To be read first:
- Processing is restricted only to 100mm wafer to wafer assembling.
- Wafer cleaning: The surface of wafers processed in the SB6 tool should be cleaned as best as possible. Having a smooth, particle-free, defect-free surface is extremely important to achieve reliable and good bonding results. The risk of breaking wafers is high if the wafers are not cleaned properly.
- Cross-Contamination: The SB6 pressure plates are consumables that are changed based on the type of bonding method to avoid cross-contamination. Make sure to correctly indicate your bonding type when booking the tool, and respect the configuration planning.
- Please immediately inform the CMi staff in case of problems with the equipment.
RESERVATION RULES AND BOOKING FEES POLICY:
- No booking restrictions.
- Reservation names must correspond to operators.
The substrate bonder SB6 from Süss Microtec is a dedicated tool for voltage assisted (anodic) bonding of borofloat glass to silicon: A stack of two wafers (or more) is maintained aligned in a vaccum chamber during the following sequence: chamber purging with N2, chamber pumping (optional), heating of the bonding plates, application of pressure and electric field between the two substrates, cooling down.
In addition, the tool can also be configured for other bonding methods, which do not require an electric field such as eutectic bonding (metal interlayer) or adhesive/glue bonding (parylene, polymer interlayer).
Original recipes were extended to many methods of wafer to wafer bonding but optimization of recipes other than the original anodic bonding is not trivial. Mainly, residual alignment shifts are observed depending on the intermediate layer thermo-mechanical properties.
The SB6 tool is not adapted for direct wafer to wafer bonding (fusion bonding). Tool pressure and temperature settings/uniformity are not in the correct range for this kind of process.
II. Equipment description
The tool consists in:
- A vacuum chamber, with primary pump and N2 purge : pmin = 3 mbar
- Two heated pressure plates : Tmax = 450°C, Pmax = 650 kPa
- High voltage supply (10mA limit, 2 kV max)
- Load lock and fixture for loading of pre-aligned wafer stacks
- Fixture compatible with MA/BA6 for fine alignment (< 2um)
- PC for recipe edition and process control
- For safety reason, loading / unloading is controlled from the PC interface. Manual top loading is strictly forbidden.
The fixture consists of 3 x 120 deg. clamp and spacer units, which are pneumatically activated during processing in the chamber.
The bottom plate/electrode will fit in the central hole just after loading.
N.B. An additional side electrode can be used for tripple stack bonding (on the left of image), e.g. Glass/Si/Glass or SOI to Glass. Ask the staff for guidance!
Top plate description:
The top pressure plates comes in two different types: plate with center hole for optimized anodic bonding (central electrode), or full plate for other bonding methods.
The default top plate has a hole in the center to make room for the central electrode, initiating the anodic process in the center of the wafer stack. It can also be used with other bonding methods to reduce residual alignment shift during heating/pressure process steps.
The modified top plate is full and is used with methods other athan anodic to improve pressure and temperature uniformity in the center.
Wafer material and cross-contamination:
Authorized material are (d=100mm) silicon and/or borofloat 33 (pyrex) wafers. Other type of fused quartz or glass wafers will break during the process due to thermal mismatch with silicon.
Cross-contamination risks are reduced by changing both bottom and top heater/pressure plates for each type of configuration. This change of configuration need careful attention for correct distance and leveling of the bottom plate. This operation is performed daily only by the CMi lithography staff.
Available configurations are:
|A_T350_480||Anodic bonding standard|
|G_T70 _175||Glue bonding low temperature (SU8 etc…)|
|G_T220 _340||Glue bonding high temperature (Polymères)|
|ALDlayer_T300||ALD oxide (Al2O3, …) full area upper electrode|
|Eutectic T410_450||Eutectic bonding (Au-Si)|
Make sure to use your CMi equipment booking interface to reserve the correct configuration (use the “Reservation and config. request” button)