The XB8 wafer bonder is designed for a wide range of bonding processes and supports substrates with a wafer size of up to 200 mm. All process parameters can be adapted flexibly according to the requirements, which make the system perfect for use in research and development. In production, the high level of automation and the sophisticated design of the XB8 ensure a high level of process stability. This makes the XB8 wafer bonder ideal for applications from the MEMS, advanced packaging, 3D integration and LED fields.
Flexibility in process development
The XB8 wafer bonder has a closed process chamber with an automatic loading function. During loading, the chamber is flooded with nitrogen to ensure the best possible level of cleanliness. The high level of automation minimizes the influence the operator has on the process result. The thermal decoupling of the heater from the actual bonder chamber enables a process temperature which can be reproduced precisely, combined with a high repeat accuracy of the bonding force.
Homogeneous Temperature and Bond Force
The thermally decoupled ceramic heaters guarantee an even temperature distribution and also ensure an optimal bonding force homogeneity within the entire temperature range. The SUSS MicroTec unique multi-zone heating system makes advanced control of the temperature distribution possible. The innovative structure of the XB8 wafer bonder enables optimal bonding force and temperature distribution across the wafer, resulting in high yield.
In combination with the SUSS bond aligner suite the XB8 offers a highly precise bond alignment.
The XB8 wafer bonder offers various tooling options.
The force-free spacer removal ensures best post-bond-alignment, when spacers are required for the bond process. The sequential spacer removal option gives the operator maximum flexibility to control the removal of spacers.
The design allows an individual removal of each of the three spacer controlled by the bond recipe. During the removal sequence, the clamp at the respective position is lifted from the wafer stack, the spacer is removed and afterwards the clamp is set again to secure the alignment.
The XB8 wafer bonder has a closed process chamber with an automated fixture loading function. During loading, the chamber is flooded with nitrogen to ensure the best possible level of cleanliness. Operators have minimum influence on the process result due to the high level of automation. The heater is thermally decoupled from the actual bonding chamber. This enables process temperatures which can be precisely repeated, combined with an optimal repeat accuracy of the bonding force. The independence from the operator and the sophisticated design of the XB8 wafer bonder guarantee consistently high process stability and an optimal process result.
A variety of materials are available for adhesive wafer bonding techniques utilizing polymers and adhesives, including epoxies, dry films, BCB, polyimides, and UV curable compounds.
Anodic wafer 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.
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.
Fusion bonding refers to the spontaneous adhesion of two planar substrates with a dielectric material (typically silicon oxide) as the bonding layer. The process usually involves a proper surface activation that renders the substrates largely hydrophilic. Subsequently, the substrates are aligned, brought into contact and finally tempered at elevated temperature.
Glass Frit Bonding
A glass frit bonding 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.
Hybrid bonding is an extension of fusion bonding, so that in addition to the dielectric material also metallic structures can be found in the bonding interface, which are bonded by diffusion during the annealing process. Successful bonding requires very careful control of the metal structure topography.
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.
SLID bonding (solid-liquid inter-diffusion) is based on diffusion and the mixture of different metals. The melting temperature of the alloy after bonding is very much higher than the bonding temperature, which clearly widens the range of possible applications.
The bond head includes a center pin, which allows establishing contact between both wafers at their center points. This helps to maintain excellent alignment even after thermal expansion of the bond partners. The center pin is used to initiate a fusion bond in the center of the wafer stack or to set a pre-bond for anodic bonding to avoid dejsutage when pulling the spacers.
The bond head offers excellent temperature and bond force uniformity and maintains excellent post-bond alignment in combination with SUSS proprietary sequential spacer removal technology. This bond head and tooling design enable optimum yield due to minimal exclusion zones.
The open fixture features a transport ring with minimum contact area for wafer support and maximized cut-out area for reduced thermal mass during heat up and cool down. This type of fixture allows direct contact between the wafers and the lower and the upper tooling plate, which results in optimum temperature uniformity across the wafers. In addition, this enables optimal heating and cooling rates and is therefore the best choice for high throughput applications.
Featuring a transport ring with an integrated ceramic SiC tooling plate closed fixtures are designed for handling irregular substrate shapes as well sensitive material such as lithium tantalite. The closed fixture is ideal for fragile substrates like MEMS and optical devices as the wafers are fully supported and protected during handling.
The multi-bond fixture is used in combination with a special loading and mechanical alignment system and supports multi-wafer bonding and multiple wafer sizes at the same time. Bonding multiple wafers in the same bond cycle allows to maximize the overall system throughput.