In our experiment for 0.15 micrometer contact hole, we used Water-soluble organic overcoating material (WASOOM) as a barrier layer. Since WASOOM is water soluble, after baking for resist flow, water rinse will remove it completely. The key point of resist flow technique is to reduce overhang, in other words, reducing thermal stress at the top and bottom of resist pattern by WASOOM can lead to well-controlled DICD. Since WASOOM is water soluble and very compatible with resist, during resist flow, it is assumed that it will be acting as a barrier layer so that overhang should be reduced. In this paper we will describe below 0.2 micrometer contact hole pattern without overhang profile, well controlled DICD and fine etch profile. And also 0.15 micrometer contact hole patterning method will be described with half tone + resist flow by WASOOM. And also we will describe the application of SOG (Spin On Glass) for removing top flare after resist baking.
Silicon oxynitride film on Silicon Nitride film as an inorganic ARC has been investigated for the tighter critical dimension control. Use of SiON film as an inorganic ARC on silicon nitride film led to the better CD uniformity control reducing substrate dependency issue. Resist profiles on SiON have also been investigated on BPTEOS and on silicon nitride films. Footing on BPTEOS was removed completely by adding SiON film. It is found that SiON showed storage time limit after deposition. Five days after deposition, it showed footing profile. There must be some unknown chemistry to explain that phenomenon. Oxygen plasma applied onto the 5 dayed SiON film showed foot free profile. In the paper we will describe the CD control on Nitride by using SiON as an inorganic ARC, substrate dependence and storage time limit of SiON film.
The effect of mask critical dimension (CD) error for binary mask and attenuated phase shift mask (PSM) are investigated by simulation and experimental based data. For the large features, mask error factor (MEF) is approximately unit. But as the CD is closed to the resolution limit, the MEF value is rapidly increased. The MEF was dependent on the contact density. For example, dense contact has larger MEF value than isolated contact. Attenuated PSM has smaller MEF value comparing with binary mask because it is applied the positive mask bias in order to reduce the sidelobe printing. The sensitivity of mask CD error for NA and sigma variation was different from the contact density. For the isolated contact, MEF value was almost independent on the sigma value. However, the MEF was improved by high NA lines at the resolution limits both for the isolated and for the dense contact. According to these data, the mask CD control budget for the sub-quarter micron contact was considered.
In the experiment, various ion species are implanted to the developed images to improve etching and thermal flow resistance of Deep UV chemically amplified resists. Among various ion species, it is found that Argon ion did not affect the photoresist thickness and critical dimension after ion implantation. Much improved results could be obtained. Untreated contact hole patterns start flowing on 120 degrees C and finally are filled up on 130 degrees C with noticeable film shrinkage. On the other hand, Argon implanted contact hole patterns are standing still up to 170 degrees C without any thickness shrinkage and CD variation. Application of higher temperature results in the protrusions at the bottom of the resist profiles. Pattern deformation after dry etching process can be prevented. Cross-sectional SEM micrographs of the ion implanted contact hole patterns show clear interface between the hardened and the unhardened. SIMS analysis of the ion implanted photoresists reveal the presence of the ions at the surface of the substrate, not in the resist. Detailed mechanistic study will be discussed. Application of this process to bilayer resist process and a new antireflective layer has been tried and evaluated. And also the effects of accelerating energy and ion dose on reflective index of carbonized layer have been investigated. RI analysis shows the change of n and k value according to energy and ion dose. It can be speculated that the transparent matrix resin changed to highly absorbing amorphous carbon based materials. It is quite sure for that the n and k value can be controlled for the application of bottom antireflective layer. This new ARC material is very compatible to resist and est to strip, compared to conventional Organic Bottom ARC material. Thickness optimization for the ARC, application to real device and etching characteristics are under development in our lab.
An attenuated phase-shifting mask is favorable lithography technique for enhancing the depth-of-focus for isolated hole. However, it is restricted by sidelobe printing at dense array holes. To reduce the sidelobe printing, various methods such as surface insoluble layer, add an auxiliary hole, and optimization of NA and sigma were investigated. The method of surface insoluble layer was not effective for the dense array holes and CD uniformity was not improved. The method that adds an auxiliary hole at sidelobe position of highly dense array pattern can reduce the sidelobe printing completely, but mask CD and mask defect inspection as well as automatic layout of auxiliary holes for nonrepeating patterns in periphery area will be issued. In order to optimize the NA and sigma value, DOF and sidelobe printing were considered. Also CD control is studied by considering the CD linearity and optical proximity correction (OPC) as mask print bias is applied. Design rule for attPSM was suggested at optimized and fixed conditions.
One more study for pushing resolution limit down below industry agreed optical limit was performed. It was pursued for practical application, not limited to experimental purpose only. The first work was concentrated on studying how much we could lower the resolution and improve the process latitude of dense lines, which was thought as the most critical one. OAI and BARC played a role for that purpose, were expected to improve DOF as much as 105% and 15%, compared to conventional illumination and non-BARC process, respectively. It was also known from simulation that mask biasing was important to maximize DOF for dense and isolated line. It could be used to reduce CD and resist profile difference of dense and isolated features as well. Ultimate resolution was only possible by very high contrast resist. All the efforts in this work achieved quarter micron i-line process which has 1.2 micrometer DOF for dense lines, 0.8 micrometer overlap DOF and 10% exposure latitude both for dense and isolated features.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.