Backside Wafer Deposition for Bow Compensation and Overlay Accuracy

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Solution Overview

Problem

The increasing complexity of semiconductor fabrication, particularly with advanced patterning and 3D device construction, leads to substrate bowing and uneven curvature due to stress from multiple layers of film, resulting in overlay errors and reduced feature size uniformity.

Innovation Solution

The technique involves depositing films on the backside of a substrate to create corrective stresses, counteracting the stresses on the working surface and flattening the substrate without physically contacting the front or backside surfaces, using a substrate holder that seals the perimeter to prevent deposition on the front side.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If multiple layers of film are deposited on the front side of the substrate to increase device density, then device density is improved, but substrate bowing increases causing overlay errors

Engineering Contradiction:

Improvedevice densityVSAvoidoverlay accuracy

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent applies asymmetric stress compensation by depositing films only on the backside of the substrate rather than the front side. This asymmetric approach allows the front side device layers to remain intact while the backside film creates counteracting stress to flatten the substrate, resolving the overlay errors caused by front-side film deposition

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

Instead of depositing films on the conventional front side of the substrate, the patent inverts the approach by depositing films on the backside. This inversion allows stress compensation without interfering with the device structure on the front side, thereby maintaining both high device density and overlay accuracy

Inventive Principle:

Principle #13The other way round (Inversion)

2Stability of the object's composition

If vacuum clamping is used to prevent substrate expansion during exposure, then substrate stability is improved, but electrostatic clamping is insufficient in vacuum environments

Engineering Contradiction:

Improvesubstrate stabilityVSAvoidclamping force

Core Design Contradiction:

Stability of the object's compositionVSForce

Solution Approach 1:

The patent performs preliminary action by depositing the stress-compensating film on the backside of the substrate before the exposure process. This pre-deposited film provides ongoing stress compensation throughout the exposure and heating processes, reducing reliance on vacuum clamping strength and enabling stable substrate positioning even with electrostatic clamping in vacuum environments

Inventive Principle:

Principle #10Preliminary action

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 method effectively reduces substrate bowing and improves overlay accuracy by applying compensating stresses on the backside of the substrate, maintaining the existing orientation and preventing damage to the front side features.

Implementation Method 1

a lower section (112) with a substrate support (120) and deposition hardware (130) for depositing films on the backside surfaces of substrates

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Implementation Method 2

maintaining a pressure differential between the upper section and the lower section sufficient to prevent passage of the deposition gas from the lower section to the front side surface

Methodology Applied

Scientific EffectPressure Gradient: Pressure Gradient

Data Source

PatentUS12341053B2System for backside deposition of a substrate

Publication Date: 2025.06.24 TOKYO ELECTRON LTD

AI summary

An apparatus for depositing films on a backside of a substrate includes a processing chamber and a substrate support having an annular support surface. A first gas distribution unit includes a plurality of gas delivery openings arranged along the backside surface of the substrate and configured to direct plasma deposition gas to the backside surface. A second gas distribution unit is configured to flow a second gas into the processing chamber such that the front side surface of the substrate is exposed to the second gas. A controller is configured to control flow of the plasma deposition gas from the first gas distribution unit, flow of the second gas from the second gas distribution unit a vacuum system. The controller maintains a gas pressure differential between the front side surface and the backside surface of the substrate sufficient to prevent passage of the deposition gas from the backside surface.