JPS60218845A - Apparatus for testing foreign matter - Google Patents

Abstract

PURPOSE:To conduct an accurate test of any fine foreign matter adhered on the surface of an LSI wafer or the like, by detecting the adhered position with an optical means while observing and analyzing it with a scanning microscope. CONSTITUTION:S polarization laser light is applied onto a wafer 1 by an S polarization laser 27 of a foreign matter detecting unit 12. A polarizing plate 29 is provided behind an objective 28. Any light passing through them is detected by a photoelectronic device 30, and then only the scattered light from a foreign matter (P polarization component) is detected for detecting the position of the foreign matter on the LSI wafer provided with a circuit pattern. At a leading edge of a foreign matter detection signal 23, outputs of encoders 15 and 20 are latched in a coordinate storage 22 so that the position of the foreign matter is stored therein. A movable stage 16 is moved by a motor 19 into the field or view of a scanning electron microscope SEM13. Motors 14 and 19 are driven by a material scanning unit 21 according to the data stored in the storage 22 so as to position the stages 11 and 16 appropriately. The signal from the SEM13 is analyzed to obtain data of the foreign material.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a micro foreign matter inspection device, and relates to a photomask for LSI, a reticle, a wear, etc. l) Reading cup 1f
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[Background of the invention]

Generally 1.For example, LSI, magnetic bubble memory, etc. are 1μm.
However, during the process of manufacturing masks and wafers, minute foreign matter may adhere, and these foreign matter may cause defects in the circuit patterns of manufactured masks and wafers. Become. Adhesion of foreign matter is
This occurs in many steps in the semiconductor manufacturing process.

Foreign object inspection detects not only the quantity but also the size.

Identification of the substance is also important.

Initially, visual inspection was performed using a microscope with a magnification of several hundred times to inspect foreign substances on LSI wafers, but this not only caused fatigue and decreased inspection efficiency, but also made it difficult to inspect one circuit pattern. With the miniaturization, it has become extremely difficult to inspect foreign substances in micron units.

Therefore, 1. For example, in the case of an object to be inspected that has a circuit pattern,
Laser light is irradiated onto the object to be inspected from relatively above to produce various diffusely reflected light? A ray of light from the r direction.

It has also been proposed to perform foreign substance inspection (for example, Japanese Patent Laid-Open No. 54-128682, Hitachi Review Vol. 1.62,
A11 page 15 and below).

However, although these foreign object inspection methods can detect the location of the foreign object, they cannot analyze the foreign object, detect the size of the foreign object that is comparable to or smaller than the wavelength of light, or analyze the composition of the foreign object.

For this reason, recently, a foreign matter inspection device using a scanning electron microscope (hereinafter abbreviated as "SEM") has been used.

Conventionally, as a foreign matter inspection apparatus using such an SEM, one having a configuration as shown in FIG. 1 is known.

Here, 51 is a cathode and 52 is an anode. 55, 54
Both are electronic lenses, but 55 functions as a condenser lens, and 54 functions as an objective lens. 1 is an LSI wafer, and 55 is an LSI wafer.
This is a deflection coil for scanning the surface of the SI wafer 1. When the electron beam is irradiated onto the LSI wafer 1, the LS
The surface of I sea urchin/11 generates secondary electrons, reflected electrons, X-rays, etc. depending on its shape, composition, etc.

They are detected by a detector 56. Next, 57 is an amplifier for amplifying the output from the detector 56, and the amplified output is supplied to the brightness modulation electrode of the CRT 5B.

40 is a deflection coil of the CRT5B. The output of the scan control circuit 59 is supplied to the electron beam deflection coil 55 and the CRT deflection coil 40. The scanning of the electron beam of the SEM and the scanning of the CRT 5B are synchronized, and a detection signal obtained by the detector 56 is displayed on the CRT 5B.

When such a foreign matter inspection device is used, foreign matter analysis 1 can be performed relatively freely; however, for example, when a foreign matter inspection is performed on a mirror wafer on which no circuit pattern is formed.

Since the SEN signal contains a large number of noise components, filtering processing takes time.

Fully automated inspection will take a long time.

Furthermore, since semiconductor devices and the like are formed on insulators such as Si and 5i02, if the 171 electron beam is irradiated onto the LSI wafer for a long period of time, the so-called charge-up phenomenon will occur, in which the surface of the LSI wafer is charged with electrons. 1 Image quality deteriorates and SiN becomes insufficient. .

If an Al thin film is deposited on the surface of an LSI wafer, the charge-up phenomenon can be prevented more than K, but this cannot be applied to an LSI wafer in the middle of the process. Sara K.

The electron beam is contaminated (carbon adhesion to the sample surface) I! There is a possibility that fi- damage may be caused to the LSI wafer.

Therefore, if low-acceleration SEN is used, these charge-up phenomena and contamination can be prevented, but the number of noise components increases, and full-scale automatic inspection requires a longer time.

Furthermore, for wafers with circuit patterns formed,
Unable to automatically classify patterns and foreign objects.

There was a drawback that automatic inspection could not be performed.

[Purpose of the invention]

An object of the present invention is to provide a foreign matter inspection device capable of analyzing the size, composition, etc. of fine foreign matter.

[Summary of the invention]

In order to achieve the above object, in the present invention, bt, LS
An optical means such as a laser that detects the position and size of foreign matter adhering to the surface of an I-wafer, etc., and a scanning electron microscope that analyzes the shape and composition of the detected foreign matter are placed in the same vacuum sample chamber. To provide a foreign matter inspection device according to the above.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

Note that the same reference numerals are given to the middle portions of the drawings. FIG. 2 is a configuration diagram showing an example of a foreign matter inspection device according to the present invention. 1o is a vacuum sample chamber, and 11 is a sample stage on which an object to be inspected such as an LSI wafer is placed. 14 is a motor for rotating the sample stage 11, and 15 is an encoder.

Reference numeral 16 denotes a moving stage, which moves between and within the fields of view of the foreign object detection unit 12 and the SEM 15 using optical means such as a laser. 19 is a motor for moving the moving stage 16.

It is connected to a moving stage via a screw 17 and a coupling 18. 20 is an encoder. Reference numeral 21 denotes a sample scanning section, which is connected to the motors 14 and 19 and controls their driving. Reference numeral 22 denotes a coordinate storage unit that stores the adhesion position of foreign matter adhering to the test sample of the LSI wafer 1. This coordinate storage section 22 is configured to receive a foreign object detection signal 25 detected by the foreign object detection section 12 and outputs from the encoders 15 and 20. When the foreign object detection section 12 detects a foreign object on the LSI wafer 1, the foreign object detection signal 25 becomes 1 level, for example, "Eiyk". 24 is a control section that controls the entire foreign object inspection apparatus. It is a window for replacement, and 26 is a vacuum pump.

The LSI wafer 1, which is the object to be inspected, is placed on the sample stage 11 in the vacuum sample chamber 10 through the sample exchange window 25.

A foreign object detection section 12 using an optical means such as a laser is shown in FIG. 5 (α), for example.

A foreign object on the LSI wafer 1, which is moving in a spiral manner by the motors 14 and 19, is detected. It rises to the level that detects foreign objects. At the rising edge, the output of the encoder 1520 is latched into the coordinate storage section 22, and the position of the foreign object on the LSI wafer 1 is stored. Therefore, the position of the foreign object can be obtained using polar coordinates. When the entire surface of the LSI wafer 1 or several chips have been inspected, the moving stage 16 is moved to the SE by the motor 19.
Move within field of view of M15. The position coordinates of the detected foreign object are stored in the coordinate storage section 22.

Based on the data, the sample scanning section 21 operates the motors 14 and 19.
The sample stage 11. Position the moving stage 16. This makes it possible to obtain an SEM signal of the foreign object at the position desired to be observed.

In the case of a mirror wafer having no circuit pattern on the LSI wafer, the foreign matter detection section 12 has the configuration shown in FIG. 4, for example. A laser beam from a laser 5 is irradiated from substantially directly above an LSI wafer 1 placed on a sample stage 11 that can rotate or translate.

Scattered light from foreign matter 5 attached to the surface of LSI wafer 1 is detected by detector 6, the detected value is amplified by amplifier 7, and the position and size of foreign matter 50 is stored in memory 8. By repeating this process, a foreign matter map on the LSI wafer 1 is created by the foreign matter map creator 9. Since the sample stage 11 can be rotated or translated, the LSI wafer can be moved so that the laser beam scans over the LSI wafer 1 in a spiral shape as shown in FIG. 5(a), and as shown in FIG. ) K can also be scanned as shown. Further, in the case of an LSI wafer with a circuit pattern, the foreign matter inspection section 12 has the configuration shown in FIG. 5, for example. In FIG. 5, the S-polarized laser beam 27 emits a
The SI wafer 1 is irradiated at an angle P. P is approximately 1 degree. Here, polarized light that vibrates perpendicularly to the plane formed by the irradiated laser beam and the wafer normal (Z-axis) is called S-polarized light, and polarized light that vibrates parallel to it is called P-polarized light. At this time, the polarization direction of the scattered light from the pattern portion on the LSI wafer 1 does not change, and S
Although the laser beam passes through the objective lens 2B as polarized light, the polarization direction of the laser beam that hits the foreign object changes, so it contains a large amount of P-polarized light component shown by the dotted line. Therefore, a polarizing plate 29 is provided behind the objective lens 28 to block the S-polarized light, and when the light that passes through this is detected by the photoelectric element 5o, only the scattered light (P-polarized light component) from the foreign object is detected. . This makes it possible to detect the position of a foreign object on an LSI wafer with one circuit pattern. Next, 5Eld15 is, for example, the first
The configuration shown in the figure can be used. The details have been described above, so they will be omitted. By analyzing the SEN signal from this SEM 15, foreign matter is analyzed. Note that if the foreign object detection signal 25 becomes Low level when a foreign object is detected on the LSI wafer 1, the encoders 15 and 20
is output from the coordinate storage unit 22 at the falling edge of the foreign object detection signal 25.
The position of the foreign object on the LSI wafer is stored.

Next, another embodiment of the present invention will be described based on FIG. In this embodiment, the foreign object detection section 12 and 5EN1
It is equipped with a mechanism that allows s to work more effectively on samples at the same location. That is.

Laser light emitted from the laser 42 is focused on the LSI wafer 1 via the beam expander 45 and the optical lens holder 44. The foreign object detection unit 12, which detects light scattered by foreign objects using a detector 45, can be moved in and out of the sample stage 11 by a motor 46. FIG. 6 shows the mode when foreign matter is detected. In the foreign matter analysis mode, the optical lens holder 44 moves to the right in the figure.

Then, only the 51M15 ICLSI wafer 1 within the field of view is placed, and the image of the foreign object can be observed. When detecting a foreign object, the LSI wafer 1 is continuously moved in a spiral by motors 14 and 19, and observed by SEH.

During analysis, the coordinate storage unit 22 and sample scanning unit 21 move the sample by a required amount. When 51M15 is not a long focal point (long working distance), the Z-axis mechanism 47 is used as necessary.

The Z-axis mechanism 47 rotates the LSI wafer 1 by a motor 48.
The focal point position 1 of 1M15 can be moved to, for example, the position 49, and a clear SEH image can be obtained.

In FIGS. 2 and 6, electrons are used as the excitation source, and L
If primary electrons reflected from the SI wafer 1 are detected by the detector 56, the surface of the SI wafer 1 can be analyzed using slow electron energy loss spectrum analysis, and even molecules and vibrational states can be investigated.

Similarly, if Auger electrons from the LSI wafer 1 are detected by the detector 56, single-element analysis becomes possible. .

Moreover, if a detector 56 for detecting X-rays is prepared.

Elemental analysis of minute parts is also possible. In this way, detailed observation and analysis including the composition of minute foreign matter can be performed.

〔Effect of the invention〕

According to the present invention, foreign matter adhering to the surface of an object to be inspected such as an LSI wafer can be detected at high speed by optical means such as an S-polarized laser, and at the same time can be observed and analyzed using a high-resolution scanning microscope. Therefore, fine foreign matter inspection can be performed accurately and without the risk of damaging the object to be inspected. Furthermore, since the location of foreign matter can be detected in a short time, the overall inspection time can be dramatically shortened. Therefore, the charge-up phenomenon in scanning electron microscopes can also be prevented. In addition, since foreign matter inspection can be performed at high speed and with high resolution, it becomes possible to check the manufacturing process, and it becomes possible to prevent the attachment of foreign matter, which is a major cause of lower yields of semiconductor products.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the structure of a scanning electron microscope, FIG. 2 is a block diagram showing the structure of a foreign matter inspection device according to an embodiment of the present invention, and FIG. 5 is a schematic diagram showing the scanning direction on the LSI Ueno 1. 4 is a block diagram showing the configuration of the foreign object detection section in the foreign object inspection apparatus according to the present invention when the object to be inspected does not have a circuit pattern, and FIG. A configuration diagram showing the configuration of the foreign object detection unit when the
FIG. 6 is a configuration diagram showing the configuration of a foreign matter inspection device according to another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... LSI wafer, 5... Foreign object, 11... Sample stage, 12... Foreign object detection part, 15... Scanning electron microscope, 14°19, 46, 48... Motor, 1
5.20...Encoder, 1681. moving stage,
21... Sample scanning section, 22... Coordinate storage section, 25.
... Foreign object detection signal, 24 ... Control unit, 27 ... S-polarized laser, 28 ... Objective lens, 29 ... Polarizing plate,
50... Photoelectric element, 51... Cathode, 32... Anode, 55, 54... Electronic lens, 55.40... Deflection coil, 56.45... Detector, 5B... CRT
,59...scan control circuit 1.42...ray v, 4
5... Beam expander, 44... Optical lens holder, 47... Z-axis mechanism. Figure 3, 4th item, 50th B

Claims (1)

[Claims] 1. A sample stage section on which an object to be inspected is placed, a drive section that moves this sample stage section in a predetermined movement, and a light beam irradiated to the object to be inspected on the sample stage section. A foreign matter inspection device comprising an optical system, a detection means for receiving reflected light from the object to be inspected and detecting information on the position and size of the foreign matter, and a scanning electron microscope equipped with an analysis means for the foreign matter. 2. The foreign object inspection device according to claim 1, wherein the detection means includes a foreign object information storage section that stores information about the position and/or size of the foreign object.