§
Luxuse
Patent Intelligence
Sign In
← Back to Patent Explorer
EP0489540A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

Phase-shifting lithographic masks with improved resolution

Assignee: AT&T Inc
•
Filing: 1991-11-28
•
Granted: —
•
Expires: 2011-11-28
📄 Original PDF 🌐 Google Patents 🔄 Sync Now

Abstract

Abstract In order to print an isolated feature having a width W in a photoresist layer (101) using an optical radiation imaging system (200) whose lateral magnification is equal to m , a phase-shifting mask is used having a corresponding isolated feature. This corresponding isolated feature has a central portion (C) having a refractive index n₁ and a thickness t₁, and a peripheral portion (B) having a refractive index n₂ and a thickness t₂, such that the phase-shift φ = 2π(n₂t₂ - n₁t₁)/λ of the central portion relative to the peripheral portion is equal to π radian. The width C of the central portion advantageously is selected such that mC/W is equal to at least 1.2, and preferably greater than 1.5, rather than unity.

Inventors

  • 👤 Joseph G. Garofalo
  • 👤 Robert Louis Kostelak, Jr.
  • 👤 Sheila Vaidya

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-01 00:19
CPC Classifications
G; G03; G03F; G03F1/00; G03F1/26; G03F1/29; G03F7/00; G03F7/20; G03F7/2002; G03F7/70; G03F7/70216; G03F7/70283

Claims Analysis

Total Claims: 7
Claim 1
Independent Claim 114 words
A method for printing in a photoresist layer (101) an isolated feature having a width W, using an optical focusing system (200) having a lateral magnification m which focuses onto the photoresist layer (101) the optical radiation emanating from an isolated phase-shifting mask feature located in a mask (103) comprising the step of directing the optical radiation onto the mask (103), the phase-shifting mask feature having a central portion of width C and having a peripheral portion which imparts a phase shift to the radiation propagating therethrough which is different from the phase shift imparted to the radiation by the central portion, Characterized in that the ratio mC/W is equal to at least 1.2.
Claim 2
Dependent Claim 38 words
The method of claim 1 characterized further in that the central and peripheral portions have respective thicknesses and refractive indices that in propagating through these respective portions the optical radiation undergoes a relative phase shift of π radian.
Claim 3
Dependent Claim 18 words
The method of claim 2 characterized further in that the ratio, mC/W, is equal to at least 1.5.
Claim 4
Dependent Claim 17 words
The method of claim 2 characterized further in that the ratio is equal to at least 1.6.
Claim 5
Dependent Claim 18 words
The method of claim 1 characterized further in that the ratio, mC/W, is equal to at least 1.3.
Claim 6
Dependent Claim 17 words
The method of claim 1 characterized further in that the ratio is equal to at least 1.5.
Claim 7
Dependent Claim 17 words
The method of claim 1 characterized further in that the ratio is equal to at least 1.6.

References Cited (Backward Citations)

No citation records indexed.

USPTO Annuity & Maintenance Windows

Maintenance schedule is calculated for granted US utility patents.

Assigned Categories & Tags

No categories assigned to this patent yet.

Assign Category Tag