New High Voltage Devices Will Change Parametric Test

Many parametric test engineers are learning to cope with high voltage process requirements for new applications such as high brightness LEDs. Not surprisingly, high voltage processes require high voltage parametric testing for process control and reliability monitoring.

Most of yesterday’s device technologies were limited to under 100V. Such devices were easily characterized with existing parametric test systems.

Consider, for example, Bipolar-CMOS-DMOS (BCD) technology. The term BCD is often used to describe a number of variants, including combinations such as CMOS-LDMOS, NMOS-LDMOS, etc. Today, BCD devices have emerged that use LDMOS to support voltages as high as 700V or 800V, demonstrating the upward trend. It’s expected that BCD technologies will exceed 1000V by about 2012.

Such high voltage devices are currently used for applications such has High Intensity Discharge (HID) illumination, where a combination of high voltage and high power is needed. There are a variety of applications for high voltage BCDs, including:

• Industrial controls (motor and actuator control)

• Automotive controls (lighting, engine control, drive train control, etc.)

• Advanced lighting (LED, HID, etc.)

• Power conversion and storage

• Display (backlight)

These devices require special consideration when developing a parametric test strategy. Part of the challenge lies in the fact that the new high voltage requirements add to rather than subtract from the roster of parametric tests. In many if not most cases, the high voltage transistors are controlled by complex logic that requires low voltage/low current parametric test. Consequently, both high voltage and logic tests have to be addressed within the same test plan while minimizing impact on throughput.

The roadmap for BCD technologies and related processes over the next two to five years clearly indicates the need to move beyond 1000V in parametric test. This will pose a number of challenges for high voltage parametric test systems. Instrumentation is likely the least significant of the challenges; however, probing at more than 1500V will almost certainly be much more challenging.