JPH03291340A - Copper alloy extra fine wire for semiconductor device and semiconductor device - Google Patents

Abstract

PURPOSE:To improve the reliability at a high temp. as a copper alloy extra fine wire for a semiconductor device and the reliability against the change in temp. by incorporating a trace amt. of Fe, Al and Mg into high purity oxygen free copper. CONSTITUTION:In a copper alloy extra fine wire used as a bonding wire for a semiconductor device, oxygen free copper having high purity of >=99.9999wt.% is incorporated with each 0.1wt.ppm of Fe and Ag and 0.5 to 400ppm Mg. The added Fe and Ag improve the corrosion resistance in the joined part of a wire with an Al alloy wiring film by the coexistence with Mg without increasing the hardness of the copper. Even in the contraction of a package or the like in accordance with the change in temp., the generation of cracks in its heat affected zone can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides bonding and
When used as a wire, the bond between the AQ alloy wiring film on the Si chip and the wire has high corrosion resistance and is resistant to thermal cycles.It is a copper alloy ultra-fine wire for semiconductor devices and a harsh environment that is subjected to thermal cycles. The present invention relates to a semiconductor device that has high durability at high temperatures and can be used even when swallowed.

[Conventional technology]

Conventionally, semiconductor devices generally include transistors, ICs,
Further, LSIs and the like are known, and among these, for example, the following is one of the methods for manufacturing ICs.

(a) First, as a lead frame material, plate thickness: 0°I
A Cu alloy strip having a thickness of ~0.3zx is prepared.

(b) From this lead frame material, a lead frame that matches the shape of the IC to be manufactured is formed by etching or press punching.

(C) Next, a Si chip is thermally bonded to a predetermined location on the lead frame using a conductive resin such as Ag paste, or an Au film is formed on one side of the Si chip and the lead frame in advance.

Soldering or Au brazing is performed through a plating layer made of Ag, Ni, Cu, or an alloy thereof.

(d) Ball bonding is performed across the Si chip and the lead frame using an Au ultrafine wire having a diameter of 20 to 100 μl as a bonding wire.

(e) Subsequently, the Si chip, the bonding wire, and the portion of the lead frame to which the Si chip is attached are sealed with resin for the purpose of protecting them.

(f) Finally, each interconnected portion of the lead frame is cut out to form an IC.

A method consisting of the main steps (a) to (f) above is known.

As mentioned above, ultrafine Au wires are used as bonding wires in the manufacture of semiconductor devices, but in recent years, inexpensive high-purity oxygen-free copper ultrafine wires have been attracting attention in place of the expensive Au ultrafine wires. It has become.

[Problem to be solved by the invention]

By the way, when using ordinary high-purity oxygen-free copper ultrafine wires as bonding wires for semiconductor devices, it is common to perform thermocompression bonding using ultrasonic waves. It has been considered undesirable to add elements to the bonding wire material and harden it, as there are problems such as microcracks occurring in the Si chip itself on the side to be crimped depending on the bonding wire material.

However, with advances in bonding technology, Si chips have been manufactured that allow bonding and are resistant to breakage even if the hardness of the ball part hardens slightly, making it possible to add a larger amount of additive elements than before. ing.

In addition, recently, reliability requirements for semiconductors have become stricter, requiring them to be used at high temperatures, which were not previously possible, and under severe temperature changes. Currently, there are problems such as the formation of local batteries at the junction with the film and the occurrence of cracks in the heat affected zone of copper alloy ultrafine wires due to shrinkage of packages, wires, etc. caused by temperature changes.

[Means to solve the problem]

Therefore, from the above-mentioned viewpoint, the present inventors conducted intensive research to develop a copper bonding wire that improves reliability under high temperatures and against temperature changes, and as a result, the following findings were made. I ended up getting this.

In other words, Fe, which has been considered an impurity element in steel,
and Ag are other impurity elements, especially Se, Te
, S, etc., each contains 0.1 ppm or more and less than 3°0 ppu by weight without increasing the hardness of copper, and coexists with Mg of 0.5 ppm or more and less than 400 ppu by weight. This dramatically improves the corrosion resistance at the joint between the wire and the AI2 alloy wiring coating, and also greatly reduces the occurrence of cracks in the heat-affected zone when the package shrinks due to temperature changes.

This invention was made based on the above findings, and
High purity oxygen-free copper of 99.9999% by weight or more, containing Fe and Ag of 0.1 weight PPm or more and less than 3.0 weight PPm, respectively, and Mg of 0.05 weight ppm or more, 40
A copper alloy ultrafine wire for a semiconductor device characterized by containing less than 0 ppm by weight, and a semiconductor device using this copper alloy ultrafine wire as a bonding wire.

In addition, in the copper alloy ultrafine wire of this invention, the content of Fe and Ag as alloy components is each 0.1 pp by weight.
m or more, less than 3.0 weight PPm, Mg content is 0
．． The reason for setting the content to be 5 ppm or more and less than 400 ppm by weight is that if these contents are less than the above specifications, corrosion resistance at the joint between the wire and the Aρ alloy wiring coating will be reduced when semiconductor devices are put into practical use at high temperatures. PP with an Fe and Ag content of 3.0 wt.
If Mg exceeds 400 wt.m, the ability to form a ball at the tip of the wire during wire bonding will deteriorate in the coexistence with Mg, and if Mg exceeds 400 wt. This is based on the reason that wire bonding becomes difficult even to C and l chips, which are large and have a structure that is difficult to break.

Second, the copper to which these alloy components are added is 99°999
The reason for specifying 9% by weight or more is that S, Se, Te, etc., which are unavoidable impurities in copper, not only increase the hardness, but also avoid the decrease in corrosion resistance that occurs in conventional copper bonding wires. Furthermore, this is because the metals that were previously removed as impurities in steel,
This is because it is necessary to control the content of Fe and Ag to 0.1 ppm or more and less than 3.0 ppm by weight.

[Effect]

In the copper alloy ultrafine wire for semiconductor devices and the semiconductor device of this invention, Fe and AX are each added at 0.1 weight and 1 p.
p ta or more and less than 3.0 ppm by weight, and M
By containing 0.5 weight ppm or more and less than 400 weight ppm of Even when a package or the like shrinks, the occurrence of cracks in the affected area can be greatly reduced.

[Implementation]

Next, one embodiment of the present invention will be described.

First, regular electrical steel is used as a raw material, and after repeated electrolytic refining, elements that easily form compounds with S, Se, Te, etc. (such as La) are added, and zone refining is performed to obtain a 99% .9999% or higher purity oxygen-free copper is produced.

Subsequently, this high-purity oxygen-free copper is melted in a vacuum melting furnace,
In addition, as shown in Table 1, Fe and A
g to 0.1 weight ppi or more and 3.0 weight ppi, respectively.
+ less than 0.5 weight pp1 or more of cutlet M g, 400
It is cast with a content of less than ppm by weight, and then subjected to hot part and cold wire drawing under normal conditions,
Copper alloy ultrafine wires No. 1 to 8 according to the present invention each having a diameter of 25 μm were manufactured, respectively.

For comparison, Comparative Examples Nos. 1 to 4 were manufactured in which the amount of added elements was different from that of the copper alloy ultrafine wire of the present invention.

Next, pole bonding was performed using the various copper ultrafine wires No. I = 12 mentioned above to a Si chip having a structure that is difficult to break by bonding and has an AQ alloy wiring film, and the ability to form balls and the occurrence of micro cracks were investigated. Ta.

Further, semiconductor devices manufactured using these wires were left at a high temperature of 250° C., and the number of connection failures was measured after 30 hours. Furthermore, a heat cycle test was conducted at -65°C to 150°C, and the number of defects after 500 cycles was measured.

These results are shown in Table 1.

Margin below From the results shown in this table, in the copper alloy ultrafine wire of the example of the present invention, only one micro crack occurred in No. 7, and no problems occurred in the reliability test. do not have. If this level of microcracking occurs, it can be avoided by adjusting the bonding conditions. Comparative example N
In No. 099, no improvement in reliability was observed due to the small amount of Mg added, and in No. 10.11, F
Since the contents of e and Ag were not appropriate, the coexistence effect with Mg was not sufficient, and no improvement in reliability was observed.
Furthermore, microcracks also occur due to the poor ball forming ability. In No. and +2, the amount of Mg was too large and the balls were hardened, resulting in many microcracks.

〔Effect of the invention〕

As explained above, the copper alloy fine wire for semiconductor devices of the present invention has good ball-forming ability within the hardness range that allows bonding, and provides highly reliable bonding even under high temperatures and environments with severe temperature changes. Department can be secured.

In addition, in a semiconductor device using the above-mentioned ultra-thin wire as a bonding wire, accidents such as the bonding portion between the wire and the AI2 alloy wiring sheath 4 being corroded and disconnected due to the formation of local batteries can be prevented, and even under the adverse effects of high temperatures, It also has high durability, and even in environments with severe temperature changes, it prevents accidents such as cracks occurring in the heat-affected zone of the wire and disconnection due to shrinkage of the package, wire, etc.

Claims (2)

[Claims] (1) High purity oxygen-free copper of 99.9999% by weight or more,
3. Fe and Ag each at 0.1 ppm or more by weight;
A copper alloy ultrafine wire for a semiconductor device, characterized in that it contains less than 0 ppm by weight, and 0.5 ppm or more and less than 400 ppm by weight of Mg. (2) A semiconductor device characterized in that the ultrafine copper alloy wire for semiconductor devices according to claim 1 is used as a bonding wire.