JP2003203959A - Sample for observing crystal defects on the surface layer of a semiconductor wafer and its manufacturing method - Google Patents

Abstract

(57) [Summary] [Problem] To provide a sample for observing a crystal defect on a surface layer of a semiconductor wafer and a method for producing the sample, which can determine an accurate position of a crystal defect on the surface layer of the semiconductor wafer when observing a surface layer defect by laser light or the like. Is what you do. A metal film pattern is provided on a mirror-polished semiconductor wafer surface such that a polished surface is exposed in a lattice pattern, and a crystal defect present on the polished surface and observed.
A first mark formed near the crystal defect and observable with an optical microscope or the like, and a second mark between the first mark and the crystal defect that is not observable with an optical microscope or the like near the crystal defect. This is a sample for observing crystal defects on the surface layer of a semiconductor wafer. Also, there are a method for manufacturing this sample and a method for determining the position of a crystal defect using this sample.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer evaluation method, and more particularly to a semiconductor wafer surface layer crystal defect observation sample for forming a crystal defect detection mark and a method for producing the same.

[0002]

2. Description of the Related Art Generally, electronic devices are manufactured using silicon wafers, and crystal defects existing on the surface layer of the mirror-polished surface of the wafer often cause circuit defects after device formation. Therefore, it is extremely important to accurately measure the crystal defects existing in the surface layer and clearly know the behavior thereof in order to construct a defect occurrence prevention measure.

As a method of measuring such surface layer defects, for example, a visible light tomographic apparatus is used, laser light is incident on the mirror-polished surface, and the scattered light is observed from directly above the mirror-polished surface of the wafer. ing. There is also an apparatus that adds a laser marking function to this apparatus and can perform marking at an arbitrary position on the wafer surface while observing crystal defects. This makes it possible to easily form an index for processing the wafer on the wafer surface with a laser so that defects can be observed with a transmission electron microscope or the like.

However, when a mark near a defect is formed by the above-mentioned apparatus, if a mark large enough to be observed with an optical microscope is formed, the silicon layer scattered by laser irradiation adheres to the silicon surface near the laser mark and its scattered light Therefore, simultaneous observation of defects and marks becomes unclear. Further, when a mark having a size that does not bring about such a state is formed, especially when the crystal defect and the mark have a scattering intensity of the same degree, and the size is such that an accurate position can be easily determined after observation, It is difficult to observe the mark with an optical microscope, and it is necessary to observe it with a scanning electron microscope or the like. Moreover, in reality, it is so small that it cannot be clearly observed even with a scanning electron microscope (it can be confirmed only very faintly), so it is difficult to find the laser mark by laser marking alone, and therefore the exact position of the surface layer defect can be determined. Is difficult.

[0005]

Therefore, when a surface defect is evaluated by laser light or the like, a semiconductor wafer surface crystal defect observing sample capable of determining an accurate position of a crystal defect in the semiconductor wafer surface layer and a method for producing this sample are disclosed. Was requested.

The present invention has been made in consideration of the above-mentioned circumstances, and is for observing a crystal defect in a surface layer of a semiconductor wafer, which can determine an accurate position of a crystal defect in the surface layer of the semiconductor wafer when observing the surface layer defect with a laser beam or the like. It is an object to provide a sample and a method for manufacturing the sample.

[0007]

To achieve the above object, according to one aspect of the present invention, a metal film is provided on a mirror-polished semiconductor wafer surface such that the polished surface is exposed in a lattice pattern. A pattern, a crystal defect existing on the polished surface and observed, a first mark formed in the vicinity of the crystal defect and observable by an optical microscope, and a crystal between the first mark and the crystal defect. Provided is a sample for observing a crystal defect in a surface layer of a semiconductor wafer, which has a second mark near the defect which cannot be observed by an optical microscope or the like. Thereby, when observing the surface layer defect with a laser beam or the like, it is possible to determine the accurate position of the crystal defect in the surface layer of the semiconductor wafer.

In a preferred example, the sizes of the first mark and the second mark are such that the crystal defect and the second mark can be observed simultaneously as scattering of laser light, and the crystal defect and the first mark and The size is such that the second mark can be integrally observed. Thus, by observing the first mark as a mark at the same time as the crystal defect without being affected by the second mark, it is possible to accurately determine the position of the crystal defect.

Further, in another preferable example, the first mark is an indentation formed by a Vickers hardness meter,
It is formed apart from the crystal defects by 150 to 200 μm.
As a result, dust is less likely to occur during marking, and
Marking can be done easily.

In another preferred example, the second marks are arranged in a cross shape with four crystal defects as symmetry points. As a result, a crystal defect can be easily and reliably indexed by a scanning electron microscope, and a small sample containing the crystal defect can be cut out.

According to another aspect of the present invention, a metal film pattern is formed on the surface of a mirror-polished semiconductor wafer so that the polishing surface is exposed in a grid pattern, and the metal film pattern is present on any of the grid-like polishing surfaces. Then, a crystal defect to be observed is determined, a first mark observable with an optical microscope or the like is formed in the vicinity of the crystal defect, and an optical microscope or the like is provided between the first mark and the crystal defect in the vicinity of the crystal defect. There is provided a method for producing a sample for observing a crystal defect in a surface layer of a semiconductor wafer, which comprises forming a second mark that cannot be observed. Thereby, the exact position of the crystal defect in the surface layer of the semiconductor wafer can be determined.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a semiconductor wafer surface layer crystal defect observing sample according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram of a sample for observing a crystal defect in a surface layer of a semiconductor wafer according to the present invention.

A sample 1 for observing crystal defects in the surface layer of a semiconductor wafer according to the present invention is a mirror-polished semiconductor wafer 2
And a metal film pattern 4 provided on the surface of the semiconductor wafer 2 so that the polishing surface 3 is exposed in a lattice pattern, crystal defects 5 existing on the polishing surface 3 and observed, and the vicinity of the crystal defect 5. Has a first mark 6 formed on the surface thereof and observable with an optical microscope or the like, and a second mark 7 between the first mark 6 and the crystal defect 5 in the vicinity of the crystal defect 5 which cannot be observed with the optical microscope or the like. ing.

The metal film patterns 4 are made of aluminum, for example, and each side is about 2 mm, and the width of the polishing surface 3 formed between the metal film patterns 4 is 200 μm or more, for example, 500 μm. There is. The width of the polished surface 3 is required to be 200 μm or more in order to prevent the laser light necessary for detecting the crystal defects 5 from being scattered by the metal. The metal vapor deposition pattern 4 serves as an index (rough mark) to facilitate the position determination of crystal defects.

The first mark 6 has crystal defects 5 to 150.
Two of them are formed in the X-axis direction with the crystal defect 5 as a symmetry point, separated by about 200 μm. The first mark 6 can be observed by a simple method such as using an optical microscope, and the laser mark (second mark) can be used by using the first mark 6 as an index.
By observing the mark (1) with a scanning electron microscope, an accurate crystal defect position can be determined from the laser mark. The distance from the crystal defect 5 is set to 150 to 200 μm because the maximum field of view in which the observation result can be captured as image data is limited to about 250 × 500 μm due to the device, and the crystal defect is included. In order to obtain an image in a shape, the distance between the first mark 6 and the crystal defect 5 is 250 μ at maximum.
This is because m. Further, since it is separated from the first mark 6 and the crystal defect 5 by about 150 to 200 μm, even if the mark is formed in a size that can be observed by an optical microscope as an indentation by a Vickers hardness meter, scattered light due to dust etc. Therefore, the observation of crystal defects is not hindered. If the distance between the crystal defect 5 and the first mark 6 is smaller than 150 μm,
Since the scattering intensity of the first mark (Vickers indentation) is usually much larger than that of crystal defects, scattered light interferes with the observation of crystal defects. If the separation distance exceeds 200 μm, it becomes difficult to integrally observe the crystal defect and the first mark and the second mark.

For example, four second marks 7 are formed in a cross shape on the XY axes with the crystal defect 5 being 20 μm away from the crystal defect 5 as a symmetry point. Since the second mark is formed smaller than the first mark 6 that cannot be observed with an optical microscope or the like, the second mark can be marked sufficiently close to the crystal defect 5, and therefore the position where the crystal defect 5 exists is in μm units. It can be determined with accuracy. Further, by forming the second mark 7 so small that it cannot be observed by an optical microscope or the like, the crystal defect 5 and the second mark 7 can be observed simultaneously as laser light scattering without being affected by the first mark 6. it can. Furthermore, the position of the crystal defect 5 can be accurately determined by observing the second mark 7 with a transmission electron microscope.

Next, a method for producing a sample for observing crystal defects on the surface of a semiconductor wafer according to the present invention will be described.

Following the flow chart of the position determining method shown in FIG.
This will be described with reference to FIG.

A mirror-polished silicon wafer 2 is prepared and, as shown in FIG. 3, a metal film pattern is formed using a vacuum vapor deposition device so that the polished surface 3 is exposed in a lattice pattern (S1).

Crystal defects to be observed existing on the lattice-shaped polished surface are determined (S2).

Using a visible light tomography apparatus, crystal defects 5
The position coordinates of are read and recorded using a metal film grid.

This position coordinate is determined by marking a mark with a helten pen and using this as an origin to obtain the XY coordinates of the metal lattice near the crystal defect using a stage. Furthermore, the distance from the corner of this metal lattice is determined by the XY coordinate. Request and record.
Since the mark of the helt pen helps to identify crystal defects,
It is preferable to use the marker, but when the crystal defect can be easily found by utilizing the XY coordinates of the metal lattice in the vicinity, the mark of the pen is not necessarily provided.

The first area that can be observed in the vicinity of the defect with an optical microscope or the like.
The mark 6 is formed (S3).

Using an optical microscope, a neighboring metal lattice is found with reference to the mark of the pen and the position of the crystal defect is estimated by S2, and two crystal defects are formed as symmetrical points in the X-axis direction. The first mark 6 uses a Vickers hardness meter so that it can be easily observed with an optical microscope,
It is preferably formed as an indentation. The Vickers hardness tester is used because dust is less likely to occur during marking.
This is because marking can be done easily, and if cost is not an issue, FIB (Focused Ion B)
There is no problem even if another method such as
Be careful of particle generation).

A second mark 7 that cannot be observed with an optical microscope or the like is formed near the crystal defect (S4).

After confirming that the first mark 6 can be observed by the visible light tomography at the same time as the crystal defect 5 which is determined to be observed, the crystal defect 5 between the first mark 6 and the crystal defect 5 is confirmed.
In the vicinity of, for example, 20 μm at the second position so that the scattering intensity becomes similar to the scattering intensity of the crystal defect 5 by the laser light.
A plurality of marks 7 are formed.

The crystal defect observing sample 1 is manufactured by the above steps.

The position of the crystal defect is determined by observing the second mark and the crystal defect at the same time using an observation device such as a visible light tomography device or a transmission electron microscope (S).
5).

When a visible light tomography apparatus is used for observing crystal defects, a small sample is used without cutting out by a general method. Therefore, a marker of a felt pen is found, and a metal film in the vicinity is found based on this marker. By finding the lattice and further observing simultaneously with the crystal defect 5 by using the first mark 6 and the second mark 7 located at the recorded distance observed from the corner portion of the metal film lattice as a mark, an accurate crystal defect can be obtained. Determine the 5 position.

When a transmission electron microscope is used, the first mark 6 is used as a mark to cut out a small sample according to a general method. Therefore, the cutting is performed using a scanning electron microscope and FIB. With the second mark 7 as a mark, a crystal defect can be easily and surely indexed by a scanning electron microscope, and a small sample including the crystal defect can be cut out. In particular, since the second marks 7 are arranged in a cross shape with the crystal defect as a symmetry point, the sample can be cut into small pieces centering on the crystal defect. Further, the cut out sample is transferred to a transmission electron microscope and observed.
The position of the crystal defect 5 can be easily determined by the mark 7 of.

[0032]

EXAMPLE An Al pattern was formed on a mirror-polished surface of a Czochralski method silicon wafer by a vacuum vapor deposition device so that the silicon-polished surface was exposed in a lattice pattern. For this pattern formation, a wire net made of wire having a diameter of about 400 μm was used as a mask. At this time, one side of the grid was about 2 mm. The width of the exposed mirror-polished surface of the silicon wafer was set to 200 μm or more in order to prevent the laser light necessary for crystal defect detection from being scattered by aluminum.

Next, an arbitrary crystal defect on the silicon surface was detected with a visible light tomography apparatus. Then, the position of the detected crystal defect with respect to the aluminum pattern is determined, a straight line on the wafer surface including the crystal defect is assumed, and 2 on the same straight line separated from the crystal defect by about 150 to 200 μm.
First marks (indentations) were formed at the points with a Vickers hardness tester.

Further, after confirming that the first mark and the crystal defect to be observed can be observed with a visible light tomography at the same time, a scattering intensity of about 20 μm in the vicinity of the crystal defect is obtained by a laser with a scattering intensity similar to that of the crystal defect. Four such laser marks (second marks) were formed in a cross shape centering on the crystal defect.

After the above work, Vickers indentation,
Image data was captured in a form including all laser marks and crystal defects to obtain an image as shown in FIG. Based on this image and the mark on the surface, it was possible to know the position of the crystal defect with considerable accuracy.

Further, when a third party is requested to process a thin piece for observation with a transmission electron microscope, the crystal defect is 1 μm thick.
It became possible to catch it in the flakes with almost 100% probability.

[0037]

According to the semiconductor wafer surface crystal defect observing sample of the present invention, a semiconductor wafer surface crystal capable of determining the exact position of the crystal defect in the semiconductor wafer surface when observing the surface defect with a laser beam or the like. A defect observation sample can be provided.

Further, according to the sample manufacturing method of the present invention, it is possible to manufacture a semiconductor wafer surface crystal defect observing sample capable of determining an accurate position of a crystal defect in the semiconductor wafer surface layer.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a semiconductor wafer surface layer crystal defect observing sample according to the present invention.

FIG. 2 is a flow chart of a method for determining a position of a crystal defect on a surface layer of a semiconductor wafer according to the present invention.

FIG. 3 is a conceptual diagram of a metal pattern used for producing a sample for observing a crystal defect in a surface layer of a semiconductor wafer according to the present invention.

FIG. 4 is a result diagram of an example using the method for determining the position of a crystal defect on the surface layer of a semiconductor wafer according to the present invention.

[Explanation of symbols]

1 Semiconductor wafer surface layer crystal defect observation sample 2 Semiconductor wafer 3 Polished surface 4 metal film pattern 5 Crystal defects 6 first mark 7 Second mark

Claims (4)

[Claims] 1. A mirror-polished semiconductor wafer surface,
A metal film pattern provided so that the polishing surface is exposed in a lattice pattern, a crystal defect existing on the polishing surface and observed, and a first mark formed in the vicinity of the crystal defect and observable with an optical microscope or the like. And the second mark that cannot be observed with an optical microscope in the vicinity of the crystal defect between the first mark and the crystal defect.
A semiconductor wafer surface layer crystal defect observing sample characterized by having the following mark. 2. The first mark is an indentation formed by a Vickers hardness tester, and is 15 from a crystal defect.
The semiconductor wafer surface layer crystal defect observing sample according to claim 1, wherein the sample is formed with a distance of 0 to 200 μm. 3. The semiconductor wafer surface layer crystal defect observing sample according to claim 1, wherein the second marks are arranged in a cross shape with four crystal defects as symmetry points. 4. A metal film pattern is formed on the surface of a mirror-polished semiconductor wafer such that the polished surface is exposed in a lattice shape, and crystal defects existing on any of the lattice-shaped polished surfaces to be observed are determined. Then, a first mark that can be observed with an optical microscope or the like is formed in the vicinity of the crystal defect, and a second mark that cannot be observed with the optical microscope or the like is formed between the first mark and the crystal defect in the vicinity of the crystal defect. A method for producing a sample for observing a crystal defect in a surface layer of a semiconductor wafer, which comprises: