JP2023009513A - Inspection device, inspection system, and inspection method - Google Patents

Abstract

To accurately inspect an object during a heat treatment.SOLUTION: An inspection device includes: an acoustic emission sensor to be arranged inside a heat treatment furnace; a storage for storing the acoustic emission sensor so as to allow the peripheral temperature of the sensor to be different from the in-furnace temperature of the heat treatment furnace; and a waveguide rod which penetrates the storage and where the acoustic emission sensor is attached to one end and the other end is in contact with an inspection object in the heat treatment furnace. A determination section processes the output of the acoustic emission sensor of the inspection device, thereby to determine the state of the inspection object.SELECTED DRAWING: Figure 1

Description

The present invention relates to an inspection apparatus, an inspection system and an inspection method.

2. Description of the Related Art Conventionally, there has been known a method of inspecting the state of an object by detecting elastic waves emitted by acoustic emission (hereinafter referred to as AE) with an AE sensor. For example, Japanese Unexamined Patent Application Publication No. 2014-22594 (Patent Document 1) discloses that "film crack detection provided in a film forming apparatus that has a processing container that houses an object to be processed and forms a thin film on the surface of the object to be processed. In the film crack detection apparatus to be operated, probe means provided in the processing container, elastic wave detection means attached to an end of the probe means for detecting an elastic wave, and detection results of the elastic wave detection means. and determination means for determining whether or not maintenance of the processing container is necessary based on ".

JP 2014-22594 A

In Patent Document 1, an elastic wave detecting means outside the processing container detects an elastic wave generated when a film deposited on a probe means provided inside the processing container breaks. In this manner, the configuration in which the probe means is pulled out to the outside of the processing container may cause the temperature inside the processing container to become unstable. Furthermore, since the distance to the elastic wave detection means is long, high inspection accuracy cannot be expected.
Moreover, although Patent Document 1 can indicate the timing of maintenance of the film forming apparatus, it cannot detect an abnormality in the object to be processed during the heat treatment.
Heat treatment is used to remove stress after film formation on a semiconductor wafer and to bake ceramics, and abnormalities in the workpiece such as cracks may occur during the heat treatment. However, since the process temperature of the heat treatment exceeds the heat-resistant temperature of the AE sensor, it has been an important issue how to accurately inspect the workpiece for abnormalities during the heat treatment. Note that heat treatment includes both a heating process and a cooling process after heating, and since abnormalities in the workpiece can occur in both the heating process and the cooling process, inspection is possible until the workpiece is removed from the heat treatment furnace. is required.
Accordingly, an object of the present invention is to accurately inspect an object during heat treatment.

In order to achieve the above object, one representative inspection apparatus and inspection system of the present invention includes an acoustic emission sensor arranged inside a heat treatment furnace, and a and a waveguide rod penetrating through the hangar, having one end attached to the acoustic emission sensor, and the other end being in contact with an object to be inspected in the heat treatment furnace. characterized by
In one of the typical inspection methods of the present invention, an inspection device equipped with an acoustic emission sensor attached inside the hangar to one end of a waveguide rod penetrating the hangar is placed in the heat treatment furnace to be inspected. a step of outputting the elastic wave to a determination unit; and a step in which the determination unit determines an abnormality of the inspection object based on the elastic wave. .

According to the present invention, an object can be accurately inspected during heat treatment. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

1 is an explanatory diagram of a device manufacturing system using inspection according to an embodiment; FIG. FIG. 4 is an explanatory diagram of a semiconductor manufacturing process using an inspection method according to an embodiment; Explanatory drawing of the test|inspection during heat processing. Explanatory drawing (1) about the structural example of an inspection apparatus. Explanatory drawing (part 2) about the structural example of an inspection apparatus. FIG. 4 is an explanatory diagram of signal processing of an AE sensor; Explanatory drawing about utilization of the generation position of a crack. FIG. 3 is an explanatory diagram of inspection in units of semiconductor wafers;

An embodiment will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of a device manufacturing system using inspection according to an embodiment. As shown in FIG. 1, the heat treatment apparatus 10 is an apparatus that performs heat treatment on a workpiece 12 placed inside a heat treatment furnace 11 . The inspection device 30 is arranged inside the heat treatment furnace 11 and inspects the state of the workpiece 12 in real time during the heat treatment. That is, in this embodiment, the processing object 12 is the inspection object.

The inspection device 30 has a sensor unit 32 stored in a hangar 31 , a waveguide rod 33 , a sound absorbing member 34 and a temperature control mechanism 35 .

The hangar 31 stores the sensor unit 32 and makes the temperature around the sensor and the temperature inside the heat treatment furnace 11 different.
The sensor unit 32 is a unit that includes an acoustic emission (AE) sensor that detects elastic waves and a temperature sensor.
The waveguide rod 33 penetrates the housing 31 , has the sensor unit 32 attached to one end, and contacts the workpiece 12 in the heat treatment furnace 11 at the other end.

The sound absorbing member 34 is filled in the through hole through which the waveguide rod 33 penetrates the storage 31 to block the through hole. A material having acoustic impedance sufficiently smaller than that of the waveguide rod 33 is used for the material of the sound absorbing member 34 . Therefore, it is possible to prevent gas from flowing from the hangar 31 to the heat treatment furnace 11, stabilize the temperature of the heat treatment furnace 11, and prevent the sensor unit 32 from being exposed to a high temperature exceeding the heat resistance temperature. Also, the sound absorbing member 34 prevents unnecessary vibration components that become noise from propagating from the storage 31 to the waveguide rod 33 .
Here, acoustic impedance will be explained. AE waves, which are ultrasonic waves, are partly reflected at boundaries between regions having different acoustic impedances, and the transmitted AE waves are attenuated. Acoustic impedance is represented by Equation 1 below.
Formula 1: Z=ρ・C
Acoustic impedance is a constant inherent to a substance, and generally MRayl (mega-rail) is used as a unit. 1 MRayl=1×10 ⁶ kg·m ⁻² ·s ⁻¹ . In Equation 1, ρ represents the density of the acoustic medium and C represents the speed of sound in the acoustic medium.
The smaller the acoustic impedance difference between different media, the smaller the reflection at the medium boundary (interface), and the larger the acoustic impedance difference, the larger the reflection at the interface.
Making the acoustic impedance of the material of the sound absorbing material 34 sufficiently smaller than that of the waveguide rod 33 has the effect of making it difficult for unnecessary vibration components from the outside to be transmitted through the sound absorbing material 34 .

The temperature control mechanism 35 controls the temperature inside the hangar 31 by blowing into the hangar 31 the gas cooled by the cooling mechanism 22 provided outside the heat treatment furnace 11 .

The determination unit 21 acquires the AE signal and temperature signal from the sensor unit 32 . The determination unit 21 detects the waveform of the AE signal and determines whether or not the workpiece 12 is abnormal. Also, the determination unit 21 passes the temperature signal to the cooling mechanism 22 .
The cooling mechanism 22 cools the gas sent to the hangar 31 . This cooling is feedback control based on the temperature signal obtained via the determination section 21 .

Thus, the determination unit 21, the cooling mechanism 22, and the inspection device 30 constitute an inspection system. The inspection device 30 inspects the workpiece 12 during heat treatment inside the heat treatment furnace 11 . Since the sensor unit 32 is sealed with the hangar 31 and the sound absorbing member 34, the temperature inside the heat treatment furnace 11 does not become unstable, and the sensor unit 32 is not exposed to a temperature higher than the heat resistance temperature. . Since the inspection device 30 is arranged inside the heat treatment furnace 11, the waveguide rod 33 can be shortened and the elastic wave can be detected with high accuracy.

FIG. 2 is an explanatory diagram of a semiconductor manufacturing process using the inspection method according to the embodiment. First, a semiconductor wafer is prepared in a substrate preparation step (step S101), and a thin film is formed on the surface of the semiconductor wafer in a film forming step (step S102). Next, heat treatment is performed to remove stress from the thin film (step S103), and electrodes are formed on the thin film (step S104).
After conducting an electrical property test (step S105) of the electrode, etching (step S106) is carried out to process the thin film and form a device. Then, heat treatment (step S107) is performed to remove the stress, and the device electrical characteristics are inspected (step S108) to complete the semiconductor wafer (step S109).

The inspection method of this embodiment can be applied to the heat treatment in step S103 and the heat treatment in step S107. FIG. 3 is an explanatory diagram of inspection during heat treatment in step S107. When the inspection is performed during the heat treatment in step S107, a plurality of inspection devices 30 (30-1 to 30-3) are brought into contact with different positions of the semiconductor wafer and the inspection is performed simultaneously.

When a crack occurs in the thin film of the semiconductor wafer, an elastic wave is generated from the location of the crack and propagates through the semiconductor wafer. Therefore, when a plurality of inspection apparatuses 30 detect elastic waves at a plurality of positions, the determination unit 21 can identify the crack generation position from the difference in detection timing of the elastic waves.

4 and 5 are explanatory diagrams of a configuration example of the inspection device 30. FIG.
The AE sensor of the sensor unit 32 is made of piezoelectric material. The structure of the AE sensor includes a resonance type (narrowband type) and a broadband type, and either type may be used. The types of AE sensors include single-end type, differential type, and preamplifier built-in type, and any of them may be used. Also, the sensor is not limited to the examples given here, and any type of sensor can be used as long as it can detect the frequency band of the AE wave (10 kHz to several MHz).

The waveguide rod 33 is a metal or ceramic rod. By bringing the tip portion of the waveguide rod 33 into contact with the object 12 to be processed, an elastic wave whose sound source is a crack generated in the object 12 propagates through the waveguide rod 33 and reaches the AE sensor. An AE sensor is installed on the plane of the waveguide rod 33 . The AE sensor may be fixed with an adhesive. Alternatively, an AE sensor holder containing a spring may be attached to the waveguide rod 33 and the AE sensor may be fixed by spring pressure.
A couplant as an acoustic transmission medium is interposed between the wave receiving surface of the AE sensor and the plane of the waveguide rod 33 . The material of the couplant is grease, wax, adhesive, or the like. The function of the couplant is to prevent reflection of sound waves and facilitate transmission of AE waves to the receiving surface of the AE sensor. Ultrasonic waves, which are high-frequency sound waves, are substantially totally reflected at the interface with air. Therefore, the gap between the plane of the waveguide rod and the wave-receiving surface of the AE sensor is filled with couplant so that air and minute air bubbles do not enter.

In the inspection apparatus 30a shown in FIG. 4, the sound absorbing member 34 is formed by combining the sound absorbing member 34a in contact with the waveguide rod 33 and the sound absorbing member 34b in contact with the storage 31. As shown in FIG. In this configuration, by configuring the sound absorbing member 34b with a material softer than that of the sound absorbing member 34a, it is possible to suppress the invasion of disturbance noise components from the hangar 31. FIG.

In the inspection apparatus 30b shown in FIG. 4, a sound absorbing member 34c exposed to the inside of the heat treatment furnace 11 and a sound absorbing member 34d inside the hangar 31 are combined to form the sound absorbing member 34. As shown in FIG. In this configuration, by arranging a sound absorbing member that can handle high temperatures as the sound absorbing member 34 c on the furnace side, there is an effect of preventing the temperature from flowing into the storage 31 via the sound absorbing member 34 .

In the inspection apparatus 30 c shown in FIG. 5 , the temperature control mechanism 35 sends gas having a temperature lower than the temperature inside the furnace to the vicinity of the through-hole through which the waveguide rod 33 penetrates the storage 31 .
An inspection apparatus 30d shown in FIG. 5 has an inner storage 31b inside an outer storage 31a, and has a double structure wall member at least in the vicinity of the through hole. In the inspection device 30d, the temperature control mechanism 35 sends gas having a temperature lower than the temperature inside the furnace into the double structure of the wall member. By doubling the hangar 31 in this manner, it is possible to prevent the cooled air in the inner hangar 31b from leaking out of the inner hangar 31b and further into the furnace.

FIG. 6 is an explanatory diagram of signal processing of the AE sensor. The AE signal detected by the AE sensor 51 is first amplified by the preamplifier 52 , cuts off low frequency components and high frequency components as noise by the bandpass filter 53 , and is further amplified by the main amplifier 54 . After that, it is sampled by an analog-to-digital (AD) converter 55 . Furthermore, the envelope of the AE waveform is obtained by full-wave rectification envelope detection 56, and determination 57 is performed based on the generation time of the AE wave, the intensity of the AE wave, the energy, and the like. For the determination 57, for example, a threshold voltage may be set and the size of the crack may be estimated from the intensity of the AE wave. In addition, any determination method can be employed, such as determination of occurrence of cracks from time-series changes in the frequency spectrum, which is the frequency response of the AE wave. The determination result is output 58 on a predetermined screen. In addition, when an abnormality occurs, a lamp may be turned on for indication.

When a crack occurs or when an already formed crack develops, an AE wave is detected that has a sharp rise and decays while oscillating at a high frequency. This is called a sudden AE wave. The sudden AE wave is subjected to full-wave rectification and envelope detection, and compared with two levels of high and low voltage thresholds VH and VL. A period is detected as one AE event. One AE event corresponds to one crack occurrence. In addition, by using two or more AE sensors, it is possible to specify the position of the sound source, that is, the position of the crack, based on the arrival time difference of the AE waves to each sensor.

FIG. 7 is an explanatory diagram of the utilization of crack occurrence positions. As already explained, by acquiring AE signals at a plurality of positions on the semiconductor wafer, the positions where cracks occur on the semiconductor wafer can be identified. For the sake of convenience, the information specifying the crack generation position in the semiconductor wafer is referred to as AE position information.

On the other hand, formation of electrodes and etching of thin films on semiconductor wafers are performed based on device design data. Therefore, by associating the AE position information with the device design data, the device located at the crack occurrence position can be identified as the defective device. By outputting the information specifying the defective device as defective device information, it can be used for processing evaluation. It is also possible to exclude defective devices and reduce the defect rate in finished products.

Thus, by applying the inspection of the present invention to the heat treatment in step S107 and detecting AE signals at a plurality of positions on one semiconductor wafer, inspection can be performed for each device.
On the other hand, the heat treatment in step S103 is performed before devices are formed on the semiconductor wafer, and a plurality of semiconductor wafers are collectively processed. When applying the inspection of the present invention for this heat treatment, the inspection may be performed in units of semiconductor wafers.

FIG. 8 is an explanatory diagram of inspection for each semiconductor wafer. In FIG. 8, the heat treatment apparatus 60 has a configuration in which a plurality of semiconductor wafers are placed as the workpieces 12 inside a heat treatment furnace 61 and heat treated. A plurality of inspection devices 80 (80-1 to 80-2) are arranged inside the heat treatment furnace 61, and are connected to the determination unit 71 and the cooling device 72, respectively.

One inspection device 80 is in contact with each of the plurality of semiconductor wafers. Therefore, in the configuration of FIG. 8, the presence or absence of cracks can be inspected for each semiconductor wafer.

As described above, the disclosed inspection apparatus includes a sensor unit 32 including an acoustic emission sensor located inside a heat treatment furnace, and housing the acoustic emission sensor to detect the ambient temperature of the sensor and the temperature of the heat treatment furnace. and a waveguide rod 33 penetrating through the storage 31 and attached with the acoustic emission sensor at one end and having the other end in contact with the object to be inspected in the heat treatment furnace.
Further, the through hole through which the waveguide rod 33 passes through the storage 31 is filled with a sound absorbing member 34 .

In such a configuration, since the waveguide rod 33 can be shortened by arranging the AE sensor in the heat treatment furnace, accuracy is improved. Further, since the AE sensor is sealed in the hangar 31, the AE sensor can be protected from the heat inside the furnace without destabilizing the temperature inside the furnace. Therefore, the object can be accurately inspected during the heat treatment.

Also, by using a combination of two or more sound absorbing members having different temperature characteristics and/or sound absorbing characteristics, it is possible to effectively block noise from the hangar 31 and maintain the temperature inside the hangar 31 .

Also, a temperature control mechanism 35 for controlling the temperature inside the hangar 31 may be further provided. The temperature control mechanism 35 sends a gas having a temperature lower than the temperature inside the furnace to the vicinity of the through hole through which the waveguide rod 33 penetrates the storage 31 .
Further, the hangar 31 may have a double structure wall member at least in the vicinity of the through hole, and the temperature control mechanism 35 may be configured to send the gas into the double structure of the wall member.
A temperature sensor may be further included in the hangar, and the temperature control mechanism may deliver cooled gas based on the output of the temperature sensor.
With these configurations, the temperature of the hangar 31 can be maintained more effectively.

Also, the determination unit 21 that processes the output of the acoustic emission sensor to determine the state of the inspection object and the cooling mechanism 22 can be provided outside the heat treatment furnace 11 .
The determination unit 21 can identify a position where an abnormality occurs in the inspection object by comparing elastic waves acquired from a plurality of positions of the inspection object.
For example, the object to be inspected is a semiconductor wafer, and the determination unit 21 uses the position of occurrence of the abnormality and the design data of the semiconductor wafer to determine which of the plurality of devices formed on the semiconductor wafer has the abnormality. identify whether

It should be noted that the present invention is not limited to the above embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. Moreover, not only deletion of such a configuration but also replacement and addition of the configuration are possible.
For example, in the above-described embodiment, the structure in which the hangar 31 is doubled was exemplified, but a structure with three or more layers may also be used.
In the above-described embodiments, the inspection of semiconductor wafers was exemplified, but the present invention can be applied to any heat treatment such as firing of ceramics.

10: heat treatment device, 11: heat treatment furnace, 12: object to be processed, 21: determination unit, 22: cooling mechanism, 30: inspection device, 31: hangar, 32: sensor unit, 33: waveguide rod, 34: sound absorbing member , 35: temperature control mechanism, 51: AE sensor, 52: preamplifier, 53: bandpass filter, 54: main amplifier, 55: AD converter, 56: full-wave rectification envelope detection, 57: judgment, 58: output

Claims (12)

an acoustic emission sensor located inside the heat treatment furnace;
a hangar that stores the acoustic emission sensor and makes the temperature around the sensor different from the temperature inside the heat treatment furnace;
and a waveguide rod penetrating through the storage, having one end attached with the acoustic emission sensor, and the other end contacting an object to be inspected in the heat treatment furnace. 2. The inspection apparatus according to claim 1, wherein a through hole through which said waveguide rod penetrates said housing is filled with a sound absorbing member. 3. The inspection apparatus according to claim 2, wherein two or more sound absorbing members having different temperature characteristics and/or sound absorbing characteristics are used in combination. 2. The inspection apparatus according to claim 1, further comprising a temperature control mechanism for controlling the temperature inside said hangar. 5. The inspection apparatus according to claim 4, wherein the temperature control mechanism sends a gas having a temperature lower than the temperature inside the furnace to a vicinity of a through hole through which the waveguide rod penetrates the storage. The hangar has a double structure wall member at least in the vicinity of the through hole,
6. The inspection apparatus according to claim 5, wherein the temperature control mechanism sends the gas into the double structure of the wall member. further comprising a temperature sensor within the hangar;
The inspection apparatus according to claim 4, wherein the temperature control mechanism sends cooled gas based on the output of the temperature sensor. an acoustic emission sensor located inside the heat treatment furnace;
a hangar that stores the acoustic emission sensor and makes the temperature around the sensor different from the temperature inside the heat treatment furnace;
a waveguide rod that penetrates the hangar, has the acoustic emission sensor attached to one end, and has the other end in contact with the test object of the heat treatment furnace;
and a judgment unit outside the heat treatment furnace that processes the output of the acoustic emission sensor and judges the state of the object to be inspected. a cooling mechanism provided outside the heat treatment furnace;
Further comprising a temperature control mechanism for controlling the temperature inside the hangar,
9. The inspection system according to claim 8, wherein the temperature control mechanism sends gas cooled by a cooling mechanism to the interior of the hangar. 9. The inspection system according to claim 8, wherein the determination unit compares elastic waves acquired from a plurality of positions on the inspection object to identify a position where an abnormality occurs in the inspection object. The object to be inspected is a semiconductor wafer,
The determination unit uses the position of occurrence of the abnormality and the design data of the semiconductor wafer to identify which of a plurality of devices formed on the semiconductor wafer has the abnormality. Item 11. The inspection system according to Item 10. an inspection device comprising an acoustic emission sensor mounted inside the hangar on one end of a waveguide rod penetrating the hangar acquires an acoustic wave to be inspected inside the heat treatment furnace;
a step of outputting the elastic wave to a determination unit;
and a step in which the determination unit determines an abnormality of the inspection target based on the elastic wave.

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