JPS6063449A - Defect inspection equipment - Google Patents

Abstract

PURPOSE:To examine foreign matters on the surface of an object having a rugged surface by judging only the reflected light of light for examination, which can be detected with all of plural detecting means, as the reflected light from foreign matters. CONSTITUTION:The light for examination is irradiated from above the center part of a semiconductor wafer 9, and the reflected light is detected simultaneously by plural reflected light detecting means 17 which are provided to face individual directional step faces 20. Since the reflected light from a foreign matter 22 has all directions and is detected by all detecting means though the reflected light from the step face 20 has directivity and is detected only by a specific detecting means in accordance with the direction, the foreign matter 22 is detected in distinction from a pattern consisting of ruggedness provided on the semiconductor wafer 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a foreign matter inspection device for detecting defects such as foreign matter present on the surface of an object, and is mainly directed to a foreign matter inspection device for visually inspecting the surface of a semiconductor wafer. It is something. For example, Japanese Patent Laid-Open No. 85793/1983 discloses an appearance inspection technique in which defects in the mask are detected by irradiating light onto a mask or the like and using the reflected light.

Foreign matter often adheres to the surface of a semiconductor wafer during the manufacturing process of semiconductor devices. The foreign matter becomes an important factor in determining the yield of semiconductor devices, and it is necessary for process control to know the size, number, etc. of the foreign matter. Therefore, inspection for foreign substances on semiconductor wafers is performed between actual semiconductor device manufacturing processes.

Conventional foreign object inspection generally involves
Metallurgical microscope (100-200x magnification) as shown in bl.
This was done using a visual inspection method. However, this method has the problem that the inspector's subjectivity is easily involved in determining whether or not there is a foreign object, and the inspection results vary depending on the inspector.In addition, the inspection takes time (2 to 3 hours for one semiconductor wafer), and the process is slow. There was a problem that the test results during the process could not be quickly reflected in process control, making it impossible to effectively prevent a decrease in yield.

For this reason, automatic foreign particle inspection was considered, but as shown in Figure 2, the surface of the semiconductor urchin is uneven because it has been etched to form a semiconductor device.
Since it is extremely difficult to automatically distinguish between this and foreign matter, foreign matter inspection has had to be carried out by visual inspection.

An object of the present invention is to solve this problem and to enable automatic inspection for foreign substances.

One embodiment of the present invention to achieve the above object is a method for inspecting foreign matter on the surface of an object having an uneven surface and a plurality of stepped surfaces due to the unevenness. A plurality of detection means for detecting are arranged on each step surface in each of the above directions, and the reflected light of the inspection light beam irradiated onto the object surface is simultaneously detected by the plurality of detection means, and the detection means is detected by all of the plurality of detection means. This method is characterized in that only the reflected light that is generated is determined to be the reflected light from a foreign object.

The present invention will be explained below with reference to Examples.

FIG. 3 shows a related foreign matter inspection method devised by the inventor.

5 is an XY table for inspection, 6 is a leaf spring for focusing, 7 is an automatic focusing device, 8 is a wafer mounting table, 9 is a semiconductor wafer to be inspected, 10 is an objective lens, 11 is a mirror for irradiating observation illumination light, 12 is a 13 is an observation illumination lamp, 14 is a burisma for switching the field of view, 15 is an eyepiece for visual observation, 16 is an eyepiece for automatic inspection, 17 is a photodiode array for detecting reflected light and converting it into an electrical signal ( Detector) calculates this output and automatically performs foreign object inspection.

Reference numeral 18 denotes an inspection light source, which is installed in the same number as the number of directions (fffi types) of uneven stepped surfaces of the semiconductor wafer to be inspected, and each of them repeats blinking in a certain order to emit an inspection light beam to the semiconductor wafer. The mechanism is such that the direction of irradiation changes.

FIG. 4, 181, lbl is an explanatory diagram showing the inspection principle of this foreign matter inspection method.

This inspection method is based on the fact that the etchings that exist on the surface of a semiconductor wafer are generally applied so as to form an orderly pattern, as shown in Figure 8 of the photo, and the directions of the stepped surfaces are limited to a certain number. Assuming that, the side surfaces of uneven surfaces in each direction reflect well only the inspection light beam from the opposite angle, and hardly reflect the inspection light beam from other angles. It is a protrusion with side surfaces in the same direction, and utilizes the fact that the inspection light beam from any angle is reflected in the same way.

That is, as shown in FIG. 4 1al, the irradiation direction of the inspection light beam can be changed in directions of 1, 2 degrees and 3.4 degrees corresponding to each direction of the stepped surface. 19 is a convex surface, 20 is a stepped surface, 21
If is a concave surface and 22 is a foreign object, then A.

When the inspection light beams in directions 1, 2, 3, and 4 are irradiated to each position B and C, the reflected light is as shown in FIG. 4 181.

In other words, the part shown to the person reflects only the inspection beam in direction 2, and the part shown in B reflects only the inspection beam in direction 1, whereas the part shown in C has a foreign object, so it reflects only the inspection beam in direction 1.
．． 2.3.4 all test beams are reflected in the same way.

Therefore, by changing the irradiation direction of the inspection light beam in accordance with the direction of the uneven step surface of the semiconductor wafer to be inspected, multiple detection results are obtained, and only the reflected light that is commonly recognized in all the detection results is used to detect foreign particles. Foreign matter inspection can be performed by determining that the light is reflected from the object. Such inspections can be performed automatically through computational processing, so there is no human subjectivity involved in the inspection results, the inspection time is extremely shortened, and the inspection results can be promptly reflected in process control. .

FIG. 5 shows an example of a mechanism for changing the direction of the inspection light beam in a fixed order.

23 is a light source, 24 is a lens, 25 is a mirror, 26 is a motor for rotating the mirror 25, 27 is a frame body, 28
is a light guide hole for inspection.

In this mechanism, the light beam from the light source 23 is directed in one direction by a mirror 25, and the direction is changed by rotating the mirror 25 by a motor 26.The rotation speed or rotation period of the mirror 250 is
This can be determined by detecting light from one hole 29 provided in the handle portion of 5 with a photodiode 30.

The light that has passed through the guide hole reaches the inspection light source section 18 through the light guide, and is further irradiated onto the surface of the semiconductor wafer.

FIG. 6 shows another example of a mechanism for changing the direction of the inspection light beam in a fixed order.

A rotating plate 31 is provided opposite the light source 23, and the rotating plate 31
The light beam is sent to the light source section through one hole 32 provided in the. 33a to 33d are glass fibers for light beam propagation, and by rotating the rotary plate 31, the holes 3
If the position of 2 is changed, the light source that irradiates the light beam will also change.

FIG. 7 shows an embodiment of the present invention. In this embodiment, an inspection light beam is irradiated from above the center of a semiconductor wafer, and a plurality of reflected light detection means 17 provided opposite to the stepped surfaces in each direction are used. At the same time, reflected light is detected, and all detection means 17
This is an inspection method in which only the light detected by this method is determined to be reflected light from a foreign object. The reflected light from a stepped surface has directionality, so depending on the direction, the reflected light can be detected only by a specific detection means, whereas the reflected light from a foreign object reflects in all directions, so all detection means can detect the reflected light. It is from.

On the other hand, foreign matter can be thought of as an accumulation of minute side surfaces whose surfaces have different directions, and light irradiated from any direction is reflected in almost the same way. Therefore, according to the present invention, foreign matter can be It can be detected in distinction from a pattern consisting of irregularities intentionally provided on the wafer.

The present invention can be applied not only to semiconductor wafers but also to a method for inspecting foreign matter adhering to the surface of an object having regular irregularities in general.

[Brief explanation of the drawing]

FIGS. 1A and 1B are explanatory diagrams showing a conventional foreign matter inspection method, respectively, and FIG. 2 is a sectional view showing the surface condition of a semiconductor wafer. Fig. 3 is an explanatory diagram showing the related foreign matter inspection method devised by the inventor, Fig. 1 (1al + tb)
is an explanatory diagram for explaining the principle of the above example, ta+ is a plan view of the part to be inspected, and 11)l shows the reflected light detection results at each position when the direction of the inspection light beam is changed. FIGS. 5 and 6 are cross-sectional views showing a 1:1 configuration of the light source used in the above example. FIG. 7 is an explanatory diagram showing an embodiment of the present invention. el, 2.3.4... Direction of inspection light beam, 5... XY table, 6... Focusing plate spring, 7... Automatic focus device, 8... Wafer mounting table, 9 ...Semiconductor wafer to be inspected, 10...Objective lens, 11...Mirror, 12...7, (,13...
・Lamp, 14... Prism, 15. ．． 16...Lens, 17...Photodiode array (detector)
, 18... Light source, 19... Convex surface, 2o... Step surface, 21... Concave surface, 22... Foreign object, 23... Light source,
24... Lens, 25... Mirror, 26... Motor, 27... Frame, 28... Light beam guide hole for inspection, 29... Hole, 30' photodiode array, 31
... Rotating plate, 32... Hole, 33a-33d... Glass fiber for light beam propagation No. IF+ (0-n (b) Fig. 2 Fig. 3 Fig. 4 (α) 2 (b) No. 5 Figure 6 Figure 7/S

Claims (1)

[Claims] 1.1a) A mounting table and l for mounting the plate-shaped object to be inspected.
bl A light source for irradiating light onto the plate-shaped object and IcI
A defect inspection device comprising a plurality of photodetectors installed under mutually different conditions to detect light reflected from the plate-like object.