US 6569761

Patent Overview — US 6,569,761 B2

Title: Method for shrinking critical dimension

Source: https://patents.google.com/patent/US6569761/en

Bibliographic data (as supplied): Inventor Ching-Yu Chang; original and current assignee Macronix International Co., Ltd.; application US09/903,667; filed 2001-07-13; priority date 2000-11-09; published as US20020055252A1 (2002-05-09); granted 2003-05-27; anticipated expiration 2021-07-13; status "Expired – Lifetime" (the source notes legal status is an assumption, not a legal conclusion).

Purpose: The invention addresses shrinking critical dimension (CD) — the smallest line width obtainable in a photolithography process. The text states CD shrinkage is "an important task," and describes three prior techniques (lithography, photoresist reflow, polymer deposition) along with drawbacks: reflow's thermal process is hard to control and resist may flow into the topographic profile; polymer deposition affects later etching and uniform polymer distribution is difficult to secure.

Plain-language scope: A photosensitive layer (positive or negative photoresist; positive in the embodiment) is spin-coated on a substrate. A patterned reticle — binary intensity mask (BIM) or phase shift mask (PSM), e.g., Levenson alternative or half-tone PSM, made of quartz glass with opaque chromium/chromium oxide — is provided and aligned. An over-exposure process is performed, supplying energy exceeding the optimal energy so excess energy diffuses peripherally, enlarging the exposed region and reducing the unexposed region. After development, a sacrificial layer is formed over the substrate and patterned photosensitive layer, anisotropically etched to expose the photosensitive layer, then the photosensitive layer is removed, reverse-transferring the pattern to the sacrificial layer. The reverse-transferred line width in the sacrificial layer is thereby reduced. Figures 1–6 illustrate these steps, with FIG. 6 showing supplied energy versus exposed-region dimension.

What the excerpt does not establish: It does not provide the full claim text, full specification, drawings' details, prosecution history, or any prior-art citations. It does not establish validity, enforceability, litigation, or ownership changes — and no such research was performed. Terms like "about 365 nm (I-line)," "248 nm," "193 nm," "0.3 µm," "0.2 µm," and "0.18 µm" appear as stated in the source, without independent verification.