Atsumi Yamaguchi

Ar ion implantation into resist for etching resistance improvement

Argon (Ar) ion implantation into resist pattern was investigated and the remarkable improvement of the etching resistance was confirmed on various films such as tungsten, aluminum copper, silicon oxide and silicon nitride. The possibility to make resist thickness thinner was proven. Ion dose more than 1E15/cm2 was necessary to obtain a sufficient effect, so that shrinking of resist thickness and pattern width occurred simultaneously. The dependence of pattern shrinking on the line width was observed. Line width uniformity within a wafer was improved because of high etching resistance by ion implantation process. Line edge roughest (LER) or resist pattern was also reduced by ion implantation and smooth etched pattern could be formed. Although same effects were obtained for ArF resist, the shrinkage of ArF resist after ion implantation was more than that of KrF resists. The improvements in etching resistance and critical dimension (CD) control will be discussed in this article.

0.10 µm Dense Hole Pattern Formation by Double Exposure Utilizing Alternating Phase Shift Mask Using KrF Excimer Laser as Exposure Light

Dense 0.10 µm hole pattern formation is achieved by optical lithography with a KrF excimer laser. A Double exposure utilizing two alternating phase shift masks (PSMs) of the line-and-space (L/S) pattern laid out in different directions produces a dense and small hole image in bright field with large focus and exposure latitude. Applying this method with a KrF excimer laser stepper and a chemically amplified negative-tone resist, a two-dimensional (2-D) 0.10 µm hole array with 0.40 µm pitch is resolved with a 0.6 µm depth of focus (DOF). The hole diameter and pitch in the resolution limit seem to be less than 0.10 µm and 0.28 µm, respectively. Also, 2-D hole arrays with different pitches in the x and y directions are easily formed using masks with different pitches in each direction. The hole pattern of an actual DRAM cell is successfully formed by this method. Because of the excellent patterning performance, this method will enable the fabrication of multi giga bit DRAMs by KrF excimer laser lithography.

0.12 /spl mu/m hole pattern formation by KrF lithography for Giga bit DRAM

Dense 0.10 /spl mu/m hole pattern formation has been achieved by optical lithography with KrF wavelength. Double exposure utilizing two alternative phase shift masks of lines and spaces patterns produces dense small hole images with enough focus and exposure latitude. Applying this method with a KrF stepper and chemically-amplified negative-tone resist, a 2-dimensional 0.13 /spl mu/m hole array with a pitch of 0.40 /spl mu/m has been resolved with 1.0 /spl mu/m DOF, and resolution limit size and pitch are less than 0.10 /spl mu/m and 0.28 /spl mu/m, respectively.

Improvement of CD control and resolution by optimizing inorganic ARC process

The comparison of organic and inorganic bottom antireflective coating (BARC) discussed, especially about resolution improvement considering dry etching characteristics of ARC. The target was 0.2micrometers gate layer with shallow trench isolation and KrF negative resist process was used. By evaluation of etching characteristics for hard mask, it was found that etching critical dimension (CD) shift from resist pattern was almost determined by neighboring space width. The CD shift of isolated line pattern was more than +50nm for organic ARC. When CD shift should be corrected accurately by mask correction, the problem occurred that depth of focus of resist pattern was extremely small to compensate such large CD shift. Inorganic ARC could reduce the CD shift of isolated line pattern by 15nm compared to organic ARC. Although CD-DOF for isolated line was deteriorated after etching in the case of organic ARC, that was maintained in the case of inorganic ARC. Organic ARC was superior for the resist line width control on substrate step and inorganic ARC was superior for line end shortening of resist pattern, while both ARCs showed nearly equal performance after etching. Considering the stage of post-etching, inorganic ARC improved resolution of 0.2micrometers isolated pattern by 20-30 nm and DOF with no worse line width control than organic ARC.

Insolubilization mechanism of chemically amplified negative photoresists

This article reports on the difference of chemical reactions of polyvinylphenol (PVP) and novolak resin as a base polymer with a melamine cross‐linker. Measurements by gel permeation chromatography (GPC) and solubility testing using alkaline developer and acetone indicate that a cross‐linking reaction is predominant for dissolution inhibition in the case of the resists comprising PVP (PVP‐type resists), while protection of hydroxyl groups for the developer is predominant in the case of the resists comprising novolak resin (novolak‐type resists). The dissolution characteristics show that the novolak‐type resists have higher contrast than the PVP‐type resists. As the concentration of the melamine cross‐linker increases, the resolution of the PVP‐type resist becomes higher, while that of the novolak‐type resist becomes lower. Significant differences in chemical reactions and lithographic performances were found between PVP and novolak resin for chemically amplified negative photoresists.

Relation between optical property of pattern image and adhesion of resist pattern

To get fine patterns of ArF photoresist without pattern collapse, we studied the relation between optical property of pattern image and adhesion of photoresist pattern. In concern of the type of photo mask, we found that using attenuated phase shift mask could make experimental small resolution limit beyond the estimation by simulation. About ARC substrate structure (inorganic ARL/ oxide/ polySi), it was important not only to optimize the reflectivity, but also to optimize the phase of reflectance. Photoresist was easy to collapse when the phase of reflectance at the interface between photoresist and inorganic ARL is near the 0 degree, although the reflectivity was set below 1%. In order to change the phase of reflectance, the film thickness of oxide was varied. In the observation of photoresist profile, bottom profile was changed similar to simulation. In the case of organic bottom ARC, we could not observe the effect of the phase.

Simple Method For Resist CD Prediction

A simple calculation method which predicts resist CD with high precision is proposed. To simplify the formalism, image intensity profile and dissolution rate of resist are approximated with a linear and an exponential function, respectively. With this simplification, the resist edge displacement is expressed with a primitive formula. The method is evaluated by comparing experiments and calculations, and the effectiveness of the method is confirmed.