International Business Machines Corporation

International Business Machines Coirporation

Paul A Rabidoux

Steven J Holmes

David V Horak

Mark Charles Hakey

Toshiharu Furukawa

Ahmad D Katnani

Niranjan Mohanlal Patel

Jack Allan Mandelman

Wu-Song S Huang

Gary Bela Bronner

Howard L Kalter

William H Ma

Kuang-Jung Chen

James Marc Leas

Diane Catherine Boyd

Jeffrey John Welser

William H-l Ma

James Spiros Nakos

Michael Straight Hibbs

Orest Bula

Steve J Holmes

Stevn J Holmes

A method of manufacturing provides a vertical transistor particularly suitable for high density integration and which includes potentially independent gate structures on opposite sides of a semiconductor pillar formed by etching or epitaxial growth in a trench. The gate structure is surrounded by insulating material which is selectively etchable to isolation material surrounding the transistor. A contact is made to the lower end of the pillar (e.g. the transistor drain) by selectively etching the isolation material selective to the insulating material. The upper end of the pillar is covered by a cap and sidewalls of selectively etchable materials so that gate and source connection openings can also be made by selective etching with good registration tolerance. A dimension of the pillar in a direction parallel to the chip surface is defined by a distance between isolation regions and selective etching and height of the pillar is defined by thickness of a sacrificial layer.

Vertical dual gate field effect transistor

A method for forming a trimmed gate in a transistor comprises the steps of forming a polysilicon gate conductor on a semiconductor substrate and trimming the polysilicon portion by a film growth method chosen from among selective surface oxidation and selective surface nitridation. The trimming step may selectively compensate n-channel and p-channel devices. Also, the trimming film may optionally be removed by a method chosen from among anisotropic and isotropic etching. Further, gate conductor spacers may be formed by anisotropic etching of the grown film. The resulting transistor may comprise a trimmed polysilicon portion of a gate conductor, wherein the trimming occurred by a film growth method chosen from among selective surface oxidation and selective surface nitridation.

Method for selective trimming of gate structures and apparatus formed thereby

A vertical transistor particularly suitable for high density integration includes potentially independent gate structures on opposite sides of a semiconductor pillar formed by etching or epitaxial growth in a trench. The gate structure is surrounded by insulating material which is selectively etchable to isolation material surrounding the transistor. A contact is made to the lower end of the pillar (e.g. the transistor drain) by selectively etching the isolation material selective to the insulating material. The upper end of the pillar is covered by a cap and sidewalls of selectively etchable materials so that gate and source connection openings can also be made by selective etching with good registration tolerance. A dimension of the pillar in a direction parallel to the chip surface is defined by a distance between isolation regions and selective etching and height of the pillar is defined by thickness of a sacrificial layer.

An assist feature is formed on a lithographic reticle or mask using a hybrid resist and an exposure dose such that only an annular area is effectively exposed having a width that is potentially less than the minimum feature size that can be resolved by the mask exposure tool to simultaneously or sequentially form both a feature of interest and an assist feature for enhancing imaging of the feature of interest when the feature is printed to a wafer. Since the assist feature can be imaged simultaneously with the feature of interest or multiple assist features imaged concurrently, possibly between closely spaced features, data volume and mask writing time are greatly reduced. The invention is particularly applicable to the scaling of contact holes for connections to active devices in extremely high density integrated circuits.

Assist features for contact hole mask patterns

A method for forming a gate conductor cap in a transistor comprises the steps of: a) forming a polysilicon gate conductor; b) doping the polysilicon gate; c) doping diffusion areas; and d) capping the gate conductor by a nitridation method chosen from among selective nitride deposition and selective surface nitridation. The resulting transistor may comprise a capped gate conductor and borderless diffusion contacts, wherein the capping occurred by a nitridation method chosen from among selective nitride deposition and selective surface nitridation and wherein a portion of the gate conductor is masked during the nitridation method to leave open a contact area for a local interconnect or a gate contact.

Borderless gate structures

A photoresist having both positive and negative tone components resulting in a lower &ldquo;k&rdquo; factor than the single tone photoresist is disclosed. The hybrid resist may either have the negative tone resist or the positive tone resist as the major portion, while the other tone is a relatively minor portion. For examples, a positive tone resist may include a minor portion of a negative tone cross-linker or a negative tone resist may include positively acting functional groups. The hybrid resist of the present invention allows for wider exposure dosage windows, therefore increasing the yield or performance and line density.

Low &ldquo;K&rdquo; factor hybrid photoresist

A densely packed array of vertical semiconductor devices having pillars and methods of making thereof are disclosed. The array has rows of wordlines and columns of bitlines. The array has vertical pillars, each having two wordlines, one active and the other passing for each, cell. Two wordlines are formed per pillar on opposite pillar sidewalls which are along the row direction. The threshold voltage of the pillar device is raised on the side of the pillar touching the passing wordline, thereby permanently shutting off the pillar device during the cell operation and isolating the pillar from the voltage variations on the passing wordline. The isolated wordlines allow individual cells to be addressed and written via direct tunneling, in both volatile and non-volatile memory cell configurations. For Gbit DRAM application, stack or trench capacitors may be formed on the pillars, or in trenches surrounding the pillars, respectively.

Structure for folded architecture pillar memory cell

The present invention lengthens gate conductors used in memory chips to limit leakage current, while still allowing the overall size of cells to remain the same. The channel length for each gate is increased by decreasing the size of spaces between gates. Decreases in space size occurs by using photolithographic image enhancement techniques. These techniques allow the space between gate conductors to be smaller while the gate size increases. In addition, a groove may be added that additionally lengthens the effective channel length and provides an additional electrical shield to limit leakage current. These techniques lead to the same density memory cells for a given process with less leakage. Finally, if grooved gate structures are used, having a longer gate conductor allows a three sigma process to be used, which increases yields.

Fabrication of a high density long channel DRAM gate with or without a grooved gate

Methods for forming a T-gate on a substrate are provided that employ a hybrid resist. The hybrid resist specifically is employed to define a base of the T-gate on the substrate with very high resolution. To define a base of the T-gate, a hybrid resist layer is deposited on the substrate. A mask having a reticle feature with an edge is provided and is positioned above the hybrid resist layer so that the edge of the reticle feature is above a desired location for the base of the T-gate. Thereafter, the hybrid resist layer is exposed to radiation through the mask, and the exposed hybrid resist layer is developed to define an opening therein for the base of the T-gate. Preferably the loop feature formed in the hybrid resist layer by the reticle feature during exposure is trimmed. The T-gate may be completed by employing any known T-gate fabrication techniques.

Methods of T-gate fabrication using a hybrid resist

A photoresist composition is disclosed having both negative tone and positive tone responses, giving rise to spaces being formed in the areas of diffraction which are exposed to intermediate amounts of radiation energy. This resist material may be used to print doughnut shapes or may be subjected to a second masking step, to print lines. Additionally, larger and smaller features may be obtained using a gray-scale filter in the reticle, to create larger areas of intermediate exposure areas.

Method of producing an integrated circuit chip using frequency doubling hybrid photoresist and apparatus formed thereby

A photo resist composition contains a polymer resin, a first photo acid generator (PAG) requiring a first dose of actinic energy to generate a first photo acid, and a photo base generator (PBG) requiring a second dose of actinic energy, different from the first dose, to generate a photo base. The amounts and types of components in the photo resist are selected to produce a hybrid resist image. Either the first photo acid or photo base acts as a catalyst for a chemical transformation in the resist to induce a solubility change. The other compound is formulated in material type and loading in the resist such that it acts as a quenching agent. The catalyst is formed at low doses to induce the solubility change and the quenching agent is formed at higher doses to counterbalance the presence of the catalyst. Accordingly, the same frequency doubling effect of conventional hybrid resist compositions may be obtained, however, either a line or a space may be formed at the edge of an aerial image. Feature size may also be influenced by incorporating a quenching agent into the resist composition that does not require photo generation.

Hybrid resist based on photo acid/photo base blending

A composition used to form an acid sensitive antireflective coating (ARC) includes a water soluble resin and a cross-linker. Radiation adsorptive components may be provided as part of the resin or, more preferably, as a separate dye. Being acid sensitive, selected portions of an ARC formed from the composition may be removed by a suitable reversal of the cross-linking followed by a develop step, preferably with an aqueous developer, more preferably de-ionized water. The water soluble resin is preferably hydroxystyrene-sulfonated styrene copolymer, poly(2-isopropenyl-2-oxazoline), or poly(acrylic acid), the cross-inker is preferably an acetal diacid or a water soluble divinyl ether, and the dye is preferably 9-anthracene methanol or a squaric acid derivative.

Acid sensitive ARC and method of use

Integrated circuit chip produced by using frequency doubling hybrid photoresist

A method for forming contacts on an integrated circuit that are self-aligned with the wiring patterns of the integrated circuit. In the method a thicker lower layer of a first material and a thinner upper layer of a second material are formed on a substrate. The features of the metal wiring is patterned first on the upper layer. The wiring pattern trenches are etched through the thinner surface layer, and partially through the second, thicker layer. After the wiring pattern is etched, the contacts for the wiring layer are printed as line/space patterns which intersect the wiring pattern. The contact pattern is etched into the lower, thicker layer with an etch process that is selective to the upper thinner layer. The contact is only formed at the intersection point of the wiring image with the contact image, therefore the contact is self-aligned to the metal.

Growing community of inventors

Winooski, VT, United States of America

Paul A Rabidoux