JPH01195346A - Infrared scattering tomography device - Google Patents

Abstract

PURPOSE:To easily analyze the dislocation state of the crystal of a sample by calculating and displaying the difference between the two scattered images obtd. by projecting IR laser beams from two directions to one sample so that the scattered image stressed of the dependency on oritation is obtd. CONSTITUTION:The IR laser beam IR is perpendicularly projected to the end face Ta of the square sample Ta and the entire area is scanned in a direction Y. The image data of the scattered images is stored in an image memory device 14. A rotary sample stage 1 and an IR vidicon 3 are then rotated 90 deg. in a direction Q and the image data of the scattered images in said direction is stored in the memory 14. The difference between the two sets of the image data in the device 14 is computed by the command of an arithmetic command circuit 16 and the image by the data after the computation is displayed on a CRT 13. The image stressed of the scattered image by a scattering body having the dependency on the orientation is thereby obtd. and the analysis of the dislocation state of the crystal in the sample is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an apparatus for observing crystal defects present in a sample such as a semi-dedicated wafer using a narrowly focused infrared laser beam.

<Prior Art> Generally, an apparatus for observing crystal defects in a sample using an infrared laser beam emits an infrared laser beam IR narrowly focused by a condenser lens 7 on the side of the sample T, as shown in FIG. 6, for example. Irradiate the inside of the sample T from the direction,
An infrared microscope 4 is used to form an image of the light scattered by crystal defects interposed within the sample T on the light receiving surface of an infrared vidicon 3 installed above the sample T, and the signal output from the infrared vidicon 3 is framed. The image data is captured and stored in the memory 11, and further stored in the image processing device 12. Then, after the observation is completed, image processing is performed and the contents are output to the image display device CRT 13 via the frame memory 11.
It is configured to display an image of scattered light on Tl 3.

(Osaka Moriya: [Observation of Crystal Defects by Laser Tomography J Applied Physics 55 (1986) 542) <Problems to be Solved by the Invention> By the way, within the sample T, there are, for example, precipitates having a rectangular parallelepiped shape, etc. There are scatterers with orientation dependence, and these scatterers are often adsorbed on the slip planes of crystals. Therefore, by observing a scattering image focusing on this orientation-dependent scatterer, it is possible to know the dislocation state of the crystal. However, in the actual sample T, there are many cases in which the above-mentioned direction-dependent scatterers and scatterers without direction dependence, such as spherical precipitates, coexist, and the conventional apparatus However, it is very difficult to distinguish between the scattering images caused by these two different types of scatterers.

Means for Solving the Problems> The present invention has been made to solve the above problems, and its configuration is shown in FIGS. 1 and 2 corresponding to the embodiments.
To explain with reference to the drawings, the present invention includes one end surface of the sample T along a plane perpendicular to the horizontal plane as a reference plane Ta,
An incident direction changing means (rotating sample table) 1 capable of changing the angular relationship between the reference plane Ta and the infrared laser beam IR traveling direction in the direction along the horizontal plane, and before and after driving the incident direction changing means 1. , a storage means (image storage device) 14 for individually storing image data of the obtained ILK disordered images, and a calculation means (image difference calculation device) for calculating the difference between the two image data stored in the storage means 14. 15, and display means (CRT) 13 for displaying the image data after the calculation.

<Operation> A scattering image due to an azimuth-dependent scattering image appears or disappears when the direction of incidence of the infrared laser beam IR on the sample T differs. Therefore, for example, a third
Appears in diagram (A), as shown in diagrams (A) and CB),
If there is a scattering image that disappears in figure [B], that is, a scattering image within the region r in figure (A), the difference image between the two,
FIG. 3(C) is an image in which the above-mentioned disappearing scattering image, that is, the scattering image due to the direction-dependent scatterer is emphasized.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

An infrared microscope 4 and an infrared vidicon 3 supported by a rotating support stand 2 are arranged vertically above the rotating sample stage 1, and a sample T such as a semiconductor wafer is placed on the rotating sample stage 1. .

The rotating sample stage 1 has a built-in stepping motor (not shown) and is configured to rotate the sample T by an angle θ according to a drive signal supplied from the driver 5.

The same applies to the rotation support table 2, which is configured to rotate the infrared vidicon 3 in the same direction as the rotation of the sample T by a stepping motor or the like rotated by the same drive signal from the driver 5. ing.

A YAGI laser device 6 is disposed on the side of the sample T, and its oscillated infrared laser beam IR is reflected by a prism 8, passes through an infrared condenser lens 7, and enters the sample T. It is configured like this. Further, on the oscillation side of the infrared laser beam IR, a known scanning device (not shown) is provided that can scan the beam IR along a horizontal plane in the Y direction in predetermined steps.

The infrared vidicon 3 is a known one, and is configured to output a signal according to the amount of light by receiving scattered light from the sample T via an infrared microscope 4, and the output signal is as follows. , captured and stored in the frame memory 11, and further stored in the image processing device 12.

The image processing device 12 performs image processing on the accumulated data each time scanning of the infrared laser beam IR over the entire area of the sample T is completed, that is, each time one observation is completed, and the image data after the image processing is processed. It is configured to sequentially output to the image storage device 1-4.

The image storage device 14 has a function of individually storing image data sequentially output by the image processing device 12.

The image difference calculation device 15 takes in two image data from the image storage device 14 in accordance with a command signal output from the calculation command circuit 16 in response to a command from the keyboard 17, calculates the difference between the two image data, and also performs calculation. The subsequent data is sent to the image display device CRT' via the frame memory 11.
13. Here, the image data difference calculated by the image difference calculation device 15 means that, if each image based on two image data is, for example, FIG. 3 (A) and (B), the image shown in FIG. It means erasing the image.

Next, the observation procedure will be explained with reference to FIG. 2, which shows the area around the sample T viewed from above.

First, a sample T cut into a square is placed on the rotating sample stage 1 so that the infrared laser beam IR is perpendicularly incident on one end surface Ta of the sample T. In this state, by scanning the infrared laser beam IR over the entire sample T in the Y direction, image data of the obtained scattering image is captured and stored in the image storage device 14.

Next, the rotating sample stage 1 and the infrared vidicon 3 are rotated 90 degrees in the direction of the arrow in the figure, and the image data of the scattering image obtained in the same manner as the previous observation is stored in the image storage device 14.
The data is stored separately from the image data from the previous observation.

That is, in the image storage device 14, image data of two scattered images obtained by the infrared laser beam IR that is perpendicularly incident on the surface Ta or Tb of the sample T is stored separately. Then, by supplying a command signal from the calculation command circuit 16 to the image difference calculation device 15 by operating the keyboard 17, the difference between the two image data in the image storage device 14 is calculated, and an image is created by the image data after the calculation. will be automatically displayed on the CRT13. Here, if each image based on two image data stored in the image storage device 14 is, for example, shown in FIG. 3 (A) and (B), then C
On RT13, the image shown in FIG. 3(C) is displayed, which is obtained by erasing the image in FIG. 3(C) from the image in FIG. 3(A).

In the above embodiment, the case where the rotation angle of the sample T was set to 90' was explained, but any other arbitrary angle may be set. In this case, for example, as shown in FIG. The laser beam IR is refracted by the surface Ta of the sample T, and its traveling direction within the sample T changes, and the scanning step width d
The positional relationship with the sampling line of the electron beam of the infrared vidicon 3 also changes, but the rotation angle of the sample T, that is, the angle of incidence of the infrared laser beam IR on the sample T, ψ
The above deviation can be eliminated by calculating the refraction angle φ' from φ' and calibrating the sampling direction of the electron beam of the infrared vidicon 3 and its scanning step width based on the calculated value φ'. Here, n is the refractive index of the sample T with respect to the infrared laser beam reflecting device.

Furthermore, in this example, the case where the rotation angle of the sample T is set in two different ways has been explained, but two or more different angles may be set. Each image based on three or more image data is displayed on, for example, a monitor CRT (not shown), and an operator selects two preferable images from the group of three or more images,
If the difference is displayed, it is possible to save time and effort such as redoing the observation, and it is possible to efficiently obtain the target observation image.

Further, in this embodiment, the sample T and the infrared vidicon 3 are configured to be rotated, but the present invention is not limited to this, and both may be fixed, for example, as shown in FIG. Lens 57 and rotating mirror 58
By moving the laser beam reflection device 56 consisting of , the direction of incidence of the infrared laser beam IR on the sample T may be changed.

Furthermore, in this embodiment, the image processing device 12, the image storage device 14. Although the image difference calculation device 15 and image difference calculation device 15 are separately provided, the present invention is not limited to this, and each of these functions may be incorporated as software in one microcomputer or the like.

<Effects of the Invention> As explained above, according to the present invention, an infrared laser beam is irradiated into one sample from two different directions, two types of observations are performed, and the difference between two scattering images obtained by each is calculated. Since the configuration is configured to calculate and display the scattering image after the calculation, the displayed image is a scattering image that appears in one of the two observations and disappears in the other observation, that is, a scattering image that is azimuth-dependent. The resulting image emphasizes the scattering image caused by the scatterer, so that it is possible to obtain an image that facilitates analysis of the dislocation state of crystals within the sample.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a diagram for explaining the observation procedure, FIG. 3 is an explanatory diagram of the operation, and FIGS. FIG. 6 is a block diagram showing the configuration of a conventional infrared scattering tomography apparatus. 1...Rotating sample stage 13...CRT 14...Image storage device 15...Image difference calculation device IR...Infrared laser beam T...Sample patent applicant Shimadzu Corporation Representative Patent attorney Nishi 1) New construction 1 diagram 6

Claims (1)

[Claims] By irradiating a sample disposed along a predetermined plane with an infrared laser beam traveling parallel to the plane, a light detection means receives scattered light generated by a scatterer interposed within the sample; In a device for observing the scattering image, one end face of the sample along a plane perpendicular to the plane is used as a reference plane, and the angular relationship between the reference plane and the infrared laser beam traveling direction in the direction along the plane is changed. an incident direction changing means capable of changing the incident direction; a storage means for separately storing image data of scattered images obtained before and after driving the incident direction changing means; and two image data stored in the storage means. 1. An infrared scattering tomography apparatus comprising: a calculation means for calculating the difference; and a display means for displaying image data after the calculation.