Technic Taiwan Co., Ltd.

Gold plating is used for many applications that require good electrical, thermal, and mechanical properties. For example, gold plating is used for a variety of bonding applications due to gold’s corrosion resistance and mechanical properties. In flip-chip and chip-scale packaging applications, the under bump metal (UBM) stack has gold as a final surface finish. In bonding applications, the electrical and thermal properties of gold make it useful for backside and via plating on power amplifiers used in cell phone applications. The majority of these applications require a soft, pure gold process.

Sulfite gold processes are the preferred plating chemistries in the semiconductor industry. Legacy cyanide gold plating solutions that are high in toxicity are being phased out for safer, more environmentally responsible products. The problem is traditional sulfite gold solutions also have inherent weaknesses. The sulfite complex is not as strong and the cyanide complex making the solution less stable. The high pH of sulfite gold can make the chemistry incompatible with some photoresist, presenting costly problems with the bath and adhesion. Another significant problem is the short bath life of sulfite gold processes making operating costs much higher than cyanide gold systems. Finally, while sulfite gold solutions are cyanide-free, they still present toxicity concerns because of their use of arsenic or thallium as grain refiners.

Technic’s Elevate Gold 7990 NBV HT eliminates all the inherent weaknesses of traditional sulfite gold processes. Because Elevate Gold 7990 NBV HT operates at a pH of 6.3, it is compatible with all photoresists. At this pH, the deposit is bright, negating the need for toxic metallic grain refiners. The acidic pH extends the bath life by allowing the bath to be able to produce optimum results at high specific gravity levels. A proprietary stabilizer dramatically increases the stability of the solution throughout the life of the bath.

Benefits

• Reduced cost of operation through:

- Extended bath life which significantly reduces the number of bath makeups per year

- Stable electrolyte eliminates scrap produced from bath plate-out

- Excellent coplanarity and step coverage resulting in less gold used per wafer

- High-speed plating increases wafer production capabilities • Free of cyanide, thallium, and arsenic making it safe for operators and environmentally responsible.

• For use in plating tools from manual wet bench and R&D to fully automatic production lines.

• One of the most widely used and reliable sulfite gold chemistry in the semiconductor industry.

As the semiconductor industry continues to push for higher reliability, power, and overall increase in performance the properties of legacy solders like tin-silver can no longer meet these requirements. One alternative that is becoming the high-performance solder of choice is eutectic gold-tin. Gold-tin has many desirable properties compared to other solders as compaired in Table A.

The tensile strength and shear strength of gold-tin is much higher than other solders making it a much more reliable bond for high power applications that require long-term reliability. Although indium has higher thermal conductivity than gold-tin, the high Young’s modulus of gold-tin allows the material to be deposited much thinner than indium and maintain a consistent flatness over a large area.

There are several methods for applying gold-tin: solder paste, solder preform, evaporation, plating by layers, and alloy plating. Of all these methods, alloy plating has been determined to be the most efficient and cost-effective. In addition, alloy plating is not limited by feature size or configuration.

Elevate® AuSn 8020 is a one-step cyanide-based process formulated to deposit a eutectic or near eutectic gold-tin alloy. The alloy ranges from 75 – 82% gold content with a corresponding melting point of 280 oC – 320 oC.

Features

• One step, single bath process

• Capable of producing various alloys

• Simple to use and easy to control process • Produces predictable and consistent gold-tin alloys

• Produces alloys with excellent reflow performance

Benefits

• Reduces cost by being able to deposit on selective areas compared to evaporation processes that must deposit on the full wafer.

• Reduces cost by having the capability of producing a pure gold flash layer on top of the gold-tin alloy with the same chemistry. Eliminates the need to add an extra gold bath after the gold-tin process.

• Technology enabling chemistry. Unlike preforms, the chemistry is not feature size or deposit thickness limited.

The semiconductor industry utilizes nickel as a barrier layer and a hard mask. Nickel is crucial for metal stacks that include copper-like Cu/Ni/Au, Cu/Ni/Sn to prevent the migration of copper into the rest of the stack, and thereby contaminating the deposits. For hard-to etch substrates like SiC and LiNbO3, nickel is used as a hard mask, because of its high selectivity.

Traditional nickel plating solutions utilize boric acid as a buffering agent. New regulations and guidelines identify boric acid as problem in two essential areas:

Toxicity: Boric acid is classified as a toxin for reproduction (May impair fertility or cause harm to an unborn child.)

Low Water Solubility: Boric acid concentration in a nickel solution is typically 40 g/l. Because of boric acid’s low solubility in water, an effective liquid replenisher can be challenging. Additions have to be made by dissolving boric acid powder in heated water before adding it to the tank. This method has caused incomplete dissolution of the boric acid resulting in redeposit on the wafers.

Technic Elevate® Ni 5950 eliminates both of these problems by being boric acid free and by being comprised of all liquid components, thereby eliminating any solubility issues. Elevate® Ni 5950 produces nickel deposits equal to or better than deposits utilizing boric acid.

Features

• Boric acid free

• All liquid components

• Very stable electrolyte

• Improved coplanarity compared to typical nickel solution

• Low-stress semi-bright deposit

• Optimum deposit up to 10 ASD

• Versatile - can be used in all types of applications requiring nickel

Benefits

• Safer for production enviroment for operators

• Easy implementation/replenishment of the buffer component.

• Cost effective - eliminates downtime associated dissolving boric acid in the working bath.

• Can be used in a standard plating tool without any modifications.

The Semcon Fountain is the latest development in the highly successful Semcon series of wafer plating tools by Technic. Expanding on the popularity of the Semcon 1000 single wafer processing for R&D and small scale production, the Semcon Fountain offers more options and features with a patented chamber design and solution sparger that more closely resembles a full-scale production environment. The Semcon Fountain’s unique design also orients the wafer in the more favorable horizontal position, mimicking most of the semiconductor mass production electroplating tools. The Semcon Fountain is capable of processing wafers up to 300 mm with specially designed wafer mounts.

Through the use of interchangeable wafer plating cups, fabricated to specific wafer sizes. Optimum plating results can be achieved by configuring the process for each application by adjusting the sparger, solution flow, shielding, and more. Each, diameter specific, wafer cup allows for maximum flexibility at a low cost by being able to run different wafer sizes using one plating cell.

The Semcon Fountain is ideal when setting up an electroplating process for the first time or when introducing a new metal plating bath to an already existing electroplating process.

Features

• Can be used for several different applications on a variety of substrates including Si, GaAs, InP and others.

• The horizontal orientation of the wafer allows for ease of transition to a mass production fountain tool.

• Custom plating cups specific to wafer diameter results in optimized plating performance.

• Rotating sparger provides an ideal solution flow across a stabilized wafer.

• Self-contained with all components required for an electroplating system.

• Centralized controls and a touch screen PLC to store plating recipes.

Benefits

• Superior WID and WIW improves development and processing cost by reducing the amount of metal required per wafer. This is extremely beneficial when plating gold or other precious metals.

• Reduced cost of R&D by providing a versatile tool that can be used to develop and test process parameters that can be transferred to mass production tool.

• A self-contained, modular tool allowing for low-cost incremental expansion of plating capabilities from a single metal application to multiple metal stacks.

• Technic supplies a wide range of electroplating chemistries for the quick development of optimum process parameters.

Technic’s Semcon 2000 expands on the success of the Semcon 1000, a single process manual electroplating tool, by providing customers with a multiprocess version offering more options for system layout and configura tions. Because of its modular construction, the customer can customize the tool to incorporate all required components needed for specific ap plications. The system can incorporate multiple cleaning, electroplating, rinsing, and other chemical processing all within an easy-to-manage tool that can accommodate any size and shape wafer to 200mm. The Sem con 2000 is extremely versatile with an easy to operate HMI interface for process monitoring of all key functions.

Constructed and designed with enhanced operator safety features, easy-access controls, and quick access to maintenance areas, the Semcon 2000 is fully compatible with any commercially available electroplating and ancillary chemistries. Construction options include FM-4910 specifications and SEMI S2-0200 Certification. 

Features

• Available single and double wafer plating cells with pretreatment, QDR and dragout rinsing, and reciprocating drying station.

• Closed loop flow control with reciprocating sparger, in-line filter with replacement alarm, and solution sample ports.

• Easy, touch screen HMI control panel for monitoring of all key opera tions and functions. Dual controls available for service chase installa tions.

• Programmable recipe controls for DC, pulse, and PPR rectifiers.

• Datalogging with wafer based report generation at the tool or via OPC interface.

• Open and dry backside plating fixtures are available.

• Automatic hands free filling and dosing systems available. Including software interface with automatic solution analysis equipment.

Benefits

• Multiple process configurations in a single tool: cleaning, electroplating, stripping, and etching.

• Capable of processing a variety of substrates including Si, GaAs, InP, and others.

• Customizable configuration to meet the customer’s requirements.

• Ongoing technical support with industry-leading chemistry – Technic supplies a wide range of advanced electroplat ing chemistries – providing for quick development of optimum process parameters.

Titanium and titanium alloys are widely used in advanced packaging as adhesion and barrier seed layers. With FOWLP, Flip Chip, 2.5/3D and other technologies continuing to require increased functionality with smaller feature sizes, traditional metal etchants are reaching their limitations.

DHF, SC1, and pure H2 O2 have been used for many years to etch titanium and titanium alloys. These traditional chemistries suffer from inconsistent etch rates, excessive undercuts, and low compatibility with metal stacks, and they are difficult to control. Because of these weaknesses, legacy chemistries cannot meet the current requirements of advanced packaging companies.

Working closely with our industry leading customers, Technic has successfully formulated a high-level metal etchant chemistry that eliminates many of the weaknesses of traditional titanium and titanium alloy etchants. TechniEtch TBR19 is a stabilized hydrogen peroxide based metal etchant that is extremely selective with a very low undercut value of < 0.2 microns.

Features

• Excellent selectivity

• Low undercut

• Improved etch uniformity

• Stable and consistent etch rate over the life of the bath

• Fluoride-free aqueous solution

• Compatible with most UBM and copper pillar integration materials

• Fully compatible with aluminum

• Tunable etch rate

Benefits

• High selectivity and low undercut provides high yields with fine pitch patterns

• Reduced cost of operation through extended bath life

• High process efficiency through stable chemistry and consistent etch rate

• Wide process operating window – 50% process overetch still results in minimal undercut