Semiconductor Substrate Back Surface Polishing for Lithography Flatness

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Solution Overview

Problem

In semiconductor device fabrication, residual films and concave scratches on the back surface of substrates cause distortion during lithography, leading to poor surface flatness and potential damage to LSI structures, and existing methods for removing these defects are inefficient, especially under high polishing loads.

Innovation Solution

A method involving static pressure bearing technology to polish the back surface of substrates non-contactingly, using a polishing head with a smaller diameter than the substrate, applying pressure fluid to remove foreign materials and defects without damaging the front surface, and performing cleaning and drying in the same chamber to maintain surface flatness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If chemical solution is used to remove residual films on the back surface, then the residual films are removed, but the concave scratches remain and the process is time-consuming

Engineering Contradiction:

Improvesurface flatnessVSAvoidprocess speed

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent replaces chemical etching with mechanical polishing using a polishing head that contacts the back surface of the substrate. This mechanical approach can remove both residual films and concave scratches simultaneously, improving surface flatness without the time-consuming multi-step chemical process

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the polishing load parameter dynamically during the polishing process. By adjusting the polishing load from a first value to a second value, the system optimizes removal of different types of defects (residual films vs. concave scratches) while maintaining productivity

Inventive Principle:

Principle #35Parameter changes

2Productivity

If polishing load is increased to remove defects faster, then productivity improves, but the substrate distorts and crystalline defects or cracks occur

Engineering Contradiction:

Improvepolishing speedVSAvoidsubstrate integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent uses periodic adjustment of polishing load during the polishing process. The polishing load is changed from a first value to a second value in sequence, allowing efficient defect removal while preventing substrate distortion and damage through controlled load variation

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent makes the polishing load dynamic rather than static. By adjusting the polishing load during processing based on substrate response, the system maintains high productivity while preventing substrate damage through adaptive control

Inventive Principle:

Principle #15Dynamics

3Productivity

If a retaining plate is disposed at the surface side to support polishing load, then polishing can be performed, but the fine LSI structure on the front surface is damaged or contaminated

Engineering Contradiction:

Improvepolishing capabilityVSAvoidcontamination of LSI structure

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent polishes the back surface of the substrate instead of the front surface. By applying polishing load to the back surface, the fine LSI structures on the front surface are protected from damage and contamination while still achieving the desired surface flatness improvement

Inventive Principle:

Principle #13The other way round (Inversion)

4Ease of operation

If only the side surface of the substrate is held during polishing, then the substrate can be retained, but distortion increases especially at the center of large scale substrates

Engineering Contradiction:

Improveretention methodVSAvoidsubstrate distortion

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent changes the retention approach from side-surface holding to back-surface contact. By contacting the polishing head with the back surface of the substrate, the system provides distributed support across the substrate area, preventing center distortion while enabling effective polishing

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

This approach effectively removes residual films and concave scratches, enhancing surface flatness and pattern accuracy in lithography, preventing contamination and distortion, while allowing for high productivity and cost-effectiveness.

Implementation Method 1

Polishing the back surface of the substrate can be considered for a method to collectively remove the residual film or the concave scratch

Methodology Applied

Scientific EffectAbrasion: Abrasion

Implementation Method 2

applying pressure fluid to remove foreign materials and defects

Methodology Applied

Scientific EffectFluid pressure: Pressure Increase

Data Source

PatentUS10586694B2Method for fabricating semiconductor device

Publication Date: 2020.03.10 KIOXIA CORP

AI summary

According to one embodiment, a method for fabricating a semiconductor device includes performing a back surface processing to remove at least one of a scratch and a foreign material formed on a back surface of a substrate to be processed, a front surface of the substrate being retained in a non-contact state, contacting the back surface of the substrate to a stage to be retained, and providing a pattern on the front surface of the substrate by using lithography.