Texas Instruments Corporation

Bernard M Kulwicki

Robert Yung-Hsi Tsu

Scott Robert Summerfelt

Howard R Beratan

Thomas C Conlan

Peter G Berg

Vishwa N Shukla

Robert T McGovern

George Trenkler

Leo Marcoux

Stanley J Lukasiewicz

David C Hill

David F Lynch

Norman P StMartin

The invention described is a method of forming an improved dielectric material by adding lead to an original perovskite material having an original critical grain size to form a lead enhanced perovskite material, then forming a layer of the lead enhanced perovskite material having an average grain size less than the original critical grain size whereby the dielectric constant of the layer is substantially greater than the dielectric constant of the original perovskite material with an average grain size similar to the average grain size of the layer. The critical grain size, as used herein, means the largest grain size such that the dielectric constant starts to rapidly decrease with decreasing grain sizes. Preferably, the lead enhanced perovskite material is further doped with one or more acceptor dopants whereby the resistivity is substantially increased and/or the loss tangent is substantially decreased. Preferably, the original perovskite material has a chemical composition ABO , where A is one or more monovalent, divalent or trivalent elements, and B is one or more pentavalent, tetravalent, trivalent or divalent elements.

PB substituted perovskites for thin films dielectrics

A semiconductor device and process for making the same are disclosed which incorporate boron, which has been found to be substantially insoluble in BST, into a BST dielectric film,Dielectric film,is preferably disposed between electrodes,and,(which preferably have a Pt layer contacting the BST) to form a capacitive structure with a relatively high dielectric constant and relatively low leakage current. Boron included in a BST precursor may be used to form boron oxide in a second phase,which is distributed in boundary regions between BST crystals,in film,It is believed that the inclusion of boron allows for BST grains of a desired size to be formed at lower temperature, and also reduces the leakage current of the capacitive structure.

Barium strontium titanate (BST) thin films using boron

The invention forms improved ferroelectric (or pyroelectric) material by doping an intrinsic perovskite material having an intrinsic ferroelectric (or pyroelectric) critical grain size with one or more donor dopants, then forming a layer of the donor doped perovskite material having an average grain size less than the intrinsic ferroelectric (or pyroelectric) critical gran size whereby the remanent polarization (or pyroelectric figure of merit) of the layer is substantially greater than the remanent polarization (or pyroelectric figure of merit) of the intrinsic perovskite material with an average grain size similar to the average grain size of the layer. The critical ferroelectric (or pyroelectric) grain size, as used herein, means the largest grain size such that the remanent polarization (or pyroelectric figure of merit) starts to rapidly decrease with decreasing grain sizes. Preferably, the donor doped perovskite material is further doped with one or more acceptor dopants to form a donor acceptor doped perovskite material whereby the resistivity is substantially increased. Preferably, the intrinsic perovskite material has a chemical composition AB03, where A is one or more monovalent, divalent or trivalent elements, and B is one or more pentavalent, tetravalent, trivalent or divalent elements. Structures containing an improved ferroelectric (or pyroelectric) material include a layer of donor doped perovskite material with average grain size less than the intrinsic ferroelectric (or pyroelectric) critical grain size formed on the surface of a substrate. Other structures include such a layer of donor doped material interposed between two electrically conducting layers.

Donor doped perovskites for thin-film ferroelectric and pyroelectric

A semiconductor device and process for making the same are disclosed which incorporate a relatively large percentage of erbium dopant (1 to 5%) into a BST dielectric film 24 with small grain size (e.g. 10 nm to 50 nm). Dielectric film 24 is preferably disposed between electrodes 18 and 26 (which preferably have a Pt layer contacting the BST) to form a capacitive structure with a relatively high dielectric constant and relatively low leakage current. Apparently, properties of the thin film deposition and small grain size. including temperatures well below bulk BST sintering temperatures, allow the film to support markedly higher defect concentrations without erbium precipitation than are observed for bulk BST. For erbium doping levels generally between 1% and 3%, over an order of magnitude decrease in leakage current (compared to undoped BST) may be achieved for such films.

Method of making barium strontium titanate (BST) thin film by erbium

The invention described is an improved dielectric material formed as a film on the surface of a substrate by adding lead to an original perovskite material having an original critical grain size to form a lead enhanced perovskite material, then forming a layer of the lead enhanced perovskite material having an average grain size less than the original critical grain size whereby the dielectric constant of the layer is substantially greater than the dielectric constant of the original perovskite material with an average grain size similar to the average grain size of the layer. The critical grain size, as used herein, means the largest grain size such that the dielectric constant starts to rapidly decrease with decreasing grain sizes. Preferably, the lead enhanced perovskite material is further doped with one or more acceptor dopants whereby the resistivity is substantially increased and/or the loss tangent is substantially decreased. Preferably, the original perovskite material has a chemical composition ABO.sub.3, where A is one or more monovalent, divalent or trivalent elements, and B is one or more pentavalent, tetravalent, trivalent or divalent elements.

Method of forming improved thin film dielectrics by Pb doping

A semiconductor device and process for making the same are disclosed which incorporate a relatively large percentage of erbium dopant (1 to 5%) into a BST dielectric film 24 with small grain size (e.g. 10 nm to 50 nm). Dielectric film 24 is preferably disposed between electrodes 18 and 26 (which preferably have a Pt layer contacting the BST) to form a capacitive structure with a relatively high dielectric constant and relatively low leakage current. Apparently, properties of the thin film deposition and small grain size, including temperatures well below bulk BST sintering temperatures, allow the film to support markedly higher defect concentrations without erbium precipitation than are observed for bulk BST. For erbium doping levels generally between 1% and 3%, over an order of magnitude decrease in leakage current (compared to undoped BST) may be achieved for such films.

Barium strontium titanate (BST) thin films by erbium donor doping

A semiconductor device and process for making the same are disclosed which incorporate boron, which has been found to be substantially insoluble in BST, into a BST dielectric film 24. Dielectric film 24 is preferably disposed between electrodes 18 and 26 (which preferably have a Pt layer contacting the BST) to form a capacitive structure with a relatively high dielectric constant and relatively low leakage current. Boron included in a BST precursor may be used to form boron oxide in a second phase 30, which is distributed in boundary regions between BST crystals 28 in film 24. It is believed that the inclusion of boron allows for BST grains of a desired size to be formed at lower temperature, and also reduces the leakage current of the capacitive structure.

An improved dielectric material and microcircuit having capacitive elements which employ such a dielectric material are disclosed. The dielectric material comprises polycrystalline barium strontium titanate doped with at least one donor element and having a grain size of less than 1 micron. In the preferred embodiments, the donor element may be Nb, Ta, Bi, Sb, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er or a combination thereof. The material may be further doped with an acceptor dopant to control resistivity. The microcircuit comprises capacitors having such a dielectric material and connected to a semiconductor substrate which contains embedded circuitry for reading the voltage across a capacitor.

Microelectronic device with capacitors having fine-grain dielectric

The invention described forms improved ferroelectric (or pyroelectric) layer by adding lead to an original perovskite layer having an original ferroelectric (or pyroelectric) critical grain size, then forming a layer of the lead enhanced perovskite layer having an average grain size less than the original ferroelectric (or pyroelectric) critical grain size whereby the remanent polarization (or pyroelectric figure of merit) of the layer is substantially greater than the remanent polarization (or pyroelectric figure of merit) of the original perovskite layer with an average grain size similar to the average grain size of the layer. The critical ferroelectric (or pyroelectric) grain size, as used herein, means the largest grain size such that the remanent polarization (or pyroelectric figure of merit) starts to rapidly decrease with decreasing grain sizes. Preferably, n-type lead enhanced perovskite layer is doped with one or more acceptor dopants whereby the resistivity is substantially increased. Preferably, p-type lead enhanced perovskite layer is doped with one or more donor dopants whereby the resistivity is substantially increased. Preferably, the original perovskite layer has a chemical composition ABO.sub.3, where A is one or more monovalent, divalent or trivalent elements, and B is one or more pentavalent, tetravalent, trivalent or divalent elements. Structures containing an improved ferroelectric (or pyroelectric) layer include a layer of lead enhanced perovskite layer with average grain size less than the original ferroelectric (or pyroelectric) critical grain size formed on the surface of a substrate. Other structures include such a layer of lead enhanced layer interposed between two electrically conducting layers.

Lead substitured perovskites for thin-film pyroelectric devices

A semiconductor device and process for making the same are disclosed which incorporate a relatively large percentage of holmium dopant (0.5 to 5%) into a BST dielectric film 24 with small grain size (e.g. 10 nm to 50 nm). Dielectric film 24 is preferably disposed between electrodes 18 and 26 (which preferably have a Pt layer contacting the BST) to form a capacitive structure with a relatively high dielectric constant and relatively low leakage current. Apparently, properties of the thin film deposition and small grain size, including temperatures well below bulk BST sintering temperatures, allow the film to support markedly higher defect concentrations without holmium precipitation than are observed for bulk BST. For holmium doping levels generally between 0.5 and 5% (compensated with titanium and/or manganese), better than 50% improvement in dielectric constant and two to six orders of magnitude reduction in leakage current (compared to undoped BST) have been observed for such films.

Barium strontium titanate (BST) thin films by holmium donor doping

An improved pyroelectric material comprises a polycrystalline material doped with at least one donor element such that the polycrystalline material has a grain size less than 10 .mu.m (or 5 .mu.m) and a Figure of Merit greater than 90 nC/(cm.sup.2* K). In the preferred embodiments the polycrystalline material is barium strontium titanate or calcium-substituted barium strontium titanate. The donor element may be Nb, Ta, Bi, Sb, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er or a combination thereof. The material may additionally be doped with an accepter such as Co, Cu, Fe, Mn, Ru, Al, Ga, Mg, Sc, K, Na, U, In, Mg, Ni, Yb or a combination thereof to control the resistivity. Other structures and methods are also disclosed.

Fine-grain pyroelectric detector material and method

Titanate ceramic materials are made by forming a common solution (10) of barium acetate, strontium acetate, isopropyl titanate, lactic acid and water, forming a mist of particles of approximately 50 um or smaller, directing a carrier stream of gas (14) through the mist into a reaction zone in a furnace (20) where the material is pyrolyzed and then collected as a powder in a filter (24) or deposited onto a substrate. The tetra-isopropyl titanate and lactic acid may be replaced by commercially available titanium ammonium lactate. In a first embodiment the carrier gas is an oxidizing gas while in a second embodiment it is an inert gas resulting in powder having greater density.

Method for producing titanate powder and product made thereby

An improved pyroelectric material comprises a polycrystalline material doped with at least one donor element such that the polycrystalline material has a grain size less than 10 .mu.m (or 5 .mu.m) and a Figure of Merit greater than 90 nC/(cm.sup.2.K). In the preferred embodiments the polycrystalline material is barium strontium titanate or calcium-substituted barium strontium titanate. The donor element may be Nb, Ta, Bi, Sb, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er or a combination thereof. The material may additionally be doped with an acceptor such as Co, Cu, Fe, Mn, Ru, Al, Ga, Mg, Sc, K, Na, U, In, Mg, Ni, Yb or a combination thereof to control the resistivity. Other structures and methods are also disclosed.

A humidity sensor composed of interdigitated electrodes and a material therebetween which is composed of Nafion wherein H+ cites have undergone ion exchange with at least one of NH4+ and Li+, Na+, Ag+ and Mg+.

Fluoropolymer humidity sensors

A humidity sensor composed of interdigitated electrodes and a material therebetween which is composed of perfluorosulfonic acid substituted poly (tetrafluoroethylene) copolymer wherein H+ sites have undergone ion exchange with at least one of NH4+ and Li+, Na+, Ag+ and Mg+.

Growing community of inventors

North Attleboro, MA, United States of America

Bernard M Kulwicki