JP2005534505A - Method for producing a microsystem structure with lateral gaps and corresponding microsystem structure - Google Patents

Abstract

The present invention relates to a method for producing a microsystem structure with lateral gaps and a corresponding microsystem structure. The method of the present invention includes (a) depositing a first sacrificial layer (CS ₁ ) on a substrate (S) and (b) forming a movable add-on structure having two degrees of freedom (YY, XX). Forming a structural element (SE) or add-on structure on the sacrificial layer, and (c) a second sacrificial layer with a thickness e = d _g equal to the linear dimension of the lateral gap Coating the free surface of (SE) and (d) a layer of material (SM) adapted to form another add-on structure, a first sacrificial layer (CS ₁ ) and a second sacrificial layer Covering the free surface of (CS ₂ ), and (e) first and second degrees of freedom to form a lateral gap having a width essentially equal to the thickness of the sacrificial layer (CS ₂ ). Between the structural element (SE) in the direction of and any other add-on structure and substrate (S) The Rayuru contact to at least partially prevented, the second sacrificial layer (CS ₂₎ is etched in the subsequent first sacrificial layer (CS ₁₎ to the etching. The present invention is suitable for production of a microsystem structure and a device including the microsystem structure.

Description

  The present invention relates to a method for producing a microsystem structure with lateral gaps and a corresponding microsystem structure.

  The goal of current technology for using silicon micro-system structures with lateral gaps is that the mechanical features of the add-on structures on the substrate that make up the micro-system structures are the electromechanical functions of the devices incorporating such structures. Since it is critical in the definition of features, this mechanical feature is the most important construction of the silicon microsystem structure.

  This is especially true for the production of electromechanical resonators or filters that incorporate such microsystem structures.

  Two specific processes can be considered for the above-described techniques currently known that aim to produce high frequency resonant structures.

W. T.A. Hsu other by the title "A sub-micron capacitive gap process for multiple metal electrode lateral micromechanical resonators " ^{(Technical Digest, 14 th International IEEE} Electro Mechanical Systems Conference, Interlaken, Switzerland, Jan.22-25,2002, pp.340-352 ) Is based on a process for micromachining thin films. The gap is formed by oxidizing the polysilicon element. However, the formation of the electrode requires the use of gold electrodeposition. The minimum gap obtained by this process is currently 100 nm.

  The process, on the one hand, has the disadvantage of requiring a large number of mask overlays and complex technical steps, and on the other hand, the final structure is the smallest dimension limited by the molding process. This limits the shape of the structure that can be produced.

D. Galayko other by the title "High frequency hign-Q micromechanical resonator in thick epipolytechnology with post-process gap adjustment " ^{(Technical Digest, 15 th International IEEE} Micro Electro Mechanical Systems Conference, Las Vegas, USA, Jan.21-24,2002, pp The second process described in the .665-668) paper is based on the use of movement of the movable electrode impinged on the resonant beam after release of the movable structural element.

  The process described above allows gap values on the order of 0.2 μm to be realized.

  However, the minimum gap value remains dependent on the lateral accuracy of the structural layer lithography and etching. Therefore, it is difficult to realize a gap value of less than 0.2 μm.

  Furthermore, the process described above requires a specific architecture for the placement of the electrodes, and in particular requires additional connection pins and an additional voltage source.

  Finally, a third process for reducing the vertical gap is described in K.K. Wang et al., Titled “VHF free-free beam high-Q micromechanical resonator, Technical Digest, 12th International, 19th International Electron. 458). In the process described above, a resonator suspended from a flexible beam is attracted by a buried electrode in a direction perpendicular to the plane of the substrate and perpendicular to the substrate, and this electrode can also be used as a conversion electrode. Works. The corresponding gap can be reduced from 1.5 μm to 0.3 μm to 0.5 μm. The use of this process is limited to resonators with vertical gaps and excitation, and due to the use of buried electrodes, it is limited to thin film technology applications, otherwise excessively high voltages A level is required.

  Compared to conventional microelectronic technology, the above-described technology requires the use of structures with significantly thicker layers in order to obtain sufficient stability of the movable structure with respect to the assembly.

  Such a relatively large thickness systematically results in a minimum lateral dimension increase that is perpendicular to the thickness dimension used in connection with the method described above for the fabrication of microsystem structures.

  In particular, all of the processes used in connection with these technologies have a substantially constant form factor, and this form factor forms the smallest lateral dimension and its microsystem structure Defined as the ratio between the thickness of the add-on structure used.

  In most current applications of such microsystem structures, and in current applications that can be reasonably assumed in the medium term, movable add-on structures are used to create filters, resonators, etc. Operated by electrostatic conversion.

  Optimizing conversion efficiency and thus improving the performance of the micro-system structure used results in a movable add-on structure from one or more fixed or movable add-on structures in a direction substantially parallel to the substrate. Requires the narrowest possible side gap to isolate.

  Thus, there is a clear conflict between the need for thick add-on mechanical structures and the efficiency of electrostatic conversion.

  The object of the present invention is to solve the problems caused by the existence of the above-mentioned conflicts.

  Accordingly, the subject matter of the present invention is the use of a method of producing a microsystem structure having a lateral gap with a gap width that is substantially independent of the thickness of the layers comprising the add-on structure, and the production of the add-on structure. Is the use of process accuracy to etch the layers that make up that add-on structure.

  In particular, another subject of the present invention is the use of a method for producing a microsystem structure with an extremely small lateral gap due to the irrelevance described above.

  Another subject of the present invention is the use of a microsystem structure comprising an add-on structure on a substrate, further comprising at least one movable add-on structure, the lateral gap of which has a linear dimension of less than 0.1 μm Isolate the movable add-on structure from any add-on structure.

  The method to which the present invention relates to forming a lateral gap between add-on structures on the surface of a support substrate of a microsystem structure has two degrees of freedom with respect to the substrate, i.e. substantially perpendicular to the substrate. At least one movable add-on structure having a first degree of freedom in a direction and a second degree of freedom in a direction substantially parallel to the substrate and substantially parallel to the direction of the gap It can be used for the formation of add-on structures.

  This method deposits a first sacrificial layer of a predetermined thickness on the surface of the substrate and forms structural elements on the first sacrificial layer that constitute a movable add-on structure having two degrees of freedom. One of the faces of the structural element is in contact with the first sacrificial layer, and the free surface of the structural element is covered with a second sacrificial layer having a thickness substantially equal to the linear dimension of the lateral gap. Covering the free part of the first sacrificial layer and the free surface of the second sacrificial layer perpendicular to the direction of the gap with a layer of a specific material constituting at least one other add-on structure, A position below the structural element so that the structural element is at least partially free from any contact in each of the first and second degrees of freedom direction and in the direction of the gap with respect to In a position below a specific material layer, And etching the second sacrificial layer extending in the direction of the first degree of freedom, and then etching the first sacrificial layer extending in the direction of the first and second degrees of freedom by etching. It is worth noting in that respect. This allows the formation of a lateral gap having substantially the same thickness as the second sacrificial layer.

  The microsystem structure to which the present invention pertains includes an add-on structure on the substrate, one of which is a movable structure, which has two degrees of freedom with respect to the substrate, i.e. a direction substantially perpendicular to the substrate. And a second degree of freedom in a direction substantially parallel to the substrate. At least one of the other add-on structures is fixed and mechanically attached to the substrate.

  This microsystem structure is notable in that it comprises an intermediate layer that provides a mechanical connection between the substrate and the add-on structure, which is one of the add-on structures that make up the movable structure and the substrate. At least partially etched away in between and at least one lateral gap isolates the movable structure from one of the other add-on structures in the direction of the second degree of freedom. This lateral gap has a linear dimension of less than 0.1 μm in the direction of the second degree of freedom.

  The methods and microsystem structures to which the present invention pertains are in particular the microsystem industry and microsystem technology for the manufacture of electromechanical filters, resonators, or more generally electromechanical elements incorporating them. It is applicable to.

  The method and microsystem structure of the present invention will be better understood with reference to the following description and review of the accompanying drawings.

  In the following, a more detailed description of a method for forming lateral gaps between add-on structures on a substrate surface of a microsystem structure and the corresponding microsystem structure according to the present inventive subject matter is shown in FIG. This is done in association with the following figure.

  It will generally be recalled that the method to which the present invention pertains is aimed at forming lateral gaps between add-on structures on the surface of the support substrate. An “add-on structure” is any mechanical and formed on the substrate to constitute the microelectronic structure described above, such as a vibrating mass, electrodes, and / or walls fixed to the substrate. // means an electromechanical structure.

  These add-on structures comprise, for example, at least one movable add-on structure that forms a resonant part of a resonator or filter, which movable add-on structure has two degrees of freedom for the substrate. Referring to FIG. 1a, the movable structure described above has a first degree of freedom in a direction substantially perpendicular to the substrate, or more particularly in a direction perpendicular to the surface of the substrate to which the structure is added. And a second degree of freedom in a direction substantially parallel to the substrate, ie to the free surface of the substrate, and thus in a direction substantially parallel to the direction of the lateral gap. I can understand that FIG. 1a shows, at point a), the direction XX constituting the direction of the second degree of freedom and the direction YY constituting the direction of the first degree of freedom and perpendicular to the direction XX. Is seen from the front, so that its free surface is perpendicular to the plane of the drawing showing the drawing.

Referring to FIG. 1a above, at that point a), the method to which the present invention pertains deposits a _first sacrificial layer, designated CS ₁ of a predetermined thickness, on the surface of the substrate S. Or to form. In general, this substrate is a silicon substrate, but it should be pointed out that the method to which the present invention pertains is not limited to use on silicon substrates.

  Under these conditions, the first sacrificial layer can be constituted by a layer of silicon oxide formed by oxide growth, and this growth process is oriented in the second direction YY described above. Is represented by a vertical arrow.

Then, step a) can be followed by step b), which comprises an SE on the first sacrificial layer CS ₁ that constitutes, for example, a movable add-on structure with two degrees of freedom. Is to form the structural elements shown in FIG. One of the surfaces of this structural element SE is in contact with the _first sacrificial layer CS ₁ . The structural element SE is applied by depositing a specific layer of a predetermined material, such as polysilicon shown in dotted lines in FIG. May be formed in a conventional manner as illustrated in FIG. 1a by etching by masking.

  In general, step a) and step b) described above correspond to the implementation of steps that are conventional in the field of thin film technology or thick film technology processes, and are therefore detailed in these steps. Will not be explained.

The method to which the present invention pertains is that after step a) and step b) described above, in step c) the structural element SE is formed by a second sacrificial layer of a predetermined thickness, indicated by CS ₂ . In covering the free surface, this thickness is selected to be substantially equal to the linear dimension of the lateral gap to be formed.

  As a non-limiting example, when the structural element SE is formed, for example from polysilicon, step c) comprises both a free top surface of the structural element SE and, of course, a free lateral surface of the structural element SE. It should be pointed out that it is possible to do this by growing a layer of silicon oxide on the substrate.

Choosing the thickness of the sacrificial layer CS ₂ to match the gap value is shown by the equation e = d _g , where e represents the thickness of the oxide layer and d _g represents the value of the linear dimension of the gap in the direction XX of the second degree of freedom that is substantially parallel to the substrate S.

Step c) is followed by step d), in which the free part of the _first sacrificial layer CS ₁ and the free surface of the _second sacrificial layer CS ₂ perpendicular to the direction of the gap are described below. Coating with a layer of a specific material (indicated by SM) that constitutes at least one other add-on structure under the conditions to be achieved.

With reference to point d) in FIG. 1a, it should be pointed out that the above-described operation is actually in flattening the assembly. It is preferred that only the second sacrificial layer CS ₂ can be left free in its upper position without being covered with the specific material SM described above.

Step e) is followed by step e), which is in the direction of the second and first degrees of freedom in order to reach the first sacrificial layer CS ₁ by means of the freed gap, and of course It should be noted that the second sacrificial layer CS ₂ extending in a direction perpendicular to the plane of the drawing in which the drawing is shown is etched away, and then at a position below the structural element SE and of a layer of a specific material SM. In the lower position, the first sacrificial layer CS ₁ extending in the direction of the first and second degrees of freedom is eroded by etching. This operation is performed in each of the directions XX, YY of the first and second degrees of freedom, as shown in FIG. Allows the structural element SE to be at least partially released from any contact in the direction of the gap with respect to any adjacent add-on structure, and of course with respect to the substrate S.

Etching erosion on the first sacrificial layer CS ₁ on the one hand frees up space corresponding to the thickness of the sacrificial layer below the structural element SE and in particular below the layer of the particular material SM. It will be understood that this freed space is indicated by φ in FIG. 1a at point e).

Thus, the method to which the present invention pertains allows the formation of a lateral gap (denoted “gap”) whose width d _g is substantially equal to the thickness e of the second sacrificial layer. Will be understood.

The method to which the present invention relates is, in its notable aspect, that the thickness e of the second sacrificial layer CS ₂ depends on the selection of the parameters of the method for forming the second sacrificial layer and in particular its sacrificial It appears to be particularly effective because it can be adjusted directly by the choice of parameters of the oxidation process when the layer is formed by silicon oxide. The above parameters are not only related to the physical parameters of the oxidation of the polysilicon that constitutes the structural element SE described above, but are also required to form the resulting silicon oxide forming the _second sacrificial layer CS _2. Also related to time.

  It should be pointed out that under these conditions, the second sacrificial layer can be formed to have a predetermined thickness of less than 0.1 μm.

  Of course, the method to which the present invention pertains is shown in FIG. 1a in the most general case form.

However, from the point of view of industrial use of this method, step a) and step b) shown in FIG. 1a can be omitted, in which case steps c), d), e) is performed on the blank of the microsystem structure. The semi-processed state as shown in FIG. 1b is a substrate S covered with a _first sacrificial layer CS ₁ and a movable formed on the first sacrificial layer and having two degrees of freedom. And a structural element SE constituting the add-on structure. One surface of this structural element SE is in contact with the _first sacrificial layer CS ₁ .

  In particular, the above-mentioned semi-processed state can be produced on a large scale, and thus step c) shown in FIG. 1b corresponding to steps c), d), e) of FIG. 1a. It will be understood that by performing steps d) and e), it is possible to mass produce microsystem structures.

In general, it should be pointed out that the first sacrificial layer CS ₁ and the second sacrificial layer CS ₂ are made of substantially the same material. In particular, when the substrate S is a silicon substrate and the structural element SE is made of polysilicon, it is advantageous that the first and second sacrificial layers are composed of silicon oxide.

Under these conditions, the step of erosion by etching the second sacrificial layer CS ₂ and then the first sacrificial layer CS ₁ is performed substantially continuously, for example by isotropic etching. Only the conditions of this corrosion, i.e. the rate of corrosion and the conditions of the etching, can be adjusted, for example, depending on the specific specificity of the method.

Similarly, when the substrate S is composed of silicon, the operation of depositing or forming the first sacrificial layer CS ₁ on the substrate causes a predetermined thickness of the silicon oxide layer to grow by oxidation. It is particularly advantageous that this thickness is of the order of a few micrometers so as to constitute a freed area (indicated by φ) in point e) of FIG. Is possible.

  Finally, the specific material SM constituting at least one other add-on structure may be formed of various materials such as polysilicon, metal for constituting the electrode, silicon compound, epoxy resin and the like. In particular, the one or more add-on structures adjacent to the structural element SE constituting the movable structure may be fixed by themselves because they are separated from the structural element SE by the lateral gap described above, Or, in some cases, it may be movable.

  In the following, a detailed description of the industrial application of the method to which the present invention relates as shown in FIG. 1b will be given in connection with FIG.

  In FIG. 2, reference numerals for the same steps represent the same steps as those described above with reference to FIG. 1b or FIG. 1a, and the individual subscripts associated with the reference numerals for these steps are specific sub- Steps are shown.

  Thus, starting from a semi-machined state similar to that shown in FIG. 1b, the above-described method to which the present invention pertains performs a sequence of three steps c), d), e).

  However, several methods may be used, for example, to realize the intermediate structure shown in step d) of FIG. 1a or FIG. 1b. In particular, it will be recalled that the steps described above correspond to a process of depositing and planarizing the structure adjacent to the structural element SE, for example constituting a fixed electrode.

  Among the methods described above, mechanical chemical polishing, simple planarization with resin, or planarization with resin and selective corrosion can be taken up.

The last method described above consists in the thickness ep ₁ of the movable structural element SE and the thickness ep of the layer (indicated by SM ₁ ) forming other adjacent add-on structures which are fixed structures, for example electrodes. _The most common because it can be applied independently of ₂ .

  The sequence of steps for carrying out the method to which the present invention relates will now be described in connection with FIG. 2 in connection with the above method of resin flattening and selective corrosion.

With reference to the above-mentioned figures, a semi-machined state as described above in this description is considered, which half-machined state forms the structural element SE and is located above the first sacrificial layer CS _1. A first layer of structural material having a thickness e ₁ . Then, a structural element such as SE is defined by a first photolithography and etching operation. This definition takes place starting from a thick mask of silicon oxide that allows it to be stored later and to obtain a semi-processed state as shown in FIG. 1b or FIG. The semi-machined state is limited to the definition of a single structural element SE. A thick mask of silicon oxide is shown in OM and is superimposed on the structural element SE.

  Starting from the semi-processed state described above, step c) is carried out, for example, by the steps shown in FIG. 1b.

In the course of this step, the side surface of the structural element SE is oxidized to form a second sacrificial layer CS ₂ lateral thickness e = d _g of the second sacrificial layer CS ₂ is 2 Accurately define the desired nanometer gap value as shown at point c).

Then, as shown in FIG. 2, sub-step d ₁ ) so as to form a suitable coating for the assembly, in particular for the structural element SE and the second sacrificial layer CS _2. Step d) is performed by depositing a second structural layer of thickness ep ₂ at. This second structural layer is shown as SM ₁ . This operation is represented by step d ₁ ) in FIG. The assembly is then protected by depositing a sufficiently thick resin to form a protective layer so as to substantially cover the step height obtained in substep d ₁ ), this operation being performed in substep d _2. ) And corresponds to the operation of planarizing the second level structural material. The resin is represented as SM ₂ points d ₂₎ of FIG. In particular, it will be appreciated that sub-step d ₂ ) allows a first planarization in the sense that the step height is substantially reduced for the first time.

  The following steps substantially correspond to the etching and corrosion steps, step e) of FIG. 1b or FIG. 1a.

For that purpose, a thick resin protective layer is etched to form holes in the structural material SM ₁ only where the structural element, ie the structural element SE, is covered. Starting from a selective anisotropic etching process between the material SM ₁ and the protective layer SM ₂ , the second structural level SM ₁ is oxidized above the silicon oxide, ie the structural element SE It is planarized until it is flush with the thick silicon mask OM. The above-mentioned thick mask formed by silicon oxide serves as a means for indicating the end of the corrosion represented by point e ₂ ) in FIG.

The next sub-step e ₃₎ is followed by substep e _2), in the sub-step e _3), step e ₃₎ protective layer or material SM ₂ is removed in, the next, the material SM ₁ is The second step of photolithography by masking and etching is defined as add-on elements that form other add-on elements. The other add-on elements are shown in step e ₃ ) in FIG.

Subsequently, the structural element SE forming the movable element is a thick silicon oxide mask OM, a sacrificial layer CS ₂ and a subsequent sacrificial layer CS ₁ , as described above in connection with FIGS. 1b and 1a. And by a lateral gap in nanometers of width d _g relative to the adjacent structure acting as an electrode, for example as shown in sub-step e ₄ ) of FIG. It is isolated from other add-on elements by freeing the isolated movable structure or structure SE.

  The method to which the present invention relates therefore only uses the two masking levels mentioned above and lithographic means with a moderate resolution, ie with a resolution higher than 1 μm. Furthermore, in order to form a movable structure with a lateral gap in nanometers with self-aligning electrodes, it is not necessary to use very exact alignment and the alignment required is greater than 2 μm. . This is especially true in the case of the formation of a resonant beam activated by a side electrode.

  The method with which the present invention is concerned is of course applicable to any number of structural levels for other applications. Thus, this method allows the formation of lateral gaps with gap distances in the range of 10 nm to 1 μm for material thicknesses varying from 100 nm to 15 μm, regardless of the selected gap value.

  The method to which the present invention pertains enables industrial scale use and production of add-on structures on a substrate S that constitutes a microsystem structure as shown in FIG.

  This microsystem structure can be used to produce all types of microsystem elements, as will be described later in this description.

  Referring to FIG. 3, any of the microsystem structures according to the present inventive subject matter includes at least one add-on structure on the substrate S that constitutes a movable structure, ie, a structural element SE. You will remember that.

  This structural element has two degrees of freedom with respect to the substrate S in the directions XX and YY described above in this description.

At least one of the other add-on structures SM is fixed to the substrate S and mechanically attached. In a first noteworthy aspect of the microsystem structure to which the present invention pertains, this structure comprises an intermediate layer CS ₁ which realizes the mechanical connection between the substrate S and the add-on structures SE, SM, and this intermediate layer CS ₁ is at least partly between at least one of its add-on structures (particularly the structural element SE constituting the movable structure) and the substrate S, and possibly with one or the other of the movable structure SM. Etching is removed at least partially between the substrate S and the substrate S.

  Finally, in a particularly noteworthy manner, the microsystem structure to which the present invention pertains is at least one that isolates the movable structure, ie the structural element SE, from the other add-on structures in the second degree of freedom direction, ie the above-mentioned direction XX. Has a lateral gap.

FIG. 3 shows, in a non-limiting manner, two lateral gaps e ₁ = d _g and e ₂ = d _g , each of the lateral gaps in the second degree of freedom direction XX, 0. It has a linear dimension smaller than 1 μm.

The intermediate layer CS ₁ is a sacrificial layer having a predetermined thickness of 1 μm to 10 μm, for example. It will be recalled that the sacrificial layer is a layer that can be etched and etched, for example by chemical erosion.

  Two specific use cases of a microsystem starting from a microsystem structure according to the present inventive subject matter as shown in FIG. 3 will now be described in connection with FIGS.

  FIG. 4 shows an oscillating beam microresonator obtained by using a microsystem structure as shown in FIG.

  FIG. 4 shows that the oscillating beam has a reference VB and that its longitudinally symmetric plane is represented by the line indicated by pp ′ in FIG.

In a conventional manner, the vibration beam VB is clamped and fixed to the substrate by first and second fixtures indicated by ANC ₁ and ANC ₂ . Each of the first and second lateral gaps is between the lateral edge of the oscillating beam VB and the lateral edges of the first and second electrodes, indicated respectively by E ₁ and E _2. Is formed. Referring to FIG. 3, it will therefore be recalled that the lateral gap is indicated by e ₁ and e ₂ .

A microresonator with a limited oscillating beam as shown in FIG. 4 was used with the following dimensions:
Length = 30μm
Width = 2μm
Thickness = 2μm

  Next, another example of the use of a microresonator called a lame mode microresonator will be described with reference to FIG.

  Referring to the above figures, it can be seen that this lame mode microresonator has a microsystem structure as shown in FIG. 3 according to the inventive subject matter.

This microsystem structure is symmetric with respect to the center of symmetry indicated by C, which is embodied by the intersection of axes YY ′ perpendicular to the surface of the substrate S. The microsystem structure comprises a substantially square vibrating plate VP, the symmetry center C is located at the center of the plate, and the plate is fixed to the substrate S by an intermediate layer at each apex thereof. These fixing points are indicated by ANC ₁ , ANC ₂ , ANC ₃ , ANC ₄ .

As shown in FIG. 5, the lame mode microresonator is adjacent to one of the lateral edges of the vibrating plate VP and the lateral electrodes indicated by E ₁ , E ₂ , E ₃ , E _4. There are four lateral gaps, each formed between the edge and each associated with one of the side edges of the vibration plate VP. These lateral gaps are indicated by e ₁ , e ₂ , e ₃ , e ₄ .

  In the embodiment used with respect to FIG. 5, it can be seen that the vibrating plate VP has side edges or sides having a length of about 35 μm.

  In all cases, the value of the lateral gap described above is used regardless of whether a microresonator or lame mode microresonator with a limited oscillating beam as shown in FIGS. 4 and 5 is used. Was substantially equal to 80 nm.

  The method to which the present invention pertains allows the use of microsystem structures with a particularly high performance with lateral gaps significantly smaller than 1 μm and in particular significantly smaller than 0.1 μm.

  In general, any type of device can be used starting from the microsystem structure described above.

The method to which the present invention relates is considered to be particularly well suited for the production of microsystem structures starting from SOI type substrates, which is an abbreviation for Silicon On Insulator, The substrate is made of monocrystalline silicon, and the insulating oxide of SOI constitutes the first sacrificial layer CS ₁ .

  This application aimed at a positioning system with an accuracy in the range of a few nanometers, gripping an object in the nanometer range, a zero-bias resonator and an ultra-high frequency resonator called a nanoresonator.

Fig. 2 shows a schematic diagram for carrying out each successive step of the method to which the present invention pertains. Fig. 4 shows a schematic for implementing successive steps of a variant of the method to which the present invention is applied, wherein the basic steps are applied to a semi-processed state of a microelectronic structure, for example for use on an industrial scale. is there. Fig. 1b shows a detailed example of the implementation of the steps of the method forming the subject of the present invention in the variant shown in Fig. Ib. 1 shows a perspective view of a microsystem structure according to the present subject matter. Fig. 4 shows an overview of a microresonator having a lateral oscillating beam and incorporating a microsystem structure according to the present inventive subject matter as shown in Fig. 3; Fig. 4 shows an overview of a lame mode microresonator incorporating a microsystem structure according to the inventive subject matter shown in Fig. 3;

Claims (12)

A method of forming a lateral gap between add-on structures on a surface of a substrate, wherein the add-on structure has two degrees of freedom relative to the substrate, i.e., in a direction substantially perpendicular to the substrate. At least one movable add-on structure having one degree of freedom and a second degree of freedom in a direction that is substantially parallel to the substrate and substantially parallel to the direction of the gap. A method for forming a lateral gap, comprising:
a) depositing a first sacrificial layer of a predetermined thickness on the surface of the substrate;
b) A structural element constituting at least one movable add-on structure having two degrees of freedom, wherein one of its faces is in contact with the first sacrificial layer above the first sacrificial layer. Formed into
c) coating the free surface of the structural element with a second sacrificial layer having a predetermined thickness substantially equal to the linear dimension of the lateral gap;
d) a layer of a specific material that constitutes at least one other add-on structure with the free portion of the first sacrificial layer and the free surface of the second sacrificial layer perpendicular to the direction of the gap. Coated with
e) With respect to the at least one other add-on structure and the substrate, the structural element is at least partially free from any contact in each of the first and second degrees of freedom direction and in the direction of the gap. The second sacrificial layer extending in the direction of the second and first degrees of freedom is etched away at a position below the structural element and below the layer of the specific material by etching. The first sacrificial layer extending in the direction of the first and second degrees of freedom is eroded by etching, which has a width substantially equal to the thickness of the second sacrificial layer. Allowing gaps to be formed,
A method characterized by that.   The method according to claim 1, wherein the steps c), d), and e) are continuously performed on a half-processed state of a microsystem structure, and the half-processed state is the first processed state. The structural element comprising a substrate coated with a sacrificial layer and formed on the first sacrificial layer and adapted to constitute the at least one movable add-on structure has two degrees of freedom. And wherein one of the surfaces of the structural element is in contact with the sacrificial layer.   The method according to claim 1 or 2, characterized in that the second sacrificial layer has a thickness of less than 0.1 m.   The method according to any one of claims 1 to 3, wherein the first and second sacrificial layers are made of the same material.   In the case of a substrate composed of silicon, the step of depositing the first sacrificial layer on the substrate is characterized in that a layer of silicon oxide of a predetermined thickness is grown by oxidation. Item 5. The method according to any one of Items 1 to 4.   In the case of a structural element constituting the movable add-on structure made of a material belonging to the group formed by silicon, polysilicon, or silicon compound, the second sacrificial layer having a predetermined thickness 6. The operation of coating a free surface of a structural element, characterized in that a layer of silicon oxide having a thickness substantially equal to the width of the lateral gap is grown by oxidation. The method according to item.   The method of claim 6, wherein the thickness of the silicon oxide layer is adjusted according to a growth time of the silicon oxide layer.   The specific material constituting at least one other add-on structure is constituted by a material belonging to a group formed by polysilicon, metal, silicon compound, epoxy resin, or the like. The method according to any one of 7 above. A micro-system structure comprising an add-on structure on a substrate, wherein one of the add-on structures, i.e. the movable structure, has two degrees of freedom relative to the substrate, i.e. in a direction substantially perpendicular to the substrate. One degree of freedom and a second degree of freedom in a direction substantially parallel to the substrate, at least one of the other add-on structures being fixed and mechanically attached to the substrate. A microsystem structure,
An intermediate layer providing a mechanical connection between the substrate and the add-on structure, and is at least partially etched and removed between at least one of the add-on structures constituting the movable structure and the substrate; A middle layer,
At least one lateral gap that isolates the movable structure from the other add-on structure in the direction of the second degree of freedom, wherein the linear dimension is less than 0.1 μm in the direction of the second degree of freedom. Having lateral gaps,
A microsystem structure characterized by comprising:   The structure of claim 9, wherein the intermediate layer is a sacrificial layer having a predetermined thickness of 1 μm to 10 μm.   A microresonator having an oscillating beam, comprising the microsystem structure according to claim 9 or 10, wherein the microsystem structure has a symmetry with respect to a longitudinal symmetry plane of the oscillating beam, and A microresonator having first and second side gaps each formed between a side edge and each of side edges of first and second electrodes. A lame-mode microresonator, comprising the microsystem structure according to claim 9 or 10, wherein the microsystem structure is symmetric about a center of symmetry;
A substantially square vibrating plate located about the center of symmetry and secured to the substrate at the apex by the intermediate layer;
Four each formed between one of the side edges of the vibration plate and an adjacent edge of a side electrode associated with one of the side edges of the vibration plate A lame-mode microresonator comprising a side gap.

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