CN-113739716-B - Wafer inspection apparatus and wafer inspection method

CN113739716BCN 113739716 BCN113739716 BCN 113739716BCN-113739716-B

Abstract

The invention provides a wafer inspection device and a wafer inspection method, which precisely determine the formation state of a modified layer in a wafer. The wafer inspection apparatus includes a holding table capable of holding a wafer with a back side of the wafer exposed upward, a point light source that emits light that irradiates the back side of the wafer held by the holding table, and an imaging unit that images reflected light of the light emitted from the point light source and irradiated onto the back side of the wafer, the imaging unit including an imaging lens that faces the wafer held by the holding table, a beam splitter positioned at an imaging point of the imaging lens, and a camera disposed on a first optical path branched by the beam splitter, the point light source being disposed on a second optical path branched by the beam splitter, a collimator lens that generates light emitted from the point light source as parallel light, and a condenser lens that condenses the parallel light generated by the collimator lens onto the beam splitter.

Inventors

Kimura Show

Assignees

株式会社迪思科

Dates

Publication Date: 20260508
Application Date: 20210525
Priority Date: 20200528

Claims (3)

1. A wafer inspection apparatus for inspecting a wafer having a modified layer formed therein, characterized in that, The wafer inspection apparatus includes: a holding table capable of holding the wafer in a state in which a back surface side of the wafer is exposed upward; A point light source for emitting light to irradiate the back surface side of the wafer held by the holding table, and A photographing unit photographing reflected light of the light emitted from the point light source and irradiated onto the back surface of the wafer, The photographing unit includes: An imaging lens facing the wafer held by the holding table; a beam splitter positioned at an imaging point of the imaging lens, and A camera arranged on a first optical path branched by the beam splitter, The point light source is arranged on a second optical path branched by the beam splitter, The light emitted from the point light source is a laser beam, A collimator lens that generates light emitted from the point light source into parallel light and a condenser lens that condenses the parallel light generated by the collimator lens on the beam splitter are disposed on the second optical path.
2. The wafer inspection apparatus according to claim 1, wherein, The wafer inspection apparatus further has a moving unit that relatively moves the holding table and the photographing unit.
3. A wafer inspection method for inspecting a wafer having a plurality of predetermined dividing lines intersecting each other on a front surface and devices formed in regions of the front surface divided by the predetermined dividing lines, by positioning light-condensing points inside the wafer and irradiating the wafer with a laser beam having a wavelength transparent to the wafer, characterized in that a modified layer is formed in the wafer along the plurality of predetermined dividing lines, The wafer inspection method has the steps of: A holding step of holding the wafer with the front surface of the wafer facing the holding table and the rear surface side being exposed upward by the holding table; an irradiation step of irradiating the light emitted from the point light source to the back surface of the wafer through the collimator lens, the condenser lens, the beam splitter, and the imaging lens; an imaging step of imaging the reflected light of the light irradiated onto the back surface of the wafer by the irradiation step and reflected by the back surface and reaching the camera via the imaging lens and the beam splitter to form an imaged image, and A determination step of determining a formation state of the modified layer formed inside the wafer based on the photographed image obtained by the photographing step, The light emitted from the point light source is a laser beam.

Description

Wafer inspection apparatus and wafer inspection method Technical Field The present invention relates to a wafer inspection apparatus and a wafer inspection method for inspecting the shape of a modified layer of a wafer having the modified layer formed therein. Background In a process for manufacturing a device chip for an electronic device such as a mobile phone or a personal computer, first, a plurality of dividing lines intersecting each other are set on the front surface of a wafer made of a material such as a semiconductor. Devices such as ICs (INTEGRATED CIRCUIT: integrated circuits) and LSIs (LARGE SCALE Integration: large-scale integrated circuits) are formed in the respective regions divided by the lines to divide. Further, when the wafer is thinned to a predetermined thickness and then divided along the dividing line, device chips can be formed. When dividing a wafer, a laser beam having a wavelength (a wavelength that can pass through the wafer) that is transparent to the wafer is condensed inside the wafer along a predetermined dividing line, thereby forming a modified layer that serves as a dividing start point. When an external force is applied to the wafer, the crack extends from the modified layer to the front and back surfaces of the wafer, and the wafer is divided along the dividing line (for example, refer to patent documents 1 and 2). Here, if the modified layer is not formed properly inside the wafer, the wafer may not be divided properly, and damage may occur to the wafer. Therefore, when the modified layer is formed, the presence or absence of the micro-roughness is detected by irradiating the back surface of the wafer with light and capturing reflected light. The image in which the reflected light is reflected emphasizes the concave-convex shape. This phenomenon is called a magic mirror, and a technique for detecting the presence or absence of a modified layer using the magic mirror has been developed (see patent document 3). Patent document 1 Japanese patent No. 3408805 Patent document 2 Japanese patent No. 4358762 Patent document 3 Japanese patent application laid-open No. 2017-220480 Here, in order to detect the formation state of the modified layer with high accuracy, it is necessary to obtain a clear captured image. However, since the contrast of the reflected light image tends to be easily lowered, it is not easy to precisely determine whether or not the modified layer is present. Disclosure of Invention The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a wafer inspection apparatus and a wafer inspection method that can obtain an image of reflected light with good contrast and clarity, and can precisely determine the formation state of a modified layer inside a wafer. According to one aspect of the present invention, there is provided a wafer inspection apparatus for inspecting a wafer having a modified layer formed therein, the wafer inspection apparatus including a holding table capable of holding the wafer in a state in which a back surface side of the wafer is exposed upward, a point light source for emitting light to be irradiated to the back surface side of the wafer held by the holding table, and an imaging unit for imaging reflected light of the light emitted from the point light source and irradiated to the back surface of the wafer, the imaging unit including an imaging lens facing the wafer held by the holding table, a beam splitter positioned at an imaging point of the imaging lens, and a camera arranged on a first optical path branched by the beam splitter, the point light source being arranged on a second optical path branched by the beam splitter, a collimator lens and a condenser lens being arranged on the second optical path, the collimator lens generating light emitted from the point light source as parallel light, the condenser lens generating the parallel light with the collimator lens. Preferably, the wafer inspection apparatus further has a moving unit that relatively moves the holding table and the photographing unit. In addition, it is preferable that the light emitted from the point light source is a laser beam. In accordance with another aspect of the present invention, there is provided a wafer inspection method for inspecting a wafer having a plurality of predetermined dividing lines intersecting each other on a front surface, the wafer being formed with devices in regions of the front surface divided by the predetermined dividing lines, the wafer being inspected by the wafer inspection apparatus according to any one of claims 1 to 3, wherein a modified layer is formed in the wafer along the predetermined dividing lines by locating a light collecting point inside the wafer and irradiating a laser beam having a wavelength transparent to the wafer, the wafer inspection method comprising a step of holding the wafer with the holding table in a state in which the front surface