Linewidth control in projection lithography using a multilayer resist process

O'Toole, Michael M.; Liu, E.D.; Chang, M. S.

doi:10.1109/t-ed.1981.20622

Cited by 17 publications

(8 citation statements)

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“…Modeling studies (10) that have attempted to predict the performance improvement of lightly dyed resists fail to include alternate exposure paths and only assume light paths normal to the resist surface. Dyed resist systems, however, introduce exposure and resist profile penalties and produce linewidth deviations that are more sensitive to bulk thickness changes (3).…”

Section: Resultsmentioning

confidence: 99%

“…These include: resist thickness changes, standing wave effects within the resist film, sidewall reflections, and focus differences between the top and bottom of the .step. Standing wave induced dimensional deviations appear to present the most severe difficulties (1)(2)(3). These interferometric effects produce oscillating linewidth deviations as a function of resist thickness and are particularly prominent on highly reflective substrates (>50%).…”

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confidence: 99%

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Contour Modifiers for Optical Lithography

White

1988

J. Electrochem. Soc.

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The shrinking design rules of integrated circuits require precisely controlled patterned resist linewidths with minireal dimensional deviations. In the presence of steps (topography) on the substrate, dimensional deviations greater than 0.5 ~m are not uncommon. Several factors contribute to dimensional deviations in positive resist films patterned on topography with optical lithography. These include: resist thickness changes, standing wave effects within the resist film, sidewall reflections, and focus differences between the top and bottom of the .step. Standing wave induced dimensional deviations appear to present the most severe difficulties (1-3). These interferometric effects produce oscillating linewidth deviations as a function of resist thickness and are particularly prominent on highly reflective substrates (>50%). The necking of the patterned resist line near the edge of a step has been termed "reflective notching." This reflective notching near the top edge of a step and ballooning near the bottom edge of a step have been largely attributed to a standing wave effect. In this work we discuss another factor that also contributes to "reflective notching" and propose a new procedure for minimizing its effects. In some cases the latitude of the resist process can be improved and deviations in linewidth at critical regions of the device layout minimized with this procedure. ExperimentalAlthough standing wave effects certainly play an important role in resist dimensional deviations from optical lithography, our experiments suggest the origin of reflective notching and ballooning arise in part from a different and more complicated mechanism. Figure 1 shows a schematic of the contour of a spun-on resist film coating a step and the resulting light ray paths. The curvature of the resist contour changes the direction of incident light so that it no longer travels perpendicular to the substrate surface. Furthermore, near the top of the step several different paths through the resist film can expose the same point on the substrate surface or within the thickness of the resist film. The curvature of the contour acts as a concave lens near the top edge of a step to focus the light and as a convex lens to diffuse the light near the bottom edge of the step. The focused light tends to produce a "reflective notch" and the diffuse light a "ballooned" linewidth.To correct these exposure anomalies a spun-on, contour modifier overcoat is proposed to reduce the curvature of the contour at the air-polymer film interface. The overcoat layer is a water soluble polymer and is specifically designed to planarize the surface. Similar layers have been overcoated on resist films for other applications. Polyvinylalcohol, PVA, layers have been coated on x-ray resists to prevent oxygen from penetrating into the resist film (4). PVA or polyvinylpyrrolidone, PVP, layers have also been proposed as lubricants for resist layers to be used in contact printing (5). However, to obtain suitable planarization properties some special requirements a...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Contour Modifiers for Optical Lithography

White

1988

J. Electrochem. Soc.

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“…Dyed planarizing layer.--On reflective substrates, to i m p r o v e linewidth control and interference from reflective n o t c h i n g (13), a near UV actinic absorbing dye was added to the t e r p o l y m e r planarizing u n d e r l a y e r and a p r e b a k e condition for the dyed t e r p o l y m e r was chosen for no dye loss and to retain good contrast. The effectiveness of the dyed planarizing layer in controlling refleetivity effects can be seen in Fig.…”

Section: Resultsmentioning

confidence: 99%

Aqueous Processable Portable Conformable Mask (PCM) for Submicron Lithography

Lyons

Moreau

1988

J. Electrochem. Soc.

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To overcome the interfacial residues of the novolak resist/polymethylmethacrylate portable conformable mask (PCM), an underlayer of a terpolymer of poly (methylmethacrylate methacrylic acid‐methacrylic acid anhydride) was used in conjunction with an aqueous alkaline developer. The results reported show the submicron resolution capability of a simple capped process which uses a low toxicity aqueous developer which overcomes the interfacial scumming of the two resist layers in the novolak/PMMA‐PCM. In addition, the thermal stability of the underlayer is enhanced by the copolymerization of cyclic anhydride groups into the PMMA polymer structure.

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“…4). The normalized exposure latitude (NL) for the 1µm nominal linewidth may be expressed as NL = 100 x dose /nominal dose OLW (3) which is the inverse slope of the curves in Fig. 11.…”

Section: Normalized Exposure Latitudementioning

confidence: 99%

“…One method of solving this problem is the post-exposure bake [1]. Another approach is to add an absorbing dye to the patterning material [2,3,4].…”

Section: Introductionmentioning

confidence: 99%

A Lithographic Study of Photoresists Containing a Base Soluble Dye

Cagan¹,

Blanco²,

Wise³

et al. 1989

Advances in Resist Technology and Processing VI

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This paper examines the performance of a specific family of dyed resists. The effect of dye concentration on the line profiles of a homologous series of positive photoresists is studied. Usable images are obtained with dye concentrations of 0 %, 0.4 %, and 0.6% (percentage of the formulation). Both standard softbake or a softbake plus post-exposure bake (PEB) processes are used. Resist linewidths and cross -sections are measured on substrates that are representative of those encountered on integrated circuits. Optical exposure and develop simulation parameters (two developers) for this family of resists are also extracted.

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Linewidth control in projection lithography using a multilayer resist process

Cited by 17 publications

References 0 publications

Contour Modifiers for Optical Lithography

Contour Modifiers for Optical Lithography

Aqueous Processable Portable Conformable Mask (PCM) for Submicron Lithography

A Lithographic Study of Photoresists Containing a Base Soluble Dye

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