JPH1126530A - Apparatus and method of inspecting circuit pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a shape contrast image and potential contrast intensified image with high accuracy, using the same apparatus by comprising a select switch for intensifying desired contrast according to the material of a substrate under test or manufacturing process and a control system for changing desired conditions accompanied therewith. SOLUTION: A retarding electric field formed between a substrate 10 under test and ground electrode 40 accelerates sec. electrons 202 from the substrate 10 upwards in the normal direction to the substrate with suppressing the divergence through a sec. electron focus electrode 41, an ExB deflector 8 deflects only the sec. electrons 202 arrival thereat to a reflector 300, the electrons 202 collide against the reflector 300 to generate new sec. electrons 203 which are then caught by a attraction electric field formed between a detector 13 and attraction electrode 14 around the detector 13 while other conditions are controlled for optimized conditions to obtain a good image at a contrast varied according to the inspection mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a semiconductor device, and more particularly, to a technique for inspecting a pattern on a wafer in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art As an inspection apparatus for detecting a defect of a circuit pattern formed on a wafer in the process of manufacturing a semiconductor device by image comparison, a pattern inspection apparatus using an electron beam is disclosed in Japanese Patent Application Laid-Open No. Sho 59-192943. Vac. Sci. Tech. B, Vo
l. 9, No. 6, pp. 3005-3009 (1991), J. Vac. Sc
i. Tech. B, Vol. 10, No. 6, pp. 2804-2809 (199
2), SPIE Vol.2439, pp.174-183, and JP-A-5-258
No. 703, for example. There, it is necessary to acquire an image at a very high speed in order to obtain a practical throughput. And in order to secure the SN of the image acquired at high speed, it is more than 100 times (10
Using an electron beam with a current of at least nA), the practical inspection speed is maintained while ensuring the SN of the image. Furthermore, a low-acceleration electron beam of 2 keV or less is irradiated with a low-acceleration electron beam (electron and ion beam handbook (Nikkan Kogyo Shimbun) p622) so that the semiconductor substrate with an insulating film such as a resist is not affected by charging.
-P623). However, an electron beam having a large current and a low acceleration causes an aberration due to the space charge effect, and it is difficult to perform high-resolution observation. As a method for solving this problem, there is known a method of decelerating a high acceleration electron beam immediately before a sample and irradiating the sample with a substantially low acceleration electron beam (for example, Japanese Patent Application Laid-Open No. 5-258703).
No., JP-A-06-139985, public information, USP.5578821).

On the other hand, a defect in a circuit pattern is not inspected with an image of a normal shape contrast of a secondary electron signal, but a disconnection, a short circuit, a defective opening of a contact hole, and the like are identified by using an image in which a potential contrast is enhanced. The demand for testing is also growing. Acquisition of a potential contrast-enhanced image is well known in the related art.
Physics E, 1968, s2, Vol.1, pp.902-906, SPIE V
ol.2439, pp.174-183, etc.

[0004] An outline of a conventional electron optical system is shown in FIG.
This will be described more simply. The primary electron beam 201 emitted from the electron gun 1 by the voltage of the extraction electrode 2 passes through the condenser lens 3, the scanning deflector 5, the aperture 6, the objective lens 9, and the like, and is converged and deflected, and the semiconductor on the sample stages 11, 12 The light is applied to the device substrate 10. A deceleration voltage (hereinafter, referred to as a retarding voltage) is applied to the substrate 10 from a power supply 58 for decelerating the primary electron beam. Secondary electrons 202 are generated from the substrate 10 by irradiation of the primary electron beam 201. The retarding voltage acts on the secondary electrons 202 as an acceleration voltage, and the secondary electrons 202 are accelerated to an energy of several keV. An EXB deflector 8 is provided adjacent to the electron gun side of the objective lens 9. The EXB deflector 8 is a deflector that deflects the primary electron beam 201 by the amounts of electric field and magnetic field that cancel each other, and deflects the secondary electron 202 by superimposing them. The accelerated secondary electrons 202 are deflected by the EXB deflector 8 and further attracted to an electric field formed by an attraction voltage between the attraction electrode 14 externally attached to the detector 13 and the detector 13 and incident on the detector 13 I do.
The detector 13 is constituted by a semiconductor detector. Secondary electron 20
2 enters the semiconductor detector to form an electron-hole pair, which is taken out as a current and converted into an electric signal. This output signal is further amplified by the preamplifier 21 and becomes an image signal luminance modulation input. After the image of one area on the substrate is obtained by the operation of the electron optical system described above, the image output signal is delayed by one screen, and the image of the second area is similarly obtained. The two images are compared by an image comparison and evaluation circuit to detect a defective portion of the circuit pattern.

[0005]

However, this circuit pattern inspection apparatus has the following problems. In order to obtain a shape contrast image of the sample surface with high resolution,
It is necessary to detect a change in the amount of secondary electrons generated from one point on the sample with high accuracy. Therefore, it is necessary to guide the generated secondary electrons to the detector as efficiently as possible to detect them. On the other hand, when there is a potential distribution on the sample surface, the secondary electrons generated from the sample are emitted with a velocity distribution according to the potential distribution near the surface. Since the information on the velocity distribution is information on the potential contrast on the sample surface, it is necessary to save the velocity information immediately after the generation of the secondary electrons in order to obtain a potential contrast enhanced image. That is, the information of the surface potential is not a change in the amount of generated secondary electrons but whether the secondary electrons pass through a spatial filter after generation.

In the above prior art, a low speed (5
The above-mentioned retarding electric field (several kV) becomes an accelerating electric field for the secondary electrons generated within 0 eV), and accelerates almost upward in the normal direction of the sample surface regardless of the initial velocity of the secondary electrons. Therefore, secondary electrons can be captured regardless of the initial velocity, and a shape contrast enhanced image can be obtained by this operation. However, this prior art does not consider a capturing method for capturing more secondary electrons, and it is difficult to obtain highly accurate shape contrast. On the other hand, in order to obtain a potential contrast enhanced image in this electron optical system, it is necessary to reduce the retarding voltage and store information on the velocity of secondary electrons near the surface. However, when the retarding voltage is low, secondary electrons generated at various angles from the sample diverge in the same direction and deviate before reaching the detector. Is difficult to obtain.

As described above, in the prior art, it was difficult to obtain a shape contrast emphasized image and a potential contrast emphasized image with the same electron optical system with high accuracy. Therefore, it has not been possible to select a high-precision inspection with a desired contrast image according to the type of the substrate to be inspected and the processing step.

An object of the present invention is to solve the above-mentioned problems, and obtain not only a normal shape contrast enhanced image but also a potential contrast enhanced image with high accuracy by the same inspection apparatus, and it is possible to obtain the type of substrate to be inspected and the processing steps. Inspection mode selection is performed accordingly, and the resulting image is automatically compared and inspected to detect a defect quickly and without error. It is another object of the present invention to reflect the results on the manufacturing conditions of the semiconductor device, to improve the reliability of the semiconductor device and to reduce the defect rate.

[0009]

In order to solve the above problems, we have a step of scanning the first and second regions of a substrate on which a circuit pattern is formed with a primary electron beam, and the steps of: An electron beam acceleration / deceleration step of decelerating the primary electron beam and accelerating secondary electrons generated secondarily from the region by the primary electron beam; and deflecting the primary electron beam by an electric field and a magnetic field. A deflection step in which the amount is canceled and an electromagnetic field that exerts a deflection action by superposition of an electric field and a magnetic field on the secondary electrons is generated, a step of detecting a signal of the secondary electrons, and A circuit pattern inspection method comprising: a step of obtaining an image of a region; a step of comparing the image of the first region with the image of the second region; and a step of determining a defect of a circuit pattern from the comparison result. In the way, on A step of converging the secondary electrons simultaneously with the acceleration / deceleration step on the substrate; and selectively operating voltages and current values of the acceleration / deceleration step and the secondary electron convergence step according to the type and processing step of the substrate. A selecting step to be changed, and in conjunction with the selecting step, changing all or a part of an accelerating voltage of the primary electron beam, an operating voltage and a signal of the convergence step, the deflecting step, and the EXB deflecting step to a desired value. A circuit pattern inspection method and apparatus, characterized in that the inspection method selectively performs the inspection using the shape contrast image and the potential contrast image. In the detection of the secondary electrons, a configuration was employed in which the secondary electrons from the sample were applied to the solid piece and the secondary electrons newly generated from the solid piece were attracted to the detector. This solid piece was composed of two or more materials having different secondary electron generation efficiencies. Further, in order to observe the insulator in a stable charged state, an inspection including preliminary irradiation means and a step of irradiating the area with another electron beam before scanning the primary electron beam on the sample was also performed.

By implementing the above-described method and apparatus, when a normal shape contrast image is to be obtained, a high retarding voltage is applied to the sample, and the primary electron beam accelerating voltage is increased in conjunction with the application of the high retarding voltage. By irradiating a primary electron beam in which the expansion of the diameter due to the charge effect is suppressed, the generated secondary electrons can be accelerated at high speed and extracted upward in the normal direction of the sample surface. At this time, the same voltage as the retarding voltage is applied to the secondary electron focusing electrode provided just above the sample to form a converging electric field that suppresses the divergence of the secondary electrons, and the maximum number of secondary electrons is drawn upward. Can be. On the other hand, when it is desired to enhance the potential contrast, a relatively low retarding voltage is applied to the sample to generate low-speed secondary electrons and apply a spatial filter to obtain surface potential information. Furthermore, since secondary electrons are applied to a reflector made of two or more materials having different secondary electron generation efficiencies and new secondary electrons generated by the reflector are captured by the detector, a further spatial filter effect is added. The surface potential information can be further enhanced.
In the case of this low retarding voltage, the acceleration voltage of the primary electron beam is also reduced in conjunction with the primary electron beam to prevent the irradiation energy of the primary electron beam from relatively increasing and damaging the sample.
As a result, the beam spread due to the space charge effect also increases.However, the size of disconnection, short circuit, opening defect, etc. to be found in the potential contrast is on the order of μm, which is larger than the resolution required for defect inspection by ordinary shape contrast, May be larger than the beam diameter at the time of acquiring the shape contrast image. The scanning speed was increased in accordance with the increase in the beam diameter, making it possible to inspect the substrate at high speed. vice versa,
It is also possible to obtain a high-precision potential contrast image by performing arithmetic processing such as averaging of secondary electron signals between adjacent positions without increasing the scanning speed. In some cases,
Instead of directly increasing the beam diameter, the beam may be converged by changing the excitation condition of the lens. In addition, since the acceleration energy of the secondary electrons decreases, the operating conditions of the ExB deflector also need to be changed in conjunction with the amount of secondary electron deflection toward the detector. As described above, in order to enhance the desired contrast and form an image by changing the retarding voltage, the secondary electron focusing electrode is operated, the primary beam acceleration voltage, the lens excitation condition, the scanning deflection signal,
It is necessary to change the operating conditions of the B deflector in conjunction with it. For this reason, the present invention has a configuration including a selection switch for enhancing desired contrast according to the material of the substrate to be inspected and a processing step, and a control system for changing desired conditions accompanying the selection switch.

With these effects, according to the present invention,
With the same device, not only shape contrast images but also potential contrast enhanced images can be acquired with high accuracy, and as a result, it is possible to select an inspection mode according to the type of inspection board and processing process and obtain an image with the desired contrast enhancement As a result, a circuit pattern inspection apparatus and method capable of quickly performing the required inspection without error can be obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of an inspection method and an apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 shows the configuration of the apparatus, and FIG.
The outline of the semiconductor device manufacturing process is shown in FIG. As shown in FIG. 2, a number of pattern forming steps are repeated in the semiconductor device manufacturing process. The pattern formation process is roughly
It is composed of steps of film formation, photosensitive resist coating, light exposure, development, etching, resist removal, and cleaning.
If the manufacturing conditions are not optimized in each of these steps, the circuit pattern of the semiconductor device will not be formed properly. For example, when an abnormality occurs in the film forming process of FIG. 2, particles are generated, adhere to the wafer surface, and an isolated defect or the like occurs. In addition, during exposure after resist application, if conditions such as focus and exposure time are not optimal, there may be places where the amount or intensity of light applied to the resist is too large or insufficient, resulting in short-circuits, disconnections, and pattern narrowing. . If there is a defect on the mask reticle at the time of exposure, similar pattern shape abnormality is likely to occur. In addition, when the etching amount is not optimized, and due to a thin film or a particle generated during the etching, a short circuit, a projection, an isolated defect, an opening defect, and the like also occur. At the time of cleaning, abnormal oxidation is likely to occur at the corners of the pattern and other places depending on the condition of running out of water during drying. Therefore, in the wafer manufacturing process, it is necessary to optimize the processing conditions so that these defects do not occur, and it is necessary to detect the occurrence of an abnormality at an early stage and feed it back to the process.
Therefore, in this embodiment, an example will be described in which the inspection is applied after resist exposure and development in the n-th pattern forming step shown in FIG.

First, an outline of an inspection method and an inspection apparatus for detecting the above-described defect will be described below.

The basic concept of the present invention is to select a desired inspection mode according to the type of a substrate and a processing step, and to inspect the secondary electrons generated from the substrate only as a normal shape contrast image. In other words, a high-accuracy potential contrast-enhanced image obtained by converting the velocity distribution of secondary electrons near the sample into a signal is to be obtained. The initial velocity distribution of secondary electrons is preserved by lowering the retarding voltage applied to the sample substrate, and deviation due to secondary electron divergence caused by lowering the retarding voltage is prevented by the secondary electron focusing electrode. Even when a low retarding voltage is applied, the primary beam extraction voltage, lens conditions, scan change conditions, and the like are changed in conjunction so that the primary beam is irradiated to the sample with a desired beam diameter and irradiation energy. In addition, since the acceleration voltage of the secondary electrons changes, the secondary electron deflection conditions also change accordingly.

Next, embodiments will be described in detail.

FIG. 1 shows a configuration diagram of the first embodiment. Inspection devices are roughly divided into electron optical system 101, sample chamber 102, control unit 10
3. It is composed of an image processing unit 104. Electron optics 101
Is electron gun 1, electron beam extraction electrode 2, condenser lens
3. It is constituted by a deflector 4 for a Franking scan, a scanning deflector 5, an aperture 6, a shield pipe 7, an EXB deflector 8, an objective lens 9, a ground electrode 40, a secondary electron focusing electrode 41 and the like. A reflector 300 is provided on the shield pipe 7. The sample chamber 102
−Y stage 11, rotating stage 12, optical height measuring device 2
3. Consists of a position monitor 24, and 2
A secondary electron detector 13 is located above the objective lens 9, and an output signal of the secondary electron detector 13 is amplified by a preamplifier 21 and converted into digital data by an AD converter 22. The image processing unit 104 includes image storage units 30a and 30b, a calculation unit 33, and a defect determination unit. The captured electron beam image and optical image are displayed on the monitor 32. The operation command and operation condition of each part of the inspection device are input and output from the control unit 103. Conditions such as acceleration voltage, electron beam deflection width, deflection speed, deflection direction, sample stage moving speed, and signal acquisition timing of the detector are input to the control unit 103 in advance. An inspection mode selection switch 36 is connected to the control unit 103, and control is performed under operating conditions corresponding to the inspection mode. More specifically, it controls the voltage supply voltage 58 to be applied to the substrate to be inspected and the secondary electron focusing electrode power supply 57, and accordingly, the electron gun power supply 51, the electron beam extraction voltage power supply 52, the scanning deflection signal generator 53, and the ExB deflector power supply system 54. The objective lens power supply 55 is controlled to a desired operating condition. For this purpose, the above conditions are input to the control unit as appropriate operating conditions in advance, and are changed as necessary. In addition, a correction signal is generated from the signals of the optical height measuring device 23 and the position measuring
Objective lens power supply 5 so that 201 is always irradiated to the correct position
5, and a correction signal is sent from the correction control circuit 35 to the scanning signal generator 54.

As the electron gun 1, a diffusion-supply type thermal field emission electron source was used. As a result, it is possible to obtain a comparative inspection image with a small variation in brightness and to increase the electron beam current, so that a high-speed inspection can be performed. The electron beam 201 is extracted from the electron gun 1 by applying a voltage to the extraction electrode 2. The electron beam 201 is accelerated by applying a high negative potential to the electron gun 1. As a result, the electron beam 201 travels toward the sample stage 11 with energy corresponding to the potential, is converged by the concentration 3, is further narrowed down by the objective lens 9, and is mounted on the XY stage 11. Irradiates 10 (wafer or chip, etc.). A negative voltage can be applied to the test substrate 10 by a test substrate application voltage power supply 58. By adjusting the test substrate applied voltage power supply 58, it becomes easy to adjust the electron beam irradiation energy to the test substrate 10 to an optimum value. Either a method in which the XY stage 11 is stationary and the electron beam 201 is scanned two-dimensionally for image formation, or a method in which the electron beam is scanned only one-dimensionally and the XY stage 11 is continuously moved in a direction orthogonal to the scanning direction Can be selected. When inspecting only a specific place, the stage is stopped and inspected, and when inspecting a wide range of the substrate 10 to be inspected, the stage is continuously moved to inspect, so that efficient inspection can be performed.

In order to obtain an image of the substrate 10 to be inspected,
The inspection target substrate 10 is irradiated with a finely focused electron beam 201 to generate secondary electrons, and these are detected in synchronization with scanning of the electron beam 201 and movement of the stage, thereby obtaining an image of the surface of the inspection target substrate. In the automatic inspection as described in the present invention, a high inspection speed is essential. Therefore, unlike a normal SEM, a beam current of the order of pA is scanned at a low speed, and scanning is not performed a plurality of times. Therefore, a configuration is adopted in which an image is formed by scanning only once with a large current electron beam of, for example, 100 nA which is about 100 times or more that of a normal SEM. The image signal was delayed by one image, and the image comparison and evaluation were performed in synchronization with the capture of the next image, thereby searching for defects on the circuit board.

The secondary electrons 202 from the substrate 10 are suppressed from diverging by the secondary electron focusing electrode 41 while the inspected substrate 10 and the ground electrode
Due to the retarding electric field formed by 40, the substrate is accelerated upward in the normal direction of the substrate surface. Then, the light reaches the ExB deflector 8 and only the secondary electrons 202 are deflected in the direction of the reflection plate 300. When the secondary electrons 202 collide with the reflection plate 300, second secondary electrons 203 are newly generated from the collision point, and the detector 13 and the suction electrode 14 around the detector are generated.
Are captured by the detector 13 by the attraction electric field formed by. The reflection plate 300 was made of three types of materials having different secondary electron generation efficiencies as shown in FIG. The above is the outline of the configuration and operation of the present apparatus.

Next, the nature of the secondary electrons will be described. When the primary electron beam enters the solid, it enters the inside and excites electrons in the shell at each depth, losing energy. Also, there occurs a phenomenon in which the reflected electrons generated by the backscattering of the primary electron beam travel toward the surface while also exciting the electrons in the solid. Through these multiple steps, the electrons in the shell cross over the surface barrier from the solid surface to become secondary electrons, and exit into the vacuum with energy of 0 to 50 eV. The smaller the angle between the primary electron beam and the solid surface, the smaller the ratio of the entrance distance of the primary electron beam to the distance from the position to the solid surface, and the more easily secondary electrons are emitted from the surface. Therefore, the generation of secondary electrons greatly depends on the angle between the primary electron beam and the solid surface, and the amount of secondary electrons generated becomes the shape contrast of the sample surface. The detection signal amount of secondary electrons can be expressed by the following equation.

(Detection signal amount of secondary electrons) = (generation amount of secondary electrons) * (capture efficiency) * (detection gain) (1) Therefore, the shape contrast is 100% of the capture efficiency of equation (1). In this case, it is possible to obtain with ideal high precision.

On the other hand, when a potential distribution exists on the sample surface, the secondary electrons are emitted with an initial velocity distribution according to the potential distribution near the sample. That is, the potential distribution on the surface does not contribute to the amount of secondary electrons generated in equation (1). The secondary electrons are subjected to spatial filtering inside the electron optical system according to the initial velocity distribution, and the trapping efficiency of the secondary electrons in equation (1) changes, and the result is the potential contrast. However, strictly speaking,
In a normal secondary electron image, the above-described shape contrast and potential contrast are mixed.

The means and method for enhancing the shape contrast and the potential contrast will be described below. The inspection mode for enhancing the shape contrast is referred to as a normal mode, and the case for enhancing the potential contrast is referred to as a potential contrast mode. FIG. 4 shows an electron optical system 103 around the secondary electron focusing electrode 41.
2 shows an enlarged view of a part of FIG. The same potential as the retarding voltage is applied to the secondary electron focusing electrode 41 provided between the ground electrode 40 and the substrate 10. As a result, a secondary electron focusing electric field shown by equipotential lines in the figure is formed. As shown in FIG. 5, the structure of the secondary electron focusing electrode 41 is a hollow truncated cone with the central axis of the primary electron beam as an axis. The hollow part in the figure is the diameter a1 of the upper end
Is larger than the diameter a2 at the lower end, and
l is a straight line in this embodiment. In this embodiment, the dimensions a1 and a2 of the secondary electron focusing electrode 41 are the opening radii a0 and a1 of the ground electrode 40.
= A0 + 1 mm and a2 = a0-1 mm. The ground electrode 40 and the focusing electrode 41 were sufficiently separated so as not to discharge.

The operation in the normal mode in this configuration will be described. The normal mode is selected with the inspection mode selection switch 36, and the voltage applied to the electron gun 1 is set to -12 kV,
The primary electron beam 201 is accelerated to 12 kV with an accelerating electric field of up to 12 kV.
According to the input value from the control unit 103, the deflection system 5, the lens system 3, E
The xB deflector 8 also operates under appropriate conditions at the same time. Primary electron beam 2
01 is applied to the sample substrate 10 to generate first secondary electrons 202 first. The energy at the time of generation of the first secondary electrons 202 is 50 eV or less, and is rapidly accelerated by a secondary electron acceleration electric field formed between the substrate 10 and the ground electrode 40 to which the retarding voltage -11.5 kV is applied. Proceed in the direction normal to the substrate surface. Specifically, as shown in FIG. 6, the secondary electrons 202 having an initial energy of 2 eV emitted from the surface with a spread of -90 ° to 90 ° have an angle distribution of -10 ° to 10 ° from the surface to 2 mm in height. The spreading width is within about 1 mm. Further, the secondary electrons 202 emitted from the surface at a shallow angle with a higher initial energy also receive a force converging to the central axis by the converged electric field formed by the secondary electron focusing electrode 41 and the substrate 10. The secondary electrons 202 thus efficiently extracted in the normal direction are bent by 3 degrees toward the detector 13 by the ExB deflector 8 and collide with the reflector 300. Reflector 30
From 0, a second secondary electron 203 having an energy of 0 to 50 eV
Occurs. The second secondary electrons 203 are attracted to the front surface of the detector by the attraction electric field generated by the detector 13 and the attraction electrode 14 attached to the detector. The detector 13 was constituted by a semiconductor detector of Si, the detector and the entire detection circuit system were floated at 6 kV, the suction electrode 14 was set to 0 V, and the effective detection area of the detector 13 was set to 4πmm 2. By this operation, 90% or more of the secondary electrons 203 generated from the sample can be captured. The second secondary electrons 203 enter the semiconductor detector and are converted into an electric signal. This electric signal is further amplified by the preamplifier 21 and taken in as an image luminance signal.

Next, the potential contrast enhancement mode will be described. The irradiation energy of the primary electron beam 201 is set to 500 eV, which is the same as that in the normal mode, the primary electron beam 201 is extracted from the electron gun power supply 28 at 2 kV, and the retarding voltage is reduced.
1.5 kV was applied. Since the primary electron beam 201 becomes a low-speed large-current beam, the beam diameter expands due to the space charge effect and expands to about 0.4 mm on the substrate 10. The order is large and does not hinder the inspection. Since the electron beam diameter becomes twice or more as compared with the normal mode, in this embodiment, the scanning speed is doubled and the inspection speed is increased in conjunction with this as shown in FIG. A retarding voltage is applied to the secondary electron focusing electrode 41 as in the normal mode. Fig. 8 shows secondary electrons 202
As shown in FIG. 6, light is emitted from the surface of the substrate 10 at an initial speed according to the surface potential distribution. Although it is accelerated in the normal direction by the retarding electric field, the retarding voltage is relatively low.
The initial velocity distribution of the secondary electrons 202 is guided upward while being stored at a constant rate. The secondary electrons 202 obliquely emitted with high energy to the surface of the substrate 10 are reflected by the electric field near the secondary electron focusing electrode 41 and guided obliquely upward. Further, since the retarding voltage is low, the distribution of the magnitude of the velocity of the secondary electrons 202 is relatively widened. Therefore, as shown in FIG. 9, these secondary electrons 202 are pulled out upward, and ExB
When deflected by the deflector 8, the ExB deflector 8 plays a role of an energy filter, and only the secondary electrons 202 having specific energy and orbital inclination can pass. Further, the secondary electrons 203 that collide with the reflector 300 and are emitted are separated into a case where the secondary electrons 203 are captured by the detector 13 and a case where they are not captured according to the emission position on the reflector 300. Be transformed into Further, as shown in FIG. 3, since the reflecting plate 300 is made of three types of materials having different secondary electron generation efficiencies, the detected secondary electron signal changes depending on the position where the secondary electrons collide with the reflecting plate. Therefore, the effect of a further energy filter is generated. Specifically, the secondary electron generation efficiency for each material is 10: 1
The ratio is set to 00: 1 so that the secondary electron colliding with the middle part of FIG. 3 has the largest signal amount. In addition, in response to the decrease in the acceleration energy of the secondary electrons 202, the operating conditions for the ExB deflector 8 are also changed in conjunction with the amount of deflection of the secondary electrons 202 so as not to change. That is, the acceleration energy, irradiation energy, irradiation beam diameter, scanning deflection signal, and secondary electron deflection amount of the primary electron beam 201 are set to desired values while the secondary electron focusing electrode 41 is operated at a low retarding voltage. Change various conditions in conjunction with operation. For the operating conditions, optimal conditions have been input in advance according to the type of the substrate to be inspected 10 and the processing steps.

By realizing the above-described configuration and operation, a high-quality image can be obtained with high accuracy by selecting an inspection mode. That is, an inspection apparatus is provided which selects an inspection using a normal shape contrast image and an inspection using a potential contrast enhanced image in an electron optical system having the same configuration and performs an inspection without error immediately.

(Embodiment 2) Next, a second embodiment shown in FIG. 10 will be described. The second embodiment is an apparatus for performing preliminary irradiation with another electron beam 302 on the substrate to be inspected 10 in addition to the first embodiment. In the case of a substrate containing an insulator, a stable charge state is created in advance by irradiating a fixed amount of beam, so that a secondary electron signal can be obtained stably. Therefore, the pre-irradiation chamber 105, the pre-irradiation electron gun 15, the stage 43, and the like are installed and once irradiated with a large-diameter beam. Other operations are the same as in the first embodiment.

(Embodiment 3) FIG. 11 shows a third embodiment. In the first and second embodiments, the objective lens 9 is connected to the reflecting plate 3.
00, the substrate to be inspected 10 than the secondary electron detector 13 and the ExB deflector 8
However, in this embodiment, the lens is installed above the reflector 300 to provide a long focal length lens. According to this configuration,
Secondary electrons 202 can be extracted and captured under certain conditions regardless of the excitation conditions of the objective lens 9 for converging the primary beam 201 to a desired diameter. Other operations are first
This is the same as the embodiment.

The embodiment of the present invention has been described above. The point is that the secondary electrons 202 generated on the substrate are suppressed by the secondary electron focusing electrode 41 so as to suppress the divergence and departure even if the retarding voltage is changed. 13 and simultaneously control the other conditions to the optimum conditions, and may be any inspection device or method capable of obtaining a good image with different contrast depending on the inspection mode.The configuration of the secondary electron focusing electrode 41 is the same as that of the embodiment. The configuration is not limited to the above. Any shape suitable for collecting the diverging secondary electrons 202 may be used. The opening diameters of the upper and lower ends are only an example, and the generatrix of the side surface does not need to be a straight line, and may be constituted by a curved line. In the above embodiment, the secondary electron focusing electrode 41
Is fixed, but it may be installed movably.
What is necessary is just to form a converging electric field at an optimum place according to the state of 10. As a configuration at this time, as shown in FIG. 12, a configuration in which the truncated cone is supported at eight points around the roller member 42, and the electrode 41 is moved in the vertical direction by moving the roller in the horizontal direction, or the like can be considered. Secondary electron focusing electrode 41
The potential applied to the substrate may be a numerical value suitable for convergence, and may be stored in a table in advance according to the substrate to be inspected 10 or may be input manually. Further, in the present embodiment, the potential contrast enhanced image is used alone. However, a high accuracy shape contrast is obtained in the neighboring cells, and the potential contrast enhanced image is added or subtracted to obtain a true potential contrast image. There may be. Alternatively, a method may be used in which a position where a defect is detected in the potential contrast emphasis mode is stored, a normal inspection is performed again only at that position, and an image is stored. Further, in the embodiment, the electron beam is widened and the high-speed scanning is performed by that amount. However, as shown in FIG. 13, the scanning is performed so that the adjacent beam irradiation positions overlap without increasing the scanning speed, and the obtained signal value is obtained. May be used as is or by averaging to obtain a highly accurate potential contrast enhanced image. The method of capturing secondary electrons is not limited to the reflection plate method, but may be a method of directly capturing secondary electrons. Of course, the secondary electrons may be directly sucked while being configured with the reflection plate, or the operation may be performed so that the capture method can be selected according to the inspection mode. Further, an operation of changing the voltage of the secondary electron detector to a desired value according to the inspection mode may be performed. Further, in the present embodiment, a negative high voltage is applied to the substrate to be inspected, and a retarding electric field is formed between the substrate and the ground electrode. However, other structures may be used as long as the retarding electric field can be formed. The operation condition control and selection means may be a means for manually inputting and adjusting a part or all of the operation conditions. The numerical values described in the embodiments are merely examples, and it goes without saying that the present invention is not limited to these and can be implemented.

[0031]

According to the present invention, defects of the same design pattern of a semiconductor device on a wafer in the process of manufacturing the semiconductor device can be obtained.
In the method of inspecting foreign matter, residue, and the like by an electron beam, various kinds of high-precision and quick inspection of a semiconductor wafer can be performed.

As a result, a defect which cannot be detected by the conventional device, which has occurred in the manufacturing process, can be found at an early stage, and the defect rate of the semiconductor device is reduced by feeding back to the semiconductor process, thereby improving the reliability.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an apparatus configuration according to a first embodiment.

FIG. 2 is an explanatory diagram of a semiconductor device manufacturing process flow.

FIG. 3 is a configuration explanatory view of one member used in the apparatus of the first embodiment.

FIG. 4 is an enlarged explanatory diagram of a partial configuration of the apparatus according to the first embodiment.

FIG. 5 is a configuration explanatory view of one member used in the apparatus of the first embodiment.

FIG. 6 is an explanatory diagram of a secondary electron trajectory in the device of the first embodiment.

FIG. 7 is an explanatory diagram of electron beam scanning in the apparatus according to the first embodiment.

FIG. 8 is an explanatory diagram of a secondary electron trajectory in the device of the first embodiment.

FIG. 9 is an explanatory diagram of a partial configuration and a secondary electron orbit of the first embodiment.

FIG. 10 is a partial configuration explanatory view of a second embodiment.

FIG. 11 is a diagram illustrating a partial configuration of a third embodiment.

FIG. 12 is a configuration explanatory view of one member in another embodiment.

FIG. 13 is an explanatory diagram of electron beam scanning in another embodiment.

FIG. 14 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 1: electron gun 2 extraction electrode 3: condenser lens 4: blanking deflector 5: scanning deflector 6: aperture 7: shield pipe 8: EXB deflector 9: objective lens 10: substrate to be inspected 11: XY stage 12: Rotating stage 13: Secondary electron detector 14: Suction electrode 15: Pre-irradiation electron gun 16: Pre-irradiation lens 17: Pre-irradiation deflector 21: Preamplifier 22: AD converter 23: Optical sample height measuring instrument 24: Length monitor for position monitor 30a, b: Image storage unit 31: Delay circuit 32: Monitor 33: Operation unit 34: Defect judgment unit 35: Correction control circuit 36: Inspection mode selection switch 40: Ground electrode 41: Secondary Electron focusing electrode 42: Roller member 43: Pre-irradiation stage 51: Electron gun power supply 52: Extraction electrode power supply 53: Scan signal generator 54: ExB deflector power supply system 55: Objective lens power supply 57: Secondary electron focusing electrode power supply 58 : Applied voltage power supply for substrate to be inspected 101: Electronic optical system 102: Sample chamber 103: Control unit 104: Image processing system 105: Pre-irradiation chamber 201: Primary electron 202: The first secondary electron 203: second secondary electron 300: reflector 301: preliminary irradiation chamber 302: pre-irradiation electron beam.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hisaya Murakoshi 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. Central Research Laboratory (72) Inventor Kaoru Umemura 1-280 Higashi Koigakubo, Kokubunji, Tokyo, Japan Inside the Central Research Laboratory of Hitachi, Ltd. 72) Inventor Yasuteru Usami 882 Ma, Hitachinaka-shi, Ibaraki Pref., Hitachi, Ltd.Measurement Instruments Business Division Inventor Katsuhiro Kuroda Tokoi, Kokubunji, Tokyo Kubo chome 280 address Hitachi, Ltd. center within the Institute

Claims (15)

[Claims] An electron gun for generating a primary electron beam, a lens means for converging the electron beam, a deflecting means for scanning the electron beam with a substrate, a sample stage for holding the substrate, a deceleration means for decelerating the primary electron beam An electron beam accelerating / decelerating means for changing a speed of a first secondary electron secondaryly generated from the substrate by the primary electron beam; and For the secondary electron, an electromagnetic field that produces a deflection action by superposing an electric field and a magnetic field is generated
EXB deflecting means, a solid piece that collides with the secondary electrons,
A detector for detecting a second secondary electron generated from the solid piece; a means for imaging a second secondary electron signal obtained by the detector; and an image of the area and an image of another area. In a circuit pattern inspection device including a signal processing system for comparative evaluation,
A converging electrode for converging the secondary electrons inside the accelerating / decelerating means, a selecting means for selectively changing a voltage and a current value applied to the accelerating / decelerating means and the secondary electron converging electrode, and the selecting means Control means for changing and setting all or part of the voltages and signals applied to the primary electron beam acceleration voltage, the lens means, the deflecting means, and the EXB deflecting means to desired values. A circuit pattern inspection apparatus having an inspection function selectively using a shape contrast image and a potential contrast image. 2. The circuit pattern inspection apparatus according to claim 1, wherein said first solid piece for secondary electron collision is made of a material having at least two types of secondary electron generation efficiencies. Circuit pattern inspection device. 3. An electron gun for generating a primary electron beam, a lens means for converging the electron beam, a deflection system for scanning the electron beam on one area of a substrate having a circuit pattern, and a deceleration system for decelerating the primary electron beam. Electron beam acceleration / deceleration means for accelerating secondary electrons secondary generated from the substrate by the primary electron beam,
EXB deflecting means for generating an electromagnetic field that cancels the amount of deflection due to an electric field and a magnetic field with respect to the primary electron beam and generates a deflection action by superimposing the electric field and the magnetic field with respect to the secondary electron; Circuit pattern inspection configured to include a detector for detecting an image, a means for imaging a secondary electron signal obtained by the detector, and a signal processing system for comparing and evaluating an image in the area with an image in another area. In the apparatus, an electrode for changing the position inside the acceleration / deceleration means on the substrate and converging the secondary electrons, and the acceleration / deceleration means and the secondary Selecting means for selectively changing the voltage and current applied to the electron focusing electrode; and applying the accelerating voltage of the primary electron beam, the lens means, the deflection system, and the EXB deflection means in conjunction with the selection means. Voltage and signal Control means for changing and setting all or a part of the position of the secondary electron focusing electrode to a desired value, and having a function of performing an inspection selectively using a shape contrast image and a potential contrast image. Circuit pattern inspection apparatus. 4. A circuit pattern inspection apparatus according to claim 1, further comprising another electron beam source for previously irradiating an area of the substrate before the primary electron beam scans the area. Pattern inspection device. 5. The circuit pattern inspection apparatus according to claim 1, wherein said secondary electron focusing electrode is applied at substantially the same potential as said substrate. 6. The circuit pattern inspection apparatus according to claim 1, wherein the secondary electron focusing electrode has a shape of a rotary body similar to a hollow truncated cone with the central axis of the primary electron beam as an axis. Circuit pattern inspection equipment. 7. The circuit pattern inspection apparatus according to claim 1, wherein said control means can control a voltage applied to said secondary electron detector and a gain of said secondary electron signal. Inspection equipment. 8. An electron gun for generating a primary electron beam, a lens means for converging the electron beam, a deflection system for scanning the electron beam on an area of a sample, and a deceleration device for decelerating the primary electron beam. Electron beam acceleration / deceleration means for accelerating secondary electrons secondary from the sample, and canceling the amount of deflection due to an electric field and a magnetic field for the primary electron beam and an electric field and a magnetic field for the secondary electron EXB deflecting means for generating an electromagnetic field exerting a deflecting action by superimposing, a detector for detecting the secondary electrons, and a sample observation apparatus having means for imaging a secondary electron signal obtained by the detector. A sample observation apparatus, comprising: an electrode provided on the sample inside the acceleration / deceleration means for focusing the secondary electrons, wherein the secondary electron focusing electrode is variable in position and applied voltage. . 9. A step of scanning the first and second regions of the substrate on which a circuit pattern is formed with a primary electron beam, the step of converging the primary electron beam, the step of decelerating the primary electron beam, and the step of decelerating the primary electron beam. An acceleration / deceleration step of accelerating a first secondary electron secondaryly generated from the region, and an amount of deflection of the primary electron beam due to an electric field and a magnetic field canceling the first secondary electron. A deflecting step of generating an electromagnetic field having a deflecting action by superposition of an electric field and a magnetic field, a step of applying the first secondary electron to a solid piece to generate a second secondary electron, Detecting a signal of a secondary electron; obtaining an image of the region from the detected signal;
A step of comparing the image of the area with the image of the second area, and a step of determining a defect of the circuit pattern based on the comparison result.
Converging the first secondary electrons simultaneously with the acceleration / deceleration step on the substrate; operating voltages and current values of the acceleration / deceleration step and the secondary electron convergence step according to the type and processing step of the substrate A selection step of selectively changing the operating voltage and all or a part of the operating voltage and signals of the acceleration voltage of the primary electron beam, the convergence step, the deflection step, and the EXB deflection step in conjunction with the selection step. A circuit pattern inspection method, comprising: a control step of changing and setting a value, and performing an inspection selectively using a shape contrast image and a potential contrast image. 10. The circuit pattern inspection method according to claim 9, wherein the second secondary electron generation step comprises forming the solid pieces from two or more materials having different secondary electron generation efficiencies. A step of changing the number of generated second secondary electrons according to the secondary electron orbit. 11. A first substrate on which a circuit pattern is formed.
Scanning a second region with a primary electron beam, accelerating and decelerating the primary electron beam to accelerate secondary electrons generated secondary from the region by the primary electron beam, A deflection process in which the amount of deflection due to an electric field and a magnetic field is canceled for an electron beam, and an electromagnetic field that exerts a deflection action by superimposing the electric field and the magnetic field on the secondary electrons is generated. A detecting step, a step of obtaining an image of the area from the detected signal, a step of comparing the image of the first area and the image of the second area, and determining a defect of the circuit pattern from the comparison result. A circuit pattern inspection method, comprising the steps of: converging the first secondary electrons on the substrate at the same time as the acceleration / deceleration step; and accelerating / decelerating the substrate according to the type and processing step of the substrate. Process and above A selection step of selectively changing an operating voltage and a current value of a secondary electron convergence step; an acceleration voltage of the primary electron beam in conjunction with the selection step; and an operating voltage of the convergence step, the deflection step, and the EXB deflection step. And a control step of changing and setting all or a part of the signal to a desired value, and performing an inspection selectively using the shape contrast image and the potential contrast image. . 12. The circuit pattern inspection apparatus according to claim 9, wherein another electron beam is irradiated before the primary electron beam scans the first or second region of the substrate. A circuit pattern inspection method, comprising: 13. The circuit pattern inspection apparatus according to claim 9, wherein the selecting step increases the scanning speed in the scanning step when the beam diameter of the primary electron beam is large. A circuit pattern inspection method characterized by a step of reducing the scanning speed when the diameter is small. 14. The circuit pattern inspection apparatus according to claim 9, wherein in the image signal acquiring step, when the beam diameter of the primary electron beam is large, the positions of the adjacent primary electron beam irradiation positions are different. A circuit pattern inspection method, wherein the secondary electron signal is subjected to arithmetic processing, and when the beam diameter is small, the secondary electron signal at the primary electron beam irradiation position is used as it is. 15. A system comprising: means for accelerating secondary electrons from a substrate having a pattern; a reflector for amplifying and separating the secondary electrons; and a detector for detecting secondary electrons from the reflector. Inspection equipment using the characteristic electron beam.