JP2001068390A - Semiconductor wafer - Google Patents

Abstract

(57) [Problem] To provide a semiconductor wafer in which characters or symbols for identification are laser-marked without deteriorating any of the items of strength, cleaning degree, and flatness of the semiconductor wafer. An individual character or symbol imprinted on a semiconductor wafer is formed by laser-marked dots, the diameter a of the dots is 15 to 50 μm, and the depth b is 0.1 to 1.0 μm. Yes, and outer ring height c
Was set to 0.1 to 0.5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer in which characters for identification are laser-marked on a front surface or a back surface of a semiconductor substrate.

[0002]

2. Description of the Related Art With the high integration of semiconductor devices, characters for identification, such as, for example, characters on the front surface or the back surface of the semiconductor substrate are required to secure traceability for managing characteristics of individual semiconductor substrates, device yield, and the like. It is necessary to write a lot number, a wafer number, and the like.

[0003] As a method of writing characters, a method using laser marking is generally known. This is a method of irradiating a sufficiently focused laser beam to a substrate and engraving characters by the heat. Characters engraved in this way,
There are two types: grooving type and dot marking type. The grooving type is engraved with letters as the name implies. In the dot marking type, a character is formed by an aggregate of dots (points).

[0004]

However, a semiconductor wafer on which characters have been engraved by a conventional laser marking method has the following problems.

[0005] In a semiconductor wafer provided with a grooving type character, the groove of the character has a depth of 30 μm or more. In addition, the generation of dust at the time of marking contaminates the wafer surface, the engraved powder accumulates on the outer periphery of the groove, and sintering causes a local step, causing problems such as deterioration of wafer flatness. . In particular, a local step at the time of backside marking causes image distortion in a circuit pattern transfer process, and a gap between a semiconductor wafer and a susceptor or an annealing jig in a process to which a heat treatment such as epitaxial layer growth or activation annealing is applied. This causes a fatal problem such as non-uniformity in the temperature distribution on the wafer surface.

Further, a semiconductor wafer provided with a dot marking type character hardly generates dust at the time of engraving because the wafer is locally melted.
Since the thickness is about 00 μm, it has a slight effect on the cracking and flatness of the wafer.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a semiconductor wafer in which characters or symbols for identification are laser-marked without deteriorating strength, cleanliness and flatness. is there.

[0008]

According to the present invention, in order to achieve the above object, individual characters or symbols imprinted on a semiconductor wafer are constituted by laser-marked dots.

The dots have a diameter of 15 to 50 μm, a depth of 0.1 to 1.0 μm, and an outer ring height of 0.1 to 0.5 μm.

[0010]

FIG. 1 is a schematic view of a laser-marked dot (dot). When a laser beam is applied to a semiconductor wafer, atoms of the wafer are thermally evaporated, and a hole having a diameter a and a depth b is formed according to the spot diameter and output of the laser beam. An outer ring is formed around the hole by diffusion of wafer atoms evaporated by heat and cooling. The height of this outer ring is assumed to be c.

The gist of the present invention is that the diameter a of the dots constituting the laser marking characters applied to the semiconductor wafer is 15 to 50 μm, the depth b is 0.1 to 1.0 μm, and the outer ring height c is 0.1 to 1.0 μm. 1 to 0.5 μm. In order to form such dots, it is important to select the spot diameter and output of the laser beam according to the thickness and size of the substrate, that is, in consideration of the thermal conductivity at the position where the laser beam is irradiated.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a compound semiconductor substrate, GaAs having a diameter of 4 inches
Using a substrate, Nd: YAG having an oscillation wavelength of 532 nm
The letters were engraved using a laser. The characters are engraved within a range of 4 mm from the second flat part of the substrate to the inside of the substrate. The number of characters is 16 characters, the character height is 1.6 mm, the character width is 0.8 mm, and the pitch between adjacent characters is 1.4 mm. .

FIG. 2 is a microscope observation image of a character which is laser-marked on the secondary flat portion on the back surface of the semiconductor wafer under the above conditions. It can be seen that a character is formed by a plurality of dots.

FIG. 3 is a sectional view of one dot portion of FIG. 2 observed by an atomic force microscope (AFM). The diameter of the marked dot is 20 μm, the depth is 0.16 μm, and the outer ring height is 0.12 μm, which is within the above-mentioned limited range. The flatness TTV (Total Thicness V) of this substrate
(ariation) was 1.41 μm.

FIG. 4 is a bird's-eye view of the secondary flat portion on the back surface of the semiconductor wafer of FIG. No abnormality was recognized in the laser marking part.

FIG. 5 is a bird's-eye view of the secondary flat portion when laser marking is performed with a dot shape higher than the laser output within the above range. A local step was recognized in the laser marking part. This step was at a level that caused image distortion in the circuit pattern transfer process. In this case, the diameter of the dot is 30 μm and the depth is 1.3.
μm, the outer ring height is 1.1 μm, and the substrate flatness TTV is 2.
It was 92 μm.

Next, when laser marking was performed with the dot shape lower than the laser output within the above range, the engraved characters were thin and difficult to distinguish.

The laser output in the above embodiment is adjusted so that the point having the above-mentioned optimum dimension is imprinted, and the result varies from laser device to laser device. is not. Further, although the GaAs substrate is used in the above embodiment, another compound semiconductor substrate such as InP may be used, and the engraved position may be any position of the main flat portion or the outer periphery of the substrate. In addition, the laser used for engraving has an oscillation wavelength of 106
A 4 nm Nd: YAG laser may be used. In that case, the laser output may be adjusted so that the engraved point in the above-described optimum range is formed.

[0019]

According to the present invention, the strength of a semiconductor wafer,
Without deteriorating any items of cleaning degree and flatness,
A semiconductor wafer on which identification characters are laser-marked can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of dots (dots) marked by laser.

FIG. 2 is a microscopic observation image of characters laser-marked on a secondary flat portion on the back surface of the semiconductor wafer according to one embodiment of the semiconductor wafer of the present invention.

FIG. 3 shows a portion of one dot in FIG. 2 by an atomic force microscope (AF).
It is sectional drawing observed in M).

FIG. 4 is a bird's-eye view of a secondary flat portion on the back surface of the semiconductor wafer of FIG. 2;

FIG. 5 is a bird's-eye view of a secondary flat portion when laser marking is performed with a high laser output.

[Explanation of symbols]

 a Diameter of the marked dot b Depth of the marked dot c Height of the outer ring of the marked dot

Claims (2)

[Claims] 1. A semiconductor wafer having characters or symbols engraved thereon, wherein said characters or symbols are constituted by laser-marked dots. 2. A dot having a diameter of 15 to 50 .mu.m, a depth of 0.1 to 1.0 .mu.m, and an outer ring height of 0.1 to 0.5 .mu.m. Item 2. A semiconductor wafer according to item 1.