JPS6297791A - Laser marking device - Google Patents

Abstract

PURPOSE:To execute with a high accuracy the marking of a semiconductor wafer, a glass plate, etc., by condensing a laser beam which has transmitted through an object to be worked, to the reverse side of the object to be worked, and also, to the surface, too. CONSTITUTION:In a laser beam 3a which has been emitted from a laser oscillator 1, a laser beam 3b which has transmitted through an object to be worked 2 is led to a concave reflecting mirror 6 which has been placed at the back of the object to be worked, and its reflected light is condensed to the reverse side of the object to be worked 2. On the other hand, by using an observation use optical device 7, marking is executed with a high accuracy by observing a point Q of the surface of the object to be worked 2. Also, on the upper side of the object to be worked 2, a convex lens 8 of a comparatively small diameter is provided, also a convex lens 9 and a plane mirror 10 are provided on the lower side of the object to be worked 2, and a mark is given simultaneously to the surface and the reverse side of the object to be worked 2. In this way, marking can be executed efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention uses a laser beam to mark alignment marks or loft numbers on at least the back surface of a plate-shaped workpiece such as a semiconductor wafer or a glass plate. The present invention relates to a laser marking device that applies laser marking using a laser marking device.

[Conventional technology]

Currently, YAG lasers are used for marking, etc.
Lasers are the most popular. Conventionally, a laser marking device that uses this YAG laser to apply a mark to a workpiece such as a semiconductor wafer 1- is already widely known.

Among these, a well-known device is one that applies marks to the back surface of a workpiece by switching the optical path of an optical device that guides a laser beam in a predetermined direction.

[Problem that the invention seeks to solve]

By the way, depending on the optical path switching means of the optical device in the conventional laser marking apparatus, it is extremely difficult to apply a mark at the same position on the front and back surfaces of the workpiece with high precision.

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser marking device that can easily and accurately mark the same position on the front and back surfaces of a workpiece.

[Means for solving problems]

The present invention has a configuration including a laser oscillator that generates a laser beam with a wavelength that partially passes through the workpiece, and an optical device that can focus the laser beam that has passed through the workpiece on the back surface of the workpiece, This aims to achieve the above-mentioned purpose.

〔Example〕

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

FIG. 1 is a schematic diagram showing an embodiment of a laser marking device according to the present invention. A laser oscillator 1 is configured to generate a laser beam 3 having a wavelength that partially transmits through a workpiece 2 (semiconductor wafer, glass plate, etc.). The Radhe beam 3 emitted from this laser oscillator 1 is expanded by a beam expander device 4 and guided to the workpiece 2 side in a state of low power density. To explain this in more detail, the laser beam 3 emitted from the laser oscillator 1 is transmitted through concave lenses 4as and convex lenses 4b constituting the beam expander device 4.
After successively passing through the laser beam 3a, the laser beam 3a with low power density
Then, it moves towards the Guicroic Mirror 5 side. After being reflected at 90 degrees by this guichroic mirror 5, it is guided to the workpiece 2 side.

Of the laser beams 3a, the laser beams 3b that have passed through the workpiece 2 first hit the concave reflecting mirror 6 placed behind the workpiece 2, and are reflected to a point P on the back surface of the workpiece 2.
The light is focused on the By this, this point P
A dot-shaped mark will be added to the . for example,
When the workpiece 2 is a silicon wafer with a thickness of 0.3 mm and the wavelength of the laser beam is 1.06 μm, approximately 25%
The laser beam will pass through the silicon wafer. Note that the optical device is composed of a beam expander device 4, a gicroic mirror 5, and a concave reflecting mirror 6.

On the other hand, the observation optical device 7 is disposed behind the guichroic mirror 5 and observes the point Q on the surface of the workpiece 2 via the guichroic mirror 5. Incidentally, the position of the mark at point P is exactly on the back side of point Q, and if the mark is provided at the position of point Q, a mark for pattern creation on both the front and back surfaces of the workpiece 2 can be obtained.

In this way, it has become possible to mark the same position on both the front and back sides of the workpiece 2 with high precision and with ease. In the device manufacturing process, it is possible not only to improve the accuracy of mask alignment on both the front and back sides, but also to shorten the manufacturing process.

FIG. 2 shows another embodiment of the laser marking device according to the present invention. In this embodiment, a convex lens 8 having a relatively small diameter is disposed above the workpiece 2, a convex lens 9 having a larger diameter than the convex lens 8 is disposed below the workpiece 2, and a reflecting mirror is disposed below the convex lens 9. This is a configuration in which lO is provided. Although not shown in FIG. 2, it is assumed that the laser oscillator 1, beam expander device 4, and gicroic mirror 5 are arranged in the same manner as in FIG. 1.

When using a laser marking device configured as described above,
A portion of the expanded laser beam 3a passes through the convex lens 7.
The light is focused on a point Q' on the surface of the workpiece 2, and this point Q
' is marked. At the same time, part of the laser beam 3a that has passed through the space other than the convex lens 8 is transmitted through the workpiece 2, and the transmitted laser beam 3b is transmitted through the convex lens 9 and then reaches the reflecting mirror 10. The laser beam 3b reflected by this reflecting mirror IO further passes through a convex lens 9, and then is focused on a point P' on the back surface of the workpiece 2, and a mark is placed on this point P'. In this way, in this embodiment, marks can be applied to both the front and back surfaces of the workpiece 2 at the same time.

Note that even if the surface of the workpiece 2 is grainy, the divergence angle of the laser beam 3b after passing through the workpiece 2 does not become very large, and by slightly increasing the diameter of the concave reflecting mirror 6 or the reflecting mirror 1o, the laser beam 3b can be sufficiently widened. can be focused on the back surface of the workpiece 2.

〔Effect of the invention〕

As explained above, according to the laser marking device according to the present invention, marks that can be used for mask alignment etc. can be easily applied with high precision at the same position on the front and back surfaces of the workpiece. In the manufacturing process of semiconductor elements in which circuits are formed from both the front and back sides of the workpiece, it is possible to not only improve the accuracy of mask alignment on both sides of the workpiece, but also to shorten the manufacturing process. It also has an extremely excellent effect.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of a laser marking device according to the present invention, and FIG. 2 is a schematic diagram showing a main part of another embodiment of the laser marking device according to the present invention. ■... Laser oscillator device, 2... Workpiece, 3.3a, 3b... Laser beam, 4...
... Beam expander device, 5... Gicroic mirror, 6... Concave reflector, 7... Observation optical device, 8.9...・Convex lens, IO...Parallel reflector. Applicant: NEC Corporation Representative

Claims (1)

[Claims] 1. A laser that includes a laser oscillator that generates a laser beam with a wavelength that partially transmits through the workpiece, and an optical device that guides the laser beam from the laser oscillator toward the workpiece. A laser marking device, wherein the optical device is configured to focus a laser beam transmitted through the workpiece onto the back surface of the workpiece. 2. The laser marking device according to claim 1, wherein the optical device includes a lens capable of focusing a laser beam from a laser oscillator onto the surface of the workpiece.