MA300 Gen3 Mask-Aligner

Top-side alignment (TSA)

Where lithographic processes require the alignment of structures on only one side of the device wafer (e.g. RDL, micro bumping, 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 DirectAlign® system invented at SUSS.

Highlights

• Mask aligner for the highest level of alignment precision
• Clear and stable pattern recognition even under poor contrast conditions

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 4 µm in size for 300 mm tools and down to 3.5 µm and 3 µm for 200 and 150 mm tools, respectively. 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 are based on proximity lithography.

Features & Benefits

• Superior resolution as a result of diffraction-reducing optics
• Process stability through the use of microlens optical systems

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.

Highlights

• Excellent light uniformity over full exposure field
• Stable light source
• Customizable illumination by means of illumination filter plate exchange
• "DUV-ready" process capabilities with fused silica micro optics
• Special "down-sizing kits" for light compression to smaller wafer sizes

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.

Automatic Mask Management System

The mask library stores several photomasks in a controlled environment. Furthermore, the system automatically detects and chooses the correct mask layer and takes over activation and deactivation.
Utilizing the mask library allows operator errors to be minimized and platform productivity to be improved overall.

Overlay accuracy regularly suffers considerable degradation due to the thermal run-out between photomask and the wafer. The SUSS compensation system ThermAlign® ensures a constant temperature on the wafer chuck and additionally provides a stabilizing influence on the mask temperature. ThermAlign® compensates for run-out effects by adapting the temperature to the process conditions.

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 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, verification, and optimization. At the same time, it covers all the process steps, from illumination shaping and mask layout optimization up to photoresist processing. Additionally, modern 3D simulation functions improve the model visualizations.

The combination of MO Exposure Optics and the SUSS optics custom-developed optical models in the Lab facilitates customer-specific design optimization of the exposure filter plates, which in turn leads to an improvement in pattern fidelity.

Highlights

• Complete simulation of the mask aligner lithographic process
• Adjustable illumination parameters (collimation, spectral composition), custom-developed for all SUSS optics
• Fast and flexible visualization and quantitative predictions in 1, 2 and 3D

Controlled Local Process Environment

To meet exceptionally high reliability requirements in the manufacture of microstructures, the optional SUSS filter unit offers improved ambient air stability and quality in the unit by creating an effectively sealed process environment within the unit housing.

The process environment is therefore largely decoupled from varying clean room conditions. The generated environment holds fewer particles which has a positive effect both on process stability and thus product quality, contributing to increased effectiveness as well as cost reduction.

The mask aligner is designed for integration into a fab automation system compatible to the SECS-II/GEM interface standards. Level and details of the communication will be specified on basis of the SUSS core software solution.