Wafer Division Using Laser Modified Layers and Reinforcing Sheet

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The existing methods for dividing semiconductor wafers along crossing division lines are hindered by the presence of a reinforcing sheet with an insulating function on the back side, as the laser beam is interrupted, preventing internal processing.

Innovation Solution

A wafer processing method involving a protective member attachment, back grinding, modified layer formation using a laser beam from the back side, mounting a reinforcing sheet, heating it to harden, and applying an external force to divide the wafer along the modified layers, allowing for successful division even with an insulating reinforcing sheet.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a reinforcing sheet with insulating function is mounted on the back side of the wafer, then the mechanical strength and support are improved, but the laser beam is interrupted and internal processing cannot be performed

Engineering Contradiction:

Improvemechanical strengthVSAvoidlaser processing capability

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The laser beam is applied to form the modified layer inside the wafer along the division lines BEFORE the reinforcing sheet is mounted on the back side. This preliminary action allows the laser processing to occur when the path is clear, and the reinforcing sheet is added afterward to provide mechanical support without interfering with the already-formed modified layers

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The manufacturing process is divided into distinct sequential stages: first performing the laser-based internal processing to create modified layers, then separately mounting the reinforcing sheet. This segmentation allows each operation to be optimized independently without the conflicting constraints present when both requirements must be satisfied simultaneously

Inventive Principle:

Principle #1Segmentation

2Duration of action of stationary object

If a thick cutting blade with thickness of 20 μm is used, then the cutting edge durability is improved, but the division line thickness increases to 50 μm reducing productivity

Engineering Contradiction:

Improvecutting edge durabilityVSAvoidwafer division efficiency

Core Design Contradiction:

Duration of action of stationary objectVSProductivity

Solution Approach 1:

The traditional mechanical cutting blade is replaced with a laser beam for forming division lines. The laser creates modified layers inside the wafer material itself through optical energy, eliminating the need for physical contact with a thick cutting blade. This substitution achieves precise, thin division lines while maintaining effective cutting capability through the modified layer structure

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The method changes the fundamental parameter of how division lines are created - from mechanical removal with a thick blade to optical modification with a laser. By controlling the laser parameters (wavelength, pulse duration, focus depth), thin modified layers are formed without requiring thick division lines, thus improving productivity while maintaining cutting effectiveness

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

Enables the division of semiconductor wafers into individual devices while overcoming the interference from the insulating reinforcing sheet, improving productivity by allowing internal processing to proceed effectively.

Implementation Method 1

applying a laser beam having a transmission wavelength to the wafer from the back side of the wafer along each division line in the condition where the focal point of the laser beam is set inside the wafer to thereby form a modified layer inside the wafer along each division line

Methodology Applied

Scientific EffectLaser beam focusing and absorption: Laser

Implementation Method 2

heating the wafer processed by the wafer supporting step to heat the reinforcing sheet mounted on the back side of the wafer, thereby hardening the reinforcing sheet

Methodology Applied

Scientific EffectThermal heating and hardening: Heating

Implementation Method 3

applying an external force to the wafer to thereby divide the wafer into the individual devices along each division line where the modified layer is formed

Methodology Applied

Scientific EffectMechanical fracture along modified layers: Fracture Mechanics

Data Source

PatentUS9093519B2Wafer processing method

Publication Date: 2015.07.28 DISCO CORP

AI summary

In a wafer processing method, the back side of the wafer is ground to reduce the thickness of the wafer to a predetermined thickness. A modified layer is formed by applying a laser beam to the wafer from the back side of the wafer along each division line with the focal point of the laser beam set inside the wafer. The wafer is mounted on a reinforcing sheet having an insulating function on the back side of the wafer and a dicing tape is attached to the reinforcing sheet. The peripheral portion of the dicing tape is supported by an annular frame. The wafer is heated, which also heats the reinforcing sheet, thereby hardening the reinforcing sheet. An external force is applied to the wafer to divide the wafer into individual devices along each division line and to also break the reinforcing sheet along the individual devices.