ATE Vendors Seek Piece of 3D Chip Testing Pie
By Mark LaPedus, SemiMD senior editor
The conventional test flow for today’s 2D chips includes wafer probe and final test. Final test gets the vast majority of the “test seconds,” while wafer probe takes a back seat in the process.
“The more stringent test is done at final test (for today’s 2D designs). Wafer sort was viewed as an initial screening process. That breaks down in 3D. There is a need to migrate high quality test from final test to wafer sort,” said Steve Pateras, product marketing director for Silicon Test Systems at Mentor Graphics Corp.
Today’s 2D chips are processed in the fab and then moved to the wafer prober. Then, they are packaged and sent to final test. Because 2.D/3D chips use bare die, most of the testing is done on the prober.
In fact, the lion’s share of “test seconds” will migrate to wafer probe and sort for 2.5D/3D chips, leaving the traditional final test vendors — Advantest/Verigy, LTX-Credence and Teradyne — on the outside looking in.
Final test and systems-level test are still important in 3D chip testing, but now, the bulk of the work — and dollars — will migrate towards the wafer probe vendors, such as Tokyo Electron Ltd. (TEL) and Tokyo Seimitsu Kogu Co. Ltd. Much to the chagrin of the ATE crowd, wafer probe vendors are already grabbing the majority of the test time in wafer-level chip-scale packaging (CSP). Probe card vendors will continue to benefit in both 2D and 3D.
The ATE vendors have been fighting back, however. In 2009, ATE supplier Verigy Inc. entered the probe card business by buying Touchdown Technologies Inc. Touchdown manufactures probe cards, a key part of the wafer probe process.
Probe cards serve as the interface between a wafer prober and a semiconductor wafer. Equipped with tiny probes, probe cards are relatively the most expensive part of testing, because they are custom and consumable items. Cascade, FormFactor, MicroProbe and others sell probe cards.
Then, last year, Japanese ATE giant Advantest Corp. completed its acquisition of Verigy in an all-cash transaction, estimated to be approximately $1.1 billion. Advantest itself has been selling probe cards for some time.
In contrast, Teradyne Inc. has a different strategy. It does not sell probe cards, but rather it “partners with multiple probe card companies,” said Greg Smith, manager of the Computing and Communications Business Unit at Teradyne. It is unlikely Teradyne will buy a wafer probe vendor or develop its own system. “The existing vendors have a mature position in the market,” Smith said.
Teradyne, the world’s largest ATE vendor, is not throwing the towel in the arena. In fact, the company recently rolled out latest addition to Teradyne’s probe interface family, dubbed the UltraProbe.
Conventional wafer probers consist of a probe interface board (PIB), a probe tower and a probe card with wafer contactors. Teradyne’s UltraProbe solution eliminates the probe tower. It also combines the functionality of the PIB and probe card into a single PCB. By reducing the number of components and interconnects, UltraProbe will boost the signal integrity for wafer-level-packaging, known good die (KGD) and other products, Smith said.
It also enables planarity for various probe cards, such as standard cantilever, vertical and membrane solutions, he added. The UltraProbe is an option for its UltraFlex line of logic testers. The solution will provide a shorter signal path to the device under test (DUT). UltraProbe is ideal for higher-speed digital and RF devices, he said.
Meanwhile, the probe card business reflects the cyclical nature of ATE, which saw a slowdown in the fourth quarter. Some probe card vendors, namely loss-ridden FormFactor Inc., have struggled for some time, partly due to its reliance on the memory market.
Demand for DRAM-based probe cards were weak in the fourth quarter, said Tom St. Dennis, CEO of FormFactor, in a conference call. The DRAM business has been hit hard by a slowdown in the PC market. The PC business has also been impacted by the floods in Thailand. Suppliers of disk drives with factories in Thailand were unable to ship product.
The company is making a push into the systems-on-a-chip (SOC) market with a vertical probe card solution. FormFactor, the world’s largest probe card maker, this week announced its financial results for the fourth quarter of fiscal 2011 that ended on Dec. 31, 2011. Quarterly revenues were $30.2 million, down 42 percent from $52.1 million in the third quarter of fiscal 2011, and down 31 percent from $43.9 million in the fourth quarter of fiscal 2010.
On a GAAP basis, net loss for the fourth quarter of fiscal 2011 was $27.0 million or minus $0.54 per fully-diluted share, compared to a net loss for the third quarter of fiscal 2011 of $9.9 million or minus $0.20 per fully-diluted share, and a net loss for the fourth quarter of fiscal 2010 of $20.4 million or minus $0.40 per fully-diluted share.
For fiscal 2011, FormFactor posted revenue of $169.3 million, down 10 percent from $188.6 million in fiscal 2010. Net loss for fiscal 2011 was $66.0 million or minus $1.31 per fully diluted share, compared to a net loss of $188.3 million or minus $3.75 per fully-diluted share for fiscal 2010.
