Laser Wafer Slicing With Controlled Reformed Section Depth
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Solution Overview
Problem
The existing method for producing wafers from semiconductor ingots using laser beams often results in reformed sections being formed at shallower locations than intended, leading to increased material loss and reduced yield due to the formation of multi-staged reformed sections.
Innovation Solution
The method involves radiating a laser beam to the ingot at a planned cutoff surface with controlled energy density parameters, including a peak value of 44 J/cm² or less, an energy density rising rate of 1000 J/cm³ or more, and a depth range where the energy exceeds the reforming threshold of 30 μm or less, to form reformed sections at the desired depth position, preventing multi-staged sections and minimizing material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser beam is radiated to form reformed sections in the ingot, then wafers can be sliced from the ingot, but reformed sections are formed at shallower locations than intended, leading to increased material loss
Solution Approach 1:
The patent applies parameter changes by precisely controlling the energy density parameters of the laser beam, including peak value (44 J/cm² or less), energy density rising rate (1000 J/cm³ or more), and depth range where energy exceeds the reforming threshold (30 μm or less). This ensures reformed sections are formed at the intended depth position, preventing multi-staged sections and reducing material loss.
2Productivity
If a laser beam is radiated to form reformed sections in the ingot, then wafers can be sliced from the ingot, but multi-staged reformed sections are formed, reducing manufacturing yield
Solution Approach 1:
The patent applies parameter changes by precisely controlling the energy density parameters of the laser beam, including peak value (44 J/cm² or less), energy density rising rate (1000 J/cm³ or more), and depth range where energy exceeds the reforming threshold (30 μm or less). This ensures reformed sections are formed at the intended depth position, preventing multi-staged sections and reducing material loss.
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 approach allows for the formation of reformed sections at the correct depth position, reducing material loss and improving the manufacturing yield of wafers by controlling the energy density of the laser beam to satisfy specific conditions.
Implementation Method 1
radiating the laser beam to the ingot at a plurality of portions from a direction crossing a planned cutoff surface
Implementation Method 2
an energy density, as an energy per unit area of the laser beam in the ingot when radiating the laser beam to the ingot, exceeds a reforming threshold capable of reforming a part of the ingot on the planned cutoff surface
Implementation Method 3
forming, with the radiation of the laser beam, a plurality of reformed sections at a portion corresponding to a depth position of the planned cutoff surface in the ingot to extend a crack from the reformed section as an origin
Implementation Method 4
extend a crack from the reformed section as an origin, thereby slicing wafers
Data Source
AI summary
A manufacturing method for wafers includes: radiating a laser beam to a planned cutoff surface where the ingot is to be cutoff; and forming, with the radiation of the laser beam, a plurality of reformed sections at the planned cutoff surface to extend a crack from the reformed section, thereby slicing wafers, wherein an energy density of the laser beam exceeds a reforming threshold. The energy density satisfies at least one of conditions of a peak value of the energy density is lower than or equal to 44 J/cm2, a rising rate of the energy density at a portion corresponding to the most shallow position where the energy density reaches the reforming threshold Eth is larger than or equal to 1000 J/cm3, and a range of depth where the energy density exceeds the reforming threshold is smaller than or equal to 30 μm.