Wafer Ring Removal for Flat Dicing via Laser and Vacuum

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Solution Overview

Problem

Wafers ground to a thickness of 100 μm or less often warp due to stress, leading to issues during dicing, where the ring portion is left unground to reduce warpage, resulting in a decrease in effective semiconductor chips and gaps between the wafer and dicing tape.

Innovation Solution

A semiconductor-element manufacturing method using a laser to cut out the ring portion of the wafer, forming a flat surface that is then attached to dicing tape using a vacuum end-effector, allowing for precise dicing without adverse effects on chip count or tape adhesion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the wafer is ground to a thickness of 100 μm or less, then the manufacturing precision is improved, but the wafer warps due to stress, making it impossible to transfer and dice

Engineering Contradiction:

Improvewafer thickness precisionVSAvoidwafer flatness

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary action by removing the ring portion from the wafer before the dicing process. This prevents the warpage issue from affecting subsequent processing steps. The ring portion is cut out using laser light while the wafer is held flat on a vacuum stage, ensuring the remaining central portion remains flat and can be properly transferred and diced.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent segments the wafer by removing the ring portion (outer peripheral region) separately from the central portion containing the semiconductor elements. This segmentation allows the central portion to be processed independently without the warpage problems caused by the thick ring portion, while preserving all effective chips in the center.

Inventive Principle:

Principle #1Segmentation

2Stability of the object's composition

If the ring portion is left unground to reduce warpage, then the wafer stability is improved, but the number of effective chips decreases due to gaps between the wafer and dicing tape

Engineering Contradiction:

Improvewafer flatnessVSAvoidnumber of effective chips

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent performs the ring portion removal as a preliminary action before dicing. By removing the problematic ring portion first, the remaining central wafer area is guaranteed to be flat and free of gaps when attached to the dicing tape. This ensures maximum utilization of effective chips without any loss due to warpage-related adhesion problems.

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If the ring portion is removed after attaching to dicing tape, then the warpage issue is addressed, but the process complexity increases and chip count decreases

Engineering Contradiction:

Improvewafer flatnessVSAvoidprocess complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent inverts the conventional sequence by removing the ring portion before attaching to dicing tape, rather than after. This reversal simplifies the overall process because the wafer is held flat on a vacuum stage during ring removal, making the operation easier and more precise. The inverted sequence eliminates the need for complex gap management during ring removal.

Inventive Principle:

Principle #13The other way round (Inversion)

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 enables wafer dicing without reducing the number of effective chips and eliminates gaps between the wafer and dicing tape, ensuring a stable and efficient semiconductor-element production process.

Implementation Method 1

with the first surface of the wafer being held on a vacuum stage by suction

Methodology Applied

Scientific EffectSuction: Suction

Implementation Method 2

with the second surface of the flat wafer being held by a vacuum end-effector by suction

Methodology Applied

Scientific EffectSuction: Suction

Implementation Method 3

cutting out the ring portion of a wafer with laser light to form a flat wafer

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS9659808B2Semiconductor-element manufacturing method and wafer mounting device using a vacuum end-effector

Publication Date: 2017.05.23 MITSUBISHI ELECTRIC CORP

AI summary

According to the present invention, a semiconductor-element manufacturing method including the steps of cutting out a ring portion of a wafer with laser light to form a flat wafer, the ring portion being formed on a periphery of the wafer and thicker than a central portion of the wafer, the wafer having a first surface and a second surface opposite to the first surface, with the first surface of the wafer being held on a vacuum stage by suction, attaching the first surface to dicing tape after detaching the flat wafer from the vacuum stage with the second surface of the flat wafer being held by a vacuum end-effector by suction, and dicing the flat wafer attached to the dicing tape.