Substrate bonding
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Substrate bonding refers to attaching two or more substrates of material such as glass or silicon, to each other by means of various chemical and physical effects. Substrate bonding is mainly used in MEMS, where sensor components are encapsulated in the application. The most common types of bonding are adhesive, anodic, eutectic, fusion, glass frit, direct wafer or fusion bonding, and metallic diffusion.
Contents
Technologies
There are 7 primary methods which define substrate bonding technology. These have been mentioned above and are described in detail below.
Adhesive bonding
Uses a layer of polymer or adhesive, including epoxies, dry films, BCB, polyimides, and UV curable compounds between the substrates to bond the substrates together. This introduces a foreign material between your substrates, but there is a wide variety of materials that can make this method desirable for it's extremely wide range of temperature and control.
Relatively low temperatures help protect sensitive components
Anodic bonding
This type of bonding involves encapsulating components on a silicon wafer by means of ionic glass. When ionic glass is heated, it becomes increasingly less insulating. When a high voltage is applied, current is able to flow which causes the migration of the ions in the glass.
Bond is hermetically sealed and displays good resistance to thermal and chemical effects Very reliable bond, probably the most forgiving with substrate flatness
Technology 3
Eutectic wafer bonding takes advantage of the special properties of eutectic metals. Similar to soldering alloys, such metals melt already at low temperatures. This property allows planar surfaces to be achieved.
In order to control reflow of the eutectic material, eutectic bonding requires precise dosing of the bonding force and even temperature distribution.
High mechanical strength High resistance to thermal and chemical effects
Technology 4
Fusion bonding refers to spontaneous adhesion of two planar substrates. The process involves rinsing the polished discs and rendering them largely hydrophilic, then placing them in contact and tempering them at high temperatures. Plasma pretreatment allows the substrates to be bonded at room temperature.
Less process time required Low temperatures protect sensitive components
Technology 5
This process involves screen-printing glass frits onto the bonding surfaces. This results in structures that are subsequently heated and fused when the two substrate surfaces are placed in contact. On cooling, a mechanically stable bond results.
Low production costs
Technology 6
Metal diffusion bonding is based on Cu-Cu, Al-Al, Au-Au and other metallic bonds. In addition, the use of metal diffusion allows two wafers to be bonded both mechanically and electrically in a single step. The technique is required for bonding in 3D applications such as 3D stacking.
Highest level of impermeability among all common bonding processes High alignment precision following bonding
Technology 7
Here's another technology in that group.
Figures of Merit
What is important to look for in the technology? Etch/dep rate? Resolution?
FOM 1
Subheadings are optional.
Applications
How is this technology used in nanofabrication and what types of devices/research areas is it useful in?
Equipment
Specific equipment for each technology can be found on its page above. Additionally, below is a list of all metrology equipment in the LNF:
See also
Other related wiki pages
References
Further reading
- Other stuff, e.g. technology workshop slides
- External links (can be in another section below, if appropriate)
