This paper describes process technologies for an x-ray mask using Ta as the x-ray absorber and SiC as the x-ray membrane. SiC can be grown heteroepitaxially in a coldwall LPCVD reactor at 1000~ and 3.5 torr using a gas mixture of SiHC13, C3H8, and H2. SiC has a stress of 4 x 109 dyn/cm 2 and a Young's modulus of 4.7 x 10 '2 dyn/cm 2. Pure Ta with Ar ions implanted by 150 keV is more stable and dense than Ta alloys and their nitrides. The film density is about 16 g/cm 3 and the stress change due to annealing of 200~ is below 2 x 108 dyn/cm 2. The yield of stress control is 68% for 2 • l0 s dyn/cm 2. The temperature of the membrane during Ta RIE is controlled by He cooling from the back. It is held between 45 ~ and 100~ at a power density of 0.8 W/cm 2. A mixture of C12 and CC14 (1:1) is used as the etching gas. The gas pressure is from 0.18 to 0.2 torr. The etch rate of Ta is 1.2 ~tm/min and the selectivity of Ta to a resist (AMS-1) is 7. A 0.8 ~m thick Ta pattern of 0.15 ~m lines and spaces is obtained by using a 0.5 ~m thick single-layer resist. Electron beam lithography on a thin membrane requires a high-contrast resist (AMS-1) and a well-controlled correction of the proximity effect because of the high electron backscattering on Ta. Si etchback is done by spray etcher using a mixture of HF and HNO3 (1:3) with a high speed of 8 min per mask. The total fabrication process is designed to minimize mask distortion. The maximum mask distortion due to the absorber stress is 0.11 ~m (3~) including the measurement errors of Nikon 2I. The mask used for the measurement had a circular membrane of 60 mm diam and a 32 • 32 mm field window. The SiC was 2 ~m thick and the Ta was 0.8 ~m thick with a stress of 1.4 x 108 dyn/cm 2.It will be the key factor to establish a well-controlled and zero-defect x-ray mask for a successful application of x-ray lithography to deep submicron devices. The x-ray mask consists of some process technologies. Chemical vapor deposition (CVD), reactive ion etching (RIE), and electron beam delineation are the most common. The requirements for x-ray mask materials and processes are somewhat different from those of electronic devices.The x-ray membrane must have a tensile stress high enough to obtain flat surface and avoid vibration due to pressure difference on the two sides of the membrane. Especially, the mask vibration during the x-ray exposure and alignment process is a severe problem resulting in a loss of overlay accuracy and a loss of critical dimension (CD) control. A high stress above 1 x 109 dyn/cm 2 is preferable for this purpose. A high Young's modulus of membrane is
Study on the interface thermal stability of metal-oxide-semiconductor structures by inelastic electron tunneling spectroscopy Appl.Numerical simulations and experimental measurements of stress relaxation by interface diffusion in a patterned copper interconnect structure J. Appl. Phys. 97, 013539 (2005); 10.1063/1.1829372Bias-temperature stressing analysis on the stability of an ultrathin Ta diffusion barrier
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The addition of an atom having different bonding radii to a matrix film is an effective method for changing the stress of the film. In a plasma-enhanced CVD of BN, it is difficult to obtain tensile stress except for extremely boron-rich films. The controllability of tensile stress in BN film was improved by introducing a small amount of carbon into the BN matrix, using plasma-enhanced CVD between 400 ~ and 500~ We obtained transparent films with high Young's modulus and tensile stress. The radiation resistance of BNC deposited at 400~ was improved five times better than that of BN deposited by low-pressure CVD at similar temperatures. Boron compound films are attractive in applications for x-ray lithography and insulators for LSI devices, because boron compound films have a low atomic number, are chemically inert, and are thermally stable. Mydan et al. (1), Dana and Maldonado (2), and Shimkunas (3) reported applications of BN as x-ray mask membranes, while Yamaguchi and Minakata (4) and Miyamoto et al. (5) reported ap-ABSTRACTThe low pressure chemical vapor deposition (LPCVD) of in situ doped silicon from disilane (Si2H6) and phosphine (PH3) was investigated using response surface methodology experimental design. TEM and associated analytical techniques were employed in characterizing films deposited over the range of 475~176Polycrystalline films with a resistivity pf -770 1~2-cm after a 850~ 30 rain anneal with less than 5% thickness variation were deposited at approximately 60 A-min -1 over 100 mm wafers.
The authors have fabricated metal-oxide-semiconductor (MOS) contacts on silicon for spin injection and detection and characterized them by internal photoemission and capacitance-voltage (C-V) measurements with the aim of extracting the metal- semiconductor effective work-function mismatch that determines the magnetoresistance between such contacts. The authors show that sputter deposition of these contacts induces high levels of negative charge in the oxide localized close to the metal-oxide interface. This is seen to affect the electrostatics of the MOS contact and could thereby impact its contact resistance, and in turn, the magnetoresistance that one can obtain.
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