Phase-shift mask

About: Phase-shift mask is a research topic. Over the lifetime, 2088 publications have been published within this topic receiving 18058 citations.

Far-field light imaging in the presence of atmospheric turbulence with rotating anti-phase apertures: Theoretical investigation

Abstract: We investigated the diffraction of far-field light objects in the presence of turbulence formed by an optical system with a rotating anti-phase mask. This mask facilitates to detect the position of faint companion in every direction around the bright companion. In the presence of atmospheric turbulence, diffraction images of distant objects are beyond the diffraction limits, the proposed phase shift mask has a merit to compensate the turbulence results high contrast astronomical imaging under partially coherent light illumination and it is proficient to increase the resolution limits in a Sparrow criterion sense. In this approach, we demonstrated the mask fabrication in laboratory conditions for future prospects and analyse the performance by computing the point spread function of the composite image under various considerations analytically.

Investigation of quartz etch rate uniformity for alternating phase-shift mask applications utilizing a next-generation ICP source

Abstract: As critical dimensions and exposure wavelengths approach the physical limitations of optical lithography, the use of newer techniques such as Phase Shift Photomask Technologies become necessary to extend the viability of DUV lithography tools. Alternating Phase Shift Mask technologies are challenging the capabilities of current quartz dry etch processes; as this phase shift technique is achieved by the precise removal of quartz, the need for ever improving phase shift uniformity across the photomask surface requires extremely uniform quartz etch depth. To this end, a Next Generation ICP (Inductively Coupled Plasma) hardware configuration has been adopted. In this article, the quartz etch parameter space of this new ICP source is explored. Finally, process results including, quartz roughness, sidewall profile, and most importantly quartz etch rate uniformity will be presented.

Fast nondestructive optical measurements of critical dimension uniformity and linearity on AEI and ASI phase-shift masks

Abstract: The fabrication of a production-worthy phase shift mask requires, among other things, excellent uniformity of critical dimensions (trench width and depth) and optical properties of the phase shift material (MoSi). Traditionally, CD-SEM has been the instrument of choice for the measurement of width; AFP (Atomic Force Profilometer) or conventional profilometer for the measurement of depth; and Interferometer for the measurement of phase shift and transmittance of the phase shift material. We present an innovative optical metrology solution based on broadband reflectometry, covering a wavelength range from 190 to 1000 nm, in one nanometer intervals. The analysis is performed using Forouhi-Bloomer dispersion equations, in conjunctions with Rigorous Coupled Wave Analysis (RCWA). The method provides accurate and repeatable results for critical dimensions, thickness, and optical properties (n and k spectra from 190 - 1000 nm) for all materials present in the structure. In the current study, the method described above was used to examine photomasks at two stages of mask manufacturing process: After Etch Inspection (AEI) and After Strip Inspection (ASI). The results were compared with the measurements taken on the same samples using conventional CD-SEM. Two comparison studies were conducted - global CD uniformity and CD linearity. The CD linearity study demonstrated excellent correlation between the values of grating line width obtained using this new optical reflectometry approach and a CD-SEM for the grating structures of two pitches (760 nm and 1120 nm). The global CD uniformity study revealed that this presented reflectometry method can be used to produce CD uniformity maps which demonstrate excellent correlation with the results obtained using a conventional CD-SEM. The advantages of the optical method are high throughput, non-destructive nature of the measurements and capability to measure a wider variety of structures pertinent to the photomask manufacturing process.

Phase shift mask comprising light shielding regions having a multiple box structure

Abstract: A phase shift mask for forming contact holes in the fabrication of highly integrated semiconductor devices. The phase shift mask includes a transparent substrate, a plurality of light exposure regions respectively defined by patterns formed on portions of the transparent substrate corresponding to contact holes which will be formed using the phase shift mask, the patterns including those comprised of a first phase shift film and those comprised of a second phase shift film exhibiting a difference in phase from the first phase shift film. The phase shift mask also includes a plurality of light shield regions respectively defined by patterns formed on portions of the transparent substrate not covered with the patterns defining the light exposure regions. The patterns of the light shield regions include those comprised of the first phase shift film and those comprised of the second phase shift film while the light shield regions each have a double box structure including an inner box and an outer box respectively consisting of the patterns of the first and second phase shift films associated with the light shield region. The patterns of the first and second phase shift films define the light exposure regions and light shield regions are arranged in such a manner that adjacent patterns are different in phase from each other.

Phase shift mask using CrAION as phase shifter material and manufacturing method thereof

Abstract: A phase shift mask formed by depositing on a transparent substrate a phase shifter material containing chromium (Cr), aluminum (Al), oxygen (O) and nitrogen (N). The transmissivity of a phase shifting layer of the phase shift mask, which is a CrAION layer, is increases, and the phase of exposure light is shifted by 180° at a predetermined thickness, so that a fine photoresist pattern can be formed. Also, the transmissivity of the phase shifting layer with respect to inspection light, which has a longer wavelength than exposure light, is relatively low, which permits accurate inspection of the mask. The phase shift mask can be useful in photolithography using a short wavelength of exposure light, and in an inspection apparatus using an inspection light source having a longer wavelength than exposure light.