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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.