JP-7856536-B2 - Grinding device

JP7856536B2JP 7856536 B2JP7856536 B2JP 7856536B2JP-7856536-B2

Inventors

齋藤大
長井健

Assignees

株式会社ディスコ

Dates

Publication Date: 20260511
Application Date: 20220922

Claims (3)

A grinding apparatus for grinding a wafer held on the holding surface of a chuck table with a grinding wheel, A linear gauge that measures the height of the upper surface of the chuck table radially outward from the holding surface, or the height of the upper surface of the wafer held on the holding surface of the chuck table, Control unit and Equipped with, The linear gauge in question is, The device comprises: a contact shaft whose tip contacts the measuring surface or is positioned at a predetermined distance from the measuring surface; an air bearing that supports the contact shaft so that it can move up and down vertically; a detection unit that detects the height position of the contact shaft as it descends by its own weight; a lifting mechanism that raises the contact shaft; a case that houses the air bearing, the detection unit and the lifting mechanism; a through hole formed in the bottom plate of the case through which the tip portion of the contact shaft is inserted; a water film forming nozzle formed in the bottom plate of the case that communicates with the through hole and protrudes from the case to form a water film on the side surface of the contact shaft; and a water volume adjustment unit that adjusts the amount of water supplied to the water film forming nozzle. The control unit is A grinding apparatus comprising: a first flow rate control unit that sets the amount of water supplied to the water film forming nozzle to a small amount (first flow rate) by the water volume adjustment unit until the wafer is ground to a preset finish thickness; a second flow rate control unit that increases the amount of water supplied to the water film forming nozzle to a second flow rate greater than the first flow rate when the wafer is ground to a finish thickness; and a contact shaft raising control unit that, before raising the contact shaft, sprays the increased amount of water from the water film forming nozzle by the second flow rate control unit to fill the side surface of the contact shaft between the water film forming nozzle and the air bearing with water, and then raises the contact shaft.
The linear gauge is equipped with a cooling nozzle that supplies water to the outer surface of the case to prevent thermal deformation of the linear gauge. The system comprises a first supply passage that connects a water source to the cooling nozzle and supplies water to the cooling nozzle, a first valve that opens and closes the first supply passage, a second supply passage that connects the water source to the water film forming nozzle and supplies water to the water film forming nozzle, a second valve that opens and closes the second supply passage, and a flow rate adjustment valve that adjusts the amount of water in the second supply passage. The grinding apparatus according to claim 1, wherein the second flow control unit closes the first valve, opens the second valve, and increases the orifice diameter of the flow control valve, thereby supplying the water that was supplied to the cooling nozzle to the water film forming nozzle.
The grinding apparatus according to claim 1, wherein the entire surface of the contact shaft is coated with a water-repellent and water-sliding coating.

Description

This invention relates to a grinding apparatus for grinding a wafer held on a chuck table using a grinding wheel. In a grinding apparatus that grinds a wafer held on a chuck table using a grinding wheel, the thickness of the wafer during grinding is measured by a thickness measuring instrument. Some thickness measuring instruments measure the height of the wafer's top surface and the height of the chuck table's top surface, and determine the wafer's thickness from the difference between these two values. The wafer is then ground until the thickness measured by such a thickness measuring instrument reaches a predetermined thickness. Incidentally, thickness measuring instruments sometimes use a linear gauge that detects the height of the upper surface of the chuck table or the upper surface of the wafer held on the chuck table (see, for example, Patent Documents 1 and 2). This linear gauge comprises a contact shaft whose tip is positioned in contact with the measuring surface or at a predetermined distance from the measuring surface, an air bearing that supports the contact shaft so that it can move up and down vertically, a detection unit that detects the height position of the contact shaft as it descends by its own weight, a lifting mechanism that raises the contact shaft, a case that houses the air bearing, the detection unit, and the lifting mechanism, and a water film forming nozzle that forms a water film on the side surface of the protruding part of the contact shaft that protrudes from the case. In the linear gauge described above, a water film is formed on the side surface of the protruding portion of the contact shaft that extends from the case, thereby preventing grinding debris contained in the grinding water scattered by the rotation of the grinding wheel from adhering to the contact shaft. Therefore, during grinding, water is continuously sprayed from a water film-forming nozzle toward the protruding portion of the contact shaft case. Japanese Patent Publication No. 2020-118503Japanese Patent Publication No. 2022-067788 This is a perspective view showing a part of the grinding apparatus according to the present invention, broken off.This is an enlarged detail view of section A in Figure 1.This is a partial side cross-sectional view showing the configuration of the linear gauge of the grinding apparatus according to the present invention.Figure 3 is a magnified detailed view of the main part, where (a) shows the state of the wafer before it is ground to the finishing thickness, and (b) shows the state of the wafer after it has been ground to the finishing thickness.This figure shows the change in height of the grinding surface of the grinding wheel in the grinding apparatus according to the present invention over time.This is a flowchart showing the wafer grinding procedure in the grinding apparatus according to the present invention. The embodiments of the present invention will be described below with reference to the accompanying drawings. First, the configuration of the grinding apparatus according to the present invention will be described below with reference to Figure 1. In the following description, the arrows in Figure 1 will correspond to the X-axis direction (left-right direction), the Y-axis direction (front-back direction), and the Z-axis direction (up-down direction), respectively. [Configuration of the grinding device] The grinding apparatus 1 shown in Figure 1 grinds a disc-shaped wafer W, which is a workpiece, and comprises the following components. Specifically, the grinding apparatus 1 comprises a chuck table 10 that holds the wafer W and rotates around its axis, a grinding unit 20 that grinds the wafer W held by the chuck table 10, a thickness measuring instrument 30 that measures the thickness of the wafer W during grinding, a grinding feed means 70 that moves the grinding unit 20 up and down in a direction perpendicular to the holding surface 11a of the chuck table 10 (in the Z-axis direction), a horizontal movement mechanism 80 that moves the chuck table 10 in a direction horizontal to the holding surface 11a (in the Y-axis direction), and a control unit 90 (see Figure 3) as its main components. Here, the wafer W is composed of a single-crystal silicon matrix, and in the state shown in Figure 1, multiple devices (not shown) are formed on the downward-facing surface. These devices are protected by a protective tape T attached to the surface of the wafer W. The wafer W is held in place by suction on its surface (the bottom surface in Figure 1) to the holding surface 11a of the chuck table 10 via the protective tape T, while its back surface (the top surface in Figure 1) is ground by the grinding unit 20. Next, the configurations of the main components of the grinding apparatus 1—the chuck table 10, grinding unit 20, thickness measuring instrument 30, grinding feed means 70, horizontal movement mechanism 80, and control unit 90—will be described. (Chuck table) The chuck table