Semiconductor Contact Structure Void-Free Filling
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Solution Overview
Problem
The challenge in semiconductor manufacturing is forming a contact structure with high aspect ratio without voids, which is crucial for minimizing leakage current and contact resistance, especially as devices continue to miniaturize.
Innovation Solution
A method involving selective epitaxial growth (SEG) to form an epitaxial layer with a specific dopant concentration, followed by an in-situ gas-phase doping process to create an interface layer with a higher dopant concentration, and then forming a metal silicide layer and plug, ensuring the contact structure fills the high aspect ratio opening without voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicide layer is formed to create an Ohmic contact, then contact resistance is reduced, but the aspect ratio of the contact structure increases making void-free filling difficult
Solution Approach 1:
The contact structure is divided into multiple segments: a first silicide layer formed at the bottom of the contact hole, an intermediate layer formed over the first silicide layer, and a second silicide layer formed over the intermediate layer. This segmentation allows each layer to serve specific functions - the first silicide layer provides Ohmic contact, the intermediate layer prevents excessive reaction and facilitates void-free filling, and the second silicide layer provides additional contact improvement.
Solution Approach 2:
An intermediate layer is introduced between the first silicide layer and the second silicide layer. This intermediate layer acts as a mediator that prevents the second silicide layer from directly reacting with the first silicide layer, thereby avoiding excessive reaction that would create voids. The intermediate layer facilitates smooth transition and enables complete filling of the contact hole without voids.
2Productivity
If the aspect ratio of contact structure is increased to keep up with miniaturization, then device density is improved, but void formation becomes more likely
Solution Approach 1:
The contact structure is segmented into multiple layers with different compositions and functions. The first silicide layer provides initial contact, the intermediate layer prevents excessive reaction and controls filling, and the second silicide layer enhances contact properties. This segmentation enables the contact structure to maintain high aspect ratio without void formation.
Solution Approach 2:
The invention changes the compositional parameters by introducing an intermediate layer with specific properties between the two silicide layers. This parameter change in layer composition and structure allows the contact hole to be completely filled without voids, even at high aspect ratios required for device miniaturization.
3Manufacturing precision
If ion implantation is used to form doped layers, then dopant concentration is precisely controlled, but manufacturing cost increases
Solution Approach 1:
The invention replaces the mechanical ion implantation process with a chemical vapor deposition process. Instead of using ion implantation equipment to introduce dopants, the patent uses a CVD process to form doped silicide layers, where dopants are introduced through chemical reactions during deposition. This substitution eliminates the need for costly ion implantation equipment while achieving the required dopant concentration control.
Solution Approach 2:
The invention changes the manufacturing process parameters by switching from ion implantation to chemical vapor deposition. The CVD process allows for precise control of dopant concentration through gas flow rates, temperature, and pressure parameters, achieving the same level of precision as ion implantation but with lower equipment costs and simpler manufacturing.
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 effectively reduces contact resistance and maintains high aspect ratio filling without voids, improving electrical characteristics and reducing production costs by eliminating the need for costly ion implantation equipment.
Implementation Method 1
forming an epitaxial layer having a first dopant concentration in the pattern; forming in-situ an interface layer having a second dopant concentration higher than the first dopant concentration, over the epitaxial layer. The epitaxial layer may be formed through a selective epitaxial growth (SEG) process
Implementation Method 2
after the selective epitaxial growth process, an in-situ gas-phase doping process may be performed to form the interface layer. The selective epitaxial growth process may include supplying a silicon source gas and an N-type dopant gas in-situ, and the in-situ gas-phase doping process includes supplying a phosphorus-containing dopant gas
Data Source
AI summary
A method for fabricating a semiconductor device includes: forming a semiconductor structure including a pattern; forming an epitaxial layer having a first dopant concentration in the pattern; forming in-situ an interface layer having a second dopant concentration higher than the first dopant concentration, over the epitaxial layer; forming a metal silicide layer over the interface layer; and forming a metal plug over the metal silicide layer.