International Business Machines Corporation

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International Business Corporation

Donald M Kenney

Chung H Lam

John Edward Cronin

Son Van Nguyen

Michael D Armacost

David L Harmon

Claude Louis Bertin

Howard L Kalter

Thomas John Licata

Hsing-San Lee

Albert Stephan Bergendahl

Richard R Garnache

Tue H Nguyen

Pai-Hung Pan

James Spiros Nakos

David M Dobuzinsky

Peter John Geiss

Eric Adler

Steven Alfred Grundon

Walter E Mlynko

Wayne S Berry

Michael L Kerbaugh

Srinandan R Kasi

Daniel A Carl

Daniel Arthur Carl

A Richard Baker, Jr

Jack Allan Mandelman

John Kenneth DeBrosse

Gary Bela Bronner

Stephen Ellinwood Luce

Paul Christian Parries

James Gardner Ryan

Howard Smith Landis

William J Cote

Rosemary A Previti-Kelly

Carter W Kaanta

Nandor G Thoma

Brian J Machesney

Michael A Leach

John F Rembetski

John K Debrosse

Jeffrey A Robinson

Julian Juu-Chuan Hsieh

Robert W Sweetser

A post-etch structure resulting in the inverse of a sidewall spacer etch, i.e. removal of the spacer. A vertical portion of a film is removed while leaving horizontal portions substantially intact. A facet is left in the film in register with an upper corner formed by the vertical and horizontal portions of the underlying body.

Selective removal of vertical portions of a film

Chips having subsurface structures within or adjacent a horizontal trench in bulk single crystal semiconductor are presented. Structures include three terminal devices, such as FETs and bipolar transistors, rectifying contacts, such as pn diodes and Schottky diodes, capacitors, and contacts to and connectors between devices. FETs have low resistance connectors to diffusions while retaining low overlap capacitance. A low resistance and low capacitance contact to subsurface electrodes is achieved by using highly conductive subsurface connectors which may be isolated by low dielectric insulator. Stacks of devices are formed simultaneously within bulk single crystal semiconductor. A subsurface CMOS invertor is described. A process for forming a horizontal trench exclusively in heavily doped p+ regions is presented in which porous silicon is first formed in the p+ regions and then the porous silicon is etched.

Stacked devices

A stacked capacitor having very thin fins and subminimum dimension supports for the fins is described. The capacitor includes a stack of conductive layers on a substrate. A plurality of subminimum dimension trenches are formed in the stack and a columnar conductive layer lines the trenches in contact with alternate layers of the stack. An insulator lines these alternate layers and the columnar conductive layer and capacitively couples these alternate layers and the columnar conductive layer to a second plate layer that is formed between the alternate layers, within the columnar layers in the trenches, and extending between stacked capacitors.

Mechanical supports for very thin stacked capacitor plates

An apparatus and method provide deposition on a surface by angled sputtering using a collimation grid having angled vanes which limit the distribution of trajectories of particles in at least one coordinate direction around a central axis oriented at an angle of less than 90.degree. to said surface; resulting in improved uniformity of deposition and/or selective favoring of deposition on surfaces at a high angle to the deposition surface (e.g. sidewalls). Substantially parallel orientation and uniform spacing of the sputtering target and deposition surface provides good uniformity of results over the deposition surface. The angled trajectories of sputtered particles provides improved deposition on sides of upstanding mandrel features and filling of recessed features of high aspect ratio, especially when the collimation grid is rotated about an axis generally perpendicular to the deposition surface. Angled, collimated deposition also allows for control of deposition at potentially sub-lithographic feature sizes by using portions of features as a mask with deposition being performed only on remaining exposed portions of features or deposition on selected sides of a mandrel feature. Sidewall image transfer techniques may thus be extended to non-symmetrical and singular features. At very shallow angles to the deposition surface, deposited material has a fibrous texture with greatly increased effective surface area.

Method for selective material deposition on one side of raised or

A method of forming recesses in a substrate such as a capacitor so as to increase the surface area thereof and therefore the charge storage capacity of the capacitor. This is accomplished by utilizing a micro mask formed by agglomeration on the surface of the substrate. The agglomerated material, such as gold, titanium nitride or titanium silicide, is used as a mask for selectively etching the substrate to form recesses therein. Alternatively, an oxide transfer mask can be utilized with the agglomerated material micro mask to etch the substrate.

Micro mask comprising agglomerated material

A body is provided with a substantially horizontal surface and a substantially vertical surface. A film is formed on the body with a substantially horizontal portion on the substantially horizontal surface, a substantially vertical portion on the substantially vertical surface, and a corner region joining the substantially horizontal and substantially vertical portions. The corner region and the substantially vertical portion of the film are removed while the body and the substantially horizontal portion of the film are left substantially intact. A high density plasma with a fluorocarbon-based etching gas may be used to remove the vertical portion and corner region.

Vertical epitaxial SOI transistors and memory cells are disclosed. The devices are formed completely within a substrate trench and have a bulk channel epitaxially grown on an exposed surface of the substrate within the trench. The bulk channel is disposed proximate to a transistor gate electrode such that an inversion layer is formed therein when the gate electrode is appropriately biased. Back biasing of the bulk region is accomplished through the substrate. In the transistor embodiment, a first node diffusion and a second node diffusion are disposed at opposite ends of the bulk channel. In a memory cell configuration the access transistor is disposed above a trench storage node, which electrically connects with the transistor's second node diffusion. Arrays of the trench transistors and trench memory cells are also described. Further, fabrication methods for the various structures disclosed are presented. A novel wiring approach to construction of bit lines in a cell array is also set forth.

Method of fabricating a memory cell in a substrate trench

A semiconductor trench capacitor structure having a first level aligned isolation structure and buried strap that extends from within the trench into the doped semiconductor substrate. The semiconductor trench capacitor structure may be fabricated by forming a shallow trench within the trench capacitor and semiconductor substrate, depositing a layer of conductive material within the shallow trench, using a mask to define and recess the strap and depositing insulating material within the shallow trench.

Semiconductor trench capacitor cell having a buried strap

A first region of a seed substrate is separated from a bonded handle substrate by etching and/or fracturing a second region of the seed substrate. A third region of the seed substrate remains bonded to the handle wafer. Etching and etch ant distribution are facilitated by capillary action in trenches formed in the seed substrate prior to bonding of the handle substrate. A portion of the second region may be removed by undercut etching prior to handle bonding. Elevated pressure and etchant composition are used to suppress bubble formation during etching. Alternatively, pressure from bubble formation is used to fracture a portion of the second region. First, second, and third regions are defined by a variety of methods.

SOI fabrication method

The present invention is a sidewall connector providing a conductive path linking at least two conductive regions. The sidewall connector has a top portion comprising surface. A conductive member contacts the top portion, connecting the rail to a conductive region or to an external conductor. An etch stop layer located on a conductive region can be used to protect the conductive region during the directional etch to form the sidewall connector. A conductive bridge is then used to link exposed portions of the conductive region and the conductive sidewall rail, the conductive bridge extending across the thickness of the etch stop layer. A 'T' connector is formed by the process, starting with a pair of intersecting sidewalls wherein the two sidewalls have top edges at different heights where they intersect. The connector is used to form a strap for a DRAM cell.

Sidewall strap

An integrated structure is provided that includes a DRAM cell with a trench storage capacitor, and a corresponding storage node precharge circuit. The entire structure ideally requires only eight square features of area per memory bit. The structure also provides a partial leakage current shield for the DRAM storage node diffusion, thereby improving the data hold time. A graded impurity region around the storage node diffusion enhances the leakage shielding effect. The structure can be operated independently as a DRAM leakage shield if the precharge circuit is not needed. In that case, a junction diffusion in the structure can be eliminated and a leakage shielding effect is still achieved.

Trench capacitor precharge structure and leakage shield

A DRAM one device cell and an associated precharge circuit are integrated together in a novel structure having an area of only four square features. The structure also provides physical and electrical separation between adjacent cells along a direction parallel to the DRAM word lines. The DRAM bit line length per bit is reduced by 50% relative to a conventional planar integrated structure disclosed elsewhere. As a result, bit line capacitance is also substantially reduced, and the effectiveness of a precharge technique for reduction of DRAM power consumption is enhanced by the dense novel structure.

Vertical precharge structure for DRAM

Polysilicon (20) in a trench (21) is etched at an angle to produce a conductor within the trench that has shape characteristics which approximate the shadow of the side wall (26) of the trench (21) closest the beam source. Specifically, when the first side wall (26) is closest the beam source and the second side wall (27) is furthest from the beam source, the polysilicon on the first side wall (26) is almost as high as the first side wall (26), while the polysilicon on the more exposed side wall (27) is considerably lower than the first side wall (26) and approximates the shadow of the first side wall (26) on the second side wall (27) relative to the beam. The polysilicon (20) in the trench (21) may be in the shape of a solid angled block approximating the shadow line from the top of side wall (26) to side wall (27); however, it is preferred that the polysilicon take the form of a conformal layer in trench (21) prior to etching such that the polysilicon ultimately has an angled 'U' shape which approximates the shadow line. Contact is made to the polysilicon (20) using strap (23) that electrically connects the side wall (26) with the polysilicon (20). Strap (23) is sized such that it does not extend to the opposite side wall (27) of trench (21), thereby avoiding short circuits. Having the polysilicon (20) approximate the shadow line of the etch permits narrowing the distance between adjacent straps (23) and (24) in an array without the risk of creating a short circuit.

Method for preparing a narrow angle defined trench in a substrate

A semiconductor device memory array formed on a semiconductor substrate comprising a multiplicity of field effect transistor DRAM devices disposed in array is disclosed. Each of the DRAM devices is paired with a non-volatile EEPROM cell and the EEPROM cells are disposed in a shallow trench in the semiconductor substrate running between the DRAM devices such that each DRAM-EEPROM pair shares a common drain diffusion. The EEPROM cells are arranged in the trench such that there are discontinuous laterally disposed floating gate polysilicon electrodes and continuous horizontally disposed program and recall gate polysilicon electrodes. The floating gate is separated from the program and recall gates by a silicon rich nitride. The array of the invention provides high density shadow RAMs. Also disclosed are methods for the fabrication of devices of the invention.

Process for forming a polysilicon electrode in a trench

Method of fabricating vertical epitaxial SOI transistor

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Shelburne, VT, United States of America

Donald M Kenney