Direct Germanium Deposition on SiO2 via Higher Order Precursors
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Solution Overview
Problem
Current methods for depositing pure and continuous Germanium layers on SiO2 surfaces using Chemical Vapour Deposition (CVD) require a silicon seed layer, which is undesirable in some applications, and lack a method for direct deposition without seed layers, as Germanium suboxides formed with GeH4 precursors desorb at growth temperatures, preventing Ge growth on SiO2 areas.
Innovation Solution
A method involving the use of higher order germanium precursors like digermane (Ge2H6) or trigermane (Ge3H8) in a gas mixture with a non-reactive carrier gas at atmospheric pressure, deposited between 275°C and 500°C, achieving a continuous Germanium layer on substrates including SiO2 without a seed layer by maintaining sufficient partial pressure of the germanium precursor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If GeH4 is used as the germanium precursor for CVD deposition on SiO2, then Ge growth can occur on Si areas, but Ge growth is prevented on SiO2 areas due to formation of volatile germanium suboxides
Solution Approach 1:
The patent changes the chemical parameters of the germanium precursor from GeH4 to higher order germanes (Ge2H6, Ge3H8, Ge4H10), which have different reactivity and decomposition characteristics. This parameter change allows Ge deposition on SiO2 without forming volatile suboxides, enabling continuous layer formation across both Si and SiO2 areas.
Solution Approach 2:
The patent uses composite gas mixtures containing higher order germane precursors combined with carrier gases (H2, N2, Ar) and sometimes dopant gases. This composite approach optimizes the deposition process by controlling precursor delivery, reaction kinetics, and layer quality while enabling direct deposition on SiO2.
2Reliability
If a Si seed layer is deposited on SiO2 before Ge deposition, then continuous Ge growth is enabled, but the presence of the seed layer is undesirable in some applications
Solution Approach 1:
The patent extracts and eliminates the intermediate Si seed layer step from the deposition process. By using higher order germane precursors directly, the method achieves direct Ge deposition on SiO2 without requiring the seed layer, thereby simplifying the process structure while maintaining continuous layer formation.
Solution Approach 2:
The patent performs preliminary optimization of deposition parameters (temperature, pressure, gas flow rates, precursor concentration) to enable direct Ge nucleation and growth on SiO2. This preliminary preparation of optimal conditions allows direct deposition without intermediate layers.
3Reliability
If higher order germanium precursors are used with increased partial pressure, then direct Ge deposition on SiO2 is enabled, but process parameter optimization becomes more complex
Solution Approach 1:
The patent employs dynamic control of deposition parameters including variable gas flow rates, adjustable precursor partial pressures, and temperature programming during deposition. This dynamic adjustment allows optimization of nucleation and growth rates to achieve continuous layers while managing the complexity of multiple interdependent parameters.
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
Enables the deposition of continuous, pure Germanium layers on SiO2 and other challenging surfaces like titanium nitride, overcoming the issue of selective growth and island formation, with optimal conditions determined by partial pressure and temperature, resulting in a continuous and polycrystalline Ge layer.
Implementation Method 1
Introducing said substrate into a reaction chamber suitable for applying a layer onto said surface by chemical vapour deposition (CVD)
Implementation Method 2
Depositing by CVD a continuous germanium layer overlying and in contact with said substrate surface... said deposition step is performed at a deposition temperature between about 275°C and about 500°C
Data Source
Figure 1
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Figure 3b~4
AI summary
The present invention is related to a method for the deposition of a continuous layer of Ge on a substrate by chemical vapour deposition. According to the invention, a mixture of a non-reactive carrier gas and a higher order germanium precursor gas, i.e. of higher order than germane (GeH4), is applied. Preferably the deposition is done under application of a deposition temperature between about 275°C and about 500°C, with the partial pressure of the precursor gas within the mixture being at least 20mTorr for temperatures between about 275°C and about 285°C, and at least 10mTorr for temperatures between about 285° and about 500°C.