Abstract
The present work reports on studies and process
developments to utilize the chemical mechanical
planarization (CMP) technology in the field of micro
electrical mechanical systems (MEMS). Approaches have
been undertaken to enable the manufacturing of thick film
SOI (silicon-on-insulator) substrates with a high degree
of flatness as well as utilizing CMP for the formation of
several novel MEMS devices.
Thick film SOI wafers are of high interest in MEMS
manufacturing as they offer obvious benefits as a
starting material or foundation for more complex
structures. Precise control of the SOI layer thickness as
well as the removal uniformity is of critical importance
to fully utilize the benefits of this technology. By
combining fixed abrasive (FA) pads for polishing and
novel grinding techniques it is shown that major
improvements can be achieved over the standard
manufacturing sequence. Analysis of the material removal
rate (MRR) dependency on several process parameters is
made. Together with the FA pad vendor a suitable
consumable set for SOI is generated, which shows long
term stability in the generated process. A comparison
with standard methods is undertaken to prove the surface
and crystalline quality of the resulting substrate
material is equivalent. Analysis is done to understand
the microscopic mechanism of removal.
The CMP process is applied to several MEMS structures to
smooth deposited oxide films and to enable direct wafer
bonding (DWB) at low temperatures. This allows the design
of bonded multiple stack layers including heat sensitive
materials such as metals.
FA CMP is applied to large pattern MEMS for total
planarization but also for smoothing of the surface of
single protruding structures while minimizing edge
rounding and preserving the original intended pattern
shape. With dedicated CMP steps thick film polysilicon
smoothing is demonstrated enabling DWB. The
chemo-mechanical particularities of the FA pad are
investigated in detail.
Original language | English |
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Qualification | Doctor Degree |
Awarding Institution |
|
Award date | 20 Oct 2006 |
Place of Publication | Espoo |
Publisher | |
Print ISBNs | 951-38-6855-9 |
Electronic ISBNs | 951-38-6856-7 |
Publication status | Published - 2006 |
MoE publication type | G5 Doctoral dissertation (article) |
Keywords
- CMP
- micro electro mechanical devices
- polishing
- fixed abrasives
- MEMS
- SOI
- silicon-on-insulator
- direct wafer bonding
- DWB
- low temperature bonding