Silicon Nitride Sintered Substrate With Low Surface Pore Contamination
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Solution Overview
Problem
Existing silicon nitride sintered substrates face issues with contamination and reduced bonding and dielectric strength due to pores and network structures formed by silicon nitride crystals on the surface, which can lead to malfunctions and degradation in semiconductor performance.
Innovation Solution
A silicon nitride sintered substrate is produced using a specific β-type silicon nitride powder and controlled firing conditions to minimize pores of 1 to 10 μm in diameter, resulting in a smooth surface with reduced contamination and improved adhesion for metal layers, achieved by using a continuous firing furnace under normal pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If α-type silicon nitride powder is used and sintered at high temperature, then the interior is densified, but many pores are formed on the surface due to network structure formed by grown needle-like crystals
Solution Approach 1:
The invention changes the crystal type parameter from α-type to β-type silicon nitride powder, which fundamentally alters the sintering behavior and crystal growth pattern. β-type powder produces equiaxed grains instead of needle-like crystals, preventing network structure formation on the surface while maintaining interior densification
Solution Approach 2:
The invention achieves different surface qualities by controlling crystal growth locally. The β-type silicon nitride produces uniform equiaxed grains throughout the substrate, creating a smooth surface without the network structure that would otherwise form, while the interior maintains high density through controlled sintering
2Productivity
If the substrate is used in unpolished state after sintering, then processing steps are reduced, but contamination from releasing agent in pores causes semiconductor malfunctions
Solution Approach 1:
The invention extracts or eliminates the harmful pores from the surface by using β-type silicon nitride powder that does not form network structures. This removes the trapping sites for releasing agent contamination, allowing the substrate to be used in unpolished state without semiconductor malfunctions
Solution Approach 2:
The invention converts the potential harm of using unpolished substrates (contamination risk) into a benefit by eliminating pore formation through β-type powder. The same unpolished state that would normally cause contamination issues now provides a clean surface free of releasing agent residues
3Strength
If network structure is present on surface, then anchoring effect is provided for bonding, but bubbles remain in network structure degrading bonding strength and dielectric strength
Solution Approach 1:
The invention extracts the network structure from the surface by using β-type silicon nitride powder that forms equiaxed grains instead. This eliminates the bubble-trapping network structure while maintaining adequate bonding strength through the dense, uniform grain structure
Solution Approach 2:
The invention changes the surface morphology parameter from network structure to equiaxed grain structure. This fundamental change in microstructure eliminates bubble entrapment while maintaining bonding capability, thereby preserving both bonding strength and dielectric strength
4Strength
If excessive amount of brazing material is used to fill network-shape layer, then bonding is improved, but cost and complexity increase
Solution Approach 1:
The invention extracts the need for excessive brazing material by eliminating the network structure that requires filling. The β-type silicon nitride surface with equiaxed grains provides adequate bonding without requiring large amounts of brazing material to fill voids
Solution Approach 2:
The invention replaces the need for excessive brazing material (a consumable that adds cost and complexity) with a surface structure that provides inherent bonding capability. The β-type powder creates a surface that bonds effectively without requiring heavy use of additional materials
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 substrate significantly reduces contamination from boron nitride residues, prevents semiconductor malfunctions, and enhances bonding strength and dielectric properties, allowing direct metal layer lamination without brazing materials.
Implementation Method 1
A silicon nitride sintered compact is obtained by adding any of various sintering additives to a silicon nitride powder and sintering at a high temperature
Implementation Method 2
a green sheet...is sintered at 1900° C. for 2 to 24 hours in pressurized nitrogen of 10 atm to obtain the silicon nitride sintered compact
Data Source
AI summary
The present invention provides a silicon nitride sintered substrate capable of reducing contamination caused by a boron nitride powder or the like used as a releasing agent and problems in bonding strength and dielectric strength at the time of laminating metal layers or the like, where the contamination is caused by a network structure provided by a silicon nitride crystal formed on the surface of the substrate in an unpolished state after sintering a silicon nitride powder. The silicon nitride substrate in an unpolished state after sintering is a silicon nitride sintered substrate where a cumulative volume of pores having a diameter in a range of 1 to 10 μm is not more than 7.0×10−5 mL/cm2 in a measurement by a mercury porosimetry. Preferably, Ra of the surface is not more than 0.6 μm and arithmetic mean peak curvature (Spc) of a peak is not more than 4.5 [1/mm].