JPS5961142A - Inspecting device of defect - Google Patents

Abstract

PURPOSE:To level up the detecting capability of defects and also to increase the yield of products while inspecting products such as wafers by superimposing necessary selective analog signals of bright visual field and dark visual field. CONSTITUTION:The laser beam, which is generated at the laser oscillator, is continuously vibrated in the determined direction by a deflector 3, and the spot light is scanned right and left on the chips 9, 9' of a wafer 8. Reflected beams on flat parts are fed in photomultipliers 10A, 10B through objective lenses 7, 7' and are delivered as signals of bright visual field, and are amplified at amplifiers 11A, 11B. In the meantime, the reflected beams in slanting parts are fed to photomultipliers 10C, 10D through ring-form lenses 15, 16, ring-form mirrors 13, 14 and light collecting lenses 17, 17', and is delivered as signals of dark visual field and are amplified at amplifiers 11A, 11B. Signals in the blight visual field and in the dark visual field are added in adders 12A, 12B. Unnecessary analog signals in the blight visual field are removed through gate circuits 18, 18' and analog switches S, S', the defects on chips are detected without mistake by comparing added outputs on a differential amplifier 12C.

Description

Detailed Description of the Invention (1) Technical Field of the Invention The present invention relates to optical defect detection of wafers, etc., and in particular detects defective parts of wafers, etc. using selective superposition of dark field and bright field. The present invention relates to a defect detection device.

(2) Background of technology In recent years, various manufacturing technologies have progressed as ICs, LSIs, etc. have been applied to various fields, and at the same time, the durability and reliability of these products have also improved. is being demanded. In order to satisfy these above requirements, for example, I
With regard to various inspection devices and the like for improving the reliability of C, LSI, etc., devices with even higher precision are being developed in conjunction with technological advances in related fields. These inspection devices mainly have both electrical and optical systems that are interrelated, so ways to improve accuracy include improving the electrical system, improving the optical system, or a combination of the two. There is.

(3) Prior art and problems Various methods have been proposed in the past for optically detecting defects in chips GL (etc.) of wafers.
Mainly, there are many error elements that the wafer itself gives to the detection system, making it difficult to distinguish it from a true defective part. This is because uneven grains are formed on the metal surface of the wiring pattern by sputtering or vapor deposition of .DELTA.1, for example, and a bright 111 image is generated during optical detection. However, the problem has been that it is difficult to distinguish between a defect signal generated by a true defect and the unevenness of the metal wiring portion that does not directly contribute to the defect.

FIG. 1 is an explanatory diagram of the optical system and electrical system of a conventional automatic inspection apparatus using vertical epi-illumination.

The laser beam generated from the laser oscillator 1 is, for example, expanded into a beam (luminous flux) to a predetermined width by an expander (inverted telescope) 2, and then continuously deflected from side to side by an ultrasonic deflector 3.
Let the summer move. Furthermore, the light is focused on different chips 9.9' on the wafer 8 through the half mirrors 4, 4', or the mirrors 5 and 4'', and through the objective lens 7.7', and corresponding patterns are simultaneously scanned in parallel. The reflected light from the thousand tube 9°9' returns to the original objective lens 7.7', that is, via the half mirror 4' or 4'', and is further transmitted to the photomultiplier tube (hereinafter referred to as photomultiplier) 10, "10". Light is converted into current at a predetermined conversion rate.The converted signals C and D are further amplified by an amplifier 1111' and input to a differential amplifier 12C.Here, both chips 9 and 9 on the wafer 8 ' are the same type of pattern and the same part is scanned at the same time, so both electrical signals C and D are originally the same type of signals.Therefore, if any signal is output after passing through the differential amplifier 12c, If so, this is because the shapes of both tip portions 9, 9″ are different, so the bottom mark is 10.10″.
It was thought that the defect signal was generated due to a difference in the amount of light incident on ', which was differentially amplified. However, in this case, even if irregular irregularities exist on the surface of the wafer 8, for example, in the metal wiring part, and even if both chips 9°9' have the same type of pattern, the irregularities in the metal wiring part of the former Chip 9.9' usually has a different waveform because it is different Denki Shinji, 0. -1D' occurs, resulting in a false defect signal.

Therefore, it becomes impossible to identify a true defective part. Similar results are obtained even when dark field is used.

Figure 2 (al is a cross-sectional view of the chip and Figure 2 (bl is the second cross-sectional view)
FIG. 5 is a correlation diagram illustrating the correlation between the chip cross-sectional view drawn directly above in FIG.

For example, in bright field mode, the objective lens 7.7', half mirror 4', 4
If the shape is oblique or perpendicular, the incident laser beam will not enter the objective lens 7.7' even if it is reflected.This signal waveform is As shown in Figure 2 (Fa), it changes depending on the unevenness of the surface of each chip and the thinness on the chip, so if only a bright field comparison is used, erroneous detection will occur when determining scratches etc. on the uneven parts. (FIG. 2 (bl solid line)) Next, in the dark field, reflected light from a portion of the chip having a diagonal shape enters the objective lens, and an electric signal is generated in the photomultiplier.

In addition, in a flat shaped part, the laser beam does not enter the objective lens after being reflected by the chip, and the electrical signal from the photomul during dark field becomes as shown by the broken line in Fig. 2 (bl).At this time, As is clear from the figure, the signal is completely opposite to that in the bright field. However, as in the bright field, the dark field signal changes depending on the unevenness of the surface of each chip, as shown in Figure 2 (a). This is a comparison of signals in the dark field.With Reno, there are false positives when it comes to identifying scratches on the chip.

(4) Purpose of the Invention The present invention solves the above-mentioned problems by simultaneously scanning each chip of the same pattern on the same web part with a laser beam, etc., and processing and comparing the reflected signals of bright and dark fields taken out. It is an object of the present invention to provide a defect detection device that inspects a chip 9H, and in particular does not judge normal irregularities on the surface of the chip as defects, but only determines irregularities as defects. purpose.

(5) Structure of the Invention The features of the present invention include: irradiation means for irradiating laser light onto a plurality of chips; a second converting means; and a third converting means for converting the lli field of light reflected on the chip into an electrical signal. a fourth converting means; and the third. The level of the electrical signal obtained by the fourth converting means determines the level of the electrical signal obtained by the first converting means. The first converter controls the output of the second converter. a second gate means; and said third gate means.
The output of the fourth converting means, and the output of the first converting means. The first . This is achieved by providing a defect detection device comprising a second addition means and detecting defects on a plurality of chips by comparing the outputs of the addition means.

(6) Embodiment of the Invention FIG. 3 is an explanatory diagram of the optical system-electrical system of an automatic inspection apparatus for detecting defects in a chip portion using the present invention.

Note that the same parts as in FIG. 1 are given the same reference numerals to avoid redundant explanation.

In the same figure, unlike the conventional example shown in FIG. 1, in which bright field and dark field optical information are taken in separately, half mirrors 4' and 4 send only bright field light to photomultipliers 1oA and 1oB.
'' and only the reflected light in the dark field are separated by another photomultiplier lOc, 10D.
Ring-shaped mirror 13.14 and Hayako lens 17.1 sent to
7' is provided. In addition, after converting the optical signal into an electrical signal and amplifying it in the photomaru IOC and IOD, the gate circuit 1
8.18' is provided, and when the signal is below a predetermined slice level value, an analog switch S is provided.

With S' turned off, the optical signal is converted into an electrical signal by the photomultipliers 10Δ and 10B, and the amplified signal is sent to the adders 12Δ and 12B.
You will not be able to enter it.

The laser beam generated from the laser oscillator l is continuously vibrated in a predetermined direction by the deflector 3, and tjc −y (,′l+
Similarly, the spot light enters the object lens while vibrating continuously from side to side, for example, and as the spot light is scanned from side to side on the wafer 8'' and the second chip 9,9l-.

The reflected light beam is 1-object lens 7.7', 〕〼＼-Fumi 1
-4', 4 to the photomultiple 10Δ, 101'3. Further, the photons 10C, 101 are incident on the ring-shaped lens 15.1 (i, ring-shaped mirror 13.14, and condensing lens 17°17). Potomaru) 0Δ～
The above-mentioned anti in IOD! 11 lights are converted. Hot 1-Maru 1
The output of 0Δ, 1013 is amplified by the amplifier 11Δ, II13, and the output of 7s1 Nogu Suinochi S is generated.

The signals are input to the single inputs of adders 12A and 12B through S'. Further, the output of the photomultiplier 10C210D is amplified by amplifiers 11C and 11D and input to the other inputs of adders 12A and 12B, respectively, and the gate circuit 18.
18'.

The outputs of adders 12A and 12B are respectively input to differential amplifier 12G.

Note that the gate circuits 18 and 18' turn on and off the analog switches s and s' according to a predetermined slice level (
This is a circuit that outputs g.

The beam of light irradiated to the chip 9'- is reflected on the surface, but
The reflection at the central part is input to the photomultiplier 108, +01 (through the objective lens 7.7').As a result, a bright field signal is output from the photomultiplier 10Δ, IOB, and is input to the amplifier 11A.
, 11B.

On the other hand, the reflection at f,'+01 (is the ring-shaped lens 15
．． []
. '4 rope j ha dark field i1 (number is 11-marked and 10C
3 lot) and is amplified by amplifiers 11Δ and IIB. Furthermore, the output is input to the gate circuit 18゜18, and as mentioned above, it is divided into two according to a specific slice level.
It is converted into a digitized signal. This binary signal turns on analog switches s and s'.

Turn off.

Adders 12Δ and 12B add the aforementioned bright field signal and dark field signal, and unnecessary bright field analog signals are removed by gate circuits 18° and 18' and analog switches s and s'. Therefore, this output becomes a signal corresponding to the pattern on the chip. This is compared using the differential amplifier 12C. As a result, scratches and the like on the thousand knobs can be detected without error.

FIG. 4 [al is the cross section of the semiconductor chip, and (bl~(
el is the electrical signal of data obtained in the dark field by the automatic inspection device using the present invention, the binary signal of the gate circuit, the electrical signal of the data obtained in the bright field, the electrical signal in the dark field and the gate circuit 18, 18' and 18' respectively show electrical signals obtained by combining or adding bright field electrical signals processed by analog switches s and s'.

In Figure 4, the same parts as in Figure 3 are designated by the same reference numerals.
1. Duplicate explanations will be omitted.

In FIG. 4 fa), the wiring portion 19 of the chip portion 9 on the wafer 8 is formed with unevenness due to the A pattern etc. due to the manufacturing process.
Further, a groove for a defective portion 20 is formed in the central portion. The reflected light on the chip in the dark field is particularly noticeable at the sloped surface or the convex portion having an acute angle.
It can be seen that the input is 5.16. (Figure 4(b)) Also, the closer the reflected light in the bright field is to the plane, the more the objective lens 7.7
' and is taken into the photomaru IOA and IOB.

(Fig. 4(d)) Also, depending on the signal in the dark field of Fig. 4(b), the outputs of the gate circuits s and s' have a waveform as shown in Fig. 4(c+), and the predetermined level of the electrical signal in the dark field. Only when the value exceeds the value shown in Fig. 4 (the bright field signal of dl is superimposed on the dark field signal and then compared), it is possible to detect the defective part 20 with good accuracy and high accuracy. becomes.

Furthermore, when there is a step difference in the pattern on the chip, the output of the dark-field optical system becomes a signal like the one shown at the right end of bl in FIG. 4.

The signal in the bright field is as shown in fd+ in Fig. 4, and is narrower at the base than the signal in the dark field. Therefore, the signal obtained by superimposing these signals becomes as shown in FIG. 4(e), and the signals at the pattern steps are not canceled out.

Zunawaji, the present invention corrects for specific irregularities on the surface by adding specific ranges of dark field and bright field.
Is it unevenness caused by scratches, etc.? ii) Since the signals of the two chips are not corrected, it can be determined whether each chip is normal or not by comparing the respective signals of the two chips.

It is also possible to use a floating slice level in which the gate circuit for extracting processed signals exceeding a predetermined value is provided with a differentiating circuit, an integrating circuit, or the like. In other words, because samples such as chips have irregularities, they are not all illuminated at a uniform level during actual light irradiation, and for example, when illuminating a part of a chip whose surface is slightly tilted, the balance of illumination light will be disrupted. Therefore, the signal height itself also changes. This floating slice level switches the slice level according to the changing height, and if the signal is high, it is switched at the top, and if it is low, it is switched at the bottom, so there is little consideration for unevenness in the wiring part due to A1 etc. inspection is possible.

In the embodiment of the present invention, the objective lenses 7 and 7' and the ring-shaped lenses 15 and 16 are provided separately, but they may be the same lens.

(7) Effects of the Invention According to the present invention, the ability to detect defective parts is dramatically improved by superimposing the selected analog signal of the bright field and the dark field as necessary when inspecting products such as Ueno products. Therefore, the yield of the product is also significantly improved. In addition, if inspection is performed at a floating slice level using a gate consisting of a differential and integral circuit during inspection, the slice level will rise and fall depending on the unevenness of the wiring section such as A1, so there is no need to consider troublesome lighting costs. Since it can be ignored, accuracy is further improved.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the optical system and electrical system of the automatic inspection device in bright field, Figure 2 (81, (bl is a correlation diagram between the chip cross-sectional view and the intensity of reflected light in bright and dark field, Figure 3) is an explanatory diagram of the optical system-electrical system of the automatic inspection device using the present invention, FIG.
are cross-sectional views of the semiconductor chip, and FIGS. It is a signal of the superposition of 1... laser oscillator, 3... deflector, 4.4',
4"... Half mirror 15, 13° 14... Mirror, 7.7'... Objective lens, 9.9'... Chip, IOA, IOB. 10C, IOD... Photomal, 12A. 12B... Adder, 12C... Differential amplifier, 1
3.14...Ring-shaped mirror, 15.16...
Ring-shaped lens, 18.18'...gate circuit,
s, s'...Analog switch.

Claims (4)

[Claims] (1) irradiation means for irradiating a plurality of thousand knobs with laser light; a second converting means; a third and fourth converting means for converting the dark field of reflected light from the second chip into an electrical signal; The first converter controls the output of the first and ff12 converters according to the level of the electrical signal obtained by the fourth converter. a second gate means; and said third gate means. The output of the fourth converting means, and the output of the first converting means. The first . 1. A defect detection device comprising a second addition means, and detecting defects on a plurality of chips by comparing outputs of the addition means. (2) Defect detection according to claim 1, wherein the bright field is vertically reflected light from above the chip, and the dark field is obliquely reflected light from above the chip. Device. (3) The defect detection apparatus according to claim 1, wherein the irradiation means includes a deflection means for scanning the chip by deflecting the laser beam. (4) The dark field is light reflected by a ring-shaped mirror placed on the top of the chip, and the bright field is light reflected by a half mirror on a disk placed above the chip;
2. The defect detection device according to claim 1, wherein the laser beam is irradiated onto the chip via the half mirror.