A wafer thinning method and a wafer structure are provided. In the wafer thinning method, a to-be-thinned wafer is provided, and the to-be-thinned wafer is grinded on a rear surface of the to-be-thinned wafer. Then, a first planarization process is performed on a rear surface of the grinded wafer to restore surface flatness of the grinded wafer, and a second planarization process is performed on a rear surface of the wafer obtained after the first planarization process is performed until a target thinned thickness is reached.

A cutting tool includes: a shank part; and a cutting part provided at one end of the shank part. The cutting part includes a first region provided at one end of the cutting tool, and a second region located closer to a center of the cutting tool than the first region. Abrasive grains adhere to the first region and the second region. An average grain diameter of the abrasive grains in the second region is smaller than an average grain diameter of the abrasive grains in the first region.

A cutting tool includes: a shank part; and a cutting part provided at one end of the shank part. The cutting part includes a first region provided at one end of the cutting tool, and a second region located closer to a center of the cutting tool than the first region. Abrasive grains adhere to the first region and the second region. An average grain diameter of the abrasive grains in the second region is smaller than an average grain diameter of the abrasive grains in the first region.

A polishing device has a substrate stage which holds a substrate Wf, a processing head which processes a surface of the substrate Wf, an indentation detecting system which detects a position of an indentation in the substrate Wf, a movement mechanism which moves the processing head in a radial direction of the substrate stage, and a rotation mechanism which rotates the substrate stage, and the indentation detecting system has a fluid injection nozzle configured to inject a fluid to a circumferential edge portion of the substrate Wf when the substrate Wf is held on the substrate stage, a fluid measuring device which measures a physical quantity which is pressure or a flow rate of the fluid, and a position detector which detects the position of the indentation formed in the circumferential edge portion of the substrate Wf based on a change in physical quantity.

Provided is a method of double-side polishing a silicon wafer using a double-side polishing apparatus, the method including in succession: a first polishing step of performing double-side polishing while supplying a first polishing agent that is an alkaline aqueous solution containing abrasive grains to the polishing cloths; a polishing agent switching step of stopping the supply of the first polishing agent and starting the supply of a second polishing agent that is an alkaline aqueous solution containing a water-soluble polymer with no abrasive grains, with the polishing cloths of the upper plate and the lower plate being in contact with the front surface and the back surface of the silicon wafer, respectively and with the upper plate and the lower plate being continuously rotated; and a second polishing step of performing double-side polishing while supplying the second polishing agent to the polishing cloths.

A thickness measuring apparatus for measuring the thickness of a workpiece held on a chuck table includes the followings: a light source configured to emit white light; an optical branching unit configured to branch, to a second optical path, reflected light applied from the light source to the workpiece held on the chuck table via a first optical path and reflected from the workpiece; a diffraction grating disposed in the second optical path; an image sensor configured to detect an optical intensity signal of light separated into each wavelength by the diffraction grating; and a thickness output unit configured to generate a spectral interference waveform on the basis of the optical intensity signal detected by the image sensor, determine the thickness on the basis of the spectral interference waveform, and output the thickness.

A seed crystal for single crystal 4H-SiC growth of the present invention is a disk-shaped seed crystal for single crystal 4H-SiC growth having a diameter of more than 150 mm and having a thickness within a range of more than or equal to 1 mm and less than or equal to 0.03 times of the diameter, in which one surface on which the single crystal 4H-SiC is grown is a mirror surface and an Ra of the other surface is more than 10 nm, and an absolute value of magnitude of waviness in a state where the seed crystal is freely deformed so that an internal stress distribution is reduced is less than or equal to 12 μm.

A seed crystal for single crystal 4H-SiC growth of the present invention is a disk-shaped seed crystal for single crystal 4H-SiC growth having a diameter of more than 150 mm and having a thickness within a range of more than or equal to 1 mm and less than or equal to 0.03 times of the diameter, in which one surface on which the single crystal 4H-SiC is grown is a mirror surface and an Ra of the other surface is more than 10 nm, and an absolute value of magnitude of waviness in a state where the seed crystal is freely deformed so that an internal stress distribution is reduced is less than or equal to 12 μm.

A method of manufacturing a mechanical element includes: a first step of forming a mechanical element that has a sliding surface, which constitutes machinery, by precision machining; a second step of subjecting the sliding surface of the formed mechanical element to surface processing; and a third step of grinding down protrusions on the sliding surface of the mechanical element subjected to surface processing with a grinding agent composition in which ceramic particles are dispersed in oil and embedding the ceramic particles in cavities on the sliding surface of the mechanical element, the ceramic particles each having a hardness higher than a hardness of the mechanical element and being 0.01 .Math.m or more and 0.5 .Math.m or less in particle size.

A method of manufacturing a mechanical element includes: a first step of forming a mechanical element that has a sliding surface, which constitutes machinery, by precision machining; a second step of subjecting the sliding surface of the formed mechanical element to surface processing; and a third step of grinding down protrusions on the sliding surface of the mechanical element subjected to surface processing with a grinding agent composition in which ceramic particles are dispersed in oil and embedding the ceramic particles in cavities on the sliding surface of the mechanical element, the ceramic particles each having a hardness higher than a hardness of the mechanical element and being 0.01 .Math.m or more and 0.5 .Math.m or less in particle size.