JP2697866B2 - A method for manufacturing a semiconductor device. - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a manufacturing technique thereof, and more particularly to a technique effective when applied to the manufacture of a semiconductor device having a small wire bonding pad pitch and a semiconductor device for high frequency.

[Conventional technology]

Gallium arsenide field effect transistors (abbreviated as GaAs-FETs) formed based on a zinc-blende-type crystal structure substrate are widely known as microwave transistors having features such as low noise, high cut-off frequency, and high output. Have been. Also,
As one of the GaAs-FETs, a Schottky barrier gate type field effect transistor (also referred to as MESFET) is known. The GaAs-MESFET has a source / drain electrode having an ohmic contact structure provided on a main surface of an active region of n conductivity type;
One or two gate electrodes having a Schottky junction structure are provided in the middle thereof to form a single gate structure or a dual gate structure.

In recent years, GaAs-MESFETs have also been used as semiconductor devices for receiving satellite broadcasting. SHF band low noise GaAs for satellite broadcasting reception.
For s-FET, for example, see “National Technical Report (National Tech Report)” issued by Ohm Co., Ltd.
nical Report) ", April 1986, issued on April 18, 1986, pages 26 to 34. In this document, it is important to reduce the input capacitance in order to reduce noise. In the case of the semiconductor device described in this document, bonding on a chip (semiconductor element) is required to reduce the parasitic input capacitance. It describes that the area of the pad (wire bonding pad) is designed to be a necessary minimum and that a ceramic package is used.

On the other hand, the wire bonding for electrically connecting the electrode of the semiconductor element, that is, the wire bonding pad and the lead, is described in, for example, “Electronic Materials Supplement” issued by the Industrial Research Institute.
As described on pages 123 to 129 issued on November 18, 1986, thermocompression bonding (TC method) and ultrasonic thermocompression bonding (TS
Method) and ultrasonic method (US method). In the thermocompression bonding method and the ultrasonic thermocompression bonding method, after the tip of the wire is formed into a sphere (ball), the ball portion is crushed by the tip surface of the capillary, and the tip of the wire is fixed by pressure to the wire bonding pad. At the time of fixing by pressure bonding, the capillary is vibrated by the ultrasonic thermocompression bonding method. Also, in the same document, when the tip of a wire is formed into a ball with an electric torch (discharge), the polarity is made negative (the wire is plus and the discharge electrode is minus) to improve the uniformity of the ball. Is described.

In addition, the document describes the following as a technical problem.

In other words, this document states that "Ultra LSI and ASIC products have been progressing toward higher integration, more pins, and surface mounting, and the accuracy requirements have been further strengthened. TS bonding assumed a pad pitch of 70 μm or less. In case, wire size 18-20μ
m, Crimp ball diameter 40 ~ 50μm, total position accuracy ± 4 ~ ± 5μm
Is expected to be required, but at this stage 100-130μ
m is considered to be a practical level.

Ball shrinking using fine wires seems to be the most effective, but the issues are loop control, wire flow during resin sealing, the quality of the bolt neck capillary, and reliability in terms of life. "Is described.

[Problems to be solved by the invention]

The SHF band GaAs-FETs all use small special ceramic packages to reduce the parasitic capacitance, thereby improving the high frequency characteristics. Further, in the wire for electrically connecting the semiconductor element (chip) and the lead sealed in this package, the same space is connected by a plurality of wires in order to reduce the inductance of the wire. In this case, in order to keep the chip size as it is even if the number of wire bonds increases, the pad size of the wire bonding pad (hereinafter, also simply referred to as a pad) is a square (65 μm square) having a side of 65 μm. The following are required:

In the case of wedge bonding, the ultrasonic vibration is applied along the extending direction of the wire, and the crushing width of the wire due to the ultrasonic vibration is not so large.
Bonding can be performed without protruding into a 65 μm square pad.

However, in the case of the thermocompression bonding method (ultrasonic thermocompression bonding method), the tip of the wire is formed into a ball (ball), and the wire is crushed into a ring shape at the tip of the capillary to perform bonding. The diameter is even larger than the ball. Therefore, in the case of a wire having a diameter of 20 μm, the conventional capillary has a crushed diameter of 70 μm to 80 μm. Therefore, the wire bonding pad is 90 μm square, for example, in consideration of the margin of wire bonding. In this way, if the pad is 90 μm square, IC
The pad pitch in the structure in which the pads are arranged side by side, for example, is such that when the pad interval for preventing short circuit is, for example, 30 μm, the pad pitch is equal to the pad dimension.
It is about 120 μm, which is the sum of 90 μm and 30 μm pad interval for preventing short circuit. In this case, the ball diameter is 6
It is formed around 0 μm.

As described above, when the pad size is 65 μm □,
Bonding is possible by the ultrasonic method, but bonding cannot be performed by the conventional ultrasonic thermocompression bonding method (thermocompression bonding method) without protruding the crushed ball portion from the wire bonding pad.

However, since the ultrasonic method has directionality in bonding, the mechanism of the bonding apparatus is complicated, the cost of the machine is high, and the mass productivity and reliability are low. In contrast, thermocompression (ultrasonic thermocompression)
Is a bonding technique suitable for mass production without directivity during bonding.

The inventor of the present invention has studied the technology capable of performing wire bonding to a smaller size wire bonding pad by thermocompression bonding (ultrasonic thermocompression bonding) by improving the structure of the capillary used and changing the bonding method. .

An object of the present invention is to provide a semiconductor device in which a wire bonding pad has been reduced in size.

Another object of the present invention is to provide a semiconductor device having excellent high-frequency characteristics due to downsizing of a wire bonding pad, for example, an SHF band low noise GaAs-FET.

It is another object of the present invention to achieve downsizing of a semiconductor device by reducing the wire bonding pad pitch by downsizing the wire bonding pad.

Another object of the present invention is to provide a smaller semiconductor device by downsizing a package by downsizing a semiconductor element.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[Means for solving the problem]

The outline of a representative invention among the inventions disclosed in the present application will be briefly described as follows.

That is, in the manufacture of a semiconductor device by the ultrasonic thermocompression bonding method of the present invention, when fixing the tip of a wire guided in a state inserted into a capillary to a wire bonding pad of a GaAs semiconductor element, a guide hole is formed at the tip. Using a capillary which is sequentially expanded in two stages by a first tapered hole and a second tapered hole, the diameter of the wire at the tip of the wire is larger than the maximum diameter of the first tapered hole and the maximum diameter of the second tapered hole. A smaller spherical portion is formed, and the spherical portion is pressed by the tapered surface of the second tapered hole, and is thermocompression-bonded to the bonding pad with a maximum diameter smaller than the maximum diameter of the second tapered hole. The wires are fixed to the bonding pads by sonic thermocompression bonding.

[Action]

According to the above-described means, in manufacturing a semiconductor device by the ultrasonic thermocompression bonding method of the present invention, the maximum diameter portion of the tapered hole at the tip of the capillary is the diameter of the crushed ball at the tip of the wire.
The diameter of the wire is set to 63 μm, which is close to 60 μm, and the diameter of the ball at the tip of the wire having a diameter of 20 μm is set to a small value of 40 μm to 50 μm so as to fill the tapered hole of the capillary due to collapse during bonding. Therefore, at the time of bonding, the capillary is stopped at a height of 15 μm from the surface of the wire bonding pad. As a result, the ball is crushed by the tapered hole surface of the capillary and is thermocompression-bonded to the wire bonding pad. Does not appear. As a result,
Since the crushing diameter of the ball at the tip of the wire is about 60 μm,
65μm wire bonding pad to connect wires
□ and smaller.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an SHF band low noise GaAs-M according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a semiconductor device constituting an ESFET, FIG. 2 is a plan view of the semiconductor device also with a cap removed, FIG. 3 is a plan view showing a chip also constituting a GaAs-MESFET,
FIG. 4 is a sectional view showing the structure of the chip, and FIGS.
FIG. 14 is a view of each step in the manufacture of the semiconductor device constituting the GaAs-MESFET, and FIG. 5 is a GaAs-MESFET.
Plan view showing a lead frame used for manufacturing
FIG. 7 is a plan view showing a state where the base is fixed to the lead frame, FIG. 7 is a partially enlarged bottom view showing a state where the base and the lead frame are joined, and FIG. 8 is a lead frame where a chip is fixed on the base. , FIG. 9 is a front view showing a main part of a wire bonding apparatus, FIG. 10 is a cross-sectional view showing a main part of a capillary, and FIG. 11 is a main part of a capillary holding a ball-tipped wire. , FIG. 12 is a cross-sectional view showing a state in which a ball portion is crushed by a capillary, FIG. 13 is a cross-sectional view showing a wire stretched by a capillary, and FIG. 14 is a sealing in which a cap is attached to a base. It is sectional drawing which shows a state.

The semiconductor device of this embodiment, that is, SHF band low noise GaAs
The semiconductor device constituting the s-FET has a structure as shown in FIG. 1 and FIG. As shown in FIG. 2, the semiconductor device 1 includes a package 2 made of an octagonal columnar ceramic, and a plurality of leads 3 each having one end attached to the lower surface of the package 2. The leads 3 are located on an XY plane whose origin is the center of the package 2 and extend in a cross shape along the XY axis direction. A thick lead extending in the ± Y direction is a source lead 4, a lead extending in the + X direction is a drain lead 5, and a lead extending in the −X direction is a gate lead 6.

The package 2 includes a base 7 and a cap 8 that covers a main surface of the base 7, that is, an upper surface. The base 7 includes a base body 9 of an octagonal plate made of ceramic, and a ceramic frame portion 10 having an outer periphery formed of an octagonal frame provided at a peripheral portion of a main surface of the base body 9. The cap 8 is air-tightly fixed on the upper surface of the frame 10 via a bonding material 11. In the base body 9, a conductor layer 12 is partially provided from the main surface of the base body 9 to the peripheral surface and the back surface thereof. These conductor layers 12 are a conductor layer 13 for source, a conductor layer 14 for drain, and a conductor layer 15 for gate. The base 7 is formed by a lamination printing method or the like, and is integrally formed by firing.

The source lead 4, the drain lead 5, and the gate lead 6 form a bonding material 16 corresponding to the source conductor layer 13, the drain conductor layer 14, and the gate conductor layer 15 extending on the lower surface of the base 7. Connected through.
Each lead 3 is provided with a plating film 17 on its surface.

On the other hand, in the base body 9 of the base 7, as described above, the source conductor layer 13 and the drain conductor layer 1 extend from the main surface to the peripheral surface and the back surface of the base body 9.
4, a gate conductor layer 15 is provided. The source conductor layer 13 forms a wide chip mounting portion 20 passing through the center on the main surface of the base body 9 as shown in FIG. The chip mounting portion 20 has the narrowest width at the center and has a drum shape that expands toward the periphery of the base body 9. And this chip mounting part
At the center of 20, there is a bonding material 21 made of silver paste etc.
An SHF band low noise GaAs-FET chip (semiconductor element) 22 is mounted. The drain conductor layer 14 and the gate conductor layer 15 on the main surface of the base body 9 form wire bonding portions 23 and 24, respectively. The wire bonding portions 23 and 24 include a wire bonding pad (drain electrode) for the drain of the chip 22.
25, Gate wire bonding pad (gate electrode) 2
The other end of the wire 27 whose one end is fixed to 6 is fixed. A source wire bonding pad (source electrode) 28 on the main surface of the chip 22 and the source conductor layer 13 are electrically connected by wires 27. Although the drain wire bonding pad 25 and the gate wire bonding pad 26 are single, the source wire bonding pad 28 is provided at two places, and two wires 27 are connected side by side at each place. I can do it. Therefore, the gate (G) electrode and the drain (D) electrode are connected to the conductor layer 12 by one wire 27, while the source (S) electrode is connected to the conductor layer 12 by four wires 27.
It will be connected to 12. As a result, the inductance of the wire connected to the source electrode decreases.

Incidentally, the wires 27 are connected by an ultrasonic thermocompression bonding method. The chip 22 to which the wire 27 is connected is
The structure is as shown in FIG. 4 and FIG. The SHF band low noise GaAs-FET chip 22 has a single gate structure in which one gate electrode 32 is provided between a source electrode 30 and a drain electrode 31, as shown in FIG. The chip 22 includes a semi-insulating GaAs substrate 33, a buffer layer 34 formed on the main surface, an n-type active layer 35 formed on the buffer layer 34, and two sides of the active layer 35. Each of them is provided with an n ^{+ -type} ohmic contact layer 36. On the ohmic contact layer 36, a source electrode 30 and a drain electrode 31 are separately provided. The source electrode 30 and the drain electrode 31 are made of AuGe / Ni /
Made of Au. In addition, a gate electrode 32 made of Al is provided on the active layer 35 between the source electrode 30 and the drain electrode 31, more specifically, at the bottom of the recess groove formed by the recess etching. In addition, the chip 22
Is covered with a passivation film 37. Also,
As shown in FIGS. 3 and 4, in regions not covered by the passivation film 37, the above-described drain wire bonding pads 25, gate wire bonding pads 26, and source wire bonding pads 28 are formed.
Are formed. These wire bonding pads 2
5, 26 and 28 are smaller than the conventional semiconductor device. That is, the drain wire bonding pad 25 and the gate wire bonding pad 26 have a rectangular shape (square) with sides a and b each having a length of 65 μm. Further, since the source wire bonding pad 28 connects the two wires 27 side by side, the length of one side c is 65 μm, and the length of the side wire c is 65 μm.
And the source wire bonding pad 28, but the length of the other side d is as long as 150 μm ± 15 μm. And these wire bonding pads 25, 26,
The wire 27 is connected to the wire 27 having a diameter of 20 μm and the crushed portion 38 having a diameter of about 60 μm. A wire bonding method performed by reducing the collapse diameter of the collapse portion 38 will be described later.

Next, a method for manufacturing such a semiconductor device will be described.

In manufacturing the SHF band low noise GaAs-FET of this embodiment, a lead frame 39 as shown in FIG. 5 is used. The lead frame 39 is made of, for example, 0.15 of iron-nickel alloy, iron-nickel-cobalt alloy, copper alloy or the like.
It is formed by etching a metal plate having a thickness of about mm to 0.2 mm or patterning it by a precision press. Further, a plating film 17 such as gold plating is provided on the surface of the lead frame 39 (see FIG. 8).
The lead frame 39 has a shape in which a plurality of unit lead frame patterns for manufacturing a single semiconductor device are arranged in series. That is, this lead frame 39
As shown in FIG. 5, a pair of horizontal frames 40 extending in parallel
And a vertical frame 41 that is orthogonal to the horizontal frame 40 and connects the pair of horizontal frames 40. Since the vertical frames 41 are arranged at regular intervals, a frame is formed by a pair of adjacent vertical frames 41 and a pair of horizontal frames 40. This frame area constitutes a unit lead frame pattern. Cantilever type lead 3 from each corner of each frame along each diagonal of said frame
Is protruding. The source leads 4 of the leads 3 protrude from each corner of one diagonal line and extend along the diagonal line to near the center of the frame. The drain lead 5 and the gate lead 6 protrude from the other two corners of the frame, which are the respective ends of the other diagonal lines, and extend to near the center of the frame without contacting the source lead 4.
The source lead 4 is formed thick. The horizontal frame 40 is provided with a guide hole 42 and a notch 43. These guide holes 42 and cutouts 43 are used for transferring and positioning the lead frame 39 on the guide table.

The base 7 is attached to such a lead frame 39 as shown in FIG. The base 7 includes a base body 9 and a frame 10. Therefore, each conductor layer 12 (source conductor layer) extending on the lower surface of the base body 9 is formed.
13, the drain conductor layer 14 and the gate conductor layer 15) face the respective leads 3 of the lead frame 39 and are connected via a bonding material 16 made of silver paste or the like (see FIGS. 7 and 8). . At the center of the main surface of the base 7 fixed to the lead frame 39, the drum-shaped source conductor layer 13, that is, the chip mounting portion 20, comes to appear. Also, this chip mounting part
The wire bonding portions 23 and 24 of the drain conductor layer 14 and the gate conductor layer 15 respectively appear on the main surfaces of the base body 9 on both sides at the center of 20.

Next, as shown in FIG.
At the center of 20 via a bonding material 21 made of silver paste etc.
The F band low noise GaAs-FET chip 22 is fixed. Further, the single wire bonding pad 25 for drain and the wire bonding pad 26 for gate of the chip (semiconductor element) 22 are connected to the wire bonding portions 23 and 24 by wires 27. Further, the source wire bonding pad 28 and the chip mounting portion 20 located on both sides of the gate wire bonding pad 26 respectively have two wires.
Connected at 27 (see FIG. 2). The connection of the wire 27 is performed by an ultrasonic thermocompression bonding method.

This is one of the features of the present invention. In this ultrasonic thermocompression bonding method, a capillary 50 having a characteristic structure as shown in FIG. 10 is used. This capillary 50
Has a cylindrical structure like a general capillary, and has a guide hole 51 for guiding the gold wire 27 through the center thereof. The guide hole 51 is a tapered hole in consideration of the convenience of the insertion of the wire 27, and at the lower end thereof, for example, is a hole having an equal diameter e for guiding the wire 27. A first tapered hole 52 concentrically connected to the guide hole 51 and having an expansion angle of θ (θ is 90 degrees in this embodiment), and an expansion angle α connected to the first tapered hole 52. A second tapered hole 53 (α is 130 degrees in this embodiment) and a tapered hole 54 are provided. Since the capillary 50 of this example has a structure using the wire 27 having a diameter of 20 μm, the diameter e of the guide hole 51 is 25 μm.
It has become. The diameter f at the boundary where the first tapered hole 52 changes to the second tapered hole 53 is 33 μm. Furthermore, the maximum diameter of the second tapered hole 53, that is,
The diameter g of the lower end is set to 63 μm. Further, in this example, since the wire bonding is performed so as to have a collapse diameter of about 60 μm on a wire bonding pad having a side length of 65 μm, and two wires are connected in close proximity, the capillary 50 The diameter of the tip (lower end) is formed as small as possible. For example, wire bonding can be performed so that the pitch between adjacent wires is about 90 μm to 95 μm.

Further, the spherical portion at the tip of the wire 27 inserted and held in the capillary 50, that is, the ball 55 is smaller than the maximum diameter portion of the second tapered hole 53 as shown in FIG. , 40 μm to 50 μm. Then, the wire bonding pad diameter w (w = 65)
μm) is connected by ultrasonic thermocompression bonding.
Further, as will be described later, the capillary 50 is moved from the surface of the wire bonding pad 56 as shown in FIG.
Bonding is performed so as to stop descending at a certain height, the ball 55 of the wire 27 is crushed to a desired degree, and thermocompression bonding (in this example, ultrasonic thermocompression bonding) is performed. At this time, since the crushed ball 55 stops at a height of h from the surface of the wire bonding pad 56, the protruding edge of the crushed ball 55 extends from the maximum diameter portion of the second tapered hole 53. No more overflowing. Therefore, the diameter (crushed diameter m) of the crushed portion 38 of the fixed wire 27 is 63 μm, which is the maximum diameter g of the second tapered hole 53.
Less than about 60 μm in diameter.

Next, a wire bonding apparatus equipped with such a capillary 50 will be described.

As shown in FIG. 9, the wire bonding apparatus is roughly composed of a table 60 on which a lead frame 39, which is a work, is placed, and a bonding unit 61. A lead frame 39 is placed on the table 60, and the lead frame 39 is intermittently transferred in the longitudinal direction by a transfer mechanism (not shown). Also this table
A heat block 62 is built in the unit 60, and the mounted lead frame 39 is heated to a desired temperature so that ultrasonic thermocompression bonding can be reliably performed.

On the other hand, the bonding unit 61
XY table 63 arranged on the side of 60 and this XY table
It comprises a bonding head 64 mounted on 63, a bonding arm 65 extending from the bonding head 64 onto the table 60, a clamp mechanism 68 including a pair of clamp arms 66 and 67, and the like. The capillary 50 having the above-described structure is attached to the tip of the bonding arm 65. And this capillary 50
A wire 27 made of gold (gold wire) is inserted into the guide hole 51. The tip of the pair of clamp arms 66 and 67 of the clamp mechanism 68 is turned on and off by an electromagnetic plunger (not shown), and the capillary 50
Is clamped above the wire 27. The wire 27 is inserted into and guided by a ring-shaped guide 70 attached to the tip of a support arm 69 projecting from the clamp arm 66. The wire 27 is unwound from a reel or the like (not shown), and a back tension is constantly applied, so that the tip of the wire 27 is drawn into the capillary 50.

On the other hand, on the side of the capillary 50, a wire spheroidizing mechanism including the wire 27 is configured. This wire spheroidizing mechanism has a desired discharge electrode 71 at the tip of the capillary 50 as required. In addition, this discharge electrode 71 and the wire
27 is connected to a power supply circuit 72, and the wire 27 is an anode (+)
In addition, the discharge electrode 71 is set to be a cathode (-). By making wire 27 the anode, the discharge
A stable ball 55 generated at the tip of 27 and having a small diameter is formed with good reproducibility. By such discharge, the ball
The diameter of 55 is formed to be about 2.0 to 2.5 times the diameter of wire 27. Therefore, in the case of a wire 27 having a diameter of 20 μm,
The diameter of the ball 55 is formed to be about 40 μm to 50 μm. Further, a gas injection tube 73 is provided along the discharge electrode 71 in order to further stabilize the spheroidization of the wire. A gas supply source 74 is connected to the gas injection pipe 73. Further, a heater 76 for heating the gas 75 to a desired temperature is built in the gas injection pipe 73.

In such a wire spheroidizing mechanism, the wire 27 is held by the clamp mechanism 68. In this holding state, the tip of the wire 27 protrudes from the tip of the capillary 50. Therefore, the discharge electrode 71 is operated to advance below the capillary 50, and the tip of the discharge electrode 71 is positioned directly below the wire 27. In this state, the gas 75 is blown out from the gas injection pipe 73 to the tip of the wire 27, and the tip of the wire 27 is surrounded by the gas 75. The gas 75 is, for example,
It is composed of a nitrogen gas and a hydrogen gas and is a reducing gas, so that oxidation of the wire can be prevented. Therefore, in this reducing atmosphere, the wire 27 and the discharge electrode 71
Between the wire 27 and the tip of the wire 27
A ball 55 of 40 μm to 50 μm is formed. In the case of the conventional thermocompression bonding method or ultrasonic thermocompression bonding method,
When the wire diameter is 20 μm, the diameter of the ball 55 is
70 μm to 80 μm is generally used. In this embodiment, this is one of the features of the present invention.
μm to 50 μm. This is because, as described above, when the ball 55 is crushed only by the tapered hole 54 connected to the guide hole 51 of the capillary 50, the crushed portion 38 of the crushed ball 55 protrudes from the tapered hole 54. This is to prevent the tip of the capillary 50 from overflowing into the flat surface area as in the related art.

When the ball 55 is formed at the tip of the wire 27 in this manner, the discharge electrode 71 of the wire spheroidizing mechanism is connected to the capillary 50.
Out of the lower area of. Thereafter, the clamp operation of the clamp mechanism 68 is released. As a result, the tip of the wire 27 is drawn into the guide hole 51 of the capillary 50 by the back tension. However, since the ball 55 is formed at the tip of the wire 27, as shown in FIG. 11, the ball 55 is connected to the edge of the guide hole 51 of the capillary 50,
Strictly speaking, it comes to rest on the tapered surface of the tapered hole 54.

Next, the bonding unit 61 is operated, and as shown in FIG.
The wire 27 is stretched between the wire bonding pad 56 and the conductive layer 12 of the base 7 as the second bonding portion.

That is, by the lowering operation of the bonding arm 65, the capillary 50 is lowered as shown by the arrow, and the ball 55 of the wire 27 is turned into a chip which is a part of the work.
22 electrodes, for example, a wire bonding 56 which is a wire bonding pad 25 for drain. In addition, the capillary 50 not only presses the ball 55 but also applies ultrasonic vibration.
Hole 54 formed by the tapered hole 52 and the second tapered hole 53
And is fixed to the wire bonding pad 56 by ultrasonic thermocompression bonding. At this time, control is performed so as to stop at a position of height h from the surface of the wire bonding pad 56 and not to descend any more.

This means that the capillary 50 is connected to the wire bonding pad 56
When it is lowered enough to make contact with it, the bend angle is reduced to 40 μm to 50 μm, the diameter of the ball 55 is reduced, and the guide hole of the capillary 50 is reduced.
Even if a space is provided for accommodating the crushed portion 38 crushed in connection with 51, the crushed portion 38 overflows from this space and the capillary
As a result, the crushed portion 38 is crushed by the flat surface at the tip of 50, and as a result, the crushed portion 38 is larger than the maximum diameter g of the second tapered hole 53 of 63 μm, and has a crushed diameter of 70 μm or 80 μm as in the related art. It is because it becomes. Therefore,
In this embodiment, as shown in FIG. 12, the collapsed diameter m of the collapsed portion 38 is smaller than the maximum diameter of the tapered hole 54 of the capillary 50, that is, the maximum diameter g of the second tapered hole 53, The wire bonding pad 56 having a side length w of 65 μm has a crushed portion 38 having a diameter of 60 μm to perform wire bonding. The ball 55 of the wire 27
It has been confirmed that a sufficient bonding strength can be obtained only by crushing the wire with a tapered hole 54 connected to the guide hole 51 of the capillary 50. The reason why the tapered hole 54 of the capillary 50 is formed in two steps of the first tapered hole 52 and the second tapered hole 53 is that the expansion angle α of the second tapered hole 53 is increased to 130 degrees. Thereby, the ball 55 is effectively crushed.

Next, as shown in FIG.
Are ascending and horizontal movement as indicated by the arrow group, and the conductor layer 12 on the main surface of the base body 9 which is the second bonding point,
That is, the wire 27 is lowered onto the drain conductor layer 14 and the rear end of the loop of the wire 27 having the loop drawn thereon is thermocompression-bonded to the conductor layer 12. At this time, since the capillary 50 is subjected to ultrasonic vibration, the wire 27 crushed on the flat end surface of the capillary 50 is reliably subjected to ultrasonic thermocompression bonding to the conductor layer 12 by the ultrasonic vibration.

Next, the capillary 50 ascends, moves horizontally, and moves to the next first bonding point. Before the capillary 50 is raised from the second bonding point, the clamp mechanism 68 operates to clamp the wire 27. As a result, with the rise of the capillary 50, the wire 27 breaks at the base of the second bonding portion.

Thus, the wire bonding is performed sequentially. As shown in FIG. 2, a single wire 27 is connected to each of the drain wire bonding pad 25 and the gate wire bonding pad 26, but is disposed on both sides of the gate wire bonding pad 26, respectively. Two wires 27 are connected to the source wire bonding pads 28 thus formed. The pitch of the two wires 27 connected side by side is, for example, about 70 μm to 80 μm.

Next, cap sealing is performed on the lead frame 39 on which the wire bonding has been completed. That is,
As shown in FIG. 14, after the cap 8 made of ceramic is placed on the frame 10 of the base 7, a joining material made of silver paste or the like is interposed between the frame 10 and the cap 8. The cap 8 is attached to the base 7 in an airtight manner by the melt hardening of 11.

Thereafter, the leads 3 are separated from the lead frame 39, and the semiconductor device 1 constituting the SHF band low noise GaAs-FET as shown in FIGS. 1 and 2 is manufactured.

According to such an embodiment, the following effects can be obtained.

(1) According to the wire bonding method of the present invention, the ball at the tip of the wire is crushed only by the tapered hole surface of the capillary, and the ball can be crushed only by the tapered hole in the cap. The diameter of the ball is made smaller than before, and the wire is controlled so that the capillary is stopped slightly before the surface of the wire bonding pad so as not to crush the ball with the flat tip of the capillary during wire bonding. As a result of preventing the collapsed portion from protruding from the maximum diameter portion of the tapered hole, the effect that the diameter of the collapsed portion can be reduced to about 60 μm is obtained.

(2) According to the above (1), according to the present invention, the crushed portion due to thermocompression bonding can be reduced to a diameter of about 60 μm.
The effect that it can be reduced to m □ is obtained.

(3) According to (2) above, the SHF band low noise GaAs-F of the present invention
Since the ET can reduce the wire bonding pad size to 65 μm square, the effect of reducing the parasitic input capacitance and achieving low noise can be obtained.

(4) According to the above (2), according to the present invention, the size of the wire bonding pad can be reduced, so that the effect that the chip size can be reduced can be obtained.

(5) According to the above (4), according to the present invention, an effect is obtained that the package size can be reduced from the chip size.

(6) According to (1) to (5), according to the present invention, a synergistic effect that a small SHF band low noise GaAs-FET with small parasitic input capacitance can be provided is obtained.

Although the invention made by the inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments, and various changes can be made without departing from the gist of the invention. Nor. For example, as shown in FIG. 15, when the ball is crushed into the tapered hole 54 of the capillary 50, the deformation caused by the crushing is performed so that the crushed portion does not protrude from the maximum portion of the tapered hole 54. The same effect as in the above-described embodiment can be obtained even if the accommodation portion 77 for accommodating the portion is provided. Also, the tapered holes need not have a multi-stage structure. In this case, the expansion angle of the tapered hole should be widened so that the ball can be reliably crushed.

Further, when the present invention is applied to an IC 78 as shown in FIG. 16, the pitch p of the wire bonding pads 79 in the chip 22 can be reduced. Pitch p
Is the sum of the dimension of the wire bonding pad and the pad spacing for preventing short circuit between the wire bonding pads.
□ and if the pad spacing for preventing short circuit between the wire bonding pads is 30 μm, the pitch p is 90 μm
It can be as small as ~ 95 µm. As a result, in an IC, since the number of wire bonding pads is large, reducing the size of the wire bonding pads has a remarkable effect on reducing the chip size. Therefore, downsizing of the package can be achieved, and downsizing of the IC can be achieved. Especially,
For ICs that require a reduction in parasitic input capacitance, miniaturization of the chip and package is effective in reducing the parasitic input capacitance. In FIG. 16, reference numeral 80 denotes a lead, and 81 denotes a package.

Further, in the above embodiment, a gold wire was used for wire bonding, but a wire other than gold, for example, a copper liner or
The same effect as in the above embodiment can be obtained with other wires such as an Al wire. Further, in the above embodiment, the present invention is applied to the wire bonding by the ultrasonic thermocompression bonding method. However, the present invention can be similarly applied to the wire bonding by the thermocompression bonding method, and the same effect as the above embodiment can be obtained.

In the above description, the case where the invention made by the present inventor is mainly applied to the manufacturing technique of the GaAs-MESFET, which is the field of application as the background, has been described. Applicable to manufacturing technology.

The present invention can be applied to at least a semiconductor device manufacturing technique.

〔The invention's effect〕

The effects obtained by the representative inventions among the inventions disclosed in the present application will be briefly described as follows.

That is, in the manufacture of the semiconductor device by the ultrasonic thermocompression bonding method of the present invention, the maximum diameter portion of the tapered hole at the tip of the capillary is set to 63 μm which is close to the crushed diameter of the ball at the tip of the wire of 60 μm. At the same time, the ball at the tip of the wire having a diameter of 20 μm is crushed at the time of bonding and is filled with a diameter of 40 μm to fill the tapered hole of the capillary.
It is set as small as 50 μm. When bonding, the capillary is 15μ from the surface of the wire bonding pad.
It is stopped at a height of m. Therefore, the ball is crushed by the tapered hole surface of the capillary and is thermocompression-bonded to the wire bonding pad. Absent. As a result, the crushed diameter of the ball at the tip of the wire is about 60 μm, and the wire bonding pad to which the wire is connected is reduced to 65 μm □.
From these facts, when the present invention is applied to the SHF-band low-noise GaAs-MESFET, the parasitic input capacitance can be reduced due to the miniaturization of the wire bonding pad, so that a semiconductor device having excellent high-frequency characteristics can be obtained. In the case of a semiconductor device in which wire bonding pads are arranged side by side, such as an IC, the pitch of the wire bonding pads can be reduced due to the reduction in the size of the wire bonding pads. Miniaturization can be achieved.

[Brief description of the drawings]

FIG. 1 shows an SHF band low noise GaAs-MES according to an embodiment of the present invention.
FIG. 2 is a plan view of a semiconductor device with a cap removed, FIG. 3 is a plan view of a chip that also forms a GaAs-MESFET, and FIG. FIG. 5 is a cross-sectional view showing the structure, FIG. 5 is a plan view showing a lead frame also used for manufacturing a semiconductor device constituting the GaAs-MESFET, FIG. 6 is a plan view showing a state where the base is fixed to the lead frame, FIG. 7 is a partially enlarged bottom view showing the connection state between the base and the lead frame, FIG. 8 is a sectional view of the lead frame in which the chip is fixed on the base, and FIG. Front view showing the main part of a wire bonding apparatus for stretching a wire, FIG. 10 is a cross-sectional view showing the main part of a capillary that also performs wire bonding, and FIG. 11 is also a ball-shaped tip. FIG. 12 is a cross-sectional view showing a main part of a capillary holding a wire, FIG. 12 is a cross-sectional view showing a state in which a ball portion is similarly crushed by a capillary, FIG. 13 is a cross-sectional view showing a wire stretched by a capillary, FIG. Is a cross-sectional view showing a state in which a cap is attached to the base, FIG. 15 is a cross-sectional view showing a main part of a capillary according to another embodiment of the present invention, and FIG. 16 is a semiconductor device according to another embodiment of the present invention. It is a top view which shows the principal part of. 1 ... semiconductor device, 2 ... package, 3 ... lead,
4 ... source lead, 5 ... drain lead, 6 ... gate lead, 7 ... base, 8 ... cap, 9 ... base body, 10 ... frame, 11 ... joining material, 12 ... conductor layer,
13 ... source conductor layer, 14 ... drain conductor layer, 15 ...
… Gate conductor layer, 16… joining material, 17… plated film, 20
... Chip mounting part, 21 ... bonding material, 22 ... chip (semiconductor element), 23, 24 ... wire bonding part, 25 ... drain wire bonding pad, 26 ... gate wire bonding pad, 27 ... ... wires, 28 ... wire bonding pads for sources, 30 ... source electrodes, 31 ...
... Drain electrode, 32 ... Gate electrode, 33 ... Semi-insulating Ga
As substrate, 34 ... buffer layer, 35 ... active layer, 36 ... ohmic contact layer, 37 ... passivation film, 38 ...
… Crushed part, 39 …… lead frame, 40 …… horizontal frame, 41 ……
Vertical frame, 42 Guide hole, 43 Notch, 50 Capillary, 51 Guide hole, 52 First tapered hole, 53 Second tapered hole, 54 Tapered hole, 55 …… ball, 56 ……
Wire bonding pad, 60 ... table, 61 ... bonding unit, 62 ... heat block, 63 ... XY
Table, 64 bonding head, 65 bonding arm, 66, 67 clamp arm, 68 clamp mechanism, 69 support arm, 70 guide, 71 discharge electrode, 72 power supply circuit 73, gas injection tube, 74, gas supply source, 75, gas, 76, heater, 77, housing part, 78
…… IC, 79 …… Wire bonding pad, 80 …… Lead, 81 …… Package.

Claims (1)

(57) [Claims] 1. A method of manufacturing a semiconductor device, comprising fixing a tip of a wire guided in a state inserted into a capillary to a wire bonding pad of a GaAs semiconductor element, wherein a guide hole of the capillary has a first taper toward the tip. A hole portion and a second tapered hole, which are sequentially expanded in two stages. At the tip of the wire, a spherical portion whose diameter is larger than the maximum diameter of the first tapered hole and smaller than the maximum diameter of the second tapered hole is formed. And pressing the spherical portion by a tapered surface of a second tapered hole, and performing thermocompression bonding or ultrasonic thermocompression bonding to the bonding pad at a maximum diameter smaller than the maximum diameter of the second taper hole, Fixing the wire to a bonding pad.