JPH08220004A - Apparatus and method for member inspection - Google Patents

Abstract

PURPOSE: To make it possible to discriminate a foreign matter present on the surface of a member such as a semiconductor substrate and a defect of the member present in the vicinity of the surface and to improve the quality of the semiconductor substrate or the like. CONSTITUTION: The inspecting apparatus scans the light transmitted through a member such as a semiconductor substrate and has at least a light splitting detector 50 for detecting the change in phase of the light caused by the defect of the member. A detecting circuit 62 for a signal changing state detects the appearing state of the phase change of the detected light. A defect-site discriminating circuit 63 discriminates the defect in the member and the foreign matter attached on the surface of the member based on the appearing state of the phase change of the light, which is detected with the detecting circuit 62 for the signal changing state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection technique for a member such as a semiconductor substrate, and more particularly to a Czochralski (CZ: Czoc).
The present invention relates to a member inspection apparatus and a member inspection method suitable for highly accurately detecting oxygen precipitates which are minute crystal defects existing near the surface of a silicon member grown by the hralski) method.

[0002]

2. Description of the Related Art Highly integrated circuit devices are formed on and near the surface of a semiconductor substrate, and the characteristics of the device are strongly influenced by the conditions near the surface of the semiconductor substrate. In particular, it is considered that if crystal defects exist near the surface of the semiconductor substrate, the device characteristics such as the breakdown voltage of the gate oxide film and the current leakage of the capacitor are deteriorated. If the correlation between the crystal defect density near this surface, especially the oxygen precipitate density in the CZ silicon substrate containing a large amount of interstitial oxygen and the device yield becomes clear, what kind of silicon crystal should be used, or It should be clear that any silicon substrate should not be used as it is prone to failure. Therefore, there is a demand for a technique for evaluating the density of oxygen precipitates near the surface of a silicon semiconductor substrate.

Oxygen precipitates precipitated in the CZ silicon crystal by the heat treatment have a diameter of about 0.3 μm at the maximum. If there is a larger size near the surface, it can be safely considered that it is other than oxygen precipitates. Therefore, it is necessary to discriminate whether it is an oxygen precipitate or a foreign substance adhering to the surface of the substrate when the size is smaller than this.

As a technique for detecting oxygen precipitates which are fine crystal defects existing in the vicinity of the surface of a silicon semiconductor crystal substrate, the surface is often etched and then observed with an optical microscope. That is, since the etching rate varies depending on the presence or absence of defects, irregularities are formed on the substrate surface, and it becomes possible to confirm the location of the defects by an optical microscope. However, this inspection technology requires destructive inspection, and
There are drawbacks such as the need for chemical treatment. As an alternative to such an etching test, one that detects the side scattered light of the light that passes through the semiconductor crystal is known, and is disclosed in "Journal of Crystal Growth" magazine. Volume 108 (19
91), pp. 482-490. This technique does not etch but requires breaking the substrate and is not non-destructive. This semiconductor inspection technique that detects scattered light is suitable for detecting defects inside the crystal.

However, with this detection technique using side scattered light, it is difficult to measure defects near the surface of the substrate, and it is not suitable for detecting defects near the surface. In addition, there is a conventional technique for detecting a crystal defect existing near the surface by detecting the reflected and scattered light from the semiconductor crystal. In this technique as well, when the reflected and scattered light from the crystal defect is detected, it is detected. Is it due to foreign matter adhering to the surface?
Alternatively, it cannot be easily distinguished whether it is due to a crystal defect. As a result, if the yield of a semiconductor substrate is evaluated using such data, the evaluation will include an error.

[0006]

The problem to be solved is that the conventional technique cannot easily distinguish a foreign substance attached to the surface of a semiconductor substrate or the like from a defect existing in the vicinity of the surface. is there. The object of the present invention is to solve the problems of these conventional techniques, improve the detection accuracy of crystal defects of semiconductors, etc., make the evaluation of yield for semiconductor substrates highly reliable, and improve the quality of members such as semiconductor substrates. An object of the present invention is to provide a member inspection apparatus and a member inspection method that enable the inspection.

[0007]

In order to achieve the above object, the member inspection apparatus according to the present invention comprises: (1) scanning of light transmitted through a member (inside of a semiconductor) to change the phase of light due to a defect in the semiconductor. And a signal change state detection circuit for detecting the appearance of a phase change of the detected light, which is an inspection apparatus having at least a means (light splitting detector 50) for detecting A discriminating means (defect portion discriminating circuit 63) for discriminating between a defect in the semiconductor substrate 41 and a foreign substance adhering to the surface of the semiconductor substrate 41 on the basis of the appearance of the phase change of the light detected in 62 is provided. And (2) In the member inspection apparatus according to (1) above, the light that has been scanned and transmitted through the member (semiconductor substrate 41) at adjacent positions is received, and the signal intensity corresponding to the intensity of the received light is received. First and second light receiving circuits (optical splitting detector 5 having detection surfaces 51 and 52) for outputting
0) and a comparison circuit (difference electronic circuit 61) that outputs the difference between the signal intensities output from the light split detector 50 in the scanning order.
And the signal change state detection circuit 62 detects the appearance of the phase change of the light based on the appearance of the change of the signal intensity difference output from the difference electronic circuit 61 in the scanning order. Further, (3) a member (for example, a crystalline sample such as graphite, which may be a semiconductor substrate 4 in this case).
1 is given as an example) and light of a wavelength that transmits (emission light 1
2) generating light source 11, an optical system (lenses 21, 22) for condensing the light from the light source 11, a scanning mechanism 60 for holding and scanning the semiconductor substrate 41 at the condensing position, and the semiconductor substrate 41. The light transmitted through is divided into multiple areas and received,
At least a light split detector 50 that outputs a signal corresponding to each received light intensity and a difference electronic circuit 61 that outputs a difference between the respective signals output from the light split detector 50 in the scanning order are provided. An inspection device for detecting a defect of a semiconductor substrate 41 based on a change in a differential signal output from a circuit 61 in a scanning order, the signal being for detecting how a change in a differential signal output from a differential electronic circuit 61 appears. Change state detection circuit 62 and this signal change state detection circuit 62
It is characterized in that a defect part discriminating circuit 63 for discriminating between a defect of the semiconductor substrate 41 and a foreign substance adhering to the surface of the semiconductor substrate 41 is provided on the basis of the appearance of the change of the differential signal detected in step. And the inspection method of the member of the present invention,
(4) An inspection method for scanning the light passing through a member (semiconductor substrate 41), detecting a change in the phase of light due to a defect in the semiconductor substrate 41, and determining the presence or absence of a defect in the semiconductor substrate 41. The appearance of the phase change of the light that has scanned and transmitted through the substrate 41 is detected, and based on the detected appearance of the phase change of the light, the semiconductor substrate 41 detects defects in the member and foreign matter attached to the surface of the member. It is characterized by making a determination. (5) In the member inspection method according to (4), the light beams that have been scanned and transmitted through the members at adjacent positions are received, and signal intensities corresponding to the intensities of the received lights are output. The difference between the signal intensities is output in the scanning order, and the appearance of the phase change of the light is detected based on the appearance of the change in the signal intensity difference output in the scanning order. Further, (6) light having a wavelength that passes through the member (semiconductor substrate 41) is generated, this light is condensed, the semiconductor substrate 41 is held and scanned at this condensing position, and the light transmitted through the semiconductor substrate 41 Is divided into a plurality of areas to receive light, the signals corresponding to the respective received light intensities are output in the scanning order, the difference between the output signals is output, and the defect of the semiconductor substrate 41 is detected based on the change in the scanning order of the difference signal. Of the difference signal output in the scanning order, the defect of the semiconductor substrate 41 and the surface of the semiconductor substrate 41 are detected based on the detected change signal of the difference signal. The feature is that it is distinguished from the adhered foreign matter.

[0008]

In the present invention, for example, the difference in the direction of the detection signal of the oxygen precipitates in the semiconductor substrate and the direction of the detection signal of the foreign matter on the surface of the semiconductor substrate is taken into consideration. A crystal defect existing in the vicinity and a foreign substance attached to the surface of the semiconductor substrate are discriminated. Since the refractive index of the silicon crystal matrix is 3.57 and the refractive index of the oxygen precipitates is about 1.47, there is a difference in the progress of the wavefront as compared with the absence of the oxygen precipitates. That is, the phase of light changes, and the wavefront of light in oxygen precipitates advances faster than in silicon crystals.If the semiconductor substrate containing oxygen precipitates is moved from the left with respect to the laser light, Then, the waveform of the signal strength at this time is as shown in FIG.
After increasing, it decreases and then starts increasing. This makes it possible to detect oxygen precipitates inside the semiconductor substrate. Further, when foreign matter is attached to the surface of the semiconductor substrate, the refractive index of the foreign matter on the surface is generally larger than that of air, so the speed of the wavefront of the emitted light in the foreign matter on the surface becomes slower than in air. . That is, a phase delay occurs. Therefore, when the surface foreign matter is irradiated with the emitted light, the direction in which the emitted light bends is opposite to that of the case of oxygen precipitates in the silicon crystal. Therefore, when the semiconductor substrate having the surface foreign matter attached thereto is moved from the left, it decreases and then increases as shown in FIG. 5, and then starts to decrease. In this way, for example, oxygen precipitates in the semiconductor substrate and foreign substances existing on the surface of the semiconductor substrate generate different output signals. Therefore, by comparing the output signals, they can be distinguished from each other.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a configuration according to the present invention of a member inspection apparatus according to the present invention. The present embodiment exemplifies a semiconductor substrate inspection apparatus. In the figure, 11 is a light source for generating light having a wavelength that passes through the inside of the semiconductor substrate 41 of silicon crystal, and 21 and 22 are light from the light source 11 (output A lens as an optical system that collects the incident light 12),
Reference numeral 60 denotes a scanning mechanism for holding and scanning the semiconductor substrate 41 at a condensing position, and 50, which receives the light transmitted through the semiconductor substrate 41 by dividing the light into a plurality of areas and outputs a signal corresponding to each received light intensity. , 61 is a light splitting detector as first and second light receiving means, 61 is a difference electronic circuit as a comparing means of the present invention for outputting the difference between the respective signals output from the light splitting detector 50 in the scanning order, and 62 is a difference A signal change state detection circuit for detecting a change state of the differential signal output from the electronic circuit 61 in the scanning order, 63 is based on the detection result of the signal change state detection circuit 62, and the change of the differential signal exists near the surface of the semiconductor substrate. It is a defective portion discrimination circuit that discriminates whether it is due to a crystal defect or a foreign substance attached to the surface of the semiconductor substrate.

With such a structure and the following operation, in the semiconductor substrate inspection apparatus of this embodiment, the crystal defects existing near the surface of the semiconductor substrate 41 as the inspection sample and the foreign substances attached to the surface of the semiconductor substrate are detected. Can be easily discriminated. That is, from the light source 11, light having a wavelength that can be transmitted through the semiconductor substrate 41 of silicon crystal (emitted light 1
2) is emitted. The emitted light 12 is collimated by the lens 21 and narrowed down on the semiconductor substrate 41 by the lens 22. The transmitted light from the semiconductor substrate 41 is detected by the light split detector 50 including the detection surfaces 51 and 52. The difference electronic circuit 61 amplifies each signal from the light split detector 50 and then takes the difference between the two. The respective amplification factors are set so that the difference between the two becomes substantially zero when light is not irradiated on the oxygen precipitates or the foreign substances on the surface.

In this state, the scanning mechanism 60
When scanning is performed so as to pass through oxygen precipitates contained in the semiconductor substrate 41 or pass through foreign substances on the surface of the semiconductor substrate 41, signals as shown in FIGS. 3 and 5 described later are obtained. When scanning the center of the defect, the difference signal becomes almost zero. The signal change state detection circuit 62 and the defective portion determination circuit 63 are electronic circuits including a computer, and the signal change state detection circuit 62 has an image storage device, as shown in FIGS. A waveform is stored, and the stored waveform is analyzed by software to detect the change state of the signal. Then, the defective portion determination circuit 63
Based on the change state of this signal, it is determined whether the detected defect is due to a foreign substance on the surface or due to an oxygen precipitate. The determination result is displayed as information such as an image on a display device (not shown).

The main purpose of the semiconductor substrate inspection apparatus of this embodiment is to distinguish between foreign substances on the surface of the semiconductor substrate and oxygen precipitates existing in the vicinity of the surface. It is naturally possible to detect an object. At that time, a confocal microscope optical system is added in the embodiment shown in FIG. 1 in order to know how deep the focal position of the irradiation light is from the substrate surface. Since the position of the semiconductor substrate surface can be specified by this confocal microscope optical system, it is possible to know how much the beam waist of the narrowed light enters the inside of the semiconductor with reference to the position. In the present embodiment, the reflected light from the surface of the semiconductor substrate 41 returns to the lens 22, is reflected by the semitransparent mirror 31, and is focused on the pinhole 32 by the lens 23.
The light transmitted through the pinhole 32 is detected by the detector 56. In the confocal optical system, the amount of detected light becomes maximum when the beam waist of the narrowed irradiation light has a reflecting surface. That is, when the surface of the semiconductor substrate 41 is at the focal position of the lens 22, the output of the detector 56 becomes maximum. By setting this position as the surface, the depth of the beam waist can be estimated. If the signal of the detector 56 is used as an image signal, a high resolution confocal image can be obtained.

As described in the prior art, the oxygen precipitates precipitated in the CZ silicon crystal by the heat treatment have a diameter of about 0.3 μm at the maximum, and have a larger size in the vicinity of the surface. If something exists,
There is no doubt that this is something other than oxygen precipitates. Therefore, in the semiconductor inspection apparatus of the present embodiment, a smaller one is discriminated as an oxygen precipitate or a foreign substance. Details of such a determination operation will be described below with reference to FIG.
~ It demonstrates using FIG. First, with reference to FIGS. 2 and 3, let us consider a case where a foreign substance exists near the surface of the semiconductor substrate.

FIG. 2 is an explanatory view showing a first specific example of a defect detection state of a semiconductor substrate by the semiconductor inspection apparatus in FIG. 1, and FIG. 3 is a graph showing an example of a signal waveform in the defect detection state. . In this example, the oxygen precipitate 42 exists near the surface of the semiconductor substrate 41 made of silicon crystal. The laser light (emitted light 12) is finely focused on the surface of the semiconductor substrate 41. Then, the transmitted light is detected by the detection surface 5.
It is detected by the light splitting detector 50 composed of 1 and 52, and its output is input to the difference electronic circuit 61 composed of an operational amplifier or the like to take the difference. When the surface of the semiconductor substrate 41 is clean and oxygen precipitates are not present in the irradiation region of the irradiation light, that is, when the wavefront of the irradiation light is not disturbed, the difference electronic circuit 61
The signal strength from is set to zero.

As shown in FIG. 2, when the oxygen precipitate 42 in the semiconductor substrate 41 is irradiated with the irradiation light, the refractive index of the silicon crystal matrix is 3.57, and the refractive index of the oxygen precipitate 42 is reduced. Since the rate is about 1.47, there is a difference in the progress of the wavefront as compared with the place where the oxygen precipitate 42 does not exist. That is, the phase of light changes, and the wavefront of light advances earlier in the oxygen precipitate 42 than in the silicon crystal. Here, consider a case where the semiconductor substrate 41 containing the oxygen precipitate 42 is moved from the left with respect to the laser light (emitted light 12). The waveform of the signal strength at this time is shown in FIG.
When the irradiation light irradiates the place where there is no oxygen precipitate 42, the output signal 6 from the differential electronic circuit 61
4 is zero.

When the oxygen precipitate 42 enters the left side of the emitted light 12, the traveling direction of the emitted light 12 is bent to the right, and the light is strongly incident on the detection surface 52 of the light splitting detector 50. Since the difference output from the difference electronic circuit 61 is obtained by subtracting the intensity of the detection surface 51 from the intensity of the detection surface 52 of the light split detector 50, it increases and then decreases as shown in FIG. It will be. When the semiconductor substrate 41 is further moved and comes to be on the right side of the emitted light 12, the light is strongly incident on the detection surface 51. Therefore, as shown in FIG. 3, the differential signal further decreases and then increases. Will turn to.

Next, with reference to FIGS. 4 and 5, let us consider a case where a foreign substance is present on the surface of the semiconductor substrate. 4 is shown in FIG.
5 is an explanatory diagram showing a second specific example of a defect detection state of the semiconductor substrate by the semiconductor inspection apparatus in FIG. 5, and FIG. 5 is a graph showing an example of a signal waveform in the defect detection state. As shown in FIG. 4, foreign matter (surface foreign matter 4
3) is attached. Since the refractive index of the surface foreign matter 43 is generally larger than that of air, the velocity of the wavefront of the emitted light 12 in the surface foreign matter 43 is slower than that in the air. That is, a phase delay occurs. For this reason, the surface foreign matter 43 is reflected by the emitted light 1
When 2 is irradiated, the bending direction of the emitted light 12 is opposite to that of the case of oxygen precipitates in the silicon crystal. Therefore, when the semiconductor substrate 41 having the surface foreign matter 43 attached thereto is moved from the left, the output waveform as shown in FIG. 5 is obtained. As described above, since the oxygen precipitates in the silicon crystal and the foreign matter existing on the surface of the silicon crystal substrate generate different output signals, the states of the output signals can be compared to easily determine the respective signals. it can.

As described above with reference to FIGS. 1 to 5, in the semiconductor substrate inspection apparatus of the present embodiment, the semiconductor substrate exists inside the semiconductor based on the difference between the refractive index of the minute defect and the refractive index of the semiconductor crystal matrix. In addition to detecting small defects, the order of increase and decrease of the detected signal intensity is analyzed to distinguish between crystal defects existing near the surface of the semiconductor substrate and foreign particles existing in the air adhering to the semiconductor substrate surface. be able to.
Generally, a semiconductor substrate in a semiconductor manufacturing process passes through various heat treatment processes. This heat treatment step changes the size or distribution of oxygen precipitates inside the semiconductor substrate, and the number density, but in the semiconductor substrate inspection apparatus of the present embodiment, the change of oxygen precipitates particularly near the surface of the substrate is You can know it by excluding its existence. When detecting the change, a dummy substrate can be flown in the same semiconductor manufacturing process, extracted after each process, and inspected by the semiconductor substrate inspection apparatus of this embodiment.

Further, since the inspection by the semiconductor substrate inspection apparatus of this embodiment is non-destructive, it is possible to monitor the change of the defect at the same place by returning to the process after inspecting one dummy substrate. is there. Further, in the semiconductor device in the process of manufacturing, the semiconductor substrate inspection apparatus of this embodiment inspects a portion having a small number of patterns, so that the occurrence of defects can be detected at an early stage. Further, by removing the defective product at the stage when it is discovered, it is possible to prevent waste of the subsequent steps. In this way, the quality control of the semiconductor manufacturing process can be improved.

The present invention is not limited to the embodiment described with reference to FIGS. 1 to 5, and various modifications can be made without departing from the scope of the invention. For example, in this embodiment, a confocal microscope optical system is added in order to know the depth of oxygen precipitates inside the semiconductor substrate from the substrate surface. It may not have an optical system. Further, the light splitting detector of the present embodiment shows an example of splitting into two, but it is also possible to use a detector of splitting into two or more. Further, although the semiconductor substrate inspection is described as an example in the present embodiment, the present invention can be applied to other members that transmit light, such as liquid crystal.

[0021]

According to the present invention, a foreign substance existing on the surface of a member such as a semiconductor substrate and a defect existing near the surface of the member can be easily distinguished from each other, and the detection accuracy of crystal defects such as a semiconductor can be improved. It is possible to improve, for example, the yield evaluation for a semiconductor substrate with high reliability, and by using the member substrate inspection apparatus of the present invention in the semiconductor manufacturing process, the quality control of the semiconductor manufacturing process can be improved and the quality of the semiconductor substrate can be improved. It is possible to improve.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a configuration of a semiconductor substrate inspection apparatus of the present invention according to the present invention.

FIG. 2 is an explanatory diagram showing a first specific example of a defect detection state of a semiconductor substrate by the semiconductor inspection device in FIG.

3 is a graph showing an example of a signal waveform in a defect detection state of the semiconductor substrate in FIG.

FIG. 4 is an explanatory diagram showing a second specific example of a defect detection state of a semiconductor substrate by the semiconductor inspection device in FIG.

5 is a graph showing an example of signal waveforms in a defect detection state of the semiconductor substrate in FIG.

[Explanation of symbols]

11: light source, 12: emitted light, 21, 22, 23: lens, 31: semi-transparent mirror, 32: pinhole, 41: semiconductor substrate, 42: oxygen precipitate, 43: surface foreign matter, 50: light splitting detector, 51: 52: detection surface, 56: detector, 60: scanning mechanism, 61: differential electronic circuit, 62: signal change state detection circuit, 63: defective portion discrimination circuit, 64: output signal

Claims (6)

[Claims] 1. An inspection apparatus having at least means for scanning light passing through a member to detect a change in the phase of the light due to a defect in the member, wherein the appearance of the phase change of the detected light is detected. And a determining means for determining a defect in the member and a foreign substance adhering to the surface of the member based on how the phase change of the light detected by the detecting means appears. Inspection device 2. The member inspection apparatus according to claim 1, wherein the light which has been scanned and transmitted through the members at adjacent positions is received, and a signal intensity corresponding to the intensity of the received light is output. , Second light receiving means and comparing means for outputting the difference in the signal intensities outputted from the first and second light receiving means in the scanning order, and the detecting means is outputted from the comparing means in the scanning order. An inspection apparatus for a member, which detects the appearance of the phase change of the light based on the appearance of the change in the signal intensity difference. 3. A light source that emits light of a wavelength that passes through a member, an optical system that collects light from the light source, a scanning mechanism that holds and scans the member at the light collecting position, and the member. An optical division detector that receives the transmitted light by dividing it into a plurality of areas and outputs a signal corresponding to each received light intensity, and a differential electron that outputs the difference between the signals output from the optical division detector in the scanning order. And a circuit for detecting a defect of the member based on a change of a difference signal output from the difference electronic circuit in a scanning order, the change of the difference signal output from the difference electronic circuit in a scanning order. A detecting means for detecting the appearance of the defect and a determining means for determining the defect of the member and the foreign matter adhering to the surface of the member based on the appearance of the change of the differential signal detected by the detecting means. Characterized by Inspection device for parts. 4. An inspection method for determining the presence or absence of a defect in the member by scanning light passing through the member, detecting a change in the phase of the light due to a defect in the member, and scanning the member. The appearance of the phase change of the transmitted light is detected,
A method for inspecting a member, wherein a defect in the member and a foreign substance adhering to the surface of the member are discriminated based on how the detected phase change of the light appears. 5. The method for inspecting a member according to claim 4, wherein the light beams that have been scanned and transmitted through the members at adjacent positions are received, and a signal intensity corresponding to the intensity of each received light is output. , A difference in the signal intensities is output in the scanning order, and the appearance of the phase change of the light is detected based on the appearance of the change in the signal intensity difference output in the scanning order. Inspection methods. 6. A light having a wavelength that passes through a member is generated, the light is condensed, and the member is held and scanned at the condensed position.
The light transmitted through the member is divided into a plurality of areas to receive light, signals corresponding to the respective received light intensities are output in the scanning order, the difference between the output signals is output, and the difference signal is output based on the change in the scanning order. An inspection method for detecting a defect of a member, wherein the appearance of the change of the differential signal output in the scanning order is detected, and the defect of the member and the member are detected based on the appearance of the change of the detected differential signal. A method for inspecting a member, which is characterized in that it is distinguished from a foreign matter attached to the surface of the.