Agency for Science, Technology and Research

Institute of Microelectronics

Other

National University of Singapore

Janak Singh

Yu Jau Chen

Quanbo Zou

Ajay Agarwal

Chih Kiong Terence Gan

Xiaolin Zhang

Uppili Sridhar

Ranganathan Nagarajan

Tie Yan

Tit Meng Lim

Chirayarikathuveedu Sankarapillai Premachandran

Chew Kiat Heng

Pamidighantam Venkata Ramana

Colin James Richard Sheppard

Joseph Suresh Paul

A microprobe that is capable of using an incident and reflected radiation ray for three-dimensional (3-D) bio-imaging. The microprobe comprises a hollow body closed at one end and having an aperture at an opposite end, at least one 3-D free space micromirror, at least one focusing lens, and a beam director or a beam coupler or other kind of device for beam coupling or splitting. The beam director is arranged at the aperture end of the hollow body and is adapted to direct the incident ray into the hollow body via the aperture. Within said hollow body is the at least one focusing lens and the at least one micromirror arranged respectively from the aperture, such that the distance between the focusing lens and the micromirror allows for the incident light ray to be directed onto the micromirror.

Microprobe for 3D bio-imaging, method for fabricating the same and use thereof

In a 3D free space micromirror device, a mirror plate is joined with actuators through flexible springs where the other ends of the actuators have fixed support on the substrate. Single crystal silicon and aluminum are used as bi-morph materials with silicon dioxide providing electrical isolation between the two. Thickness variation in the microstructure is achieved by two-step p-n junction formed in a p-type substrate. Thick and thin n-silicon layer formation and DRIE cut mechanisms are employed in such a way that all the thick and thin silicon components of the structure are released simultaneously avoiding overetch which can be detrimental to the thin flexural springs. Working prototypes of the device have been found suitable for any optical switching array architecture where deflections up to 10 degrees are required.

Single-crystal-silicon 3D micromirror

First and second n-doped regions are formed at a surface of a p-doped single crystal silicon substrate. An aluminum layer is patterned overlying some of the second n-doped regions to form thermal actuators. A dielectric layer is deposited overlying the patterned aluminum layer and an underlying thermal oxide layer. A metal layer is deposited thereover and patterned to form bond pads to the thermal actuators and to form reflecting mirror surfaces overlying others of the second n-doped regions to form micromirrors. The substrate is etched away from the backside stopping at the first and second n-doped regions. Then the wafer is diced into mirror array chips. Portions of the first n-doped regions are etched away from the frontside to form flexible springs wherein the second n-doped regions covered by the patterned aluminum layer form thermal actuators and wherein the flexible springs connect the micromirrors to the thermal actuators.

Method of making a single-crystal-silicon 3D micromirror

Method of fabricating a micro-mirror switching device in single crystal silicon are described. The device is fabricated as three main elements: silicon mirror plate with metal-mirror, secondary actuator, and hinge/spring mechanism to integrate the mirror plate with the actuator. p-n junction is first formed on p-type silicon. Trenches are then etched in n-silicon to define the device element boundaries and filled with silicon dioxide. Three layers of sacrificial oxide and two structural poly-silicon layers are deposited and patterned to form device elements. Novel release processes, consisting of backside electrochemical etching in potassium-hydroxide, reactive ion etching to expose oxide-filled trenches from the bottom, and hydrofluoric acid etching of sacrificial oxide layers and oxide in silicon trenches, form the silicon blocks; those that are not attached to structural poly-silicon are sacrificed and those that are attached are left in place to hold together the switching device elements.

Method of fabricating micro-mirror switching device

A process to form a capillary that is well insulated from its environment is described. Said process has two stages. The first stage, which is the same for both of the invention's two embodiments, comprises forming a micro-channel in the surface of a sheet of glassy material. For the first embodiment, this sheet is bonded to a layer of oxide, that lies on the surface of a sheet of silicon, thereby sealing in the capillary. After all silicon has been selectively removed, a thin membrane of oxide remains. Using a low temperature bonding process, a second sheet of glassy material is then bonded to this membrane. In the second embodiment, the silicon is not fully removed. Instead, the oxide layer of the first embodiment is replaced by an oxide/nitride/oxide trilayer which provides improved electrical insulation between the capillary and the remaining silicon at a lower level of inter-layer stress.

Capillary with glass internal surface

Formation of micro-fluidic systems is normally achieved using a multi-wafer fabrication procedure. The present invention teaches how a complete micro-fluidic system can be implemented on a single chip. The invention uses only dry etch processes to form micro-chambers. In particular, it makes use of deep reactive ion etching whereby multiple trenches of differing depths may be formed simultaneously. Buried micro-chambers are formed by isotropically increasing trench widths using an etchant that does not attack the mask so the trenches grow wider beneath the surface until they merge. Deposition of a dielectric layer over the trenches allows some trenches to be sealed and some to be left open. Micro-pumps are formed by including in the micro-chamber roof a layer that is used to change chamber volume either through electrostatically induced motion or through thermal mismatch as a result of its being heated.

Process to fabricate an integrated micro-fluidic system on a single wafer

Growing community of inventors

Singapore, Singapore

Janak Singh