JP2000252333A - Method for evaluating trace organic matter on surface of silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for evaluating trace organic matter on surface of silicon wafer by which whether the quantity of organic aggregates existing on the surface of a silicon wafer kept in a case is large or small can be evaluated by counting the number of the aggregates. SOLUTION: A silicon wafer W is set to a prescribed inspecting position. Then the surface of the wafer is perpendicularly irradiated with laser light and the total number of particles including organic aggregates (a) existing on the surface is counted. The surface of the wafer W is obliquely irradiated with laser light and the number of the particles excluding the aggregates (a) is counted. Then the number of the organic aggregates (a) is calculated by subtracting the number of the particles from the first counted number of particles. Therefore, whether the quantity of the organic aggregates (a) existing on the surface of the wafer W is large or small can be evaluated easily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating a trace amount of organic substances on the surface of a silicon wafer, and more particularly, to a method for measuring the number of organic aggregates generated on the surface of a silicon wafer stored in a wafer case for a long time. The present invention relates to a method for evaluating trace organic substances.

[0002]

2. Description of the Related Art A silicon wafer shipped to a device factory after polishing and cleaning is stored in a wafer case,
Transported and stored. By the way, when this wafer case is composed of a case body and a core made of polypropylene and a lid made of polycarbonate, for example, if stored for a long period of one month or more, although the cause is not clear, the wafer surface In some cases, a small amount of organic aggregates in the shape of a perfect circle having a diameter of about 10 μm and a thickness of about 0.1 μm may be generated.

[0003] Such organic aggregates have a great effect on the product yield and reliability of the device as the device becomes finer and the chip area increases. This is because the poor appearance and shape of the wafer surface is the largest factor in lowering the product yield. As a result, if the amount of the organic matter aggregate is large, the product becomes defective, and the product yield and the like are reduced. Therefore, it is necessary to detect the organic matter aggregates and discharge the silicon wafer, which is determined to have a large amount of the organic matter aggregates, out of the device manufacturing line. For example, re-cleaning is performed.

[0004]

By the way, in the conventional inspection of the wafer surface performed before the device process, the inspection of the particles may be carried out by using a low-angle incident particle detector. However, since the organic matter aggregate has a height as low as about 0.1 μm, there is a problem that it is difficult to detect the organic matter aggregate by a particle detection apparatus having a low incident angle.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method for evaluating a trace amount of organic matter on the surface of a silicon wafer by measuring the number of organic matter aggregates present on the surface of the silicon wafer and evaluating the amount of the organic matter aggregates. To provide
That is the purpose. Another object of the present invention is to evaluate a situation (for example, a plastic case) in which a silicon wafer is stored.

[0006]

According to a first aspect of the present invention, a surface of a silicon wafer having no COP is irradiated with laser light from two directions, a vertical direction and an inclined direction, and the surface is obtained by the vertical incidence. From the number of particles containing organic aggregates on the wafer surface, by subtracting the number of particles not containing organic aggregates obtained by the oblique incidence, the number of organic aggregates on the silicon wafer surface to be measured and evaluated. This is a method for evaluating trace organic matter.
The silicon wafer to be evaluated is not limited to the cause of the generation of the organic aggregate on the wafer surface. For example, a wafer case having a part made of polypropylene and a part made of polycarbonate is exemplified. Further, the particle detection device that irradiates the surface of the silicon wafer with laser light in the vertical direction is not particularly limited. For example, “SS620” manufactured by Tencor Corporation
0 "," SP-1 "," LS-6 "manufactured by Hitachi, Ltd.
310 "and ADE" WIS-CR80 ".

[0007] Further, there is no particular limitation on a particle detection device that irradiates a laser beam from an inclined direction. For example, "SS6420" manufactured by Tencor Corporation is mentioned. The incident angle of the laser beam is 20 to 80 degrees, especially 20 to 4 degrees.
0 degrees is preferred. If the angle is less than 20 degrees, minute particles cannot be accurately detected. On the other hand, when the temperature exceeds 80 degrees, the target organic aggregate is measured.

[0008]

According to the present invention, first, a silicon wafer having no COP on its surface is set at a predetermined inspection position.
After that, for example, the wafer surface is irradiated with a laser beam from a vertical direction, and the total number of particles such as fine dust containing organic aggregates present on the wafer surface is measured. Next, the wafer surface is irradiated with a laser beam from an inclined direction. Thereby, the number of particles excluding the organic aggregates present on the wafer surface is measured. Then, by subtracting the number of particles not containing the organic matter aggregate from the former number of particles containing the organic matter aggregate, the number of the organic matter aggregates can be obtained by a simple calculation. Moreover, from the calculation result, it is possible to evaluate the abundance state of the organic matter aggregate whose height is as low as about 0.1 μm and which is difficult to detect by the conventional method.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram during detection of particles by normal incidence in a method for evaluating a trace amount of organic matter on a silicon wafer surface according to one embodiment of the present invention. FIG. 2 is an explanatory diagram during particle detection by oblique incidence in the method for evaluating a trace amount of organic matter on a silicon wafer surface according to one embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes an inspection apparatus 10 for a trace organic substance on a silicon wafer surface to which a method for evaluating a trace organic substance on a silicon wafer surface according to an embodiment of the present invention is applied (hereinafter, simply referred to as a trace organic substance inspection apparatus 10). In some cases). This trace organic matter inspection apparatus 10 is capable of measuring a trace amount of organic matter aggregate a present on the surface of the silicon wafer W.
(A diameter d = 10 μm, a thickness t = about 0.1 μm), a first particle detection device 11 for inspecting fine dust and the like by irradiating a laser beam from a vertical direction, and a particle present on the surface of the silicon wafer W. A second particle detection device 12 is provided for inspecting the wafer surface by irradiating other fine dust and the like except the organic matter aggregates to the wafer surface at an inclination angle of 20 degrees. Note that the second particle detection device 12 is installed downstream of the first particle detection device 11.

The silicon wafer W used here
Is obtained, for example, by subjecting a silicon single crystal rod pulled up by the CZ method to block cutting, wafer cutting, chamfering, mechanical chemical polishing, and final cleaning by RCA cleaning,
Then, with a polypropylene case body and core,
It is a silicon wafer that has been stored in a wafer case with a lid made of polycarbonate and shipped, and has been stored in the warehouse of the device factory for about one month. The silicon wafer W to be evaluated has a mirror-finished wafer surface. The first particle detecting device 11 is specifically “SS6200” manufactured by Tencor Corporation.
In other words, the apparatus irradiates the surface of the silicon wafer W with laser light in the vertical direction, and detects the number of particles having a minimum of 0.10 μm existing on the surface.

This apparatus is composed of a laser light source 13 arranged orthogonally to the wafer surface, and two channels (for a bright field and a dark field) on the left and right sides in a vertical plane around the light source 13. And a photomultiplier 14 arranged radially. The laser light irradiated at 90 ° from the upper light source 13 toward the wafer surface hits particles such as organic aggregates a and fine dust adhering to the mirror-finished wafer surface and is irregularly reflected. The reflected light spreads radially as shown by the arrow in FIG. This is captured by an arbitrary photomultiplier 14, whereby the total number of particles including the organic aggregates a present on the surface of the silicon wafer W is detected.

A second particle detecting device 1 shown in FIG.
2 is, specifically, “SS642” manufactured by Tencor Corporation.
0 ". That is, the surface of the silicon wafer W is irradiated with laser light from an obliquely upward direction, and particles such as fine dust having a minimum of 0.15 μm excluding the organic aggregates a on the wafer surface are counted. The device configuration includes a light source 15 arranged on one upper side of the silicon wafer W to irradiate the laser beam upward to the silicon wafer W in parallel, and a mirror 16 for bending the laser beam downward to the silicon wafer W side. , A beam expander 17, and a lens 1 for condensing a laser beam passing therethrough
8 and arranged on the other side above the silicon wafer W,
A large photomultiplier 19 that captures laser light reflected from the wafer surface.

The laser beam emitted from the light source 15 is bent at an angle of 20 degrees with respect to the surface of the wafer W by the mirror 16, and thereafter, the beam expander 17 and the lens 18
Is applied to the wafer surface. Of these, the particles reflected by the two channels (for bright field and dark field) of the photomultiplier 19 capture the reflected light reflected by the particles, thereby detecting the particles. However,
Here, it is impossible to detect the organic substance aggregate a as described above. This is because the thickness t of the organic matter aggregate a is
Since the particles are as thin as 0.1 μm, if the light is emitted from the oblique direction, the aggregates a
This is because it is not possible to obtain good reflected light capable of capturing the light.

Here, the scanning technique based on SS6420 will be described. The focus mechanism moves the target silicon wafer W up and down with the wafer surface placed on the scan plane. The silicon wafer W has a wavelength of 488 at a constant speed.
traveling in the nm telecentric scanning laser beam. The laser beam is focused to project a 75 μm diameter circle when traversing the substrate surface at a 20 ° angle. The scanning beam traverses a straight path on the silicon wafer W back and forth, and reliably samples the entire silicon wafer W.

The laser beam is applied to the L on the silicon wafer W
When illuminating a PD (foreign matter), light is scattered in all directions from the point of incidence. A part of the scattered light is collected and guided to a low-noise photomultiplier to be amplified. Low noise photomultiplier tube PMT
Is digitized by a high-speed analog-to-digital converter. Data acquisition electronics periodically sample this digital converter,
A raster image of the surface of the silicon wafer W is generated. The raster image is then analyzed by a pipeline processor and a dedicated general purpose computer to create, display, and manipulate surface measurement data.

Next, a method for evaluating a trace organic substance on the surface of a silicon wafer using the trace organic substance inspection apparatus 10 will be described. As shown in FIG. 1, the silicon wafer W is
Are arranged in a horizontal state on the detection stage of the particle detection device 11. After that, the organic agglomerates a, fine dust and the like existing on the surface of the silicon wafer W are inspected. That is, in the particle inspection of the wafer surface,
Laser light is emitted from the light source 13 of the first particle detection device 11 toward the wafer surface at 90 °, and the reflected light is captured by the photomultiplier 14, thereby containing the organic aggregates a attached to the wafer surface. Count particles. As described above, in the first particle detection device 11, the laser light is incident on the wafer surface from the vertical direction. Therefore, as shown in the partial enlarged view of FIG. 1, the reflected light from the organic aggregate a having a low height can be captured well by using the photomultiplier 14.

Next, the silicon wafer W is transferred to the detection stage of the first particle device 12. Here, the second particle detector 12 irradiates the wafer surface with laser light from the light source 15 in an oblique direction. Then, the reflected light is transferred to the photomultiplier 19.
Captured by As a result, particles such as fine dust present on the wafer surface are detected. However, in the second particle detection device 12, since the incident angle of the laser beam is small, as shown in the partial enlarged view of FIG. The reflection angle of the reflected light is small. Therefore, the photomultiplier 19 cannot satisfactorily capture the reflected light. As a result, the particles that can be detected by the second particle detection device 12 are fine dust and the like excluding the organic aggregates a.

Thereafter, the number of particles of the second particle detection device 12 is subtracted from the number of particles obtained by the first particle detection device 11 in the control section (not shown) of the trace organic substance inspection device 10. The number of organic agglomerates a present on the surface of the silicon wafer W is measured by the simple calculation described above, and the amount of the organic agglomerates a on the silicon wafer W as a specimen is evaluated based on the obtained result. I do. As described above, when measuring the number of the organic aggregates a on the wafer surface, the surface of the wafer is irradiated with laser light from the vertical direction and the inclined direction, and thereafter, the simple calculation is performed to thereby obtain the organic aggregates a.
Was determined, so that this organic matter aggregate a
It is possible to easily evaluate a state with many or few states.

[0020]

According to the present invention, the surface of the wafer is irradiated with laser light in the vertical and inclined directions to measure the organic substance aggregates present on the wafer surface. It is possible to easily evaluate whether or not the agglomerate is large on the wafer surface. In particular, it is possible to easily evaluate the cleanliness of the wafer surface stored in the resin case. Therefore, the cleanliness of the resin case itself can be evaluated. In addition, evaluation such as cleaning of a wafer can be performed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram during detection of particles by normal incidence in a method for evaluating a trace amount of organic substances on a silicon wafer surface according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram during particle detection by oblique incidence in the method for evaluating a trace amount of organic matter on a silicon wafer surface according to one embodiment of the present invention.

[Explanation of symbols]

 10 Inspection device for trace organic matter on silicon wafer surface, 11 First particle detection device, 12 Second particle detection device, W Silicon wafer, a Organic matter aggregate.

Continued on the front page F term (reference) 2G051 AA51 AB07 BA10 BB01 CA02 CA07 CB01 DA06 EA08 4M106 AA01 BA05 CA41 DB08 DB11 DB21 DB30

Claims (1)

[Claims] 1. A surface of a silicon wafer having no COP is irradiated with laser light from two directions, a vertical direction and an inclined direction, and the number of particles including organic aggregates on the wafer surface obtained by the perpendicular incidence is calculated as follows. A method for evaluating a trace amount of organic matter on the surface of a silicon wafer by measuring and evaluating the number of organic matter aggregates by subtracting the number of particles containing no organic matter aggregates obtained by the oblique incidence.