Enclosed ferroelectric stacked capacitor
First Claim
1. A storage capacitor constructed on a silicon substrate, said capacitor comprising:
- a conductive storage node plate comprising a rectangular upper portion and a lower portion that extends downward and makes contact at a storage node junction, said storage node plate conforms to an existing topology of said silicon substrate;
a cell dielectric adjacent and coextensive said storage node plate except at said storage node junction contact; and
conductive double cell plates adjacent and coextensive said cell dielectric.
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Abstract
This invention relates to semiconductor circuit memory storage devices and more particularly to a process to develop three-dimensional stacked cell capacitors using a PZT ferroelectric material as a storage cell dielectric for use in high-density dynamic random access memory (DRAM) arrays. The present invention employs using PZT ferroelectric for the storage cell dielectric in three-dimensional stacked capacitor technology and develops an existing stacked capacitor fabrication process to construct a PZT three-dimensional stacked capacitor cell (the EFSC) that will allow denser storage cell fabrication with minimal increases of overall memory array dimensions. A capacitance gain of 3 to 10X or more over that of a conventional 3-dimensional storage cell is gained by using PZT ferroelectric as the storage cell dielectric.
44 Citations
25 Claims
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1. A storage capacitor constructed on a silicon substrate, said capacitor comprising:
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a conductive storage node plate comprising a rectangular upper portion and a lower portion that extends downward and makes contact at a storage node junction, said storage node plate conforms to an existing topology of said silicon substrate; a cell dielectric adjacent and coextensive said storage node plate except at said storage node junction contact; and conductive double cell plates adjacent and coextensive said cell dielectric.
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2. A DRAM storage capacitor constructed on a silicon substrate, said capacitor comprising:
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a first conductive layer, said first conductive layer patterned to form a storage node plate having an upper rectangular shaped portion and a lower portion that extends downward and makes contact at a storage node junction, said storage node plate conforms to an existing topology of said silicon substrate; a second conductive layer, said second conductive layer patterned to form a rectangular shaped bottom cell plate of a double cell plate; a cell dielectric layer being adjacent said storage node plate and said bottom cell plate and coextensive therewith except at a region for said contact at said storage node junction; and a third conductive layer forming a top cell plate of said double cell plate, said top plate connecting to said bottom cell plate to form a double cell plate, said double cell plate being adjacent said second cell dielectric layer and coextensive therewith. - View Dependent Claims (3)
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4. A DRAM memory array constructed on a silicon substrate, said memory array comprising:
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a plurality of active areas arranged in parallel interdigitated rows and parallel non-interdigitated columns, said active areas separated by isolation means, each of said active areas having a digit line junction, and a storage node junction; a plurality of parallel conductive word lines aligned along said rows such that a digit line junction and a storage node junction within each active area are bridged by a word line, each word line being insulated from associated active areas by a gate dielectric layer; a plurality of parallel conductive digit lines, aligned along said columns such that a digit line makes electrical contact with each digit line junction within a column, said digit lines running perpendicular to and over said word lines forming a 3-dimensional, waveform-like topology, said digit and word lines electrically separated from one another by isolation means; and at least one storage capacitor for each active area, each capacitor having a storage node plate that is in electrical contact with its associated active area and a double cell plate that is common to the entire array, each storage node plate being insulated from said double cell plate by a cell dielectric layer. - View Dependent Claims (5, 6)
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7. A process for fabricating a DRAM array on a silicon substrate, said process comprising the following sequence of steps:
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creating a plurality of separately isolated active areas arranged in parallel interdigitated rows and parallel non-interdigitated columns; creating a gate dielectric layer on top of each active area; depositing a first conductive layer superjacent surface of said array; depositing a first dielectric layer superjacent said first conductive layer; masking and etching said first conductive and said first dielectric layers to form a plurality of parallel conductive word lines aligned along said rows such that each said word line passes over a inner portion of each said active area being separated therefrom by a remanent of said gate dielectric layer; creating of a conductively-doped digit line junction and storage node junction within each said active area on opposite sides of each said word line; depositing a second dielectric layer superjacent said array surface; creating a first aligned buried contact location at each said digit line junction in each said active area; depositing a second conductive layer superjacent said array surface, said second conductive layer making direct contact to said digit line junctions at said first buried contact locations; depositing a third dielectric layer superjacent to said second conductive layer; masking and etching said second conductive layer and said third dielectric layer to form a plurality of parallel conductive digit lines aligned along said columns such that a digit line makes electrical contact at each digit line junction within a column, said digit lines running perpendicular to and over said word lines forming a 3-dimensional, waveform-like topology; depositing a fourth dielectric layer on surface of said silicon; masking and etching a buried contact location allowing access to an active area and thereby forming vertical sidewalls within opening of said buried contact location; depositing a third conductive layer superjacent said fourth dielectric layer and said buried contact opening; planarizing said third conductive layer; patterning said third conductive layer to form an upper rectangular shaped portion and a lower portion of a storage node, said lower portion making contact to said active area at said buried contact location, said third conductive layer conforming to said 3-dimensional, waveform shaped topology; depositing a fifth dielectric layer superjacent said existing waveform shaped topology; anisotropically etching said fifth dielectric layer thereby forming vertical dielectric spacers adjacent sidewalls of said conductive upper rectangular shaped portion; depositing and planarizing a fourth conductive layer superjacent said existing waveform shaped topology; isotropically etching said vertical dielectric spacers thereby leaving a conductive rectangular shaped bottom cell plate; depositing a cell dielectric layer superjacent said existing waveform shaped topology, thereby enclosing exposed portion of said bottom cell plate and upper portion of said storage node plate; depositing a fifth conductive layer superjacent said cell dielectric layer, thereby forming a top cell plate, said top cell plate connecting to said bottom cell plate, said top and said bottom cell plates combining to form a double cell plate common to the entire memory array. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A process for fabricating a DRAM storage capacitor on a silicon substrate having active areas, word lines and digit lines, said process comprising the following sequence of steps:
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depositing a first dielectric layer on surface of said silicon; masking and etching a buried contact location allowing access to an active area and thereby forming vertical sidewalls within opening of said buried contact location; depositing a first conductive layer superjacent said first dielectric layer and said buried contact opening; planarizing said first conductive layer; patterning said first conductive layer to form an upper rectangular shaped portion and a lower portion of a storage node, said lower portion making contact to said active area at said buried contact location, said first conductive layer conforming to said 3-dimensional, waveform shaped topology; depositing a second dielectric layer superjacent said existing waveform shaped topology; anisotropically etching said second dielectric layer thereby forming vertical dielectric spacers adjacent sidewalls of said conductive upper rectangular shaped portion; depositing and planarizing a second conductive layer superjacent said existing waveform shaped topology; isotropically etching said vertical dielectric spacers thereby leaving a conductive rectangular shaped bottom cell plate; depositing a cell dielectric layer superjacent said existing waveform shaped topology, thereby enclosing exposed portion of said bottom cell plate and upper portion of said storage node plate; depositing a third conductive layer superjacent said cell dielectric layer, thereby forming a top cell plate, said top cell plate connecting to said bottom cell plate, said top and said bottom cell plates combining to form a double cell plate common to the entire memory array. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
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Specification