EV Group's wafer-level microlens molding process extends manufacturing roadmap for CMOS image sensors

SEMICON JAPAN 2010; CHIBA, JAPAN: EV Group (EVG), a leading supplier of wafer bonding and lithography equipment for the MEMS, nanotechnology and semiconductor markets, has developed a new micro-lens molding process that can enable volume production of very-high-resolution (up to eight megapixels and higher) wafer-level optics for use in smart phones, pico projectors and myriad other applications.

The new, Monolithic Lens Molding (MLM) capability, which was developed in-house by EVG's process development team, is available as an option on the company's IQ Aligner UV nanoimprint lithography (UV-NIL) system or can be upgraded to existing equipment. EVG expects to ship its first IQ Aligner with the MLM option in the first half of 2011.

As the size of the camera in mobile phones can be a limiting factor in mobile handset designs, there is an increasing demand for smaller camera modules that can still address the call for higher resolution and cost effectiveness. This has shifted manufacturing of both the CMOS image sensor and the micro-optics stack to the wafer level. At the same time, the evolution of wafer-level cameras toward higher pixel counts to meet higher performance standards is driving the need for more complex optical systems and, consequently, tighter manufacturing tolerances.

In wafer-level camera production today, glass substrates are typically used as carrier and spacer wafers for the lenses, which are composed of an optical polymer material. The different material characteristics of these components limit resolution and picture quality, which hinder the scalability and quality of the camera modules. EVG's MLM process overcomes this limitation by eliminating the need for glass substrates. Instead, the polymer is molded between two stamps and then cured with UV exposure by the EVG's IQ Aligner system.

By omitting the glass substrates, wafer-level optics manufacturers face fewer constraints on the optic and lens stack design—enabling the production of thinner lens wafers and significantly shorter optical stacks. In addition, since the IQ Aligner molds the micro-lenses using a room-temperature UV-NIL process versus thermal imprinting, a high degree of precision alignment is achieved between the various elements in the optical lens stack—maximizing device performance.