Laser Processing Control for Wafer Thickness-Based Pass Calculation

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Solution Overview

Problem

Existing laser processing apparatuses require manual calculation of the number of spots and passes for a pulsed laser beam to achieve desired processing depth, which is cumbersome and prone to errors, especially when processing wafers of different thicknesses, leading to potential damage.

Innovation Solution

A laser processing apparatus with a controller that calculates the number of spots and passes based on the workpiece's thickness and spot diameter, using storage sections for processing depth, thickness, and overlap rate, allowing automated control of the processing trajectory and feed mechanisms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If manual calculation of number of spots and passes is performed for each wafer thickness, then processing accuracy can be achieved, but operation complexity and time consumption increase significantly

Engineering Contradiction:

Improveprocessing accuracyVSAvoidoperation complexity

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The system performs self-service by automatically calculating the number of spots and passes based on wafer thickness input. The calculation unit computes processing parameters autonomously using stored spot diameter and depth limit values, eliminating the need for manual calculation by operators while maintaining processing accuracy.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The manual calculation process is replaced by an automated calculation unit that uses electronic computation. The system substitutes human mental/mathematical operations with an electronic calculation mechanism that automatically determines processing parameters based on input thickness and stored constants.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If manual calculation is used to determine processing parameters, then flexibility to handle different wafer thicknesses is maintained, but calculation errors can cause wafer damage

Engineering Contradiction:

Improveflexibility for different thicknessesVSAvoidrisk of calculation error

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system incorporates feedback mechanisms where the calculation unit continuously computes processing parameters based on actual wafer thickness measurements. The controller uses these calculated values to adjust the number of spots and passes, ensuring that processing parameters always match the actual workpiece conditions, thereby preventing errors and damage.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Inventive Principle:

Principle #25Self-service

3Manufacturing precision

If the number of passes is increased to achieve desired groove depth, then processing depth requirement is met, but excessive passes cause wafer damage due to repeated irradiation

Engineering Contradiction:

Improvegroove depth accuracyVSAvoidwafer damage from excessive irradiation

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The system dynamically changes processing parameters (number of spots and passes) based on wafer thickness. By adjusting these parameters according to the actual thickness and the calculated limit processing depth, the system achieves the desired groove depth while avoiding excessive irradiation that would cause wafer damage.

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

Automates the calculation of processing parameters, reducing the need for manual input and minimizing errors, ensuring accurate processing without wafer damage across varying thicknesses.

Implementation Method 1

a condenser configured to condense the pulsed laser beam emitted by the laser oscillator onto the workpiece held on the chuck table

Methodology Applied

Scientific EffectCondensation of laser beam: Focusing

Implementation Method 2

a laser beam irradiating unit configured to irradiate the workpiece held on the chuck table with a pulsed laser beam... forming grooves having a desired depth by irradiating the wafer with the pulsed laser beam of a wavelength absorbable by the wafer

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS20230398630A1Laser processing apparatus

Publication Date: 2023.12.14 DISCO CORP

AI summary

A controller of a laser processing apparatus includes a processing trajectory storage section, a thickness storage section (TSS), a limit processing depth storage section (LPDSS), a pass number storage section (PNSS), a spot overlap rate storage section, and a selecting section. The controller calculates a processing width by multiplying, by a spot diameter, a value obtained by dividing a thickness stored in the TSS by a limit value stored in the LPDSS, and calculates the number of passes of a pulsed laser beam (LB) to be applied to a section width-wise by multiplying the value obtained by dividing the thickness stored in the TSS by the limit value stored in the LPDSS by the number of passes stored in the PNSS, and multiplying a result by a number of spots determined from the spot diameter of the LB, the overlap rate of the spots, and the processing width.