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  Low-density, high-resistivity titanium nitride layer for use as a contact for low-leakage dielectric layers and method of makingUSPTO Application #: 20060033180Title: Low-density, high-resistivity titanium nitride layer for use as a contact for low-leakage dielectric layers and method of making Abstract: A low-density, high-resistivity layer of a PVD sputter-deposited material, preferably titanium nitride, when coupled with a dielectric, makes a superior low-leakage insulating barrier for use in semiconductor devices. The material is created by sputtering methods that cause the ions to strike the deposition surface with reduced energy, for example in an ion metal plasma chamber with no self-bias accelerating ions normal to the deposition surface, or in a standard PVD chamber with pressure increased. (end of abstract)
Agent: Matrix Semiconductor, Inc. - Santa Clara, CA, US Inventor: S. Brad Herner USPTO Applicaton #: 20060033180 - Class: 257530000 (USPTO) Related Patent Categories: Active Solid-state Devices (e.g., Transistors, Solid-state Diodes), Integrated Circuit Structure With Electrically Isolated Components, Passive Components In Ics, Including Programmable Passive Component (e.g., Fuse), Anti-fuse The Patent Description & Claims data below is from USPTO Patent Application 20060033180. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] This application is a divisional of Herner, U.S. patent application Ser. No. 10/611,245, "Low-Density, High-Resistivity Titanium Nitride Layer for Use as a Contact for Low-Leakage Dielectric Layers," filed Jun. 30, 2003, assigned to the assignee of the present invention and hereby incorporated by reference in its entirety. BACKGROUND OF THE INVENTION [0002] Many semiconductor devices include a dielectric layer between two conductors. If this dielectric is imperfect, leakage current across the dielectric may adversely affect device performance. [0003] The invention relates to the use in semiconductor devices of a low-density, high-resistivity metal layer, preferably titanium nitride. Paired with a dielectric, the layer reduces leakage current across the dielectric. [0004] It is known in the art that ionized metal plasma deposition of titanium nitride with no applied self-bias creates a low-density, high-resistivity titanium nitride (see Tanaka et al., "Properties of titanium nitride film deposited by ionized metal plasma source," Journal of Vacuum Science Technology, March/April 1999), but the usefulness of this material in semiconductor devices according to the present invention has not been previously recognized. SUMMARY OF THE INVENTION [0005] The present invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims. In general, the invention is directed to a low-density, high-resistivity material which can be paired with a dielectric to form a low-leakage contact, and its use in semiconductor devices. [0006] A first aspect of the invention provides for a method for forming titanium nitride in a semiconductor device comprising providing a surface for a semiconductor device; and depositing a film of titanium nitride on the surface by physical vapor deposition wherein, for any portion of the film more than about 20 angstroms thick, the density of the titanium nitride is less than about 4.0 grams per cubic cm. [0007] Another aspect of the invention provides for a semiconductor device comprising a first conductive or semiconductive material; a layer of titanium nitride, wherein, for any portion of the titanium nitride layer more than about 20 angstroms thick, the resistivity of the titanium nitride is greater than about 300 microOhm-cms and the density is less than about 4.25 grams per cubic cm; and a dielectric layer interposed between the first conductive or semiconductive material and the titanium nitride layer. [0008] Yet another aspect of the invention calls for a semiconductor device comprising silicon; in contact with the silicon, a layer of silicon dioxide or silicon nitride; and in contact with the silicon dioxide or silicon nitride layer, a layer of nitrogen-rich titanium nitride, wherein, for any portion of the titanium nitride layer more than about 20 angstroms thick, the ratio of titanium to nitrogen is greater than about 1.2:1 and the density is less than about 4.0 grams per cubic cm. [0009] A preferred embodiment provides for a method for making a thin film transistor comprising forming a polysilicon layer; forming a silicon dioxide layer in contact with the polysilicon layer; forming a titanium nitride layer in contact with the silicon dioxide layer wherein, for any portion of the titanium nitride layer more than about 20 angstroms thick, the resistivity of the titanium nitride is greater than about 300 microOhm-cms and the density of the titanium nitride is less than about 4.25 grams per cubic cm; and patterning and etching the titanium nitride. [0010] Another embodiment provides for a monolithic three dimensional memory array comprising polysilicon; in contact with the polysilicon, a layer of silicon dioxide or silicon nitride; and in contact with the silicon dioxide or silicon nitride layer, a layer of titanium nitride, wherein, for any portion of the titanium nitride layer more than about 20 angstroms thick, the resistivity of the titanium nitride is greater than about 300 microOhm-cms and the density of the titanium nitride is less than about 4.25 grams per cubic cm. [0011] An aspect of the invention provides for a method for forming titanium nitride in a semiconductor device comprising providing a surface for a semiconductor device; and depositing on the surface a film of titanium nitride by physical vapor deposition wherein, for any portion of the film more than about 20 angstroms thick, the deposition is performed with substantially no self-bias and with pressure greater than about 15 mTorr. [0012] Another aspect of the invention provides for a method for forming titanium nitride for use in a semiconductor device comprising providing a surface for a semiconductor device; on the surface, depositing titanium nitride wherein, for any portion of the titanium nitride layer more than about 20 angstroms thick, the resistivity of the titanium nitride is greater than about 300 microOhm-cms and the ratio of nitrogen to titanium is greater than about 1.2:1. [0013] A preferred embodiment provides for a semiconductor device comprising a dielectric-rupture antifuse; and a layer of low-density, high-resistivity material in contact with the antifuse wherein the low-density, high-resistivity material is titanium nitride, tungsten nitride, tantalum nitride, titanium tungsten, tungsten, or aluminum, and wherein a portion of the low-density, high-resistivity material having a thickness greater than about 20 angstroms was deposited by physical vapor deposition in a chamber with substantially no self-bias. [0014] Another aspect of the invention provides for a semiconductor device comprising a dielectric layer; a titanium nitride layer in contact with the dielectric layer wherein, for any portion of the titanium nitride layer thicker than about 20 angstroms, the ratio of nitrogen to titanium is greater than about 1.2:1, and wherein, for any portion of the titanium nitride layer thicker than about 20 angstroms, the resistivity of the titanium nitride layer is greater than about 300 microOhm-cms. [0015] A preferred embodiment provides for a method for forming titanium nitride in a semiconductor device comprising providing a surface for a semiconductor device; and depositing a film of titanium nitride on the surface by physical vapor deposition wherein the density of the titanium nitride is less than about 4.0 grams per cubic cm. [0016] Another preferred embodiment provides for a semiconductor device comprising a first conductive or semiconductive material; a layer of titanium nitride the resistivity of the titanium nitride is greater than about 300 microOhm-cms and the density is less than about 4.25 grams per cubic cm; and a dielectric layer interposed between the first conductive or semiconductive material and the titanium nitride layer. [0017] Yet another preferred embodiment provides for a semiconductor device comprising silicon; in contact with the silicon, a layer of silicon dioxide or silicon nitride; and in contact with the silicon dioxide or silicon nitride layer, a layer of nitrogen-rich titanium nitride, wherein the ratio of titanium to nitrogen is greater than about 1.2:1 and the density is less than about 4.0 grams per cubic cm. [0018] Another preferred embodiment provides for a method for making a thin film transistor comprising forming a polysilicon layer; forming a silicon dioxide layer in contact with the polysilicon layer; forming a titanium nitride layer in contact with the silicon dioxide layer wherein the resistivity of the titanium nitride is greater than about 300 microOhm-cms and the density of the titanium nitride is less than about 4.25 grams per cubic cm; and patterning and etching the titanium nitride. [0019] Still another preferred embodiment provides for a monolithic three dimensional memory array comprising polysilicon; in contact with the polysilicon, a layer of silicon dioxide or silicon nitride; and in contact with the silicon dioxide or silicon nitride layer, a layer of titanium nitride, wherein the resistivity of the titanium nitride is greater than about 300 microOhm-cms and the density of the titanium nitride is less than about 4.25 grams per cubic cm. [0020] An aspect of the invention provides for a memory array comprising memory cells on a die, wherein the memory cells comprise diode portions and an antifuse, wherein the diode portions comprise doped polysilicon, and wherein median leakage current across the antifuse for the memory cells on the die is less than about 1.77.times.10.sup.-13 amps/.mu.m.sup.2. [0021] Another aspect of the invention provides for a semiconductor device comprising an antifuse; and a layer of low-density, high-resistivity material in contact with the antifuse, such that the leakage current across the antifuse in contact with the low-density, high-resistivity material is less than one-tenth the leakage current across an identical antifuse in contact with an analogous material when the analogous material is formed in the presence of self-bias or decreased pressure. Continue reading... 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