Cerebras bear case: its wafer products have a lifespan of only two years.

October 29 - Semiconductor research firm Culper today expressed the view that Cerebras's wafer-scale engine (WSE) and routing architecture are indeed fully capable of solving yield issues, as the company claims. The uncertainty lies in how long the wafer can last in actual operation.

The research report points out that Cerebras's design requires a large number of redundant interconnects to accommodate manufacturing defects. However, all these BEOL wirings significantly increase the effective area susceptible to TDDB (time-dependent dielectric breakdown), potentially creating greater long-term reliability risks. TDDB can cause short circuits, and in this design, short circuits are more dangerous than open circuits. The dielectric layer thickness determines the probability of TDDB occurrence, and variations in this thickness may be spatially correlated across the wafer. This makes it likely that many interconnect failures will concentrate in specific regions. How Cerebras detects these short circuits and avoids using faulty interconnects is currently unclear.

In summary, the firm believes that the CBRS wafer will fail after approximately 2 years of use, and this product lifespan is disruptive to the company's entire business.