Patent number 8637214 is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "There is a continuing trend within the microelectronics industry to incorporate more circuitry having greater complexity on a single integrated circuit (IC) chip. Maintaining this trend generally entails shrinking the size of individual devices within the circuit by reducing the critical dimensions (CDs) of device elements along with the pitch, or the CD of such an element added to the spacing between elements. Microlithography tooling and processing techniques play an important role in resolving the features necessary to fabricate devices and accordingly, are continually under development to meet industry milestones relating to the CD and pitch characteristic of each new technology generation.
"High numerical aperture (NA) 193 nanometer (nm) optical projection stepper/scanner systems in combination with advanced photoresist processes now are capable of routinely resolving complex patterns that include isolated and dense resist features having CDs and pitches, respectively, well below the exposure wavelength. However, to meet the requirements of device design rules which continue to push the resolution limits of existing processes and tooling, other more specialized techniques have been developed to further enhance resolution. These include double patterning techniques (DPT) in which device patterns having potentially optically unresolvable features are decomposed into two or more complementary, and more easily resolvable patterns, each containing features with larger CDs and/or a relaxed pitch. One such DPT is referred to as litho/etch/litho/etch (LELE), and involves two separate lithographic exposures each followed by an etch process. These exposures are performed using different photomask reticles, each designed to image a portion of the total pattern. However, this scheme includes an additional etch step between lithography steps which increases fabrication cost and adds complexity to process logistics as wafers are transported between lithography and etch areas of a typical fab line. Other DPT processing options include spacer lithography processing often used, for example, in the fabrication of FinFet devices. However, these processes typically introduce several additional steps into a fabrication sequence adding yet further cost and complexity to the overall device fabrication process.
"DPT processes which utilize a single etch step known as litho/freeze/litho/etch (LFLE) have also been developed. In LFLE, a first pattern is imaged into a first layer of photoresist, and the resist layer then is 'frozen' rendering it unaffected by a second, subsequent photoresist process. A second pattern, complementary to the first pattern, then is formed into the second resist layer. However, the resolution conventionally attainable, for example, for isolated and dense trenches using existing LFLE processes is still limited to that of the lithography process.
"Accordingly, it is desirable to provide methods for fabricating semiconductor devices using DPT processes which provide improved resolution over existing DPT processes. Further, it is also desirable to provide methods for designing photomask patterns for such DPT processes. Furthermore, it is also desirable to provide photomasks for such DPT processes. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention."
In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "Methods are provided for fabricating a semiconductor device. In accordance with an exemplary embodiment of the invention, one method comprises the steps of providing a first pattern design having a first polygon, the first polygon having a first tonality and having a first side and a second side, the first side adjacent to a second polygon having a second tonality, and the second side adjacent to a third polygon having the second tonality. The method also comprises forming a second pattern design by reversing the tonality of the first pattern design, and wherein the first polygon is converted from the first tonality to the second tonality, and wherein the second and third polygons are both converted to the first tonality. The method further comprises forming a third pattern design from the second pattern design by converting the second polygon from the first tonality to the second tonality forming a fourth pattern design from the second pattern design by converting the third polygon from the first tonality to the second tonality forming a fifth pattern design by reversing the tonality of the third pattern design, and forming a sixth pattern design by reversing the tonality of the fourth pattern design.
"A method is provided for fabricating a semiconductor device in accordance with another exemplary embodiment of the invention. The method comprises providing a semiconductor substrate forming a first photoresist layer overlying the semiconductor substrate, and forming a first opening in the first photoresist layer, the first opening having a first side surface and a second side surface substantially parallel each other. The method also comprises freezing the first photoresist layer, forming a second photoresist layer on the first photoresist layer and in the first opening, and forming a second opening in the second photoresist layer, the second opening having a third side surface substantially parallel to the first and second side surfaces and positioned overlying the substrate between the first and second side surfaces, and a fourth side surface substantially parallel to the third side surface and positioned overlying the first photoresist layer.
"A photomask set suitable for a double patterning lithography technique is provided. The set comprises a first photomask comprising a first surface, a first substantially opaque layer on the first surface, and a first substantially transparent polygon etched into the first substantially opaque layer, the first substantially transparent polygon having a first side and a second side substantially parallel to each other. The set also comprises a second photomask comprising a second surface, a second substantially opaque layer on the second surface, and a second substantially transparent polygon etched into the second substantially opaque layer, the second substantially transparent polygon having a third side and a fourth side substantially parallel to the first and second sides, and wherein the first and second substantially transparent polygons overlap when the first and second photomasks are aligned to each other."
URL and more information on this patent, see: Deng, Yunfei; Kye, Jongwook. Photomask Sets for Fabricating Semiconductor Devices. U.S. Patent Number 8637214, filed
Keywords for this news article include: Electronics, Semiconductor,
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