JPH01127635A - Fine au alloy wire for bonding semiconductor device - Google Patents

Abstract

PURPOSE:To improve the heat resistance of a fine Au alloy wire for bonding and the strength at ordinary temp. and high temp. and to stabilize loops by incorporating a specified amt. of one or more among La, Ce, Pr, Nd and Sm and a specified amt. of Ge and/or Be into the Au alloy wire. CONSTITUTION:The compsn. of a fine Au alloy wire for bonding a semiconductor device is composed of 0.2-2.5ppm one or more among La, Ce, Pr, Nd and Sm, 1-15ppm Ge and/or Ge and the balance Au with inevitable impurities. The Au alloy has superior heat resistance and strength at high temp. and ordinary temp. The Au alloy wire can form stable loops of large and nearly uniform height at the time of bonding, and the deformation of the loops by the effect of heat in a bonding stage and the flowing of the loops by the effect of heat in a subsequent resin molding stage can be inhibited.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has excellent room temperature and high temperature strength as well as excellent heat resistance, and has a
When used for bonding (connection) between semiconductor elements and external leads, the loop height is high, the variation in height is small, there is no formation of deformed loops, and the loop flow during resin molding is small. Au that can eliminate defects such as edge shorts.
This relates to fine alloy wires.

[Conventional collision]

Generally, when assembling semiconductor devices.

(a) First, the tip of the Au or Au alloy filament supplied through the bonding capillary is heated and melted electrically or with a hydrogen flame to form a ball.

(b) A solid ball is heated to 150 to 300° C. and bonded (ball bonded) by pressing it with a capillary to an electrode on a semiconductor element.

(C) Next, move the capillary onto the external lead while forming a loop.

((1) Attach the capillary to 11PL on the external lead.

Join the other end of the loop to this (wedge bond).

(e) Next, pinch the thin wire and pull it upward.

Cut this.

The above steps (a) to (e) are one step, and this is repeated repeatedly to bond the semiconductor element and the external leads.This can be done manually or automatically. Bonder is used.

[Problem that the invention seeks to solve]

On the other hand, recent advances in semiconductor technology have resulted in semiconductor devices becoming more highly integrated, faster to assemble, more diverse in product shape, and forced to be used under harsher conditions.
Along with this, the speed of bonding has increased, the density of semiconductor devices has increased, and package shapes have become more diverse. It has become necessary to perform bonding at high speeds, but the high-purity Au thin wires and thin Au alloy wires used in the past have insufficient loop height, and there are large variations in loop height. The current situation is that the formation of unstable loops is unavoidable, and as a result, new serious loop-related problems are occurring, such as contact with the edges of semiconductor devices and making edge shorts more likely to occur. , so the loop height is high.

There is a strong demand for the development of a thin wire for bonding semiconductor elements that has small variations in height, does not form deformed loops, and has less loop flow during resin molding.

[Means for solving problems]

Therefore, the inventors of the present invention, etc., from the above-mentioned viewpoint.

As a result of our research to develop a thin wire for bonding semiconductor devices that can speed up bonding and support the high density and diversification of semiconductor devices, we have developed a thin wire for bonding semiconductor devices.

Lai or 2a or more of La, Ce, Pr, Nd, and Sm (hereinafter collectively referred to as Ce group rare earth elements) = 0.2 to 2.5 ppm.

One of Ge and Be or 2fi:l~15p
When composed of an Au alloy containing pm* and having a composition in which the remainder consists of Au7 unavoidable impurities, this Au alloy has excellent room temperature and high temperature strength, as well as excellent heat resistance.
Furthermore, during bonding, it is possible to form a high loop, and it is also possible to suppress loop deformation due to the heat effect of the bonding process and the occurrence of loop flow due to the subsequent heat effect of the resin mold. I gained knowledge.

This invention was made based on the above findings.

One or more of Ce group rare earth elements 20.2
~2.15ppH 1° of Go and Be [or 2 strokes: l ~15P
The present invention is characterized by an Au alloy thin wire for semiconductor device bonding, which is made of an Au alloy having a composition containing .ms and the remainder consisting of Au and unavoidable impurities.

Next, the reason why the component composition of the Au alloy thin wire of the present invention is limited as described above will be explained.

(a) Ce group rare earth element These components include fine wire normal and high temperature strength.

Furthermore, it has the effect of improving heat resistance and preventing loop deformation and flow due to heat effects, but the content is 0.2
If the content is less than ppm, the desired effect cannot be obtained, while if the content exceeds 2.5 ppm.

Since it becomes impossible to secure the desired high loop height, the content should be reduced to 0.2 to 2.5 ppm (0,000 ppm).
It was set as 02~O, OOO25 heavy fi [%).

(b) Ge and Be These components have the effect of ensuring a high loop height and reducing variations in loop height when co-contained with a Ce group rare earth element at 1%.

If the content is less than 1 ppm, the desired effect cannot be obtained, whereas if the content exceeds 15 ppm, variations in the loop height will occur.
Its content is 1-%-15ppm (0,0001-0
．． 0015 weight/shortness%).

〔Example〕

Next, the Au alloy thin wire of the present invention will be specifically explained with reference to examples. After making V4 molten Au alloy having the composition shown in Table 1 by a usual melting method and casting, By rolling using a groove rolling mill and subsequently performing wire drawing, at least any of the constituent components of the present invention Au alloy thin A1-35 having a diameter of 0.02 s and a comparative deviation are obtained. Ingredients (marked with * in Table 1)
has a composition outside the scope of this invention.

Next, let's talk about the nine polar thin lines obtained as a result.

A high-temperature tensile test was conducted under conditions corresponding to the conditions to which the thin wire is exposed during bonding, that is, the temperature was maintained at 260° C. for 20 seconds, and the breaking strength and elongation were measured.

In addition, these thin wires are used as bonding wires,
Bonding was performed using a high-speed automatic bonder, and the loop height, variation in loop height, presence or absence of deformation of /I/-, and wire flow rate after resin molding were measured. Show the results of these measurements in Table 1.

As shown in the front view in Fig. 1, the loop height is determined by measuring h when the semiconductor element 8 and the external lead L are bonded with a thin @W using a two-axis micrometer. The variation in the loop height is expressed by finding the standard deviation of the 80 loop height measurements mentioned above and expressing it by the value of 3σ. In this case, practically h: 2
It is required that the current is 50 μm or more and the variation is 30 μm or less.

In addition, the presence or absence of loop deformation is determined by the connection 4IW after bonding.
was observed using a microscope, and as shown by the dotted line in FIG.
It was judged as "present" if there was an edge short (short edge), and "absent" if there was no contact.

Furthermore, the loop flow rate is determined by the connection after resin molding (thin 4
1W) from directly above, and based on the resulting X@photograph, measure the maximum amount of dust in the connection for direct 1IPc connecting the bonding points of the semiconductor element and external lead at some of the four corners, and Expressed as an average value.

In this case, the maximum loop flow rate is 100 μmt.
is acceptable.

〔Effect of the invention〕

From the results shown in Table 1, the present invention Au alloy thin wires 1 to 35
They all have high high temperature strength, excellent heat resistance, high loop height and extremely small variation, no loop deformation, and very little loop flow. On the other hand, as seen in Comparative Au and Au Alloy Fines 1I11 to 24, if the lid containing at least one of the constituent components is out of the scope of the invention, at least one of the above characteristics may be lost. It is clear that the quality is inferior.

As mentioned above, the Au alloy thin wire of the present invention has excellent high-temperature strength, high room-temperature strength, and excellent heat resistance. Even when high-speed bonding is used when assembling semiconductor devices, it is possible to stably form a loop with a high height and extremely small variation in height, and there is almost no deformation of the loop. It has industrially useful properties such as the occurrence of defects such as short circuits and edge shorts is significantly suppressed, resulting in high reliability.

[Brief explanation of the drawing]

! Figure 441 is a front view showing the bonding shape. S...Semiconductor element, L...External lead. W...Thin line.

Claims (1)

[Claims] One or more of La, Ce, Pr, Nd, and Sm: 0.2 to 2.5 ppm; One or two of Ge and Be: 1 to 15 ppm
1. A thin Au alloy wire for semiconductor device bonding, characterized in that it is made of an Au alloy having a composition of: m, and the remainder consisting of Au and unavoidable impurities.