Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
1999-04-12
2001-11-13
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S313000, C430S323000, C430S324000, C430S950000
Reexamination Certificate
active
06316168
ABSTRACT:
BACKGROUND
1. Technical Field
This disclosure relates to semiconductor fabrication and more particularly, to improved top layer imaging lithography wherein silicon is incorporated in an under layer to provide improved image quality.
2. Description of the Related Art
Semiconductor fabrication processes typically include photolithographic processing to pattern areas of a surface of a semiconductor device to form a protective layer over areas, preferably using a resist material. The protected areas remain during subsequent etching wherein the unprotected areas are etched away as needed. For top layer imaging, an image is formed by exposing and developing a thin imaging layer on the surface of a semiconductor device. The image created by exposing and developing the thin imaging layer is transferred to an under layer by an etching process where the top layer functions as an etch mask. The top layer or imaging layer that remains on the surface withstands the etch process and prevents etching in the protected areas.
After the first etch step, the resist or thin imaging layer is removed. The remaining portion of the under layer may now be used as a mask to etch a stack or substrate below the under layer. A subsequent etch step transfers the pattern of the under layer to the stack or substrate. Since the top layer is present during the under layer etching process, “grass formation” occurs on the top layer. Grass formation is the redeposition of silicon byproducts on the top layer as a result of etching the under layer. Grass formation typically results in a degradation of image transfer to the under layer from the top layer.
The top layer imaging technique also suffers from poor coating quality of the thin imaging layer. In conventional fabrication processes, the top layer performs two functions. First it provides an image to be transferred, and second it provides etch resistance to protect areas of the under layer while etching exposed areas of the under layer. These functions are balanced between image quality of the top layer and the etch resistance of the top layer.
Therefore, a need exists for a method which provides image transfer using an under layer to transfer the image. A further need exists for a method for providing improved coating quality using a high performance photoresist as a top layer by employing silylated portions of an under layer as an etch mask instead of the top layer.
SUMMARY OF THE INVENTION
A method for etching a surface includes the steps of providing an under layer formed on the surface and a top layer formed on the under layer, patterning the top layer to expose portions of the under layer, forming a layer including silicon on the exposed portions of the under layer, removing the top layer to expose the under layer in portions other than the portions of the under layer having the silicon layer thereon and etching the under layer in portions other than the portions of the under layer having the silicon layer thereon to expose the surface.
A method for etching a substrate for semiconductor devices includes the steps of providing an under layer formed on the substrate and a top layer formed on the under layer, patterning the top layer to expose portions of the under layer, forming a layer including silicon on the exposed portions of the under layer, removing the top layer to expose the under layer in portions of the under layer other than the portions of the under layer having the silicon layer thereon and mask open etching the under layer to transfer a pattern defined by the silicon layer to the substrate and etching the substrate in accordance with the pattern of the under layer.
Another method for etching a substrate for semiconductor devices includes the steps of providing an under layer formed from an anti-reflective resist material on the substrate and a top layer formed on the under layer, the top layer including a resist material, patterning the top layer to expose portions of the under layer by exposing and developing the resist material of the top layer, silylating the exposed portions of the under layer to form a silylated layer thereon by implanting silicon ions in the exposed portions of the under layer, removing the top layer to expose the under layer in portions of the under layer other than the portions of the under layer having the silylated layer thereon and mask open etching the under layer by providing etchant gases to transfer a pattern defined by the silylated layer to the substrate and etching the substrate in accordance with the pattern of the under layer.
In alternate methods, the top layer may include a photoresist and the step of patterning may include the steps of exposing the photoresist to light and developing the away portions of the resist to expose the portions of the under layer. The step of patterning preferably includes the step of depositing the top layer having a thickness between about 1000 Å and about 3000 Å. The step of forming a layer may include silicon includes the step of ion implanting a material including silicon on the exposed portions of the under layer. The step of ion implanting may include the step of adjusting a penetration depth of the ions to less than a thickness of the top layer. The step of ion implanting may include the step of adjusting an incident angle of the ions to silylate the exposed portions of under layer. The step of forming a layer including silicon may include the step of employing a silicon target for collimated sputtering of the layer including silicon or chemically bonding a reagent including silicon to the exposed portions of the under layer. The implanting silicon ions may include the step of adjusting a penetration depth of the ions to less than a thickness of the top layer and/or adjusting an incident angle of the ions to silylate the exposed portions of under layer. The step of silylating may include the step of employing a silicon target for collimated sputtering of the layer including silicon or chemically bonding a reagent including silicon to the exposed portions of the under layer.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.
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Butt Shahid
Schroeder Uwe Paul
Barreca Nicole
Huff Mark F.
Paschburg Donald B.
Siemens Aktiengesellschaft
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