Process control monitors for interferometric modulators
View Patent ↗Process control monitors are disclosed that are produced using at least some of the same process steps used to manufacture a MEMS device. Analysis of the process control monitors can provide information regarding properties of the MEMS device and components or sub-components in the device. This information can be used to identify errors in processing or to optimize the MEMS device. In some embodiments, analysis of the process control monitors may utilize optical measurements.
1. A process control monitor for monitoring the effect of a process for manufacturing interferometric modulators on the color of light reflected by those interferometric modulators, comprising a test etalon that comprises a higher density of posts supporting a mechanical membrane in the test etalon than in interferometric modulators produced by the process.
2. The process control monitor of claim 1 , wherein the mechanical membrane in the test etalon has substantially the same structure as a mechanical membrane in the interferometric modulators produced by the process.
3. The process control monitor of claim 1 , wherein, except for the higher density of posts, the process control monitor has substantially the same structure as the interferometric modulators produced by the process.
4. A method of monitoring the effect of a process for manufacturing interferometric modulators on the color of light reflected by those interferometric modulators, the method comprising:
forming a test etalon that comprises a higher density of posts supporting a mechanical membrane in the test etalon than in interferometric modulators produced by the process; and
detecting light reflected from the test etalon.
5. The method of claim 4 , wherein the test etalon comprises at least two regions, wherein the posts in one region have a different height than posts in the other region such that light reflected from the two regions are of different color.
6. The method of claim 4 , wherein at least two test etalons are formed where the posts in one test etalon have a different height than posts in the other test etalon such that light reflected from the two test etalons are of different color.
7. The method of claim 4 , wherein the reflected light is detected during forming of the test etalon.
8. The method of claim 4 , wherein the reflected light is detected after forming of the test etalon.
9. The method of claim 4 , wherein detecting the reflected light comprises measuring a color of the reflected light with a colorimeter.
10. The method of claim 4 , wherein detecting the reflected light comprises measuring a spectrum of the reflected light with a spectrometer.
11. The method of claim 10 , further comprising determining the depth of the test etalon from the detected light.
12. The method of claim 11 , wherein the determining comprises fitting the measured spectrum to a model of etalon interference.