Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10B—ELECTRONIC MEMORY DEVICES
  • H10B12/00—Dynamic random access memory [DRAM] devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D1/00—Resistors, capacitors or inductors
  • H10D1/01—Manufacture or treatment
  • H10D1/041—Manufacture or treatment of capacitors having no potential barriers
  • H10D1/042—Manufacture or treatment of capacitors having no potential barriers using deposition processes to form electrode extensions
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10B—ELECTRONIC MEMORY DEVICES
  • H10B12/00—Dynamic random access memory [DRAM] devices
  • H10B12/01—Manufacture or treatment
  • H10B12/02—Manufacture or treatment for one transistor one-capacitor [1T-1C] memory cells
  • H10B12/03—Making the capacitor or connections thereto
  • H10B12/033—Making the capacitor or connections thereto the capacitor extending over the transistor
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D1/00—Resistors, capacitors or inductors
  • H10D1/60—Capacitors
  • H10D1/68—Capacitors having no potential barriers
  • H10D1/692—Electrodes
  • H10D1/711—Electrodes having non-planar surfaces, e.g. formed by texturisation
  • H10D1/716—Electrodes having non-planar surfaces, e.g. formed by texturisation having vertical extensions
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S438/00—Semiconductor device manufacturing: process
  • Y10S438/942—Masking
  • Y10S438/947—Subphotolithographic processing

Definitions

• a stacked-capacitor DRAM cell comprises a MOS transistor and a storage capacitor, the MOS transistor being arranged in a silicon substrate and the storage capacitor consisting of two doped polysilicon layers and an interposed dielectric layer which are arranged on the surface of the substrate .
• the storage capacitor completely or partially covers the area covered by the
• Transistor is occupied.
• the storage node ie the electrode of the storage capacitor on which the information is stored in the form of charge
• the bottom surface which is arranged on the surface of the substrate, it comprises a jacket surface which projects upwards.
• the dielectric layer is arranged on the surface of the bottom surface and on the inside and outside on the surface of the outer surface.
• the cell plate ie the second electrode of the storage capacitor, is then arranged on the surface of the dielectric layer. In this way, the area of the capacitor can be increased drastically compared to the area occupied on the substrate.
• an auxiliary layer is first produced on the surface of the substrate. Openings are made in this. to
• Formation of the storage node is a thin layer of doped polysilicon on the auxiliary layer with the
• the part of the polysilicon layer deposited on the side walls and the bottom of the openings forms the later storage node.
• the side walls of the openings should therefore be as vertical as possible.
• a storage dielectric is applied over the entire surface. This runs both on the inner and on the outer surfaces of the free-standing jacket part of the storage node.
• the cell plate is then applied over the entire surface as a counter electrode.
• the auxiliary layer is applied to the surface of the substrate in which the MOS transistors were previously manufactured. A cell contact must be made between the storage node and the respective active region of the associated transistor. This can follow directly or via additional, electrically conductive structures.
• the surface of the substrate is usually covered with an insulating layer. When producing the opening in the auxiliary layer, it must be ensured that there is no uncontrolled structuring of the insulating layer lying under the auxiliary layer. If holes are created in the insulating layer in addition to the cell contacts to other conductive areas during the production of the openings, short circuits occur via these the storage node subsequently formed. This should be avoided.
• auxiliary layer From Y. Kawamoto et al, Symp. On VLSI-Technology 1990, p. 13 it is known to form the auxiliary layer from polyimide.
• the production of the openings in the auxiliary layer is then not critical since polyimide can be etched with good selectivity to SiO 2 .
• a polysilicon layer is deposited on the surface of the auxiliary polyimide layer in order to produce the storage nodes. Because of the low temperature stability of the polyimide, the temperature during the polysilicon deposition must be limited.
• the invention is based on the problem of specifying a further method for producing storage capacitors for DRAM cells, which is suitable for use in the production of a stacked capacitor DRAM cell and in which an uncontrolled free etching of electrically conductive structures in the substrate during Production of openings in an auxiliary layer arranged on the surface of the substrate is reliably avoided.
• This problem is solved according to the invention by a method according to claim 1.
• a first auxiliary layer made of polysilicon is deposited over the entire surface of a substrate provided with SiO 2 .
• the substrate are before
• the first auxiliary layer is structured in accordance with the arrangement of the storage capacitors, so that it has openings which each run between storage nodes of adjacent storage capacitors.
• a second auxiliary layer made of SiO 2 is deposited over the entire surface, the openings in the first auxiliary layer being filled with SiO 2 .
• SiO 2 has good selectivity too
• Polysilicon can be etched so that the surface of the first auxiliary layer is exposed in a selective etching process by etching back the second auxiliary layer. SiO 2 remains in the openings as a placeholder. The first auxiliary layer is selectively completely removed to SiO 2 , so that the placeholders remain.
• a conductive structure for connecting the storage nodes is covered only by a thin SiO 2 layer. This is removed by briefly etching back SiO 2 over the entire area.
• the storage nodes By depositing a doped poly over the entire surface Silicon layer and exposing the surface of the placeholders in the upper area of the placeholders, the storage nodes are formed. In this way, the storage nodes completely cover the area within the placeholders and the side walls of the placeholders essentially. Storage nodes produced in this way are essentially cylindrical, the area within the placeholders forming the base area and the portion of the polysilicon layer arranged on the side walls of the placeholders forming the outer surface of a cylinder. After removing the placeholders selectively for the storage nodes, storage dielectric and a conductive layer as a cell plate are produced over the entire surface.
• the first auxiliary layer is formed from polysilicon and is continuously present under the first auxiliary layer SiO 2 and because polysilicon can be etched with good selectivity to SiO 2 , the formation of the openings in the first auxiliary layer requires an uncontrolled exposure of electrical structures below the SiO 2 surface not to be feared.
• the first auxiliary layer is structured using a photoresist mask. All furthermore
• Structures can be self-adjusted, i.e. H. without further
• Photoresist mask done. A photoresist mask would be
• a photoresist layer to expose the surface in the upper region of the placeholder, which is removed by back-exposure and development only in the upper part of the placeholders covered with the doped polysilicon layer.
• the placeholder is e.g. B. removed by SiO 2 etching, in which the etching removal is set over the etching time.
• SiO 2 etching in which the etching removal is set over the etching time.
• an Si 3 N 4 layer is deposited which is thinner than it corresponds to half the width of the openings in the first auxiliary layer.
• the surface of the Si 3 N 4 layer is exposed in the region of the first auxiliary layer.
• the surface of the first auxiliary layer is then exposed to polysilicon.
• the placeholders are surrounded by the portion of the Si 3 N 4 layer surrounding them in the openings.
• the placeholders are removed by SiO 2 etching which is selective with respect to Si 3 N 4 .
• An Si 3 N 4 etching is then carried out selectively with respect to polysilicon and SiO 2 , the residues of the Si3N4 layer being completely removed.
• Fig. 1 shows a section through a substrate
• the entire surface is provided with SiO 2 .
• 2 shows the substrate after deposition of a first one
• Auxiliary layer. 4 shows the substrate after the formation of placeholders.
• 5 shows the substrate after deposition of a doped polysilicon layer.
• FIG. 6 shows the substrate after the formation of storage nodes.
• Fig. 7 shows the substrate according to the invention
• the method according to the invention is based on a substrate 1 (see FIG. 1) in which transistors for a DRAM cell arrangement were previously produced. For the sake of clarity, these transistors are not shown in FIG.
• the substrate 1 comprises electrically conductive structures 2, via which the transistors are electrically connected to storage capacitors to be produced by the method according to the invention.
• An insulating layer 3 is provided on the surface of the substrate 1, which completely covers the electrically conductive structures 2 and other electrically conductive components, which are not shown.
• the insulating layer 3 consists essentially of SiO 2 .
• a first auxiliary layer A is applied to the entire surface of the insulating layer 3 (see FIG. 2).
• the first auxiliary layer A is made of polysilicon z. B. applied by CVD ab divorce.
• the first auxiliary layer A is z. B. 1 micron applied.
• the thickness of the first auxiliary layer A determines the height of the cylindrical side surfaces of the storage nodes to be produced later.
• a photoresist mask 5 is applied to the first auxiliary layer A.
• the photoresist mask 5 is produced by depositing a photoresist layer, exposing and developing the photoresist layer. In a dry etching step, e.g. B.
• the ste auxiliary layer A is structured using the photoresist mask 5 as an etching mask (see FIGS. 2 and 3).
• the first auxiliary layer A Openings 6 formed.
• the openings 6 each run between locations at which storage nodes of adjacent storage capacitors are later produced.
• the remaining first auxiliary layer A covers those areas of the surface of the insulating layer 3 which are later covered by storage nodes.
• An Si 3 N 4 layer 7 is subsequently covered over the entire surface in a thickness of, for. B. 20 nm deposited.
• a second auxiliary layer 8 is deposited over the entire surface of the Si 3 N 4 layer 7.
• the second auxiliary layer 8 is formed from SiO 2 .
• the second auxiliary layer 8 is deposited in such a thickness that the openings 6 are completely filled with SiO 2 .
• the thickness is z. B. 200 nm.
• the deposition of the second auxiliary layer 8 takes place, for. B.
• the second auxiliary layer 8 is removed outside the openings 6.
• the surface of the Si 3 N 4 layer 7 is first exposed.
• the Si 3 N 4 layer 7 is removed from horizontal surfaces of the first auxiliary layer A made of polysilicon. The etching takes place selectively to polysilicon.
• the openings 6 remain filled with a placeholder 81 made of SiO 2 , which is the remainder of the second auxiliary layer 8. Between the placeholder 81 and the surrounding first
• Si 3 N 4 of the Si 3 N 4 layer 7 remains arranged
• the first auxiliary layer A by wet chemical etching with z. B. Choline removed. This etching step is carried out selectively for SiO 2 and Si 3 N 4 . Since under the first auxiliary layer A the insulating layer 3 covers the entire surface of SiO 2 is in the process of removing the first
• Auxiliary layer A ensures that no uncontrolled etching into the insulating layer 3 takes place.
• the SiO 2 acts as an etch stop in the wet chemical etching.
• the insulating layer 3 above the electrically conductive structures 2 is subsequently removed in a dry etching process in order to open contact with the electrically conductive structures 2.
• the preprocessing must ensure that this dry etching process in SiO 2 can not produce undesired short circuits. This is done in particular by adjusting the layer thickness of the insulating layer 3.
• a doped polysilicon layer 9 is deposited over the entire surface in a thickness of z. B. 100 nm.
• the doped polysilicon layer 9 is deposited substantially conformally and completely covers the placeholder 81 (see FIG. 5).
• a photoresist layer is then deposited over the entire surface, which completely covers the doped polysilicon layer 9.
• the photoresist layer is back exposed and developed. During back exposure, the photoresist layer is exposed only to a predeterminable depth, so that only the upper part of the photoresist layer is removed during development.
• the photoresist layer is exposed to such an extent that a developed photoresist layer 10 is formed which leaves the upper part of the placeholders 81 covered with the doped polysilicon layer 9 uncovered (see FIG. 6).
• the doped polysilicon layer 9 is then structured in an anisotropic dry etching process in such a way that the horizontal surface of the placeholder 81 and the surrounding Si 3 N 4 of the Si 3 N 4 layer 7 is exposed.
• the placeholders 81 are selectively removed from Si 3 N 4 and polysilicon in an etching step using NH 4 F, HF (5: 1).
• the Si 3 N 4 acts as an etch stop.
• the Si 3 N 4 acts as an etch stop.
• the Si 3 N 4 layer 7 can be dispensed with. This leads to process simplification.
• a storage dielectric z. B produced by producing thermal SiO 2 , Si 3 N 4 and thermal SiO 2 .
• a cell plate 12 made of doped polysilicon is produced over the entire surface of the storage dielectric 11.
• the extent of the individual storage capacitors is determined by the geometry of the storage nodes 91 (see FIG. 7).
• the storage capacitor includes the surface of the inside and outside of the cylindrical part of the storage node 91
• insulating layer 3 has a flat surface.
• the method according to the invention can be used analogously if the insulating layer is provided with a surface topology.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Semiconductor Memories (AREA)
• Semiconductor Integrated Circuits (AREA)

Priority Applications (6)

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Family Applications (1)

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Citations (3)

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• 1992
  • 1992-07-08 DE DE4222467A patent/DE4222467C1/de not_active Expired - Fee Related
• 1993
  • 1993-06-15 JP JP50280694A patent/JP3330605B2/ja not_active Expired - Fee Related
  • 1993-06-15 KR KR1019950700021A patent/KR100309614B1/ko not_active Expired - Fee Related
  • 1993-06-15 HK HK98101321A patent/HK1002337A1/xx not_active IP Right Cessation
  • 1993-06-15 AT AT93912589T patent/ATE160652T1/de not_active IP Right Cessation
  • 1993-06-15 EP EP93912589A patent/EP0649566B1/de not_active Expired - Lifetime
  • 1993-06-15 US US08/351,464 patent/US5496757A/en not_active Expired - Lifetime
  • 1993-06-15 WO PCT/DE1993/000516 patent/WO1994001891A1/de not_active Ceased
  • 1993-06-15 DE DE59307748T patent/DE59307748D1/de not_active Expired - Fee Related
  • 1993-07-07 TW TW082105415A patent/TW358242B/zh not_active IP Right Cessation

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