JP2009224233A - Charged particle beam inspection apparatus and data display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charged particle beam inspection apparatus that discovers abnormal conditions due to a stage in an early stage and takes a quick countermeasure. <P>SOLUTION: In the charged particle beam inspection apparatus, a charged particle beam is irradiated while an inspected substrate arranged on a stage is continuously shifted, and an image is created based on a generated secondary signal. The apparatus includes a position monitor length measuring unit which measures a position of continuous shifts of the stage, a controlling circuit for calculating a speed from measured positions, and a display for displaying the measured positions and a time variation of the calculated speeds. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for inspecting a defect of a substrate having a fine circuit pattern such as a semiconductor device or a liquid crystal, and more particularly to an inspection apparatus using a charged particle beam and a data display method.

  Semiconductor devices such as LSI and memory are manufactured by forming a circuit pattern on a semiconductor wafer, and in the case of liquid crystal, etc., they are manufactured by forming a circuit pattern on a glass substrate. In order to improve the yield rate of the product, it is important to inspect in the middle of the manufacturing process whether it is finished in dimensions and whether there is any foreign matter or scratch. In addition, in lithography technology used when forming a circuit pattern of a semiconductor device on a semiconductor wafer, a circuit pattern is also formed on a photomask that is an original image of the circuit pattern, and whether a desired circuit pattern is formed on the photomask. An inspection is also performed.

  For inspection, an inspection device that applies optical microscope technology that inspects the substrate by irradiating light, or an electron microscope or ion beam microscope that inspects the substrate by irradiating a charged particle beam such as an electron beam or ion beam. Inspection equipment applying technology has been developed and used.

  Here, a semiconductor wafer inspection will be described as an example. A semiconductor device is manufactured by repeating a process of transferring a pattern formed on a photomask on a semiconductor wafer by lithography and etching. A charged particle beam inspection system that inspects defects present in patterns on a semiconductor wafer irradiates a semiconductor wafer with charged particle beams, detects secondary electrons and reflected electrons generated from the substrate, and images the detected signals. Detect defects. However, the size of the charged particle beam spot is much smaller than the area of the semiconductor wafer, and it takes an enormous amount of time to inspect the entire surface of one semiconductor wafer. As a countermeasure, an attempt has been made to improve the inspection time throughput by scanning the charged particle beam while continuously moving the semiconductor wafer in one direction (see, for example, Patent Document 1).

  However, since the charged particle beam inspection apparatus uses an electron beam or an ion beam, it must be housed in a sealed container in order to make the passage region vacuum, and the internal situation can be visually confirmed. Can not. In view of this, a technique has been developed in which a generated image is displayed in real time so that an error in an inspection setting parameter is detected at an early stage (see, for example, Patent Document 2).

  However, the image display only shows the inspection result, and it is not possible to know the internal situation of the apparatus, especially the movement state of the semiconductor wafer, so it is not possible to detect defects due to mechanical factors during the inspection at an early stage. It was.

JP-A-10-294345 JP 2007-147527 A

  An object of the present invention is to provide a charged particle beam inspection apparatus that can detect an abnormality caused by a stage at an early stage and can take a quick response.

  According to an embodiment of the present invention, there is provided a charged particle beam inspection apparatus that irradiates a charged particle beam while continuously moving a substrate to be inspected arranged on a stage and generates an image based on a generated secondary signal. The position monitor length measuring device that measures the position of continuous movement of the stage, the control circuit that calculates the speed from the measured position, and the temporal change in the measured position and the calculated speed are displayed. And a display.

  According to the present invention, since the operating state of the stage is displayed on the display in real time, an abnormality caused by the stage can be found at an early stage, and prompt action can be taken.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the configuration of an inspection apparatus using a charged particle beam, and the main configuration is represented by a schematic longitudinal sectional view and a functional diagram. The circuit pattern inspection apparatus 1 irradiates a substrate 7 to be inspected, which is a semiconductor wafer, with charged particles, detects secondary electrons and reflected electrons generated from the substrate 7 to be inspected, and detects defects in the substrate 7 to be inspected. It is a device to do. The circuit pattern inspection apparatus 1 includes an inspection chamber 2 in which the chamber is evacuated, and an X stage 13 and a Y stage 14 for transporting the substrate 7 to be inspected into the inspection chamber 2. The transport mechanism is omitted. Each of the X stage 13 and the Y stage 14 is measured by the position monitor length measuring device 3 such as a laser interferometer, and the position data is sent to the correction control circuit 4 in real time.

  The charged particle beam 12 generated by the charged particle source 8 in the inspection chamber 2 is focused by the condenser lens 9 and is narrowed down and irradiated onto the substrate 7 to be inspected by the objective lens 10. At this time, since the size of the spot of the charged particle beam 12 is small, the scanning deflector (not shown) scans the inspected substrate 7 in the Y direction by the width for imaging, and at the same time the X stage 13 is perpendicular to the scanning direction. Move continuously. Since secondary electrons and reflected electrons are generated from the substrate 7 to be inspected, they are detected by the detector 11, converted from analog signals to digital signals, and sent to the image processing unit 5. The image processing unit 5 forms an image from the signal detected by the detector 11. The dimension of the image in the Y direction is determined in advance in consideration of the size displayed on the display. The image formed in this way is displayed on the display of the interface 6.

  Further, the stage position data sent to the correction control circuit 4 is sent to the image processing unit 5 after arithmetic processing described later and displayed on a display (not shown).

  FIG. 2 is a screen diagram showing a layout of a screen displayed on the display of the interface 6. The screen includes a display unit 15 that displays an image of the substrate 7 to be inspected, a map diagram that schematically shows the arrangement of the semiconductor devices, and a mode switching button area 16 in which a plurality of mode switching buttons are arranged. Thus, it is possible to select a display mode desired by the operator.

  FIG. 3 is a graph showing the measurement result of the stage position. FIG. 3A shows the time displacement of the length measurement value accompanying the stage movement of the X stage that moves continuously. The horizontal axis represents time, and the vertical axis represents the length measurement value. Ideally, a straight line is desirable, but the measured value has fluctuations. FIG. 3B shows an enlarged view of a portion surrounded by a broken line in FIG. The length measurement value is not a continuous value, but an instantaneous length measurement value measured at a predetermined length measurement value sampling period. Since the measurement value sampling cycle is short, the averaged value of the instantaneous measurement value is displayed on the display in consideration of the processing capability of the microprocessor of the image processing unit 5. In the example shown in the figure, an average value for six instantaneous length measurement values is set in advance, and an average value of six instantaneous length measurement values included in the average period is calculated. This average length measurement value is set as a representative length measurement value within the averaging period.

  Next, for each averaging period, a head time ts immediately before the first instantaneous length measurement value in the average period and a monitored time tm corresponding to the representative length measurement value are obtained. The monitored time tm is the central time within the averaging period, and is defined as the product of the half of the total number of data and the length measurement sampling period plus the start time ts. The stage moving speed at the monitored time tm is expressed by the stage moving amount per unit time. The stage moving speed at the monitored time tm is the average of the difference between the average measured value at the latest monitored time and the average measured value obtained within the measured value sampling cycle before N stages (one stage before in the figure). Calculated from the conversion cycle. If the above values are obtained, the N-th next N + 1-th stage position data shown in FIG. 3B can be predicted.

  FIG. 4 is a screen diagram in which the time variation of the position of the X stage 13 is displayed on the display unit 15 shown in FIG. 2, and can be generated from the position data of the position monitor length measuring device shown in FIG. . As shown in FIG. 4, the operator can visually determine whether the movement of the X stage is linear. Further, by making the vertical axis a speed instead of a position, the reference becomes oblique to horizontal, so that the operator can further know the change in stage position.

  FIG. 5 is a screen diagram in which the time variation of the speed of the X stage 13 is displayed on the display unit 15 shown in FIG. The X stage is controlled so that the speed is constant, but slight speed unevenness occurs due to factors such as mechanical error of the drive unit and vibration. Since the operator can easily confirm visually whether or not the allowable value has been exceeded by displaying the line 17 indicating the allowable value of the speed fluctuation in FIG. You can discover and take measures.

  FIG. 6 shows the position and speed time of the X stage of the plurality of circuit pattern inspection apparatuses on the display section shown in FIG. 2 or the display section of a display device (not shown) connected to the plurality of circuit pattern inspection apparatuses. FIG. In the example of the figure, the status of the X stage of three circuit pattern inspection apparatuses A, B, and C is displayed. The time variation of the position of the X stage 13 shown in FIG. 4 is displayed on the left side of the display unit 15, and the time variation of the speed of the X stage 13 shown in FIG. 5 is displayed on the right side. As a result, the operator can monitor the status of each device, and can quickly find out which device has an abnormality and take measures. In addition, since the circuit pattern inspection apparatus and the monitoring apparatus are connected by communication means, a monitoring apparatus is installed in a process control room away from the semiconductor wafer manufacturing apparatus, and centralized management of a plurality of circuit pattern inspection apparatuses is performed. be able to. It is also possible to monitor from a remote location using a communication line such as the Internet.

  As described above, according to the present invention, since the operating state of the stage is displayed on the display in real time, an abnormality caused by the stage can be found at an early stage, and a quick response can be taken.

The longitudinal cross-sectional view which shows the structure of the test | inspection apparatus using a charged particle beam. The screen figure which shows the layout of the screen displayed on a display. The graph which shows the measurement result of a stage position. The screen figure which displayed the time fluctuation | variation of the position of X stage on the display part shown in FIG. The screen figure which displayed the time fluctuation | variation of the speed of X stage on the display part shown in FIG. The screen figure which displayed the time fluctuation | variation of the position and speed of X stage of each apparatus on the display part shown in FIG. 2, or the display part of the display connected to the some circuit pattern inspection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit pattern inspection apparatus 3 Position monitor length measuring device 4 Correction control circuit 5 Image processing part 6 Interface 7 Board to be inspected 13 X stage 14 Y stage 15 Display part

Claims (4)

  A charged particle beam inspection apparatus that irradiates a charged particle beam while continuously moving a substrate to be inspected arranged on a stage and generates an image based on a secondary signal generated from the substrate to be inspected, wherein the stage A position monitor length measuring device for measuring the position of continuous movement, a control circuit for calculating a speed from the measured position, and a temporal change in the measured position and the calculated speed. A charged particle beam inspection apparatus comprising a display.   The charged particle beam inspection apparatus according to claim 1, wherein the display displays a line indicating a permissible value of a fluctuation in speed along with the temporal change in the calculated speed.   A data display method for a charged particle beam inspection apparatus that irradiates a charged particle beam while continuously moving a substrate to be inspected placed on a stage and generates an image based on a secondary signal generated from the substrate to be inspected. Measuring a position of continuous movement of the stage, calculating a speed from the measured position, and displaying a temporal change in the measured position and the calculated speed on a display. Data display method.   4. The data display method according to claim 3, wherein the display displays a line indicating an allowable value of a fluctuation in speed together with the temporal change of the calculated speed.

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