Differences between VOx and a-Si technology

Infrared focal plane array is the core of infrared thermal image system. It can be widely used in security monitoring, industry, transportation, medical and other fields. Currently, VOx and a-Si are the main sensitive materials of uncooled infrared focal plane array. This article will compared their similarities and differences in terms of manufacturing process, film type, technical accumulation time, film performance indicators and device technology.

1. Similarities

a. Manufacturing process

Microbolometer technology is compatible with CMOS technology and can be integrated with CMOS readout circuits on a single chip, allowing mass production based on semiconductor manufacturing processes.

b. Film type

Both films are semiconductor thermosensitive films (infrared thermosensitive films), and the TCR film (temperature coefficient of resistance) is proportional to its resistivity.

2. Difference

a. Technical accumulation time

In 1978, researchers made a breakthrough in using VOx materials to make detectors, but a-Si technology was delayed by 10 years. The performance and technology of chips made of VOx are more mature than a-Si.

b. Film performance indicators

At the same resistivity, VOx film is better than a-Si film. Under the same TCR (temperature coefficient of resistance), 1/f noise coefficient of a-Si film is higher than VOx film. In short, the VOx infrared detector has better imaging effect.

c. Device technical indicators

VOx infrared detector has high photoelectric conversion efficiency and good temperature measurement stability. The NETD (thermal sensitivity) of VOx infrared detector can reach 30mk, while the NETD of a-Si infrared detector is usually around 50mk.

The image non-uniformity of VOx infrared detectors is better than that of a-Si thermal detectors. The residual fixed image noise of a-Si is more than an order of magnitude larger than that of VOx, resulting in blurred image texture and slightly lower clarity than VOx.

Looking at the global infrared market, both VOx and a-Si have been widely used. GSTiR adopts VOx technology, has a complete independent and controllable product line, and is supported by the earliest domestic technology to achieve mass production of wafer-level packaging (WLP), which greatly reduces the cost of VOx detectors.

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