International Business Machines Corporation

Joseph F Shepard

Louis L Hsu

Seiki Ogura

Nivo Rovedo

Martin Revitz

Paul L Garbarino

James R Gardiner

Stanley R Makarewicz

Joyce E Acocella

Carol Galli

Toshio Mii

Jacob Riseman

Paul J Tsang

Michael Daniel Monkowski

Taqi Nasser Buti

William A Pliskin

Rajiv V Joshi

Manu J Tejwani

Scott R Stiffler

Mary Joseph Saccamango

George A Kaplita

Edward J Vishnesky

Nicholas J Giammarco

Anthony F Scaduto

Alexander D Lopata

Alexander Gimpelson

Dominic Joseph Schepis

Jack Oon Chu

Louis Lu-Chen Hsu

Chang-Ming Hsieh

Joseph John Fatula, Jr

Robert K Cook

Sieki Ogura

Jack C Chu

Robert F Bartholomew

An integrated circuit using high-performance bipolar and CMOS transistor elements on a single chip is fabricated by a simplified process requiring minimal, if any, changes in the process used for forming either type of device in accordance with a variety of possible device designs. The method according to the invention makes maximal use of self-aligned and self-masking processes to reduce the number of processing steps. The number of processing steps is further reduced by performing some steps concurrently on different device types. Further, the masking steps which are employed are reasonably misregistration tolerant, resulting in high manufacturing yield for the process. Consequently, the process according to the invention substantially eliminates the existence of trade-offs between element performance, integration density and process complexity and cost when plural technologies are integrated on the same chip.

High performance/high density BICMOS process

Improved packing density as well as improved performance and manufacturing yield is achieved in an electrically programmable memory by confining floating gate structures between isolation structures covered with a thin nitride layer. The confinement of the floating gate is achieved by planarization, preferably with a self-limiting chemical/mechanical polishing process, to the surface of the nitride layer covering the isolation structures. Gate oxide and control electrode connections can then be formed on a substantially planar surface without compromising the quality of the gate oxide or breakdown voltage the device must withstand for programming. Since severe topology is avoided over which these connections are formed, improved formation of low resistance connections, possibly including metal connections, are possible and allow scaling of transistors of the memory cells to be scaled to sizes not previously possible.

Packing density for flash memories

A method for forming trench isolation and in specific shallow trench isolation(STI) using SiO.sub.2 plugs is proposed. The SiO.sub.2 plugs of the STI have a buried phosphorus (P) rich layer introduced during and subsequent to the trench formation to tie up any sodium ionic contamination from processes prior to gate formation. P impurity layer is formed below the surface of the deposited SiO.sub.2 layer. A preferred method for forming the buried P layer is by shallow implantation in a vertical direction into the deposited SiO.sub.2 layer prior to planarization. The process is self aligned to the trench isolation regions.

Shallow trench isolation with self aligned PSG layer

A simple method of making a thin film transistor (TFT) on a substrate with an insulating surface layer is disclosed. A layer of dopant source layer is deposited on the insulating layer, followed by defining a gate stack consisting of a gate polysilicon, gate insulator and a protective polysilicon using the dopant source layer as an etch stop. Sidewall spacers are formed in contact with the gate stack. A TFT body polysilicon is deposited and patterned, forming thereby the source and drain regions in a self-aligned manner. By heating, the dopants from the dopant source layer are driven into the source/drain and to part of the off-set regions of the body polysilicon layer while simultaneously also doping the gate polysilicon.

Thin film transistor with self-aligned bottom gate

A method of gettering an SOI wafer from the front side of the wafer includes depositing a gettering layer, such as polysilicon, on the SOI layer and annealing the SOI wafer with the gettering layer in place. A polish stop structure, which can be deposited before or after the gettering layer, provides a means for selectively removing the gettering layer from the SOI wafer without damaging the surface or eroding the thickness of the SOI layer.

Method and structure for front-side gettering of silicon-on-insulator

Packing density for flash memories by using a pad oxide

Method of making thin film transistor with a self-aligned bottom gate

A process for making a dual gated thin film transistor (TFT), having a sidewall channel and self-aligned gates and off-set drain is disclosed. A substrate having a top surface with insulating regions is provided. A bilayer having a polysilicon bottom layer and an insulating top layer, is patterned to form the bottom electrode of the TFT with an insulating layer over it. A first gate insulator is formed in contact with sides of the bottom electrode. A layer of second polysilicon having two end source and drain regions and a middle channel region is formed with the channel region being vertical along the side of the bottom electrode and overlying insulator layer and in contact with the first gate insulator. A second gate insulator is formed on the second polysilicon. A contact opening is etched in the insulating layers overlying the bottom electrode, in a region away from the second polysilicon to expose surface of part of the bottom electrode. A third polysilicon layer is deposited and patterned to have a horizontal region overlapping the contact opening to make contact to the bottom electrode, and to have sidewall electrode regions in contact with the second gate insulator and superadjacent to the channel region act as the top electrode of the TFT. The sidewall spacer electrode regions are connected to the horizontal regions of the third polysilicon. Thus the top and bottom electrode are also electrically connected together. The source and drain regions are doped selectively. By choice of implant conditions, the off-set region having a desired dopant concentration different from the device layer concentration, can be formed at the drain side of the dual gated TFT.

Vertical dual gate thin film transistor with self-aligned gates / offset

A shallow trench isolation structure is formed by a process having a reduced number of steps and thermal budget by filling trenches by liquid phase deposition of an insulating semiconductor oxide and heat treating the deposit to form a layer of high quality thermal oxide at an interface between the deposited oxide and the body of semiconductor material (e.g. substrate) into which the trench extends. This process yields an isolation structure with reduced stress and reduced tendency to develop charge leakage. The structure can be readily and easily planarized, particularly if a polish-stop layer is applied over the body of semiconductor material and voids and contamination of the deposited oxide are substantially eliminated by self-aligned deposition above the trench in the volume of apertures on a resist used to form the trench.

Isolation structure using liquid phase oxide deposition

A DRAM cell of the trench capacitor type is formed by a simplified process that reduces cost and increases process latitude by forming the trench collar in a single step of expanding a shallow trench horizontally and conformally coating the collar; etching the trench to its final depth and implanting the bottom heavily and doping the walls lightly; recessing the poly liner in a non-critical step that exposes a contact area between the top of the poly and the adjacent transistor electrode.

Method of making a DRAM cell with trench capacitor

A trench capacitor DRAM cell with Shallow Trench Isolation (STI), a self-aligned buried strap and the method of making the cell. A trench capacitor is defined in a substrate. The trench capacitor's polysilicon (poly) plate is recessed below the surface of the substrate and the trench sidewalls are exposed above the poly. A doped poly layer is deposited over the surface contacting both the sidewall and the trench capacitor's poly plate. Horizontal portions of the poly layer are removed either through chemmech polishing or Reactive Ion Etching (RIE). A shallow trench is formed, removing one formerly exposed trench sidewall and a portion of the trench capacitor's poly plate in order to isolate the DRAM cell from adjacent cells. The remaining poly strap, along the trench sidewall contacting the poly plate, is self aligned to contact the source of the DRAM Pass gate Field Effect Transistor (FET). After the shallow trench is filled with oxide, FET's are formed on the substrate, completing the cell. In an alternate embodiment, instead of recessing the poly plate, a shallow trench is formed spanning the entire width of the trench capacitor. The deposited polysilicon is selectively removed, having straps that strap the poly plate to the shallow trench sidewall.

Method of forming integrated interconnect for very high density DRAMs

A method of forming a MOS DRAM cell having a trench capacitor in which the strap connection to the trench capacitor, the source, drain, and isolation are all raised above the surface of the single crystal silicon includes the steps of forming the trench capacitors, depositing a blanket gate stack including the gate oxide and a set of gate layers, and then depositing isolation members in apertures etched in the gate stack using the gate oxide as an etch stop. The same sidewalls that are used to form an LDD source and drain combine with nitride sidewalls on a gate contact aperture to separate a gate contact from source and drain contacts.

Method for forming a DRAM trench cell capacitor having a strap connection

A capacitor is provided having a substrate and a first capacitor plate including a lattice mismatched crystalline material is formed over and supported by a surface of the substrate. A layer of insulating material is formed over and supported by the first capacitor plate. A second capacitor plate including a layer of conductive material is formed over and supported by the layer of insulating material.

Method for forming capacitors with roughened single crystal plates

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Hopewell Junction, NY, United States of America

Joseph F Shepard