In-situ Semiconductor Surface Cleaning via Germanium Deposition
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Solution Overview
Problem
Conventional high-temperature cleaning methods for semiconductor surfaces before epitaxial deposition are costly and reduce wafer throughput, as they require extensive thermal budgets and can lead to reoxidation of silicon wafers, which is detrimental for high-throughput manufacturing, especially for low-temperature epitaxial processes.
Innovation Solution
A low-temperature method involving exposure of the semiconductor substrate to a Ge source vapor to form GeOx, followed by an etchant gas to remove GeOx, allowing for in-situ epitaxial deposition without the need for high-temperature bake steps, thereby reducing thermal load and maintaining surface purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-temperature cleaning methods are used to remove contaminants from semiconductor surfaces, then cleaning effectiveness is improved, but thermal budget increases and wafer throughput decreases
Solution Approach 1:
The patent changes the temperature parameter from conventional high-temperature cleaning (typically >400°C) to low-temperature cleaning (below 200°C). This is achieved by using a two-step process: first depositing a sacrificial organic layer at low temperature, then removing it with oxygen plasma. The parameter change resolves the contradiction by maintaining effective contaminant removal while dramatically reducing thermal budget and enabling higher wafer throughput.
Solution Approach 2:
The patent introduces a sacrificial organic layer as an intermediary substance. This layer is deposited on the semiconductor surface, serves as a mediator that facilitates contaminant removal through subsequent oxygen plasma treatment, and is then completely removed itself. The intermediary enables effective cleaning at low temperatures without directly exposing the wafer to high-temperature processes, thus resolving the throughput-thermal budget contradiction.
2Manufacturing precision
If high-temperature bake steps are used for surface purification, then contaminant removal is improved, but processing time increases and thermal load increases
Solution Approach 1:
The patent fundamentally changes the temperature parameter from high-temperature baking (>400°C for extended periods) to low-temperature processing (below 200°C). The cleaning action is achieved not through thermal energy but through chemical reactions with oxygen plasma acting on the sacrificial organic layer. This parameter change dramatically reduces processing time while maintaining high surface purity, resolving the time-purity contradiction.
Solution Approach 2:
The patent replaces the thermal-mechanical cleaning mechanism (high-temperature baking that physically desorbs contaminants) with a chemical mechanism (oxygen plasma reactions that chemically decompose and remove contaminants). This substitution allows effective purification at low temperatures and short durations, resolving the contradiction between processing time and surface purity.
3Manufacturing precision
If conventional cleaning procedures are used, then oxide removal is achieved, but reoxidation occurs and surface purity deteriorates
Solution Approach 1:
The patent implements a continuous in-situ process where the sacrificial organic layer is deposited and subsequently removed by oxygen plasma without breaking vacuum or exposing the surface to ambient air. This continuous action prevents reoxidation that would occur during transfer between cleaning and deposition chambers. The useful action of surface purification continues uninterrupted, maintaining surface purity and resolving the contradiction between oxide removal and preventing reoxidation.
Solution Approach 2:
The patent maintains an inert or reduced atmosphere (typically nitrogen or hydrogen ambient) throughout the low-temperature cleaning process. This inert environment prevents oxygen from reoxidizing the cleaned surface during processing. By combining the inert atmosphere with the low-temperature oxygen plasma treatment, the patent achieves effective oxide removal while preventing reoxidation, resolving the purity-maintenance contradiction.
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 method significantly decreases the thermal load and processing time, enhancing wafer throughput and reducing thermal budget consumption, while ensuring the purity of the semiconductor surface for subsequent epitaxial deposition, even at low temperatures.
Implementation Method 1
The substrate is then exposed to a Ge source vapor, thereby leaving a layer of Ge on the surface. The layer of Ge reacts with any oxygen on the substrate surface to form GeOx
Implementation Method 2
The GeOx is removed by exposing the substrate to an etchant
Data Source
AI summary
Methods for low temperature cleaning of a semiconductor surface prior to in-situ deposition have high throughput and consume very little of the thermal budget. GeH4 deposits Ge on the surface and converts any surface oxygen to GeOx. An etchant, such as Cl2 or HCl removes Ge and any GeOx and epitaxial deposition follows. A spike in Ge concentration can be left on the substrate from diffusion into the substrate. All three steps can be conducted sequentially in-situ at temperatures lower than conventional bake steps.