JPS62226290A - Reading device - Google Patents

Abstract

PURPOSE:To increase a reading accuracy by projecting successively plural laser light beams to an object to be inspected and utilizing the fact that the reflected light strength distribution difference of respective laser light beams different corresponding to the coarseness of a surface, obtaining the binarization signal for decoding for respective laser light beams. CONSTITUTION:A wafer 1 is held, moved and driven to the prescribed position of a mounting part 4. To the bar code forming position of the wafer 1 mounted at the mounting part 4, laser light 5 is irradiated from a laser light irradiating part 6 through a beam splitter 18a. The laser light 5 reflected by the wafer 1 is photodetected by a pair of photodetecting parts 7a and 7b and the output is inputted to an arithmetic processing part 8. The arithmetic processing part 8 obtains the binarization signal used for the decoding processing of the bar code and obtains the reading result for respective laser light beams 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates primarily to a reading device that automatically reads barcodes formed on semiconductor wafers.

[Technical background of the invention and its problems]

Recently, identification symbols are engraved by hand or with a laser marker on wafers for semiconductor devices made of single crystal silicon (So).This identification symbol is required for process control or quality control. In each actual process, the engraved recognition symbols are either visually checked by a worker for each sheet, or automatically read using a symbol recognition device with advanced pattern recognition functions. Ta.

However, the former visual inspection method not only imposes a heavy burden on each worker, but also has low efficiency.

In addition, there was a risk of misunderstanding the identification symbol. On the other hand, the latter method has disadvantages in that the equipment is expensive and the time required for symbol recognition is longer than in the case of visual inspection.

[Purpose of the invention]

An object of the present invention is to provide a reading device that can quickly and accurately read barcodes formed on, for example, wafers.

[Summary of the invention]

For example, multiple laser beams are sequentially applied to different positions of a surface to be inspected on which a barcode is formed by a combination of a bar part made of a rough surface and a space part made of a smooth surface, and then reflected at the barcode forming part. A binary signal used for decoding the barcode is obtained based on the diffusely reflected light, and a reading result is obtained for each laser beam.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the reading device of this embodiment.

This reading device holds the wafer (1) in a predetermined position and irradiates the wafer (1) with laser light as shown in FIG.
), and a loading part (4) that moves forward and backward along the arrow (3) direction, which is the direction of the orientation flat (1a) in which the barcodes (2) engraved in A laser beam irradiation unit (6) that irradiates a laser beam (5) to the barcode (1) formation site of the wafer (1) placed on it, and a laser beam (5) that irradiates the laser beam (5) reflected by the wafer (1). A pair of light receiving parts (7a) and (7b) that receive the reflected light distributed near the optical path through which the specularly reflected light passes and convert it into an electrical signal according to the amount of received light.
), an arithmetic processing section (8) that reads the identification symbol of the wafer (1) indicated by the barcode (2) based on the electrical signals output from the light receiving sections (7a) and (7b), and this arithmetic processing section. (8) LED displaying the reading result (
It consists of a light emission device (Dlode) and a display section (9) such as a cathode ray tube. Therefore, the loading section (4) includes a guide stand (10) and this guide stand α.
A table circle mounted on Q so as to be slidable in the direction of arrow (3), a feed screw α2 screwed into this table housing, and a feed screw α2 connected to one end of this feed screw α2.
and a motor α9 that rotates forward and backward to move the table υ forward and backward in the direction of arrow (3).

It consists of a vacuum adsorption mechanism α-guide which is installed on the table (11) and fixes the wafer (1) in a detachable manner. The vacuum suction mechanism I is installed at a distance from a flat plate-shaped suction holder having air intake holes (not shown) distributed on its upper surface, and is fluidly connected to the air intake holes. A vacuum source (not shown) and a wafer (1
) is comprised of a positioning pin (not shown) for positioning the barcode (2) so that the direction in which the barcode (2) is arranged is in the direction of the arrow (3). On the other hand, the laser beam irradiation unit (6) includes a semiconductor laser device (10) and this semiconductor laser device (uhp?).
x; out"1 (-1f-v-ze+t5) XL 2'r
”/f-17, a cylindrical diaphragm mechanism α η that adjusts the diameter of the laser beam (5) emitted from this optical system side, and a suction plate (a diaphragm disposed above the center part of the diaphragm). Mechanism α
It consists of a beam splitter (ISA) that splits the laser beam (5) emitted from the rod in the directions of arrows A, , and A. The beam splitter (18a) causes the irradiation trajectory of the laser beam (5) on the wafer (1) to change (B1) as shown in FIG.
).

Further, the laser beam (5) is adjusted to be branched to a position where the irradiation trajectory of the laser beam (5) on the wafer (1) becomes (B2). However, the irradiation trajectory (Bl
).

(B,) is perpendicular to the length direction of the bar portion (c), which will be described later, and intersects at the upper and lower end portions of the bar portion (to). Length, 2 directions (A4)
, (At), the laser beams (5), (5) are arranged to irradiate the irradiation positions (Ct), (Ct) on the wafer in FIG.

The distance between these irradiation positions (Cs) and (Ct) is set to be longer than the array length of the barcode (2). Also.

One light receiving section (7a) receives the laser beam (5) irradiated in the direction of the arrow (A1), and the other light receiving section (7b)
It is arranged at a position to receive the laser beam (5) irradiated in the direction of the arrow (At). These light receiving parts (7a), (
7b).

Since they have exactly the same structure, to describe one of them, there is an annular support plate α1 placed on the suction plate ttS opposite to the laser beam irradiation part (6), and a pair supported by this support plate (19). It consists of a first photoelectric converter (21) and a second photoelectric converter GlG arranged at a position to receive the laser beam (5) that has passed through the through hole (19a) of the support plate. Therefore, the first photoelectric converter (2G, +21
) is the diffusely reflected light 124) from the wafer (1) at symmetrical positions on both sides of the optical path of the specularly reflected light (c) of the laser beam (5) specularly reflected on the surface of the wafer 5(1). Receive light.

The position is adjusted so as to output an electric signal SA having a voltage corresponding to the amount of light received. Also.

The second photoelectric converter (4C) receives the specularly reflected light Q3I that has passed through the hole in the center of the support plate CL, and outputs an electric signal 8A having a voltage corresponding to the amount of received light. It looks like this. Furthermore, the arithmetic processing unit (8).

The first photoelectric converter ■ of each light receiving section (7a), (7b),
an amplifier (c) connected to the output side of the sha ) is connected to the output side of the decoder C31) for decoding the barcode (2) into a corresponding identification symbol;
9) and a control section t33, such as a micro-combiner, which outputs a control signal SR to a motor (13) for moving the table Uυ forward and backward.

Next, the operation of the reading device having the above configuration will be described.

The bar code 2) shown in Fig. 2 is engraved with a laser marker, and is located on the bar portion θ1, which is directly irradiated with laser light and has a rough satin-like surface.
. . , and a space portion 0i) that is not irradiated with laser light and is a smooth surface (see Fig. 3).

A desired code is indicated by the width of these bar portions (g) and space portions c34). Note that both ends of the barcode (2) are bars for starting and ending reading, respectively. First, the wafer (1) is placed on the suction plate (
15 in a predetermined position. Then, by the control signal S output from the control section (3).

Position the table 0υ to the reading preparation position. Then,
Laser beams (5), (
5) Irradiate. Next, point the table (11) with the arrow (
3) move forward at a constant speed in the direction. As a result, first, the laser beam (5) in the direction (81) at the irradiation position (C1) is
A portion of the wafer (1) where the barcode (2) is formed is irradiated along an irradiation trajectory (B,) perpendicular to the longitudinal direction of the bar (...).

Subsequently, the laser beam (5) in the direction (A, ) is applied to the barcode forming part 2) of the wafer (1) at the irradiation part t(Cz).

Irradiation is performed along an irradiation trajectory (B2). As a result, from the wafer (1) irradiated with the laser beams (5), (5), the specular reflection light (c), (c) and the diffuse reflection light (to) of the laser beam (5), (5), CI! 41 is reflected. And, specularly reflected light (c), (231 is one hole (19a)
, (19a) is received by the second photoelectric converter (2), and the electric signal 8A; , SA; is output to the binarization circuit (to). On the other hand, the diffusely reflected light (c), 04) , Photoelectric converter-'1llll Inn 1111
1 A11l If Shil/'1 Relative Umu J
P-1-1771": 2-E2-, Knee, 11-
.

An electrical signal SA, which has a voltage of a magnitude corresponding to the amount.

SA is output to the amplifier (c) (see Fig. 1).

By the way, FIGS. 4 and 5 show the reflected light distribution at the bar part (2)... and the space part G41... at the first photoelectric converter (A), ω, +21), (2I) position. The relationship between the intensity and the angle θ with respect to the optical path of the specularly reflected light (C) and (C) is shown. In other words, as shown in FIG.
5), a part of (5) is diffusely reflected, and the intensity distribution of the 1 reflected light becomes irregular, with peaks occurring on both sides of the optical path of the specularly reflected lights (c) and (c). However, the space part G・υ...
Since the 9 surface is a smooth surface in . . . , the 1 reflected light intensity distribution has a sharp symmetrical mountain shape with a peak at the angle θ of zero. In other words, the diffusely reflected light (2) when the laser light (5), (5) is incident on the bar part (2)...
4), (The light amount of 241 is the space part C34)...
This is much more than when the laser beams (5) and (5) are incident. Particularly in sections (L) and (M) in Figures 4 and 5 (where θ is around 3°).

Part of the light amount of diffusely reflected light, tl, C24) OJ...
・and space part body mountain)...F+r6 is a short trick, and using this suhi τ rre, one part Cyu... and space part (b)... can be clearly distinguished.

Therefore, in the binarization circuit □□□, some partial values and
The electric signal SA4 is a threshold voltage value vT for distinguishing between the space portion (2) and the space portion (2).

Set based on SA. That is, in the binarization circuit, as shown in FIG. 6, the electric signal f13Al.

A threshold voltage value is set that is directly proportional to the voltage of SA.

Thus, the electrical signal SB input to the binarization circuit (to),
.

SB! are sequentially binarized from the threshold voltage value vT, and the binarized signals sc, , sc, are output to the decoder Gυ. That is, in this binarized No. 8 SC1, SC, the part indicating the bar part (g)... is set to logic "0", and the part indicating the space part light υ... is set to logic "1". "It has become. The binary signals '44fSC, , SC, indicate barcode (2). Therefore, the decoder G outputs the binary signal 8C in synchronization with the control signal S.
, , SCt are identification signals 8D1 . . . SCt indicating the identification symbol of wafer (1). It is decoded to SD. Next, decoder G
From υ, a different number SD1゜SD, control i1 part 0 crocodile h
The wafer (1) is outputted to the next i and stored in its memory, and the identification symbol of the wafer (1) indicated by the barcode (2) is displayed in parallel on the display wS (91).
If dust or dirt is attached to a part of the barcode row (2) (for example, on the irradiation trajectory (B)), the identification signal SD
, are not output from the decoder 3v. However, since the irradiation trajectory (identification symbol 8D corresponding to B) with no dust or dirt attached is output, this is displayed on the display section (9).

In this way, the reading device of this embodiment can
Laser light between ... and space part 041... (5)
, (5) is used to clearly distinguish between the two, and to obtain binary signals 8C, , SC, indicating the barcode. It can be decoded with high precision, eliminating the possibility of misidentification. especially.

In this example, irradiation is performed at two different positions N (irradiation loci (Bt), (Bt)) of the barcode (2).

Even if part of the barcode (2) becomes unreadable due to dirt or dust, the pair of laser beams (5), (5
), the reading process can be performed based on one of the laser beams (3), improving the accuracy and reliability of reading.

Note that the table (11) may not be moved (the laser beam irradiating section (6) and the light receiving section (7) may be moved).Furthermore, one reflected laser beam may be received via an optical fiber. Furthermore, the number of photoelectric converters is not limited to two, and two or more photoelectric converters may be arranged along the periphery of the through hole.Alternatively, if there is no problem with detection accuracy, a spot-like photoelectric converter may be used. It may be one.Furthermore, in the above embodiment (in this case, the laser beam (5) is connected to the beam splitter (18a)
Although the laser beams are separated into two laser beams (5) and (5), the number may be arbitrary. Also, without using a beam splitter.

A plurality of laser beam irradiation units may be provided depending on the number of required laser beams. Furthermore, one aspect of the present invention is that the object to be recorded is formed by utilizing the roughness of one surface in addition to barcode reading.

Applicable.

〔Effect of the invention〕

The reading device of the present invention sequentially projects a plurality of laser beams onto an object to be inspected, and utilizes a method in which the reflected light intensity distribution difference of each laser beam differs depending on the roughness of the surface17. Since a binary signal is obtained for each laser beam, not only reading accuracy but also reading reliability is improved.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a reading device according to an embodiment of the present invention, FIG. 2 is a horizontal view showing a barcode, FIG. 3 is a timing chart showing a barcode decoding process, and FIGS. The figures are a reflected light intensity distribution diagram of the space portion and bar portion of the barcode, respectively, and FIG. 6 is a graph showing a method of setting the threshold voltage value in the binarization circuit. (1)...Wafer (object to be inspected), (2)...Barcode. (4)...Mountain part (scanning part), (5)...Laser light. (6)... Laser light irradiation unit, (8)... Arithmetic processing unit 5a]... Support plate (support body), (2Q, C, 'l)
...First photoelectric converter. (/40...Second photoelectric converter, ci...Specular reflected light. CI!4)...Diffuse reflected light, (19a)...
・Through hole. (To)...Binarization circuit, I3υ...Decoder (reading section). Agent Patent Attorney Noriyuki Chika Same as above Shinji Takehana Diagram 1 Angle θ 14 Diagram Le No. 58

Claims (2)

[Claims] (1) A symbol to be recognized formed on an object to be inspected, in which a plurality of first portions with rough surface roughness and a plurality of second portions with a smoother surface than the first portions are arranged in a row. a laser beam irradiation section that irradiates laser beams to different positions; and a plurality of laser beams that hold the object to be inspected and move it relative to the laser beam irradiated from the laser beam irradiation section. A scanning unit that scans the symbols to be recognized in the direction in which they are arranged, and a scanning unit that is separately disposed at a position to receive the specularly reflected light of each laser beam irradiated to the symbol to be recognized, and that passes the specularly reflected light. a plurality of supports having through holes bored therein, and a plurality of supports supported by the respective supports and receiving diffusely reflected light reflected from the recognition target symbol of the laser beam in the vicinity of the through holes, and the plurality of supports correspond to the amount of light received; a plurality of first photoelectric converters for photoelectrically converting the first detection signal into a first detection signal; and a plurality of first photoelectric converters arranged at positions to receive specularly reflected light that has passed through the through holes of each of the supports, and corresponding to the size of the specularly reflected light. a plurality of second photoelectric converters that photoelectrically convert the plurality of second detection signals into a plurality of second detection signals; A threshold value is variably selected for making a sharp distinction, and the first detection signal is binarized using the selected threshold value.
It comprises a digitization circuit, and a reading unit that performs recognition processing of the symbol to be recognized based on at least one readable binary signal among the plurality of binary signals output from the binarization circuit. A reading device characterized by: (2) The reading device according to claim 1, wherein the symbol to be recognized is a barcode symbol.