Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2001-03-28
2003-02-11
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S302000, C430S309000, C430S310000, C430S311000
Reexamination Certificate
active
06517977
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to semiconductor devices, microelectronic devices, micro-electro mechanical devices, microfluidic devices, and more particularly to a lithographic template, a method of forming the lithographic template and a method for forming these devices with the lithographic template.
BACKGROUND OF THE INVENTION
The fabrication of integrated circuits involves the creation of several layers of materials that interact in some fashion. One or more of these layers may be patterned so various regions of the layer have different electrical characteristics, which may be interconnected within the layer or to other layers to create electrical components and circuits. These regions may be created by selectively introducing or removing various materials. The patterns that define such regions are often created by lithographic processes. For example, a layer of photoresist material is applied onto a layer overlying a wafer substrate. A photomask (containing clear and opaque areas) is used to selectively expose this photoresist material by a form of radiation, such as ultraviolet light, electrons, or x-rays. Either the photoresist material exposed to the radiation, or that not exposed to the radiation, is removed by the application of a developer. An etch may then be applied to the layer not protected by the remaining resist, and when the resist is removed, the layer overlying the substrate is patterned.
Lithographic processes such as that described above are typically used to transfer patterns from a photomask to a device. As feature sizes on semiconductor devices decrease into the submicron range, there is a need for new lithographic processes, or techniques, to pattern high density semiconductor devices. Several new lithographic techniques which accomplish this need and have a basis in imprinting and stamping have been proposed. One in particular, Step and Flash Imprint Lithography (SFIL), has been shown to be capable of patterning lines as small as 60 nm.
SFIL templates are typically made by applying a layer of chrome, 80-400 nm thick, onto a transparent quartz plate. A resist layer is applied to the chrome and patterned using either an electron beam or optical exposure system. The resist is then placed in a developer to form patterns on the chrome layer. The resist is used as a mask to etch the chrome layer. The chrome then serves as a hard mask for the etching of the quartz plate. Finally, the chrome is removed, thereby forming a quartz template containing relief images in the quartz.
Overall, SFIL techniques benefit from their unique use of photochemistry, ambient temperature processing, and the low contact pressure required to carry out the SFIL process. During a typical SFIL process, a substrate is coated with an organic planarization layer, and brought into close proximity of a transparent SFIL template, typically comprised of quartz, containing a relief image and coated with a low surface energy material. An ultraviolet or deep ultraviolet sensitive photocurable organic solution is deposited between the template and the coated substrate. Using minimal pressure, the template is brought into contact with the substrate, and more particularly the photocurable organic layer. Next, the organic layer is cured, or crosslinked, at room temperature by photoillumination through the template. The light source typically uses ultraviolet radiation. A range of wavelengths (150 nm-500 nm) is possible, depending upon the transmissive properties of the template and photosensitivity of the photocurable organic. The template is next separated from the substrate and the organic layer, leaving behind an organic replica of the template relief on the planarization layer. This pattern is then etched with a short halogen breakthrough, followed by an oxygen reactive ion etch (RIE) to form a high resolution, high aspect-ratio feature in the organic layer and planarization layer.
The distinction between a lithographic mask and a lithographic template should be noted. A lithographic mask is used as a stencil to impart an aerial image of light into a photoresist material. A lithographic template has a relief image etched into its surface, creating a form or mold. During SFIL, a pattern is defined when a photocurable liquid flows into the relief image and is subsequently cured. During standard imprint lithography, a pattern is defined when a material present on the surface of a substrate material deforms in response to pressure exerted thereupon. The attributes necessary for masks and templates, therefore are quite different.
SFIL technology has been demonstrated to resolve features as small as 60 nm. As such, a wide variety of feature sizes may be drawn on a single wafer. Certain problems exist though with this SFIL template fabrication methodology. In particular, problems exist with respect to incorporating the template fabrication into existing lithographic equipment and handlers. Typical template fabrication for SFIL requires the cutting of a standard 6″×6″×0.250″ photomask, or template material, into 1″ squares. It is well known that this cutting procedure causes a significant amount of contamination of the actual template end product. In addition, this methodology requires the utilization of non-standard equipment for testing, handling, inspection and repair, which adds expense and complexity to the fabrication process. Once the template has been formed, it is mounted for use in a carrier as is generally indicated in
FIG. 1
, referenced prior art. More specifically, illustrated is a template
10
, including a patterned portion
11
, which is mounted into a carrier
12
, in which a force, typically a compression force, illustrated by arrows
14
, is applied to the exterior vertical aspects of the template by carrier
12
. The template
10
is held in place by this carrier
12
and force
14
relative to a substrate wafer
16
, and utilized to accomplish SFIL.
As previously stated, this 1″ template format precludes the use of standard photomask inspection equipment and cleaning of the equipment once template
10
has been cut. This preclusion is caused by the fact that standard photomask equipment utilizes a larger format, typically in a range of 3″ to 9″, with a most common embodment ranging from 5″-6″. The template periphery is typically rectangular in shape, however a circular or round format can also be used and may contain a flat, notch or the like formed in or on a peripheral surface for alignment purposes. In addition, special carrier device
12
required for mounting template
10
for use due to its uncommon format of 1″ square, causes distortion in patterned portion
11
of the template due to the necessary compression force
14
required for mounting within carrier device
12
. Accordingly, it would be beneficial to improve upon a template for use in lithography processes in which a template is fabricated so as to conform with standard photomask equipment present in the industry.
It is a purpose of the present invention to provide for an improved lithographic template, a method of fabricating the improved lithographic template, and a method for making devices with the improved lithographic template in which standard handling and inspection equipment now present in the field is able to be utilized.
It is yet another purpose of the present invention to provide for an improved lithographic template, a method of fabricating the improved lithographic template, and a method for making devices with the improved lithographic template in which improvement in the template provides for higher throughput and cost effectiveness.
SUMMARY OF THE INVENTION
This invention relates to semiconductor devices, microelectronic devices, micro electro mechanical devices, microfluidic devices, and more particularly to a lithographic template, a method of forming the lithographic template and a method for forming devices with the lithographic template. Disclosed is a lithographic template including a planar mat
Nordquist Kevin J.
Resnick Doug J.
Koch William E.
Motorola Inc.
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