Lsi Logic Corporation

John Haywood

Sheldon Aronowitz

Valeriy K Sukharev

Helmut Puchner

David C Lee

Nicholas K Eib

Ravindra Manohar Kapre

James O Kimball

James P Kimball

David Chan

Philippe Schoenborn

Jiunn-Yann Tsai

Jon S Owyang

Ming Yi Lee

A process for etching oxide is disclosed wherein a reproducibly accurate and uniform amount of silicon oxide can be removed from a surface of an oxide previously formed over a semiconductor substrate by exposing the oxide to a nitrogen plasma in an etch chamber while applying an rf bias to a substrate support on which the substrate is supported in the etch chamber. The thickness of the oxide removed in a given period of time may be changed by changing the amount of rf bias applied to the substrate through the substrate support.

Process for etching a controllable thickness of oxide on an integrated circuit structure on a semiconductor substrate using nitrogen plasma and plasma and an rf bias applied to the substrate

A process for inhibiting the passage of dopant from a gate electrode into a thin gate oxide comprises nitridation of the upper surface of the thin gate oxide, prior to formation of the gate electrode over the gate oxide, to thereby form a barrier of nitrogen atoms in the upper surface region of the gate oxide adjacent the interface between the gate oxide and the gate electrode to inhibit passage of dopant atoms from the gate electrode into the thin gate oxide during annealing of the structure. In one embodiment, a selective portion of silicon oxide on a silicon substrate may be etched to thin the oxide to the desired thickness using a nitrogen plasma with a bias applied to the silicon substrate. Nitridation of the surface of the etched silicon oxide is then carried out in the same apparatus by removing the bias from the silicon substrate.

PROCESS FOR FORMING THIN GATE OXIDE WITH ENHANCED RELIABILITY BY NITRIDATION OF UPPER SURFACE OF GATE OF OXIDE TO FORM BARRIER OF NITROGEN ATOMS IN UPPER SURFACE REGION OF GATE OXIDE, AND RESULTING PRODUCT

Provided are methods for fabricating hardened composite thin layer gate dielectrics. According to preferred embodiments of the present invention, composite gate dielectrics may be produced as bilayers having oyxnitride portions with nitrogen contents above 10 atomic percent, while avoiding the drawbacks of prior art nitridization methods. In one aspect of the present invention, a hardened composite thin layer gate dielectric may be formed by deposition of a very thin silicon layer on a very thin oxide layer on a silicon substrate, followed by low energy plasma nitridization and subsequent oxidation of the thin silicon layer. In another aspect of the invention, low energy plasma nitridization of a thin oxide layer formed on a silicon substrate may be followed by deposition of a very thin silicon layer and subsequent oxidation, or additional low energy plasma nitridization and then oxidation, of the thin silicon layer.

Composite semiconductor gate dielectrics

Provided is a method of fabricating gate dielectric layers having variable thicknesses and compositions over different regions of a semiconductor wafer. In a preferred embodiment of the present invention, a gate oxide layer is first grown over the various regions. Regions that are to have a relatively thicker, unhardened gate dielectric are masked and the wafer is exposed to a remote low energy nitrogen plasma. After the nitridization process is completed, the mask is removed and the wafer is exposed to further oxidation. The regions where oxynitrides have been formed act as a barrier to the oxidation process. Consequently, different oxide thicknesses can be grown on the same wafer, thinner and hardened where nitridization has been performed, and thicker and not hardened in those regions that were masked during the nitridization. Variable thickness gate dielectrics in accordance with the present invention may be particularly advantageous in semiconductor integrated circuits involving both digital and analog devices.

Method of forming variable thickness gate dielectrics

A process for forming a photoresist mask over a patternable layer of an integrated circuit structure formed on a semiconductor substrate is described wherein the photoresist mask is initially formed with oversized lateral dimensions over a layer of patternable material of an integrated circuit on a semiconductor substrate. The oversized resist mask is then optionally measured in a vacuum apparatus to determine the size of the critical dimensions; then dry etched, preferably in the same vacuum apparatus, to reduce the size of the resist mask; then measured to determine the size of the critical dimensions (preferably again in the same vacuum apparatus); and then, if necessary, further dry etched to further reduce the size of the critical dimensions. The dry etching and subsequent measurement steps are repeated until the desired critical dimensions of the resist mask are reached. If the dry etching step should accidentally overetch the resist pattern, the structure can still be reworked by removing the resist mask and applying a fresh resist layer as in the prior art. After the correctly sized resist mask has been formed and determined by the cycle of dry etch and measurement steps, the underlying patternable layer can be etched through the photoresist mask, with a greatly reduced chance that the etched pattern in the underlying layer will have unsatisfactory dimensions.

Process for forming photoresist mask over integrated circuit structures

A process for forming improved metal silicide contacts over the gate electrode and source/drain regions of MOS devices of an integrated circuit structure formed in a silicon substrate is described. The metal silicide contacts are formed by first forming a silicon oxide layer over exposed portions of the silicon substrate and over exposed surfaces of previously formed polysilicon gate electrodes. Silicon nitride sidewall spacers are then formed over the oxide on the sidewalls of the gate electrode by depositing a silicon nitride layer over the entire structure and then anisotropically etching the silicon nitride layer. Source/drain regions are then formed in the silicon substrate adjacent the nitride spacers and the structure is then contacted with an oxide etch to remove oxide from the upper surface of the gate electrode and the substrate surface over the source/drain regions. During the oxide etch step, notches, each having an aspect ratio of 1 or less, are formed in the exposed edges of the oxide respectively between the silicon nitride spacers and either the substrate or the gate electrode. A metal layer capable of reacting with the exposed silicon to form metal silicide contacts is then blanket deposited over the structure and into the notches. After reacting the metal with silicon surfaces with which it is in contact to form metal silicide, the unreacted metal is removed, leaving a metal silicide gate contact on the upper surface of the polysilicon gate electrode, as well as those upper portions of the sidewall of the gate electrode exposed by forming the notch in the oxide layer on the sidewall of the electrode. Metal silicide source/drain contacts of enlarged area are also formed over the exposed silicon surfaces of the source/drain regions and those portions of the silicon substrate beneath the nitride spacers exposed by the notches formed in the oxide beneath the nitride spacers.

Process for forming integrated circuit structure with metal silicide

A uniformly doped polysilicon gate electrode of an MOS device forming a part of an integrated circuit structure on a semiconductor substrate is formed by first depositing a very thin layer of amorphous or polycrystalline silicon, e.g., from about 2 nm to about 10 nm, over a gate oxide layer. The thin layer of silicon layer is then exposed to a nitrogen plasma formed from N.sub.2 at a power level sufficient to break the silicon--silicon bonds in the thin layer of silicon, but insufficient to cause sputtering of the silicon to cause a barrier layer of silicon and nitrogen to form at the surface of the thin silicon layer. Further silicon, e.g., polysilicon, is then deposited over the barrier layer to the desired thickness of the polysilicon gate electrode. The gate electrode is then conventionally doped, i.e., by implantation followed by furnace annealing, to diffuse and activate the dopant in the polysilicon gate electrode without, however, resulting in penetration of the dopant through the barrier layer into the underlying gate oxide layer or the semiconductor substrate.

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Santa Clara, CA, United States of America

John Haywood