Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2001-11-14
2004-06-15
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S313000, C430S314000, C430S315000
Reexamination Certificate
active
06749969
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing masks composed of reticle patterns on chrome-coated plates or other types of correct negative masks and, more particularly, for producing a correct negative mask for damascene level production.
Masks are becoming a predominant factor in the manufacturer of integrated circuit semiconductor devices. Reduction lenses are used to reduce the patterning for applying to a wafer surface. To shrink patterns with each generation of semiconductor device, the amount of information on the mask increases considerably over time.
As a result, lithography is moving into new and difficult areas where the shrinking dimensions are no longer able to be resolved with standard techniques. Dense line and space patterns can be printed using off-axis light, such as annular, quadrapole or even dipole illumination. However, there are other features such as isolated and semi-dense structures to print which are not dense line and space patterns. It has been shown that these structures can be made to look dense by adding “assist” features to them. These sub-minimum assist features act to make the structure print as if it were a dense pattern, but are designed just below the resolution limits so they do not themselves print.
FIG. 1
illustrates the printing of standard desired features compared to printing of desired features and added assist features. Particularly, reference numeral
10
identifies a standard isolation line, while reference numeral
12
illustrates the isolated line along with the assist features on either side. In production, these assist features are printed on the reticle but do not print on the wafer. Similarly, reference numeral
14
identifies a series of nested lines as a desired feature, while corresponding reference numeral
16
illustrates the nested lines with assists. Finally, reference numeral
18
illustrates contacted pitch lines as a desired feature, while reference numeral
20
illustrates the contacted pitch lines with the assists. By making the structures look dense and using off-axis illumination, the process window (mostly depth of focus) for printing all of the features improves significantly.
The addition of assist features to the standard design features has become an industry standard solution for producing correct positive reticles with positive tone resists. However, reticles used in creating damascene level are not correct positive masks. Instead, correct negative masks are used in manufacturing for the contact/vias and metal lines.
When the pattern illustrated in
FIG. 1
is reversed, small holes must be resolved instead of small lines. The resolution and linearity for printing small lines is significantly better than small holes, as illustrated by the curves in FIG.
2
. The curves labeled with the suffix “Opq”, representing opaque, refer to isolated lines printed with correct positive designs. Conversely, the curves labeled with the suffix “Clr”, representing clears, refers to printing of isolated holes or spaces. The prefix “
3500
” identifies a tool that is an I-line mask writer ideal for printing these features as it can print with a very small grid. The curves with the suffix “Meb” represents an MEBES e-beam tool. Both tools show significantly better performance for the printing of small lines than for the printing of small holes.
The present invention is directed to further improvements in mask manufacture.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided a method for producing a correct negative reticle with positive tone resists. This method is not necessarily limited to binary masks but could be used with other masks that could utilize a reverse tone process.
Broadly, in accordance with one aspect of the invention there is provided a method of producing a reverse image mask comprising the steps of: depositing a metallic layer on a substrate; applying resist on the metallic layer to pattern desired features; plating the metallic layer with a metal film; stripping the resist; and etching the metallic layer using the metal film as a mask.
It is a feature of the invention that depositing a metallic layer on the substrate comprises depositing chrome on the substrate.
In accordance with one aspect of the invention, the substrate comprises a glass substrate.
In accordance with another aspect of the invention, the substrate comprises a quartz substrate.
The metal film may comprise copper or nickel, or the like.
It is a feature of the invention that applying resist on the metallic layer to pattern desired features comprises printing a reverse pattern in positive tone resist.
It is a further feature of the invention to include the step of etching the metal film to provide the reverse image mask.
It is yet another feature of the invention that plating the metallic layer with a metal film comprises electroplating copper to the metallic layer in areas not covered by the resist pattern.
It is still another feature of the invention that applying resist on the metallic layer further comprises applying assist features proximate the desired features.
There is disclosed in accordance with another aspect of the invention a method of producing a correct negative reticle with positive tone resist comprising the steps of depositing an opaque metallic layer on a transparent substrate; printing a reverse pattern of positive tone resist on the opaque metallic layer to pattern desired features; plating the opaque metallic layer with copper in non-patterned areas; stripping the resist; and etching the opaque metallic layer using the copper in the non-patterned areas as a mask.
REFERENCES:
patent: 4174219 (1979-11-01), Anares et al.
patent: 4306006 (1981-12-01), Descamps et al.
patent: 5229230 (1993-07-01), Kamon
patent: 5397663 (1995-03-01), Uesawa et al.
patent: 5578422 (1996-11-01), Mizuno et al.
patent: 5792596 (1998-08-01), Yasuzato et al.
patent: 5932395 (1999-08-01), Okamoto et al.
patent: 5976968 (1999-11-01), Dai
patent: 6020109 (2000-02-01), Okamoto et al.
patent: 6022644 (2000-02-01), Lin et al.
patent: 6048647 (2000-04-01), Miyazaki et al.
patent: 6074787 (2000-06-01), Takeuchi
Horak David V.
Leidy Robert K.
Wood Phillips Katz Clark & Mortimer
Young Christopher G.
LandOfFree
Reverse tone process for masks does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reverse tone process for masks, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reverse tone process for masks will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3322365