JPS62290835A - Au-alloy extra fine wire for semiconductor device bonding wire - Google Patents

Abstract

PURPOSE:To obtain an Au-alloy extra fine wire for semiconductor device bonding wire particularly excellent in strength at high temp. and heat resistance, by providing a composition containing one or more kinds among Ce-group rare earth elements, Se, and Pb each in the prescribed percentage. CONSTITUTION:The above Au-alloy extra fine wire is composed of an Au alloy consisting of, by weight ratio, 0.0001-0.003% of one or more kinds among Ce-group rare earth elements constituted of La, Ce, Pr, and Sm, 0.0005-0.003% Se, 0.002-0.008% Pb, and the balance Au with inevitable impurities. The Au- alloy extra fine wire combines superior strength at ordinary and high temps. with superior heat resistance and, moreover, it is excellent in joining strength. Accordingly, when used as bonding wire for semiconductor device the Au-alloy extra fine wire is capable of preventing the deformation of wire loop at the time of bonding no matter how high-speed the bonding operation is made, and semiconductor device is made highly concentrated and large-sized and, moreover, owing to its superior wire drawability, it can easily be worked into an extra fine wire of <=0.05mm diameter.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] This invention provides an ultrafine Au alloy wire that has high strength, particularly high temperature strength, and has excellent heat resistance. Particularly when this is used as a bonding wire for semiconductor devices, it can prevent deformation of wire looseness during wire bonding, as well as wire flow and wire neck breakage during resin molding.
This relates to ultrafine u-alloy wires.

[Conventional technology]

Conventionally, in general, semiconductor devices such as engineering C+LSI are manufactured using (a,) First, the lead material is plate thickness: 0.1-
Prepare a strip of Cu and Cu alloy or N1 and Nj gold alloy with a thickness of about 0.3 mm, (b) Then, press punch the above lead material to form a lead suitable for the shape of the semiconductor device to be manufactured. Forming a frame, (C) High-purity $1 at predetermined locations on the lead frame.
Alternatively, a semiconductor element such as Del is heat-bonded using a conductive resin such as AgR-st, or Au is plated on one side of the lead material in advance.

(d) Wire bonding (connection) using ultrafine pure Au wires across the semiconductor element and the lead frame; (e) Pulling. Next, in order to protect the semiconductor element, the wiring, and the part of the lead frame to which the semiconductor element is bonded, resin molding is performed using plastic, and (f) the interconnected parts of the lead frame are cut out. fg) Finally, the legs of the lead material are coated and welded with a solder material for connection to the substrate of the semiconductor device. In particular, the wire bonding in the above step (d) is performed using a manual or automatic bonding machine.
A bonding wire made of ultra-fine wire is cut using an oxyhydrogen flame or electrically, and the ball portion at the tip formed at that time is heated to a temperature of 150 to 350 degrees Celsius for each of the semiconductor element and lead frame. This is done by pressing on the surface of the

[Problem that the invention seeks to solve]

As mentioned above, ultrafine pure Au wires are used as bonding wires in the manufacture of semiconductor devices, but recent improvements in bonding technology have led to increased speeds, higher integration density, and economic efficiency. Therefore, bonding wires are also required to have strength, especially high-temperature strength and heat resistance.However, the above-mentioned pure Au ultrafine wires lack particularly high-temperature strength, so it is difficult to manufacture the above-mentioned semiconductor devices. During wire bonding in step (d) in the process, deformations such as ``sagging'' and ``sagging'' that cause short circuits in the wire loops are likely to occur, and due to lack of heat resistance,
Similarly, at the time of resin molding in step (e) above, wire flow and wire neck breakage, which also cause short circuits, are likely to occur, and the above requirements cannot be satisfied at present.

[Means for solving problems]

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to develop a bonding wire with particularly excellent high-temperature strength and heat resistance. (Hereinafter, ``chi'' indicates weight%)
, 5°・°1・2′・ゞ°・3 and °°”ra”1z9f
)1. One or more of the earth elements: O,
0OO1~0.003%, Be: 0.0005~0.003%, Pb, 0003
~0008%, while maintaining the excellent wire drawability and bonding strength of pure Au ultrafine wires, the strength, especially high temperature strength and heat resistance, is significantly improved, and as a result of this, Au When ultra-fine alloy wire is used as a bonding wire, the deformation of the wire loop during bonding is prevented despite the increase in bonding speed and the increase in the density and size of semiconductor devices. They found that flow and wire neck breakage were significantly suppressed.

This invention was made based on the above findings, and includes one or more of the cerium group rare earth elements consisting of La, Ce, Pr, Nd, and Sm:
0.0OO1~0003%, Be: 0.0005~0.003%, Pb: 0.0
03 to 0.008%, with the remainder consisting of Au and unavoidable impurities.
In particular, the present invention is characterized by ultrafine Au alloy wires for bonding wires of semiconductor devices, which have excellent high-temperature strength and heat resistance.

Next, the reason for limiting the component composition range as described above in the Au ultrafine wire of the present invention will be explained.

(a) Cerium Group Rare Earth Elements These components, in the coexistence of Be and Pb acid components, have the effect of suppressing coarsening of crystal grains and improving high-temperature strength during heating during bonding and resin molding. If its content is less than 0.0001%, the desired effect cannot be obtained;
．． If it exceeds 0.003%, embrittlement will appear and the wire drawability will deteriorate, so the content was determined to be O,OOOl~0,OO3%.

(b) se and Pb These components have the effect of improving heat resistance when they coexist with the cerium group rare earth elements, but even if the Be content is less than 0.0005%, the Pb Even if the content is less than 31% O, OO, the desired heat resistance cannot be secured, while for Be, the content exceeds 3% O, OO3, and for Pb, the content exceeds 0.0% O8%. If the content increases, not only will the drawing blade tend to become brittle and the Loe properties of the wire drawing blade will deteriorate, but also the grain boundary fracture will easily occur at the heating temperature during bonding. , respectively Be: 0.0005 to 0.00
3%, Pb: 0.003-0, ooschi.

〔Example〕

Next, the Au alloy ultrafine wire of the present invention will be explained with reference to Examples.

By preparing a molten metal having the component composition shown in Table 1 by a normal melting method, casting it, rolling it using a known groove rolling mill, and subsequently performing wire drawing. Au alloy ultrafine wires 1 to 13 of the present invention, comparative A and u alloy ultrafine wires 1 to 4, and conventional pure Au ultrafine wires each having a diameter of 0.025 mm were manufactured.

In addition, comparative Au alloy ultrafine wires 1 to 4 all contain one of the constituent components (components marked with * in Table 1).
It has a composition in which the content of is slightly outside the scope of the present invention.

Next, the resulting ultra-fine wires were subjected to room temperature tensile tests to measure the breaking load and elongation, and were further tested under conditions equivalent to those to which the wires are exposed during bonding, that is, at a temperature of 250°C for a period of 308°C. The high-temperature breaking load was measured at six strips, and using these ultra-thin wires as bonding wires, the bonding was carried out at 3.5 u.
0.1 over a long pumping distance (usually 2 tom)
This was carried out at a high speed of 8 seconds (normal speed is 0.23 seconds) to measure the bonding strength with the semiconductor element, the presence or absence of loop deformation, and the amount of wire flow after resin molding.

The wire flow rate was determined by taking an X-ray photograph of the wire (connection) after resin molding from directly above, and connecting the bonding points of the semiconductor element and lead frame at some of the four corners based on the resulting X-ray photograph. The maximum amount of wire expansion with respect to a straight line was measured, and the average value of these values was expressed.

〔Effect of the invention〕

From the results shown in Table 1, the Au alloy ultrafine wires 1 to 1 of the present invention
No. 13 has much higher strength, especially high-temperature strength, than conventional pure Au ultra-fine wires, so there is no loop deformation during wire bonding, and the bonding strength is equivalent to that of conventional pure Au ultra-fine wires. Moreover, since it has excellent heat resistance, there is very little wire flow after resin molding, whereas conventional pure Au ultrafine wires have had significant loop deformation and wire flow.

Furthermore, as seen in Comparative Au Alloy Ultrafine Wires 1 to 4, if the content of any of the constituent components is too low to be within the scope of the present invention, at least one of the above characteristics is inferior. It is clear that it will become a thing.

As mentioned above, the Au alloy ultrafine wire of the present invention has excellent room temperature and high temperature strength, excellent heat resistance, and also has excellent bonding strength, so it was used as a bonding wire for semiconductor devices. In some cases, deformation of wire loops during bonding is prevented, and even wire flow and wire neck breakage are significantly suppressed during resin molding, despite faster bonding and higher density and larger semiconductor devices. It has become highly reliable and has excellent wire drawability, making it easy to process into ultra-fine wires with a diameter of 0.05mx or less, making it an industrially useful wire. It has characteristics.

Claims (1)

[Claims] One or more cerium group rare earth elements consisting of La, Ce, Pr, Nd, and Sm: 0.000
1 to 0.003%, Be: 0.0005 to 0.003%, Pb: 0.003 to 0.008%, and the remainder is Au and unavoidable impurities (weight%). An ultrafine Au alloy wire for bonding wires of semiconductor devices, characterized in that it is made of an alloy.