X-FAB upgrades substrate coupling analysis tool

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X-FAB Silicon Foundries, an analogue/mixed-signal and specialty foundry, has expanded the scope of its SubstrateXtractor tool, via which unwanted substrate coupling effects can be examined.

According to X-FAB it is the first foundry worldwide to offer this analysis function for a BCD-on-SOI process. With the company’s XT018 180 nm BCD-on-SOI technology now being supported, X-FAB complements the XH018 and XP018 180 nm bulk CMOS processes that the tool was originally designed for. Through use of the new SubstrateXtractor version, accelerated SOI-related product development can be achieved, avoiding the need for multiple iterations.

The initial SubstrateXtractor, which X-FAB developed in collaboration with EDA partner PN Solutions (and is based on its widely used PNAware product), was released in 2019. Using it, customers have been able to address the coupling issues caused by interactions between active and passive elements within semiconductor substrates (whether these elements are part of the circuit itself or present parasitically). This has resulted in quicker time to market for customer projects. Support for SOI processes is built on the PNAwareRC tool by PN Solutions and further increases the capabilities of the platform and broadens its appeal.

The BOX/DTI features of X-FAB’s XT018 process enable isolation of constituent functional blocks on the chip from each other. This can apply to sensitive analogue blocks needing to be decoupled from digital blocks, or low noise amplifiers that must be isolated from high-voltage driver circuits. It also makes multi-channel implementations much easier, as circuits in XT018 are effectively placed in their own separate substrate, thereby reducing crosstalk.

The ability of SubstrateXtractor to analyse substrate couplings in SOI-based integrated circuits is being described as a major advance. Though active silicon islands in SOI processes can be completely dielectrically isolated by BOX and DTI, passive R and C couplings may still be present. Using this updated tool, a passive RC network can be extracted for lateral and vertical coupling paths resulting from DTI and BOX. These passive coupling networks can be simulated to assess what impact they will have on the integrated circuit.

Key applications for this additional post-layout extraction will be the high-current and high-voltage devices used in industrial and automotive systems.

“Mitigation of substrate coupling is a challenging task, and through support for the extraction of parasitic elements relating to our XT018 BCD-on-SOI process, customers will be able to simulate the coupling of circuit blocks and identify interferences that will be detrimental to performance,” said Lars Bergmann, Director of Design Support at X-FAB. “This will be of particular interest in situations where there are very large interference voltages involved or for high frequencies in the single-digit GHz range.”