Germanium Oxide Gate Insulator with High-k Dielectric
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Solution Overview
Problem
The challenge is to form a thin germanium oxide film on a germanium layer with a preferable interface condition and reduce the Equivalent Oxide Thickness (EOT) of the gate insulating film, as existing methods result in a high forming rate of germanium oxide films, making it difficult to achieve a thin film with improved interface conditions.
Innovation Solution
A semiconductor structure is developed with a germanium layer and an insulating film comprising a high dielectric oxide film, such as hafnium or yttrium oxide, formed on the germanium layer, where the EOT is 2 nm or less, and a germanium oxide film is formed by oxidizing the germanium layer in an oxygen atmosphere with a partial pressure greater than 1 atmosphere and a temperature less than 550 degrees Celsius, allowing for a thin germanium oxide film with improved interface conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high pressure oxygen gas is used during forming the germanium oxide film, then the interface condition between germanium substrate and germanium oxide film is improved, but the forming rate of the germanium oxide film becomes large, making it difficult to form a thin germanium oxide film
Solution Approach 1:
The patent changes the oxidation parameters by using a two-stage process: first forming a thin germanium oxide film at low temperature (400-550°C) to control thickness and achieve desired EOT, then performing a second oxidation at high temperature (600-700°C) to improve interface conditions. This parameter transformation resolves the contradiction by separating the thickness control function from the interface quality improvement function.
Solution Approach 2:
The oxidation process is segmented into two distinct stages: a first oxidation step to form the thin germanium oxide film with controlled thickness, and a second oxidation step to improve the interface condition. This segmentation allows each step to optimize for its specific function, resolving the contradiction between forming rate and interface quality.
2Productivity
If the forming rate of germanium oxide film is large, then the oxidation process is efficient, but it becomes difficult to form a thin germanium oxide film with EOT of 2 nm or less
Solution Approach 1:
The patent uses parameter transformation by conducting the first oxidation at low temperature (400-550°C) where the oxidation rate is slower and more controllable, enabling precise thickness control to achieve EOT of 2 nm or less. The second oxidation at high temperature (600-700°C) then provides efficient interface improvement without significantly increasing the already-thin film thickness.
Solution Approach 2:
The oxidation process is divided into two segments with different temperature and rate characteristics. The first segment (low temperature) controls film thickness with high precision, while the second segment (high temperature) provides efficient interface improvement. This segmentation resolves the contradiction between oxidation efficiency and thickness control precision.
3Length of stationary object
If a thin germanium oxide film is formed to reduce EOT, then the gate insulating film thickness is reduced, but the leak current density increases
Solution Approach 1:
The patent creates a composite gate insulating film structure consisting of a thin germanium oxide film (providing low EOT) combined with a high-k dielectric film (providing high dielectric constant). This composite structure achieves the desired EOT reduction while the high-k film compensates for the thinness, maintaining low leak current density through its superior dielectric properties.
Solution Approach 2:
The high-k dielectric film acts as an intermediary layer that enables the use of a thin germanium oxide film without suffering from high leak current. The high-k film provides the necessary dielectric strength and barrier properties, allowing the thin germanium oxide layer to function effectively as part of the gate insulating structure.
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 enables the formation of a thin germanium oxide film with a density of 3.6 g/cm3 or more and an EOT of 2 nm or less, achieving a preferable interface condition and reducing leak current density, while maintaining capacitance stability across voltage changes, thus enhancing the performance of semiconductor devices.
Implementation Method 1
a germanium oxide film that is formed on the germanium layer by oxidizing the germanium layer in an oxygen atmosphere under a condition that a partial pressure of the oxygen at room temperature is more than 1 atmosphere
Data Source
AI summary
A semiconductor structure includes: a germanium layer 30; and an insulating film that has a film 32 that includes a germanium oxide and is formed on the germanium layer and a high dielectric oxide film 34 that is formed on the film including the germanium oxide and has a dielectric constant higher than that of a silicon oxide, wherein: an EOT of the insulating film is 2 nm or less; and on a presumption that an Au acting as a metal film is formed on the insulating film, a leak current density is 10−5×EOT+4 A/cm2 or less in a case where a voltage of the metal film with respect to the germanium layer is applied from a flat band voltage to an accumulation region side by 1 V.