Die Separation Technology Improves Throughput, Reliability

Today's scribe machines are not the messy wafer saws of yesteryear — they are cleanroom-compatible systems that must meet specifications of submicron positional accuracy, narrow, shallow scribes in wafers and MTBFs over 1000 hours. Such were some of the specifications placed on development of a new die separation technology from Diamond Touch Technology Inc. (Prescott Valley, Ariz.), a company that got its start re-engineering dicing machines and currently provides complete scribe and fracture tools. The company's technology can meet exacting requirements for ultrathin scribing and low-impact fracture due to a novel chuck and frame design as well as control software with extensive diagnostic capability. Interestingly, the systems do not use deionized water.

'We surveyed engineers working on production lines, and they told us their biggest problem was tool uptime, which could be as low as 50%,' explained Michelle Broyles, president of Diamond Touch Technology. Most of the time was consumed with trouble-shooting software problems, software interface issues or mechanical problems due to the complexity of the tool, she said. The company responded by developing reliable dicing hardware and software with a limited number of commands and good diagnostic routines. 'We have over 100 installations of this software. We designed it for ease of operation and rapid resolutions of problems caused by anything from a broken wire to inaccurate positioning of the scribe tool.'

The process uses a diamond scribing tool to impart a 1 µm deep, 3 µm wide scribe line that moves at a rate of 3 in./sec across the wafer. Once scribed, a pulse of compressed air from under the chuck simultaneously separates all die in 50 msec. The shallow DiaFrame dome (500 µm at center) enables die separation and a repeatable return to its original shape. (Source: Diamond Touch Technology)

Once the wafer is scribed, the scribing stylus lifts and a small puff of clean dry air is forced through the chuck at very high speeds and returns the DiaFrame to its original shape. This burst simultaneously fractures all die on the wafer within microseconds, thereby increasing system throughput. At that point a pick-and-place tool can be used to remove the die or the wafer can be shipped to an assembly and packaging facility. The dome shape prevents the need for tape restretching to separate die, which is necessary with many tape-based frames. The scribe and fracture system is mounted on a patented composite carbon fiber antivibration platform that is hundreds of times more stable than granite and has no third-order harmonics. Other features of the hardware include plug-and-play operation and the use of standard components throughout — from the PC to stepper motors to power supplies. Diamond Touch claims its tools average a 2500 hr MTBF and 3 hr MTTR.

An important contributor to that high uptime is the control software, which can also be added to existing dicing tools. Using DOS-based software with hierarchical design and an FPD touch-screen, the programs and user interface allow rapid recovery from tool interrupts. The system can be calibrated in minutes and it takes two days to train an operator in its use.

'Approximately 10-15% of software development went into making the machine operate, 30% was devoted to ergonomics and the user interface, but the largest effort went into error handling,' explained company vice president Dave Barbour. He estimated that a single interrupt can come from any of 15 sources in the machine and, depending on the conditions that occurred directly before the operation was interrupted, the program can rapidly determine the safest thing to do next. Diagnostic programs allow testing of every machine component in the field. Given the set of conditions, a routine is recommended for returning the system to production operation. The software also allows networking capability and remote monitoring of the tools.

Diamond Touch's approach meets the needs of silicon suppliers looking to increase tool uptime and yield, but it is especially attractive to makers of micromachines, III-V and II-VI materials because the scribe and fracture is a completely dry process, eliminating hazardous waste. It allows near-zero contamination levels on the wafer following fracture. The elimination of DI water also saves the investment in cooling water, chillers and disposal.