Overview

CS‑600A Series Overview

IWATSU Electric Co., Ltd. developed the CS‑600A series to provide a high‑voltage capacitance‑vs‑bias (C‑V) measurement platform for power semiconductor devices.

• The system includes a CV bias unit (model CS‑603A or CS‑605A), an external LCR meter, and PC‑based control software (CV measurement tool).
• It automates the application of DC bias while using a small AC test signal from the LCR meter to measure device capacitance.
• The CS‑605A provides bias up to 5 kV, while the CS‑603A supports up to 3 kV.
• Particularly suited for emerging SiC and GaN power MOSFETs/IGBTs and can also measure high‑voltage capacitors and diodes.
• Adapters used with IWATSU curve‑tracer systems can be reused, and the bias unit integrates with wafer probe stations for on‑wafer testing.

Features and Measurement Modes

High‑Voltage Bias Capability

The CS‑605A can sweep DC bias from 0 V to 5 kV (with a low‑voltage range of 0–50 V), while the CS‑603A offers 0 V to 3 kV (0–50 V low‑range). The bias resolution is 100 mV in the high‑voltage range and 1 mV in the 0–50 V range.

Bias is applied via a controlled DC source inside the bias unit. Safety interlocks ensure the bias is disabled if the cover is open or cables are incorrectly connected.

C‑V Measurement (Capacitance vs. DC Bias)

• C‑V (capacitance vs. bias voltage): The system sweeps a DC voltage across the drain–source terminals while superimposing a small AC measurement signal from the LCR meter. This mode characterises device capacitance as a function of bias and is used to extract parameters such as Ciss, Coss and Crss. The bias sweep can be linear, logarithmic or user‑defined (list). The software supports up to 5 000 measurement points and an UP sweep direction.
• C‑G (capacitance vs. gate voltage): Similar to C‑V but sweeps gate‑source voltage while measuring capacitances. Useful for capturing the gate‑drain capacitance (Cgd) and investigating gate‑oxide characteristics.
• C‑Time: Applies a constant DC bias for a specified period and monitors capacitance variation over time. This mode is used for evaluating time‑dependent dielectric degradation.
• Frequency sweep: The measurement frequency (10 kHz–100 kHz) can be swept to study frequency‑dependent impedance.

Measurement Parameters

The system calculates various device capacitances from the measured impedance:

• Input capacitance (Ciss or Cies): defined as Cgs + Cgd for MOSFETs or Cge + Cgc for IGBTs.
• Output capacitance (Coss or Coes): defined as Cds + Cgd (MOSFET) or Cce + Cgc (IGBT).
• Reverse transfer capacitance (Crss or Cres): Cgd for MOSFETs; Cgc for IGBTs.
• Additional parameters include CT (capacitance between all terminals), Cgs, Cge/Cgd, Ccg/Cds, Cce (calculated value), and Rg (gate resistance).

Measurement Range and Accuracy

• Measurement range: at 10 kHz, the system measures 100 pF–10 nF with ±5 % accuracy (±50 pF); at 100 kHz, the range is 10 pF–1 nF with ±5 % accuracy (±2 pF).
• The specification includes conditions for unequal capacitance ratios (Cgd : Cds : Cgs = 1 : 1 : 1 or 1 : 10 : 100), ensuring accurate measurement even when capacitances differ widely.
• Frequency range: 10 kHz–100 kHz.
• AC signal level: 100 mV–1 V from the LCR meter. Users can choose lower levels for sensitive devices or higher levels for improved signal‑to‑noise ratio.
• Gate bias: ±25 V with 1 mV resolution allows separate gate bias during measurement.

Sweep Types and Data Handling

• The software supports linear, logarithmic, list and single‑point sweeps.
• Up to 5 000 data points can be collected in one sweep, enabling high‑resolution C‑V curves.
• The tool includes waveform comparison and reference display functions to overlay multiple measurements.

Safety Features

• The CV bias unit includes an interlock that disables high‑voltage output when the cover is open or when the CV cable is not correctly connected.
• External interlock connections are available for integrating with probe stations; an optional external interlock kit is offered.
• The manual warns users to discharge the device under test after measurement to avoid electric shock and to use only specified test leads.