Atomic Layer Deposition Temperature Segmentation for Film Quality
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Solution Overview
Problem
Atomic layer deposition techniques face limitations in achieving high-quality thin films due to low growth-per-cycle rates and impurities from unreacted precursor ligands, particularly in the deposition of films thinner than 5 nm, leading to film roughness and pinholes.
Innovation Solution
An optimized atomic layer deposition method involving sequential pulses of precursor gases at specific temperatures, including a first precursor gas like HfCl4 and a second gas like H2O, with optional plasma treatment and temperature adjustments to enhance growth-per-cycle and reduce impurities, utilizing a reactor design with heating and cooling susceptors for precise temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ALD method is used with single temperature process, then process simplicity is maintained, but growth-per-cycle is low (15% of monolayer) and film quality is poor
Solution Approach 1:
The patent segments the ALD process into multiple temperature stages: a first temperature for precursor adsorption, a second higher temperature for reaction, and a third lower temperature for purification. This segmentation allows each stage to be optimized independently, achieving 40% monolayer growth-per-cycle while maintaining process control through systematic division of the deposition sequence.
Solution Approach 2:
The patent implements dynamic temperature adjustment during the ALD cycle, transitioning between three distinct temperature states. The substrate temperature is dynamically changed to match process requirements: lower during precursor introduction, higher during reaction, and lower again during purge. This dynamic control optimizes both growth rate and film quality.
2Manufacturing precision
If conventional ALD is used for thin films thinner than 5 nm, then deposition is achieved, but film roughness and pinholes occur due to slow film closure
Solution Approach 1:
The patent changes the temperature parameter throughout the deposition cycle to optimize film quality. By using a second temperature higher than the first during the reaction phase, the process achieves faster growth rates (40% monolayer per cycle) while the subsequent cooling to third temperature ensures complete reaction and smooth film closure, eliminating pinholes in thin films.
Solution Approach 2:
The patent employs periodic temperature cycling with distinct phases: adsorption at first temperature, reaction at second temperature, and purification at third temperature. This periodic action ensures complete film closure with each cycle, producing smooth, pinhole-free thin films while maintaining high deposition efficiency.
3Reliability
If conventional ALD with single temperature is used, then process simplicity is maintained, but Cl-impurities remain in the deposited layer
Solution Approach 1:
The patent segments the reactor into multiple temperature zones and uses a dual susceptor design with independent temperature control. The first susceptor operates at first temperature for precursor introduction, while the second susceptor operates at third temperature for purification. This spatial and thermal segmentation enables effective removal of Cl-impurities through the temperature gradient-driven purification process.
Solution Approach 2:
The patent introduces a temperature gradient as an intermediary mechanism to separate and purify the deposited layer. By maintaining different temperatures between the two susceptors, the process creates a thermal field that acts as an intermediary to drive off volatile Cl-containing species during the purification phase, achieving high film purity.
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
The method enhances growth-per-cycle from 15% to 40% of a monolayer and reduces Cl-content by two orders of magnitude, improving film quality and scalability, specifically for hafnium oxide deposition, while maintaining precise thickness control.
Implementation Method 1
Atomic layer deposition is a thin film deposition technique based on the used for separated chemisorption reactions of at least two gas phase reactants with a substrate
Implementation Method 2
providing a first pulse of a second precursor gas into the reactor at a second temperature... any precursor able to decompose the first precursor, or to eliminate the ligands of the first precursor
Implementation Method 3
heating the substrate surface at a fourth temperature, between step c) and d)... the fourth temperature can be substantially equal or higher than the second temperature, preferably higher than about 375° C.
Implementation Method 4
providing a second pulse of the second precursor gas at a third temperature lower than the second temperature... the third temperature can be substantially lower than the second temperature, preferably lower than about 500° C., or than about 350° C., or than about 225° C. and more preferably is room temperature
Implementation Method 5
the substrate can be exposed to a plasma treatment during and/or after step d)... The plasma used for the plasma treatment can consist of N2O, NO, O2, N2, H2, NO2, or NH3
Data Source
AI summary
One inventive aspect is related to an atomic layer deposition (ALD) method comprising:a) providing a semiconductor substrate in a reactor,b) providing a pulse of a first precursor gas into the reactor at a first temperature,c) providing a first pulse of a second precursor gas into the reactor at a second temperature, andd) providing a second pulse of the second precursor gas at a third temperature lower than the second temperature. Another inventive aspect relates to a reactor suitable to apply the method.