A composition for forming a silica layer includes a silicon-containing polymer and a solvent, the composition having a SiO.sub.2 conversion rate of greater than about 0 and less than or equal to about 15. The SiO.sub.2 conversion rate is represented by: SiO.sub.2 conversion rate=(a ratio of an area of SiO to an area of SiH measured after coating the composition in a thickness of 6700 on a bare wafer, and allowing the coated wafer to stand for 24 hours under conditions of a temperature of 85 C. and a relative humidity of 85%)(a ratio of an area of SiO to an area of SiH measured after coating the composition in a thickness of 6700 on a bare wafer, and allowing the coated wafer to stand for 2 hours under conditions of a temperature of 85 C. and a relative humidity of 85%).

A composition for forming a silica layer includes a silicon-containing polymer and a solvent, the composition having a SiO.sub.2 conversion rate of greater than about 0 and less than or equal to about 15. The SiO.sub.2 conversion rate is represented by: SiO.sub.2 conversion rate=(a ratio of an area of SiO to an area of SiH measured after coating the composition in a thickness of 6700 on a bare wafer, and allowing the coated wafer to stand for 24 hours under conditions of a temperature of 85 C. and a relative humidity of 85%)(a ratio of an area of SiO to an area of SiH measured after coating the composition in a thickness of 6700 on a bare wafer, and allowing the coated wafer to stand for 2 hours under conditions of a temperature of 85 C. and a relative humidity of 85%).

A silicon nitride substrate including silicon nitride crystal grains and a grain boundary phase and having a thermal conductivity of 50 W/m.Math.K or more, wherein, in a sectional structure of the silicon nitride substrate, a ratio (T2/T1) of a total length T2 of the grain boundary phase in a thickness direction with respect to a thickness T1 of the silicon nitride substrate is 0.01 to 0.30, and a variation from a dielectric strength mean value when measured by a four-terminal method in which electrodes are brought into contact with a front and a rear surfaces of the substrate is 20% or less. The dielectric strength mean value of the silicon nitride substrate can be 15 kV/mm or more. According to above structure, there can be obtained a silicon nitride substrate and a silicon nitride circuit board using the substrate in which variation in the dielectric strength is decreased.

A silicon nitride substrate including silicon nitride crystal grains and a grain boundary phase and having a thermal conductivity of 50 W/m.Math.K or more, wherein, in a sectional structure of the silicon nitride substrate, a ratio (T2/T1) of a total length T2 of the grain boundary phase in a thickness direction with respect to a thickness T1 of the silicon nitride substrate is 0.01 to 0.30, and a variation from a dielectric strength mean value when measured by a four-terminal method in which electrodes are brought into contact with a front and a rear surfaces of the substrate is 20% or less. The dielectric strength mean value of the silicon nitride substrate can be 15 kV/mm or more. According to above structure, there can be obtained a silicon nitride substrate and a silicon nitride circuit board using the substrate in which variation in the dielectric strength is decreased.

Si.sub.3N.sub.4 nanotubes and nanorods wherein the nanotubes and nanorods of silicon nitride are pure -Si.sub.3N.sub.4 formed by carbothermal reduction of SiO.sub.2 from reacting agricultural husk material in heat and forming the silicon nitride nanotubes and nanorods.

A method of etching is described. The method includes providing a substrate having a first material containing silicon nitride and a second material that is different from the first material, forming a first chemical mixture by plasma-excitation of a first process gas containing H and optionally a noble gas, and exposing the first material on the substrate to the first chemical mixture. Thereafter, the method includes forming a second chemical mixture by plasma-excitation of a second process gas containing N, F, O, and optionally a noble element, and exposing the first material on the substrate to the second plasma-excited process gas to selectively etch the first material relative to the second material.

Disclosed herein are compositions, devices and methods for inactivating viruses, bacteria, and fungi. The compositions, methods, and devices may include coatings or slurries such as silicon nitride powder coatings or slurries for the inactivation of viruses, bacteria, and/or fungi.

Disclosed herein are compositions, devices and methods for inactivating viruses, bacteria, and fungi. The compositions, methods, and devices may include coatings or slurries such as silicon nitride powder coatings or slurries for the inactivation of viruses, bacteria, and/or fungi.

A method of etching is described. The method includes providing a substrate having a first material containing silicon nitride and a second material that is different from the first material, forming a first chemical mixture by plasma-excitation of a first process gas containing H and optionally a noble gas, and exposing the first material on the substrate to the first chemical mixture. Thereafter, the method includes forming a second chemical mixture by plasma-excitation of a second process gas containing N and F, and optionally a noble element, and exposing the first material on the substrate to the second plasma-excited process gas to selectively etch the first material relative to the second material.

A method of etching is described. The method includes providing a substrate having a first material containing silicon nitride and a second material that is different from the first material, forming a first chemical mixture by plasma-excitation of a first process gas containing H and optionally a noble gas, and exposing the first material on the substrate to the first chemical mixture. Thereafter, the method includes forming a second chemical mixture by plasma-excitation of a second process gas containing N and F, and optionally a noble element, and exposing the first material on the substrate to the second plasma-excited process gas to selectively etch the first material relative to the second material.