<title>Real-time on-wafer evaluation of contaminant-induced defects from resist processing</title>

Abstract

In this paper we present a new non-contact, non-destructive method for real-time evaluation of both surface and interface metallic contamination from resists. The method allows for independent testing at the completion of a coat/ash or ash/removal/clean steps in processing. Using a standard 1.2i resist in both as-received and intentionally doped versions wherein alkaline and transition metals such as K, Fe, Cr, and Cu were added to the initial solution, we demonstrate that at both these crucial steps in resist processing important electrical and material parameters such as bulk Fe concentratior, minority carrier diffusion length, relative surface recombination velocity, and surface charge can be detected directly on-a processed test wafer with no electrical test structures using a combination of low and high injection level surface photovoltage.. Since most production fabs only test for residual particles in-line, or rely on expensive, time-consuming analytical techniques such as AAS, DLTS, or TXRF to evaluate contaminant metals, this approach offers a faster and a more economical way to control this problem.

Surface photovoltage phenomena: theory, experiment, and applications

“…Thus, ( may be found from the inverse of characteristic knees in the SPV versus frequency curve. This approach has been used successfully with both saturated [509], [586],[595±601] and non-saturated [294,295] SPV.…”

“…(5.18) show that if the surface band-bending is known, S and L may be extracted simultaneously, from the slope and intercept of a Goodman plot, respectively. This approach has indeed been used successfully in several studies [12,428,506,509]. Speci®cally, Hoff et al used scanning SPV and work function measurements for simultaneous wafer-scale maps of L, [Fe], V 0 s , Q ins , and S, thus combining several approaches discussed above for comprehensive characterization of surface and bulk properties of Si wafers [506].…”

“…The most common approach for quantitative extraction of S relies on measuring Goodman plots (discussed in Section 5.1) [12,232,233,428,506,509,628,704,705]. The value of S affects the slope of the Goodman plot used to extract L (in both the constant SPV and the linear SPV approaches), due to the S DaL À1 coef®cient in the dependence of nw on I (Eq.…”

Migration-Adsorption Mechanism of Metallic Impurities out of Chemically Amplified Photoresist onto Silicon-Based Substrates

“…If the chemical reaction reaches equilibrium, the equilibrium constant (K) for the reaction can be expressed as [8] where [H ϩ ] and [M nϩ ] are volume concentrations for the generated acid and metallic impurity in the interface region, while SiOM (nϪ1)ϩ and SiOH are surface concentrations. From Eq.…”

“…Many lithographic models have been developed and applied for the photoresist profile simulation, [4][5][6] however, the effects of impurity migration in the chemically amplified photoresist are seldom reported. Brown and co-workers 7,8 intentionally contaminated the photoresist with various metals for the evaluation of metal-induced electrical effect. After the lithographic process and photoresist ashing, they applied the optical surface photovoltage method to evaluate the diffusion length of the minority carriers.…”