Wafer Bonding

Bonding refers to attaching two or more substrates or wafers, of materials such as glass or silicon, to each other by means of various chemical and physical effects. Wafer bonding is mainly used in MEMS, where sensor components are encapsulated in the application. Other markets for this technology include advanced packaging, 3D integration and CIS manufacturing. Temporary bonding is a specialized technology within wafer bonding that is regarded as a key technology for 3D integration.

Adhesive Bonding

A variety of  materials are available for bonding techniques utizilizing polymers and adhesives, including epoxies, dry films, BCB, polyimides, and UV curable compounds.

Features and Benefits

  • Relatively low temperatures help protect sensitive components

Automated Systems

Manual Systems

Anodic Bonding

Anodic bonding involves encapsulating components on the wafer by means of ionic glass. In triple-stack bonding, three layers (i.e. glass-silicon-glass) are simultaneously bonded, enhancing both functionality and yield. This requires first a laser pre-bonding process to attach a glass wafer to the silicon wafer at certain points.

Features and Benefits

  • Bond is hermetically sealed and displays good resistance to thermal and chemical effects

Manual Systems

Eutectic Bonding

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.

Features and Benefits

  • High mechanical strength
  • High resistance to thermal and chemical effects

Automated Systems

Manual Systems

Fusion Bonding

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.

Features and Benefits

  • Less process time required
  • Low temperatures protect sensitive components

Automated Systems

Manual Systems

Glass Frit Bonding

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.

Features and Benefits

  • Low production costs

Manual Systems

Metal Diffusion Bonding

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.

Features and Benefits

  • Highest level of impermeability among all common bonding processes
  • High alignment precision following bonding

Automated Systems

Manual Systems

  • SB6/8e

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