JP2002093852A - Manufacturing method of semiconductor device, and the semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor device, where damages and positional discrepancies of a semiconductor element generated by the applied load are reduced and ultrasonic vibration to it, when jointing metal electrodes to it using ultrasonic waves, and a precise junction having weighted unevenness of its load and junction-strength distributions can be performed. SOLUTION: In the manufacturing method of a semiconductor device, where metal electrodes 4, 5 are jointed to a semiconductor element 1 by ultrasonic waves for mounting via the electrodes 4, 5 the semiconductor element 1on an electric-circuit board, prior to jointing processes respectively, there are provided irregular portions 4a, 5a on the jointing surfaces of the metal electrodes 4, 5 for jointing therethrough the electrodes 4, 5 to the element 1 so as to be jointed to the element 1 their sides, whereon the irregular portions 4a, 5a re provided. Thereby, even if oxide films 13 are formed on the surfaces of the electrode portions of the semiconductor element 1 when jointing by the ultrasonic wave, the irregular portions 4a, 5a are so passed respectively through the oxide films 13 that the metal electrodes 4, 5 are jointed properly to the semiconductor element 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device on which a semiconductor element is mounted, and more particularly, to a method for ultrasonically bonding a metal electrode to a semiconductor element and mounting the semiconductor element on an electric circuit board via the metal electrode. The present invention relates to a method for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art Generally, a semiconductor device on which a semiconductor element is mounted has a structure in which a semiconductor element and a metal electrode are connected by wire bonding. However, this structure inevitably causes problems such as noise generation and reduced reliability due to an increase in wiring inductance due to wire bonding. 2. Description of the Related Art A semiconductor device designed to be able to transmit and receive a signal and electric power with a short wiring distance has attracted attention.

Hereinafter, a semiconductor device having a conventional structure will be described with reference to the drawings. FIG. 6 shows an example of a conventional semiconductor device.
Shown in The semiconductor element 1 is a MOSFET, has a drain (not shown) as a first main electrode on the first main surface 14a of the semiconductor element main body 14, and has a second main electrode made of aluminum or the like on the second main surface 14b. It has a source 11 as an electrode and a gate 12 as a control electrode. The drain of the semiconductor element 1 is connected to the first main surface 14 a of the semiconductor element body 14.
Above, the first main electrode device electrode 2 made of a copper plate whose surface is nickel-plated is joined by the first main electrode joining means 3 using solder, and serves as an external drain terminal.

A source 11 of the semiconductor element 1 is mechanically and electrically connected to a metal electrode 8 for a second main electrode made of a cubic copper piece having a gold-plated surface by ultrasonic bonding. You. The gate 12 of the semiconductor element 1 is mechanically and electrically connected to the control electrode metal electrode 9 made of a cubic copper piece having a gold plated surface by ultrasonic bonding.

[0005] The metal electrode 8 for the second main electrode and the metal electrode 9 for the control electrode are formed so that the bonding surface to be bonded to the second main surface 14a is flat. The ultrasonic bonding of the metal electrode 8 for the second main electrode and the metal electrode 9 for the control electrode is performed as follows. As shown in FIG. 7, in a state where the semiconductor element 1 is mounted on the ultrasonic bonding stage 51 so that the second main surface 14b of the semiconductor element 1 faces upward, the ultrasonic output horn 52 is connected to the ultrasonic wave. Output head 53
Thereby, ultrasonic vibration is applied while pressing the second main electrode metal electrode 8 and the control electrode metal electrode 9 downward, thereby performing ultrasonic bonding.

When performing this ultrasonic bonding, as shown in FIGS. 6 and 7, the surfaces of the source 11 and the gate 12 made of aluminum of the semiconductor element 1 are inevitably exposed to the air to form an oxide film. 13 are formed, and this oxide film 13 hinders the ultrasonic bonding. Therefore, in joining such metal electrodes 8 and 9 to the semiconductor element 1, first, the first load is applied via the metal electrodes 8 and 9 to break the oxide film 13, and the conditions are set so that an alloy can be easily formed. ,
Ultrasonic vibration is applied under the second load to perform joining.

[0007]

However, in such a conventional method for manufacturing a semiconductor device, since the oxide film 13 formed on the surfaces of the metal electrodes 8 and 9 made of aluminum or the like is penetrated during ultrasonic bonding. It is necessary to increase the momentum associated with the first weight in proportion to the bonding area, and in applications where a large current is used, that is, in applications where the bonding area is large, there is a high possibility that the semiconductor element 1 will be broken by the first weight. Was.

Further, the metal electrodes 8 and 9 are likely to be displaced from the source 11 and the gate 12 of the semiconductor element 1 due to weighting or ultrasonic vibration, and there is a high possibility that accurate joining is not performed.

Further, when the horizontality of the metal electrodes 8 and 9 is impaired due to weighting or ultrasonic vibration, a large variation occurs in the bonding area and uneven weight distribution, and there is a high possibility that accurate bonding is not performed. .

Due to the problems described above, according to the conventional method of manufacturing a semiconductor device, the expected electric characteristics cannot be obtained stably, and the product yield and reliability are reduced. Had.

The present invention has been made in consideration of the above-described problems, and has a small load and a small displacement to the semiconductor element due to the weight when applying the ultrasonic bonding of the metal electrode to the semiconductor element and the ultrasonic vibration. It is another object of the present invention to provide a method of manufacturing a semiconductor device capable of performing accurate bonding with less unevenness in bonding strength distribution.

[0012]

In order to solve the above-mentioned problems and attain the object, the following method is specifically adopted.

According to a first aspect of the present invention, in a method of manufacturing a semiconductor device in which a metal electrode is ultrasonically bonded to a semiconductor element and the semiconductor element is mounted on an electric circuit board via the metal electrode, the bonding step may be Prior to providing a concave and convex portion on the bonding surface of the metal electrode and the semiconductor element,
The side of the metal electrode on which the uneven portion is provided is ultrasonically bonded to a semiconductor element.

According to a second aspect of the present invention, in the method of manufacturing a semiconductor device according to the first aspect, the uneven portion provided on the bonding surface is formed by pressing the bonding surface via a forming jig having the uneven surface. It is characterized by being formed by doing.

According to a third aspect of the present invention, in the method of manufacturing a semiconductor device according to the first aspect, the uneven portion provided on the bonding surface is formed by polishing and forming the bonding surface.

According to a fourth aspect of the present invention, in the method of manufacturing a semiconductor device according to the first aspect, the uneven portion provided on the bonding surface is formed by eroding the bonding surface by a chemical reaction. I do.

According to a fifth aspect of the present invention, there is provided a semiconductor device in which the semiconductor element is mounted on an electric circuit board via a metal electrode ultrasonically bonded to the semiconductor element. It is characterized in that an uneven portion is provided on the bonding surface and ultrasonic bonding is performed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a semiconductor device and a method of manufacturing the same according to the present invention will be described below with reference to the drawings. In addition, the same reference numerals are given to substantially the same parts as those of the conventional semiconductor device and the device related to the manufacture thereof, and the description will be made.

(First Embodiment) FIG. 1 is a schematic sectional view showing a semiconductor device according to a first embodiment of the present invention. The semiconductor element 1 is a MOSFET, has a drain (not shown) as a first main electrode on the first main surface 14a of the semiconductor element main body 14, and has a second main electrode made of aluminum or the like on the second main surface 14b. It has a source 11 as an electrode and a gate 12 as a control electrode. The drain of the semiconductor element 1 is formed on the first main surface 14a of the semiconductor element main body 14 by soldering to the device electrode 2 for the first main electrode made of a copper plate whose surface is nickel-plated.
It is joined by the joining means 3 for the main electrode and functions as an external drain terminal.

The source 11 of the semiconductor element 1 is made of a second copper piece having a cubic shape with projections and depressions, the surface of which is plated with gold.
It is mechanically and electrically connected to the metal electrode 4 for the main electrode by ultrasonic bonding. Gate 1 of semiconductor element 1
Numeral 2 is mechanically and electrically connected to a control electrode metal electrode 5 made of a cubic copper piece having projections and depressions on a bonding surface by ultrasonic bonding.

Here, in the semiconductor device of the present embodiment, among the surfaces of the metal electrodes 4 and 5, the bonding surfaces to be bonded to the semiconductor element 1 are provided with the uneven portions 4a and 4a prior to the ultrasonic bonding step.
5a is provided.

FIG. 2 shows an uneven portion 4a on the joining surface of the metal electrodes 4 and 5, which are components of the semiconductor device according to the present embodiment.
The method for forming 5a is illustrated using the metal electrode 4 as an example. That is, a forming jig 60 having a concave-convex surface 61 and made of a substance harder than the metal electrode 4 is set on the press device stage 70 on a surface serving as a bonding surface of the metal electrode 4 formed of a gold-plated cubic copper piece, A pressure and a pressure that does not impair the overall shape of the metal electrode 4 so that the uneven surface 61 of the forming jig 60 is well transferred to the surface serving as the bonding surface of the metal electrode 4.
Pressing is performed by the press device head 71 at the time and temperature.

By the above steps, the intended concave and convex portions 4a are formed on the surface to be the bonding surface of the metal electrode 4, and this surface is used as the bonding surface to form the aluminum electrode portion (source 1) of the semiconductor element 1.
Ultrasonic bonding is performed in a manner opposed to 1). In the upper part of FIG. 1, the shapes of the metal electrodes 4 and 5 realized in the present embodiment are shown with the concave and convex portions 4a and 5a serving as bonding surfaces facing upward.

FIG. 3 is a cross-sectional view of the semiconductor device according to the present embodiment, including a part of the ultrasonic bonding apparatus, at the moment when the first weight is applied at the time of ultrasonic bonding. As shown in FIG. 3, with the semiconductor element 1 placed on the ultrasonic bonding stage 51 such that the second main surface 14 b of the semiconductor element 1 faces upward, the ultrasonic output horn 52 is connected to the ultrasonic wave. When the output head 53 presses the metal electrode 4 for the second main electrode and the metal electrode 5 for the control electrode downward while applying ultrasonic vibration to perform ultrasonic bonding, the bonding surface of the metal electrodes 4 and 5 is formed. The formed concavo-convex portions 4a and 5a are implanted deeper than the oxide film 13 and shallower than the thickness of the source 11 and the gate 12, which are aluminum electrodes. Positional displacement with respect to the electrode portion (source 11 and gate 12) of the element 1 is less likely to occur, and thus accurate bonding is possible.

In addition, the first weight is insufficient and the uneven portions 4a, 5a
Even if the oxide film 13 does not penetrate due to the step size, shape, etc., the oxide film 13 may be broken by the ultrasonic vibration and sufficient bonding may be performed. Since the ultrasonic vibration is more easily transmitted at the periphery of the surface where the metals come into contact with each other, that is, at the edge, even in the above-described case, compared to the conventional method of manufacturing a semiconductor device, the present embodiment can realize an electrode bonding surface having many edges. The semiconductor device can be easily joined by employing the method of manufacturing a semiconductor device according to the embodiment.

Further, when the horizontality of the metal electrodes 4 and 5 is impaired by the weighting or the ultrasonic vibration, the conventional method causes a large variation in the joint area and the unevenness of the weight distribution. Then, the variation of the bonding area and the unevenness of the weight distribution can be suppressed to a smaller size by employing the method of manufacturing a semiconductor device of the present embodiment, so that more accurate bonding can be performed.

The uneven portions 4a, 5a of the metal electrodes 4, 5
As shown in FIG. 1, if the horizontal cross-sectional area becomes smaller toward the upper side (for example, a pyramid shape as shown in FIG. 1), the concave and convex portions 4a and 5a bite deeper than the oxide film 13. It is easy and preferable, but the present invention is not limited to this. Irrespective of the shape of the uneven portions 4a and 5a, the recesses 4a and 5a can be more easily cut into the source 11 and the gate 12 than in the case of a flat surface, and can be easily joined.

(Embodiment 2) FIG. 4 is a schematic sectional view showing a semiconductor device according to a second embodiment of the present invention. The same components as those shown in FIG. 1 are denoted by the same reference numerals, detailed description thereof will be omitted, and different portions will be described here.

That is, in the first embodiment,
As the metal electrodes to be ultrasonically bonded to the semiconductor element 1, the metal electrodes 4 and 5 having the concave and convex portions 4 a and 5 a provided on the bonding surfaces by a pressing process are used. In the manufacturing method, the metal electrode 4,
As an alternative to 5, an uneven portion 6 may be formed on the joining surface by a polishing process.
Polished metal electrodes 6 and 7 provided with a and 7a are used.

FIG. 5 shows an uneven portion 6a,
The method for forming 7a is illustrated using the metal electrode 6 as an example. That is, after the metal electrode 6 made of a cubic copper piece was fixed to the polishing sample fixture 81, the surface to be the bonding surface of the metal electrode 6 was bonded to the surface with abrasive grains made of a substance harder than the metal electrode 6. Polishing is performed by the rotating polishing disk 82.

Since the groove-shaped concave and convex portions 6a are formed on the surface serving as the bonding surface of the metal electrode 6 by the above steps, this surface is used as the bonding surface to form the aluminum electrode portion (source 1) of the semiconductor element 1.
Ultrasonic bonding is performed in a manner opposed to 1). Note that if gold plating is performed on the surface of the metal electrode 6 prior to bonding, an oxide film is less likely to be formed on the surface of the metal electrode 6, so that bonding is further simplified. In the upper part of FIG. 4, the shapes of the metal electrodes 6 and 7 realized in the present embodiment are shown by the uneven portions 6 a and
7a is shown facing up.

Here, in the first embodiment, when the metal electrodes 4 and 5 are pressed, the metal electrodes 4 and 5 are pressed.
It was necessary to control the pressing pressure so as not to impair the overall shape of the metal electrodes, and it was difficult to accurately control the electrode height after molding. The shape is hardly impaired, and the height of the electrode after molding can be accurately controlled by changing conditions such as the polishing time.

The uneven portions 6a, 7a of the metal electrodes 6, 7
As shown in FIG. 4, a triangular shape having a smaller horizontal cross-sectional area toward the top as shown in FIG. 4 is preferable because the uneven portions 6a and 7a can easily penetrate deeper than the oxide film 13.
The shape is not limited to this, and the shape of the uneven portion 6 is not limited.
Regardless of whether they are a and 7a, they can be easily sunk into the source 11 and the gate 12 and joined easily as compared with the case of a plane.

Further, the shapes of the concave and convex portions 4a to 7a of the metal electrodes 4 to 7 in the first and second embodiments may be formed by eroding a bonding surface by a chemical reaction. In the first and second embodiments, the metal electrodes 4 and 5 are metal pieces. However, as in these embodiments, the metal electrodes 4 and 5 are electrically connected to the circuit board. It is needless to say that other shapes, such as a plate shape or a column shape, capable of transmitting and receiving signals and power can be easily derived from the gist of the present invention.

Further, in the above-described first and second embodiments, only an example in which a MOSFET is used as the semiconductor element 1 has been described. However, a different type of semiconductor element 1 such as an IGBT or a diode, It is clear from the gist of the present invention that the same effect can be obtained even when an IC or the like in which is integrated.

[0036]

As described above, according to the method of manufacturing a semiconductor device of the present invention, the uneven surface is provided on the bonding surface of the metal electrode to be bonded to the semiconductor element, and the uneven side of the metal electrode is formed on the semiconductor element. By performing the ultrasonic bonding, the first load for penetrating the oxide film on the surface of the electrode portion of the semiconductor element at the time of the ultrasonic bonding can be reduced by a small value as compared with the conventional manufacturing method (bonding method). The possibility that the semiconductor element is destroyed by the first weight is reduced.

Further, since the metal electrode is less likely to be displaced from the electrode portion of the semiconductor element due to the load or the ultrasonic vibration, accurate bonding can be performed. Furthermore, when the horizontality of the metal electrode is impaired due to weighting or ultrasonic vibration, the conventional method causes a large variation in the bonding area and a non-uniform weight distribution, but the variation in the bonding area compared to the conventional method. Further, since the unevenness of the weight distribution can be suppressed to a small value, more accurate bonding can be performed, good electrical characteristics can be stably obtained, and an improvement in product yield and an improvement in reliability can be realized.

That is, when the production method of the present invention is adopted,
As compared with the case of using a conventional semiconductor bonding method, it is possible to realize an excellent semiconductor device capable of improving the electrical characteristics, improving the product yield, and improving the reliability.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a semiconductor device according to a first embodiment of the present invention, and a perspective view of a single metal electrode is also shown at the top.

FIG. 2 is a cross-sectional view showing a step of forming an uneven portion on a bonding surface of a metal electrode used in the method for manufacturing a semiconductor device according to the embodiment.

FIG. 3 is a cross-sectional view showing a step of ultrasonically bonding a metal electrode to the semiconductor device in the method for manufacturing a semiconductor device according to the embodiment.

FIG. 4 is a schematic sectional view showing a semiconductor device according to a second embodiment of the present invention, and also shows a perspective view of a single metal electrode in an upper part.

FIG. 5 is a cross-sectional view showing a step of forming an uneven portion on the bonding surface of the metal electrode used in the method for manufacturing a semiconductor device according to the embodiment.

FIG. 6 is a schematic sectional view showing a conventional semiconductor device.

FIG. 7 is a cross-sectional view showing a step of ultrasonically bonding metal electrodes in the conventional semiconductor device manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor element 4-7 Metal electrode 4a-7a Uneven part 11 Source (electrode part) 12 Gate (electrode part) 13 Oxide film 14 Semiconductor element main body 51 Ultrasonic bonding stage 52 Ultrasonic output horn 53 Ultrasonic output head 60 Molding jig Tool 61 Uneven surface 81 Abrasive sample fixture 82 Abrasive disk

Claims (5)

[Claims] An ultrasonic bonding of a metal electrode to a semiconductor element,
In a method of manufacturing a semiconductor device in which the semiconductor element is mounted on an electric circuit board via the metal electrode, an uneven portion is provided on a bonding surface of the metal electrode to be bonded to the semiconductor element prior to a bonding step, A method of manufacturing a semiconductor device, comprising: ultrasonically bonding a side of an electrode provided with the uneven portion to a semiconductor element. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the uneven portion provided on the bonding surface is formed by press-forming the bonding surface via a forming jig having the uneven surface. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the uneven portion provided on the bonding surface is formed by polishing and shaping the bonding surface. 4. The uneven portion provided on the joint surface is formed by eroding the joint surface by a chemical reaction.
13. The method for manufacturing a semiconductor device according to item 5. 5. A semiconductor device in which the semiconductor element is mounted on an electric circuit board via a metal electrode ultrasonically bonded to the semiconductor element, wherein an uneven portion is provided on a bonding surface of the metal electrode with the semiconductor element. A semiconductor device characterized by being subjected to ultrasonic bonding.