JPS6057220B2 - semiconductor equipment - Google Patents

Abstract

PURPOSE:To improve bonding performance and reliability and to contrive to attain low cost by a method wherein in a semiconductor device on which a semiconductor element is mounted, a gold or gold alloy wire is directly bonded to the base of a substrate for element arrangement. CONSTITUTION:A semiconductor element 104 is mounted by pressure exerted through pressing on an island region 102 of a lead frame 101 composed of a single element of copper or copper alloy. On the upper surface of the semiconductor element 104, Al electrodes 110a, 110b are provided. The end of a gold or gold alloy wire 111a, 111b is bonded to this Al electrode 110a. Another end is directly bonded to lead regions 103a, 103b by full solid solution of Au-Cu. By this method bonding performance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device, and more particularly to a semiconductor device having an improved element mounting base material on which a semiconductor element is mounted and wires connected to electrodes of the element are bonded.

Generally, semiconductor devices having structures shown in FIGS. 1 and 2 are known.

That is, FIG. 1 is a perspective view showing a state in which a silicon semiconductor element (for example, a bipolar semiconductor element) is mounted on an element mounting base material (for example, a lead frame) and further wire-bonded, and FIG. This is a cross-sectional view showing the state after cutting, and numeral 1 in the figure is a lead frame having an island portion 2 on which a semiconductor element is mounted and lead portions 3a and 3b to which wires are bonded. The island portion 2 of this lead frame 1, the lead portion 3a,
A silver layer 4 is coated around the bonding portion 3b. Further, a silicon semiconductor element 6 having base and emitter N electrodes 5a and 5b on the upper surface is mounted on the island portion 2 via a layer 7 mainly composed of gold. Gold wires Ba, 8b are connected to the Al electrodes 5a, 5b of this semiconductor element 6, respectively, and these gold wires Ba, 8b
The other ends are post-bonded to internal leads 3a and 3b which function as base and emitter electrodes, respectively. Further, numeral 9 in the figure is a resin sealing layer that covers the island portion 2 including the semiconductor element 6 and the vicinity of the connection portions of the gold wires Ba and 8b of the lead portions 3a and 3b. Note that the lead portions 3a and 3b exposed from the resin sealing layer 9 are covered with a solder layer 10. By the way, in the semiconductor device described above, the gold wire 8 whose one end is connected to the N electrodes 5a and 5b on the upper surface of the semiconductor element 6 is
a, 8b to the lead portions 3a, 3b of the lead frame 1, conventionally, the lead portions 3a, 3b have a thickness of 2 to 1 mm.
A 0 μm silver layer 4 is coated by plating or the like, and gold wires 8a and 8b are attached to the silver layer 4 at 300°C in air or N2.
A method of post-bonding by heating to a certain degree is used.

However, the above method has various problems as follows.

1. Since the lead portion (post bonding portion) on the lead frame is coated with a silver layer by plating, the number of man-hours required to manufacture the lead frame increases, and since silver itself is expensive, the cost of the lead frame increases.

2. If the silver layer of the lead frame is left in the air, it will sulfurize, and it is difficult to remove it by simple treatment, which deteriorates the bonding properties of gold or gold alloy wires.

Therefore, great care must be taken when storing the lead frame after it has been plated with a silver layer. 3 If the thickness of the silver layer on the lead frame is thin, the underlying metal will oxidize, causing the silver layer to swell and peel.Especially in high temperature and high humidity, the bulge and peeling become even more likely to occur, making wire bonding difficult. Sexuality is significantly reduced.

4. If the lead portion of the lead frame is coated with a silver layer, when bonding gold or gold alloy wire to the electrode on the top surface of the semiconductor element, if a hydrogen torch hits the silver layer on the lead portion, the silver layer will be removed. Not only is the layer portion oxidized, but the underlying metal is also oxidized, impairing the bonding properties of the wire.

5 When a semiconductor device with a structure in which gold wire is post-bonded to the silver layer on the lead part of a lead frame is operated for a long time in a high temperature atmosphere, water droplets will adhere to the electrodes (lead parts) of the lead frame, and water droplets will adhere to the electrodes (lead parts) of the lead frame. silver begins to melt,
A so-called migration phenomenon occurs, and silver is deposited on the other lead portion, causing a short circuit between the two saws 1 with silver, which significantly impairs reliability.

6 When automating the manufacturing process from thin metal sheets to products, it is difficult to automate the process because a silver plating process is required.

7 When the lead portions of a lead frame are coated with a silver layer by partial plating in order to reduce the amount of silver used and reduce costs, directionality occurs in the lead frame.

8. When manufacturing a lead frame from a thin metal plate using a press or the like, defects in the plating of the silver layer are detected and removed during the press, reducing the movability of the press.

Note that the above-mentioned problems are the same even when a stem is used instead of a lead frame as the element mounting base material.

The present invention was made in order to solve the above various problems all at once, and does not cover the post-bonding part of the element mounting base material with a silver layer, and instead uses the base material of the base material (copper or copper alloy alone). The present invention aims to provide a semiconductor device in which gold or gold alloy wire is directly bonded to the semiconductor device.

Next, an embodiment of the present invention will be described with reference to FIGS. 3 and 4.

Figure 3 is a perspective view showing, for example, a bipolar semiconductor element mounted on a lead frame and wire bonding a performed, and Figure 4 shows the semiconductor device after resin sealing and cutting. be.

In the figure, reference numeral 101 denotes an island portion 102 on which a semiconductor element is mounted and a lead portion 103a on which wire bonding is performed.
, 103b is a lead frame made of simple copper. In addition, 104 in the figure is a vanadium layer 105 with a thickness of about 600 mm on the mounting surface, and a vanadium layer 105 with a thickness of about 200 mm, as shown in FIG.
0A nickel layer 106, 1.0 μm thick gold/germanium (Gll2Wt%) alloy layer 107, and 100 μm thick gold/germanium (Gll2Wt%) alloy layer 107.
This semiconductor element 104 is a bipolar silicon semiconductor element in which gold layers 108 of 0A are sequentially laminated, and as shown in FIG. Mounted by heating and pressing with (forming gas). In other words, the semiconductor element 104 is
Au-G containing no silicon of the semiconductor element 104
- It is mounted via a bonding layer 109 made entirely of a solid solution of Cu. Further, base and emitter A1 electrodes 110a and 110b are provided on the upper surface of the semiconductor element 104, and one ends of gold wires 111a and 111b are connected to these N electrodes 110a and 110b, respectively, in a reducing atmosphere (
For example, bonding is performed using H2-N2 forming gas). And these gold wires 111a, 111
The other end of b is a lead portion 103 that functions as the base and emitter electrode of the lead frame 101 made of copper alone.
A and 103b are bonded to each other in a reducing atmosphere (for example, H2-N2 forming gas). In other words, the other ends of the gold wires 111a and 111b are joined to lead portions 103a and 103b made of copper alone using a solid solution of Au-Cu. Furthermore, the island portion 102 and lead portion 103a of the lead frame 101 including the semiconductor element 104
, 103b where the gold wires 111a and 111b are connected are covered with a resin sealing layer 112. In addition, the resin sealing layer 11
A solder layer 113 is coated on the leads (shown in the figure) of the island portion exposed from 2 and the lead portions 103a and 103b. Note that the above-described semiconductor device can be manufactured, for example, by the method shown below. First, a thin copper plate is pressed to produce a lead frame made of copper alone.

Next, on the mounting surface of the silicon substrate on which a plurality of Npn bipolar transistors were formed, a layer of Vanadium 1 with a thickness of about 600A was added, and a nickel layer with a thickness of about 2000A, and a layer of nickel with a thickness of 1
．． After successively vacuum-depositing a 0 μm gold/germanium (Gel2Wt%) alloy layer and a 1000A thick gold layer, the silicon substrate was deposited from its upper surface (the surface opposite to the mounting surface).
The semiconductor element 104 shown in FIG. 5 is produced by cutting with a diamond scribe or a blade dicer scribe. Note that these semiconductor elements are stored covered with vinyl chloride or the like. Next, the lead frame is H2-N
2 forming gas. 370~ in (reducing atmosphere)
While heated to 400'C, the semiconductor element was heated to 50 to 80°C without applying vibration to the island part of this lead frame.
Mount by pressing with a weight of 0y. After that, one end of the gold wire is bonded to the A1 electrode of the mounted semiconductor element in the above-mentioned forming gas atmosphere, and the other end of the gold wire is bonded to the lead part of the lead frame made of pure copper at an angle of 300 to 350° in a reducing atmosphere. After post-bonding with C and further resin sealing, the extended lead portions and the like are immersed in a solder bath and soldered to produce the semiconductor device shown in FIG. According to the present invention, the gold wires 111a and 111b, one end of which is connected to the A1 electrodes 110a and 110b on the upper surface of the semiconductor element 104, are connected to the lead portions 103a and 103b of the lead frame 101 made of pure copper using Au-C.
Since it is possible to obtain a semiconductor device that is well bonded through the solid solution of u, it has various effects listed below.

(1) There is no need to cover the lead frame with a silver layer, and since it is made of copper (or copper alloy) alone, the process can be shortened by omitting the silver plating process, and the lead frame can be manufactured at low cost.

(2) Since there is no need to coat the lead frame with a silver layer, it is possible to eliminate the disadvantages of silver, such as a decrease in wire bonding strength due to silver sulfurization and oxidation of the base under the silver layer, and prevent the lead frame from being carefully stored and mounted. The wire can be firmly joined to the lead part of the lead frame without any precautions.

(3) Since the wire bonding part of the lead frame is not coated with a silver layer, even if the semiconductor device is operated for a long time in a high-temperature atmosphere, short circuits between the electrode lead parts due to silver migration phenomenon can be eliminated, improving reliability. can be significantly improved.

(4) Even if the hydrogen torch hits the lead part of the lead frame when bonding the gold wire to the electrode on the top surface of the semiconductor element, the lead part is not covered with a silver layer, so the silver layer will not cover it. Wire bonding and ink can be bonded and inked well without causing oxidation or deterioration of the lead portion due to oxidation or deterioration.

When bonding this gold wire, using a reducing gas (for example, a forming gas containing about 10% H2) will prevent the hydrogen torch from extinguishing, and will also reduce the oxidation of the copper that makes up the lead part of the lead frame, resulting in good bonding properties. Become. (5) The bonding layer formed by bonding a gold wire to the lead portion of a lead frame made of simple copper is a solid solution of gold and copper in a total proportion and does not form an intermetallic compound.

Therefore, since no intermetallic compound is formed in the bonding layer, it is possible to obtain a highly reliable semiconductor device with low electrical resistance, chemical stability, and no deterioration in mechanical strength. Further, although copper, which is a constituent material of the lead frame, is easily oxidized, the bonding layer becomes a precious metal by diffusion or melting of gold, and becomes resistant to oxidation. Furthermore, even when heated and oxidized in air, the gold diffuses and the noble metal layer becomes wider, so oxidation of the bonding layer does not occur. (6) Since the plating process for coating the lead frame with a silver layer can be omitted, reliability tests for the silver layer (tests for blistering, peeling, plating thickness, and plating defects) of the silver layer are no longer necessary, and Automation during the manufacture of semiconductor devices becomes easy, cleaning after press processing becomes easy, and a high-precision lead frame without directionality caused by coating with a silver layer can be obtained.

Additionally, oxidation due to local battery generation does not occur during cleaning of the lead frame. Note that the semiconductor device according to the present invention is not limited to the case where a lead frame made of copper alone is used as in the above embodiment, but may be constructed from a single copper alloy such as Cu-Sn, Cu-Zn, or phosphor bronze.

As for the wire, a gold alloy wire may be used instead of the gold wire. Further, the semiconductor device according to the present invention is not limited to the structure in which a gold (or gold alloy) wire is bonded to a lead frame made of copper (or copper alloy) alone, as in the above embodiment, but also has a structure in which a lead frame made of copper (or copper alloy) alone is bonded. You may also bond wires to the

Further, the semiconductor device according to the present invention has vanadium, nickel, gold/germanium, etc. on the mounting surface as shown in the above embodiment.
The semiconductor element is not limited to a structure in which a semiconductor element made of four metal layers of gold is laminated and mounted on an island part of a lead frame made of simple copper. It may also be mounted on an island portion coated with a silver base material via an alloy.

In other words, in the semiconductor device of the present invention, the element mounting base material to which the gold or gold alloy wire is bonded must be made of copper or a copper alloy alone, and a silver layer may be applied to the mounting portion of the semiconductor element as necessary. It may be coated. As detailed above, according to the present invention, a gold or gold alloy wire is coated on the base material (single copper or copper alloy) of the base material (copper or copper alloy alone) without coating the post-bonding part of the element mounting base material with a silver layer. Direct bonding provides a semiconductor device that has the effects of excellent bonding performance listed in (1) to (6) above, low cost, and high reliability.

[Brief Description of the Drawings] Figure 1 is a perspective view showing a silicon semiconductor element mounted on a lead frame, and the element and the leads of the lead frame are connected with gold wires, and Figure 2 is the same view as Figure 1. 3 is a cross-sectional view showing a semiconductor device after the lead frame is resin-sealed and cut; FIG. 3 is a perspective view of a silicon semiconductor device according to an embodiment of the present invention mounted and bonded to the lead frame; FIG. This figure is a sectional view showing the semiconductor device after the lead frame shown in FIG. 3 has been sealed with resin and cut, and FIG. 5 is a sectional view showing the semiconductor device shown in FIG. 3 before being mounted. 101...Lead frame made of copper alone, 1
02...Island part, 103a, 103b...
・Lead part, 104... Bipolar silicon semiconductor element, 109... Bonding layer, 110a, 1
10b...Al electrode of base and emitter, 111a
, 111b... Gold wire, 112...
Resin sealing layer.

Claims (1)

[Claims] 1. An element mounting base material made of a single piece of copper or copper alloy;
Using a four-layer brazing material in which a semiconductor element having an electrode on its upper surface, a gold layer, a gold, germanium alloy layer, a Nitzgul layer, and a vanadium layer are laminated in this order, the semiconductor element is placed on the base material. is mounted in a reducing atmosphere with the gold layer on the base material side and the vanadium layer on the semiconductor element side, and the element mounting base material and the electrode of the semiconductor element are mounted on the gold layer. Or a semiconductor device characterized by being connected in a reducing atmosphere using gold alloy wire.