Memory cell with a stacked capacitor
First Claim
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1. A method for forming a memory cell including a transistor and a capacitor comprising the steps of:
- forming in a semiconductor chip a transistor having first and second regions of one conductivity-type spaced apart by a region of the opposite conductivity-type along a top surface of the chip;
forming a dielectric layer over a top surface of the chip;
forming a contact hole with substantially vertical side walls in the dielectric layer by anisotropic etching for exposing a top surface portion of the second region of the transistor;
filling the contact hole with a conductive fill for providing a low resistance connection to the second region;
removing the top portion of the conductive fill of the contact hole for forming a recess in the conductive fill and exposing the dielectric layer in the contact hole;
etching the exposed dielectric layer isotropically for widening the recess and enlarging the surface area of the contact hole in the dielectric layer;
depositing a first conductive layer conformally over the enlarged surface area of the contact hole suitable for use as a lower plate of a storage capacitor;
patterning the first conductive layer to confine the first conductive layer to the interior of the contact hole by etching a portion of the first conductive layer with etchants introduced at an acute angle relative to the top surface;
depositing a layer of a material of high dielectric constant for covering over the first conductive layer; and
depositing s second conductive layer conformally over the last dielectric layer suitable for use as an upper plate of a capacitor that comprises the electrically isolated upper and lower plates separated by the layer of high dielectric constant.
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Abstract
A semiconductor memory cell includes a field effect transistor coupled to a storage capacitor that formed as a multilayer stack over the surface of the silicon chip of the cell. The capacitor is formed by three conformal layers over the surface of a cup-shaped contact hole in a silicon oxide layer overlying the surface of the chip.
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Citations
15 Claims
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1. A method for forming a memory cell including a transistor and a capacitor comprising the steps of:
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forming in a semiconductor chip a transistor having first and second regions of one conductivity-type spaced apart by a region of the opposite conductivity-type along a top surface of the chip;
forming a dielectric layer over a top surface of the chip;
forming a contact hole with substantially vertical side walls in the dielectric layer by anisotropic etching for exposing a top surface portion of the second region of the transistor;
filling the contact hole with a conductive fill for providing a low resistance connection to the second region;
removing the top portion of the conductive fill of the contact hole for forming a recess in the conductive fill and exposing the dielectric layer in the contact hole;
etching the exposed dielectric layer isotropically for widening the recess and enlarging the surface area of the contact hole in the dielectric layer;
depositing a first conductive layer conformally over the enlarged surface area of the contact hole suitable for use as a lower plate of a storage capacitor;
patterning the first conductive layer to confine the first conductive layer to the interior of the contact hole by etching a portion of the first conductive layer with etchants introduced at an acute angle relative to the top surface;
depositing a layer of a material of high dielectric constant for covering over the first conductive layer; and
depositing s second conductive layer conformally over the last dielectric layer suitable for use as an upper plate of a capacitor that comprises the electrically isolated upper and lower plates separated by the layer of high dielectric constant. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 14)
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10. A method of forming a stacked capacitor on the top surface of a silicon wafer for use as a storage capacitor in series with a switching transistor formed in a top surface portion of the silicon wafer comprising the steps of:
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forming a first dielectric layer over the top surface of the silicon wafer;
forming a contact hole in the dielectric coating for exposing the portion of the silicon transistor to which the lower plate of the storage capacitor is to be electrically connected;
partially filling the contact hole with doped polysilicon suitable for forming an electrical connection to said portion of the silicon transistor;
widening the unfilled portion of the contact hole to essentially a cup-shape for enlarging the surface area of the unfilled portion;
forming a diffusion barrier conductive layer over the doped polysilicon;
depositing conformally over the surface of the unfilled portion of the contact hole, a first conductive layer suitable for serving as said lower plate of the capacitor;
ion etching to remove an upper portion of the first conductive layer in the contact hole;
depositing conformally over the first conductive layer and the contact hole a second dielectric layer suitable for serving as the dielectric of the capacitor; and
depositing conformally over the second dielectric layer a second conductive layer suitable for serving as the upper plate of the capacitor without providing an electrical short to the lower plate of the capacitor. - View Dependent Claims (11, 12, 13, 15)
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Specification