Metallic MOL-BEOL Heater for Semiconductor Thermal Tuning
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Solution Overview
Problem
Current semiconductor chip designs face challenges in meeting thermal requirements due to the distance between back end of the line (BEOL) and front end of the line (FEOL) levels, and middle of the line (MOL) polysilicon heaters exhibit reliability issues.
Innovation Solution
A semiconductor structure with a metallic heating element having a lower portion within the MOL dielectric layer adjacent to the semiconductor device and an upper portion extending into the BEOL dielectric layer, formed by creating a cavity and filling it with metallic material, which allows for local temperature increase without the reliability issues of polysilicon-based heaters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If BEOL heaters are used to heat FEOL semiconductor devices, then thermal requirements can be met, but the separation distance between BEOL and FEOL levels makes it difficult to achieve effective heating
Solution Approach 1:
The heating element extends vertically through multiple dielectric layers (MOL and BEOL) to bridge the separation distance between FEOL and BEOL levels. This three-dimensional configuration allows the heater to physically connect regions that are separated in the vertical dimension, enabling effective thermal coupling without requiring lateral proximity.
Solution Approach 2:
The heating element acts as an intermediary structure that transfers thermal energy from the BEOL region to the FEOL semiconductor device. By positioning the heater to extend through intermediate dielectric layers, it mediates the thermal interaction between distant regions, overcoming the limitation of direct thermal coupling over large separation distances.
2Temperature
If MOL polysilicon heaters are used to place heaters closer to FEOL semiconductor devices, then heating effectiveness improves, but reliability issues arise
Solution Approach 1:
The invention changes the material parameter of the heating element from polysilicon to metal (such as tungsten, copper, or aluminum). This material substitution fundamentally alters the thermal and electrical properties, providing superior reliability while maintaining the ability to generate heat effectively at the MOL level close to the FEOL device.
Solution Approach 2:
The heating structure combines metal heating material with surrounding dielectric layers (MOL and BEOL) to form a composite structure. The metal provides reliable heating functionality, while the dielectric materials provide structural support, electrical isolation, and thermal management, creating a synergistic system that overcomes the limitations of pure polysilicon heaters.
3Temperature
If heating elements are placed closer to semiconductor devices, then thermal tuning effectiveness improves, but the risk of damaging the device increases
Solution Approach 1:
The heating element is positioned within dielectric layers at a controlled distance from the semiconductor device, creating a localized heating zone. The dielectric materials provide thermal isolation that concentrates heat where needed while preventing excessive temperature rise that could damage the device, achieving effective thermal tuning with controlled thermal gradients.
Solution Approach 2:
The dielectric layers (MOL and BEOL) surrounding the heating element provide thermal cushioning before heat reaches the semiconductor device. These layers act as thermal buffers that moderate the heat transfer, protecting the device from direct exposure to extreme temperatures while still allowing effective thermal tuning to occur.
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
The metallic heating element effectively raises the temperature of semiconductor devices, such as e-fuses or photonic devices, reducing the current needed for programming and enhancing thermal tuning, thereby improving reliability and efficiency.
Implementation Method 1
The metallic heating element can be employed to locally raise the temperature of the semiconductor device
Implementation Method 2
The metallic heating element can have a lower portion, which is within a middle of the line (MOL) dielectric layer adjacent to the semiconductor device
Data Source
AI summary
A semiconductor structure includes a semiconductor device (e.g., an e-fuse or photonic device) and a metallic heating element adjacent thereto. The heating element has a lower portion within a middle of the line (MOL) dielectric layer adjacent to the semiconductor device and an upper portion with a tapered top end that extends into a back end of the line (BEOL) dielectric layer. A method of forming the semiconductor structure includes forming a cavity such that it has both a lower section, which extends from a top surface of a MOL dielectric layer downward toward a semiconductor device, and an upper section, which extends from the top surface of the MOL dielectric layer upward and which is capped by an area of a BEOL dielectric layer having a concave bottom surface. A metallic fill material can then be deposited into the cavity (e.g., through via openings) to form the heating element.