Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R19/00—Electrostatic transducers

Definitions

• the invention relates to a method for producing a filled depression in a material layer, and to an integrated circuit arrangement produced by the method.
• such a circuit arrangement comprises a CMOS microphone, in which a depression forms a cavity, the so-called rear side volume, over which a membrane is arranged, which is set into vibration by sound waves.
• CMOS microphone in which a depression forms a cavity
• rear side volume over which a membrane is arranged, which is set into vibration by sound waves.
• the vibrations are converted into electrical signals.
• the cover layer and the recess are produced in a single substrate. To do this, the recess is filled with a sacrificial layer. A perforated cover layer and a membrane are created over the sacrificial layer. The sacrificial layer is then removed by etching through an opening at the edge of the membrane.
• the thickness of a conformally deposited layer must be at least the depth of the depression so that the depression is filled by the layer.
• the associated depressions generally have the dimensions described.
• the recess in the second microphone is filled during the manufacturing process by deposition of the sacrificial layer, it is flat in contrast to the recess in the first microphone.
• the back volume of the second microphone is correspondingly smaller than that of the first microphone.
• micromechanical components such as rotation rate sensors or acceleration sensors, which have movable structures arranged in cavities, for which the greatest possible freedom of movement is sought.
• the German patent application DE 195 09 868 AI describes a manufacturing process for such micromechanical components. A lower sacrificial layer and a structural layer above it are produced and structured on a substrate, as a result of which a structure surrounded by a depression is produced. The depression is filled by depositing an upper sacrificial layer, over which a cover layer is applied. Using etch holes in the top layer, the sacrificial layers are removed and the recess forms part of a cavity in which the structure can move.
• shocks or rotations are detected with the aid of the structure, which can be set into lateral vibrations.
• the cover layer serves to protect the circuit arrangement.
• the sensitivity of the acceleration sensor or the rotation rate sensor is greater the thicker the structure, i.e. the deeper the depression is.
• the invention is based on the problem of specifying a production method in which a filled, at least a few ⁇ m deep recess can be produced in a material layer, which has a horizontal cross section in which at least one circular surface with a diameter of a few ⁇ m fits. Furthermore, an integrated circuit arrangement generated by the manufacturing method is to be specified.
• a method according to claim 1 at least a first structure and at least a second structure are produced in a region of the material layer provided for the depression, which adjoin one another laterally and which form a filling of the depression, and in which each of its parts each have opposing flank parts, the sides of which Distance from each other is less than about half a depth of the depression.
• the depression is not first produced as in the prior art and then filled in one step, which is why the deposition of a thick layer with all of its disadvantages is avoided.
• the method according to the invention enables the creation of filled deep depressions with large horizontal cross sections.
• Such a method is advantageous for any technical field in which depressions are filled with essentially conformal layers as standard.
• One such area is semiconductor process technology, for example.
• the described dimensions of the first structure and the second structure enable these structures to be produced by method steps which are independent of the depth of the depression.
• the first structure At least one narrow depression is first produced in a region of the material layer provided for the depression by removing a portion of the material layer.
• the narrow depression has a smaller horizontal cross section than the depression to be produced and forms part of the depression to be produced.
• Flank-forming layer-like parts of the first structure are then produced, which are laterally thickened until the parts meet and thereby form the first structure. An interface between the abutting parts is thus inside the first structure.
• the first structure is either in the narrow distribution deepening or outside of the narrow depression.
• the second structure is produced by initially producing flank-forming layer-like parts of the second structure, which are thickened laterally until the parts meet and thereby form the second structure. By filling the first structure and the second structure, which extend to a bottom of the depression, the filled depression is formed.
• the first structure and the second structure are produced in corresponding narrow recesses, which are filled by depositing an essentially conformal filling layer.
• the filling layer is initially created on the flanks of the narrow depression and forms the flank-forming layer-like parts of the structures there. In the further course of the deposition, these parts thicken laterally in the direction of the center of the narrow depression until opposing parts collide and the narrow depression is filled. Due to the small spacing of the flank parts from one another, the minimum thickness of the filling layer is determined by this spacing and not by the depth of the narrow depression. It is only half of this distance.
• the filling layer can therefore have a substantially smaller thickness than a thickness of a layer that would be required to fill the entire depression in one step.
• the first structure is meandering and twists through the recess.
• the second structure is also meandering, for example.
• there are a large number of strip-shaped second structures which are arranged in the turns of the first structure.
• a corresponding number of narrow recesses are created for the second structures.
• a large number of first structures can also be provided, which are, for example, cylindrical or strip-shaped.
• the shapes described are examples from an unlimited number of shapes that meet the above condition for the Flank parts meet and are also within the scope of the invention.
• the first structure can be produced in the narrow depression by filling the narrow depression by essentially conformally depositing a first filling layer.
• a further narrow depression is then produced by removing the parts of the material layer arranged between flanks of the first structure.
• the second structure is created by filling the further narrow depression by essentially conformally depositing a second fill layer.
• the narrow depression can be produced by etching the material layer selectively with respect to the first filling layer.
• the above-mentioned parts of the first fill layer can be removed by masked etching.
• the first fill layer is polished mechanically and mechanically until the material layer is exposed.
• a mask covers parts of the material layer lying outside of the area provided for the depression when the narrow depression is produced.
• a circuit arrangement according to the invention can comprise the filled depression.
• the filling of the depression serves as a sacrificial layer and is removed in a later process step.
• a lid structure can be created over the filled depression, which lies completely outside the depression and into which an opening is created. Using the opening, the first structure and the second structure can be removed by etching, whereby the recess forms a cavity.
• the first structure and the second structure consist of the same material.
• the removal can then take place in an etching step. If the etching step is isotropic, it is advantageous if the first structure and the second structure can be etched selectively with respect to the material layer.
• a movable structure can be created from the material layer.
• a lower sacrificial layer is applied and structured on a semiconductor substrate.
• the material layer is applied to the lower sacrificial layer.
• the material layer creates the structure that is laterally surrounded by the depression.
• the first structure and the second structure form part of an upper sacrificial layer that is adjacent to the lower sacrificial layer.
• the narrow depression is created in such a way that it extends to the lower sacrificial layer and cuts through the material layer.
• the lid structure with the opening is applied to the upper sacrificial layer covering the structure. Using the opening of the lid structure, the upper sacrificial layer and the lower sacrificial layer are removed, as a result of which the depression forms a first part of the cavity, which has at least further parts arranged below and above the structure.
• supports or suspensions can be provided which connect the structure to the substrate or to the lid structure.
• the lower op- layer creates an opening that extends to the substrate.
• the opening is filled.
• the filled opening forms the support that connects the material layer to the substrate.
• an opening is made in the upper sacrificial layer that extends to the structure.
• the opening is filled.
• the filled opening forms the suspension that connects the structure to the lid structure.
• a bottom of the depression can have adjoining regions over which one of the structures was generated during the method and which lie at different depths. Due to the dimensions of the structures, each of the parts of these areas each have opposing edges, the distance from one another of which is smaller than a few ⁇ . Since a depth difference between the areas is due to the fault tolerances, it is much smaller than the depths of the areas, i.e. than the depths of the deepening. If no lower sacrificial layer is provided, the shape of the floor is retained even if the structures have been removed during the manufacturing process.
• first of the regions of the bottom of the depression can be strip-shaped, run essentially parallel to one another and cross the depression. Second of the areas of the bottom of the depression are arranged between the first areas. In each first area, the bottom has a cuboid flat projection which is considerably longer than it is wide.
• An upper surface of the filler layer for the second structure if it is not planarized, has a slight indentation along a center line of the associated narrow depression.
• the narrow depressions are in the form of strip-shaped trenches running parallel to one another, during the deposition of the filler layer for the second structures along the center lines of the trenches, grooves are formed in an upper surface of this filler layer.
• the lid structure which is deposited above, fills the grooves and consequently has projections in the form of burrs.
• the depression has a depth that is greater than approximately 5 ⁇ m. It is within the scope of the invention if the depression has horizontal dimensions that are more than approximately 10 ⁇ m.
• the circuit arrangement comprises a rotation rate sensor or an acceleration sensor in which the movable structure can be set in lateral oscillations.
• the circuit arrangement comprises a microphone, in which the depression serves as a rear-side volume, and in which the cover structure is a perforated electrode.
• Another electrode is e.g. a membrane arranged over the lid structure.
• the circuit arrangement is a thermal sensor.
• a temperature measurement point is arranged above the recess so that a heat flow between the temperature measuring point and the substrate is as small as possible.
• the circuit arrangement is a high-frequency coil.
• the high-frequency coil is arranged above the depression, which is filled with insulating material, so that a capacitance between the high-frequency coil and the semiconductor substrate is as small as possible.
• the circuit arrangement is a pump or a valve for gases or liquids.
• the depression acts as a flow channel.
• the first structure and the second structure can contain oxide.
• FIG. 1 shows a cross section through a first substrate after a lower sacrificial layer, a layer, a support, a first mask and first trenches have been produced.
• FIG. 2 shows the cross section from FIG. 1 after first structures and a second mask have been produced as parts of an upper sacrificial layer and parts of the first mask have been removed.
• FIG. 3 shows the cross section from FIG. 2 after parts of the layer have been removed and second structures have been produced as parts of the upper sacrificial layer.
• FIG. 4 shows the cross section from FIG. 3 after a cover layer and a cavity-forming depression
• FIG. 5 shows a cross section through a second substrate after a mask, trenches and first structures have been produced.
• FIG. 6 shows the cross section from FIG. 5 after the first mask has been removed and a filling layer, second structures and a cover layer have been produced.
• a first substrate 1 made of silicon is provided as the starting material.
• SiO 2 is deposited in a thickness of approximately 1 ⁇ m on the first substrate 1 and structured in a TEOS process (see FIG. 1). In this case, a part of the lower sacrificial layer U is created which extends as far as the first substrate 1.
• polysilicon is deposited over the lower sacrificial layer U to produce a material layer S (see FIG. 1).
• the recess is filled in which a support T is created.
• SiO 2 is deposited in a thickness of approximately 200 nm and structured by a photolithographic process.
• first trenches G 1 running parallel to one another and approximately 1 ⁇ m wide are produced.
• the first trenches G1 are at a distance of approximately 1 ⁇ m from one another (see FIG. 1).
• the first trenches Gl extend into the first sacrificial layer U and are approximately 5 ⁇ m deep.
• first filling layer F1 made of SiO 2 is then deposited in a TEOS process. Parts of the first fill layer F1 which fill the first trenches Gl form the first structures Sl (see Figure 2). The thickness of the first structures S1 corresponds approximately to the depth of the first trenches Gl.
• a second mask 3 made of photoresist which covers parts of the first filling layer F1 lying outside the recess to be produced and the first structures S1, parts of the first filling layer F1 and the first mask 2 arranged in the region of the recess V to be produced are covered with e.g. B. removed hydrofluoric acid (see Figure 2). The second mask 3 is then removed.
• an approximately 1 ⁇ m thick second fill layer F2 made of SiO 2 is deposited. Parts of the second fill layer F2, which fill the second trenches G2, form second structures S2.
• the first fill layer F1 and the second fill layer F2 together form an upper sacrificial layer.
• the first trenches G1 and the second trenches G2 together form the depression V.
• a bottom of the depression V has mutually adjacent first areas B1 and second areas B2, in which each of their parts each have mutually opposite edges, the spacing from one another of less than a few ⁇ m is.
• One of the first structures S1 is arranged above the first regions B1.
• the second structures S2 ′ are arranged above the second regions B2.
• a bottom of the first trenches Gl coincides with the first areas B1.
• a bottom of the second trenches G2 corresponds to the second areas B2.
• a depression is formed from the material layer S by the depression V, which is laterally surrounded by the depression V.
• the semiconductor structure is approx. 50 ⁇ m wide and approx. 50 ⁇ m long.
• the support T connects it to the first substrate 1.
• An upper surface of the second fill layer F2 has along center lines of the second trenches G2 running grooves (see Figure 3).
• the depression V has a horizontal cross section in which a circular surface with a diameter of approximately 7 ⁇ m fits.
• lid structure D polysilicon is deposited in a thickness of approximately 1 ⁇ m.
• the lid structure D has projections a in the region of the recess V in the form of ridges that run in the grooves (see FIG. 4).
• the downwardly tapering projections a are substantially smaller than the depth of the depression V and are arranged over the second regions B2 of the bottom of the depression V.
• the courses of the projections a essentially coincide with the courses of center lines of the second areas B2.
• An opening 0 is created in the lid structure D, through which the upper sacrificial layer and the lower sacrificial layer U are removed in an etching step.
• a buffered hydrofluoric acid for example, is suitable as an etchant.
• the depression V forms part of a cavity which is delimited at the top by the lid structure D.
• the semiconductor structure can be vibrated by vibrations. The lateral freedom of movement is about 7 ⁇ m.
• the circuit arrangement is suitable, for example, as a rotation rate sensor or as an acceleration sensor.
• further components are arranged in the first substrate 1.
• circuit arrangements are, for example, micro- hair dryers, thermal sensors, pumps and valves for gases or liquids and integrated high-frequency coils.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Pressure Sensors (AREA)
• Micromachines (AREA)
• Measuring Fluid Pressure (AREA)
• Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
• Internal Circuitry In Semiconductor Integrated Circuit Devices (AREA)
• Weting (AREA)
• Production Of Multi-Layered Print Wiring Board (AREA)

Applications Claiming Priority (3)

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• 1999
  • 1999-07-02 AT AT99945888T patent/ATE409398T1/de not_active IP Right Cessation
  • 1999-07-02 JP JP2000559711A patent/JP2002520862A/ja not_active Withdrawn
  • 1999-07-02 WO PCT/DE1999/002041 patent/WO2000003560A2/fr active IP Right Grant
  • 1999-07-02 DE DE59914876T patent/DE59914876D1/de not_active Expired - Lifetime
  • 1999-07-02 EP EP99945888A patent/EP1101389B1/fr not_active Expired - Lifetime
• 2001
  • 2001-01-08 US US09/756,532 patent/US6724058B2/en not_active Expired - Lifetime

Non-Patent Citations (1)

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