Method of making elastic elements of monocrystalline silicon

 

Usage: in the technology of semiconductor devices. The inventive method of manufacturing elastic elements integral transducers of monocrystalline silicon provides for the operation of anisotropic etching of monocrystalline silicon plate with subsequent isotropic duralluminium. Anisotropic etching is carried out with simultaneous extraction of the plate from the solution. The technical result of the invention is to improve the reproducibility of the geometric dimensions of the elastic elements due to compensation of the clinoid shape of the profile of the source plate. 2 Il.

The invention relates to the technology of instrument making.

As an analogue of the selected method of manufacturing elastic elements of monocrystalline silicon by RF patent 2059321, H 01 L 21/306, 1996

Method of making elastic elements (beams, membranes, strings) integral transducers of the wafer of monocrystalline silicon with a plane orientation (100) includes the steps of oxidation of the plate, covering it with a protective layer of photoresist, one-sided photolithography, opening the Windows in the oxide film in the places of formation elastic elements film, re-oxidation, deposition of a protective layer of photoresist, one-sided photolithography on the side opposite to the doping, opening the Windows in the oxide film in places the formation of elastic elements on the width, the greater the required width of the elastic element, the anisotropic etching to the doped layer.

Anisotropic etching until doped layer for symmetric elastic suspensions is carried out in two stages, the first stage of the anisotropic etching is performed on a depth equal to half the thickness of the silicon wafer, and then additionally hold the drawing on the plate of the protective layer of photoresist, one-sided photolithography on the side opposite to the doping, and opening Windows in the oxide film in the formation of elastic elements at a certain width, then spend the second stage of the anisotropic etching to the doped layer.

The disadvantages of the known solutions: cumbersome process, it is impossible the formation of a symmetric suspensions with fillet profiles only anisotropic etching, elastic elements, is made on the basis of the doped layer, have a relay transfer characteristic due to changes in physico-mechanical characteristics metallicheskih silicon by Japan patent 59-25393, H 01 L 29/84, 1984

Method of making elastic elements of monocrystalline silicon, containing operations oxidation wafer of monocrystalline silicon with the orientation of the underlying surface in the plane (100), applying a protective layer of photoresist, photolithography, opening the Windows in the oxide film in the formation of elastic elements at a certain width, taking into account the anisotropic etching of monocrystalline silicon, an anisotropic etching to a depth less than that needed to obtain the required thickness of the elastic element, and isotropic otravlenia until you get the desired thickness of the elastic element with simultaneous formation of a fillet transitions.

A disadvantage of the known solutions: low reproducibility of the geometric dimensions of the elastic elements (30% of the total number of elements on a wafer of monocrystalline silicon) due to the scatter of the thickness of the original plate, in particular of the clinoid shape of the profile.

This disadvantage is eliminated by the proposed solution.

Task - improving method of manufacturing elastic elements of monocrystalline silicon.

The technical result - improving the reproducibility of the geometrician and the clinoid shape of the profile of the source plate.

This technical result is achieved in that in the method of manufacturing elastic elements of monocrystalline silicon, containing operations oxidation flat plate with the orientation of the underlying surface in the plane (100), applying a protective layer of photoresist, photolithography, opening the Windows in the oxide film in the formation of elastic elements at a certain width, taking into account the anisotropic etching of monocrystalline silicon, an anisotropic etching to a depth less than that needed to obtain the required thickness of the elastic element, and isotropic otravlenia until you get the desired thickness of the elastic element with simultaneous formation of a fillet transitions, plate with a certain amount of the clinoid shape profile for anisotropic etching to a depth less than that needed to obtain the required thickness of the elastic element, hung so that the minimum thickness was in the upper part of the etching solution, with subsequent simultaneous extraction plates of the provide the Etchant speedwhere V is the speed of extraction of inserts provide the Etchant solution; d is the diameter of the original silicon wafer; TTrsettlement time is th the thickness of the plate.

In Fig. 1 is a diagram of an installation for implementing the method of manufacturing elastic elements of monocrystalline silicon. In Fig.2 - source procurement (silicon wafer).

Installation scheme for anisotropic etching of elastic elements of monocrystalline silicon is shown in the drawing: it contains a bath 1 with solution provide the Etchant 2, the bracket 3 with the silicon wafer 4.

Method of making elastic elements of the monocrystalline silicon is the following. When receiving a batch of semiconductor silicon wafers carry out the measurement of the thickness of the plate. Tolerances on thickness are1...2% of the nominal thickness of the plate.

Based on the data obtained by measurements produce the sorting plate thickness. Measured plates are grouped in a party with limits of deviation from the nominal value of 0-10 μm. Sorting by clinoid shape of the profile plates should be in the range of 0 to 1 μm. Taking into account the tolerance on parallelism receive up to 5 groups of plates with the same thickness, but with deviations from parallelism of 1 μm, 2 μm to 6 μm. For each of the obtained groups in the region with a minimum thickness of plates is carried out to estimate the time tmin- minimum plate thickness; R100the etching rate in the direction (100); hpack- the required thickness of the elastic element.

The etching time TTrtaking into account deviations from parallelism is defined by the following expression:where hPLmin- minimum thickness of the plate.

Selected plates oxidize, put a protective layer of photoresist, carry out a photolithography followed by opening Windows in the oxide film at a certain width, taking into account the anisotropy of the etching. Then the plate was hung so that the minimum thickness was in the upper part of the solution.

Then, completely immerse the plate in a bath 1 to provide the Etchant and conduct anisotropic etching to a depth less than that needed to obtain the desired thickness of the elastic elements, allowing time equal to T0Tr. Further, the bracket raises 3 plates of provide the Etchant with the speed defined in the formula (1). Then spend isotropic otravlenie until you get the desired thickness of the elastic element with simultaneous formation of a fillet transitions.

An example of the method.

In the manufacture of elastic elements with a thickness of 20 μm from the plate is the minimum etching time was 6 hours at a speed of etching of 60 μm/hour. Then the plate was removed from the solution provide the Etchant with the speed of 1.27 mm/sec. If the wedge plate is 6 μm, the rate of extraction plates will be 0.25 mm/sec. As a result of the etching, the thickness of the elastic suspensions will be the same all across the plate and will be 20 microns.

The reproducibility of the geometric dimensions of the elastic elements of monocrystalline silicon, made by the proposed method is 48.7 per cent of the total number of elastic elements on the plate, i.e., increased 1.6 times in comparison with the prototype.

Claims

Method of making elastic elements of monocrystalline silicon by oxidation flat round plate with the orientation of the underlying surface in the plane (100), applying a protective layer of photoresist, photolithography, opening the Windows in the oxide layer in the formation of elastic elements at a certain width, taking into account the anisotropic etching of monocrystalline silicon, an anisotropic etching to a depth that is less than necessary to obtain the desired thickness of the elastic elements, isotropic otravlenia until you get the desired thickness of the elastic elements with the simultaneous formation of a fillet perehodia deep less than is necessary to obtain the required thickness of the elastic element, hung so that the minimum thickness is in the upper part of the etching solution, with subsequent simultaneous extraction of their speedswhere V is the velocity of the extraction plates of the solution provide the Etchant;
d is the diameter of the original silicon wafer;
TTr- estimated time of etching with a maximum thickness of plates;
T0Tr- estimated time of etching with a minimum thickness of plate.

 

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