Wafer Level Optics - Introduction and Solutions Available for Wafer Level Optics by EV Group

Topics Covered

Overview
Wafer Level Cameras (WLCs)
Master Stamp Fabrication
UV Microlens Molding
Aligned UV Bonding

Overview

In modern electronic devices such as digital cameras, mobile phones, portable gaming consoles, laptops or netbooks, micro-optical systems are decisive interfaces between the real world and the microelectronics of the image sensor inside a camera module. At present, the general concept of a camera module assembly undergoes a transition from discrete assembly to wafer-level integration using well-established semiconductor technologies. Wafer-level cameras have already started to replace conventional modules due to smaller form factors and lower cost performance ratios.

Wafer Level Cameras (WLCs)

Wafer level cameras (WLCs) are devices in which all the individual parts are fabricated at wafer level and are then bonded to form one single part consisting of a CMOS image sensor (CIS) and a micro-optics stack enhancing the light capture efficiency of the camera.

UV imprint lithography, originally developed for cost-efficient replication of structures in the nanometer range, is now considered a powerful tool for the fabrication of wafer-level optics in highly parallel mass fabrication processes.

EV Group offers manufacturers a complete range of solutions, including master stamp fabrication, replication and integration of optical elements at wafer level based on its well-established mask alignment and nanoimprint lithography systems. Its product portfolio is highly versatile, enabling customers to implement highly customized hardware and software processes. Coupled with process development and optimization in EV Group's cleanroom facilities, EV Group provides a total solution from system configuration and fabrication to process integration and material know-how.

Elements of a typical wafer-level camera module include a CMOS image sensor, polymeric lenses molded onto glass carriers by UV imprint lithography, spacers and aperture layers, as shown in this exploded view.
Source: EVG.

Master Stamp Fabrication

Master stamps are wafer-size templates fully populated with microlens molds each replicated from one single lens template in a step-and-repeat (S&R) approach. Starting out from a single lens master made out of metal or glass, EV Group offers a process flow which covers all essential process steps for the fabrication of master stamps featuring unmatched lens position accuracies of <100nm and high lens shape repeatabilities required for the fabrication of high-end wafer level camera modules.

Individual S&R process steps featured by EV Group:

  • High precision positioning of single lens template across the wafer
  • Droplet dispense of master stamp material
  • Wedge compensated force or distance controlled high-precision first imprint
  • UV exposure
  • Demolding

Please see our related product EVG®770 Gen II NILStepper for detailed information.

UV Microlens Molding

Soft UV Imprint Lithography is a highly parallel technique for the fabrication of polymeric microlenses, the key elements of wafer level optical systems. Starting out from soft working stamps replicated from wafer-size master stamps, EV Group offers hybrid and monolithic microlens molding processes which can be easily adapted to various material combinations for working stamp and microlens materials. In addition, EV Group offers a qualified microlens molding process including all relevant material know-how.

Soft UV Imprint Lithography Setup for single and double side lens molding.
Source: EVG.

Individual UV Molding process steps featured by EV Group:

  • Puddle dispense of optical pre-polymer
  • Wedge compensated force or distance controlled aligned imprint
  • UV exposure
  • Demolding

Please see our related product IQ Aligner® for detailed information.

Single side 300mm lens wafer fabricated by Soft UV Imprint Lithography.
Source: EVG.

Aligned UV Bonding

The ultimate micro optics stack is fabricated by UV bonding of all elements, including individual double side microlens wafers as well as spacer wafers required to achieve the final stack height. Crucial parameters are lens-to-spacer alignment accuracy, total thickness variation of the resulting bond interface and wafer throughput.

UV bonded micro optics stack consisting of lens wafers and spacer wafers.
Source: EVG.

Individual process steps featured by EV Group:

  • Wedge compensated aligned UV bond
  • UV exposure

Individual lens and spacer wafers of a micro optics stack prior to UV bonding.
Source EVG, Courtesy of Aptina.

Please see our related product IQ Aligner® and our Gemini® for detailed information.

Source: EV Group

For more information on this source please visit EV Group

Date Added: Jan 17, 2011 | Updated: Jun 11, 2013
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