JPH07151698A - Apparatus and method for observing crystal defect - Google Patents

Abstract

PURPOSE:To enable the observation of a defect only which is very near the surface of a semiconductor crystal efficiently even when a device is already formed by irradiating a laser luminous flux with a wavelength large in absorption coefficient passing only near a flat surface of a semiconductor crystal. CONSTITUTION:When a wafer 1 which is held on an XY stage 7 and has a device formed is observed, first, a part desired to be observed is found out by a visible light moving the XY stage 7 and the wafer 1 is so positioned that the part is located within a visible range of a microscope 5. Then, a laser light with a wavelength large in absorption coefficient passing only near the surface of the wafer 1 by a laser irradiation means 3 to irradiate the surface of the wafer l at the part within the visible range of the microscope 5. A scattered image data is obtained with a camera 9 through the microscope 5 from a defect near the surface of the wafer 1 generated eventually. Here, the wafer 1 can be moved finely with the XY stage 7. The operation as mentioned above is repeated to find and observe the parts to be observed sequentially.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for observing defects existing in the vicinity of the surface of a semiconductor crystal used in a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, as a method of observing an internal defect of a semiconductor wafer, a laser beam is irradiated toward a wafer surface, and thereby scattered light generated by the internal defect is generated on the surface side of the wafer.
A method of observing from the back surface side or the cleavage surface side perpendicular to these surfaces is known. Then, in these methods, laser light having a wavelength having a high transmittance with respect to a semiconductor wafer is used.

[0003]

However, according to the conventional technique as described above, only defects existing in the vicinity of the semiconductor surface, which have a very important influence on the presence or absence of defects in forming a semiconductor device, are limited. There is a problem that it is inconvenient to observe efficiently.

Further, when semiconductor devices are already formed on the surface of a wafer, a series of delicate operations in which the portions to be observed are sequentially searched, positioned with respect to the observation means, and these portions are sequentially observed. There is also an inconvenient situation in which there is currently no means for efficiently performing.

In view of the above-mentioned problems of the prior art, an object of the present invention is to observe a crystal defect in which only a defect existing in the immediate vicinity of a semiconductor crystal surface can be efficiently observed even if a device is already formed. To provide a device.

[0006]

In order to achieve this object, the crystal defect observing apparatus of the present invention has a wavelength at which the semiconductor has a large absorption coefficient so that only a portion near the surface of the semiconductor crystal is transmitted toward the flat surface. Laser irradiation means for irradiating the laser light flux, a microscope for observing the semiconductor crystal surface with visible light while receiving and forming an image by the scattered light generated from crystal defects existing in the vicinity of the surface by the laser light flux, and the semiconductor crystal And a moving means for moving in a plane substantially perpendicular to the optical axis of the microscope.

When the semiconductor crystal is silicon crystal, the wavelength is preferably in the range of 400 to 900 nm.

[0008]

According to the present invention, since the irradiated laser light is transmitted only in the range in the vicinity of the semiconductor crystal, it is possible to observe the surface of the semiconductor crystal with visible light as if the scattered image of the defect in that range. Similarly, it is observed two-dimensionally.
That is, only the defects near the surface that have an important influence on device formation are extracted and efficiently observed without the complexity of specifying the depth position from the surface of the defect.

Further, according to the apparatus of the present invention, the microscope is used not only for observing scattered light from a defect but also for observing the surface with visible light. Therefore, the observation target portion is searched for and positioned with a simple structure. Defects are observed efficiently.

[0010]

1 and 2 are a front view and a side view, respectively, showing a crystal defect observing apparatus according to an embodiment of the present invention. As shown in these drawings, this apparatus is provided with a laser irradiation means 3 for converging and irradiating a laser beam of a wavelength having a large absorption coefficient, which is transmitted only to the vicinity of the surface of the semiconductor wafer 1, and irradiates the laser beam. The microscope 5 for observing the surface of the wafer 1 with visible light and receiving the scattered light generated from the defects existing in the vicinity of the surface of the wafer 1 by moving the wafer 1 in a plane perpendicular to the optical axis of the microscope 5 for positioning. An XY stage 7 and a television camera 9 for photoelectrically converting an image obtained by the microscope 5 to obtain image data.

In this structure, when the wafer 1 held on the XY stage 7 and having the device formed thereon is observed,
First, the portion to be observed is searched for with visible light while moving the XY stage, and the wafer 1 is positioned so that the portion is located within the visible range of the microscope 5.

Next, the laser irradiation means 3 focuses the laser light of the above-mentioned wavelength and irradiates it on the surface of the wafer 1 in the visible portion of the microscope 5. Then, the scattered image data from the defect near the surface of the wafer 1 generated thereby is obtained by the camera 9 through the microscope 5. At that time, the wafer 1 can be finely moved by the XY stage 7. When the observation of the portion is completed, the above operation is repeated, and the observation target portion can be sequentially searched and observed.

[0013]

As described above, according to the present invention, the scattered image of defects existing in the range near the semiconductor crystal is two-dimensionally obtained as if the surface of the semiconductor crystal was observed with visible light. Can be observed. That is, it is possible to efficiently perform observation by extracting only defects near the surface, which have an important influence on device formation, without the complexity of specifying the depth position from the surface of the defect. Moreover, since the microscope is used for observing scattered light from defects and for observing the surface with visible light at the same time, it is possible to efficiently locate defects by locating and locating the observation target portion with a simple configuration. it can.

[Brief description of drawings]

FIG. 1 is a front view showing a crystal defect observing apparatus according to an embodiment of the present invention.

FIG. 2 is a side view of FIG.

[Explanation of symbols]

1: semiconductor wafer, 3: laser irradiation means, 5: microscope,
7: XY stage, 9: TV camera.

Claims (4)

[Claims] 1. A laser irradiating means for irradiating a flat surface of a semiconductor crystal with a laser beam of a wavelength having a large absorption coefficient in the semiconductor, which transmits only in the vicinity of the surface, and the laser beam to the vicinity of the surface. A microscope for observing the semiconductor crystal surface with visible light while receiving and forming an image with scattered light generated from existing crystal defects, and a moving means for moving the semiconductor crystal in a plane substantially perpendicular to the optical axis of the microscope. An apparatus for observing crystal defects, which comprises: 2. The crystal defect observing apparatus according to claim 1, further comprising means for photoelectrically converting an image obtained by the microscope to obtain image data. 3. A laser beam having a wavelength having a large absorption coefficient in the semiconductor, which transmits only the vicinity of the surface toward a flat surface of the semiconductor crystal, is irradiated, and the laser beam causes a crystal defect existing in the vicinity of the surface to disappear. A method for observing a crystal defect, which comprises observing by receiving scattered light generated. 4. The crystal defect observing method according to claim 3, wherein the semiconductor crystal is silicon crystal, and the wavelength is in the range of 400 to 900 nm.