Medhat A. Toukhy

Second-generation radiation sensitive developable bottom anti-reflective coatings (DBARC) and implant resists approaches for 193-nm lithography

We will discuss our approach towards a second generation radiation sensitive developable bottom antireflective coating (DBARCs) for 193 nm. We will show imaging results (1:1 L/S features down to 140 nm) for some first generation implant resist material based upon a fluorinated resins and also show relative implant resistance of these first generation fluorinated resists towards As implantation (15 KeV at 5x1015 dose with 20 x 10-4 amp). Also, discussed will be a second generation of implant resists based on a non-fluorinated resins. Surprisingly, we found that the nonfluorinated materials gave better implant resistance (~2-3 X1011 atoms/cm2) despite the higher atomic number of fluorine compared to hydrogen in the fluorinated implant materials (~2-5X1012 atoms/cm2). Finally, we will give an update on the lithographic performance of this second generation of implant resists.

Manipulation of chemically amplified resist dissolution rate behavior for improved performance

The properties of the PAG and the type of the blocking group combined with the process temperature affect the slope of the dissolution rate curves within the critical lithographic area of the curve significantly. The location of the steepest dissolution rate switching and the photospeed of the resist are primarily a function of the PAG type and base ratio. The resist inhibition is largely influenced by the blocking level of the polymer. The total phenolic (OH) content of de-blocked polyhydroxystyrene (PHS) based resist systems is the only parameter that affects their maximum dissolution rate (Rmax).

Chemically amplified hybrid resist platform for i-line applications

Three polymer platforms based on acid labile blocked novolaks were investigated. The first, blended with Polyhydroxystyrene/ t-butylacrylate (PHSC), produced incompatible blends for the most part. Compatible blends were obtained for the second platform by reacting novolak and PHSC together with alkylvinylether, which was optimized for resist performance on Cu substrate at and below 10 μm film thickness. The third platform, based on a modified novolak resin, achieved greater than 5 aspect ratio in 25 μm thick films.

All i-line lift-off T-gate process and materials

An all i-line 0.22 um T-gate process is demonstrated. A resist structure suitable for metal deposition and lift-off is constructed sequentially with two different resist materials. The lithographic process is described in details in this paper.

Large area interposer lithography

Large area silicon or glass interposers may exceed the maximum imaging field of step and repeat lithography tools. This paper discusses the lithographic process used to create a large area interposer on a stepper by the combination of multiple subfield exposures. Overlay metrology structures are used to confirm the relative placement of the subfields to construct the interposer. Routing lines from 1.5 to 4.0 μm in width are evaluated to measure critical dimension (CD) control where the lines cross the subfield boundaries. CD metrology at the bottom and top of the photoresist is performed using a top down CD-SEM. Finally large area test interposers are patterned using two subfields on a 1X stepper and processed through a Cu electroplating module for detailed characterization. The CD control of routing lines as they cross the subfield boundary can be optimized by using a shaped or tapered line end design. Lithography simulation using Prolith modeling software by KLA-Tencor is matched to experimental results and then used to evaluate performance of various line end designs. Larger latitude for overlap error was observed for the tapered line end compared to the standard square line end. The experimental and modeled results in this study show the capability of using stepper lithography to produce large area interposers with 1.5 μm I/O routing line dimensions.

Radiation sensitive developable bottom anti-reflective coatings (DBARC) for 193nm lithography: first generation

A first generation DBARC applicable for 1st minimum 193nm lithography is described in this paper. The polymer used in this DBARC is insoluble in the casting solvent of the resist, which is propyleneglycolmonomethyletheracetate (PGMEA). Photo acid generator (PAG) and base extractions from the DBARC coating by the resist casting solvent were examined by the DBARC dissolution rates in the developer, before and after solvent treatments. Although the resist and the DBARC do not appear to intermix, strong interaction between the two is evident by their lithographic performance and dissolution rate study.

Chemically amplified thick film i-line positive resist for electroplating and redistribution applications

Adapting chemically amplified (CA) resist technology to thick film applications is demonstrated in this paper over a wide range of thicknesses and types of substrates. Substantial performance differences were observed over copper (Cu) substrates compared to silicon (Si). These differences are attributed to different photo acid generator (PAG) distribution in the resist depth influenced by its structure and the nature of the substrate. Optimized resist formulations were developed to provide acceptable performance on Cu wafers. A family of new chemically amplified thick film resist products is being introduced to the market. This technology offers significant advantages in throughput and performance over conventional novolak / diazonaphthoquinone (DNQ) products at a competitive cost.

Effect of developer normality on the resist dissolution rate and performance

Process simulation is necessary to investigate possible enhancements of some selective resist performance properties as a result of changes in the developer concentration. Accurate dissolution parameters are needed for different developer normalities to simulate their effect on the resist dissolution rates. Only qualitative similarities are observed in the dissolution behavior of similar chemistry based resist as a function of developer normalities. Quantitative differences in the dissolution rates and curve shapes are detected between resist based on different chemistries. No single universal dissolution model capable of describing the behavior of all different resists was found. However, individual resist dissolution/developer concentration models can be constructed.

Design and process of a new DUV ARCH3 resist

A new concept for polymer design is described which can extend the utility of acetal chemistry in the development of advanced chemically amplified deep-UV resists for KrF excimer lasers. Many acetal blocked polymers only impart marginal thermal flow properties to the photoresist matrix. This polymer design concept can overcome this thermal flow deficiency and also improve photoresist contrast and resolution. This concept involves the formation of crosslinked acetal polymers from linear acetal blocked polymers via acid labile crosslinks. The resulting branched polymers have increased Tg and therefore impart improved thermal flow properties to the resist. Furthermore, the acid lability of the crosslinks results in a large molecular weight differential between exposed and unexposed areas of the resist leading to larger dissolution rate discrimination between exposed and unexposed regions. The ultimate result is improved resolution capability of the resist system. This design concept has been incorporated into the ARCH3 resist series.

Combinatorial process optimization for negative photo-imageable spin-on dielectrics and investigation of post-apply bake and post-exposure bake interactions

Patternable dielectric materials were developed and introduced to reduce semiconductor manufacturing complexity and cost of ownership (CoO). However, the bestowed dual functionalities of photo-imageable spin-on dielectrics (PSOD) put great challenges on the material design and development. In this work, we investigated the combinatorial process optimization for the negative-tone PSOD lithography by employing the Temperature Gradient Plate (TGP) technique which significantly reduced the numbers of wafers processed and minimized the developmental time. We demonstrated that this TGP combinatorial is very efficient at evaluating the effects and interactions of several independent variables such as post-apply bake (PAB) and post-exposure bake (PEB). Unlike most of the conventional photoresists, PAB turned out to have a great effect on the PSOD pattern profiles. Based on our extensive investigation, we observed great correlation between PAB and PEB processes. In this paper, we will discuss the variation of pattern profiles as a matrix of PAB and PEB and propose two possible cross-linking mechanisms for the PSOD materials to explain the unusual experimental results.