JPS63110626A - Optical discriminator of semiconductor wafer - Google Patents

Abstract

PURPOSE:To enable a bar code provided on a wafer to be read out by a method wherein a specific wave length from a light source is selected so that reflected ray from the first region (bar part) may be attenuated by the interference of a thin film while another reflected ray from the second region (space part) may not be attenuated by the interference. CONSTITUTION:The wave length of light 15 from a light source 14 is selected to atttenuate a reflected ray 17 from a thin film 12 (bar part) and another reflected ray 18 from a wafer 11 by interference. Assuming the wave length of light 15 as lambda, when an expression of an even number multiple i.e lambda/2(2m)=2nd cosgamma is satisfied, the reflected rays 17, 18 can be attenuated where m, n, gamma respec tively represent an arbitrary integer, the refractive index of thin film 12 and the total reflection of light 15 on the film 12. When the wave length of light 15 is selected as mentioned above, the signal level ratio of reflected ray on Al pattern 13 to another attenuated reflected ray on the thin film part 12 can be compared with each other satisfactorily to be read out as binary signals of 1 and 0.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] This is an optical identification device for semiconductor wafers that uses light interference caused by a thin film on a portion of a semiconductor wafer to select a specific wavelength to be attenuated and read at that wavelength.

[Industrial application field]

The present invention relates to an optical identification device for semiconductor wafers, and more specifically, the present invention relates to an optical identification device for semiconductor wafers. It relates to a device for reading a reader.

[Conventional technology]

The use of barcodes in logistics management is well known, and it is widely known that labels with barcodes printed on them are affixed to products, irradiated with a laser beam, and the reflected light is detected to identify the product. <It has been implemented.

In the manufacturing process of semiconductor devices, conventional wafers are
Five wafers are 10 feet long, and a number and identification number are written on the carrier, which is read by a person to manage the wafers.

[Problem that the invention seeks to solve]

In addition to the above-mentioned loft processing, there has recently been a demand for the management of each wafer, and research has been conducted into writing identification means such as numbers and symbols on each wafer and reading the means. It's starting to happen. One method is to print a number on the wafer using a laser beam and read it manually, but there is a desire to read it by some automatic means.

When reading barcodes, if there is dirt or scratches somewhere on the barcode, the detector will simply be unable to read the barcode and will not read it incorrectly.

On the other hand, if signs such as letters are written on a wafer and an attempt is made to automatically read them using mechanical or electrical means, there is a problem in that they may be read incorrectly if dust or the like is attached. Furthermore, since reading a label requires recognition of all of the marks, there is a problem that processing time is required and the reading device becomes expensive.

Therefore, it has been proposed to form a barcode on the wafer and detect it. Referring to FIG. 3, a thin 11Q12 (5iOz film or silicon nitride film) is deposited on the wafer 11.
is formed, and an aluminum (Aβ) pattern 13 is formed thereon by patterning using a normal adhesive lithography technique. Place the area where there is no A2 pattern in the first area (
21, Aβ pattern in the second area (space part)
22, and when a signal of "0" is obtained in the bar part 21 and a signal of "1" in the space part, the recognition of the sign is to read the signals of 0 and 1.

In a normal barcode, part of the bar is a claw bar, and the space part is a white part with nothing printed on it.The part of the bar reflects a lot of light and has a sufficient ratio of signal levels, so 1 and 0 can be separated. The signal is detected, but in the example shown in FIG.
The surface of 5iOz IIQ' is also a mirror surface, and there is a lot of specular reflection from there, and the surface of the Sj-based material under the SiO+ film is also a mirror surface, so there is a lot of total reflection from there, and there is a big difference in the signal level detected by the detector 16. do not have. In other words, the signal levels of O and 1 cannot be read because the ratio of signal levels is not sufficient. In FIG. 3, the barcode may be read by moving the wafer 11 in the direction of the arrow or by scanning the detector 16.

Furthermore, as the process for the wafer 11 progresses, a thin film is formed or etched on the barcode 2, causing the problem that the barcode surface becomes unstable.

The present invention was created in view of these points, and is an identification (ID) for managing the number of wafers in the semiconductor industry.
An object of the present invention is to provide a barcode reader in which the ratio of signal levels from a bar part 21 and a space part 22 is sufficiently high to ensure barcode detection when a barcode is used as a means for barcode detection. .

[Means for solving problems]

FIG. 1 is a sectional view of an embodiment of the present invention.

In the present invention, the reflected light 1 from the thin film 12 (part of the bar) is
The wavelength λ of the light 15 from the light source 4 is selected so that the reflected light 18 from the light source 7 and the wafer 11 is attenuated by interference.

[Effect]

When the 150 wavelength of light is λ, it is (iJ'l several times,
That is, when the relationship λ/2 (2m) = 2nd cos r is satisfied, the reflected light 17.18 is attenuated by interference.

Here, m is an arbitrary integer, n is the refractive index of the thin film 12, and γ is the total reflection of the light 15 on the thin film 12. By selecting the wavelength of the light 15 as described above, a sufficient signal level ratio between the reflected light from the Ae pattern 13 and the attenuated reflected light from the thin film portion is obtained, and the signal is read as a 1 and 0 signal. be.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

Referring again to FIG. 1, in the present invention, for example, the light from the white light source 14 is made to have a wavelength of λ using, for example, a prism 19.

There are two optical paths from the light 15: not only the reflected light 17 that is reflected by the surface of the thin film 12, but also the reflected light 18 that is totally reflected after passing through the thin film 12 and reaching the interface of the wafer 11. Light interferes with each other. Here, if the wavelength λ is selected so that the relationship λ/2 (2m) −2nd cos γ is satisfied, the reflected light 17
．． The reflected light produced by 18 is attenuated, and its wavelength is
The intensity is smaller than the reflected light reflected from the AN pattern 13 (this reflected light does not cause interference as described above, and the reflected light is 7 times brighter regardless of the wavelength λ), Since the ratio of the signal levels from the first area (bar part) 21 and the second area (space part) 22 is sufficient, each time a bar code is scanned at this wavelength,
signals can be read.

Even if a thin film is formed on the barcode, part 2 of the barcode is
Since the film thicknesses on the bar portion 21 and the space portion 22(i) are different, the wavelength that is attenuated in the bar portion 21 is not attenuated in the space portion 22, so that reading is possible.

In one embodiment, the thickness of the 5i02 film 12 is 400 mm.
In the case of 0 people, when the light of 6000 people is irradiated, the reflected light is attenuated due to interference at the bar part, and the reflection intensity is small. A
The intensity of the reflected light from the n pattern 13 hardly changed and a sufficient signal level ratio was obtained.

In order to obtain a light beam with a specific wavelength λ, a diffraction grating can be used in addition to the above-mentioned prism.

An example of the application of the invention is shown in the cross-sectional view of FIG.

In this application, a single white light source 1 is used in the example of FIG.
4 was used, a plurality of monochromatic light sources 14a, l/lb, 14c, . . . having different wavelengths are provided. Light from these monochromatic light sources is irradiated onto the par@Bt and space portions 22 of the wafer using a mirror 23, the signal level ratio is taken, a light source with a specific optimum wavelength λ is selected, and the barcode is read. That is, a monochromatic light source is selected in which the reflected light 17 and the reflected light 18 of the bar portion 210 are attenuated by interference.

Since the space portion 22 reflects most of the light regardless of wavelength, barcodes can be read by scanning with the specific wavelength. Detector 16a, 16b, 16c00
8. A plurality of (1&) are prepared corresponding to each wavelength.The optimum wavelength is a wavelength that satisfies the above-mentioned formula.

A monochromatic light source may be emitted using a laser chip, or an incandescent light source may be emitted using a diffraction grating to extract light of a desired wavelength. Furthermore, a combination of an incandescent light source and a prism as in the embodiment shown in FIG. 1 may be used.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to read the barcode provided on the wafer, and the wafer ID in the management of the number of wafers is automatically set to the correct value U(f).

[Brief explanation of the drawing]

Figure 1 is a sectional view of the embodiment of the present invention. Figure 2 is a cross-sectional view of an application example of the present invention. FIG. 3 is a sectional view of a conventional example. In Figures 1 to 3, 11 is a wafer; 12 is a thin film; 13 is A6 pattern, 14 is a light source; 14a, 14b, 14c are monochromatic light sources, 15 is light, 16 is a detector; 17 and 18 are reflected lights, 19 is prism, 21 is the first area (part of the bar), 22 is the second area (space part), 23 is a mirror. Agent: Patent attorney: Akira Kukimoto Sub-Agent Patent Attorney Yoshiyuki Osuga 7 Minato I7 Seiji 16 Figure 1 I

Claims (4)

[Claims] (1) In a device that provides a pattern for storing an amount of information on the surface of a wafer (11) and optically reads the amount of information in the pattern, the reflected light from the first region (21) interferes with the thin film (12). An optical identification device for a semiconductor wafer, characterized in that a light source having a specific wavelength (λ) is selected so that reflected light from the second region (22) is not attenuated due to interference. (2) The device according to claim 1, wherein the pattern for storing the amount of information is a bar code. (3) The wavelength (λ) of the light (15) from the light source (14) is
The reflected light (17) reflected from the thin film (12) and the wafer (1)
As reflected light (18) reflected from 1) interferes and is attenuated, λ/2(2m)=2ndcosγ. ．． ．． ．． ．． (1) (where m is an arbitrary integer, n and d are the refractive index and film thickness of thin film (12), and γ is the total reflection angle of light (15) with respect to film thickness (12)). The device according to claim 1, characterized in that the device is configured to. (4) Monochromatic light sources with different wavelengths (14a, 14b)
, 14c. ．． ．． ．． ．． ) and prepare detectors (16a, 16b, 16c...) corresponding to each monochromatic light source,
The apparatus according to claim 2, characterized in that the bar code is scanned by a monochromatic light source having a wavelength (λ) that satisfies equation (1).