Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
  • B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
  • B81C1/00436—Shaping materials, i.e. techniques for structuring the substrate or the layers on the substrate
  • B81C1/00555—Achieving a desired geometry, i.e. controlling etch rates, anisotropy or selectivity
  • B81C1/00611—Processes for the planarisation of structures
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
  • B81C2201/00—Manufacture or treatment of microstructural devices or systems
  • B81C2201/01—Manufacture or treatment of microstructural devices or systems in or on a substrate
  • B81C2201/0101—Shaping material; Structuring the bulk substrate or layers on the substrate; Film patterning
  • B81C2201/0102—Surface micromachining
  • B81C2201/0105—Sacrificial layer
  • B81C2201/0108—Sacrificial polymer, ashing of organics
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
  • B81C2201/00—Manufacture or treatment of microstructural devices or systems
  • B81C2201/01—Manufacture or treatment of microstructural devices or systems in or on a substrate
  • B81C2201/0101—Shaping material; Structuring the bulk substrate or layers on the substrate; Film patterning
  • B81C2201/0118—Processes for the planarization of structures
  • B81C2201/0125—Blanket removal, e.g. polishing
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/01—Chemical elements
  • H01L2924/01082—Lead [Pb]

Definitions

• the invention relates to a method for producing an integrated microsystem-type component, comprising a planar suspended micro-structure, using a sacrificial layer of polymer material deposited on a substrate and having side walls delimiting the planar suspended structure, method comprising successively a planarization step, a step of depositing a formation layer of the suspended structure, a step of etching at least one opening of the formation layer up to the level of the front face of the sacrificial layer and a step dry etching of the sacrificial layer.
• MEMS micro electro-mechanical Systems
• planar suspended micro-structures This is for example the case of actuators, sensors, switches, variable capacitors, inductances (self) or acoustic wave resonators of suspended volume.
• suspended micro-structures are produced by the use of a sacrificial layer.
• the conventional steps for obtaining a suspended microstructure are shown, in simplified form, in FIGS. 1 to 5.
• a layer 2a is deposited on a substrate 1.
• the layer 2a is typically made of polymer material, silicon oxide or tungsten.
• the second step shown in Figure 2, consists of lithographing and engraving the layer 2a so as to form a layer sacrificial 2 covering part of the substrate 1 on which the suspended structure must be formed.
• a layer 3 for forming the suspended structure is deposited on the substrate 1 and on the sacrificial layer 2.
• the layer 3 for formation can be conductive or dielectric or constituted by a stack of several different layers.
• the fourth step, represented in FIG. 4 consists in lithographing and etching the formation layer 3 up to the level of the front face of the sacrificial layer, so as to delimit the suspended structure 5 by openings 4 in the layer 3 of training.
• the sacrificial layer is removed by dry etching or wet etching, so as to constitute a free space between the substrate and the suspended structure 5, thus freeing the suspended structure.
• the material constituting the sacrificial layer is chosen so that its etching is selective with respect to the material for making the microstructure.
• the sacrificial layer can be made of silicon oxide (Si0 2 ) and the suspended structure can be made of polysilicon.
• a second combination comprises a sacrificial layer of polymer material and a suspended structure of Si0 2 .
• a third possibility is to use a sacrificial layer of polymer material and a suspended metal structure.
• the outline of the suspended structure 5, in a plane perpendicular to FIG. 5, is perfectly defined during the lithography step.
• its profile in the plane of FIG. 5 depends on the lower layers, and in particular on the sacrificial layer, on which the suspended structure is built.
• the profile is very often strongly accentuated by the creep of the material during annealing.
• the exact profile of the suspended structure affects system control. Indeed, undulations of the microstructure, brought about by the shape of the sacrificial layer, make it difficult to know the stiffness of the final device and its deformation as a function of the excitation conditions.
• the space between the suspended structure and the substrate is also influenced by the profile.
• the embedding of the micro-structure depends on the inclination of the suspended structure, which also depends on the profile. Lack of knowledge of the exact profile leads to a large gap between simulations and experimental measurements of the device and to the risk of stress concentrations at the embedding and on the mobile structure. Above all, this makes the devices extremely sensitive to process variations.
• CMP chemical mechanical polishing
• the object of the invention is to remedy these drawbacks and, more particularly, to produce planar suspended structures using a planarized polymer sacrificial layer.
• this object is achieved by the fact that, between the deposition of the sacrificial layer and the planarization step, a step of deposition, on at least part of the substrate and of the front face of the sacrificial layer, an embedding layer, having a thickness greater than the thickness of the sacrificial layer, so that, after the planarization step, the front faces of the sacrificial layer and the layer of embedding form a common flat surface, the formation layer of the suspended structure being deposited on the front face of the common flat surface.
• the planarization step successively comprises a sub-step of chemical mechanical polishing of the underlayment layer, and a sub-step of etching of the underlayment layer so that the faces before the sacrificial layer and the embedding layer form a common planar surface.
• the side walls of the sacrificial layer are delimited by etching by means of a mask formed on the front face of a layer of polymer material by deposition, lithography and etching of a temporary layer, the deposition of the embedding layer being carried out on the assembly constituted by the sacrificial layer and the mask, the mask being eliminated during the planarization step.
• the component comprising elements projecting from the substrate comprises, before the deposition of the sacrificial layer, successively a deposition on at least one area of the substrate, intended to be covered by the layer sacrificial and comprising projecting elements, of a base layer, having a thickness greater than the thickness of the projecting elements, and an additional planarization step, by chemical mechanical polishing, of the base layer, so as to that the front faces of the base layer and the projecting elements form a common flat surface.
• the two faces of the formation layer of the suspended structure are completely flat.
• Figures 1 to 5 show a method, according to the prior art, of a component comprising a suspended structure.
• Figures 6 to 1 1 show different steps of a particular embodiment of a method according to the invention.
• Figures 12 to 14 show steps of another particular embodiment of a method according to the invention.
• Figures 15 to 19 show steps of a third particular embodiment of a method according to the invention.
• Figures 20 to 23 show steps of a fourth particular embodiment of a method according to the invention.
• FIG. 6 represents a sacrificial layer 2 arranged on a substrate 1.
• the side walls 10 of the sacrificial layer 2 have been delimited by lithography and etching, as in FIG. 2.
• the planar suspended structure intended to be formed on the sacrificial layer 2 is delimited by the side walls 10 of the sacrificial layer 2.
• FIG. 7 represents a step of depositing, on at least a portion of the substrate and of the front face of the sacrificial layer 2, of an embedding layer 6, having a thickness greater than the thickness of the sacrificial layer. Typically the thickness of the embedding layer 6 is 1.7 times greater than the thickness of the sacrificial layer 2.
• the embedding layer 6 must be arranged so as to envelop the sacrificial layer 2 and to block lateral movement. of the sacrificial layer 2.
• the embedding layer 6 can completely cover and surround the sacrificial layer 2. It can also cover only a limited band of the sacrificial layer 2 and extend, at the ends of this band, over the zones adjacent to the substrate 1, on either side of the sacrificial layer 2.
• the material of the embedding layer 6 must be a material allowing the use of planarization process, in particular of CMP type, for example Si0 2 , silicon nitride or aluminum. As shown in the figure
• a planarization step of the assembly of the embedding layer 6 and of the sacrificial layer 2 is carried out so that the front faces of the sacrificial layer 2 and of the embedding layer 6 form a flat surface common.
• the planarization stage must be stopped as soon as the front face of the sacrificial layer 2 is completely discovered.
• the thickness fluctuations of the sacrificial layer 2 are leveled and the sacrificial layer 2 and the embedding layer 6 form a common flat surface. Continuation of the planarization step beyond this limit increases the risk of deteriorating the quality of the surface of the sacrificial layer 2 and of deteriorating the flatness.
• FIG. 9 represents a step of depositing a planar layer 3 for forming the structure suspended on the front face of the common planar surface of the sacrificial layer 2 and the embedding layer 6.
• the deposition of the formation layer 3 is done on a single plane.
• a fourth step, represented in FIG. 10, consists in etching at least one opening 4 in the formation layer 3 up to the level of the front face of the sacrificial layer 2.
• the dry etching of the sacrificial layer 2 is carried out.
• the planar formation layer 3 then forms the planar suspended structure 5.
• a component produced by the method according to the invention comprises a layer 3 for forming the suspended structure 5 having two flat faces, the front face and the rear face arranged on the embedding layer 6.
• the planarization step may include a chemical mechanical polishing (CMP) and, in particular, consist only of a chemical mechanical polishing.
• CMP chemical mechanical polishing
• a CMP type process consists, in known manner, of holding the object to be planarized against a rotary polishing plate wet in a polishing bath, containing abrasives and an acid or basic solution.
• Abrasives are typically particles based on aluminum or silicon.
• the layer intended to be planarized is chemically modified by the liquid and then removed by the particles of the abrasive.
• the application of a type CMP directly to the sacrificial layer 2 risks damaging the sacrificial layer 2, even in the presence of an embedding layer 6, in particular by encrustation of abrasive residues.
• the initially deposited embedding layer 6 has a thickness approximately 1.7 times greater than the thickness of the sacrificial layer 2 (FIG. 12) and the planarization step includes a mechanical-chemical polishing sub-step. , making it possible to obtain a flat surface of the embedding layer 6 (FIG. 13), and a sub-step of etching the embedding layer 6 uncovering the sacrificial layer 2 so that the front faces of the layer sacrificial 2 and the embedding layer 6 form a common flat surface ( Figure 14).
• the initial etching of the sacrificial layer 2 is carried out by means of a mask 7 previously formed on the front face of the sacrificial layer 2 by deposition, lithography and etching of a temporary layer ( Figure 15).
• the temporary layer can be of dielectric or metallic material (for example chrome, aluminum, etc.).
• the typical thickness of the temporary layer is between 10 and 50 nanometers.
• the mask 7 makes it possible to delimit the side walls 10 of the sacrificial layer 2.
• the deposition of the embedding layer 6 is then carried out on the assembly constituted by the sacrificial layer 2 and the mask 7
• a first planarization sub-step can be carried out by a CMP type process, without risk of deterioration of the sacrificial layer 2, because the sacrificial layer 2 is protected by the mask 7 (FIG. 18).
• a second planarization sub-step consists in eliminating the mask 7, preferably by dry or wet etching, as shown in FIG. 19. Then the process for producing the suspended structure can be continued by the steps shown in Figures 9 to 11 , described above.
• the method for producing the suspended structure may include additional steps before the deposition of the sacrificial layer 2.
• a base layer 9 is deposited on the substrate 1 and on the protruding elements 8 so as to completely fill the areas arranged between the protruding elements 8.
• the base layer 9 has a thickness greater than 1 thickness of the projecting elements (typically 1.7 times greater).
• the next step is planarization by chemical mechanical polishing of the base layer 9, so that the front faces of the base layer 9 and of the projecting elements 8 form a common flat surface (FIG. 22), serve as a substrate for the deposition of the sacrificial layer 2 (FIG. 23). If there is a risk that the protruding elements 8 are damaged during the planarization step, a CPM type planarization is followed by etching up to the level of the front face of the protruding elements 8.
• the process is suitable for any type of polymer of the sacrificial layer (photosensitive resin, polyimide, PMMA, etc.) and independent of any treatment of the polymer of the sacrificial layer (polymer highly or slightly annealed or even not annealed, annealed under UV, having undergone ion implantation, etc.).
• the process makes it possible to produce any geometry of the sacrificial layer (narrow, wide, thick, thin, rectangular, round shape, etc.). There is no risk of scratches on the sacrificial layer and the substrate nor of risks tearing of the sacrificial layer during the planarization step, the sacrificial layer at no time exceeding the embedding layer.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Geometry (AREA)
• Manufacturing & Machinery (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Micromachines (AREA)
• Treatments Of Macromolecular Shaped Articles (AREA)

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• 2002
  • 2002-12-18 FR FR0216088A patent/FR2849016B1/fr not_active Expired - Fee Related
• 2003
  • 2003-12-18 WO PCT/FR2003/003789 patent/WO2004056698A2/fr not_active Application Discontinuation
  • 2003-12-18 AU AU2003299341A patent/AU2003299341A1/en not_active Abandoned
  • 2003-12-18 EP EP03799623A patent/EP1572578A2/de not_active Withdrawn

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