Rear Surface Coating for Wafer Planarization

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Solution Overview

Problem

In semiconductor manufacturing, minute scratches on the rear surface of wafers cause defocus issues during exposure processing due to uneven surface conditions, especially during etching treatments, which can lead to improper horizontal holding and subsequent defects in photolithography processes.

Innovation Solution

A substrate treatment method involving the formation of a coating film on the rear surface of the substrate before exposure processing, using a coating treatment apparatus with separate chambers for solution application and curing, ensures the surface is planarized, covering scratches and contaminants, allowing for horizontal holding during exposure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If etching treatment is performed with increased surface temperatures of the wafer and electrostatic chuck, then etching efficiency is improved, but minute scratches are generated on the rear surface of the wafer due to thermal expansion differences

Engineering Contradiction:

Improveetching efficiencyVSAvoidsurface flatness of rear surface

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

A coating film is formed on the rear surface of the wafer before exposure processing to compensate for minute scratches that may occur during etching treatment. This preliminary coating action ensures that even if scratches develop later, the exposure surface remains sufficiently flat for accurate processing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The coating film acts as a cushioning layer that compensates for surface irregularities. By providing this protective coating in advance, the system tolerates the thermal expansion differences and resulting scratches without compromising exposure quality.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Object-affected harmful factors

If the rear surface of the wafer has minute scratches, then contaminants may adhere more easily, but the primary issue is that the wafer cannot be horizontally held during exposure processing

Engineering Contradiction:

Improvecontaminant adhesionVSAvoidhorizontal holding accuracy

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The coating film is applied to the rear surface before exposure processing to pre-compensate for surface irregularities. This ensures that even with existing scratches, the wafer can be held horizontally during exposure with sufficient precision.

Inventive Principle:

Principle #10Preliminary action

3Object-affected harmful factors

If a scribing brush is used to clean the rear surface of the wafer, then contaminants are removed, but minute scratches may be generated during the cleaning process itself

Engineering Contradiction:

Improvecontaminant removalVSAvoidsurface flatness of rear surface

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The coating film is formed after cleaning but before exposure processing. This timing allows the cleaning process to remove contaminants while the subsequent coating application compensates for any scratches generated during cleaning, ensuring the final surface is suitable for exposure.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The coating film converts the harmful effect of scratches (whether from etching or cleaning) into a manageable condition by providing a compensating layer that restores surface flatness to acceptable levels for exposure processing.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 effectively planarizes the rear surface of substrates, ensuring accurate and defect-free exposure processing by maintaining a flat surface, even after previous treatments that may introduce scratches, thereby improving the reliability of photolithography and etching processes.

Implementation Method 1

a coating solution is applied to the rear surface of the substrate held by the substrate holding unit

Methodology Applied

Scientific EffectCoating: Coatings

Implementation Method 2

a curing processing unit located in the second treatment chamber for curing the coating solution applied from the coating nozzle to the rear surface of the substrate

Methodology Applied

Scientific EffectCuring: Phase Change

Data Source

PatentUS8703400B2Substrate treatment method, coating treatment apparatus, and substrate treatment system

Publication Date: 2014.04.22 TOKYO ELECTRON LTD

AI summary

In the coating treatment apparatus, in a first treatment chamber, the front and rear surfaces of the substrate held by a transfer arm are inverted by a turning mechanism, and a coating solution is applied from a coating nozzle to the rear surface of the substrate. The substrate is transferred into a second treatment chamber, in which the coating solution on the rear surface is heated by a heating unit to cure, thereby forming a coating film on the rear surface of the substrate. The formation of the coating film by the coating treatment apparatus is performed before exposure processing, whereby the rear surface of the substrate can be flat for the exposure processing.