Taking on the stable supply of rare materials

The TANAKA Precious Metals Group has a long history of participating in the semiconductor products business, dating back to the 1960s. It began with the supply of gold wires for transistors, which have electrical conductivity, high chemical stability, and are easy to process. Today, the Group boasts the world’s leading share in the supply of semiconductor bonding wires, including copper and aluminum products.

As demand for semiconductors continues to increase, producing regions and quantities of minerals used as raw materials for precious metals are limited. Only a collective of precious metal professionals like the Group can supply the required precious metal materials in the required quantities and in a timely manner.

In addition, since materials are rare in the precious metal materials supply chain, it is essential to have a production and distribution system that keeps recycling in mind. Precious metal recycling is one of the Group’s core businesses, and the Group is promoting the global deployment of its recycling bases. “A system to recycle precious metal components from production scraps generated in the manufacturing process and semiconductors that are no longer useful in the market has always been a prerequisite for us as a company that handles rare materials,” says Tsutomu Yamashita, who oversees bonding wire development at TANAKA Electronics Co., Ltd. The company also offers gold bonding wires made of 100% recycled materials in response to recent social needs. It is genuinely a top runner in the materials recycling field.

While wire technology in the area of general-purpose chips is in the mature stage, the introduction of new technology for power semiconductors is essential. In the past, aluminum wire, which is inexpensive and can form thicker wiring, was often used for large currents, but with the commercialization of SiC (silicon carbide)-based devices and their increased heat resistance, thicker copper wires are now being used.

In bonding wires, reliable wire connections are important. Depending on the material, hardness or softness may be required, and the material may need to be forged for ease of use while leveraging its characteristics. The Group has established a system to develop and supply wires that meet customer needs with its proprietary technology and know-how.

Bonding wire

Mounting materials and bonding wires that are widely used in general-purpose chips for volume production

Bonding wire is a conductive wire that connects electrodes on semiconductor chips to lead frame packaging. Since the dawn of the semiconductor industry, gold wire has been primarily used, but currently, palladium-coated copper wire is being utilized, except for applications such as multilayer memory and packages for automobiles. In recent years, mounting technologies other than wire bonding, such as bumps, have come to be used for cutting-edge chips, but wire bonding is still widely used for general-purpose chips. Demand for wire continues to increase at several percent per year.

Supporting the evolution of semiconductors with the power of precious metals

On the other hand, there are expectations for new utilizations of precious metals, given the evolution of cutting-edge chips shortly.

The width of the finest wiring to be formed on a 1.4 nm node chip would be 10 nm or less, and the introduction of ruthenium wiring is also under consideration in place of copper wiring, which has been used until now. With the miniaturization of wiring, there are growing expectations for ruthenium, which has lower specific resistance and is less prone to diffusion phenomena that cause degradation in high-temperature environments during operation.

The TANAKA Precious Metals Group develops and supplies precursors, which are materials that form ruthenium thin films using the CVD (chemical vapor deposition) and ALD (atomic layer deposition) methods. The Group’s proprietary product, TRuST, has exceptionally high vapor pressure, enabling the formation of high-quality ruthenium thin films with uniformity and high coverage in narrow, deep grooves on the chip. “Each semiconductor manufacturer has its methods and conditions for the film formation process, and the specifications required for precursors vary widely. It is important to work closely with partner companies and production equipment manufacturers to bring the products to completion. We have been developing precursors and accumulating technologies for over 20 years. With the recent evolution of semiconductors, we feel that the time has come for our technologies to come into full fruition in society,” says Hirofumi Nakagawa of TANAKA Precious Metal Technologies Co., Ltd.

Ruthenium is a much rarer precious metal than gold or platinum. Moreover, the ratio of the amount effectively used to the amount input during the precursor production process and film formation process is small. The company has established technologies to recover and reuse ruthenium and can provide total solutions.

“In the semiconductor industry, which is constantly transforming both in terms of technology and business, we believe it is most important to respond to market trends quickly and accurately. We will continue to make proposals that can only be made by a group of precious metal professionals while sensing the demands of the times and reliably listening to feedback from customers,” says Naoko Abe of TANAKA Holdings Co., Ltd. The Group’s presence in the semiconductor industry seems likely to continue to grow.

Precursor

Indispensable for the miniaturization of chip wiring
Reaction precursor in the film formation process that is indispensable for the miniaturization of chip wiring

The Precursor is a substance that takes part in the film formation process or other chemical reaction to produce a target substance. In the film formation process using methods such as CVD and ALD, a liquid precursor of an organometallic compound is gasified and introduced into a chamber, where it is decomposed by heat, plasma, oxygen gas, hydrogen gas, etc. , with other materials introduced simultaneously or with substances on the film formation surface, causing a metallic reaction that forms a thin film. Oxygen, hydrogen, etc. are used as reaction gases to accelerate the reaction. The formation of thin films for wiring requires the use of precursors with high vapor pressure following gasification, which enables thin films to be formed uniformly in fine, deep grooves.

Tsutomu Yamashita (right), who oversees bonding wire development at TANAKA Electronics Co., Ltd., Hirofumi Nakagawa (center), who oversees precursor development at TANAKA Precious Metal Technologies Co., Ltd., and Naoko Abe (left), who is General Manager of the Corporate Communications & Advertising Department at TANAKA Holdings Co., Ltd.

This article is a reprint of an article advertisement that has been published in the Nikkei xTECH (PR) since November 25, 2024, with permission from Nikkei Business Publications.