TWI415957B - Gold - platinum - palladium alloy lap line - Google Patents

Abstract

[Problem] To provide a gold-platinum-palladium alloy bonding wire for vehicle-mounted semiconductors, which exhibits excellent reliability in the connection with aluminum pads, while being highly reliable when left at high temperatures even in cases where an epoxy resin containing no halogen substance is used, thereby capable of maintaining the electrical characteristics after being left at high temperatures. [Solution] A gold-platinum-palladium alloy bonding wire which contains 0.4-1.2% by mass of platinum, 0.01-0.5% by mass of palladium, 10-30 ppm by mass of aluminum and 10-60 ppm by mass of calcium and/or magnesium in total, with the balance made up of gold having a purity of 99.999% by mass or more.

Description

Gold-platinum-palladium alloy wiring

The present invention relates to a gold-platinum-palladium alloy tie wire suitable for use in connection between a substrate of an IC wafer of a semiconductor device and an external conductor, and the like, particularly for use in an environment where a vehicle or a high-speed device is used in a high temperature environment. The halogen-free epoxy resin is sealed with a gold-platinum-palladium alloy.

A gold alloy wire connecting an IC wafer electrode and an external wire to a semiconductor device that is required to have high bonding reliability for automotive use is a gold-palladium having a purity of 99% by mass of palladium of 0.5 to 1.2% by mass in high-purity gold. Excellent reliability of the alloy wire is widely used. Such a gold alloy wire is connected to a pure aluminum pad or an aluminum alloy pad on the electrode of the IC wafer by ultrasonic bonding using a thermocompression bonding method, and the other end is connected to an external wire on the substrate, etc., and then the joint is closed. The oxygen resin is sealed and becomes a semiconductor device. Such a pure aluminum or aluminum alloy pad is usually formed by vacuum evaporation or the like.

The environmental conditions in which the semiconductor component for a vehicle is used are higher in the engine room of the automobile or in the vicinity thereof than in a normal use environment. In the case of a high-bond long-term test (HTS), a pure gold wire composed of gold having a purity of 99.99% by mass or more is known to have a higher bonding reliability when a high-strength gold-palladium alloy bonding wire is used. Sex. For example, it is necessary to withstand 2,000 to 4,000 hours at 175 °C. In such a mounting environment, it is important to ensure the bonding strength of the gold-palladium alloy wire and the pad electrode portion for a long period of time. As such a lap The wire is made of gold containing 0.5 to 0.7% by mass of palladium, 0.1 to 0.3% by mass of platinum, and 99.99% by mass or more of the other, and a gold alloy wire for a high temperature semiconductor device having a metal or alloy pad of aluminum. (Required item 1 of Patent Document 1) is composed of gold containing 0.5 to 0.7% by mass of palladium, 0.1 to 0.3% by mass of platinum, and 99.999% by mass or more of the other, and having a high temperature of a metal or alloy pad of aluminum. In the case of using a gold alloy wire for a semiconductor device (claim 1 of Patent Document 2) or a halogen-containing epoxy resin as a sealing resin, the gold alloy fine wire contains 0.005 to 0.5% by weight of manganese and contains palladium 0.005. 1.0% by mass and platinum 0.01 to 2.0% by mass further contain at least one of calcium, lanthanum and rare earth elements in a total range of 0.0005 to 0.05% by weight (Received item 5 of Patent Document 3).

In recent years, epoxy sealing resins containing no halogen substances have been used for environmental reasons. In the high-temperature long-term test in the case of using this epoxy sealing resin, the high-bonding gold-palladium alloy bonding wire of the former has not performed better than the bonding reliability of the 99.99 mass% gold bonding wire. Even the gold-palladium alloy wire is less reliable than the pure gold wire.

Further, in the automotive IC package, the semiconductor device is generally shielded from high temperature for a long time without resin sealing, and is subjected to a tensile test after being placed at 175 ° C for 1000 hours. When such an unsealed high-temperature long-term test is carried out, the high-bonding is caused by the high-bonding of the interface between the first bonding portion and the aluminum pad at an early stage from the high-bonding gold-palladium alloy bonding wire. Reliability is lower than pure gold.

Previous high-bonding gold-palladium alloy wire by adding palladium to platinum Further, the diffusion of the gold-aluminum joint portion at the interface of the aluminum pad is suppressed, and the generation of the intermetallic compound which causes deterioration of the joint portion of the molten ball is suppressed. However, if the generation of the intermetallic compound is suppressed, the diffusion of gold and aluminum in the gold-aluminum joint portion is suppressed too much, so that the joint strength due to diffusion cannot be sufficiently ensured, and the interface is caused at the gold-aluminum joint portion. Deterioration. In such a case, the gold-palladium alloy is used for the wiring, and in fact, the semiconductor component of the vehicle-mounted IC package or the epoxy resin which does not contain a halogen substance has not been put into practical use.

[Patent Document 1] Japanese Patent Laid-Open No. 09-321075

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2011-155129

[Patent Document 3] Japanese Patent Laid-Open No. Hei 10-303239

It is an object of the present invention to provide a gold-platinum for semiconductors which is excellent for use in a semiconductor device which is sealed by a resin in an excessively harsh environment such as high temperature, high humidity and high pressure, and which has excellent connection reliability with an aluminum pad. Palladium alloy is used for wiring.

Further, an object of the present invention is to provide an aluminum pad which is highly reliable in high temperature for a long period of time even when an epoxy resin containing no halogen substance such as bromine is used, and which can maintain the electrical characteristics after standing at a high temperature for a long period of time. A gold-platinum-palladium alloy wiring for semiconductors with excellent reliability and excellent reliability.

In the present invention, platinum contained in the gold is more expensive than palladium as a main element, and contains not more than 1% by mass, and palladium is contained as a minor element containing 0.5% by mass or less, and the gold pad interface is moderately suppressed. - When the aluminum bonding portion is diffused and the epoxy resin containing no halogen substance is used, the generation or growth of the intermetallic compound which causes deterioration of the bonding portion of the molten ball is suppressed. In the past, the bonding wire containing about 1% by mass of palladium in gold was too much to suppress the diffusion of the joint with the aluminum pad. Therefore, in the case of high temperature long-term test (HTS), especially in the case of using halogen-free substances. In the case of an epoxy resin, it is presumed to cause deterioration of the bonding wire at the interface of the aluminum pad.

Further, the inventors of the present invention added a trace amount of aluminum to the aluminum pad, and simultaneously added calcium or magnesium to be finely dispersed in the gold-platinum-palladium alloy matrix, and moderately inhibited the diffusion of the gold-aluminum joint portion at the interface of the aluminum pad. Improve the mechanical properties of the wire and improve the roundness of the crimp ball. The mechanical properties or roundness characteristics of the bonding wires are further improved by adding a rare earth element such as cerium or lanthanum or cerium.

One of the gold-platinum-palladium alloy wiring wires for semiconductor elements for solving the problems of the present invention contains platinum 0.4 to 1.2 mass%, palladium 0.01 to 0.5 mass%, aluminum 10 to 30 mass ppm, calcium or magnesium. At least one of the total of 10 to 60 ppm by mass and the balance of gold having a purity of 99.999% by mass or more.

Further, another gold-platinum-palladium alloy wiring for a semiconductor element which solves the problem of the present invention contains platinum 0.4 to 1.2% by mass and palladium 0.01~. At least one of 0.5% by mass, aluminum 10 to 30 ppm by mass, calcium or magnesium is 10 to 60 ppm by mass, and at least one of cerium and rare earth elements is 1 to 30 ppm by mass in total, and the rest is A wire composed of gold having a purity of 99.999 mass% or more.

(gold-platinum-palladium alloy)

The gold-platinum-palladium alloy of the present invention is a completely homogeneous solid solution alloy composed of gold of 0.4 to 1.2% by mass of platinum, 0.01 to 0.5% by mass of palladium, and gold having a purity of 99.999% by mass or more.

In the present invention, platinum is the main element, and palladium is used as a secondary element in order to appropriately control the diffusion speed of gold and aluminum at the joint portion of the pure aluminum pad or the aluminum alloy pad to suppress the bonding at high temperature for a long time. Deterioration of the interface.

Therefore, platinum is used in an amount of 0.4 to 1.2% by mass, and palladium is used in an amount of 0.01 to 0.5% by mass. Preferably, the total amount of platinum and palladium is from 0.6 to 1.3% by mass.

Individually, platinum is 0.4 to 0.8% by mass, palladium is preferably 0.05 to 0.4% by mass, platinum is 0.5 to 0.7% by mass, and palladium is preferably 0.1 to 0.3% by mass. The platinum/palladium ratio is preferably in the range of 2 to 4, and more preferably in the range of 2.5 to 3.5.

Further, in the present invention, the remaining gold having a purity of 99.999 mass% or more is intended to further exhibit a trace amount of an additive element such as aluminum or calcium or magnesium by limiting the amount of unavoidable impurities to a maximum of less than 10 ppm by mass. effect.

In the present invention, aluminum is made 10 to 30 ppm by mass.

In general, aluminum forms an intermetallic compound with gold, so is it not? Used in the elements of pure gold wire or gold-platinum alloy wire. However, in the gold-platinum-palladium alloy wiring of the present invention, the mechanical strength of the bonding wires is improved, and the tensile strength of calcium or magnesium is maintained at a high tensile strength even when placed at a high temperature for a long period of time.

When the aluminum is less than 10 ppm by mass, the above effect cannot be exhibited, and if the aluminum exceeds 30 ppm by mass, the roundness of the crimped ball is deteriorated. Therefore, the range of aluminum is 10 to 30 mass ppm. The preferred range of aluminum is from 16 to 24 ppm by mass.

In the present invention, at least one of calcium or magnesium is 10 to 60 ppm by mass in total.

As an additive element of the lap joint, it is generally considered that calcium and magnesium are elements which improve the mechanical strength of the lap joint and the roundness of the crimped ball. In the gold-platinum-palladium alloy wire of the present invention, by multiplying the effect with aluminum, calcium will increase the mechanical strength of the bonding wire, and magnesium will improve the roundness of the crimping ball of the bonding wire.

However, when at least one of calcium or magnesium is less than 10 ppm by mass in total, the above effects are not exhibited. When the total amount exceeds 60 ppm by mass, the mechanical strength of the bonding wire becomes too strong, and the aluminum pad is destroyed. Therefore, at least one of calcium or magnesium is 10 to 60 ppm by mass in total. It is preferable to add 10 to 30 mass ppm of calcium and magnesium in total, and it is preferable to add 16 to 24 mass ppm in total.

In the present invention, at least one of cerium or a rare earth element is in the range of 1 to 30 ppm by mass.

Tantalum or rare earth elements are generally considered to be elements that increase the mechanical strength of the bonding wires. In the gold-platinum-palladium alloy wiring of the present invention, by The synergistic effect of aluminum and calcium or magnesium, lanthanum or rare earth elements will increase the mechanical strength of the lap joint, and at the same time increase the roundness of the crimp ball during the first bond.

It is preferred to add ~1 to 20 ppm by mass and 1 to 60 ppm by mass of the rare earth element. The rare earth element is preferably 1 to 30 ppm by mass or 1 to 30 ppm by mass, and more preferably 1 to 30 ppm by mass and 1 to 30 ppm by mass.铍6~14 mass ppm and 镧1~30 mass ppm and 铈1~30 mass ppm combination, 铍1~20 mass ppm and 镧10~30 mass ppm and 铈1~30 mass ppm, or 铍1~ The combination of 20 mass ppm and 镧1~30 mass ppm and 铈10-30 mass ppm is better, and the combination of 铍6-14 mass ppm and 镧10-30 mass ppm and 铈10-30 mass ppm is better. The combination of 6~14 mass ppm and 镧14~26 mass ppm and 铈14~26 mass ppm is the best.

As described above, the gold-platinum-palladium alloy of the present invention has a good bonding property between the molten ball and the pure aluminum pad or the aluminum alloy pad, and the roundness of the crimping ball can be ensured, and further, even at a high temperature. The pores of the joint interface of the first joint are not coarsened and developed, and the stability of the joint can be ensured, and the tensile strength is also high. Further, the bonding wire formed of the gold-platinum-palladium alloy of the present invention does not cause deterioration of the bonding interface of the first bonding even when the epoxy resin containing no halogen substance is left for a long time at a high temperature. The effect of not deteriorating the electrical connection.

[Examples]

The gold-platinum-palladium alloy (gold purity: 99.9999% by mass or more) having the composition shown in the left column of Table 1 was melt-cast, and the vacuum was subjected to a heat-blown heat treatment, followed by continuous stretching until a final wire diameter of 20 μm. A gold-platinum-palladium alloy bonding wire (hereinafter referred to as "the wire of the present invention") 1 to 27 according to the present invention having a wire diameter of 20 μm was produced by wire, and was used in comparison with the composition range not entering the present invention. The gold-platinum-palladium alloy wire and the former gold-palladium alloy wire (hereinafter, collectively referred to as "comparative wire") 28 to 36.

The wire strength was measured for the wires 1 to 27 of the present invention and the comparative wires 28 to 36. Then, a wire holder (trade name: Max μm ultra) manufactured by Kulicke & Soffa was placed on a 70 μm square aluminum alloy pad made of aluminum-0.5 mass% copper alloy mounted on a semiconductor IC wafer to produce a target air ball of 40 μm ( FAB), lapped with heating temperature: 200 ° C, loop length: 5 mm, loop height: 220 μm, crimp ball diameter: 48 μm, crimp ball height: 14 μm, and evaluated for the difference in roundness . Next, after standing at 175 ° C for 1,000 hours, the tensile test was performed on the bonding wires. Further, the bonded sample was resin-sealed at 175 ° C for 4,000 hours, and then the electrical resistance was measured.

[Method for evaluating wire strength]

For each alloy composition, a 100 mm long sample was stretched at a speed of 10 mm/min using a TENSILON tensile tester (type UTM-2). Determine the strength at the time of destruction. The number of measurements was 5 points, and the average value was evaluated. The results of these evaluations are shown in the right column of Table 1.

[Evaluation method of the true roundness of the crimping ball]

For each of the alloy compositions, the length of the X-direction (direction perpendicular to the application of the ultrasonic wave) and the Y direction (the direction in which the ultrasonic wave was applied) of the crimping ball when the number of the crimping balls was 100 was measured for the IC wafer for evaluation, and the ratio was evaluated. The results of these evaluations are shown in the right column of Table 1.

〔Tensile Strength〕

For each alloy composition, a dedicated IC chip was bonded by a wire holder, and a tensile test was performed on the "Universal Joint Tester 4000 Series" manufactured by Dage Corporation at 100 points using a tensile test at a position directly above the first bond. Determination. Thereafter, the same bonded sample was allowed to stand at 175 ° C for 1,000 hours, and then the tensile strength was measured again at 100 points. The tensile strength was evaluated for the decrease in tensile strength after the high-temperature placement and the peeling of the first joint portion. The evaluation results of the tensile strength are shown in the right column of Table 1.

〔resistance〕

For each alloy composition, a dedicated IC wafer was bonded by a wire holder, and a sample for resistance measurement was produced using a halogen-free epoxy resin (manufactured by Nitto Denko Co., Ltd., product name: GE-7470C). The resistor is made of KEITHLEY company called "SonrceMeter" Formula 2004) is carried out using a dedicated IC holder and a dedicated measurement system. The measurement method was carried out by a so-called DC four-terminal method.

The resistance was measured for 100 pairs of external wires (200 plugs) before being placed at a high temperature for 4,000 ° C for 4,000 hours. When the resistance is increased by more than 20% in comparison with the high temperature, it is considered that a failure has occurred and the failure rate is evaluated. The evaluation results of the resistance are shown in the right column of Table 1.

The products No. 1 to No. 7 are related to the invention of claim 1, and the products No. 8 to No. 27 are related to the invention of claim 2, and the products No. 2 and No. 23 to No. 27 are According to the invention of claim 3, the implements No. 11, No. 13 to No. 16, and No. 20 to No. 27 are inventions related to claim 4, and the implements No. 13 to No. 16 and No. 20~No.27 is related to The invention of claim 5, and the implements No. 15, No. 20, and No. 25 to No. 27 are related to the invention of claim 6. In the right column of Table 1, the wire strength shows the strength measurement results: ◎ is about 83.4 N (8.5 gf) or more, ○ is about 68.6 N (7.0 gf) or more, Δ is about 53.9 N (5.5 gf) or more, and × is about 53.0N (5.4gf) or less.

In the right column of Table 1, the crimp ball is rounded, showing the ratio of the pressure-bonded ball diameter X to Y, X/Y, ◎ 0.95 to 1.05, ○ 0.9 to 1.10, △ 0.8 to 1.2, and × 0.79 or less. 1.21 or more.

In the right column of Table 1, the tensile strength is the amount of decrease in tensile strength and the peeling of the first joined portion, ◎ is about 0 to 9.8 N (0 to 1.0 gf), and ○ is about 10.8 to 19.6 N (1.1~). 2.0gf), Δ is about 20.6 to 39.2 N (2.1 gf to 4.0 gf), × is about 40.2 N (4.1 gf) or more, and peeling occurs in the first joint portion.

In the right column of Table 1, the incidence of resistance failure is ◎, 0%, ○ is 0.1 to 5.0%, Δ is 5.1 to 30.0%, and × is 30.1% or more.

As can be seen from the results shown in the right column of Table 1, the wire of the present invention has high wire strength, good roundness of the crimped ball, no reduction in tensile strength after long time of high temperature, and epoxy resin containing no halogen substance. In the case where the high temperature is left for a long time, the increase in resistance is not observed, and the comparative wires 28 to 36 have at least one of at least one of these characteristics.

[Industrial use possibility]

The bonding wire of the present invention has a semiconductor use for sealing a halogen-free epoxy resin used in an environment where a vehicle or a high-speed device is used in a high temperature environment.

Claims (7)

A gold-platinum-palladium alloy bonding wire characterized by containing 0.5 to 0.7 mass% of platinum, 0.1 to 0.3 mass% of palladium, 10 to 30 mass ppm of aluminum, and at least one of calcium or magnesium up to 10 to 60 The mass ppm and the rest are gold having a purity of 99.999 mass% or more. A gold-platinum-palladium alloy bonding wire characterized by containing 0.4 to 1.2 mass% of platinum, 0.01 to 0.5 mass% of palladium, 10 to 30 mass ppm of aluminum, and at least one of calcium or magnesium up to 10 to 60 At least one of the mass ppm, the lanthanum and the rare earth element is composed of a total of 1 to 30 ppm by mass and the balance of 99.999% by mass or more. The gold-platinum-palladium alloy wire of the first or second aspect of the patent application, wherein the calcium or magnesium contains 10 to 30 ppm by mass of calcium and 10 to 30 ppm by mass of magnesium. The gold-platinum-palladium alloy wire of the second aspect of the patent application, wherein the lanthanum or rare earth element contains lanthanum 1 to 20 mass ppm and at least one of the rare earth elements amounts to 1 to 30 ppm by mass. By. The gold-platinum-palladium alloy bonding wire according to item 2 of the patent application, wherein the cerium or rare earth element contains at least one of 铍1 to 20 ppm by mass, 镧1 to 30 ppm by mass or 铈1 to 30 ppm by mass. For example, the gold-platinum-palladium alloy wire of the second aspect of the patent application includes the bismuth or rare earth element containing 铍1-20 mass ppm, 镧1-30 mass ppm, and 铈1-30 mass ppm. Gold-platinum-palladium alloy lap joint as claimed in claim 1 or 2 a wire in which the aforementioned bonding wire is used for halogen-free epoxy resin sealing.