JP2003185591A - Surface inspection device and method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid exerting the effect of the surface color of an inspection object on automatic focusing even in a case performing focusing due to automatic focusing at the time of surface inspection. <P>SOLUTION: The surface inspection device is equipped with an image pickup means 18 for picking up the surface image of a semiconductor substrate plate 30 to be inspected, a first illumination means 11 for emitting illumination light required in the pickup of the surface image, a second illumination means 21 for emitting illumination light separate from that of the first illumination means 11, and automatic focusing means 23, 24 and 25 for performing the focusing of the image pickup means 18 on the basis of the reflected light of the light emitted from the second illumination means 20. A waveform variable means 19 for varying the wavelength of synthetic light applied to the surface of the semiconductor substrate plate by the first and the second illumination means 11 and 21 is provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface inspection apparatus and a surface inspection method used when inspecting and observing the surface of a semiconductor substrate.

[0002]

2. Description of the Related Art Generally, in the manufacturing process of semiconductor devices, it is widely practiced to optically inspect and observe the surface of a wafer substrate. Optical inspection and observation are usually performed by illuminating the surface of a wafer substrate with illumination light, receiving the reflected light with, for example, a CCD (Charge Coupled Device) camera, and imaging the surface of the wafer substrate. That is, the surface condition, the condition of the formed pattern, and the like are determined based on the image of the surface of the wafer substrate that is the imaging result.

Illumination light (hereinafter referred to as "incident light") illuminating the surface of a wafer substrate during such inspection and observation.
In addition, it is necessary to use light with a short wavelength. This is because by using light with a short wavelength, the resolution of imaging is increased and the accuracy of inspection observation is improved. However, although blue light and violet light are known as light having a short wavelength, an oxide film having a thickness that looks blue or purple may be formed on the surface of the wafer substrate during the manufacturing process. . From this,
As the incident light, green light close to blue is often used in order to avoid the influence of the color of the oxide film or the like on the imaging result.

In order to image the surface of the wafer substrate, so-called focusing is necessary. For this focusing, in order to facilitate or optimize the focusing, autofocus, which is a principle of alternately irradiating light of a specific wavelength and measuring a reflected wave thereof, may be used. In this case, the red LED (Light Emit) is used as the light (hereinafter referred to as “autofocus light”) to be irradiated on the surface of the wafer substrate because of its high brightness and easy availability of light emitting elements.
red light is often used. Therefore, when autofocusing is performed, the surface of the wafer substrate is irradiated with violet light, which is a combined light of the incident light (green light close to blue) and the autofocus light (red light). become.

[0005]

However, depending on the manufacturing process of the semiconductor device, an oxide film or the like having a thickness that looks purple may be formed on the surface of the wafer substrate as described above. On the other hand, if violet light is emitted, the color of the combined light and the surface color of the wafer substrate become the same, and as a result, the mechanism for autofocus may not operate normally. That is, conventionally, depending on the surface color of the wafer substrate to be inspected, focus cannot be achieved by autofocus,
It may cause a situation in which proper surface inspection cannot be performed.

Therefore, the present invention makes it possible to avoid the influence of the surface color of the object to be inspected during the autofocusing even when the focus is adjusted by the autofocusing, and to perform an appropriate surface inspection. It is an object of the present invention to provide a surface inspection device and a surface inspection method capable of realizing the above.

[0007]

SUMMARY OF THE INVENTION The present invention is a surface inspection apparatus devised to achieve the above object, and an image pickup means for picking up an image of the surface of a semiconductor substrate to be inspected, and an image picked up by the image pickup means. First illumination means for irradiating the surface of the semiconductor substrate with the illumination light required for, and second illumination means for irradiating the surface of the semiconductor substrate with light different from the first illumination means, Autofocus means for focusing the image pickup means on the basis of the light emitted from the second illuminating means on the surface of the semiconductor substrate, and the first illuminating means and the second illuminating means. It is characterized in that a wavelength varying means for varying the wavelength of the synthetic light with which the illuminating means irradiates the surface of the semiconductor substrate is provided.

Further, the present invention is a surface inspection method devised to achieve the above object. That is, an image pickup means for picking up an image of the surface of a semiconductor substrate to be inspected, a first illuminating means for irradiating the surface of the semiconductor substrate with illumination light necessary for the image pickup by the image pickup means, and the first illumination. Second illumination means for irradiating the surface of the semiconductor substrate with light different from the means, and focus of the imaging means based on the light reflected by the surface of the semiconductor substrate of the light emitted by the second illumination means. A surface inspection method comprising: an autofocus means for performing alignment; and a surface inspection method for inspecting and observing the surface of the semiconductor substrate based on an image pickup result by the image pickup means, wherein the first illumination means and the second It is characterized in that the illuminating means makes variable the wavelength of the combined light with which the surface of the semiconductor substrate is irradiated.

According to the surface inspection apparatus having the above structure and the surface inspection method having the above procedure, the first illuminating means and the second illuminating means irradiate the surface of the semiconductor substrate to be inspected in accordance with the surface color. By varying the wavelength of the combined light, the autofocus means can receive the reflected light from the surface of the semiconductor substrate without being affected by the surface color. That is, for example, even if the surface color of the semiconductor substrate to be inspected is purple, it is possible to avoid the influence of the surface color by changing the wavelength of the synthetic light from a purple equivalent to a dark purple one. Like

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface inspection apparatus and a surface inspection method according to the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is an explanatory diagram showing a schematic configuration example of a surface inspection apparatus according to the present invention. As shown in the figure, the surface inspection apparatus described here is roughly divided into an optical system for surface inspection and an optical system for autofocus.

The optical system for surface inspection is the main lamp 11
, Homogenizer 12, and beam splitters 13a, 1
3b, a mirror 14, an objective lens unit 15, a magnification lens unit 16, a zoom lens unit 17, a camera 18, and a color filter unit 19.

The main lamp 11 illuminates the surface of the wafer substrate 30 to be inspected with illumination light. That is, the main lamp 11 functions as the first lighting means in the present invention.

The homogenizer 12 serves to make the illumination light from the main lamp 11 uniform, and the beam splitters 13a, 13b and the mirror 14 reflect the illumination light from the main lamp 11 and the wafer substrate 30. It changes the optical path of light.

The objective lens unit 15, the magnification lens unit 16, and the zoom lens unit 17 are all for expanding and contracting an image obtained from the wafer substrate 30. In addition,
In the objective lens section 15 and the magnification lens section 16, a plurality of types of objective lenses 15a or magnification lenses 16a are arranged on turret stands 15b and 16b.
The objective lens 15a or the magnification lens 16a can be selected by rotating 16b.

The camera 18 reflects the reflected light of the incident light obtained from the surface of the wafer substrate 30 to be inspected, the objective lens section 15, the mirror 14 and the beam splitters 13a and 13a.
b, the magnification lens unit 16 and the zoom lens unit 17 are sequentially received to receive an image of the surface of the wafer substrate 30. That is, the camera 18 functions as the image pickup means in the present invention. It should be noted that the camera 18 may include an image sensor such as a CCD, and may be configured to capture an image using the image sensor.

The color filter section 19 includes the main lamp 1.
1 is disposed on the optical path between the camera 1 and the camera 18, and is provided with a color filter that transmits light of a specific wavelength. However, the color filter portion 19 is the most characteristic portion in the surface inspection apparatus described in this embodiment, and is configured as described below.

FIG. 2 is an explanatory diagram showing a schematic configuration example of the color filter section according to the first embodiment of the present invention.
As shown in the figure, the color filter unit 19 includes a plurality of types of color filters 19 on a rotatable turret table 19a.
b, 19c ... Each color filter 19b,
Reference numerals 19c ... Allow light of different wavelengths to pass therethrough, and one of them is for making incident light into green light close to blue. Then, the color filter unit 19 is configured such that only one of the color filters 19b, 19c ... Is interposed on the optical path between the main lamp 11 and the camera 18 by rotating the turret table 19a. There is. That is, the color filter unit 19 is
The incident light can be converted into a specific wavelength and the conversion wavelength can be changed to any one of a plurality of preset types.

Therefore, it can be said that the color filter section 19 functions as the wavelength varying means in the present invention. Further, the turret table 19a that constitutes the color filter section 19 is a drive source (not shown) for driving the turret table 19a.
Together with this, it functions as the filter variable mechanism in the present invention. The turret table 19a does not necessarily have to be automatically operated by using a drive source, and may be manually rotated by an operator of the surface inspection apparatus, for example.

On the other hand, in FIG. 1, an optical system for autofocus includes an autofocus LED (hereinafter, simply referred to as "LED") 21, a beam splitter 22a,
22b, an autofocus source sensor (hereinafter simply referred to as "source sensor") 23, an autofocus focus sensor (hereinafter simply referred to as "focus sensor")
24) and a normal sensor for autofocus (hereinafter, simply referred to as “normal sensor”) 25. The beam splitters 13a and 13b and the mirror 14 also serve as an optical system for surface inspection.

The LED 21 irradiates the surface of the wafer substrate 30 with light different from that of the main lamp 11. That is, the LED 21 functions as the second illumination means in the present invention. The light emitted by the LED 21 is autofocus light used for focusing when the camera 18 images the surface of the wafer substrate 30. Therefore, for reasons such as high brightness and easy availability of the light emitting element, it is assumed that the LED 21 emits red light, for example.

The beam splitters 22a and 22b, like the beam splitters 13a and 13b and the mirror 14, change the optical path of the autofocus light.

Source sensor 23, focus sensor 24
The normal sensor 25 and the normal sensor 25 are both
This is for realizing the focusing of the camera 18 by receiving the reflected light of the autofocus light obtained from the surface of 0. That is, each of these sensors 23, 24, 2
Reference numeral 5 functions as an autofocus unit in the present invention in combination with a drive source (not shown) for focusing the camera 18. However, each sensor 2
Since the autofocus itself using 3, 24 and 25 is not different from the conventional one, its explanation is omitted here.

Next, an example of the processing operation in the surface inspection apparatus configured as described above, that is, the surface inspection method in this embodiment will be described.

When inspecting and observing the surface of the wafer substrate 30 using the surface inspection apparatus having the above-described structure, in the surface inspection optical system, the main lamp 11 is attached to the surface of the wafer substrate 30 to be inspected. Irradiate with illumination light. At this time, the color filter unit 19 transmits light to any one of the plurality of types of color filters 19b, 19c ..., However, in the normal state (default state), the incident light becomes green light close to blue. It is assumed that you have selected one. Then, when the incident light is reflected on the surface of the wafer substrate 30, the reflected light is reflected by the camera 18 through the objective lens unit 15, the mirror 14, the beam splitters 13a and 13b, the magnification lens unit 16 and the zoom lens unit 17 in this order. Is received, and the surface of the wafer substrate 30 is imaged. As a result, it becomes possible to inspect and observe the surface of the wafer substrate 30 based on the imaging result.

Further, in the optical system for autofocus,
Before the camera 18 captures an image of the surface of the wafer substrate 30, the LED 21 irradiates the surface of the wafer substrate 30 with red light. Then, the reflected light of the red light on the surface of the wafer substrate 30 is reflected by the source sensor 23 and the focus sensor 2.
4 and the normal sensor 25 receive light, the camera 18 is focused on the basis of the light reception result. Therefore, when the focus is adjusted by the autofocus, the main lamp 11 is not attached to the surface of the wafer substrate 30.
The violet light, which is a combined light of the green light close to blue from the LED and the red light from the LED 21, is emitted.

By the way, the wafer substrate 30 to be inspected
In some cases, an oxide film or the like having a thickness that looks purple may be formed on the surface thereof. In such a case, when the wafer substrate 30 is irradiated with violet light as the combined light, the color of the combined light and the surface color of the wafer substrate 30 become the same, which may hinder the autofocus. You need to avoid this.

Whether or not the surface color of the wafer substrate 30 is purple can be determined, for example, from the manufacturing process of the wafer substrate 30 (what kind of film structure, etc.). Alternatively, the operator of the surface inspection device may make the judgment visually. Alternatively, the detection level of the reflected light by the source sensor 23, the focus sensor 24, or the normal sensor 25 is compared with a preset threshold value, and if the detection level does not reach the threshold value, the surface color of the wafer substrate 30 is purple. It is possible to judge that there is.

In this way, when it is determined that the surface color of the wafer substrate 30 is purple, the color filters 19b, 19c ... Are selected in the color filter section 19 in order to avoid the trouble of autofocusing. change. That is, with respect to the wafer substrate 30, the irradiation light from the main lamp 11 is supplied to the color filters 19b and 19b.
The light other than the default state is transmitted through c ... so that the incident light becomes light other than green light close to blue. As a result, the combined light with which the surface of the wafer substrate 30 is irradiated becomes light other than violet light, and its wavelength is different from the wavelength of the surface color of the wafer substrate 30.

As described above, according to the surface inspection apparatus and the surface inspection method described in the present embodiment, the color filter section 19 has a plurality of types of color filters 19b, depending on the surface color of the wafer substrate 30 to be inspected. By selectively interposing any one of 19c on the optical path, the wavelength of the combined light with respect to the surface of the wafer substrate 30 can be changed, so that the source sensor 23 and the focus sensor are not affected by the surface color. 24 and normal sensor 25
Will be able to receive the reflected light. That is, regardless of the surface color of the wafer substrate 30 to be inspected, proper autofocus can be realized.

In this embodiment, the color filter unit 1
9 arranges a plurality of types of color filters 19b, 19c ... On the turret table 19a and rotates the turret table 19a, so that any one color filter 19b,
Although the case where 19c ... Is selected has been described as an example, a configuration described below can be considered as a configuration for changing the wavelength of the incident light with respect to the surface of the wafer substrate 30. In other words, the wavelength of incident light can be varied by combining one or more of a plurality of types of color filters and selectively interposing them in the optical path, and by overlapping a plurality of color filters having different wavelengths in some cases. You may

[Second Embodiment] Next, a second embodiment of the present invention will be described.
The embodiment will be described. However, here, only the differences from the case of the above-described first embodiment will be described. In the surface inspection apparatus described in the present embodiment, the color filter unit in the optical system for surface inspection and the LED in the optical system for autofocus are
This is different from the case of the first embodiment (see FIG. 1).

The color filter section does not have a plurality of types of color filters as in the case of the first embodiment and a mechanism for selecting one of them, but has only one color filter. This color filter is
As in the conventional case, the incident light is green light that is close to blue.

The LED is the most characteristic part of the surface inspection apparatus described in this embodiment, and is constructed as described below. FIG. 3 is an explanatory diagram showing a schematic configuration example of an LED according to the second embodiment of the present invention. As shown in the figure, the surface inspection apparatus of the present embodiment includes a plurality of LEDs 21a, 21b, ... Which emit light of different wavelengths as LEDs for irradiating autofocus light. Then, while being controlled by a control circuit (not shown), any one of the plurality of LEDs 21a, 21b ... Or a combination of two or more thereof can be selectively emitted. That is, these LEDs 21a,
21b ... Together with the control circuit thereof function as the second illuminating means and the wavelength varying means in the present invention. It is assumed that the LEDs 21a, 21b ... Are arranged side by side at substantially the same position. This is because if they are arranged in parallel, only the wavelength of the autofocus light can be changed without changing the light emitting position.

Next, an example of processing operation in the surface inspection apparatus configured as described above, that is, the surface inspection method in this embodiment will be described. Even when the surface inspection apparatus having the above-described configuration is used to inspect and observe the surface of the wafer substrate 30, in the normal state (default state),
Similar to the case of the first embodiment, each LED 21a, 2a
Red light is emitted as autofocus light from any one or each of 1b.

However, when it is determined that the surface color of the wafer substrate 30 to be inspected is purple, an LED that emits light is used in order to avoid a problem in autofocus.
21a, 21b ... Or the combination thereof is changed. That is, for the wafer substrate 30, for example, in addition to the LED that emits red light, L that emits orange light is used.
The ED also emits light. As a result, the combined light with which the surface of the wafer substrate 30 is irradiated becomes dark violet light, and its wavelength is different from the wavelength of the surface color of the wafer substrate 30.

As described above, according to the surface inspection apparatus and the surface inspection method described in the present embodiment, the plurality of LEDs 21 are provided depending on the surface color of the wafer substrate 30 to be inspected.
The wavelength of the combined light with respect to the surface of the wafer substrate 30 can be varied by selectively emitting any one of a, 21b, ... Or two or more thereof, so that the same as in the case of the first embodiment. In addition, proper autofocus can be realized.

The specific modes described in the first and second embodiments described above are merely specific examples of the present invention, and the present invention is limited to the specific examples. Not to mention it. In particular, the surface color of the wafer substrate and the color of the synthetic light (wavelength)
It is needless to say that the above may be other modes.

However, as described in the first and second embodiments, it is sufficient that the wavelength of the combined light after changing is close to the wavelength in the normal time. Only when the wavelength of the combined light of the incident light and the autofocus light and the wavelength of the surface color of the wafer substrate are the same, a slight difference in the wavelength of the combined light is used to achieve proper autofocus. This is because it can be realized.

[0040]

As described above, according to the surface inspecting apparatus and the surface inspecting method of the present invention, the wavelength of the synthetic light with which the surface of the semiconductor substrate is irradiated is made variable, thereby the substrate surface color is changed. The proper auto focus can be realized without being affected by. Therefore, it becomes possible to easily and appropriately focus a semiconductor substrate having a surface color that could not be conventionally autofocused, and as a result, the surface inspection can be optimized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration example of a surface inspection apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a schematic configuration example of a main part according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a schematic configuration example of a main part according to a second embodiment of the present invention.

[Explanation of symbols]

11 ... Main lamp, 18 ... Camera, 19 ... Color filter part, 19a ... Turret stand, 19b, 19c ... Color filter, 21, 21a, 21b ... LED, 23 ... Source sensor, 24 ... Focus sensor, 25 ... Source sensor

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2G051 AA51 AB01 AB07 BA01 BA08                       BB15 CA04 CB01                 2G059 AA05 BB16 EE02 GG02 GG03                       GG09 JJ02 JJ22 JJ30 KK04                       LL01 NN10                 4M106 AA01 CA38 DB12 DB13 DB15                       DB16 DB20

Claims (6)

[Claims] 1. An image pickup means for picking up an image of the surface of a semiconductor substrate to be inspected, a first illuminating means for irradiating the surface of the semiconductor substrate with illumination light required for the image pickup by the image pickup means, Second illuminating means for irradiating the surface of the semiconductor substrate with light different from the first illuminating means, and the imaging based on the light radiated by the second illuminating means on the surface of the semiconductor substrate. A surface inspection apparatus comprising: an auto-focusing means for focusing the means; a wavelength for varying the wavelength of the combined light with which the first illuminating means and the second illuminating means irradiate the surface of the semiconductor substrate. A surface inspecting device comprising variable means. 2. The wavelength variable means includes a plurality of types of color filters for transmitting light of a specific wavelength, and one of the plurality of types of color filters is provided between the first illumination means and the surface of the semiconductor substrate. 2. The surface inspection apparatus according to claim 1, further comprising a variable filter mechanism selectively intervening between the two. 3. The second illuminating means is composed of a plurality of light emitting elements which emit light of wavelengths different from each other, and the wavelength varying means is any one or two of the plurality of light emitting elements. The surface inspection apparatus according to claim 1, wherein the above is combined to selectively emit light. 4. An image pickup means for picking up an image of the surface of a semiconductor substrate to be inspected, a first illuminating means for irradiating the surface of the semiconductor substrate with illumination light required for image pickup by the image pickup means, Second illuminating means for irradiating the surface of the semiconductor substrate with light different from the first illuminating means, and the imaging based on the light radiated by the second illuminating means on the surface of the semiconductor substrate. A surface inspecting device comprising an autofocusing means for focusing the means, and a surface inspecting method for inspecting and observing the surface of the semiconductor substrate based on an image pickup result by the image pickup means, wherein the first illuminating means and A surface inspection method, wherein the wavelength of the synthetic light applied to the surface of the semiconductor substrate by the second illuminating means is variable. 5. The wavelength of the combined light is varied by selectively interposing any of a plurality of types of color filters that transmit light of a specific wavelength between the first illuminating means and the surface of the semiconductor substrate. 5. The surface inspection method according to claim 4, wherein 6. When the second illuminating means is composed of a plurality of light emitting elements which emit light of different wavelengths, any one of the plurality of light emitting elements or a combination of two or more of the plurality of light emitting elements is selectively emitted. The surface inspection method according to claim 4, wherein the wavelength of the combined light is made variable by performing the above.