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May 17, 2022

Inventive Wands Key to Safe Manual Handling of Fragile Substrates

By Karl Gartland I May 17, 2022 I

Moving devices securely through fabrication without incurring loss or damage is essential for all successful IC production. It takes an intimate knowledge of materials science, chemistry, and electrical principles to produce efficient and successful edge ICs. But no matter how many improvements are made in controlling the process, yield is primarily degraded by inappropriate handling of the substrates. Vital to enabling high-yielding and reliable products, successful wafer handling is essentially the price of admission for any IC manufacturer.  

Wafer handling is like the function of a referee in sports. When it is done correctly, it is taken for granted. When it is done incorrectly, the issues become very visible. Wafer handling of any type, manual, semiautomated, or fully automated, needs to be as close to flawless as possible. Risks from wafer handling include particle and chemical contamination, scratching, edge chipping, and ESD. These risks are not just for the wafers being handled by the human or tooling but also for the wafer near the wafer being handled. For example, particles can drop from a wafer being handled to the wafer below or sprayed onto the wafer above. Those particles may be problematic in the current or succeeding operations. Every person in lithography has an example of an area on the wafer misprinted because a particle on the backside created a nonplanar surface during exposure. Scratches to the wafer surface below the wafer being handled can quickly occur. Properly designed wands can reduce that risk. ESD safe material is essential for wands and wand tips; this will reduce the risk of ESD for the wafer being handled. Other risks can be reduced by placing a bump stop on the back of the wand, preventing an operator from inserting a wand between wafers closely spaced in a cassette. Wafer-handling challenges are magnified for compound semiconductor (CS) makers. Many of these firms have limited budgets. CS companies are processing wafers smaller than 300mm, and most are processing wafers less than 200mm in diameter. This means that there are significantly fewer automation choices available.

200mm fab capacity is currently on track to reach a record high by 2024 (according to the most recent SEMI 200mm Fab Outlook Report). The industry looks to smaller wafers to meet rising chip demand and alleviate shortages. CS devices are a leading driver of this burgeoning demand, creating a significant opportunity for automation technologies like those developed by H-Square.

Over the past four decades, H-Square has researched and developed innovative methods for improving, reducing, and even eliminating the need for substrate handling. As a result, we’ve produced and delivered many industry-leading tools, techniques, and processes to enable high-yielding devices.

In 1992-93, H-Square designed the c vacuum tip, quickly becoming the de facto standard for 200mm and 150mm wafer handling worldwide. When 150mm gallium arsenide (GaAs) wafers were first introduced to the market in the mid-1980s, we quickly learned that the vacuum pocket (inlet) on the vacuum tip surface was an inappropriate design for that material, as it caused immediate stress to the crystalline structure of the GaAs wafer. To address this issue, H-Square swiftly designed, manufactured, and tested its first GaAs handling tip, the T693PKAS3-001, and shipped it to the customer within one week. Rerunning these same tests using the new custom GaAs vacuum pocket yielded zero breakage. Today, 100 percent of 150mm GaAs customer sites worldwide employ this tip.

H-Square has continued to innovate, addressing the needs of the growing CS market. Our latest product, the T793PKAS3 PEEK vacuum tip for 200mm wafers, is specifically designed for thin or fragile substrates such as GaAs, germanium (Ge), silicon-germanium (SiGe), indium phosphide (InP), and other compounds that require special care to prevent breakage.   

In summary, when manual wafer handling is required, using the proper tools is a must. H-Square designs and produces wands for every wafer size and chips and very small substrates. For every type of substrate—from thin wafers, including taiko wafers, to thick wafers, including glass and substrates for hard disk drive heads—there’s an H-Square wand that will ensure its safe transport through the fab. 

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