JPH0927498A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the adhering position and the quantity of adhesion of solder with high precision by causing only a specified part of the metal electrode surface of a semiconductor wafer to have tackiness, and causing solder powder to adhere. SOLUTION: A wafer is dipped into a 2-dodesil imidazole aqueous solution, washed by water, and dried, and tackiness is given to the surfaces of Cu electrodes 5a, 5b. Following this, eutectic solder powder is dusted. After that, solder is heated and fixed to the electrode surfaces. And a minute quantity of solder powder is removed by a brush, and a water soluble flux is applied. After that, they are put into a reflow furnace to melt the solder powder, and fine solder electrode patterns 6a, 6b are formed on the surfaces of the Cu electrodes 5a, 5b. Next, the wafer is stuck to an adhesive sheet, and made into light-emitting semiconductor devices 20 by cutting it with a dicing saw. After the separation, this light-emitting semiconductor device 20 is die-bonded so that the electrodes of the conductive circuit 10 of a circuit board 9 may touch the solder electrodes 6a, 6b of the light-emitting semiconductor device 20, and is heated and melted in the reflow furnace and is joined to the circuit board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a solder electrode.

[0002]

2. Description of the Related Art As a method for mounting a semiconductor device on a lead frame or a circuit board, an adhesive, a conductive adhesive (for example, Ag paste) is used, or a low melting point metal such as AuSn is formed as a back electrode, It is general that the semiconductor device is fixed by heating and melting (JP-A-2-260671), and then wiring is performed by a wire bonding method using gold, aluminum or the like. On the other hand, in recent years, a method of joining a semiconductor device and a circuit board (for example, a printed board) using solder has been developed as a method having higher reliability than the wire bonding method, a simple process, and excellent productivity.
This method forms solder bumps on the electrodes formed on the semiconductor device. The semiconductor device is installed on the circuit board so that the solder bumps are in contact with the wiring electrodes whose surface is covered with solder formed on the circuit board. Then, about 20
A heat treatment (reflow process) is performed at about 0 ° C. and soldering is performed to electrically and physically join the semiconductor and the circuit board.

In these solder bumps, a solder layer is formed on the surface of a base metal electrode (for example, Au / Cu / Cr structure) formed on the semiconductor surface by using a vapor deposition method, a dip method, or the like, and heat treatment is performed. Go and melt the solder once,
A method for obtaining a solder bump is known (Japanese Patent Laid-Open No. 2-2
78743, JP-A-61-1141155). These methods can form a pattern having an electrode pitch of 0.2 mm and an electrode diameter of about 0.1 mm, but it is difficult to form a finer pattern. The plating method has relatively good pattern accuracy, but has the drawbacks that the solder layer thickness cannot be increased, the layer thickness varies, and the composition shifts. Further, the electroplating method requires electrical conduction and cannot be applied to island-shaped electrodes. Therefore, the semiconductor device such as an integrated circuit (LSI) has a relatively large chip size and is applied to a semiconductor device in which an electrode interval can be made large. The wire bonding method described above is generally used for a magnetoelectric conversion element such as a light emitting diode or a Hall element having a small chip size. The reason for this is that in a semiconductor device having a small chip size, in the wafer state before being separated into chips, the distance between the electrode in one element and the electrode of an adjacent element or the electrode area is small, so that the solder electrode formation as described above is performed. This is because the method often causes short circuits such as solder bridges and defective joints.

Further, if the electrode interval is increased, the required chip area is increased, the number of elements obtained from one wafer is reduced, and the productivity is remarkably reduced. Further, the method of separating solder into chips and expanding the chip interval, that is, the method of forming the solder electrode after expanding the electrode interval is very difficult to handle because the chips are handled individually, and has not been put into practical use.

[0005]

In the conventional wire bonding method, ultrasonic waves and mechanical pressure are applied at the time of bonding, which may damage and deteriorate the semiconductor, and may cause peeling on the bonding surface and wire breakage. It is not very popular. On the other hand, in the conventional solder electrode manufacturing method, when the electrode size is reduced and the electrode interval is reduced, the solder layer thickness distribution becomes large, or short-circuiting (bridge) between adjacent electrodes occurs. The layer thickness distribution of the solder has a problem of increasing the variation in the bonding strength. In the case of manufacturing a semiconductor device having a small chip size in the conventional technique, it is difficult to form a solder electrode in a wafer state, and it is necessary to form the solder electrode after separating the elements. In this case, a process for protecting the side surface of the chip is required, which complicates the process, makes it difficult to handle the chip, and significantly reduces the productivity.

These problems are caused by the fact that the electrodes absorb light and therefore it is necessary to reduce the electrode area as much as possible in order to improve the characteristics. Therefore, there are four electrodes in a small chip such as a light emitting diode and a light receiving element. This is particularly important in semiconductor devices such as magnetoelectric conversion elements such as Hall elements having a narrow electrode interval. An object of the present invention is to manufacture a semiconductor device having a solder electrode having high reliability and high productivity even in an element having a small chip size with good reproducibility.

[0007]

In order to solve the above-mentioned problems, the inventors of the present invention have conducted extensive studies and as a result, have made it possible to selectively attach solder powder only to the surface of a fine metal electrode pattern formed on a semiconductor wafer. The present invention has been achieved with a focus on obtaining. According to the present invention, a semiconductor wafer on which a plurality of elements are formed is processed as it is without separating into individual elements to form solder electrodes, and then separated into individual elements. The semiconductor used in the present invention can be applied to Si, Ge and compound semiconductors. Compound semiconductor is GaA
s, InP, GaP, GaAlAs, GaN, etc. III
II-VI group semiconductors such as -V group semiconductors and ZnSe can be used. As a semiconductor device, a light emitting diode, a laser diode, a light receiving element, or a hall element having a narrow electrode gap, whose electrode area greatly affects the characteristics, is most suitable.
It can also be applied to transistors, diode arrays, LSIs and the like.

The main body of the semiconductor device is a semiconductor single crystal wafer (eg, Si, GaAs, etc.) manufactured by a usual method.
In addition, a well-known ion implantation method or epitaxial growth method is used to form an active layer for generating a function, and then an electrode for ensuring electrical contact is formed. The metal electrode material that contacts the main functional surface of the semiconductor may be selected from materials suitable for the semiconductor. For example, known techniques such as those described in "Latest compound semiconductor handbook" (published by Science Forum Co., Ltd.) can be used. As the method for forming the metal electrode, known vapor deposition, sputtering method or the like can be used.
However, materials with poor wettability with solder (for example, Ti,
In the case of W) or a material that is eroded by solder (for example, Au), a solder base metal such as Cu or Ni that has good wettability with solder and has little solder erosion may be formed thereon. Further, when the solder base metal and the metal in contact with the semiconductor are alloyed and there is a problem in characteristics, a high melting point barrier metal layer (for example, Ti, Cr, or the like) is formed between the metal in contact with the semiconductor and the base electrode. W, Mo, etc.) may be formed. A known photolithography method may be used as a method for forming the pattern of the metal electrode. As the protective film formed on the semiconductor surface, a generally known material such as an inorganic film such as silicon oxide or silicon nitride, an organic film such as polyimide or an oxide film of a semiconductor may be used. In this way, a plurality of devices having metal electrodes are formed on the semiconductor wafer.

Next, the method of imparting tackiness to a specific portion of the surface of the metal electrode is not particularly limited as long as it is treated with a compound that acts on the surface metal to develop tackiness. Examples of the compound include a benzotriazole derivative, a naphthotriazole derivative, an imidazole derivative, a benzimidazole derivative, and a mercaptobenzone which exhibit strong adhesion to a Cu electrode disclosed in JP-A-7-30243. An aqueous solution containing a thiazole derivative, a benzothiazole fatty acid derivative, or the like is used. The concentration of the aqueous solution is adjusted to be acidic, preferably slightly acidic with a pH of about 3 to 5, and the concentration is preferably 0.05 to 20% by weight. Further, coexistence of about 100 to 1000 ppm of copper ions is preferable because the production efficiency such as production rate and production amount of the adhesive film is enhanced. As the method of treating the metal electrode, the aqueous solution prepared as described above is brought into contact with the exposed metal portion by means of a dipping method, a coating method, a spray method or the like. Even on the metal electrodes, unnecessary portions of the solder are covered with a resist film or the like so that the metal surface is not exposed. The processing temperature is preferably in the range of room temperature to about 60 ° C. The contact time is appropriately selected within the range of 5 seconds to 5 minutes. Next, if appropriately washed with a solvent and dried, tackiness is imparted only to the exposed metal portion. If the solder powder is sprinkled and adhered to the surface of the metal electrode to which tackiness has been imparted, and excess solder is blown off with pressurized air or removed by wet cleaning or the like, the solder powder remains only on a necessary portion of the surface of the metal electrode. The solder powder may be a commonly used eutectic solder, silver-containing solder, bismuth-containing solder, or the like. The particle size of the solder powder may be appropriately selected from 10 μm to several hundreds of μm depending on the intended solder layer thickness of the solder electrode. After that, the solder is heated and fixed on the electrode surface, a trace amount of the solder powder is removed, commercial flux is applied, and then the solder is melted by heating to form a solder electrode in which the solder is attached only to the metal electrode portion. When the electrode pattern is not fine, the heat fixing step may be omitted. next,
The wafer is cut by a normal dicing saw or a scribing method to be separated into individual elements. After the semiconductor element is separated, it is die-bonded to a circuit board or a lead frame and heated to melt and bond the solder.

[0010]

In the present invention, the adhesion position and the adhesion amount of the solder can be controlled with high accuracy by imparting the adhesiveness only to the predetermined portion of the metal electrode surface of the semiconductor wafer and adhering the solder powder.

[0011]

EXAMPLES The contents of the present invention will be specifically described below with reference to examples. (Embodiment 1) As an embodiment, an example in which a plurality of LED elements are formed on an epitaxial wafer for a GaAlAs light emitting diode will be shown. A part of the plan view of this wafer is shown in FIG.
1 shows a sectional structure taken along line AA ′ of FIG. The epitaxial wafer has a plane orientation (100) of p-type semi-insulating GaA.
On the s substrate, a Zn-doped p-type GaAlAs clad layer 4 was grown to a thickness of 5 μm by a liquid phase epitaxial method, and a Zn-doped p-type GaAlAs layer 2 was grown to a thickness of 1 μm as an active layer thereon, and Te-doped. N-type GaAlAs
The clad layer 3 was formed by growing it to a thickness of 150 μm.
The Al mixed crystal ratio of the active layer 2 was adjusted to Al _0.35 Ga _0.65 As so that the emission wavelength was 660 nm. The Al mixed crystal ratio of the p and n clad layers 3 and 4 is an Al mixed crystal ratio transparent to this emission wavelength.

Next, the p-type GaAs substrate was removed by etching with a known ammonia-hydrogen peroxide type etching solution. After that, on the surface of the p-type GaAlAs cladding layer 4,
The n-type electrode formation part, 70 μm × 150 μm, pitch 300 μm, and the part to be the dicing line were left, and the other parts were protected with a resist material by photolithography. Further, the n-type clad layer 3 on the back surface was also protected by a resist material. Then, the p-type GaAlAs cladding layer 4 in the n-type electrode forming portion and the dicing line portion was removed by etching with a phosphoric acid-hydrogen peroxide-based etching solution. Next, the p-type GaAlAs cladding layer 4
The surface of the substrate was protected with a resist material by photolithography except for the n-type electrode formation region having a size of 70 μm × 150 μm with a pitch of 300 μm. The wafer is set in a vacuum evaporation system and is made of AuGe / Ti / Cu (thickness is 1000Å / 1000Å / 6000Å) n
The mold electrode material was vacuum deposited. The resist was peeled off, and the n-type electrode pattern 5a was formed by the lift-off method. Again, the surface of the p-type GaAlAs cladding layer 4 was protected with a resist material by photolithography except for the p-type electrode regions of 70 μm × 150 μm at a pitch of 300 μm. p-type GaAl
A p-type electrode material made of AuBe / Ti / Cu (thickness: 1000Å / 1000Å / 6000Å) was vacuum-deposited on the surface of the As clad layer 4. The resist was peeled off, and the p-type electrode pattern 5b was formed by the lift-off method.
Next, alloying was performed for 5 minutes at 420 ° C. in a nitrogen atmosphere to form ohmic electrodes for both n-type and p-type. On top of that, a photosensitive polyimide resin 7 (PIMEL manufactured by Asahi Kasei Corporation)
A series and a glass transition point of 355 ° C.) were uniformly applied with a spin coater. A pattern was formed by photolithography so as to protect the regions other than the electrode regions 5a and 5b and the dicing street portion 8. To cure the resin, heat treatment was performed at 350 ° C. for 60 minutes in a nitrogen atmosphere. The film thickness of the polyimide resin was 2 μm.

Next, the wafer is immersed in an aqueous solution of 2-dodecyl imidazole (1 wt%) whose pH is adjusted to about 4 with acetic acid at 45 ° C. for 5 minutes, then washed with water and dried to form Cu electrodes 5a, The surface of 5b was made tacky. A eutectic solder powder having an average particle diameter of 25 μm was sprinkled, and excess solder was blown off with pressurized air. Then 2 at 140 ℃
The solder was heated and fixed on the electrode surface for 0 minutes. A small amount of solder powder was removed with a brush, and after applying a commercially available water-soluble flux, it was put in a reflow furnace at 230 ° C. for 1 minute to melt the solder powder. Thickness of about 30μ on the surface of Cu electrodes 5a, 5b
m fine solder electrode patterns 6a and 6b were formed. The wafer was attached to an adhesive sheet and cut with a dicing saw at a pitch of 300 μm to obtain a light emitting semiconductor device 20. After the separation, the light emitting semiconductor device 20 is die-bonded so that the electrodes of the conductive circuit 10 of the circuit board (printed circuit board) 9 and the solder electrodes (6a, 6b) of the light emitting semiconductor device are in contact with each other, and the die is bonded in a reflow oven at 230 ° C. for 1 hour. It was heated for a minute to melt the solder and bond it to the circuit board. This state is shown in FIG.

An energization test was conducted on 200 samples. In the light emitting semiconductor display device obtained by this method, the defective rate of short circuit or disconnection was 0%. In this embodiment, Al
Although a GaAs / GaAs-based light emitting semiconductor device was used, similar effects were obtained with other light emitting semiconductor devices.

(Comparative Example 1) Other than the method for forming solder electrodes,
An example in which the same GaAlAs light emitting semiconductor device as that of the first embodiment is manufactured will be shown. The process up to formation of the ohmic electrode and formation of the polyimide protective film is the same as in the first embodiment. The wafer was immersed in a solder plating bath (dip method) to form a solder layer on the Cu surface. The solder layer thickness was about 30 μm. After forming the solder layer, many solder bridges were generated. Then, it was incorporated into a circuit board in the same manner as in Example 1. This sample 200
An energization test was performed on each piece. The light emitting semiconductor display device obtained by this method had a short-circuit defect rate of 16% and a disconnection defect rate of 2%.

(Embodiment 2) Hereinafter, an example in which the present invention is applied to a Hall element will be described. A plurality of Hall elements were made on one substrate. This plan layout is shown in FIG. Further, FIG. 5 shows a sectional structural view taken along the line BB ′ of FIG. After forming the element, it is cut into a single element for use.

The specific resistance is about 10 ⁷ Ω · cm, and the plane orientation (10
0) on the semi-insulating GaAs substrate 12 of 70 × 140 μ
The area other than the area of the cross-shaped magnetic sensitive portion of m and the input / output electrodes 6a and 6b is protected by a resist material by photolithography, energy: 180 KeV, dose: 3
After selectively implanting ²⁹ Si ⁺ by the ion implantation method under the condition of × 10 ¹² cm ⁻² , the resist material is removed, and then annealing treatment is performed at 800 ° C. for 30 minutes in an arsenic pressure atmosphere to form the n-type conductive layer 14. Formed. A silicon oxide film 13 of 0.15 μm was formed on the surface of the wafer by plasma CVD at a reaction temperature of 300 ° C.
It was formed in thickness. Cover the area other than the electrode area with a resist material,
After etching the silicon oxide film with hydrofluoric acid, AuGe (Ge: 7.5%) / Ti / Cu (each thickness is 1000Å / 1000Å / 6000Å) was vacuum-deposited as a metal electrode material. Electrode patterns 5a, 5 by lift-off method
b was formed. The pattern at this time has four metal electrodes of 80 × 80 μm in 400 μm □.

Alloying was performed at 420 ° C. for 5 minutes in a nitrogen atmosphere to form an ohmic electrode. A photosensitive polyimide (PIMEL series manufactured by Asahi Kasei Kogyo Co., Ltd., glass transition point 355 ° C.) was uniformly applied thereon by a spin coater. Electrode regions 6a and 6b by photolithography method
A pattern was formed so as to protect the area other than the dicing street portion 8. To cure the resin, heat treatment was performed at 350 ° C. for 60 minutes in a nitrogen atmosphere. The film thickness of the polyimide was 2 μm. The silicon oxide film 13 on the dicing streets 8 was etched with hydrofluoric acid.

Next, the wafer is immersed in an aqueous solution of 2-dodecylimidazole (1 wt%) whose pH is adjusted to about 4 with acetic acid at 40 ° C. for 30 seconds, followed by washing with water and drying to expose the exposed Cu electrode 5a. , 5b was provided with tackiness only. Then, a eutectic solder powder having an average particle size of 50 μm was sprinkled, and excess solder was blown off with pressurized air. Then, it was heated at 170 ° C. for 30 seconds to fix the solder on the electrode surface. A small amount of solder powder was removed with a brush, and after applying a commercially available water-soluble flux, it was put in a reflow furnace at 230 ° C. for 1 minute to melt the solder powder. Cu electrode 5
Fine solder electrode patterns 6a and 6b having a thickness of about 30 μm were formed on the surfaces of a and 5b. The wafer thus treated is attached to an adhesive sheet, and the wafer is cut at a pitch of 400 μm with a dicing saw to cut the Hall element 1.
It was set to 5. After separation, the Hall element is connected to the electrodes of the circuit board (printed circuit board) 9 and the solder electrodes (6a, 6a) of the Hall element.
Die-bond so that it contacts with b), and use a reflow furnace for 2
It was heated at 30 ° C. for 1 minute to melt the solder and bond it to the circuit board. This state is the same as in FIG.

An energization test was conducted on 200 samples. In the Hall element obtained by this method, the defective rate of short circuit or disconnection was 0%. In this embodiment, the GaAs Hall element is used, but the same effect can be obtained with a Hall element using InSb or InAs.

(Comparative Example 2) Other than the method for forming the solder electrode,
An example in which the same GaAs Hall element as in Example 2 is manufactured will be shown.
The process up to the ohmic electrode formation and the polyimide protection film formation is the same as in the second embodiment. The wafer was immersed in a solder plating bath (dip method) to form a solder layer on the Cu surface. The solder layer thickness was about 30 μm. After forming the solder layer, many solder bridges were generated. A semiconductor device was assembled in the same manner as in Example 2 below. An energization test was performed on 200 of these samples. The Hall element obtained by this method had a short circuit failure rate of 21% and a disconnection failure rate of 8%.

[0022]

According to the present invention, it is possible to form a solder electrode even in a fine pattern on the surface of a semiconductor wafer. In particular, it has a great effect on small-sized elements, and greatly improves reliability and productivity.

[Brief description of drawings]

FIG. 1 is a view exemplifying a part of a plane arrangement of a wafer according to a first embodiment.

FIG. 2 is a diagram illustrating a cross-sectional structure along the line AA ′ of the wafer of FIG.

FIG. 3 is a view showing a state in which the semiconductor device of the present invention is incorporated in a printed board.

FIG. 4 is a diagram showing a part of a plane arrangement of wafers according to a second embodiment.

5 is a diagram illustrating a cross-sectional structure along the line BB ′ of the wafer of FIG.

[Explanation of symbols]

 1 Epitaxial Wafer 2 Active Layer 3 n-Clad Layer 4 p-Clad Layer 5a Metal Electrode 5b Metal Electrode 6a Solder Electrode 6b Solder Electrode 7 Polyimide Resin 8 Dicing Street 9 Printed Circuit Board 10 Conductive Circuit 11 Magnetic Field 12 Semi-insulating GaAs Substrate 13 Silicon Oxide Film 14 n-Type Conductive Layer 20 Semiconductor Device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/92 603Z

Claims (4)

[Claims] 1. A metal electrode is formed on the surface of a semiconductor wafer, and then a predetermined portion of the surface of the metal electrode is reacted with a composition containing a tackifier compound to impart tackiness to the tackifier portion. After applying the solder powder only,
A method for manufacturing a semiconductor device having a solder electrode, which comprises heating to melt solder powder to form a solder layer on the surface of a metal electrode, and then cutting the wafer to separate the semiconductor device. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor is a compound semiconductor. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is a light emitting diode. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is a magnetoelectric conversion element.