JP2005135611A - Complex type charged particle beam device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a complex type charged particle beam device capable of obtaining necessary detection signals in both detection units, by balancing the influence that retracting electric fields for detecting secondary ions and secondary electrons with different charges have upon each other. <P>SOLUTION: The complex type charged particle beam device installed with both a secondary ion detecting unit 2 and a secondary electron detecting unit 1 is provided with a means for detecting detection signal levels of the secondary ion detecting unit 2 and the secondary electron detecting unit 1 so as to be able to obtain at the same time in good balance signals of the both units 2, 1, and a means equipped with an impression voltage varying means 6 at retracting electrodes 3n, 3p of the secondary ion detecting units 2 and the secondary electron detecting unit 1 for controlling the impression voltage varying means 6 based on the detection signal levels. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a system in which a focused ion beam (FIB) apparatus and an electron microscope (SEM) are combined, and has fine processing and observation functions.

  An FIB apparatus is used for correcting a black defect (attachment defect) or white defect (missing defect) in a semiconductor photomask, processing a sample with a transmission electron microscope (TEM), or manufacturing a fine structure. This FIB apparatus has a processing function such as sputter etching by FIB, gas assist etching using volatile gas, and CVD for processing by injecting raw material gas, as well as secondary charge released from the sample surface due to ion irradiation. It has an analysis function by detecting particles and a function as a scanning microscope. Although the FIB apparatus has used the function of a scanning ion microscope to observe the state of processing by the FIB, the FIB irradiation direction used for processing is different from the FIB irradiation direction for observation. Once processing is interrupted and the sample stage is tilted, FIB scanning for observation is performed, and the original angle is returned again to perform further processing. Due to this, there are problems such as loss of time, tilting of the irradiation position by tilting, and damage to the sample surface by irradiating the FIB for observation. Is equipped with an electron microscope (SEM) for observation in this FIB device, and SEM observation in real time without tilting the sample stage in the course of FIB processing by the SEM column installed at an angle different from that of the FIB column A possible device is presented.

Patent Document 1 aims to provide a processing observation apparatus and a sample processing method capable of controlling FIB processing while confirming a cross-sectional state of a sample processed by an FIB apparatus, and the configuration is processed by the FIB. In order to observe the processed cross section of the sample inside with a scanning electron microscope (SEM), the optical axis of the electron optical system of the SEM is arranged perpendicular to the optical axis of the ion optical system of the FIB apparatus, and the stage mechanism is driven. The axis was set perpendicular to both the optical axis of the ion optical system and the optical axis of the electron optical system. In addition, in order to monitor the state of the submicron minute part in the processing cross section during the FIB processing at the same time as the processing, a signal detector is provided in each of the FIB apparatus and the SEM, and each apparatus has a beam for displaying an image. By providing a scanning control circuit and an image display control circuit, simultaneous observation with an FIB apparatus and an SEM is possible at independent magnifications. In order to obtain a clear image with each device, the FIB device can detect and display an ion image and a secondary electron image, and the SEM can detect and display a secondary electron image and a reflected electron image. When the ion image is detected by the FIB apparatus, the pull-in voltage of the detector is set to be negative, and when the secondary electron image is detected, the pull-in voltage is set to be positive. Further, when the secondary electron image is detected by the SEM, the detector pull-in voltage is set to a positive value, and to detect the reflected electron image, the detector pull-in voltage is set to zero. This apparatus is provided with a detector of the FIB apparatus and a detector of the SEM apparatus, respectively, and discriminates charged particles to be detected by switching the pull-in voltage of the detector. However, when the secondary ion is detected by one detector and the secondary electron is detected by the other detector, the electric field (+) for detecting the negatively charged secondary electron and the positively charged secondary electron are detected. Since the attracting electric field (−) for detecting ions acts as a force to pull back to the sample direction to secondary charged particles (secondary electrons, secondary ions) of the same polarity, if one electric field is too strong, the other This causes a problem that the input of secondary charged particles to the detector is suppressed and the resulting image becomes dark.
JP 2001-84951 A "Processing observation apparatus and sample processing method" published on March 30, 2001 Paragraphs [0005] [0008] [0005] [0005]

  The problem to be solved by the present invention is to balance the influence of the attracting electric field for detecting secondary ions and secondary electrons having different charges on each other, and obtain necessary detection signals in both detectors. An object of the present invention is to provide a composite charged particle beam apparatus.

  The composite charged particle beam apparatus of the present invention is a composite charged particle beam apparatus provided with a secondary ion detector and a secondary electron detector, wherein the signals of the secondary ion detector and the secondary electron detector are received. Means for detecting the detection signal level of the secondary ion detector and the secondary electron detector so as to obtain a good balance at the same time, and an applied voltage variable means for the lead-in electrode of the secondary ion detector and the secondary electron detector And a means for controlling the applied voltage varying means based on the detection signal level.

  In addition, another composite charged particle beam device of the present invention is a composite charged particle beam device provided with a secondary ion detector and a secondary electron detector, the secondary ion detector and the secondary electron detector. Means for detecting the detection signal level of the secondary ion detector and the secondary electron detector so that the signal of the detector can be obtained in a balanced manner at the same time, and a voltage applied in front of the secondary ion detector and the secondary electron detector. A lead-in electrode provided with a variable means is arranged, and a means for controlling the applied voltage variable means based on the detection signal level is provided.

  Further, the composite charged particle beam apparatus of the present invention is applied to the sample stage so as to adjust the potential of the sample surface as an electric field adjusting means provided between the secondary ion detector and the drawing electrode of the secondary electron detector and the sample surface. The thing provided with the applied voltage variable means is presented.

  The composite charged particle beam apparatus of the present invention is applied to means for detecting the detection signal level of the secondary ion detector and the secondary electron detector, and applied to the lead-in electrodes of the secondary ion detector and the secondary electron detector. The voltage variable means is provided, and the means for controlling the applied voltage variable means based on the detection signal level is provided, so that the pull-in voltage of the detector is adjusted according to each detection signal level. The number of charged particles to be detected can be adjusted by this feedback system, and the signals of the secondary ion detector and the secondary electron detector can be simultaneously obtained in a balanced manner.

  In another composite charged particle beam apparatus according to the present invention, a secondary ion detector and a lead-in electrode provided with variable applied voltage means are arranged in front of the secondary electron detector and based on the detection signal level. And means for controlling the applied voltage varying means, so that not only can the signals of the secondary ion detector and the secondary electron detector be obtained in a balanced manner at the same time, but also a high voltage independent of the drawing electric field. Particles can be incident on the stage detection system with energy that provides optimum detection efficiency.

  The composite charged particle beam apparatus of the present invention uses a secondary ion detector signal as a scanning ion microscope image, and also uses a secondary electron detector signal as a scanning electron microscope image. Secondary electron images can also be clearly obtained.

  When the sample surface is irradiated with a charged particle beam such as an ion beam or an electron beam, the irradiated charged particles are reflected, the irradiated charged particles are injected into the sample, or secondary ions or secondary electrons are emitted. It is well known that occurs. When the sample surface is irradiated with an electron beam, reflected electrons reflected on the sample surface and secondary electrons emitted from the sample are mixed as shown in FIG. In the case of reflected electrons, the energy is almost equal to the energy of the irradiated primary electron beam, whereas the secondary electrons are several eV to several tens eV, and the former is scattered from the irradiation point in all directions. However, the latter becomes floating in the vicinity of the sample surface. The secondary electron detector having a negative charge is sucked by the drawing electrode showing an anodic property and taken into the detector. FIG. 4 shows a typical example of this secondary electron detector. A guides secondary electrons to a scintillator, generates photons, sequentially increases secondary electrons in a subsequent photomultiplier tube, and reaches an output electrode. . In the case of B, the secondary electrons sucked by the drawing electrode are taken into the microchannel plate at the subsequent stage. This microchannel plate is a bundle of hollow pipes having a diameter of 10 to several tens of micrometers having a secondary electron amplification function, and amplifies the captured electrons while accelerating in the longitudinal direction of the pipe. Compared with the device A, the timing characteristics (time resolution) are excellent, but there is also a defect accompanied by deterioration when used for a long time.

When the sample surface is irradiated with an ion beam, as shown in FIG. 3, secondary ions and secondary electrons emitted from the sample are mixed on the sample surface. Typical example used as an ion beam, when an ion beam using liquid Ga as an ion source is irradiated on the sample surface with an acceleration voltage of 30 kV, the number of secondary ions / number of secondary electrons = 1/10 to 1 / 20 The charge of secondary electrons is of course a negative charge, but the secondary ions in this case usually have a large number of positive charges. An example of this secondary ion detector is shown in FIG. In the example illustrated in A, the secondary ions attracted by the drawing electrode are taken into the ion-electron conversion electrode in the next stage and discharge secondary electrons. The secondary electrons emitted here are sent to the photomultiplier tube through the scintillator, and are sequentially amplified for each reflection from photons to electrons. In the example shown in B, the secondary ions attracted by the drawing electrode are taken into the channeltron of the next stage. In this channeltron, a semiconductor film having a secondary electron gain is attached to the inner surface of a spiral glass tube, a voltage of several kV is applied to both ends of the tube, and the number of electrons incident from the mouth of the negative voltage side tube is 10 ⁵ to It acts as a kind of secondary electron multiplier that emits 10 ⁷ times from the positive voltage side. It is also possible to perform mass analysis of a sample by using a mass analyzer as an ion detector.

  A typical example in which the present invention is applied to an FIB apparatus will be described with reference to FIG. A focused ion beam is irradiated onto the sample surface from the FIB column, secondary electrons emitted from the sample are attracted to the drawing electrode 3p applied to a positive potential, and secondary ions are drawn to a negative potential. It is sucked into the electrode 3n and detected by each detection mechanism. The secondary electron signals and secondary ion signals detected by the detectors 1 and 2 are respectively compared with the level detection unit 4 reference value, and depending on the level, the level of the level of each of the lead-in electrodes 3p and 3n. Applied voltage variable means 6 for adjusting the applied voltage is provided. The secondary electron detector 1, the secondary ion detector 2, and the sample are provided in the vacuum chamber 5. The electric field generated between the sample surface and the lead electrodes 3p and 3n of the detectors 1 and 2 is the potential applied to the lead electrode 3p of the secondary electron detector and the potential applied to the lead electrode 3n of the secondary ion detector. Both electric fields act in the direction of weakening each other's electric field. When the negative electric field for attracting the secondary ions is too strong, the secondary electrons repel and it is difficult to reach the secondary electron detector 1. On the contrary, when the positive electric field for attracting the secondary electrons is too strong, the secondary ions are repelled and hardly reach the secondary ion detector 2. Therefore, in the present invention, the detection signal level of each detector is monitored, and when either level is larger or smaller than the reference value, the applied voltage of each drawing electrode is changed according to the magnitude of the level. Adjust by. When the detected secondary ion signal is used for a scanning ion microscope image and the detected secondary electron signal is used for a scanning electron microscope image, when one of the images is dark, the darker detection amount is small. The electric field is strengthened by adjusting the potential of the lead electrode of the other detector, or the electric field is weakened by adjusting the potential of the lead electrode of the other detector. As a result, the detection amount of each charged particle is feedback adjusted. As an adjustment method, what is compared with the reference value is shown. However, the method of manually adjusting the applied voltage variable means by observing the ion image and the electronic image on the display is also possible to set and fix one applied voltage variable means from the luminance signal. There is also a method of adjusting the other applied voltage variable means.

  In addition, the electric field adjustment means provided between the secondary ion detector and the lead-in electrode of the secondary electron detector and the sample surface is the one with a built-in detector before the secondary ion detector and the secondary electron detector. There is also a mode in which a lead-in electrode is separately provided and an applied voltage variable means is provided thereon.

  In this device, the secondary electron image and the scanned ion image are viewed from the same angle, but the secondary electrons and secondary ions not only have different polarities, but can also obtain different sample information at the irradiation position. Therefore, it is possible to collect more abundant information about the sample by comparing.

  An example in which the present invention is applied to a FIB / SEM combined apparatus will be described with reference to FIG. This composite apparatus is installed so that the FIB column and the SEM column are irradiated with beams from different directions with respect to the sample surface, and the secondary ion detector 2 and the secondary electron detector 1 are located near the irradiation spot. Is placed. In the figure, the secondary ion detector 2 and the secondary electron detector 1 are depicted as being arranged side by side for two-dimensional expression, but in actuality, they are arranged at positions that oppose each other by 180 °. Is desirable. This is because, as described above, the electric charges of both charged particles are opposite to each other, and a simple electric field can be formed when the electric field that draws them is arranged at a position opposite to 180 °.

  In this apparatus, for example, there is a case in which FIB is irradiated from above the sample surface and the processed region is desired to be observed in real time with an SEM image during the etching process. FIB is irradiated to the sample surface for etching processing. At that time, secondary ions are emitted from the sample surface, and the secondary ion detector 2 detects them to obtain an ion image. Further, the processing state is observed while detecting and processing an SEM image by detecting secondary electrons emitted from the electron beam irradiated from different angles. In order to obtain a secondary ion image by FIB irradiation and a secondary electron image by electron beam irradiation in a well-balanced manner, in this embodiment, each charged particle detection signal level is compared with a reference value to each drawing electrode not shown. Is adjusted so that both good images can be obtained. In addition, with FIB irradiation, the emitted secondary electron exists and it becomes the noise of the SEM image which is a visual field from a different angle. Basically, the secondary electron detector 2 cannot discriminate and detect both secondary electrons, but in order to increase the S / N ratio of the SEM image, the secondary electron emitted from the FIB is used as an electron beam. The primary electron beam current is increased to increase the number of secondary electrons emitted by.

  An example in which the present invention is applied to an FIB apparatus equipped with an electron gun for reducing charge will be described with reference to FIG. While FIB deposition processing is performed by sputter etching, gas assist etching, and injection of raw material gas by the FIB apparatus, a phenomenon occurs in which ionic charges are accumulated on the surface of the sample and become charged. In such a state, the FIB repels the electric charge and causes an irradiation position shift, so that accurate processing cannot be performed. In order to avoid this phenomenon, the FIB apparatus may be provided with an electron gun for relaxing charging. Originally, the electron gun for relaxing charging is irradiated in the form of an electron shower in order to neutralize the electric charge charged on the sample surface, but a secondary electron observation image can also be obtained by this electron irradiation. However, since it is an electron beam for relieving charging, the beam diameter is not reduced as in SEM and the resolution is low, but the approximate irradiation position can be monitored. Also in this case, in order to obtain a secondary ion image by FIB irradiation and a secondary electron image by electron beam irradiation in a well-balanced manner, in this embodiment, each charged particle detection signal level is compared with a reference value to each drawing electrode. Is adjusted so that both good images can be obtained.

  An example in which the present invention is applied to an ion beam apparatus using a gas discharge ion source and an SEM combined apparatus will be described with reference to FIG. There has been proposed an ion beam apparatus that uses an inert gas such as argon gas as an ion source to perform microfabrication, analysis, or measurement without contaminating a minute region on the surface of a sample such as a semiconductor. The present invention can also be applied to such an ion beam apparatus and SEM combined apparatus. In order to obtain a secondary ion image by ion irradiation and a secondary electron image by electron beam irradiation in a well-balanced manner, in this embodiment, each charged particle detection signal level is compared with a reference value, and the applied voltage to each drawing electrode is set. Adjust so that both good images are obtained.

  An example in which the present invention is applied to an ion beam apparatus using a gas discharge ion source equipped with a charge relaxation electron gun will be described with reference to FIG. This apparatus is substantially the same as the embodiment shown in FIG. 7, and uses an ion beam apparatus using a gas discharge ion source such as an inert gas instead of the liquid gallium ion source. Also in the present embodiment, each charged particle detection signal level is compared with a reference value to adjust the voltage applied to each drawing electrode, so that both good images can be obtained.

  An example in which the present invention is applied to a combined apparatus of an FIB apparatus and an SEM equipped with an in-lens secondary electron detector will be described with reference to FIG. In this embodiment, the drawing electrode 3p is arranged at the sample side tip of the SEM column, and the applied voltage variable means 6 is provided on the drawing electrode 3p and the drawing electrode (not shown) of the secondary ion detector 2, respectively. The detection signal level of the ions and the detection signal level of the secondary electrons are compared with the reference value, the applied voltage to each drawing electrode is adjusted, and adjustment is performed so that both good images are obtained.

  A modification in which the present invention is applied to a combined apparatus of an FIB apparatus and an SEM equipped with an in-lens secondary electron detector will be described with reference to FIG. In this embodiment, instead of adjusting the potential of the lead-in electrode at the sample side tip of the SEM column, the potential of the sample surface is adjusted by the applied voltage varying means 6 provided on the sample stage, and the secondary ion detector 2 An applied voltage variable means is provided on a lead-in electrode (not shown) to adjust the potential. When the potential on the sample surface becomes a negative charge, secondary electrons repel and are drawn into the SEM column, and secondary ions are differently charged and are easily adsorbed on the sample surface. If the potential of the electrode is lower, it is drawn into the secondary ion detector 2. The detection signal level of the secondary ions and the detection signal level of the secondary electrons are compared with the reference value, the applied voltage to each drawing electrode is adjusted, and adjustment is performed so that both good images can be obtained.

It is a figure which shows the basic composition of this invention which adjusts the signal level of a secondary ion detection signal and a secondary electron detection signal appropriately in a FIB apparatus. It is a figure explaining the emission phenomenon of the reflected electron and secondary electron by electron beam irradiation. It is a figure explaining the discharge | release phenomenon of the secondary ion and secondary electron by ion beam irradiation. It is a figure which shows the typical structure of a secondary electron detector. It is a figure which shows the typical structure of a secondary ion detector. It is a figure which shows the Example which applied this invention to FIB and SEM compound apparatus. It is a figure which shows the Example which applied this invention to the FIB apparatus provided with the electron gun for charge relaxation. It is a figure which shows the Example which applied this invention to the compound apparatus of a gaseous ion source ion beam apparatus and SEM. It is a figure which shows the Example which applied this invention to the gas ion source ion beam apparatus provided with the electron gun for charge relaxation. It is a figure which shows the Example which applied this invention to the composite apparatus of FIB apparatus and the secondary electron detector type | mold SEM in a lens. It is a figure which shows the modification which applied this invention to the composite apparatus of FIB apparatus and the secondary electron detector type | mold SEM in a lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Secondary electron detector 5 Chamber 2 Secondary ion detector 6 Applied voltage variable means 3p, 3n Lead-in electrode 4 Level detector

Claims (5)

  A combined charged particle beam apparatus provided with a secondary ion detector and a secondary electron detector, wherein the secondary ion detector and a means for detecting a detection signal level of the secondary electron detector, and the secondary ion An electric field adjusting means is provided between the drawing electrode of the detector and the secondary electron detector and the sample surface, and a means for controlling the electric field adjusting means based on the detection signal level. A combined charged particle beam device characterized in that the electric field between the secondary electron detector and the sample surface is adjusted so that both detection signals can be obtained in good balance simultaneously.   The electric field adjustment means provided between the secondary ion detector and the lead-in electrode of the secondary electron detector and the sample surface is provided with a variable applied voltage means on the lead-in electrode of the secondary ion detector and the secondary electron detector. The composite charged particle beam apparatus according to claim 1, which is an apparatus.   The electric field adjusting means provided between the secondary ion detector and the lead-in electrode of the secondary electron detector and the sample surface is applied to the lead-in electrode separately provided in front of the secondary ion detector and the secondary electron detector. The composite charged particle beam apparatus according to claim 1, wherein a variable means is provided.   The electric field adjusting means provided between the lead-in electrode of the secondary ion detector and the secondary electron detector and the sample surface is one in which an applied voltage variable means is provided on the sample stage so as to adjust the potential of the sample surface. The composite charged particle beam apparatus according to claim 1.   5. The combined charge according to claim 1, wherein the secondary ion detector signal is used as a scanning ion microscope image, and the secondary electron detector signal is used as a scanning electron microscope image. Particle beam device.

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