晶片光刻胶处理系统

In this work the application of a new generation of phase-fluid stripping solutions (intelligent fluid®) to a variety of semiconductor photoresists was studied. The unique water based intelligent fluid formulas used in these experiments were all VLSI grade, copper compatible and non-toxic. The first phase of experiments was to establish if there was a reaction with the photoresist type and intelligent fluid® formula within a reasonable time period, with the most promising combinations carried forward to phase two for in depth study. The follow-on experimental results demonstrate the optimal process parameters through variation of process temperature settings and the additions of megasonic acoustic energy. Photoresist stripping results were quantified though visual inspection and contact angle measurement.

Removal of photoresist materials (resist stripping) is very straightforward in theory, but can be difficult and complicated in practice. Classical methods have included SPM (sulfuric peroxide module) /piranha, ozone and UV ozone. Solvent based fluids such as n-methylpyrollidone (NMP), Acetone, Dimethylsulfoxide (DMSO) and Tetramethalammonium (TMAH) have all been applied to this process in various forms and combinations. Typically solvents have been combined with temperature or gases (1) to enhance throughput and reduce the damage caused by swelling in thick PR scenarios. Dynamic dispense systems have also been applied to the standard solvent combinations including aerosol sprays (2) and physical activation of the solvents through acoustic energy (3) to help reduce process times and damage induces through PR film swelling. Many dry and wet dry combinations have been implemented using various Plasma and CO2 combinations. All of the legacy methods include hazardous and toxic materials and/or high equipment expense as well as multi-step process control complexity. The stripping process becomes even more challenging by factors such as thick resist, crosslinked resist or sensitive metals or materials under the resist. This study was carried out In order to determine feasibility of the use of a unique phase-fluid based photoresist-stripper in commercial semiconductor resist removal process steps. Due to their highly dynamic inner structure, phase-fluids penetrate into the polymer network of photoresists and lift the material from the surface as opposed to the surface or boundary reaction of a solvent solution. (4) As these water-based stripping fluids are non-aggressive, non-toxic, and require no special handling, the ability to apply them to industry standard resists will result in a reduction of toxic and dangerous chemistries and the environmental impact of their disposal.

This work reflects the combination of two distinct mechanisms applied to the photo resist stripping process, Phase-fluid (intelligent fluid®) and Single Wafer Megasonics. Phase-Fluid (intelligent fluid®) (4) intelligent fluids® consist of a heterogeneous mixture of two immiscible liquids that form a stable micro-emulsion. There is a balance established between the separation forces that keeps the components of the emulsion in constant motion or shape changing on a nano basis. When this very physically dynamic fluid is exposed to a film such as photo resist, the low surface energy allows for the penetration of very small gaps in the polymer surface, and the eventual forcing of the resist layer from the substrate. The film removal from the substrate is in the form of an actual physical lift-off separation and not a dissolution or etching of the film. Dilution of the Phase-Fluid is not proscribed as the equilibrium of the micro emulsion will become unbalanced and the forces will be neutralized immediately stopping any reaction. The intelligent fluid® formulas have proven to be very robust and stable in both storage time, temperature and shipment.

Single Wafer Megasonic 

The addition of megasonic range acoustic energy to wet semiconductor processes has been an industry standard for many years. The addition of megasonic acoustic energy at a certain amplitude induces cavitation in the process fluid. The imploding cavitations and subsequent micro shockwave extend the fluid exchange below the conventional surface flow boundary layer. This enables a rapid and uniform exchange of fluid directly at the wafer surface. The initial application of megasonic enhanced processing was targeted to particulate removal as the ability of the cavitation to move micro and nano particles to the macro stream and away from the substrate surface was critical to cleaning performance. Later applications of proximity Megasonics to photo resist and high aspect ratio processes in single wafer configurations added both uniformity and accelerated process times (increased throughput) (5). The rapid exchange of fluid below the conventional boundary layer accelerated the conventional etch/solvent/develop processes by eliminated the diffusion layer leading to much shorter process times and process fluid usage. As the intelligent fluids® act to physically penetrate access to the substrate film interface the additional forces of the cavitation implosions would assist in the exchange of fluid as well as enhancing the the lift-off of the resist layer below the standard boundary layer.