### 7.2.4 Summary to: 7.2 Processes and Specialities

| MEMS uses all of "known" Si technology and has some specifics of its own. |  |
Works | Sticks
--- | ---
|  | Making cantilevers and membranes necessitates making "large" cavities. |
|  | Staying absolutely planar and stress-free is essential |
|  | Packaging can be far more demanding than for chips (e.g. transparent tops for OMEMS, keeping defined pressures for > 10 a in gyros). |
| The bane of MEMS is stiction. |
|  | If you can't lubricate, it will stick sooner or later. Never bring moving parts in contact! |
|  | MEMS design therefore cannot just miniaturize exiting mechanical designs; it must look for new approaches. |
| MEMS employs some special processes and materials; they are the drivers of progress |  |
|  | Anisotropic chemical etching |  |
Making "large" cavities and extremely deep "holes" Planarization Free-standing structures
|  | High-rate plasma etching ("Bosch process") |
|  | Chemical-mechanical polishing |
|  | Sacrificial layers and removal (including chemical etching with "vapors") |
|  | Wafer bonding; in particular for packaging. |
| Process integration looks simple if compared to an advanced CMOS process, but is actually rather involved due to the special processes needed and quality requirements |  |
Exercise 7.2-1
All Questiosn to 7.2

© H. Föll (Semiconductor Technology - Script)