Epitaxial Substrate Laser Gettering Sink Formation
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Solution Overview
Problem
Current methods for forming gettering sinks in semiconductor substrates are time-consuming and costly, and may reintroduce heavy-metal contamination during heat treatment, especially in thin semiconductor devices where the gettering sink is often scraped away during thinning, and are challenging for large-diameter substrates like 300 mm wafers.
Innovation Solution
A method involving the growth of an epitaxial layer on a semiconductor substrate, where a laser beam is used to induce a multi-photon absorption process in specific microscopic regions, changing the crystal structure and forming a gettering sink capable of capturing heavy metals, which is then annealed to trap these metals, thereby reducing dark leakage current and improving imaging characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is performed to form oxygen precipitates as gettering sinks, then heavy metals can be captured, but the manufacturing time increases and cost increases
Solution Approach 1:
The patent replaces the thermal field (heat treatment) with a laser beam field to form gettering sinks. By using a laser beam to locally melt and solidify the semiconductor substrate, oxygen precipitates are formed rapidly without requiring prolonged heat treatment, thus reducing manufacturing time while maintaining heavy metal capture capability
Solution Approach 2:
The patent uses pulsed laser irradiation instead of continuous heating. The periodic pulsed action allows rapid heating and cooling cycles that form oxygen precipitates quickly, avoiding the need for long-duration heat treatment while achieving the same gettering effect
2Reliability
If heat treatment is performed to form gettering sinks, then heavy metals can be captured, but heavy-metal contamination may be reintroduced during the process
Solution Approach 1:
The patent replaces heat treatment with laser beam processing, which creates a more controlled local environment. The rapid heating and cooling from laser irradiation forms gettering sinks without the prolonged thermal exposure that could allow heavy metal contamination from equipment, thus maintaining capture capability while reducing contamination risk
3Length of moving object
If the semiconductor substrate is thinned to reduce device thickness, then the device becomes thinner, but the gettering sink may be scraped away during thinning
Solution Approach 1:
The patent forms gettering sinks with specific depth control using laser beam parameters. By adjusting the laser beam focus and pulse duration, gettering sinks are created at optimized depths that remain intact during subsequent thinning processes, ensuring both thin device structure and functional gettering sinks coexist
Solution Approach 2:
The patent forms gettering sinks before the thinning process. The preliminary formation allows the gettering sinks to be established at appropriate depths, and the subsequent controlled thinning removes only excess material while preserving the functional gettering sinks, solving both the thinning requirement and gettering integrity
4Reliability
If conventional methods are used to form gettering sinks, then heavy metals can be captured, but the process is complex and costly
Solution Approach 1:
The patent replaces complex heat treatment processes with a simpler laser beam processing method. The laser system directly creates melted zones that solidify into oxygen precipitates, eliminating the need for complex furnace setups, temperature control systems, and prolonged processing, thus reducing manufacturing complexity and cost while maintaining gettering functionality
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 rapid and cost-effective formation of gettering sinks within semiconductor substrates, effectively reducing dark leakage current and maintaining excellent imaging characteristics even in thinned devices, and is applicable to both solid-state imaging devices and back-illuminated devices on large-diameter substrates.
Implementation Method 1
causing a laser beam to be incident on the epitaxial substrate through a condensing means and condensing the laser beam in the microscopic region, to cause a multi-photon absorption process to occur in the microscopic region
Implementation Method 2
annealing the epitaxial substrate at a predetermined temperature to capture heavy metals in the gettering sink
Implementation Method 3
capture heavy metals in the gettering sink
Implementation Method 4
growing an epitaxial layer on one surface of a semiconductor substrate to form an epitaxial substrate
Data Source
AI summary
A semiconductor wafer is set in a laser irradiation apparatus, and laser beam irradiation is performed while the semiconductor wafer is moved. At this time, a laser beam emitted from a laser generating apparatus is condensed by a condensing lens so that the condensing point (focal point) is positioned at a depth of several tens ofμm or so from one surface of the semiconductor wafer. Thereby, the crystal structure of the semiconductor wafer in the position having such a depth is modified, and a gettering sink is formed.