Measuring Die Tilt Using Shadow Moiré Optical Measurements; New Techniques for Discontinuous and Semi-Reflective Surfaces

Abstract

When dealing with production of Flip Chip Packages in semiconductor packaging, the angle between the die and package substrate is critical for maintaining product yield and reliability. Current outgoing quality checks for die tilt can be time consuming to measure heights via point to point measurement techniques. Existing die tilt measurement approaches can also have reproducibility issues from user to user. Shadow moiré technology is a full field optical inspection technique commonly used for flatness characterization in the semiconductor industry, particularly at elevated temperatures. Two limitations to shadow moiré apply when discussing outgoing QC of die tilt: 1) shadow moiré requires a diffuse reflective surface for measurement; 2) shadow moiré is unable to measure sudden step heights. This paper discusses applications techniques and real world examples to overcome or mitigate the limitations of shadow moiré technology and use this full field and high speed measurement technology to measure die tilt. Using shadow moiré for this measurement technology can reduce measurement and user time as well as improve consistency of measurements from user to user. As shadow moiré tools are often used for at temperature flatness measurements, this added application can reduce the number of different measurement tools needed in QA labs.