LT5208B - A method for manufacturing of microelectromechanical switch - Google Patents

Abstract

Invention relates to a class of microelectromechanical systems (MEMS), to be more precise to the manufacturing technology of microelectromechanical switches. Seeking to increase reliability and durability of microelectromechanical switches, fabrication method of microelectromechanical switch starts from formation of microstructures in the support area (7) of microcantilever structure (5) by patterning and etching, using a combination of wet and reactive ion etching processes, a layer of deposited aluminium. Further, source (2), gate (3) and drain (4) electrodes are formed on the substrate (1) by deposition of chrome under layer by electron - beam evaporation and subsequent resistive evaporation of gold layer a top of the chrome layer, following pattering of the electrodes using lift - off lithography. Next, electron - beam evaporation is used to deposit a sacrificial copper layer over the whole area of the substrate (1). Then pattering of the copper is partially etched to define thecontact tips (6)

Description

The invention relates to a class of microelectromechanical systems (MEMS), in particular to the manufacture of microelectromechanical switches.

There is a known method of manufacturing a microelectromechanical switch, in which the clamp is electrochemically formed from multilayer metal films (see U.S. Patent No. 6016092, HOI P 1/10, 2000).

A known method of manufacturing microelectromechanical switches is to form a sacrificial polyimide layer on a semi-insulating gallium arsenide substrate, above which low temperature (T = 250 ⁰ C) plasma, activated by chemical vapor deposition, forms a silica clad that is obtained by etching and evaporating the appropriate portion of the sacrificial polyimide layer beneath it. The remainder serves as a boom support (see U.S. Patent No. 5,578,876, HOI P 1/10, 1996).

The method of manufacturing microelectromechanical switches described above, like the analogue, has certain disadvantages. Its manufacturing process involves many technological steps, very complex manufacturing processes, the material used to form the bracket is insufficiently resistant, and the bracket is unstable due to the small contact area of the bracket, which reduces the reliability and durability of the product.

The object of the invention is to increase reliability and durability.

This object is achieved by the fact that the manufacturing method of the microelectromechanical switch, in which the electrodes are formed on a heavy-duty semiconductor substrate, is covered by a sacrificial layer, which is covered by a mechanically resistant material from which the bracket is formed by etching the sacrificial layer. According to the invention, by direct photolithography, the brackets form fractal microstructures in the support area, where they electronically vaporize the aluminum layer, deposit the mask thereon. confluence electrodes, where the substrate is deposited with a photoresist to form a pattern of electrodes and to form a chromium plating on the entire photoresist layer by vacuum electron beam deposition, which is deposited on the substrate with an organic solvent, electron beam vaporization of the sacrificial copper layer, where it performs partial copper etching to form the contact tip ends and the beam support areas e performs direct photolithography on a deep copper etching process and exposes the gold contact layer, followed by reverse photolithography to form a bracket, whereby electron beam vacuum evaporation forms a gold layer on which the electrochemical nickel coating is deposited and the deposited copper layer finally deposited.

The invention is explained in Figure 1, which is a schematic diagram of a microelectromechanical switch.

The microelectromechanical switch consists of electrodes for the tray 1, the outlet 2, the gate 3 and the junction 4, and the bracket 5, which at its free end has contact tips 6 and which is attached to the tray through a support 7 having fractal microstructures. The microelectromechanical switch is controlled by applying a voltage between the gate 3 and the bracket 5, thereby generating an electrostatic force that draws the bracket 5 to the junction electrode 4 and thereby closes the circuit. When the voltage is removed, the elastic forces of the bracket 5 return it to its original position, thereby disconnecting the circuit.

The method of manufacturing the microelectromechanical switch is implemented as follows.

The semiconductor substrate 1 is cleaned chemically in organic solvents and in a plasma of a mixture of oxygen and nitrogen gas. By direct photolithography, fractal microstructures are formed on the semiconductor substrate 1 and the support region 7 of the support 5. To do this, the sacrificial layer of 100 nm aluminum is electronically vaporized on the semiconductor substrate 1. Aluminum-etched (etching-Cr ₂ O3: NH4F: H2O) mask to obtain fractal microstructures. By combining liquid isotropic and dry anisotropic (reactive ionic) etching (with several modifications of the etching method), fractal microstructures of a large effective surface area are formed in the form of stepped pyramids. Liquid isotropic etching on a silicon substrate 1 is performed using a Sirtl etcher (HF: HNO3: C2H4O2) and anisotropic etching is performed on high-frequency plasma of SF6 / N2 reactive gas. The fractal microstructures thus formed significantly improve the adhesion of the bracket 5 and the substrate 1. Further, the aluminum layer is removed from the pickle and the substrate is chemically cleaned again in organic solvents and in the oxygen / nitrogen gas plasma. Then, by reverse photolithography, the electrodes of the source 2, the gate 3, and the junction 4 are formed on the conductive substrate. To do this, a photoresist is applied to the substrate and a drawing of the electrode 2, the gate 3 and the junction 4 is formed on the substrate. The electron beam vacuum evaporation method produces a 30 nm thick chromium coating. A chromium plating is applied to a 200 nm thick gold layer by vacuum thermoresistive evaporation. The layers of metal which have evaporated on the photoresist are 'decomposed' by boiling in an organic solvent (dimethylformamide). The sacrificial layer of 3000 nm copper is electron beam vaporized on the entire surface of the substrate. By direct photolithografting, the copper in the sacrificial layer is partially etched to form the contact tip 6. Next, deep copper etching (H2SO4: CrO3: H2O etcher) is performed on the sacrificial layer by direct photolithography, in the support area 7 of the bracket 5, exposing the contact gold layer. Then, a reversible photolithography clamp 5 is formed to do this by vacuum electron beam evaporation to form a 200 nm gold layer in the clamp region 5. Then, a drawing of the bracket 5 is formed in a photoresist with the same photographic template and a 3000 nm electrochemical nickel coating is grown on a conductive gold surface. The electrode contact is provided through a mechanically exposed copper layer at the edges of the substrate 1 which covers the entire surface and has a contact with a gold layer in the clamp forming region. The following modes of nickel electrochemical deposition are used to form the cladding: cathodic current density jk = 5 A / dm ² , T = 45-60 ° C, sulfamate electrolyte Ni-NH 2 SO 2: 4H 2 O, pH = 3.6-4.2. Finally, the sacrificial layer (etching H2SO4: CrCh: H2O) is etched.

Multiple studies have shown that the use of a mechanically resistant material (nickel instead of silica) to form the bracket significantly increases the durability of the switch compared to the prototype, while the fractal microstructures in the support area reliability and durability.

Claims (1)

Definition of the Invention A method of manufacturing a microelectromechanical switch, wherein electrodes are formed on a heavy-duty semiconductor substrate by depositing a sacrificial layer, which is covered by a mechanically resistive material that forms the bracket, whereby the sacrificial layer is formed by fractal, electron vaporizing the aluminum layer, etching the mask, alternating liquid isotropic and dry anisotropic etching several times, and finally etching the aluminum layer, followed by reverse photolithography to form the source, barrier and confluence electrodes, where it provides a photoresist on the substrate Electron Beam Vacuum Evaporation of the Photoresist Layer Creates a Gold Plated Chrome Coating and Vacuum Evaporation on the Photoresist Layer removes metal layers in organic solvent, then electron beam vaporises the entire surface of the substrate! ^var i ⁰ layer, which performs a partial copper paėsdinimą contact arms viršūnėlėms form and bracket abutment region direct photolithography method performs a deep copper etching opened and the contact of gold layer, followed by reverse photolithography method forms a bracket, wherein the vacuum evaporation electron beam method consists of a gold layer, on which the electrochemical coating of nickel is grown and the final deposited copper layer is deposited. 1 ap, fig.