Final Report Summary - WAFERLEVELOPTICS (WaferLevelOptics - Specific Technological Developments to Create an Intelligent and Scalable Production Platform for Glass Optics Manufacturing)
Micro optical components and systems often serve as an important enabler for innovative products in the laser, life science or biotechnology market. At this point the role of glass micro optics becomes more and more important. Advantages of ultra precise optical components made of glass e.g. are their resistance against environmental impact, their biocompatibility and their capability of being used in high power applications. The ongoing miniaturization and the continuously growing quantities are only two issues which let to a change in optics manufacturing within the last decade. Direct manufacturing techniques such as grinding and polishing could no longer meet the requirements of the demanded micro optical components, so the precision glass moulding was set up to keep step with the technical developments in optics design. By applying this manufacturing technique large quantities of ready-to-use and highly precise optics (form accuracy << 1 µm PV, surface finish < 10 nm Ra) can be produced.
The manufacturing of thousands of computer chips on one silicon wafer enabled an enormous reduction of manufacturing costs and at the same time lowered the handling complexity as well as the system integration costs. Derived through this example the motivation of the WaferLevelOptics project is to build up the same economies of scale for the precision glass moulding process. Moulding multiple micro optics on one glass wafer, stacking those wafers to optical systems, bond and finally dice them will be the future alternative for micro optics manufacturing.
The overall objective of the project WaferLevelOptics is to essentially strengthen the European optics manufacturing by significantly increasing the flexibility and product spectrum. Therefore, a new and efficient technology for the replicative manufacturing of glass micro optics is developed. In total, the precision glass moulding process chain is pushed towards the replication of wafer scale glass optics. Thus a scalable manufacturing platform for the replicative manufacturing of glass micro optics is created.
Project Context and Objectives:
The different scientific and technological objectives that have to be accomplished are the following:
1. Optics design and tolerance management
Since there is no state-of-the-art process in manufacturing wafer scale glass optics the goal of the project is to develop new design rules to assure the final quality of the moulded glass wafer and therewith guarantee the success of the whole production platform. Here, especially the restrictions derived from the FEM process simulation must be considered. Further on it is absolutely crucial to generate modular design guidelines to meet the request of a large variety of wafer scale optics.
2. Process simulation and mould design
The FEM process simulation enormously helps to reduce the production costs for moulded glass optic by predicting the glass shrinkage as well as the glass flow behaviour. Within the WaferLevelOptics project the currently available simulation tools will be scaled to transfer the state-of-the-art knowledge towards wafer scale simulation. Further on, new developments regarding the simulation of the glass flow behaviour and the internal stresses in the wafer optic will be accomplished. Thus, detailed analysis regarding the feasibility and the design rules for the moulds in terms of macro and micro geometry can be derived. Finally, the simulation tool will be able to handle the simulation of single optical elements as well as wafer optics and therewith support the scalable manufacturing platform of precision glass moulding.
3. Mould manufacturing
The tungsten carbide used as the mould material in the glass moulding process can - due to its characteristics (brittleness, hardness, ect.) - not be easily machined. Additionally, the normal size of a state-of-the-art glass mould will not excess at most 2” today. Aiming the realization of a 4” moulded glass wafer within this project the emerging challenges can be derived. The goal of this section in the process chain will be the development of a machining process capable to manufacture the customized moulds within the tolerances requested by the optic designer and an acceptable machining time. Therefore, new reconfigurable grinding techniques will be developed, evaluated and optimized.
To further lower the manufacturing costs alternative process concepts will be tested. Therefore special machining equipment (chuck system) will be developed.
The goal for the process step “Moulding” is to build up a profound knowledge based process know-how for the replication of wafer scale glass optics. Based on the process experiences for single or multi cavity moulding the know-how will be continuously scaled up towards the replication of wafer scale optics. Finally, the expertise along the whole range of moulding processes will enable the easy up- and downscale of the manufacturing chain. Here cost efficiency and flexibility in volume and product features are the main objectives.
5. Wafer stacking, alignment, cementing and qualification
The main objective concerning the stacking and alignment of the moulded glass wafers is to develop an integrated new solutions for automatic handling of large volumes of glass wafers integrating small micro optical elements by using high precision positioning and handling techniques. The planned assembly and packaging device will on the one side be able to stack multiple glass wafers and at the same time align them to get best performing optical system.
6. Quality control
With regard to the complexity and accuracy linked to the manufacturing of precise micro optics in general a quality control system to assure a high quality standard for the whole production platform is absolutely essential. Therefore the WaferLevelOptics project is targeting the development of a modular quality control process accompanying each single process step of the production platform.
WP2: The major achievement of work package on the one hand is a tolerancing guideline for wafer level glass optics. The document explains the way micro glass lenses could be manufactured on wafer scale applying the precision glass molding process. It supports optical designers with guidelines for the design of such micro optics. Thus they will be enabled to adapt their design competences to the restrictions of the wafer level molding process. On the other hand a FE based simulation tool for the computer based simulation of the wafer level molding process is an outcome of WP2. The FE tool allows the user to simulate the forming of the wafer. Thus he is enabled to derive ideal mold and glass preform design. At the same time the user can see problems that might come up during the forming stage and is able to intervene my re-designing either the process layout or the mold. Such a-priori observation of the process allows for time and costs savings.
WP3: The first major result of WP3 is a new, nano-grained cermet based material that can be used as a substrate material for wafer level molding tools. While at the beginning of the project a conventional binder free tungsten carbide grade was used as a mold material, the newly developed material shows a coefficient of thermal expansion closely to the one glass normally has. Thus, problems caused by differences in shrinkage of the mold and the wafer can be overcome, glass breakage is lowered and the molding process is much more stable.
For the mold manufacturing itself, different grinding process strategies were developed and evaluated towards economic feasibility. It was observed which strategy is suitable for what kind of wafer lens geometry. Finally an overview about the advantages and disadvantages as well as the capabilities of every grinding strategy is summarized. Thus, the mold manufacturer is given a guide line of how to efficiently manufacture wafer level molding tools.
In order to program the ultra-precision grinding machines needed to machine the wafer level molding tools, a software tool was developed. This software can be named as another major achievement of the work conducted in WP3. It allows also un-experienced users to define a grinding job using the easy entry mask of the software tool. Also an inclusion of metrology data is possible. Thus, it is possible to feed back metrology data into the machine and allow for an adaptive machining and therewith a higher accuracy of the molding tools.
The last important result of WP3 is a chuck system developed for easy and highly accurate clamping of the wafer level molding tools within the grinding machine or different metrology devices. The system allows clamping in the sub-micron range and can easily be adapted to different machines.
WP4: Within the wafer level optics project it could be demonstrated for the first time that molding a glass wafer with multiple highly accurate micro optics is possible. Designing and lay outing the molding process (the force and path control, as well as the heating and cooling cycles) was the major achievement of this WP. The process know how gained here allows for a stable and reliable wafer level molding process even though adaptations are still needed since the geometry and the size of the lenses on the wafer and the type of glass used for molding are influencing the molding process.
WP5: The assembly and alignment of wafers by hand is a time consuming process with a low repeatability. Automating this process was the goal of WP5. By designing and building a wafer cementing device as well as an alignment machine, this goal could be successfully reached. First a wafer can be applied with glue within the automated nano-dispenser unit. The wafer can be put it the device and the glue is dispensed precisely on the wafer. Afterwards a second wafer can be packed on the first one and the stack is transferred to the alignment device. Here the rough alignment is conducted using cross marks molded on the glass wafer. Then, based on wave front metrology, the two wafers are aligned with highest precision. By switching on a UV light source finally the glue is cured and the wafers are cemented together.
WP6: To ensure the quality of the newly developed production platform, the crucial process steps were identified and a custom documentation sheet (excel based) was designed.
All technical development led to the realization of a demonstrator. While at the beginning of the project two demonstrators were planned, only one could be assembled due to delays that could not be overcome within the duration of the project. The LED demonstrator, a high power LED collimated by a glass lens manufactured on the newly developed manufacturing platform was presented by OSRAM. The lenses could be manufactured to the expectations of the end user. OSRAM further more shows high interest in the lenses. If they would be available at the right price, a usage in OSRAM’s products is realistic. The second demonstrator should be a VGA camera module. All components, molded wafers as well as the electronics were available at the end of the project. Anyhow, there was no time left for assembly and testing.
For a more detailed description of the work accomplished within the project as well as the achievements please see the second technical periodic report.
The European photonics market recorded double-digit growth rates over the past years and is expected to more than triple within the next years reaching 500 billion EUR in 2013. Many important European industries, from information and communication, industrial manufacturing, life sciences and health to lighting and displays and security rely on the same fundamental achievements in the mastery of light. Without strong European leadership in photonics technologies, these industries will be left vulnerable to strong competition from the USA and Asia. It is estimated that at least two million of the European workforce, from solely considering the processing industry, is dependent on the photonics sector. Thus, concerted efforts are urgently required in order to strengthen European leadership in photonics.
WaferLevelOptics targets established and growing technologies and markets, such as improved and miniaturized imaging and sensor devices e.g. in cameras or endoscopes, new metrology devices in health care or laser diodes for multiple machining and automation applications with a total photonic share of over 45 billion EUR and market shares of more than 45%.
The WaferLevelOptics project and the idea of enhancing the currently available process chain of precision glass molding towards a scalable manufacturing platform is expected to have the following future impact:
By having developed a completely new approach to manufacture micro optics with precisions in the sub-micron range the WaferLevelOptics project essentially supports the competitiveness of the European optics industry. Due to the savings in production costs by applying this new manufacturing platform Europe will gain competitiveness toward the Asian competitors. As a conclusion Europe as a high waged region will again be in the focus for future investments in new optic manufacturing factories. Thus an economic growth of at least 0,1% in the optical sector (43,5 million EUR) can be expected as a direct impact of the WaferLevelOptics project within 5 years after termination of the project.
The impact of the WaferLevelOptics approach towards nano- and micro scale is two folded. On the one side there is the mold substrate material consisting of nano powders (grain size < 200 nm). The developments accomplished here will not only contribute the optics manufacturing. The results gained can be transferred to other products and therewith address multiple branches. On the other side there are the processes to machine and assembly the molds and the micro optics within precisions of sub-microns. Here, a profound knowledge regarding the production technology of micro-components is generated which carries an essential benefit for Europe as the center of sophisticated optics manufacturing.
Due to the fact that the WaferLevelOptics technology can be applied with the currently available production and metrology equipment, existing optics manufacturing factories are upgraded without cost intensive investments but only by applying the new processes developed in the WaferLevelOptics project. Further on, the developed stacking and alignment device supports the integration of multiple micro process steps.
The savings in optics production based on the advances in handling and assembly of the micro optics enables European high wage countries to be competitive in optics manufacturing. Further on, the flexibility and scalability the precision glass molding process chain obtains by the WaferLevelOptics developments will allow a fast reaction of optics manufacturer so that the market requests can be answered at any time.
Through the developments accomplished in the WaferLevelOptics project and the reduction in costs as a result from these developments, as shown above, will be an enabler for the strength of Europe as an NMT-location. Since not only the optics as the final product supports this strength but also the numerous developments along the process chain (simulation tool, mold substrate material, alignment device, ect.) the benefit and infrastructure generated by the WaferLevelOptics developments will widely contribute within the NMT area.
Finally, in the long term, these knowledge intensive processes of this new approach to manufacture micro optical systems applying the WaferLevelOptics technology offers the possibility to significantly win back the production of optical components and systems currently held by Asian optics manufacturer. Especially the attention of the Asian competitors to that newly developed production technology may contain multiple further chances for the European optics industry.
Due to the higher efficiencies of the WaferLevelOptics techniques and the achieved cost reductions an additional 0,1% market growth can be obtained in branches such as optical components and systems, information technologies, optical communication medical and life science as well as production technology (total market share 50%). This means an additional market volume of more than EUR 25 million.
Having the possibility to mold either one, 20 or even 100 glass optics in one molding cycle using the same production machines will enable the European optics manufacturer “production on demand” in Europe. The flexibility linked to this scalable manufacturing platform of precision glass molding enabled through the WaferLevelOptics developments will lead to faster reaction times of the European optics manufacturer. Therewith, the European optical market will attract further interests for outside Europe and increase the total market volume. Thus, Europe as a NMT-location for both equipment and production is clearly strengthened.
List of Websites:
Dr. Olaf Dambon
Fraunhofer Institute for Production Technology IPT
+49 (0)241 8904 233
+49 (0)241 8904 6233