Lithography Mirror Fluid Channel Geometry Control

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Solution Overview

Problem

In semiconductor lithography, the varying distances between the optically active areas and temperature control channels in mirrors lead to uneven heat dissipation, affecting imaging quality, particularly in extreme ultraviolet projection exposure apparatuses.

Innovation Solution

A method involving a blank made of low-expansion materials like Zerodur or ULE, where fluid channels are introduced at a constant distance from the optical side, allowing for precise shaping onto a mold to maintain consistent heat conduction and geometry, ensuring uniform heat dissipation and improved imaging quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If drilling is used to produce cutouts for temperature-regulated water flow, then fluid channels can be introduced into the mirror, but the bore holes can only be driven straight through the mirror material causing varying distances from the optically active areas, leading to different temperature gradients and uneven heat dissipation

Engineering Contradiction:

Improveease of manufactureVSAvoidmanufacturing precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

Fluid channels are introduced into the blank before the shaping process. The blank is heated and shaped onto a mold in a state that allows straightforward channel introduction (e.g., when the blank is still relatively flat or accessible), and then the blank is shaped into its final curved mirror geometry. This preliminary action avoids the need to drill through curved surfaces later, enabling straight channel paths that maintain consistent distances from the optically active areas.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The blank is heated to a temperature where it becomes more formable and can be shaped onto the mold. This parameter change (temperature increase) allows the blank to be deformed into the final mirror geometry while the fluid channels remain in positions that maintain consistent distances from the optically active areas, achieving both ease of manufacture and manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If the blank is heated and shaped onto a mold to achieve precise geometry, then the optically active areas and fluid channels maintain consistent distances, but the blank must be heated to high temperatures requiring careful control

Engineering Contradiction:

Improvemanufacturing precisionVSAvoidtemperature

Core Design Contradiction:

Manufacturing precisionVSTemperature

Solution Approach 1:

The blank is heated to a temperature where it undergoes a phase transition or significant softening, making it formable and allowing it to be shaped onto the mold. This controlled phase transition enables the blank to adapt to the mold's geometry, ensuring that fluid channels maintain consistent distances from optically active areas while the heating is limited to the minimum necessary for formability.

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The blank is heated to exploit thermal expansion and increased formability, allowing it to be shaped onto the mold. The heating is controlled to achieve the necessary geometric precision for consistent channel distances without excessive temperature increases, and the blank is then cooled to lock in the precise geometry.

Inventive Principle:

Principle #37Thermal expansion

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The method ensures consistent heat conduction and reduced thermal gradients, enhancing the imaging quality of optical elements by maintaining the geometry of fluid channels and optically active areas, thereby improving the performance of semiconductor lithography.

Implementation Method 1

The shaping of the blank onto the mold can be implemented by heating the blank into a temperature range below the glass transition temperature of the utilized material

Methodology Applied

Scientific EffectGlass transition:

Implementation Method 2

The blank is heated before it is shaped onto the mold... the mold can already have a geometry that corresponds to the geometry of the mirror surface that is subsequently used optically

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

The mirrors comprise cutouts through which temperature-regulated water flows and which thereby dissipate the heat from the optically active surface

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS20230288662A1Method for producing a main body of an optical element for semiconductor lithography, and main body of an optical element for semiconductor lithography

Publication Date: 2023.09.14 CARL ZEISS SMT GMBH

AI summary

A method for producing a main body (33) of an optical element for semiconductor lithography includes: —producing a blank (32), —introducing at least one fluid channel (36.x) into the blank (32), then —producing the main body (33) by shaping the blank (32) onto a mold (42). Furthermore, the disclosure describes a main body (33) of an optical element that includes at least one fluid channel (36.x), the fluid channel (36.x) being embodied such that the distance between the fluid channel (36.x) and the surface (40) of the main body (33) provided for an optically active area (41) varies by less than 1 mm, preferably less than 0.1 mm and particularly preferably less than 0.02 mm.