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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - LOMID (LOMID - Large cost-effective OLED microdisplays and their applications)

Teaser

Summary

\"The LOMID project responds to the H2020 ICT3-2014 call for \"\"Advanced Thin Organic and Large Area Electronics\"\" by seeking to develop larger, higher resolution full-colour microdisplay chips than are currently available, which can also be bent, and to reduce their production costs. Such chips are required for head-mounted displays used for virtual or augmented realities and for electronic viewfinders used in a variety of optical equipment such as cameras.
In order to achieve the performance demands of the current and future markets, the project has elected to use the display technology of OLED on CMOS. Improvements to current processes must be made both for the CMOS backplane wafer (in order to achieve sufficient resolution, refresh rates and yield) and for the OLED deposition process (to reduce costs by improving yield). The LOMID microdisplay chips will enable the manufacture of more compact and comfortable head-mounted displays, initially for use in high-value professional products (for architecture, design, logistics and maintenance applications) rather than for consumer (gaming) products. Some of the challenges for the project include the very tight (nanometre) tolerances on roughness and step height variation for features on the CMOS silicon wafer, the need to reduce defect densities from the OLED process in order to make larger microdisplays affordable (cost increases roughly as the square of the display size for a given defect density), and the need to incorporate high speed video circuitry on a very small chip without loss of performance. A novelty of the project is the manufacture of display chips that can be bent to conform to a curved surface, giving more design freedom for optical designs (for more compact display devices).

In addition to creating European jobs for existing and emerging world-wide industries, the LOMID project will assess the utility of the new microdisplay chips for use in visual prosthetics consisting of a head-mounted display and camera, similar in form to a pair of sunglasses. For such medical devices which will be worn all day, the comfort is of paramount importance followed closely by the aesthetic appeal; any reduction of bulk or weight is therefore beneficial. Over two million people in Europe with severe visual impairment could benefit from such prosthetics, which would be used to compensate for poor vision e.g. by providing edge enhancement or clues about distance, eventually perhaps also face recognition or hazard warning.
The specific objectives of the LOMID project to be achieved by the development of new manufacturing processes are:
â€¢ conformable displays (with a bending radius of < 50 mm)
â€¢ durable and bright displays (lifetime of more than 15,000 hours at 1500 cd/m2)
â€¢ larger microdisplays than are currently available (2.54 cm screen diagonal)
â€¢ affordable microdisplay chips (yield > 60%, to enable a production cost of < 50 EUR/piece)
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Work performed

During the first eighteen months of the LOMID project, the consortium performed a cost-performance trade-off study and used this to fix the functional requirements and specifi-cations of the microdisplays, bearing in mind the most likely markets for the consortium members. A so-called Test and Qualification Vehicle (TQV) chip was designed - essentially very simplified version of the silicon chip that will be used for the microdisplays. This TQV was used to develop and test new silicon chip (CMOS) fabrication processes required to meet the requirements of the OLED part of the display devices. In order to meet the aims of the project, the consortium was extended slightly to include another factory from the XFAB group in order to allow access to faster, more power efficient chips.
Excellent progress has been towards improving the yield of the OLED manufacturing steps - although further long-term testing is needed, preliminary results suggest that the number of defects has been reduced by about 80%, a necessary step towards the very challenging objective of a 60% overall device yield.
A new process for depositing novel transparent materials (amorphous metal oxides) for use as transistors in thin film display devices has been developed, and promising results obtained from the characterisation of these materials. A new transparent protective coating has been developed, and used to show that similar chips can be bent to conform to a curved template.
Boundary conditions for a life-cycle analysis (LCA) have been defined to collect throughout the project relevant data.
The virtual reality and augmented reality markets continue to grow as forecasted, and the project members have kept a careful watch on these markets and the (non-) emergence of alternative technologies that would compete with the outcomes from the LOMID project.

Final results

\"At this stage of the project (half-way through), as planned, there are rather few outcomes to demonstrate progress beyond the state of the art (one quarter of the technical deliverables have been achieved, almost all on time). Such progress has occurred within the project, but almost entirely in process development and design. The first complete display devices for evaluation are expected within a few weeks (September 2016), and these will make evident some of the progress made by the project.
Highlights so far include the second version of the detailed requirements and specifications document for the microdisplays (and associated circuitry) and the tape-out of an initial design for the integrated circuit that includes new circuit designs developed within the project that are necessary to reach the required performance (speed, contrast, size). Soon to follow is a first draft of the design rule manual for the chips. The project has developed a new material and application process for a transparent hard protective coating (required e.g. during the steps to bend the display chips, but also generally useful to prevent damage before the final chip packaging), and the project has also made amorphous metal oxides (for future circuitry) by a new process that allows efficient selection of the best materials (this work has been published as \"\"Influence of the cation ration on optical and electrical properties of amorphous zinc-tin-oxide thin films grown by pulsed laser deposition\"\" in the journal ACS Combinatorial Science, 18(4) pp188-194 as an open access publication).
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