Emmanuelle Vigier-Blanc

Improved tolerancing for production yield anticipation of optical micro-modules for cameraphones

Tolerancing an optical design is vital when optical modules are produced in tens of millions. In these cases the production yield is all-important: it will decide if the product will be a success. While optical design softwares provide powerful tolerancing tools, to get an idea of what the production yield will be, we will have to go a step further. A way of taking this step consists in a tolerancing procedure that will use these tolerancing tools and a dedicated analysis software: - A list of specifications that the lenses will have to fit into has to be established. - A merit function that will calculate each of these specs will have to be written. - For the tolerancing itself, a script will have to be used to write to an output file all these values for each lens created during tolerancing - The analysis software will read the output file, make all the desired statistics and then give the production yield and other relevant informations (e.g. yield and behavior of any spec)

Ultra low cost wafer level via filling and interconnection using conductive polymer

Devices for consumers like camera phones are essentially driven by the cost and performances. In that scope, several new key technologies are requested to achieve a complete active waferlevel camera (with autofocus or zoom). A low cost vias interconnection has to be developed and conductive polymer is an attractive solution to overcome this challenge. In this paper we describe new technology to fill insulated vias and perform interconnection with conductive polymer with screen printing equipment. In the first part, process flow compatible with waferlevel camera integration is presented to make vias and metal routing. Then, polymer characterizations were done to evaluate Dupont CB100 resistivity and contact resistance with our metallization. Electrical contacts have been demonstrated with values about 100mQ and proflow configuration. Thermal cycling between −40°C to +85°C was performed successfully and no variation was observed even after 300 cycles. These results are very promising and give us a first feedback on this technology ability to withstand classical consumer product environmental tests.

Optics for mobile phone imaging

Micro cameras for mobile phones require specific opto electronic designs using high-resolution micro technologies for compromising optical, electronical and mechanical requirements. The purpose of this conference is to present the optical critical parameters for imaging optics embedded into mobile phones. We will overview the optics critical parameters involved into micro optical cameras, as seen from user point of view, and their interdependence and relative influence onto optical performances of the product, as: -Focal length, field of view and array size. -Lens speed and depth of field: what is hidden behind lens speed, how to compromise small aperture, production tolerances, sensitivity, good resolution in corners and great depth of field -Relative illumination, this smooth fall off of intensity toward edge of array -Resolution; how to measure it, the interaction of pixel size, small dimensions -Sensitivity, insuring same sensitivity as human being under both twilight and midday sunny conditions. -Mischievous effects, as flare, glare, ghost effects and how to avoid them -How to match sensor spectrum and photopic eye curve: IR filter, and color balancing. We will compromise above parameters and see how to match with market needs and productivity insurance.

Process optimization and performance analysis of an electrostatically actuated varifocal liquid lens

A new type of varifocal liquid lens actuated by electrostatic parallel plates is presented and the main technological steps involved in the fabrication process are discussed. The influences of the membrane material, the electrode size and the optical diameter on the optical performance of the lens are characterized using wave-front measurements giving basic design rules for the device performance optimization. Optical powers of 13m−1 at 20V and 11m−1 at 13V are measured on lenses with optical diameters of 3mm and 1.5mm respectively. When placed ahead of a 3Mp camera module, the variable-focus liquid lens permits to focus on the different parts of a scene by changing the applied voltage.

Enabling technologies for advanced wafer level camera integration

In this work, innovative solutions for the full manufacturing of a camera module at the wafer scale (the wafer level camera) are presented and discussed. In order to replace the glass carrier currently used in image sensors connected with TSV (Through Silicon Via), three different integration schemes (temporary bonding, cavities etched first and cavities etched last) are proposed for the introduction of a silicon carrier with structured cavities opened over the image sensor pixel area. Excellent electrical results are demonstrated for the three solutions and the advantages and limitations of each integration scheme are discussed. In a second part a benchmarking of different materials to be used as spacers between the image sensor wafer and the optics wafers is conducted. The geometrical parameters: thickness, Total Thickness Variation (TTV) and bow of silicon, glass or epoxy wafers are compared as received and after grinding to simulate a specific focal length target. The capability to structure the three materials was also tested: laser or etching for silicon, laser for epoxy and double side sandblasting for glass. Finally an innovative solution with a direct structured spacer epoxy molding on glass is presented. In the last part, perspectives are given on the integration of a wafer level variable focal lens. Associated to emerging solutions for wafer-level auto-focus, the potential of low cost polymer via filling through the optical stack is discussed.