JP3522048B2 - Bonding wire - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding wire used for connecting a chip electrode of a semiconductor element and an external lead, particularly for a multi-pin semiconductor device. The present invention relates to a suitable high-strength bonding wire. [0002] In order to connect an electrode of a semiconductor element such as ICILSI and an external lead, generally 0.01 to
0. A bonding wire having a diameter of 1 mm is used. Bonding wires are required to have good electrical conductivity, good bondability with chips and external leads, and environmental resistance in the use atmosphere.
Pure metals such as l, Au, Cu or alloys thereof have been used. However, in recent years, semiconductor packages using a resin are frequently used from the viewpoint of cost reduction, and Au-based wires having excellent environmental resistance are most frequently used. Conventionally used Au-based bonding wires include elements such as Ca and Be, for example, 0.000.
In many cases, a gold alloy wire having a purity of 99.99 wt% or more added with 1 to 0.0 l wt% is used. However, in recent years, with the increase in the number of pins of semiconductor devices, the pitch between bonding wires has been reduced and the bonding distance has been increased. When used, the strength of the device is weak, so the wire loop may sag, or when the resin is sealed, the bonding wire deforms due to the flow resistance of the resin, causing the bonding wires to contact each other. The problem of lowering occurred. In general, the additive element may be increased in order to improve the strength of the wire.
As shown in Japanese Patent No. 454, Japanese Patent Publication No. 62-23455, etc., when a large amount of noble metal elements such as Pt and Pd is added to increase the strength, the conductivity of the wire is greatly reduced. Therefore, it is not always suitable as a wire for a multi-pin package. In view of the above, an object of the present invention is to provide a high-strength bonding wire suitable for a multi-pin semiconductor device. To achieve the above object, the bonding wire of the present invention has a purity of 99.99 wt.
% Of high purity gold, 0.05 to 2 wt% of total amount of one or more kinds of Co or Ni, 0.05 to 1.2 wt% of Ge
It was made to contain. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the bonding wire of the present invention, one or more of Co or Ni and Ge are added to Au in a composite manner because the compound of Co or Ni and Ge is contained in Au. This is because the fine precipitation allows the strength to be improved without significantly reducing the conductivity. This fine precipitate has the same effect when both Co and Ni are added together with Ge alone or when Co and Ni are added together with Ge at the same time. If the total amount of one or more of Co or Ni or the addition amount of Ge is less than 0.05 wt%, the amount of precipitates is too small and the effect of improving the strength is insufficient. Conversely, C
If the total amount of one or more of o or Ni exceeds 2 wt%, the conductivity decreases, and if the added amount of Ge exceeds 1.2 wt%, a eutectic of Ge and Au is generated and the workability of the wire is reduced. It drops significantly. Therefore, the total amount of one or more of Co or Ni is 0.05 to 2 wt%, and the addition amount of Ge is 0.05 to
It is necessary to be 1.2 wt%. In order to fully exhibit the effects of the present invention, it is preferable to add by selecting the ratio of Co and Ge in the vicinity of 1: 1 and the ratio of Ni and Ge in the vicinity of 2: 1. The essence of the invention is Co or / and Ni,
Although it is in the strengthening by addition of Ge, within a range where various properties such as conductivity are not degraded, 0.01% or less of Be,
Ca, Sr, Ba, Y, Ga, In, Sn, 2% or less of Cu, Ag, or Pt group elements may be added. In order to sufficiently bring out the characteristics of the wire of the present invention, it is desirable to perform a solution treatment before the wire drawing and to anneal in order to effectively precipitate a compound phase of Co or Ni and Ge. As an annealing condition, an annealing temperature of 200
˜400 ° C. and annealing time of about 0.5 to 5 hours are preferable.
Note that this annealing is not necessarily performed before wire bonding, and can be performed together with the chip after wire bonding as long as the chip is not damaged. Since the strength of the wire is not increased, wire bonding with less chip damage is possible, and there is also an advantage in using the wire that wire bonding can be performed under conditions close to those of conventional soft wires. Thus, even when the wire is reinforced by annealing after wire bonding, high wire deformation prevention performance is sufficiently exhibited and the characteristics of the wire of the present invention are not impaired. EXAMPLES High purity gold and C having a purity of 99.999 wt%
o A gold alloy having the composition shown in Table 1 was melt cast using a mother alloy containing 1 to 20% of o, Ni or Ge. The obtained ingot was subjected to a solution treatment at 750 ° C. for 30 minutes, and then subjected to rolling and drawing to obtain a bonding wire having a diameter of 20 μmφ. These wires were heat treated to adjust the characteristics and obtain bonding samples. [Table 1] The wire strength of these bonding samples was determined by a tensile test. About electroconductivity, it evaluated by measuring a specific resistance by direct current | flow 4-terminal method. Bonding bondability between the bonding wire, the electrode of the semiconductor element, and the external lead is 30 stage temperature.
Use a wedge bonding machine set at 0 ° C to hook a hook to the wire bonded by ultrasonic thermocompression bonding, and when a tensile test is performed, if the cut occurs in the wire part, The case where it occurred at the joint was evaluated as “bad”. The time-dependent change in bonding bondability was evaluated by holding a sample wire-bonded by the same method as described above at 200 ° C. for 100 hours and then performing a similar pull test. As for the deformation of the wire when encapsulating the resin, an epoxy resin is molded with a molding machine under the conditions of a mold temperature of 180 ° C. and an injection pressure of 100 kg / cm ² with respect to a sample which is wire-bonded at intervals of 5 mm by the same method as described above. The amount of wire flow was determined from an X-ray photograph taken with an X-ray transmission device and evaluated. The wire flow amount is the deformation amount of the wire when molded with an epoxy resin. Table 2 shows the results of the above evaluation. [Table 2] As is clear from Table 2, the bombing wire of the present invention has a higher strength and a smaller wire flow rate than the conventional bonding wire. Further, as shown in the comparative example, it can be seen that the specific resistance is smaller than that of the wire strengthened by adding a large amount of noble metal. When the addition amount of Co, Ni and Ge is less than 0.05 wt%, sufficient wire strength cannot be obtained, and the addition amount of Co or Ni is 2 w.
It can be seen that the specific resistance increases when it exceeds t%.
For samples in which the amount of Ge added exceeds 1.2 wt%, breakage occurred frequently, and the wire could not be drawn to a predetermined wire diameter. According to the present invention, it is possible to obtain a bonding wire suitable for a multi-pin semiconductor device, which is less likely to cause a contact failure between wires at the time of assembling a semiconductor device and has good conductivity.

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Claims (1)

(57) [Claims] [Claim 1] A high purity gold having a purity of 99.99 wt% or more and one or more of Co or Ni in a total amount of 0.05 to 2w.
A bonding wire containing t% and 0.05 to 1.2 wt% Ge.