Samsung Developing MEMS Shutter for Mobile Cameras

May 15, 2009
Tsuneyuki Miyake, Nikkei Microdevices
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Samsung Electronics Co Ltd is currently developing a MEMS shutter intended for compact digital cameras. It is formed on a glass substrate using a typical MEMS technology and has already been reported at an academic conference.

The shutter is circular and 2.2mm in diameter. It is made by repeatedly forming a film on a glass substrate. Specifically, the ITO (indium tin oxide), a transparent electrode material, is formed on the glass substrate, and a light shield film is formed on it.

This light shield film is composed of 36 pieces of fan-shaped films that have an angle of 10°, and they are arranged to form the shape of a circle. Each of the 36 fan-shaped films is attached to the ITO film on its circumference, with its center portion curled downward. Under this condition, the light shield film is "open" and does not block light.

When the ITO film and the light shield film are applied with a voltage of 30V, an electrostatic force is generated on the films, and the light shield film covers the entire surface of the ITO film. Under this condition, the light shield film is "closed" and blocks the light.

The light shield film is curled because it is composed of two thin films, for example, an Al thin film and a SiN thin film. The two materials have different internal stresses, and, therefore, the desired curling angle can be achieved by adjusting their thicknesses and controlling the internal stress of each thin film.

In respect to the achievement, the person who made the presentation at the conference said that Samsung Electronics cannot reveal any more details other than those mentioned at the conference at least until the end of 2009 and did not mention the possibility of commercializing this technology.

It is sometimes possible to eliminate the need for a shutter used in a digital camera by quickly transferring image data captured by an image sensor (for example, in less than 10μs). However, in the case of a sensor with a high pixel count such as 10 Mpixels, the time to transfer one frame becomes long due to the image data transfer speed. And it is impossible to capture fast-moving objects without distorting their images.

This is the reason why high-end cameras need a function that physically blocks the light. However, a mechanical shutter is too large and expensive to be used in a compact camera that is built in a mobile phone. The company intends to solve the issues of the size and the cost by using a MEMS shutter.

This is why high-end cameras need a function that physically blocks the light. However, a mechanical shutter is too large and expensive to be used in a compact camera built in a mobile phone. Samsung Electronics intends to solve the issues of the size and the cost by realizing a MEMS shutter.