Bonded Wafer Cutting Angle Control for Step-Like Oxide Reduction

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Solution Overview

Problem

Direct bonding of silicon wafers without an insulating film often results in residual step-like oxide at the interface, which deteriorates device characteristics and forms defects, especially when wafers with different crystal orientations are bonded.

Innovation Solution

Control the cutting angle of silicon wafers from an ingot to a range of 0-0.1° (compound angle) with respect to a predetermined crystal face, and ensure the bonding is conducted on a hydrophobic surface to minimize the retention of step-like oxide, using an ion implantation-separation process for thinning the active layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If two silicon wafers are directly bonded without an insulating film, then the bonding interface is simplified and manufacturing process is easier, but residual step-like oxide concentrates and retains in the interface deteriorating device characteristics

Engineering Contradiction:

Improvebonding process simplicityVSAvoiddevice characteristics

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies preliminary action by strictly controlling the cutting angle of silicon wafers from the ingot to 0-0.1° compound angle with respect to the predetermined crystal face before bonding. This preliminary control of the cutting angle prevents the formation of step-like oxide concentration at the bonding interface, thereby eliminating the harmful effect while maintaining direct bonding without insulating film.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If silicon wafers are cleaned with HF solution to remove native oxide, then the bonding interface is cleaner, but step-like oxide may still be retained in the bonded interface

Engineering Contradiction:

Improveinterface cleanlinessVSAvoidoxide retention

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by controlling the cutting angle before bonding occurs. By establishing the correct cutting angle of 0-0.1° compound angle with respect to the predetermined crystal face before the bonding process, the formation of step-like oxide is prevented at its source, making subsequent cleaning steps more effective and preventing oxide retention.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies parameter changes by precisely controlling the cutting angle parameter to within 0-0.1° compound angle with respect to the predetermined crystal face. This strict parameter control changes the geometric parameters of the wafer cut, which in turn prevents the concentration and retention of step-like oxide at the bonding interface.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If wafers with different crystal orientations are bonded, then design flexibility is improved, but oxide concentration and defect formation increase

Engineering Contradiction:

Improvecrystal orientation selectionVSAvoidoxide concentration

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by strictly controlling the cutting angle parameter to 0-0.1° compound angle with respect to the predetermined crystal face, regardless of which crystal orientation is selected. This parameter control ensures that even when wafers with different crystal orientations are bonded, the step-like oxide concentration is prevented, allowing design flexibility without suffering from oxide-related harmful effects.

Inventive Principle:

Principle #35Parameter changes

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

Significantly reduces the remnant of step-like oxide at the bonded interface, improving device characteristics and preventing defect formation during the device preparation step.

Implementation Method 1

ions of hydrogen or the like are implanted into a surface layer portion of a silicon wafer for active layer to form an ion-implanted layer

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Implementation Method 2

the removal of a native oxide by immersing in a HF solution

Methodology Applied

Scientific EffectChemical etching:

Data Source

PatentUS8048767B2Bonded wafer and method for producing bonded wafer

Publication Date: 2011.11.01 SUMCO CORP

AI summary

A bonded wafer is produced by directly bonding a silicon wafer for active layer and a silicon wafer for support substrate without an insulating film and thinning the silicon wafer for active layer to a given thickness, in which a silicon wafer cut out from an ingot at a cutting angle of 0-0.1° (compound angle) with respect to a predetermined crystal face is used in each of the silicon wafer for active layer and silicon wafer for support substrate.