Epitaxial Stack Deposition Cycles to Reduce Wafer Warpage
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Solution Overview
Problem
The semiconductor industry faces challenges in manufacturing 3D DRAM devices due to limitations in planar scaling, leading to issues such as substrate warpage, bowing, and stress relaxation in thicker epitaxial stacks, which affect alignment and etching uniformity.
Innovation Solution
A method and apparatus for forming epitaxial stacks on multiple substrates using alternating deposition cycles with different reaction gas mixtures and dopant precursors, reducing substrate warpage and stress through the use of dopants in epitaxial layers, and employing a vertical processing furnace for batch operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thicker epitaxial stacks are formed on substrates, then the manufacturing of 3D DRAM devices is enabled to overcome planar scaling limits, but substrate warpage and bowing occur affecting alignment and etching uniformity
Solution Approach 1:
The epitaxial stack is segmented into multiple alternating layers of different materials (e.g., SiGe and Si) with different stress characteristics. This segmentation allows the tensile stress in one layer to compensate for compressive stress in another layer, thereby reducing overall substrate warpage and bowing while maintaining the total thickness needed for 3D DRAM manufacturing
Solution Approach 2:
Different regions of the epitaxial stack are assigned different material compositions and stress characteristics. By locally varying the material properties (e.g., Ge concentration in SiGe layers) throughout the stack, the patent achieves stress distribution that counteracts warpage while maintaining etching uniformity across the substrate surface
2Manufacturing precision
If multiple deposition cycles are executed to form thicker epitaxial stacks, then 3D DRAM device manufacturing is enabled, but processing time and cost increase
Solution Approach 1:
The patent employs continuous deposition cycles where reactive and non-reactive gas phases alternate without interruption. The reactive phase deposits epitaxial material while the non-reactive phase provides stress control and prevents excessive warpage accumulation, allowing continuous formation of thick stacks without breaking the process into separate batches
Solution Approach 2:
The deposition process uses periodic alternation between reactive gas phases (for material deposition) and non-reactive gas phases (for stress control). This periodic action enables the formation of thick epitaxial stacks by accumulating controlled stress compensation in each cycle, reducing total processing time compared to traditional continuous deposition
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 thicker, stress-poor epitaxial stacks with reduced warpage and bowing, improving commercial success by enhancing etch selectivity and uniformity, while reducing processing costs and time.
Implementation Method 1
A plurality of deposition cycles may be executed, thereby forming the epitaxial stack on the plurality of substrates. Each deposition cycle may comprise a first deposition pulse and a second deposition pulse. The first deposition pulse may comprise a provision of a first reaction gas mixture to the process chamber, thereby forming the first epitaxial layer.
Implementation Method 2
The first or the second deposition pulse may further comprise a provision of a dopant precursor gas to the process chamber.
Data Source
AI summary
A method and a wafer processing furnace for forming an epitaxial stack on a plurality of substrates is provided. In a preferred embodiment, the method comprises providing the plurality of substrates to a process chamber. A plurality of deposition cycles is executed, thereby forming the epitaxial stack on the plurality of substrates. The epitaxial stack comprises a plurality of epitaxial pairs, wherein the epitaxial pairs each comprises a first epitaxial layer and a second epitaxial layer, the second epitaxial layer being different from the first epitaxial layer. Each deposition cycle comprises a first deposition pulse and a second deposition pulse. The first deposition pulse comprises a provision of a first reaction gas mixture to the process chamber, thereby forming the first epitaxial layer. The second deposition pulse comprises a provision of a second reaction gas mixture to the process chamber, thereby forming the second epitaxial layer. The first deposition pulse or the second deposition pulse further comprises a provision of a dopant precursor gas to the process chamber.