Abstract: Reticle blanks, and divided reticles made therefrom, are disclosed for use in charged-particle-beam microlithography. The subject reticle blanks and reticles exhibit substantially reduced warp and resist stress, and hence substantially reduced positional distortion, compared to conventional reticles and reticle blanks. A reticle blank includes a silicon membrane supported on a grillage of struts formed from a thick silicon support substrate. The support substrate is made and worked separately to form the grillage of support struts and the membrane. A separate silicon-on-insulator (SOI) wafer is formed, including a silicon “active” layer, a buried oxide (BOX) layer, and a support wafer. The surface of the active layer is bonded to the surface of the support substrate, and the support wafer and BOX layer are removed to complete fabrication of the reticle blank. The support substrate has a thickness of at least 1 mm.

Abstract: Reticle blanks are disclosed for use in making reticles for charged-particle-beam microlithography. The reticle blanks include support struts formed by dry-etching intervening exposed regions of a silicon support substrate. The windows are defined by a dry-etching mask and are destined to become subfields of a reticle made from the reticle blank. The subfields of the reticle blank include patternable subfields and non-patternable subfields (dummy etching fields). The patternable subfields are destined to define respective portions of a reticle pattern, whereas the dummy subfields are not. The dummy etching fields are those that have experienced a dry-etching rate greater than a threshold value of 1.05-times the dry-etching rate of the patternable subfields. The reticle blanks also include support struts supporting a membrane (defining the subfields) and a peripheral frame connected to the support struts. The dummy etching fields are located peripherally to the patternable subfields.

Abstract: Methods are disclosed for manufacturing segmented reticle blanks for use in fabricating segmented reticles for charged-particle-beam (e.g., electron beam) microlithography. The reticle blank includes a grillage of support struts having a substantially uniform depth and width throughout the reticle blank. A reticle substrate is prepared from a silicon substrate wafer. Beginning on a second major surface of the wafer, discharge-machining is performed part way into the thickness dimension of the silicon substrate so as to form from the silicon substrate a grillage of intersecting struts separating respective subfield regions from one another. In regions not occupied by respective struts, further machining into the thickness dimension is performed by dry-etching until each subfield region includes a respective membrane formed by a residual portion of the reticle substrate extending into the thickness dimension from the first major surface.

Abstract: Methods are disclosed for fabricating, from a reticle blank, a stencil reticle for use in charged-particle-beam (CPB) microlithography. The methods prevent the accumulation, during a dry-etching step in which stencil apertures corresponding to pattern elements are formed in the membrane of the reticle blank, of dry-etching gas adjacent a back side of the membrane. Removing dry-etching gas from this location prevents the gas from eroding the membrane and, hence, prevents membrane fracture. In the reticle blank, the membrane is supported by a grillage of struts or the like typically made from a silicon substrate. To exhaust the dry-etching gas, a gap can be provided between a major surface of a dry-etching electrode and a second major surface of the reticle blank defined by edges of the grillage. Alternatively, channels can be defined either in the major surface of the dry-etching electrode or by forming notches or the like in the grillage elements.

Abstract: Methods are disclosed for manufacturing reticle blanks useful for forming reticles used in charged-particle-beam microlithography. The reticle blanks are formed that comprise support struts having sharply defined, vertical sidewalls without “icicles” being formed near or on the sidewalls. According to an exemplary method, an SOI (silicon-on-insulator) substrate is formed from a silicon support substrate, a silicon oxide layer on a first major surface of the silicon support substrate, and an SOI layer formed on the silicon oxide layer. A dry-etching mask is formed on a second major surface of the silicon support substrate. The mask defines windows in positions between which struts are to be formed. The dry-etching mask comprises a thin (desirably 1 &mgr;m to 2 &mgr;m thick) silicon oxide layer and a resist layer. The windows are dry-etched to form the struts, and the silicon oxide layer is removed.

Abstract: Apparatus and methods for making charged-particle-beam microlithography masks are provided. The apparatus and methods provide consistent maintenance of the temperature of a mask workpiece below a specified temperature during etch processes performed to make the mask. A workpiece (comprising a substrate upon which a membrane is formed) is placed in thermal contact with a temperature-controlled support. The workpiece is cooled as the support withdraws heat from the workpiece by thermal conduction. In a second aspect of the methods provided, the etch process is paused at regular intervals for set periods of time to provide the workpiece with a cooling period. The etch process is paused for a cooling period before the temperature of the workpiece increases to a level that may cause damage to the mask membrane and/or mask pattern. After the workpiece has cooled, the etch process can be resumed until the next cooling period or until the etch process is completed.

Abstract: Methods are disclosed for manufacturing silicon stencil masks for use in charged-particle-beam microlithography. According to the method, a boron-doped layer is formed on a silicon substrate, a mask pattern is formed on the boron doped layer, and the boron-doped layer is etched according to the mask pattern to form voids in the boron-doped layer. The voids do not extend completely through the thickness of the boron-doped layer. In subsequent steps, a silicon nitride layer is applied and etched to form openings in which the silicon substrate is etched away to form struts. Because the boron-doped layer is not completely etched through in the earlier etching step, the mask is much more resistant to fracture in a subsequent cleaning step. In a final step after cleaning, the boron-doped layer is etched to extend the voids completely through the thickness of the boron-doped layer.

Abstract: Methods for manufacturing mask substrates usable to make masks for use with charged particle beam or X-ray microlithography. Such masks have supports that are formed to have a minimum required width. The method involves forming a planar laminate of a membrane layer (destined to be the membrane of the mask), an etch-stopper layer, and a support-forming silicon layer. An etch-resistant layer is applied to the silicon layer, and a support-defining pattern is imposed on the etch-resistant layer by, e.g., a microlithographic technique. The resulting exposed portions of the silicon layer are removed by anisotropic dry etching (preferably plasma-enhanced dry etching at extremely low temperature or in the presence of a side-wall protective gas). The dry etching continues until the etch-stopper layer is reached. The resulting mask substrate has well defined supports with side walls perpendicular to the plane of the membrane.