The MA/BA Gen4 Pro mask and bond aligner is the all-rounder of all SUSS MicroTec's semi-automated mask alignment equipment, and thus offers a wide range of application possibilities. It supports substrate sizes of up to 150 mm and 200 mm. Thanks to numerous tools and options, as well as settable process parameters, it offers maximum flexibility for research and development or production processes. A fully developed design and leading edge technology make the MA/BA Gen4 Pro series the ideal platform to develop future technology. Thus setting new standards for MEMS, advanced packaging, 3D integration and compound semiconductor applications.
High alignment precision and resolution
Large process range
Maximum process control
The MA/BA Gen4 Pro series is easy to integrate into production environments and is highly compatible with SUSS MicroTec’ s automated mask aligners. Therefore, a process transfer from development to production is easily made. It stands out through its well designed functionality (it is an industry standard) and a high degree of functional automation. Automated pattern recognition and alignment supports a high production rate and low scrap rate.
High resolution optics and exposure systems as well as the most modern alignment processes make the MA/BA Gen4 Pro series a valuable tool when venturing into uncharted territory. It supports several imprint processes for micro and nanostructures. With only a little adaptation, it allows wafer-to-wafer alignment, easy fusion bonding as well as pre-process plasma treatments of the substrate surface.
Where lithographic processes require the alignment of structures on only one side of the device wafer (e.g. RDL, microbumping and similar techniques), top-side alignment is used to align the fiducials on the mask with those of the wafer. Depending on substrate properties, this can be achieved either using stored position data for the wafer or through live image alignment, as in the DirectAligntm system invented at SUSS MicroTec.
Bottom-side Alignment (BSA)
Alignment of the structuring on the wafer back side with the structures on the front is required in processes involving applications such as MEMS, wafer-level packaging and 3D integration, where used for example to create vertical through silicon vias (TSVs) on interposers. Optical bottom side alignment is normally used for this type of alignment. An integrated camera system detects the mask structures and the structures on the wafer back side and aligns them with each other. The wafer position has to be determined and stored prior to loading, since the wafer afterwards conceals the mask target. This places specialized demands on the alignment system as a whole.
Features and Benefits
Enhancing Alignment Precision
When stringent demands are made of overlay accuracy, the auto-alignment functionality of the standard system can be considerably refined. DirectAlign®, the SUSS MicroTec enhanced functionality for structure detection software, uses live images instead of patterns from an image memory system. The technology is based on the industry standard PatMax and achieves outstanding results. Using DirectAlign® for top-side alignment on a SUSS mask aligner allows accuracy of 0.5 µm to be achieved.
The use of Enhanced Alignment is recommended for challenging alignment processes with easily confused structures or restricted fields of view.
A mask with a certain structure is aligned with the wafer in very close proximity (thus “proximity” lithography). During exposure, the shadow cast by the mask structure is transferred to the wafer. The resulting exposure quality depends on both the precision with which the mask and wafer are spaced apart and the optical system used for exposure.
Being fast and suited to flexible implementation, this method is regarded as the most cost-effective technique for producing microstructures down to 3 µm in size. With contact exposure, resolutions in the sub-micron range can be achieved. Typical areas of use include wafer-level chip-scale packaging, flip chip packaging, bumping, MEMS, LED and power devices. The systems are deployed in high-volume production as well as in industrial research.
The mask aligners supplied by SUSS MicroTec are based on proximity lithography.
Features & Benefits
The lower the exposure gap from mask to wafer, the higher the resolution. In soft contact mode the wafer is brought into contact with the mask and is fixed onto the chuck with vacuum.
In hard contact mode the wafer is brought in direct contact with the mask, while positive nitrogen pressure is used to press the substrate against the mask. In hard contact mode a resolution in the 1 micron range is possible.
The large gap optics (LGO) optics is optimized for thick resist processes with large exposure gaps and 3D lithography, offering a resolution down to 5μm. The high resolution optics (HR) is apt for contact and close proximity lithography with structures down to 3μm at 20μm exposure gap. For processes with high dose requirements on 150mm wafers the exceptionally high intensity of the W150 HR optics facilitates high throughput.
The diffraction reducing exposure optics is designed to compensate diffraction effects in both contact and proximity lithography. Instead of using a plane wave as in other proximity lithography tools it provides an angular spectrum of planar light waves to reduce diffraction effects. The selection of a proper angular spectrum improves structure resolution in the resist.
MO Exposure Optics® is a unique illumination optics specifically designed for SUSS mask aligners. It is based on micro-lens plates instead of macroscopic lens assemblies. A simple plug & play changeover allows for a quick and easy changeover between different angular settings including the functionality of both classical SUSS HR and LGO illumination optics.
The telecentric illumination which is provided by the MO Exposure Optics improves light uniformity and leads to a larger process window. In consequence, this causes yield enhancements. MO Exposure Optics also decouples the exposure light from the lamp source thus small misalignments of the lamp do not affect the light uniformity. A decoupled light source saves setup and maintenance time and guarantees uniform illumination conditions during the full life-time of the lamp.
SUSS mask aligners are equipped with a WEC head system that allows reaching the parallelism between substrate and mask with a micrometric precision.
The mask aligner optionally offers an automatic filter exchange unit for up to four filters that are selected via process recipe. This removes the risk of operator errors and thus improves yield and effective throughput.
Simulation of lithographic processes
A simulation of lithographic processes makes the selection of optimal settings for process parameters possible without long-winded trial and error sessions. The multi-functional simulation software of lithographic processes “Lab”, which SUSS MicroTec distributes together with the supplier, GenISys, first and foremost allows the operator better process control. It offers all the required simulation functionality for an integrated design and process development, as well as verification and optimization. At the same time it covers all the process steps from illumination shaping and mask layout optimization up to photo resist processing. Additionally, modern 3D simulation functions improve the model visualizations.
The combination of MO Exposure Optics and the for SUSS optics custom-developed optical models in Lab facilitates customer-specific design optimization of the exposure filter plates, which in turn leads to an improvement in pattern fidelity.
Customer Specific Illumination Shaping and Mask Layouts
Combining optimization of mask layouts and the light source (source mask optimization), a procedure from projection lithography, makes it possible to reduce pattern inaccuracies due to illumination errors, processing artifacts and diffraction. A combined selection to match the exposure filter plates with the mask patterns (OPC = optical proximity correction) to customer specific requirements allows considerable expansion of the lithographic process functionality.
A simulation platform permits modeling of process parameters such as mask patterns and illumination parameters. This facilitates the exposure and mask patterns to be set for specific production situations with a reduced experimental effort, and reduces illumination and process errors.
Source mask optimization, together with SUSS MicroTecs customizable MO Exposure Optics® form an important contribution to improvement of process stability in mask aligner lithography.
Light Source of the Future
The new lamp house concept from SUSS MicroTec convinces with efficiency - UV-LED light sources reach many times the service life of conventional mercury vapor lamps. Moreover, they no longer need to warm-up and cool-down - the LED is only switched on during exposure. These factors significantly contribute to comparatively low energy consumption. And unlike mercury vapor lamps, they require no cumbersome hazardous-waste disposal.
The SUSS UV-LED lamp house features the latest in technology and thus meets the growing demand for environmental sustainability and energy efficiency.
The use of an LED lamp house significantly affects the operating costs of a Mask Aligner. The service life of an LED exceeds that of conventional lamps many times over, thereby lowering costs generated by changing lamps. Downtimes, acquisition of new lamps, adjustments and disposal of old material have become a thing of the past.
Guaranteed Process Flexibility
Compared to conventional mercury vapor lamps, LED light sources not only work more efficiently but are also much more flexible to use. The UV-LED lamp house generally covers the same spectral region as mercury vapor lamps. The difference is that the UV-LED can switch specific wave lengths on and off. This eliminates the need to optically filter the light outside of the lamp house. Wave lengths are regulated via programed formulas which fulfill specific process requirements without filter change or recalibration.
When interacting with SÜSS MicroTec's special optics MO Exposure Optics, the LED lamp house provides for maximum flexibility in process design.
Working with the LED lamp house is both safe and environmentally sound and is a major step up in health and occupational safety, as well as in environmental protection.
Imprint lithography represents a cost-effective and highly reliable means of transferring three-dimensional nano- or micro-scale patterns onto a wide variety of substrates.
For the imprint, a stamp is brought into contact with a photosensitive material on the substrate. The photoresist fills out the three-dimensional pattern of the stamp and then solidifies under UV light. Parameters such as pattern topography, structure resolution and aspect ratio have a considerable influence on the process quality.
Thanks to its compatibility to well-established semiconductor processes, imprint lithography plays a key role in the development and production of DFB lasers, HB LEDs, wafer-level cameras and MEMS.
SUSS MicroTec solutions for imprint lithography are based on manual mask aligner platforms and support a wide range of materials and substrate with sizes up to 200 mm. Furthermore, SUSS platforms provide the capability of aligning and levelling stamps to substrates, as required by many imprint applications. Imprint equipment can also be retrofitted to SUSS mask aligners which are already in the field.
Depending on process requirements, SUSS MicroTec offers different imprint technologies on its mask aligners.
SCIL (substrate conformal imprint lithography) technology is particularly suitable for high demand imprint processes. Here a soft stamp is used in combination with a hard but flexible glass carrier, thereby achieving superior evenness of contact and exceptionally high fidelity in pattern transfer.
Imprinting results from capillary forces rather than pressure so that any changes in structure are avoided during the contact process. Furthermore, the sequential contact routine does not allow air gaps to form, which results in extremely high yields and increases productivity.
As a result of its excellent structure replication and high uniformity, SCIL technology is suited for all highly demanding processes where a high-quality etching mask is employed, such as the production of optical elements and MEMS/NEMS as well as in the production of HB LEDs and VCELS. SCIL technology was developed in collaboration with Philips Research.
Semi-Automated Mask Aligner
Micro- and Nano-Imprinting
For the transfer of patterns in the micro- to nanometer range, SUSS MicroTec offers SMILE (SUSS MicroTec imprint lithography equipment) technology.
There are two process variants, the use of which depends on the desired resolution.
The process allows very precise exposure of both micro- and nano-patterns, thereby offering a wide spectrum of potential applications and thus excellent process flexibility. SMILE is used for example in the production of MEMS and optical lenses for wafer-level-cameras.
Using UV-NIL (UV nano-imprint lithography) SUSS MicroTec offers a classic imprint process to transfer patterns having a resolution down to 50 nm with superior fidelity. The transfer of the patterns is achieved using a hard quartz glass stamp, which is brought into contact with a UV-sensitive photoresist on the substrate. This setup allows very precise control of process parameters such as pressure, process gap and duration. The UV-NIL method allows the highest resolution of the three SUSS MicroTec imprint processes and is recommended for all R&D setups due to ease of use.
Wafer preparation for fusion bonding processes is a frequent plasma treatment application using the SELECT plasma tool from SUSS MicroTec. Pre-treatment ensures superior bond quality and at the same a high bond yield.
In wet chemical and/or plasma processes, organic and particle contamination is removed, while the bonding surface is also rendered reactive, thus allowing stronger bonds to be achieved. Following these pre-treatment steps, post-bonding annealing can take place at temperatures far below 450 °C, This ensures the CMOS compatibility of the bonding process.
In a joint development project, SUSS MicroTec and Fraunhofer IST have developed a technology for local plasma treatment that allows the selective activation of micrometer-size wafer areas where functional layers can be deposited. The technique opens up new options for designing and manufacturing components, in particular for MEMS applications such as microfluidic channels, biochip manufacturing and component encapsulation.