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Displacement Modulated Four-Point Bend Adhesion Measurement Tool Disclosure Number: IPCOM000032204D
Publication Date: 2004-Oct-26
Document File: 3 page(s) / 17K

Publishing Venue

The Prior Art Database


Disclosed is a method that improves the current state of the art by adding a displacement modulation to aid in crack detection.

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Displacement Modulated Four-Point Bend Adhesion Measurement Tool

Disclosed is a method that improves the current state of the art by adding a displacement modulation to aid in crack detection.


The current four-point bend adhesion measurement technique relies on crack propagation. As the crack begins to travel from the engineered defect (i.e. pre-crack) the crack can stall, during which time elastic energy is increased due to the continued bending of the sample. This result often occurs on samples with a strong interface. Once arrested, the system begins to store elastic energy. This energy can be released incrementally by a crack propagating and stalling several times, or it is possible that enough energy is stored to allow the crack to propagate through the interfaces of interest. Also, the current load-displacement curve is difficult to analyze, and does not lend itself to transparent automation. Therefore, an engineer or technician must consider every curve to gain a valid interpretation of the result. Both of these issues lead to an increase in throughput time for the distribution of adhesion results that are important for integrated thin film development activities.

Currently, a displacement controlled four-point bending jig equipped with a load sensor is used to measure crack propagation. The load-displacement curve is graphed as a sample coupon is bent. The coupon consists of two cut pieces of silicon wafers, with one being a silicon dioxide- on-silicon substrate standard and another being the thin film stack of interest. These wafer pieces are glued together with epoxy resin, and the pre-crack is made on the side of the coupon with a diamond saw. Many (i.e. 10-12) sample coupons are created for a given sample. Once completed, the data is analyzed wherein the engineer or technician determines if a plateau region was observed in the load-displacement curve. If so, the load at which the plateau occurred is recorded. In most instances, 30% or less of the samples have such features. The yield can be next to zero on thin film stacks with a particularly strong interface. When the yield is small, the only solution is to make more samples and collect more data, which is time consuming and requires staffing.

General Description

The disclosed method’s four-point bend technique is useful for measuring the interfacial adhesion properties for a variety of materials; however, the current implementation of this technique suffers from automation, repeatability, and interpretation problems. A solution to any of these problems is...