Data processing: structural design – modeling – simulation – and em – Modeling by mathematical expression
Reexamination Certificate
2003-01-13
2004-10-19
Phan, Thai (Department: 2128)
Data processing: structural design, modeling, simulation, and em
Modeling by mathematical expression
C703S006000
Reexamination Certificate
active
06807519
ABSTRACT:
TECHNICAL FIELD
The invention pertains to methods of forming radiation-patterning tools. In particular aspects the invention pertains to computer readable code that can enable a computer to determine locations for placement of sidelobe inhibitors. The code can be, for example, on a computer readable media or in a carrier wave.
BACKGROUND OF THE INVENTION
Photolithography is commonly used during formation of integrated circuits on semiconductor wafers. More specifically, a form of radiant energy (such as, for example, ultraviolet light) is passed through a radiation-patterning tool and onto a radiation-sensitive material (such as, for example, photoresist) associated with a semiconductor wafer. The radiation-patterning tool can be referred to as a photomask or a reticle. The term “photomask” traditionally is understood to refer to masks which define a pattern for an entirety of a wafer, and the term “reticle” is traditionally understood to refer to a patterning tool which defines a pattern for only a portion of a wafer. However, the terms “photomask” (or more generally “mask”) and “reticle” are frequently used interchangeably in modern parlance, so that either term can refer to a radiation-patterning tool that encompasses either a portion or an entirety of a wafer. For purposes of interpreting this disclosure and the claims that follow, the terms “reticle” and “photomask” are utilized with their traditional meanings.
Radiation-patterning tools contain light restrictive regions (for example, totally opaque or attenuated/half-toned regions) and light transmissive regions (for example, totally transparent regions) formed in a desired pattern. A grating pattern, for example, can be used to define parallel-spaced conductive lines on a semiconductor wafer. As discussed previously, the wafer is provided with a layer of radiation-sensitive material (such as, for example, photosensitive resist material, which is commonly referred to as photoresist). Radiation passes through the radiation-patterning tool onto the layer of photoresist and transfers a pattern defined by the radiation-patterning tool onto the photoresist. The photoresist is then developed to remove either the exposed portions of photoresist for a positive photoresist or the unexposed portions of the photoresist for a negative photoresist. The remaining patterned photoresist can then be used as a mask on the wafer during a subsequent semiconductor fabrication step, such as, for example, ion implantation or etching relative to materials on the wafer proximate the photoresist.
Advances in semiconductor integrated circuit performance have typically been accompanied by a simultaneous decrease in integrated circuit device dimensions and a decrease in the dimensions of conductor elements which connect those integrated circuit devices. The demand for ever smaller integrated circuit devices brings with it demands for ever-decreasing dimensions of structural elements, and ever-increasing requirements for precision and accuracy in radiation patterning.
FIG. 1
shows a flow chart illustrating a typical process utilized for creating a pattern for a radiation-patterning tool. At an initial step
10
, a preliminary design is created for the radiation-patterning tool and verified. The creation of the design begins with provision of a desired pattern which is ultimately to be formed in photoresist. Subsequently, elements are developed for the radiation-patterning tool to roughly produce the desired pattern on photoresist from radiation passed through the radiation-patterning tool. The elements form a rough correspondence to the desired pattern in that the first approximation of the elements largely ignores effects of interference on radiation passing through the radiation-patterning tool.
After the design is believed to be complete, (i.e., once it is believed that all patterned features which are to be patterned in photoresist with the radiation-patterning tool are represented by elements in the design) the design is submitted to a verification process to confirm that the design is complete.
After the design has been created and verified, it is subjected to optical proximity correction (shown as step
20
in FIG.
1
). The optical proximity correction takes into account various interference factors that influence radiation passing through a radiation-patterning tool (i.e., constructive and destructive interference effects that result from passing radiation through patterns having dimensions on the same order as the wavelength of the radiation, or smaller). The optical proximity correction can be utilized to correct all parts of the design, or only some parts of the design. In other words, the optical proximity correction can be applied to only some portions of a design, while other portions are not optical proximity corrected. Typically there will be a verification step following the optical proximity correction.
The steps of generating a design from a desired pattern which is to be provided in photoresist, verification of the design, optical proximity correction, and verification of the correction, are typically accomplished primarily through the use of software. A suitable software package which can be utilized for one or more of the steps is HERCULES™/TAURUS OPC™, which is available from Synopsys Corporation™.
The optical proximity correction creates a dataset which is subsequently translated into a pattern formed on a radiation-patterning tool. The process of translating the dataset into a pattern on the radiation-patterning tool is frequently referred to as taping the pattern onto the radiation-patterning tool. In such context, the terms “tape” and “tape out” refer to a process of transferring the dataset to appropriate hardware which writes a pattern represented by the dataset onto the radiation-patterning tool. The process of writing onto the radiation-patterning tool can be accomplished by, for example, laser writing and/or electron-beam writing methodologies. The step of taping the pattern onto the radiation-patterning tool is shown in
FIG. 1
as step
30
.
After the pattern has been formed on the radiation-patterning tool, the tool can be utilized for patterning radiation in semiconductor fabrication processes.
FIG. 2
illustrates an exemplary apparatus
40
in which a radiation-patterning tool is utilized for patterning radiation. Apparatus
40
comprises a lamp
42
which generates radiation
44
. Apparatus
40
further comprises a radiation-patterning tool
46
through which radiation
44
is passed. A semiconductor substrate
48
having a radiation-sensitive material
50
thereover is illustrated associated with apparatus
40
. The radiation passing through radiation-patterning tool
46
impacts radiation-sensitive material
50
to form a pattern within the radiation-sensitive material. The process of forming a pattern in a radiation-sensitive material with a radiation-patterning tool can be referred to as a printing operation.
Radiation-patterning tool
46
typically comprises an opaque material (such as chrome) over a transparent material (such as a glass). Radiation-patterning tool
46
has a front side where the pattern is formed as features (or windows) extending through the opaque material, and has a back side in opposing relation to the front side. The shown radiation-patterning tool has two opposing sides
45
and
47
, and in practice one of the two sides would be the front side (typically side
45
) and the other would be the back side. In some applications features can be printed on both the front side and back side of the radiation-patterning tool.
As discussed above, radiation-patterning tool
46
will typically have a pattern with dimensions on the order of the wavelength of the radiation passing through the radiation-patterning tool, or smaller. Accordingly, various interference effects can occur as the radiation passes through the radiation-patterning tool so that the radiation exiting the radiation-patterning tool will transfer a pattern somewhat different than the pattern of the radiation-patterning tool.
Phan Thai
Wells St. John P.S.
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