Physical description of lithographic processes: correlation between bake conditions and photoresist contrast

Paniez, Patrick Jean; Festes, G.; Chollet, Jean-Paul E.

doi:10.1117/12.59773

Cited by 5 publications

(5 citation statements)

References 7 publications

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“…[17][18][19][20][21] Experimental schemes have also been devised to measure these parameters directly. [22][23][24][25][26] Typically, the concentration of inhibitor fluctuates throughout the thickness of the resist layer as well as laterally across the surface of the film. In addition, the optical absorption tends to vary over the time span of exposure.…”

Section: Multilevel Fabricationmentioning

confidence: 99%

Photoresist characterization and linearization procedure for the gray-scale fabrication of diffractive optical elements

2001

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We present a procedure for the characterization and the linearization of the photoresist response to UV exposure for application to the gray-scale fabrication of diffractive optical elements. A simple and reliable model is presented as part of the characterization procedure. Application to the fabrication of surface-relief diffractive optical elements is presented, and theoretical predictions are shown to agree well with experiments.

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Section: Multilevel Fabricationmentioning

confidence: 99%

Photoresist characterization and linearization procedure for the gray-scale fabrication of diffractive optical elements

2001

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“…S0013-4651(99)07-030-5 CCC: $7.00 © The Electrochemical Society, Inc. [5] where W, V, 0 , and s are, respectively, the mass, the volume, the initial density of the film, and the density of the solvent. As the softbaking proceeds, the film becomes more solidified and the diffusivity of solvent decreases accordingly.…”

Section: Modelingmentioning

confidence: 99%

“…Available results in the literature are simple; most of them, however, are experimentally oriented. Paniez et al 5 proposed a polymer relaxation mechanism to describe the softbaking of a novolak-based photoresist. Beauchemin et al 6 examined the influence of the residual solvent of a photoresist film after spincoating on its dissolution and thermal behaviors.…”

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confidence: 99%

Mathematical Simulation of Soft Baking in Photoresist Processing

Hsu

Huang

Tsengb

2000

J. Electrochem. Soc.

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The soft‐baking procedure in photoresist processing is investigated theoretically. A Landau transformation coupled with a finite-difference scheme is adopted to solving the moving‐boundary problem under consideration. The experimental data of Shipley SPR510LA, m-p cresol novolak, poly(methyl methacrylate), Shipley UVIII, and Shipley SNR200 photoresists reported in the literature are analyzed to justify the applicability of the model derived. We show that the concentration dependence of the diffusivity of solvent can have a significant influence on the soft‐baking procedure. The rate of transfer of solvent is controlled by the molecular diffusion of solvent in a film. © 2000 The Electrochemical Society. All rights reserved.

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“…Although the baking mechanism of coated solution has been widely studied, [7][8][9][10] soft-baking of PR in microelectronics is reported only in recent years. [11][12][13][14][15] Baking involves three steps in series: the diffusion of solvent to the film-gas interface, the evaporation of solvent, and the transport of solvent vapor to bulk gas phase. Hence, the physical parameters governing the baking process are the diffusion coefficient of solvent in thin film, the mass-transfer coefficient of solvent in the film-gas interface, the baking temperature, and the baking time.…”

mentioning

confidence: 99%

“…Hence, the physical parameters governing the baking process are the diffusion coefficient of solvent in thin film, the mass-transfer coefficient of solvent in the film-gas interface, the baking temperature, and the baking time. Paniez et al 11 proposed a relaxation time model for the temporal variation of resist thickness during soft-baking of photoresists. A linear relation between the thickness and the logarithm of time was obtained.…”

mentioning

confidence: 99%

Theoretical Analysis of the Baking Process in Two Polymer/Solvent Systems: PMMA/Anisole and PMDA-ODA/NMP

Lin

Chen

2001

J. Electrochem. Soc.

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Baking of polymer solutions is very important for preparing uniform thin films in microelectronics. In this study, a general theoretical analysis for baking was developed to predict the variation of polymer film thickness with baking temperature and time. The theoretical analysis result was justified by experimental results from poly͑methyl methacrylate͒ ͑PMMA͒/anisole and poly͑pyromellitic dianhydride-co-4,4Ј-oxydianiline͒ ͑PMDA-ODA͒ amic acid/n-methyl pyrrolidone ͑NMP͒ systems. The theoretical analysis included a fixed boundary problem with a temperature-dependent-only diffusion coefficient, and moving boundary problems based on the diffusion coefficient from the Fujita-Doolittle equation and the Vrentas-Duda equation, respectively. The simulated results showed that the modeling equations based on the moving boundary problem with the Vrentas-Duda equation successfully predicted the variation of film thickness in comparison with the other two models. The diffusion coefficient ͑D͒, mass-transfer coefficient (k c ), and Sherwood number ͑Sh͒ were used to explain the trend of the baking curves. In the cases of the PMMA/anisole system, the values of Sh increase significantly with increased baking time while the values of D show the opposite trend. This suggests that the baking mechanism has shifted from the evaporation-control mechanism to the diffusion-control mechanism. However, the values of Sh in the polyimide/NMP system are all larger than 15 because of the low diffusion coefficient of the solvent NMP. Hence, the transition of the evaporation-control to the diffusion-control no longer exists in the polymer/ solvent system with a high-boiling-point solvent. The model based on the moving boundary problem with the Vrentas-Duda equation simulates a wide range of Sh values and results in higher accuracy than the other two models.Baking is very important for preparing photoresists and spin-on dielectrics in microelectronics. 1,2 For example, the lithographic process in the manufacturing of integrated circuits ͑ICs͒ includes the following major steps: priming, spin-coating of photoresist ͑PR͒, soft-baking, exposure, postexposure baking, developing, and hard baking, etc. Soft-baking is used to control the free volume ͑or solvent content͒ of the spin-coated PR film by selection of baking parameters, i.e., baking temperature and time. The photochemical reaction in the lithographic process largely depends on the diffusion ability of a photoactive compound in the PR film. 3,4 Hence, control of the free volume inside the PR film by soft-baking before exposure significantly affects the quality of the lithography, including photospeed, 3 contamination, 5 contrast, 6 and critical dimension variation. 6 Furthermore, soft-baking also controls mechanical properties since the adhesion of a PR film to a substrate is affected by the solvent content inside the PR film. 3 For spin-on dielectrics, multistep baking is required to control the possible voids in the film or film uniformity. Hence, understanding of the baking mechanism is ve...

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Physical description of lithographic processes: correlation between bake conditions and photoresist contrast

Cited by 5 publications

References 7 publications

Photoresist characterization and linearization procedure for the gray-scale fabrication of diffractive optical elements

Photoresist characterization and linearization procedure for the gray-scale fabrication of diffractive optical elements

Mathematical Simulation of Soft Baking in Photoresist Processing

Theoretical Analysis of the Baking Process in Two Polymer/Solvent Systems: PMMA/Anisole and PMDA-ODA/NMP

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