PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS

**Definition:** This place covers:

B81C deals with manufacturing methods of microstructures as defined in the definition statement of B81B .

Subject-matter belonging to B81C

Documents which contain one of the following characteristics should be classified in B81C :

A solution to a technical problem which is common to microstructures in general (e.g. avoiding stiction, hermetic encapsulation, fabricating structures with high aspect ratio)

A process / structure which is not specific to a given application (e.g. process for making a membrane, torsion beam not specific to a given optical switch, packages for MEMS devices, machines specific to MEMS manufacturing, stamps for making microstructure).

Examples:

documents that deal with processes that solve a general problem but mention as an example a specific application should nevertheless be classified in B81C since the invention could also be applied to other applications

Subject-matter excluded from B81C

B81C doesn't cover applications which describe processes for manufacturing pure biological or chemical material (DNA sensors, carbon nanotubes ...)

Processes for solving a problem which is specific to a kind of device like increasing the sensitivity of a pressure sensor

**Glossary:** - Extending structures: Pillar / ColumnTip - Depressed structures: Cavity GrooveHole - Stiction: Unintended adhesion of a moving part to another part - Suspended structures: Bridge Cantilever Diaphragm See-saw Comb structure - Extending structures: AnchorRib - Depressed structures: ChannelNozzle - Suspended structures: Flexure Membrane Spring Torsion hingeProof mass - Rotating elements: Gears Rack and pinionHinge - Pillar/Column B81B2203/0361: A tall vertical structure, usually narrow in proportion to its height, which is usually used as a support structure, anti-adhesion structure or a structure for thermal exchange. - Tip: Tips are small pointed or rounded structures often used for Scanning Probe Microscopy probes (SPM) - like atomic force microscope (AFM), but also for data storage (Millipede), electron tunnelling tip (used in sensors) or microneedles. - Bump: It is a raised structure similar to a tip. It is generally used to describe the raised structures used for avoiding stiction of movable parts. It is also used in relation to structures for reducing adhesion. - Functional layers: Functional layers are used mostly as protective coatings. They can protect structures against chemical or mechanical corrosion that can release particles into the protected cavity. Special coatings are used also to prevent adhesion of movable structures or to reduce the stress. Metallic layers covering polymer sealing are used to make them hermetic, but can be used also to compensate the RF-interferences. - Anchor B81B2203/0307: Anchors are structures connecting the suspended movable parts to the substrate. They can affect the resonant frequency and the reliability of the device. - Rib: Stiffening ribs are may be used to improve the stiffness of suspended structures. Improving the stiffness to mass ratio, they can have impact on resonant frequency and efficiency of the devices. - Cavity B81B2203/0315: In bulk micromachining, cavity is used to make the movement of a suspended element possible. It can be used also for the protection of movable structures in packaging, for thermal insulation or as a container for fluids (see Figure 1). The synonyms are chamber, hollow, well. - Groove B81B2203/0346: A typical example is a V-Groove (see Figure 1), which can be formed in 100 - Si substrate by KOH etching. Sometimes the groove in 111 - Si substrate is called channel or trench to distinguish them, but we consider channel to be a function oriented definition. Grooves are usually used in microfluidic applications, but can also be used for precise positioning of optical fibres or controlled weakening of structures holding a device prior to its separation by breaking. - Hole B81B2203/0353: An aperture passing through anything, a perforation, opening. - Channel B81B2203/0338: A tube or tubular passage, natural or artificial, usually for liquids or fluids. - Nozzle: A spout, mouthpiece, projecting aperture, or a short terminal pipe from which a jet of gas or liquid may issue or be discharged (see Figure 1). - Bridge B81B2203/0109: A bridge is a structure, erected or suspended over a surface, depression or an obstruction, connecting two or more extremities, including structures with supports deformable in torsion (see Figure 4), flexion or supported by springs (see Figure 5 ). - Cantilever B81B2203/0118: A cantilever is a structure which projects beyond a supporting column on a wall and is counterbalanced and/or supported at only one end. Cantilevers are also called flexures, suspension or cantilever beams and suspension springs if their structure is more complicated. These elements usually store and release mechanical energy by deformation resulting in vibration. A proof mass can be attached to one extremity of a cantilever. If there is a cantilever on both sides of a supported structure (proof mass or a micromirror), this structure is called a bridge. - Diaphragm B81B2203/0127: A diaphragm is a layer covering a hole or a cavity, fixed to a frame all along its periphery, separating two environments. This separation can be hermetic or not, permanent or temporal and its opening can be controllable. Diaphragms can be perforated or have a seismic mass attached to it. - See-saw B81B2203/0181: See-saw structures are suspended structures supported by a flexible element which main axis is usually perpendicular to the substrate plane. These structures can be used as a support for micromirrors, switches, gyroscopes and resonators. - Comb structure, comb drive B81B2203/0136 , B81B2201/033: A comb is a structure with a pair of comb-shaped electrodes. This shape increases the total capacitor surface. Comb structures are used for actuation or sensing. When voltage is applied, the combs are attracted to each-other. They are often attached to a deformable element that pulls them back to the initial position because they can not develop a repulsive force. - Flexure: Flexure or a flexure beam is a structural element that carries load primarily in bending. Deformation comprises bending about an axis normal to the beam's axis. This allows the structures to move along the perpendicular axis to the substrate (see Figure 6). - Membrane B81B2203/0127: A membrane is a thin layer separating two environments allowing selective mass transport control, like chemical or physical filtering or separation of substances. Membrane is often used as synonym to diaphragm. - Spring: Spring is a suitably shaped structure that can return to its original shape after a deformation (see Figure 5). - Torsion hinge: Torsion hinge also called deformation hinge or a torsion beam is an element that deforms by twisting about an axis parallel to the beam's axis. This allows the structures to rotate around the axis parallel to the substrate (see Figure 4). - Proof mass: Proof mass also called seismic mass is a structural element usually connected to a deformable element. The mass of this element defines the resonant frequency, sensitivity and precision of the system. In some cases, holes or grooves are made on the proof mass to control or eliminate damping (see Figure 6). - Gears B81B2201/035: A gear is a toothed wheel designed to transmit torque to another gear or toothed component. - Rack and pinion: Structure used to transform rotation to translation movement. - Hinge: The movable joint or mechanism to provide for the turning of two movable parts. - Interconnects B81B2207/07: Electrically conducting element for transmitting a signal from one point to another one. Interconnects that may be formed on, in or through the substrate or any element formed on the substrate (e.g. lid of a package). A via is a particular form of an interconnect. - Electrodes B81B2203/04: Electrically conducting element through which an electric current enters or leaves a substance (or a vacuum) whose electrical characteristics are being measured, used, or manipulated. Also terminal points in electrical components. - Thermal actuators B81B2201/031: The movement is generated by the difference in thermal expansion of two of more elements (generally beams), each elements having at least one anchoring point to the substrate. A typical thermal actuator is formed out of two parallel beams (one cold beam and one thermal beam) attached at one end to the substrate and having one connecting point at the other end. When the temperature of the thermal beam becomes higher than the temperature of the cold beam, the difference of thermal expansion generates a deflection at the connecting point. H01H . - Bimorph and unimorph actuators B81B2201/032: A bimorph is a cantilever that consists of two active layers. These layers produce a displacement via: Thermal activation (a temperature change causes one layer to expand more than the other). Electrical activation as in a piezoelectric bimorph (electric field(s) cause one layer to extend and the other layer to contract). A piezoelectric unimorph has one active (i.e. piezoelectric) layer and one inactive (i.e. non-piezoelectric) layer. For example in the following figure, in response to application of a voltage to the first movable electrode 25, the second movable electrode 26, and the third movable electrode 27, the piezoelectric thin film 1 extends/contracts and the movable section 23 is driven toward the substrate 21.