Trimming is almost a dirty world in some parts of the semiconductor industry. It is however a hugely powerful method to manufacture devices that have a capability beyond that of the silicon fabrication process being used. But trimming is notoriously difficult to control with regards to yield and sometimes quality. It is for this reason that MFG Vision have been helping our customers understand the best methods for analysing the data from trimming and how the analysis of that data can help ramp yields faster.
Trimming is achieved in 3 main ways in the industry:
1. Fuse trimming, by blowing either metal, poly or zener fuses.
2. Laser trimming, by cutting away part of the film in thin-film or thick-film resistors.
3. E-trim or floating gate trimming.
The most difficult of these to manage in production, although the cheapest to implement, is fuse trimming. The fact that it is so cheap to implement is why even in 2015 fuse trimming, although it is the oldest technology, is still widely used in power analog devices.
The interesting and sometimes worrying aspect of analysing trim data is that you move away from standard statistical analysis. While pre-trim data with enough data points will generalise towards a normal distribution, post trim data in an ideal situation will be a rectangular shape when plotted as a histogram. So other statistical methods are very helpful. One of the best is an XY scatter plot of pre-trim vs post trim. This can show many characteristics about the trimming, including many characteristics of issues with the trimming.
By understanding how to analyse the test data recorded before and after trimming our customers have benefited from significant success in ramping their new product yields faster than ever before. If you would like to know some of how this is achieved please download our application note. By clicking the link below and entering your details the application note will be emailed to you immediately.