摘要:

We propose a new process for fabrication of an ultrafine anisotropic SiO2mask, successfully combining electron beam (EB) lithography and SF6reactive ion beam etching using an Al lift‐off. SiO2etching had a high selectivity of 50 over Al with an SF6pressure of 0.9 mTorr and an ion energy of 300 V, because formation of AlF3near the surface prevented the etching of Al. EB patterns were precisely transferred to the SiO2mask with a vertical wall. Using this process, lines with widths of 70 nm and dot arrays composed of columns with diameters of 70 nm were realized.  

ISSN:1071-1023    

DOI:10.1116/1.587764

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Extreme ultraviolet (EUV) projection lithography has been proposed to achieve features as small asL=180 nm to 70 nm for 1 G to 16 G DRAMs. Application will require high‐sensitivity resists and pattern fluctuation control to less than 10% of nominal linewidth. To evaluate low‐dose, resist material, and resist process dependent resist roughness limits in EUV lithography, a roughness model originally by Neureuther and Wilson is extended, and a new model for chemical amplification resists is presented and applied to EUV lithography. Analyses of molecular scale simulation and EUV exposures of novolac negative chemical amplification resists complete the study. For 13 nm exposure wavelengths, 180 nm lithography with positive chain‐scission resists requires at least 0.69 mJ/cm2, which scales to 54.3 mJ/cm2for 70 nm features, accounting for both intrinsic resist polymer roughness and absorption in 100 nm PMMA. At 4.5 nm exposure, the dose minima are 15.9 mJ/cm2and 1254 mJ/cm2, for 1 G and 16 G respectively. Novolac negative chemical amplification resists have a theoretical minimum linewidth of 115 nm, dependent on postexposure bake conditions and resist composition. Printability criteria limit the extent to which process variation can improve roughness. Existing novolac‐based negative chemical amplification resists are not suitable for EUV lithography in the 16 G regime, but may be suitable for the 4 G regime under certain conditions.

ISSN:1071-1023    

DOI:10.1116/1.587765

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Radiation stability of SiO2antireflective film coated SiN and SiC x‐ray mask membranes was studied. Although the transmission at 633 nm of the SiO2‐coated SiN was reduced by about 8% after synchrotron radiation (SR) exposure with an absorber dose of 100 MJ/cm3, the oscillation of the transmission due to interference was considerably suppressed even after the SR absorption. Furthermore, the optical transmission spectrum of the SiO2‐coated SiC was nearly equal to that of uncoated SiC after the SR absorption of 100 MJ/cm3. The pattern displacement induced by the SR absorption of 10 MJ/cm3for the SiO2‐coated SiN and for the SiO2‐coated SiC was σx=6 nm, σy=7 nm and σx=8 nm, σy=6 nm on the 25‐mm‐square area, respectively, the values of which were within the reproducibility of the displacement measurement. Electron spin resonance analysis indicated that no significant difference of spin density between the SiO2‐coated and uncoated SiN membranes was recognized before and after the SR absorption.

ISSN:1071-1023    

DOI:10.1116/1.587766

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Electron‐irradiation‐induced gold atom implantation into α‐SiC and β‐Si3N4has been studied by ultrahigh voltage electron microscopy (UHVEM). Bilayer films of Au(target atom)/α‐SiC (substrate) and of Au (target atom)/β‐Si3N4(substrate) were irradiated with 2‐MeV electrons in a UHVEM with the electron beam incident on the gold layer. In the Au/α‐SiC system, irradiation with 2‐MeV electrons first induces amorphization of the α‐SiC substrate, and then with continued irradiation gold atoms which have been knocked‐off from the gold layer by the collision with 2‐MeV electrons are implanted into the amorphous SiC substrate. The distribution of gold in amorphous SiC is not uniform and there exists a concentration fluctuation of gold with the average wavelength of a few to several nm. In the Au/β‐Si3N4system, it seems difficult to implant gold atoms into the β‐Si3N4substrate by MeV electron irradiation. The ease with which gold implantation into ceramic substrates takes place has been discussed in terms of the chemical constraint effect.

ISSN:1071-1023    

DOI:10.1116/1.587767

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A semiempirical model for the cost of a commercial plasma source ion implantation (PSII) facility is presented. Amortized capital and operating expenses are estimated as functions of the surface area throughputT. The impact of secondary electron emission and batch processing time is considered. Treatment costs are found to decrease monotonically withTuntil they saturate at largeTwhen capital equipment payback and space rental dominate the expense. A reasonably sized PSII treatment facility should be able to treat a surface area of 104m2per year at a cost of $0.01 per cm2.

ISSN:1071-1023    

DOI:10.1116/1.587768

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Several novel and unusual microstructures were made by focused ion beam milling. These microstructures include needles, hooks, forks, and similar shapes resulting from 360° access afforded to the ion beam by a rotation mounting device. The lengths of the microstructures are in the 10 μm range, and the thicknesses all in the 1–2 μm range. Similar procedures were used to make prototype stylus geometries for scanning probe microscopy applications. Resolution limits to the fabrication process come mainly from the grain structure of the material being sputtered. The ion beam is 0.3 μm in diameter, and 0.08 μm pixel resolution for ion beam location was used to generate the objects. Start‐to‐finish fabrication time for most of the objects made was ∼2 h without any effort to streamline the process.

ISSN:1071-1023    

DOI:10.1116/1.587769

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A system has been developed for implementing a solderless fine pitch Tape Automated Bonding (TAB) process. The process was applied to multichip module (MCM) packages with lead pitch of 100 μm. The technology can be extended to ultrafine pitch as low as 25 μm and can be used for both inner lead bonding and outer lead bonding. The technology is based on metal to metal diffusion at the lead to pad interface using a ‘‘hot’’ tip energized by a laser. A closed end flat tip was used to comply with safety requirements and provide uniform temperature distribution across the footprint of the tip. The tip has shown no degradation during the initial testing of 25 000 bonds. The technology is much simpler compared to the solder based TAB process. It is easily controlled, does not require any pretreatment of the pads and is less sensitive to pad contamination and surface nonplanarity. It can be applied to various sets of pad‐lead metallurgies such as Au–Au, Au–Sn, Cu–Au, and Ni–Au. The study shows that the process can be designed to be reworkable which makes it suitable for MCM applications.

ISSN:1071-1023    

DOI:10.1116/1.587770

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Gate oxides prepared by repeated rapid thermal annealings of the thermal oxide in N2O ambient is proposed and metal–oxide–semiconductor (MOS) capacitors with these newly proposed gate dielectrics are studied. It is found that both the charge‐to‐breakdown and the oxide breakdown field shift to higher values as the number of repeated annealings and the annealing time increase. All the samples that have been subjected to repeated N2O rapid thermal annealings exhibit improved Fowler–Nordheim constant current stress resistance and radiation hardness when compared to the fresh sample and the conventional one‐time N2O‐annealed sample with a comparable annealing time. It is believed that this multiple N2O annealing method can be another promising candidate for fabricating hot‐carrier resistant and radiation‐hard MOS devices.

ISSN:1071-1023    

DOI:10.1116/1.587771

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

An aluminum electrode is rf powered before sputter cleaning of wafers to reduce the partial pressure water vapor in an evaporator. Prolonged sputter cleaning times are thereby avoided because regrowth of the aluminum oxide during sputter cleaning is practically nil. Wafers with temperature sensitive resists, for example, with a polyimide or photoresist lift off mask for fabrication of the conductor lines can be sputter cleaned and low via resistance obtained without mask damage. Histograms of the via resistance as a function of the sputter cleaning time in the range from 15 to 60 s are presented for the as‐deposited and sintered metallization. The tooling and the process to obtain low via resistance are described. The author believes, that the principle method and electrode design may be useful for similar applications where a low partial pressure water vapor in a vacuum apparatus is required.

ISSN:1071-1023    

DOI:10.1116/1.587772

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The effect of O2+H2O plasma downstream ashing on sodium contamination from resists has been studied through measurement of flatband voltage shifts of metal–oxide–semiconductor (MOS) diodes after bias‐stress treatment and measurement by atomic absorption spectroscopy of the amount of sodium in the SiO2layer after resist stripping. The flatband voltage shift of the MOS diodes on which a resist layer was stripped by the O2+H2O plasma downstream was almost the same as that treated by the O2+H2O plasma downstream without resist and smaller than that where the resist was removed by other dry ashing methods such as O2plasma and O2plasma downstream. In addition, the amount of sodium that existed in the SiO2layer after resist ashing by the O2+H2O plasma downstream was also nearly the same as that in the SiO2layer as grown. This sodium passivation by the O2+H2O plasma downstream was most effective at the H2O percentage of 40%–60%, and did not depend on wafer temperature below 200 °C or over‐ashing time. These results support our original idea of sodium passivation, i.e., OH radicals generated in the O2+H2O plasma and its downstream react with sodium to prevent sodium invasion into the SiO2layer.

ISSN:1071-1023    

DOI:10.1116/1.587773

出版商:American Vacuum Society    

年代:1994

数据来源: AIP