JP4134951B2 - Sample preparation equipment - Google Patents

Description

  The present invention relates to a micro sample preparation apparatus for extracting a sample piece including a desired specific region from a semiconductor wafer or device chip using an ion beam, and making a sample piece for micro region analysis or measurement.

  As a sample preparation device that facilitates the preparation of micro sample pieces for use in analyzers, a device that extracts micro samples on the order of several μm to several tens of μm from a sample substrate by combining focused ion beam (hereinafter abbreviated as FIB) processing and micromanipulation technology. Has been devised. This technique is disclosed in Japanese Patent Laid-Open No. 5-52721 (Known Example 1). In this known example 1, the probe tip positioning method is not specified, but from the example, the probe tip position is identified by a scanning ion microscope image (Scanning Ion Microscope, SIM image) by ion beam scanning and secondary electron detection. It is thought that there is.

JP-A-5-52721

  When automating the above-described sample preparation apparatus, a technique for automatically identifying the probe tip position is required. However, in the above conventional method (known example 1), it is considered that the operator uses the SIM image to determine the tip of the probe, and in this case, the apparatus cannot be automated. A method of identifying a probe tip by pattern recognition using a SIM image is also conceivable, but has the following problems.

  Depending on the sample surface structure (material), there may be a region with the same brightness as the probe in the SIM image, so the probe boundary may become unclear and the tip identification may be difficult. In addition, the probe shape may change due to foreign matter adsorption or ion beam irradiation on the probe, which may make verification by pattern recognition difficult. Also, an expensive pattern recognition device is required to increase the accuracy of pattern recognition.

  An object of the present invention is to provide a sample preparation device that can reliably and easily realize probe tip positioning suitable for automation.

  In order to achieve the above object, a sample preparation apparatus of the present invention is a sample preparation apparatus using ion beam processing, a technique for conveying a sample piece using a probe, and a technique for fixing a sample piece to a sample piece holder. The current flowing into the probe for transporting the sample piece is synchronized with the scanning signal of a charged particle beam such as an ion beam or an electron beam and converted into data, thereby facilitating identification of the probe tip position.

  According to the present invention, it is possible to produce a micro sample piece that can be directly introduced into an analysis apparatus from an integrated circuit chip or a semiconductor wafer without human manual work. In particular, since the probe tip can be easily positioned and is suitable for automation, the sample piece for analysis can be easily and reliably produced at high speed.

  A micro sample preparation apparatus according to the present invention includes a movable sample stage on which a substrate such as a semiconductor wafer or a semiconductor chip is placed, a probe that is brought into contact with the vicinity of the analysis position of the substrate, and a probe driving unit that drives the probe independently of the sample stage A manipulator driving device for controlling the probe driving means to suppress the substrate damage and making probe contact, a probe current detecting device for detecting a current flowing into the probe, and a means for connecting the probe and the substrate near the analysis position An ion beam optical system that irradiates an ion beam in the vicinity of the analysis position of the substrate and forms a sample piece including the analysis position of the substrate; means for holding a sample piece holder on which the sample piece is placed; and a sample piece And means for fixing the sample piece holder, and means for separating the probe and the sample piece.

Moreover, as a more preferable embodiment of the sample preparation apparatus of the present invention, there is the following configuration.
(1) The tip position is identified by recognizing the probe shape from a signal synchronized with the probe inflow current detected by the probe current detector and the scanning of the ion beam.
(2) In the probe current detection device, if the probe inflow current is binarized with an appropriate threshold value and the tip position is identified, the tip can be positioned more easily.

  FIG. 1 is a configuration block diagram showing an embodiment of a sample preparation apparatus according to the present invention. The sample preparation device includes a movable sample table 3 on which a substrate 2 such as a semiconductor wafer or a semiconductor chip is placed, and a sample position control device 9 that controls the position of the sample table 3 in order to specify the position of the substrate 2 to be analyzed. The probe 11 is moved to the vicinity of the analysis position of the substrate 2, the probe driving means 4 that drives the probe 11 independently of the sample stage 3, and the ion beam 13 is irradiated to the vicinity of the analysis position of the substrate 2 to analyze the substrate 2. An ion beam optical system 1 that forms a sample piece including a position, and a secondary electron detector 12 that constitutes observation means for detecting secondary electrons and observing the vicinity of the substrate 2, the probe 11 or the sample piece holder 19 And a deposition gas source 8 for supplying ion beam assisted deposition gas.

  The deposition gas source 8 constitutes a fixed connection means for connecting the distal end of the probe 11 and the vicinity of the analysis position of the substrate 2 or fixing the sample piece and the sample piece holder 19. The sample stage 3 has a holder holder 20 for placing a sample piece holder 19 for fixing the separated and extracted sample piece. The driving device 7, the deposition gas source control device 8 ′, the sample position control device 9, the display device 5, the manipulator driving device 4 ′ and the like of the ion beam optical system 1 are controlled by the central processing device 6. Here, 10 in the ion beam optical system 1 is a deflector. The probe 11 and the probe driving means 4 constitute a manipulator. The preamplifier 32 amplifies the inflow (outflow) current of the probe 11 and sends it to the central processing unit 6.

  By using this apparatus, a sample piece (not shown) is extracted from the substrate 2 by ion beam processing, the sample piece is transported by a manipulator including the probe 11 and its driving means 4, and the sample piece is transferred to the holder 19. A micro sample preparation operation for an analyzer, such as fixation, can be performed reliably and easily.

  Details of the probe tip position identification method will be described below. A block diagram of the circuit used in this embodiment is shown in FIG.

  This block diagram corresponds to a part of the probe 11, the preamplifier 32, the manipulator driving device 4 ′, and the central processing unit 6 in FIG. The preamplifier 32 amplifies the inflow current Ip31 to the probe 11 and generates the image signal Sp33 of the probe shape information generation circuit 35. As the scanning signal of the probe shape information generation circuit 35, the ion beam deflection scanning signal Sd34 used for the deflector 10 of the ion beam driving device 7 of FIG. 1 is used.

  The image signal Sp33 is imaged by the probe shape information generation circuit 35 in synchronization with the scanning signal Sd. That is, Sp = 0 in a region where the ion beam is not irradiated onto the probe, and Sp ≠ 0 in a region where the ion beam is irradiated onto the probe, so that the probe shape can be extracted.

  When this information is stored in the memory 36 and displayed on the display device 37, as shown in FIG. 3, the area where the probe is not present is dark with Sp = 0 (shaded area in FIG. 3), and the area where the probe is present is Sp ≠ 0. Can be displayed as bright (white portion in FIG. 3), and the probe shape can be recognized. Further, it is possible to display the information directly from the probe shape information generation circuit 35 on the display device 37 without being taken into the memory 36 once.

Ideally, Sp = 0 in the area where the probe is not present and Sp = Sb (a constant determined by the ion beam current) ≠ 0 in the area where the probe is present. The finite ion beam diameter is not always ideal.
In such a case, the probe boundary can be extracted more reliably by binarizing and imaging the image signal Sp with an appropriate threshold value in the probe shape information generation circuit 35.

  Next, a method for obtaining the coordinates of the probe tip will be described. Here, for the sake of simplicity, description will be made on the assumption that the image signal Sp is binarized (0 and 1) as described above.

  FIG. 4A is a diagram showing the memory contents corresponding to the image of FIG. N is the number of digital divisions in the X direction visual field, and M is the number of digital divisions in the Y direction visual field. That is, this field of view is composed of N × M dots, and data coordinates are represented by (Xi, Yj) (i and j are integers). The horizontal line in each Y represents the image signal Sp, and represents 0 or 1 as shown in FIG.

  In FIG. 4A, the image signal Sp33 is 0 for all X from Y0 to Ym-1, and the image signal Sp is 1 for a certain X range from Ym to YM. Based on this information, the probe tip coordinate extraction circuit 38 extracts the tip coordinates. For example, in the case of FIG. 4 (a), the point where the X interval between the rising edge (0 → 1) and the falling edge (1 → 0) is the smallest in the image signal Sp readout from Y0 to Ym is determined as the leading edge. Ym) is the probe tip coordinate 39 (FIG. 2).

  If there is no rise and fall interval due to the probe facing sideways as shown in FIG. 5 (a) (b), FIG. 5 (c) (0 and 1 of the image signal Sp are shown in FIG. 5). If the image signal Sp is read in the X direction as in (5 (d)) and the portion where the rising and falling Y intervals are the smallest is taken out, the coordinates become the probe tip coordinates. In the unlikely event that binarization does not eliminate the noise and there is a singular point with Sp = 1 in the area other than the probe, and if the above tip position cannot be identified, the surrounding area of that dot for all dots in the memory Singularities can be eliminated by taking the average of the dots and smoothing them.

  In the case of this probe tip position identification method, unlike in the case of image pattern recognition from a SIM image in which there may be a region with the same brightness as the probe other than the probe region, current inflow to the probe is not performed outside the probe region. Therefore, the tip position can be identified with high accuracy as described above.

  If the probe tip position can be automatically identified as described above, the probe target position coordinate 41 is input as shown in the block diagram of FIG. 2, and error information Sc42 from the current probe position is obtained as a position error calculation circuit. The probe can be automatically driven to the target coordinates by driving the manipulator driving device 4 ′ calculated at 40.

  This probe tip position identification method can be used in the same manner by using an electron beam deflection scanning signal instead of the scanning signal Sd even when an electron beam optical system other than the ion beam optical system is used as an observation means. Is possible.

1 is an overall schematic configuration diagram of a micro sample extraction device according to an embodiment of the present invention. The functional block diagram for the probe tip position identification by this invention. The figure which shows the probe shape image by the probe shape information generation circuit in one Example of this invention. Explanatory drawing which shows the relationship between the memory information of probe shape information and probe tip coordinates by one Example of this invention. Explanatory drawing which shows the relationship between the memory information of probe shape information by another Example of this invention, and a probe tip coordinate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ion beam optical system, 2 ... Substrate, 3 ... Sample stand, 4 ... Probe drive means, 4 '... Manipulator drive device, 5 ... Display device, 6 ... Central processing device, 7 ... Ion beam drive device, 8 ... De Position gas source, 8 '... deposition gas source driving device, 9 ... sample position control device, 10 ... deflector, 11 ... probe, 12 ... secondary electron detector, 13 ... ion beam, 19 ... sample piece holder, 20 ...... Holder clamp, 31 ... Probe inflow current, 32 ... Preamplifier, 33 ... Image signal, 34 ... Scanning signal, 35 ... Probe shape information generation circuit, 36 ... Memory, 37 ... Display device, 38 ... Probe tip coordinate extraction circuit, 39 ... probe tip coordinates, 40 ... position error calculation circuit, 41 ... target coordinates, 42 ... error information.

Claims (3)

A sample stage on which the sample is placed;
A probe in contact with the vicinity of a desired region of the sample;
A charged particle beam optical system for irradiating the sample or probe with a charged particle beam; and
Probe current detection means for detecting current flowing into the probe;
A detector for detecting charged particles secondary to the sample and probe irradiated with the charged particle beam;
A charged particle beam apparatus comprising: a scanning signal of the charged particle beam as a scanning signal; and a means for displaying the current signal flowing into the probe without taking it into a memory. The charged particle beam apparatus according to claim 1,
The sample stage is movable;
A charged particle beam apparatus comprising means for controlling the position of the sample stage. The charged particle beam apparatus according to claim 1 or 2,
The charged particle beam optical system includes an ion beam optical system or an electron beam optical system.

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