Silicide Gate Electrode Composition Control via Two-Step Alloying
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Solution Overview
Problem
The existing methods for manufacturing semiconductor devices with metal gate electrodes face challenges in controlling the composition of NiSi electrodes, leading to variations in element characteristics and instability, especially when the gate length is short, due to limited process margins for temperature and time in the two-step sintering process, resulting in irregularities and difficulty in achieving precise thickness control.
Innovation Solution
A method involving the formation of a gate electrode through a two-step alloying process, where a metal layer is deposited in excess to form a crystalline phase, followed by heat treatment and removal of excess metal, and subsequent deposition of an additional region to react and form a second alloy, allowing for the formation of Ni3Si and NiSi phases with controlled composition independent of geometric factors, thereby stabilizing the electrode composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a two-step sintering process is used to form NiSi gate electrodes, then the gate electrode composition can be controlled, but the process margins for temperature and time are limited, leading to variations in element characteristics
Solution Approach 1:
The patent segments the gate electrode formation into two distinct alloying steps: first forming an Ni3Si phase, then converting it to NiSi phase. This segmentation allows independent control of each phase formation process, improving composition precision while enhancing reliability through systematic process control.
Solution Approach 2:
The patent systematically changes process parameters (temperature, time, metal layer thickness) between the two alloying steps to achieve precise control over the gate electrode composition. By optimizing each step's parameters independently, the method overcomes the limited process margins of conventional single-step sintering.
2Productivity
If the gate length is shortened to increase device density, then productivity improves, but the gate electrode composition becomes unstable and irregularities increase
Solution Approach 1:
The patent performs preliminary alloying to form the Ni3Si phase before final conversion to NiSi. This preliminary action ensures that the gate electrode composition is established early in the process, making it less sensitive to subsequent variations and preventing irregularities even when gate length is shortened for higher device density.
Solution Approach 2:
The patent applies different alloying conditions to different stages of gate electrode formation, creating local quality variations that ensure uniform composition throughout the gate electrode. This approach maintains composition uniformity regardless of gate length scaling.
3Reliability
If excess metal is deposited to ensure complete reaction, then the alloying process becomes more robust, but additional processing steps are required to remove excess metal
Solution Approach 1:
The patent extracts and removes the excess metal layer after the alloying process. While this adds a removal step, it enables the use of excess metal during alloying to ensure complete reaction and robust process control, ultimately improving reliability without significantly increasing overall device complexity.
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 provides a method to form semiconductor devices with uniform gate electrodes, reducing variations in element characteristics and allowing for precise control of the gate electrode composition, even at short gate lengths, enhancing the reliability and reproducibility of the semiconductor device manufacturing process.
Implementation Method 1
a first alloying step of converting the entire first region into a region (1) made of the first alloy through a reaction between the component S1 in the first region and the metal M1 using heat treatment
Implementation Method 2
through a reaction between the component S1 in the first region and the metal M1 using heat treatment
Implementation Method 3
a second alloying step of converting the entire region (1) into a region (2) made of the second alloy through a reaction between the component S1 in the second region and the first alloy by using heat treatment
Implementation Method 4
through a reaction between the component S1 in the second region and the first alloy by using heat treatment
Implementation Method 5
the metal layer containing an amount of metal M1 more than an amount of metal M1 necessary to react to all the component S1 in the first region to form a first alloy made of a crystalline phase expressed by M1x1S1y1
Data Source
AI summary
Element characteristics disadvantageously fluctuate because the composition of the resultant silicide varies according to the change of the gate length when a full silicide gate electrode is formed by sintering a metal/poly-Si structure. The element characteristics also fluctuate due to element-to-element non-uniformity of the resultant silicide composition. By first forming full silicide having a metal-rich composition, depositing a Si layer thereon, and sintering the combined structure, the metal in the metal-rich silicide diffuses into the Si layer, so that the Si layer is converted into silicide. The entire structure thus is converted into full silicide having a smaller metal composition ratio.