Intel Corporation

Other

Been-Jon K Woo

Mark A Holler

Sandra S Lee

Albert Fazio

Yudong Kim

Ender Hokelek

Gregory E Atwood

Stefan K Lai

Tong-Chern Ong

Max Wei

T C Ong

Ender Hokeler

Wei-Jen Lo

In general, in one aspect, a method includes forming a spacer layer over a substrate having patterned stacks formed therein and trenches between the patterned stacks. A sacrificial polysilicon layer is deposited over the substrate to fill the trenches. A patterning layer is deposited over the substrate and patterned to define contact regions over at least a portion of the trenches. The sacrificial polysilicon layer is etched using the patterned patterning layer to form open regions.

Self-aligned contact formation utilizing sacrificial polysilicon

According to an embodiment of the invention, a flash memory cell includes a first gate stack and a second gate stack having a film deposited across the gap between the first and second gate stacks so that the film creates a void between the first and second gate stacks. Dielectric materials may be used to reduce conductivity between the two stacks. A dielectric material that is resistant to conductivity has a low dielectric constant (k). The lowest-k dielectric material is air, which has a dielectric constant of approximately 1. By creating a void between the two gate stacks, the least conductive material (air) is left filling the space between the gate stacks, and the likelihood of parasitic coupling of two adjacent floating gates is substantially reduced.

Flash memory cell having reduced floating gate to floating gate coupling

A process for fabricating contactless electrically programmable and electrically erasable memory cells of the flash contactless EPROM or EEPROM type. The array of memory cells in these devices have elongated, parallel source and drain regions disposed beneath field oxide regions. The word lines are elongated, parallel strips of polysilicon. A series of SiO.sub.2 depositions using TEOS chemistry in a PECVD process, and etches using sputter etch and plasma processes, is performed. After deposition and etchback, the polysilicon word lines remain exposed while all previous exposed substrate regions between source and drain are covered with SiO.sub.2. A metal deposition and silicidation are performed forming a silicide on the exposed silicon word lines thereby lowering the resistance of the word lines. Since the substrate regions between source and drain is covered between SiO.sub.2 prior to metal deposition and silicidation no silicide is formed in these regions. Therefore the word lines are silicidized in a self aligned process with no need for a photolithographic step after SiO.sub.2 deposition.

Silicidation method for contactless EPROM related devices

A process for fabricating floating gates for electrically programmable and electrically erasable memory cells of the flash EPROM or EEPROM type. The floating gates are a three layer structure. The first layer of the floating gate is a thin polysilicon layer of approximately 300-500 .ANG. thickness. The second layer is a silicon dioxide layer of approximately 20-30 .ANG.. The third layer is polysilicon of approximately 1000-1500 .ANG. thickness. The third layer is doped by implantation of phosphorous. This dopant is driven through the oxide layer to dope the first, thin polysilicon layer in a separate diffusion step or in subsequent high temperature processing. The grain size of the first, thin polysilicon layer is small and uniform from gate to gate due to the thinness of this layer and its light doping. This reduces variations in threshold voltage from gate to gate due to variable polysilicon grain size and orientation. This in turn results in improved yield and cycling endurance.

Erase performance improvement via dual floating gate processing

A process for fabricating an electrically programmable read-only memory array having increased density includes forming recessed field oxide regions in a silicon substrate. Elongated parallel wordline stacks are then formed over the surface of the substrate. Source and drain regions are formed by ion implantation in the openings between these vertical stacks. These openings are then filled with a metal layer until the wafer is substantially planar. This metal layer is then patterned to form drain contact pads and V.sub.SS interconnect strips. The V.sub.SS interconnect strips contact adjacent source regions across field oxide regions that insulate adjacent memory cells.

Process for fabricating a flash EPROM having reduced cell size

A method for making a device and the device itself which utilizes selectively doping part of the channel directly adjacent to the source to improve source-channel junction breakdown voltage is disclosed. This is accomplished through reduced dopant incorporation in the channel directly adjacent to the source during the channel doping steps. The portion of the channel which receives less channel dopant should not be so great that the charging of the floating gate is significantly altered.

Method of making source junction breakdown for devices with source-side

A process for fabricating contactless electrically programmable and electrically erasable memory cells of the flash EPROM type. The cells use elongated source and drain regions disposed beneath field oxide regions. A high quality tunnel oxide is grown on the channel regions of the device, followed by deposition of a polysilicon buffer layer. The use of the polysilicon buffer layer results in short reoxidation beaks. The field oxide is grown in a short, low temperature wet oxidation step, enhanced by the presence of heavy dopant implants. The use of a short, low temperatue oxide growth allows the use of thin nitride masking members and results in short reoxidation beaks as well as less stress on the substrate during field oxide growth. Also, since a low temperature field oxidation is used, the quality of the tunnel oxide will be maintained. The thin nitride masking members are removed in a wet etch process which does not degrade the underlying polysilicon buffer layer. Therefore, the polysilicon buffer layer does not need to be removed and remains as part of the device. Since the polysilicon buffer layer is not removed, there is no damage to the underlying tunnel oxide, and this layer remains on the device as well. Because these layers remain after field oxide growth, there is no tunnel oxide growth subsequent to the field oxide growth as with prior art processes. Therefore, the reoxidation beak does not continue to grow during tunnel oxide growth as occurs with prior art processes where the tunnel oxide is grown after field oxide growth. Also, the dopant implanted regions are subjected to fewer thermal cycles than in prior art processes, resulting in shallower junctions. In addition, since the tunnel oxide is grown before the implantation of dopants, the quality of this layer is better than conventional tunnel oxides grown in the presence of dopant. The short reoxidation beak, reduced thermal cycles and better tunnel oxide quality of the present invention results in a greater effective channel length at a given drawn dimension, allowing for improved scaling and increased device density.

Method for improving device scalability of buried bit line flash EPROM

A process for fabricating contactless electrically programmable and electrically erasable memory cells of the flash EPROM type. The cells use elongated source and drain regions disposed beneath field oxide regions. Ammonia formed during the field oxidation process reacts with the silicon substrate to form a thin silicon nitride layer in the beak region. A thin tunnel oxide is then grown. During tunnel oxide formation lateral growth of the field oxide is inhibited by the thin nitride layer previously formed. However, the tunnel oxide thinning (due to the existence of the thin nitride layer) induced low breakdown voltage is overcome by the enhanced oxide growth in the beak due to the buried source/drain dopants. The tunnel oxide in the erase region is therefore uniform and thin. The thin, uniform oxide in the tunnel region leads to improved erase characteristics.

Method for improving erase characteristics of buried bit line flash

A process for fabricating contactless electrically programmable and electrically erasable memory cells of the flash EPROM type. The cells use elongated source and drain regions disposed beneath field oxide regions. Ammonia formed during the field oxidation process reacts with the silicon substrate to form a thin silicon nitride layer in the beak region. A thin tunnel oxide is then grown without the use of a sacrificial-oxide growth and removal method. During tunnel oxide formation lateral growth of the field oxide is inhibited by the thin nitride layer previously formed. However, the tunnel oxide thinning (due to the existence of the thin nitride layer) induced low breakdown voltage is overcome by the enhanced oxide growth in the beak due to the buried source/drain dopants. The tunnel oxide in the erase regon is therefore uniform and thin. The thin, uniform oxide in the tunnel region leads to improved erase characteristics.

A tungsten silicide reoxidation technique for forming a reoxidation layer in a CMOS device is disclosed. After forming an insulated gate member, which has a silicon-rich tungsten silicide layer overlying a polysilicon layer, it is first oxidized and the oxide is removed to expose WSi for forming a particular source/drain doped device. Then it is annealed in a substantially pure nitrogen ambient for a given time period. A subsequent growth of the reoxidation layer over the gate member by introducing oxygen results in a substantially planarized surface. The combination between tungsten and oxygen is prevented.

Tungsten-silicide reoxidation process including annealing in pure

A method of forming metal oxide semiconductor field-effect transistors (MOSFET) is described wherein the source and drain regions are disposed by ion implantation in a manner substantially perpendicular to the substrate surface in two steps, such that the concentration of impurities increases with lateral distance away from the gate electrode member to suppress the hot e injection, to prevent channeling effect, to increase punch through voltage and to increase gate-aided breakdown voltage.

Source drain doping technique

A tungsten silicide reoxidation technique for forming a reoxidation layer in a CMOS MOSFET device. After forming an insulated gate member, which has a tungsten silicide layer overlying a polysilicon layer, a CVD oxide layer is deposited on the exposed and crystallized tungsten silicide layer to function as a cap prior to the formation of the reoxidation layer. The CVD oxide layer operates to slow the passage of oxygen atoms to combine with the tungsten atoms of the silicide layer but allows free migration of silicon atoms from the polysilicon layer to the tungsten silicide surface and combine with the oxygen atoms in forming a substantially planarized and uncontaminated reoxidation layer without the requirement of a substantially pure nitrogen ambient.

Tungsten-silicide reoxidation technique using a CVD oxide cap

A method of forming complementary metal oxide semiconductor field-effect transistors (CMOSFET) is described wherein the source and drain regions are disposed by ion implantation in a manner substantially perpendicular to the substrate surface in two steps, such that the concentration of impurities increases with lateral distance away from the gate electrode member to suppress the hot e injection, to prevent channeling effects, to increase punch through voltage and to increase gate-aided breakdown voltage.

Growing community of inventors

Saratoga, CA, United States of America

Been-Jon K Woo