Tungsten Film Analysis

2830 ZT

Introduction

Production control of integrated circuits (ICs) frequently involves the analysis of tungsten layers on a Si substrate. Tungsten is used as conductor or metal film in the production of ICs, its role is to form the vertical interconnection wires between the transistors. The thickness of the W film is an important parameter. Due to its excellent selectivity and precision, wavelength dispersive X-ray fluorescence spectrometry is the ideal technique for monitoring the W film thickness in IC manufacturing.

Instrumentation

A Malvern Panalytical 2830 ZT XRF Wafer Analyzer equipped with a fixed channel for W is used for this report. Details of the measurement conditions are presented in Table 1.

Procedure

The W-Lα signal can be used to quantify the layer thickness of the film. A calibration line for W was set up. Fundamental parameter correction was implemented in the calibration to ensure validity over the whole calibration range in terms of layer thickness.

To demonstrate the analytical precision, a 15-cycle repeated measurement was carried out. The wafer was loaded and unloaded between each cycle.

Results

A calibration line for the W layer thickness is presented in Figure1. The calibration unit for the layer thickness is Å.

Results for the repeated measurement of layer thickness are shown in Table 2. The low relative RMS values indicate excellent measurement repeability.

Figure 1. Calibration for W layer thickness 

Conclusion

The Malvern Panalytical 2830 ZT XRF Wafer Analyzer can accurately analyze the W layer thickness. The range can be adapted to customer requirements: extending up to 40 µm.