BIST is a technology used to provide self-test functions by implanting relevant functional circuits into the circuit during design, thereby reducing the dependence of device testing on automatic test equipment (ATE).
What is BIST testing technology?
The Chinese name of BIST technology is built-in self-test technology, which can be applied to almost all circuits, so it is widely used in the semiconductor industry. For example, the BIST technology commonly used in DRAM includes implanting a test pattern generation circuit, a sequential circuit, a mode selection circuit, and a debug test circuit in the circuit.
The big reason for the rapid development of BIST technology is due to the high ATE cost and the high complexity of the circuit. Nowadays, highly integrated circuits are widely used, and testing these circuits requires high-speed mixed-signal test equipment. BIST technology can reduce the need for ATE by implementing self-testing.
BIST technology can also solve the problem that many circuits cannot be directly tested because they do not have direct external pins, such as embedded flash. It is foreseeable that even the most advanced ATE cannot fully test the fastest circuit in the near future, which is one of the reasons for using BIST.
The advantages of using BIST technology are:
1. Reduce test cost
2. Improve error coverage
3. Shorten the time required for testing
4. Convenient customer service
5. Ability to independently test
Problems with BIST:
1. Which tests need to be completed by BIST?
2. How much extra area is allowed?
3. What kind of external incentives are needed?
4. Time and efficiency required for testing?
5. Is BIST fixed or programmable?
6. What impact will the adoption of BIST have on existing processes?
BIST technology can be roughly divided into two categories: Logic BIST (LBIST) and Memory BIST (MBIST)
LBIST is usually used to test random logic circuits. Generally, a pseudo-random test pattern generator is used to generate input test patterns, which are applied to the internal mechanism of the device; and multi-input register (MISR) is used as the output signal generator.
MBIST is only used for memory testing. A typical MBIST contains test circuits for loading, reading, and comparing test patterns. There are several MBIST algorithms commonly used in the industry, such as the "March" algorithm, Checkerboard algorithm, and so on.
Another relatively rare BIST is called Array BIST, which is a type of MBIST that is specifically used for self-testing embedded memories. Analog BIST is used for self-testing of analog circuits.
BIST technology is becoming an alternative to high-priced ATE, but BIST technology cannot yet completely replace ATE, and they will coexist for a long time to come.
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