JPH07130685A - Method of manufacturing semiconductor wafer - Google Patents

Abstract

PURPOSE:To prevent a metal film from peeling off from a die by a method wherein, prior to a formation of a metal film, a reverse surface of a semiconductor wafer is ground by a grindstone to chemically etch the ground surface. CONSTITUTION:A device 5 such as IC, FET is formed on a wafer 1 according to mask patterns. An adhering surface 6 being a reverse surface of the wafer 1 is ground by a grindstone of #1000 or less, and the ground surface is finished to an irregularity 2 with a mean radius of curvature 0.1mum or more and a maximum radius about 1mum. At this time, a modified layer 3 can be formed ranging over the depth several mum by a generation of a plastic deformation or a crack due to grinding near the ground surface. The modified layer 3 generated by a grinding process is removed by chemical etching. As etching liquid, a solution of a sulfuric acid system or an ammonia system is suitable. A metal film 4 is formed on the etched wafer surface by a vapor-depositing method. Here, an adhering surface between the wafer and the metal film in increased.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor die suitable for transferring and bonding the die.

[0002]

2. Description of the Related Art As shown in FIG. 4, a semiconductor die 1-1 having an IC or FET or the like formed on its surface is conveyed to an object to be mounted 46 such as a lead frame or a package to bond solder, gold, resin or the like. In the die bonding process of the integrated circuit mounted by the agent, the die fixed on the tape 41 is supplied and transferred by the collet 44 having the central hole 44-1 for adsorbing the die 1-1. By the way, by providing the metal film 4 on the back surface of the die 1-1, the adhesiveness between the die 1-1 and the mounted object 46 is enhanced.

[0003]

In order to convey the die 1-1 to the object to be mounted 46 by such a method, when the die 42 is pushed up from below the tape 41 by the needle 42 to be attracted to the collet 44, a metal film is formed. 4 may peel from the die 1-1. In such a case, there is a problem in that the die and the object to be mounted are not sufficiently joined and the reliability is lowered. Therefore, it is an object of the present invention to provide a method for manufacturing a semiconductor die that solves the above problems.

[0004]

A method for manufacturing a semiconductor wafer according to the present invention is a method for manufacturing a semiconductor wafer in which various semiconductor devices are formed on the front surface of a semiconductor wafer attached to a dicing tape and a metal film is formed on the rear surface thereof. In the method, a step of grinding the back surface of the semiconductor wafer with a grindstone and a step of chemically etching the ground surface are added prior to forming the metal film.

In the above method, the average radius of curvature of the back surface of the semiconductor wafer is less than 0.
Grinding to a surface having an unevenness of 1 μm or more and a maximum radius of about 1 μm, removing the ground surface by about 5 μm with a sulfuric acid-based etching solution or an ammonia-based etching solution, and depositing 100
It is preferable to form a metal film of 0 Å or more, or to form a thin film of Ti on the etched surface and then form a thin film of Au on it.

[0006]

According to the above construction, the method according to the present invention is characterized in that the back surface of the semiconductor wafer has an average radius of curvature of 0.1 μm or more,
Since the unevenness having the maximum radius of about 1 μm is provided and the metal film is applied on the unevenness, the adhesion surface between the wafer and the metal film becomes large, and the surface becomes rough, so that the adhesive force is increased and the reliability of die bonding is improved. Further, since the deteriorated layer generated by processing is removed, the shear strength does not deteriorate.

If the uneven surface is made finer, the effect of the adhesive force is reduced, which is not preferable. A method using chemical etching is suitable for removing the deteriorated layer in which processing strain has occurred. Since the average radius of curvature of the unevenness is 0.1 μm or more, the thickness thereof must be 0.1 μm or more to cover the entire surface with the metal film. Since Ti has a good adhesiveness with the wafer and Au has a good adhesiveness with the bonding agent such as AuSn or AuSi used for die-bonding, it is possible to obtain T on the etched wafer surface.
It is preferable to apply a thin film of i and a thin film of Au on it in order to increase mutual adhesiveness.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is a sectional view showing a semiconductor wafer formed by the manufacturing method of this embodiment. FIG (a) the IC in the size of 2mm _b ~10mm _b on the GaAs wafer 1 of a diameter of 3 inches or 5 inches, the device 5 such as a FET formed in accordance with the master pattern, the back surface 6 original GaAs Is the state of.

In FIG. 1 (b), the adhering surface 6 of the GaAs wafer 1 is ground with a grindstone of # 1000 or less, and the ground surface is finished to have irregularities 2 having an average radius of curvature of 0.1 μm or more and a maximum radius of about 1 μm. At this time, an altered layer 3 is formed in the vicinity of the ground surface over a depth of several μm due to plastic deformation or cracking generated by grinding.

FIG. 2 (a) is a sectional view showing the structure of the grinding apparatus, and FIG. 2 (b) is a plan view showing that the wafer 1 attracted by the chuck 23 rotating in the direction of arrow 24 is in the direction of arrow 25. This is a disk-shaped grindstone 21 that moves in the vertical direction 26 while rotating, and is a wafer rotation down-feed type device that grinds the back surface 6 of the wafer 1 by this grindstone 21. During grinding, heat is generated and waste powder is generated, so cooling water is sprayed. When grinding is completed, a drying gas such as N ₂ gas is sprayed to remove water.

FIG. 1 (c) shows an altered layer 3 formed by grinding.
The figure shows a state in which is removed by chemical etching. If there is a deteriorated layer 3 that causes processing strain, it is easy to crack from this part,
This is because the shear strength deteriorates. The altered layer 3 is removed by immersing it in an etching solution. Etching solution, sulfuric acid system (H ₂
SO ₄ + H ₂ O ₂ + H ₂ O) or ammonia system (NH
A solution of ₄ OH + H ₂ O ₂ + H ₂ O) is suitable. When these solutions are used, the etching rate is about 1 μm / min.
The deteriorated layer can be removed in about 5 minutes.

FIG. 1D shows a state in which a metal film 4 is formed on the etched wafer surface by a vapor deposition method. FIG. 3 is an explanatory diagram of a method of forming a thin film by a vacuum vapor deposition method. A holder 33 that holds the semiconductor wafer 1, a shutter 32 that opens and closes a passage of metal vapor, and a crucible 34 are installed in a vacuum container 31, and exhaust is performed by a rotary pump and an oil diffusion pump (not shown). Au powder gr was put in the crucible 34, the GaAs wafer 1 having a diameter of 3 inches was placed in the holder 33, and the inside of the container 31 was 1 × 10 ⁻⁶ T.
Exhausted to orr. Shutter 32 is open crucible 3
The heater built in No. 4 was energized and heated to evaporate Au.
Since the surface to be vapor-deposited has irregularities with an average radius of approximately 0.1 μm, the thickness of the film 4 must be 1000 Å or more to cover the entire surface with gold.

FIG. 1E shows a Ti metal film 4-1 on the etched wafer surface, and an Au metal film 4-2 thereon.
It shows the state of applying. This is because Ti has good adhesiveness to the wafer, and Au has good adhesiveness to the bonding agent such as AuSn or AuSi used for die bonding.

[0015]

As described above, according to the present invention,
Since the back surface of the semiconductor wafer has unevenness with an average radius of curvature of 0.1 μm or more and a maximum radius of about 1 μm, and a metal film is applied on it, the bonding surface between the wafer and the metal film becomes large, resulting in rough skin-like bonding. The force is increased and the reliability of die bonding is improved. Further, since the deteriorated layer generated by processing is removed, the shear strength does not deteriorate.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a semiconductor wafer in each step, which is formed by a manufacturing method of this embodiment.

FIG. 2 is a cross-sectional view (a) and a plan view (b) showing a configuration of a grinding device applied to the manufacturing method of the present embodiment.

FIG. 3 is an explanatory diagram of a vacuum vapor deposition method applied to the manufacturing method of the present embodiment.

FIG. 4 is a schematic diagram showing a configuration of a conventional die bonding method.

[Explanation of symbols]

 1: Semiconductor wafer 1-1: Die 2: Concavo-convex 3: Altered layer 4, 4 ': Metal film 5: Semiconductor device 6: Back surface 21: Grindstone 22: Grindstone stand 23: Chuck 24, 25, 26: Arrow 31: Vacuum Container 32: Shutter 33: Holder 34: Crucible 41: Dicing tape 44: Collet 46: Mounted object

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 21/52 C 21/301

Claims (5)

[Claims] 1. A method of manufacturing a semiconductor wafer, wherein various semiconductor devices are formed on the front surface of a semiconductor wafer attached to a dicing tape, and a metal film is formed on the back surface thereof. Prior to forming the metal film, the semiconductor wafer is formed. And a step of chemically etching the ground surface of the semiconductor wafer. 2. The back surface of a semiconductor wafer is ground to a surface having irregularities with an average radius of curvature of 0.1 μm or more and a maximum radius of about 1 μm by using a grindstone of # 1000 or less. Manufacturing method of semiconductor wafer. 3. The method for producing a semiconductor wafer according to claim 1, wherein the ground surface is removed by about 5 μm with a sulfuric acid-based etching solution or an ammonia-based etching solution. 4. The method of manufacturing a semiconductor wafer according to claim 1, wherein a metal film having a thickness of 1000 Å or more is formed on the etched surface by a vapor deposition method. 5. The method for manufacturing a semiconductor wafer according to claim 1, wherein a thin film of Ti is formed on the etched surface, and a thin film of Au is formed thereon.