Yoshihiko Hirai

Half-Micron KrF Excimer Laser Stepper Lithography With New Resist And Water-Soluble Contrast Enhanced Materials

Half-micron patterns have been fabricated using a newly developed high-speed KrF excimer laser stepper system with new resist, NOEL (Novolak based resist for Excimer Laser), and water-soluble contrast enhanced material, WSP-EX.

Self-aligned phase shifting mask for contact hole fabrication

Abstract A new fabrication process and pattern transfer characteristics of a self-aligned phase shifting mask have been described. The use of the self-aligned phase shifting mask improves the resolution and the depth of focus for contact hole patterns. However, it does not improve the resolution for line and space patterns.

Improved Bilayer Resist System Using Contrast-Enhanced Lithography With Water-Soluble Photopolymer

A new water-soluble contract enhanced material, WSP (Water-soluble Photopolymer), has been developed. The WSP is composed of a mainpolymer and a photobleachable reagents. The mainpolymer is a water-soluble polymer mixed with pullulan (refined through biotechnological process) and polyvinyl-pyrolidone (PVP). The photo-bleachable reagent is of a diazonium compound gorup. The introduction of the mainpolymer and photobleach-able reagent mixture has improved filmity, gas transparency, photobleaching characteristics and solubility in alkaline which are essential to the device fabrication. Submicron photoresist patterns are successfully fabricated by a simple sequence of photolithography process. The WSP layer has been applied to the bilayer resist system--deep-UV portable conformable masking (PCM)--that is not affected by VLSIs topography, and is able to fabricate highly accurate pattern. The aqueous developable layer, PMGI, with high organic solvent resistance is used in the bottom layer. Therefore, no interfacial mixing with conventional positive resist top layer is observed. Furthermore, deep-UV exposure method has been used for the KrF excimer laser optical system in order to increase high throughput. From the experiments, it has been confirmed that good resist transfer profile can be realized by the use of WSP, and that the submicron resist patterns with high aspect-ratio can be developed on the nonplaner wafer with steps of up to 41m by the combination of the WSP with the PCM system. By this technology, has been improved the weak point: variation in the line width due to the thickness of contrast-enhanced layer when the CEL technology is applied, and dependency of both the finished resist profile and the line-width accuracy on the thickness of the top layer resist when the PCM system is adopted.

Process Modeling for Photoresist Development and Design of DLR/sd (Double-Layer Resist by a Single Development) Process

This paper describes a new simple process model for photoresist development. The model includes the consideration of chemical reactions between a photoresist and a developer, and takes the developer concentration dependence into account. The model is applied to the design of practical photo-lithography processes to determine development conditions. Through the introduction of the model-based lithographic simulations, the multilayer resist process has been successfully designed and has obtained satisfactory patterns.

New Pattern Transfer Technology For G-line Lithography

New pattern transfer technology for G-line lithography has been developed. G-line lithography using steppers have become the main tool in the production of submicron design rule VLSI. To adapt G-line lithography for half-micron design rule VLSI production, we have developed new and simple pattern transfer technology. High contrast patterns and resolution were obtained in this technology. This was achieved by using a soak process to treat the resist surface before exposure in the conventional resist process. The surface treatment was done by dipping the wafer in a solution of tetramethyl ammonium hydroxide(TMAH) rather than a chlorobenzene solution. And also, we combined with new pattern transfer technology with CEL (contrast enhanced lithography) to control the aerial image. The resists were imaged by using G-line steppers with NA value of 0.54 and 0.45. The positive photoresists used were S1400(Shipley), TSMR-Vl(Tokyo Ohka) and TSMR-CRB2(Tokyo Ohka dyed resist). A conventional developer for positive photoresist was used for the surface treatment by TMAH alkaline solution. In this process, we have evaluated the baking step either before or after the image exposure in the conventional process in order to compare pattern profiles.

I-Line Lithography Using A New Water-Soluble Contrast Enhancing Material

I-line lithography using contrast enhanced lithography (CEL) has been developed. With this technology, we used a newly-developed water-soluble contrast enhancing material. This material consists of p-morpholinobenzene diazonium chloride zinc chloride salt, poly(p-styrene sulfonic acid) and water. P-morpholinobenzene diazonium chloride zinc chloride salts absorption peak is at around 365 nm. It also has high solubility in water and has excellent photobleaching characteristics. The poly(p-styrene sulfonic acid) as a matrix polymer prevents degradation of the diazonium salt in water, so it makes possible the long-term stability of the water-soluble contrast enhancing material. This lithography is capable of 0.5-μm pattern fabrication and it is convinced to be the major lithographic technology for 16 mega-bits DRAM production.