolet curable adhesive 4b is cured.
[0023]
For example, the ultraviolet curable pressure-sensitive adhesive 4b can be cured by irradiating at a position (50 mW / cm ² ) 10 cm away from a 60 W / cm high-pressure mercury lamp for 6 seconds to give an irradiation amount of 300 mJ / cm ² .
[0024]
Next, as shown in FIG. 4, the cured ultraviolet curable pressure-sensitive adhesive 4 b supported by the base material 4 a and the chip 3 laminated thereon are immersed in the etching solution 7 in the etching tank 6.
[0025]
The etching solution 7 is prepared by mixing phosphoric acid and hydrogen peroxide (H ₃ PO ₄ + H ₂ O ₂ ) and heating to a temperature of 30 ° C. to 60 ° C. Then, the surface of the chip 3 divided into pellets in 10 to 20 minutes is etched by a thickness of several μm, thereby removing the strained layer on the cut surface generated during dicing.
[0026]
Here, before the etching, the ultraviolet curable adhesive 4b of the secondary pressure-sensitive adhesive sheet 4 causes a chemical reaction by irradiation with ultraviolet rays, and becomes a firm film. The ultraviolet curable adhesive 4 b loses its adhesive force itself when it is exposed to ultraviolet rays, but the chip 3 is held without being peeled from the secondary adhesive sheet 4. That is, even if the ultraviolet curable adhesive 4b is cured and loses its adhesive strength, the interface is in a vacuum state, and the chip 3 is adsorbed by the same mechanism as in the mirror surface bonding. For example, unless a large external force is instantaneously applied. The secondary adhesive sheet 4 does not fall off.
[0027]
By curing the ultraviolet curable pressure-sensitive adhesive 4b before etching in this way, the etching liquid does not enter the adhesive surface between the chip 3 and the secondary pressure-sensitive adhesive sheet 4 separated from the wafer state. Further, since the etching solution does not penetrate into the ultraviolet curable adhesive 4b, the ultraviolet curable adhesive 4b itself does not swell. Therefore, even after the etching is completed and pulled up from the etching tank 6, the chip 3 can be stably held integrally with the secondary adhesive sheet 4, and the chip 3 does not fall off. That is, conventionally, when etching was performed with a chip attached to an adhesive sheet, the chip could not be removed from the adhesive sheet. However, by using the manufacturing method of the present invention, the chip 3 from one wafer 1 can be removed. The acquisition rate can be increased.
[0028]
Even if Al is used as the p-side electrode 1a, the p-side electrode 1a is entirely submerged in the ultraviolet curable pressure-sensitive adhesive 4b, so that the etching solution 7 is not melted. That is, as described above, the ultraviolet curable pressure-sensitive adhesive 4b is cured by irradiating ultraviolet rays before being immersed in the etching solution 7, so that there is no swelling of the etching solution 7 in the inside thereof, and the surface of the p-side electrode 1a. There is no penetration of the etching solution 7 into the interface. Therefore, the Al p-side electrode 1a is protected by using the ultraviolet curable adhesive 4b as a protective film, and a process of forming a protective film before etching and removing the protective film after etching is unnecessary.
[0029]
Although the n-side electrode 1b is immersed in the etching solution 7, there is no need to form a protective film because no melting damage occurs when the material is Au. For example, in a blue light emitting diode element using a GaN-based compound semiconductor in which p-side and n-side electrodes are formed on the same surface opposite to the crystal substrate, these p-side and n-side electrodes are bonded to an ultraviolet curable adhesive. Similarly, by introducing the material into the agent 4b, melt damage due to the etching solution 7 can be prevented. Therefore, even when the p-side and n-side electrodes are made of Al or a combination of Al and Au, the formation of the protective film and the removal step after the etching are unnecessary.
[0030]
After the above etching, the separated chip 3 held on the secondary adhesive sheet 4 is sent to a post-cleaning and drying process, and mounted on a lead frame or a printed circuit board and assembled in a die bonding process. .
[0031]
As the etching solution 7, in addition to a mixture of phosphoric acid and hydrogen peroxide, a similar effect can be obtained by using hydrochloric acid, sulfuric acid, ammonia, or hydrofluoric acid.
[0032]
【The invention's effect】
In the present invention, the scribe and break processes after dicing are not necessary, and chip breakage and chipping frequently occurred in these processes can be prevented, and the chip does not fall off from the adhesive sheet even in the etching process. The chip acquisition rate from is improved. In addition, even when a metal electrode having no etching resistance is used, the secondary adhesive sheet can be used as the protective film, so that a process for forming and removing the protective film is unnecessary, and productivity and product yield are improved. Is also planned.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a wafer dicing step in a method for manufacturing a light-emitting diode device according to an embodiment of the present invention. FIG. FIG. 3 is a schematic diagram showing a process of applying ultraviolet rays to the secondary adhesive sheet after chip transfer. FIG. 4 is an immersion bath etched after curing the ultraviolet curable adhesive of the secondary adhesive sheet. Schematic showing the process to be performed 【Explanation of symbols】
DESCRIPTION OF SYMBOLS 1 Wafer 1a P side electrode 1b N side electrode 2 Primary adhesive sheet 2a Base material 2b Adhesive 3 Chip 4 Secondary adhesive sheet 4a Base 4b UV curable adhesive 5 UV lamp 6 Etching tank 7 Etching solution 20 Dicing table 21 Dicing Frame 22 Dicing blade

Claims (1)

A method of manufacturing a light emitting diode device for obtaining a chip by dicing a wafer in which an electrode pattern for wire bonding is formed on at least an upper surface of a laminated compound semiconductor,
Cutting the entire cross section of the wafer and the pressure-sensitive adhesive layer of the primary pressure-sensitive adhesive sheet after pasting the primary pressure-sensitive adhesive sheet on the back surface of the wafer, and separating the wafer into chips; and
All the chips held on the primary pressure-sensitive adhesive sheet are transferred to a secondary pressure-sensitive adhesive sheet, and the electrodes are immersed in an ultraviolet curable pressure-sensitive adhesive laminated on the base material of the secondary pressure-sensitive adhesive sheet. Adhering to the adhesive sheet;
Peeling the primary pressure-sensitive adhesive sheet after the transfer, and subsequently irradiating the secondary pressure-sensitive adhesive sheet with ultraviolet rays to cure the ultraviolet curable pressure-sensitive adhesive;
A step of removing a strained layer remaining on the cut surface of the chip by immersing in an etching bath in a state where the ultraviolet curable adhesive and the chip are laminated on the base material of the secondary adhesive sheet. Production method.

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