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The MA/BA Gen4 series represents the latest generation of SUSS MicroTec’s semi-automated mask and bond aligner and introduces a new platform system. The two platform types differ in configuration, and consist of the MA/BA Gen4 for standard processes and the MA/BA Gen4 Pro series dedicated to advanced and high-end processes.
The MA/BA Gen4 series is the entry-level model, available as MA/BA6 Gen4 and MA/BA8 Gen4. With its enhanced ergonomic and user-friendly design, cost efficiency and reduced footprint, it is the perfect tool for use in research and low-volume production.
SUSS MicroTec’s MA/BA Gen4 series is setting a new benchmark in full-field lithography for academia, MEMS & NEMS, 3D integration and compound semiconductor markets. It is also prepared to handle processes like bond alignment, fusion bonding and SMILE imprinting.
Processes developed on the MA/BA Gen4 series can be quickly transferred onto SUSS MicroTec‘s automated mask aligner platforms for high-volume production.
Outstanding process results
High user friendliness
Low cost of ownership
The MA/BA Gen4 series’ high degree of automation enables outstanding process results. Functions such as constant dose mode, an automated control unit for exposure time as well as auto alignment all help optimize process parameters. Additionally equipped with the high-grade MO Exposure Optics system, the MA/BA Gen4 series provides ideal exposure conditions and thus achieves top results. Sophisticated mechanical workings ensure high adjustment precision: a special design of the top- and bottom-side microscope unit (TSA and BSA) eliminates the long travel of the TSA microscope and the disturbing vibrations.
Functions such as a highly ergonomic recipe editor and the sophisticated data logging or the ability to assign user rights simplify the operator’s work and simultaneously minimize sources of errors. The MA/BA Gen4 platform also makes use of high-grade digital microscopes and cameras, which significantly simplify the adjustment process thanks to enhanced image quality and an enlarged field of view on the monitor.
Work safety and environmental protection
The MA/BA Gen4 series can optionally be equipped with an energy-efficient LED light source, which not only reduces operating and maintenance costs, but improves work safety and environmental protection as well. This eliminates expensive hazardous waste disposal for mercury lamps. The machine offers further security features, such as UV radiation protection, safety interlocks, trap protection, thus fulfilling strict safety requirements.
A major factor for the attractive cost of ownership of the MA/BA Gen4 series is that it has a small footprint and still offers a wide variety of processes. This includes operating and maintenance expenses, which can be reduced by such means as using an optional energy-efficient LED light source. The highly robust design, easy accessibility of operating elements and replaceable parts, as well as the use of the LED light source and SUSS MicroTec’s MO Exposure Optics reduce maintenance expenses for the MA/BA Gen4 platform. Remote-controlled access to the machine can also be used to detect and rectify sources of errors in a cost-effective manner.
Additional functions such as wafer-to-wafer adjustment, fusion bonding and imprint lithography can be added as optional upgrades.
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
Multilayer wafer stacks are used in a number of structuring processes. By means of infrared (IR) illumination, the alignment marks that in the typical case are embedded between the layers can be identified and aligned.
Alignment can also be done using IR light based on such embedded marks. These require the use of materials that are transparent for IR light, such as undoped silicon, III-V semiconductors (e.g. GaAs) and adhesives for temporary bonding and debonding techniques. Specific cases should be tested to verify process feasibility.
In order to ensure availability of IR alignment to the greatest possible extent, the SUSS mask aligner can be optionally equipped with powerful IR light sources and high performance camera systems.
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 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
Auto Alignment is based on a motorized alignment stage. The COGNEX® based pattern recognition software automatically recognizes wafer target locations and controls the movement of the alignment stage. Coupled with SUSS MicroTec‘s DirectAlign® accuracies down to 0.25μm can be achieved. Auto Alignment enables highest repeatability of process results coupled with optimized throughput and minimum operator intervention.
Assisted Alignment represents the latest development for operator assisted, semi-automated alignment. During manual alignment the COGNEX® based pattern recognition software continuously measures the achieved accuracy and reports it to the operator. With its sub pixel resolution the system supports highest alignment precision, prevents misalignment and maximizes yield.
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.
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.
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.
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.
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.