TSMC OIP: Soft Error Rate Analysis

Increasingly, end users in some markets are requiring soft error rate (SER) data. This is a measure of how resistant the design (library, chip, system) is to single event effects (SEE). These manifest themselves as SEU (upset), SET (transient), SEL (latch-up), SEFI (functional interrupt).

There are two main sources that cause these SEE:

• natural atmospheric neutrons
• alpha particles

Natural neutrons (cosmic rays) have a spectrum of energies which also affects how easily they can upset an integrated circuit. Alpha particles basically are stopped by almost anything and as a result these can only affect a chip if they contaminate the packaging materials, solder bumps etc.

Increasingly, more and more partners need to get involved in this reliability assessment process. Historically it has started when end-users (e.g. telecom companies) are unhappy. This means that equipment vendors (routers, base-stations) need to do testing and qualification and end up with requirements for process, cell design (especially flops and memories), and at the ASIC/SoC level.

Large IDMs such as Intel and IBM have traditionally done a lot of the work in this area internally, but the fabless ecosystem relies on specialist companies such as iROCtech. They increasingly work with all the partners in the design chain since it is a bit like a real chain. You can’t measure the strength of a real chain without measuring the strength of all the links.

So currently there are multi-partner SER efforts:

• foundries: support SER analysis through technology specific SER data such as TFIT databases
• IP and IC suppliers: provide SER data and recommendations
• SER solution providers: SEE tools and services for improving design reliability, accelerated testing

Reliability has gone through several eras:

• “reactive” end users encounter issues and have to deal with them. product recalls, software hot-fixes etc
• “awareness” system integrators pre-emptively acknowledge the issue. system and component testing, reliability specifications
• “exchanges” requirements and targets are propagated up and down the supply chain with SER targets for components, IP etc
• “proactive” objective requirements will drive the design and manufacturing flow towards SER management and optimization

One reason that many design groups have been able to ignore these reliability issues is that they depend critically on the end market. The big sexy application processors for smartphones in the latest process do not have major reliability issues: they will crash from time to time due to software bugs and you just reboot, your life is not threatened. And your phone only needs to last a couple of years before you will throw it out and upgrade.

At the other end of the scale are automotive and implantable medical devices (such as pacemakers). They are safety critical and they are expected to last for 20 years without degrading.

iRocTech have been working with TSMC for many years and have even presented several joint papers on various aspects of SER analysis and reliability assessment.

iRocTech will be presenting at the upcoming TSMC OIP Symposium on October 1st. To register go here. To learn more about TFIT and SOCFIT, iRocTech’s tools for analyzing reliability of cells and blocks/chips respectively, go here.