Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
  • B81B3/00—Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes
• • 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
  • B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
  • B81C1/00134—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems comprising flexible or deformable structures
  • B81C1/00158—Diaphragms, membranes
• • 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
  • B81C1/00444—Surface micromachining, i.e. structuring layers on the substrate
  • B81C1/00468—Releasing structures
  • B81C1/00476—Releasing structures removing a sacrificial layer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
  • B81B2201/00—Specific applications of microelectromechanical systems
  • B81B2201/02—Sensors
  • B81B2201/0264—Pressure sensors
• • 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
  • B81C2201/0109—Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• • 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
  • B81C2201/05—Temporary protection of devices or parts of the devices during manufacturing
  • B81C2201/053—Depositing a protective layers

Definitions

• the invention is based on a method for producing a micromechanical membrane sensor or a micromechanical device produced by this method
• micromechanical sensor elements In order to detect various physical variables (pressure, temperature, air mass, acceleration, rate of rotation), components with micromechanical sensor elements are often used, in particular in the motor vehicle sector. Typically, measuring elements are often used on membranes, which are arranged above a cavern.
• membranes which are arranged above a cavern.
• so-called surface micromechanics in which layer stacks of sacrificial and functional layers are deposited, structured and selectively removed, so-called bulk or volume micromechanics are known, in which structures made of solid material are machined.
• DE 102 00 40 433 56 A1 describes how a buried cavern is generated by means of a single trench etching process.
• the trench etching process has a first trench etching step, which produces a depression.
• the etching step is performed in two phases. Alternately, in a first phase, a recess is first produced, the walls of which are covered in the second phase with a passivating agent. By repetition of the two phases thus the depression is generated.
• the cavern is then generated in the second trench etching step, the depression serving as an access hole to the cavern. This is achieved in that in the second trenching step, the etching process of the first phase is carried out significantly longer without a passivation taking place. By repeating the steps of this trench etch process, multiple underlying caverns can be created in the substrate.
• Substrate initially applied different layers By means of a masking metal layer depressions are introduced into the applied layer sequence.
• the introduction of the depression is carried out by means of an anisotropic dry etching process.
• a subsequent isotropic etching process for example by plasma etching, interconnected cavities in the substrate are produced starting from the depressions underneath the applied layers.
• a recess can be produced in the substrate from the rear side of the substrate.
• the two cavities can finally be connected to one another.
• the present invention describes a method for producing a micromechanical membrane sensor or a micromechanical device produced by the method
• the micromechanical membrane sensor has at least a first membrane and a second membrane lying substantially above the first membrane. Furthermore, it is provided that the micromechanical membrane sensor has a first cavity and a substantially over the first Having cavity lying second cavity.
• a first protective layer is first produced on the substrate. In this first protective layer, at least one opening is produced, which extends through the entire first protective layer to the substrate. On the first protective layer, a first membrane layer is then applied and patterned. This first membrane layer is at least partially provided with a second protective layer. In the second protective layer also at least one opening is produced, which extends to the first membrane layer.
• a sacrificial layer is then applied, which is at least partially covered by a third protective layer.
• a second membrane layer is applied, wherein it is provided in particular that the second membrane layer is arranged above the sacrificial layer.
• the second membrane layer at least one opening is introduced, which extends through the second membrane layer and the third protective layer to the sacrificial layer.
• the advantage of the invention is that the release of the membranes or the production of a double membrane in a surface micromechanical process can be generated by means of a single etching step from the wafer or substrate front side.
• the geometries which influence the functional parameters of the membrane sensors are each determined individually in preliminary processes and are not changed by the release. Since the wafer or the substrate is processed in a surface micromechanical process only from the front, a wafer handling on standardized systems is possible. In this case, damage to the fragile micromechanical structures is less likely than with volume micromechanical processes in which the wafers are handled and processed on both sides, since it is not necessary to encompass the wafer or reorient the processes onto the structures produced.
• the first cavity is produced in the substrate below the openings in the first protective layer.
• the second cavity which is produced by the dissolution of the sacrificial layer, is located between the first and the second membrane (layer).
• the first membrane of the proposed membrane sensor is essentially formed by the first membrane layer and the second membrane essentially by the second membrane layer.
• the two membranes have additional layers, for example in the form of protective layers.
• the second and the third protective layer are structured in such a way that they surround the sacrificial layer in the region of the second cavity.
• the first and second protective layer surrounds the first membrane, and thus define its lateral and vertical extent.
• the substrate is a semiconductor material, in particular silicon, and / or at least one of the protective layers is an oxide, in particular a thermal oxide and / or the first membrane layer silicon, and / or the sacrificial layer silicon or silicon germanium and / or the second membrane layer has a metal layer.
• the first and / or second membrane layer is produced by a CVD method.
• at least one of the two membrane layers is produced by an LPCVD deposition.
• the membrane layer which is arranged on top of the layer stack, can consist of a plurality of layers.
• the membrane layer is provided with an additional passivation layer against environmental influences.
• the structuring of the first and / or the second membrane layer takes place by means of a trench process.
• the etching process can be carried out by means of a fluorine-containing compound, for example a fluorine-containing plasma (SF 6 , NF 3 ) or preferably by spontaneously etching gases such as ClF 3 or XeF 2 .
• a fluorine-containing compound for example a fluorine-containing plasma (SF 6 , NF 3 ) or preferably by spontaneously etching gases such as ClF 3 or XeF 2 .
• the thickness of the second protective layer is greater than half the diameter of the openings in the first membrane layer.
• the lateral and vertical extent of the first cavity in the substrate is advantageously defined over the etching time of the one etching step.
• Another possible process step is to close the openings through the second membrane layer and the third protective layer by the application of another layer, so that the cavity, which was created by these openings, is completed.
• the buried first membrane is electrically contacted. It is envisaged that for generating the electrical
• the second protective layer Contacting in the second protective layer is an opening to the first membrane layer is generated.
• the sacrificial layer After the sacrificial layer has been applied, it is patterned in such a way that an electrically insulated region, which can later be electrically contacted, is produced in the sacrificial layer.
• the third protective layer is applied, which largely encloses the electrically insulated region in the sacrificial layer.
• a recess is provided in the third protective layer, which extends to the electrically insulated region in the sacrificial layer.
• an electrically conductive spatially limited layer is applied for contacting the insulated region in the sacrificial layer or for contacting the first membrane to the third protective layer in the region of the recess. This can be done, for example, in the form of bonding
• this conductive spatially limited layer has no electrical connection to the second membrane layer.
• a micromechanical membrane sensor By producing two superimposed release membranes, a micromechanical membrane sensor can be produced in which both membranes can be deflected independently of one another.
• the first and the second cavity are interconnected. This can take place, for example, through an opening in the first membrane.
• the manufacturing tolerances in particular the geometry parameters of the membrane structure, can be improved.
• the design substantially reduces the handling and processing effort and thus lowers the production costs.
• Special back side processing which is usually an integral part of volume micromechanical processes, is associated with dead areas for machine handling (eg Pinlift) and loss of yield due to damage to the front.
• a processing of the wafer back side or a processing with breakthroughs through the wafer may require the use of a complex carrier technique in which the wafer is mounted on a carrier (wafer, foil, chuck) and with this carrier must be processed.
• a carrier wafer, foil, chuck
• the manufacturing tolerances and manufacturing safety play a major role in the layer structure of the sensors. So usually the processes for demonstrators are simplified waiving the
• the release of two membranes can be achieved by two time etching processes in which one of the time etching processes is performed from the wafer front side and the other from the wafer back side. Since both processes show variations with respect to the etching rate and, in addition, differences are produced by the wafer handling, component tolerances due to wafer handling can not be ruled out.
• a controlled series production with high yield can be represented, since a complicated wafer handling of the type described is not required and the release of the two membranes is achieved by only one single etching step.
• the effects of process variations can be decoupled from the functional parameters of the membrane sensor.
• FIGS. 1 a to 1 g schematically show the production method of the membrane sensor with a double membrane.
• Figure 2 shows the structure of the finished membrane sensor.
• the functional layers are the lower membrane, the sacrificial layer between the membranes and the upper membrane.
• intermediate layers are necessary which separate the functional elements from each other.
• the first membrane and the sacrificial layer are preferably made of silicon, since at least parts of both layers are removed during sacrificial layer etching in order to expose the membranes.
• materials such as SiGe can be used, which can be removed during sacrificial layer etching.
• the upper i. second membrane may be made of different materials, including silicon.
• a preferred choice is a low tension membrane, e.g. an ONO structure
• FIGS. 1a to 1g A possible manufacturing method of the micromechanical membrane sensor according to the invention is to be illustrated schematically with reference to FIGS. 1a to 1g.
• the layer structure of the membrane sensor is carried out by applying various layers to the front side 105 of the silicon substrate wafer 100.
• the surface of the silicon substrate wafer 100 is passed through
• the oxide can be produced, for example, by means of thermal oxidation.
• this first protective layer 110 one or more through openings 120 may be provided, which may be used for the subsequent production of the first cavity.
• a first membrane layer 130 is applied to the first protective layer 110 or into the openings 120, as shown in FIG. 1b.
• This first membrane layer 130 will later form the lower membrane 400.
• the application of this first membrane layer 130 takes place by means of epitaxial methods or by means of LPCVD Deposition of silicon.
• the layer thickness of the first membrane layer 130 is determined by the process parameters during the layer deposition.
• the first membrane layer 130 is structured, for example by a trench etching process. The result is a perforation of the membrane that defines regions 140 that can be removed during sacrificial layer etching. These regions are separated from the actual membrane layer 400 by the trench etching trenches 145.
• a further protective layer 150 is applied (see Figure Id).
• the trench trenches 145 are also completely filled. This can be done by a thermal oxidation, wherein the layer thickness of the second protective layer 150 and the oxide thickness should be greater than half the trench width of the trenches, which can thus be completely filled (see 155 in Figure Id).
• the oxide layer 150 can also be patterned. In this case, in the region of the first membrane 400
• Through holes 160 are generated.
• the sacrificial layer 170 is deposited and patterned on the second protective layer 150.
• the process steps can be carried out analogously to the deposition and structuring of the lower membrane layer 130.
• a region for the second cavity 310 can be defined.
• a region 200 may be provided within the sacrificial layer 170 for the electrical contacting of the lower membrane 400.
• a further protective layer or oxide layer 180 closes the sacrificial layer 170 and at the same time limits the sacrificial layer etching in the lateral direction through the trench trenches 175 filled with the oxide of the oxide layer 180, so that only a defined region is undercut, the membrane rigidity being defined in the layout or in the layer structure , Through holes 190 may be provided in the third protective layer 180 to provide, for example, access for the sacrificial layer etch or to allow electrical contacts to the buried structures. As the uppermost layer, the upper membrane layer 210 is subsequently applied.
• the uppermost protective layer 180 forms part of the upper membrane 410.
• the upper membrane 410 in the layer structure contains at least one metal layer 210, which can also serve for the production of bond pads 220 for electrical contacting of the component.
• an additional metallization can be provided, which fulfills the same purpose.
• the layer 210 in FIG. If should represent the entire application-specific layer structure of the upper membrane 410, with the third protective layer 180 possibly also being able to be counted to the membrane.
• through-openings 230 are produced through the upper membrane and the third protective layer 180 as access for the etching medium except for the sacrificial layer 170.
• passage openings 230 can already be provided in the third protective layer 180 prior to the application of the second membrane layer 210, which through suitable structuring of the second membrane layer 210 can serve as access openings for the subsequent etching step.
• the etching step for sacrificial layer etching is preferably carried out using gases which selectively etch silicon, for example fluorine-containing plasmas (SF 6 , NF 3 ) or preferably by spontaneously etching gases such as ClF 3 or XeF 2 .
• the sacrificial layer 170 between the membranes 400 and 410, the region or regions 140 that allow access to the substrate, and a portion of the silicon substrate 100 underlying the membrane 400 and the regions 140, respectively, are etched out.
• the passage openings 230 can be closed in a further step by means of another layer.
• first membrane 400 only a part of the first membrane 400 or only the sacrificial layer 170 can be removed. This can be achieved by placing the through holes in the intermediate oxide layers or protective layers.
• All described method steps enable surface micromechanical processing of the wafer from the front side.
• a wafer handling on standardized systems is possible without the wafer has to be rotated.
• damage to the fragile micromechanical structures is less likely than with volume-mechanical processes in which the wafers have to be handled and processed on both sides.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Computer Hardware Design (AREA)
• Pressure Sensors (AREA)
• Micromachines (AREA)
• Measuring Fluid Pressure (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2005
  • 2005-02-18 DE DE102005007540A patent/DE102005007540A1/de not_active Withdrawn
  • 2005-12-21 KR KR1020077018811A patent/KR101074581B1/ko not_active IP Right Cessation
  • 2005-12-21 US US11/884,563 patent/US7863072B2/en not_active Expired - Fee Related
  • 2005-12-21 WO PCT/EP2005/057023 patent/WO2006087045A1/de active Application Filing
  • 2005-12-21 EP EP05823865A patent/EP1853514A1/de not_active Withdrawn
  • 2005-12-21 CN CN2005800481890A patent/CN101119924B/zh not_active Expired - Fee Related

Non-Patent Citations (1)

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