Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/02—Details
  • H01J37/21—Means for adjusting the focus
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
  • H01J37/28—Electron or ion microscopes; Electron or ion diffraction tubes with scanning beams
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P74/00—Testing or measuring during manufacture or treatment of wafers, substrates or devices
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
  • H01J2237/21—Focus adjustment
  • H01J2237/216—Automatic focusing methods
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
  • H01J2237/248—Components associated with the control of the tube
  • H01J2237/2482—Optical means
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
  • H01J2237/26—Electron or ion microscopes
  • H01J2237/28—Scanning microscopes
  • H01J2237/2813—Scanning microscopes characterised by the application
  • H01J2237/2817—Pattern inspection

Definitions

• the present invention relates to a sample inspection apparatus, and more particularly, to a sample inspection apparatus that performs inspection of the surface of a sample such as a semiconductor wafer by using an electron beam apparatus.
• Electron beam devices which detect defects on a wafer by generating image data and detecting z-mismatches of image data from die to die on the wafer.
• an apparatus using a projection type electron optical system is also known.
• the image projection type electron beam apparatus is configured to magnify and form secondary electrons or reflected electrons emitted from the wafer surface by irradiation of a primary electron beam by a multistage lens system such as an objective lens. Since the electron beam can be uniformly irradiated to a relatively large area on the upper side, inspection can be performed with high throughput as compared with the SEM method.
• An auto focus map (AF—MAP) is created each time a wafer is loaded on the stage of the electron beam apparatus, and an electrostatic lens for focus is obtained from the stage coordinates and AF—MAP data when inspecting a sample.
• AF-MAP creation is performed as follows using the electron beam apparatus for sample inspection itself as a focus detection apparatus.
• measurement points on the wafer are set, the stage on which the wafer is placed is moved, and one measurement point is positioned below the focus detection device.
• AF-MAP is created by calculating and storing the best focus values of all measurement points.
• the AF-MAP is created using an electron beam, charge up occurs on the wafer, and the charge up adversely affects the actual sample inspection.
• An object of the present invention is to solve such problems of the conventional example.
• An electron beam apparatus that irradiates an electron beam to inspect a sample
• An optical focus value detection unit including an optical microscope and detecting a first focus value of the optical microscope corresponding to a position of the sample surface in the optical axis direction;
• Conversion means for converting the first focus value detected to a second focus value used by the electron beam apparatus at the time of inspection of the sample
• the optical focus value detection means is an autofocus control means for automatically focusing an optical microscope on the sample surface.
• the autofocus control means outputs the first focus value of the position of the focus lens of the optical microscope in the in-focus state as the first focus value
• the conversion means is the force of the autofocus control means first focus value
• An electron beam apparatus that irradiates an electron beam to inspect a sample
• a capacitance sensor for outputting a capacitance corresponding to the position of the surface of the sample in the direction of the optical axis; a conversion means for converting the detected capacitance into a focus value used at the time of inspection of the sample by the electron beam apparatus;
• the V value used at the time of sample inspection of the electron beam apparatus be a voltage applied to the focus lens of the electron beam apparatus. Furthermore, it is preferable to further include a storage unit that stores the focus value obtained by the conversion unit in association with the coordinates of the point on the sample at which the capacitance is detected.
• An electron beam apparatus that irradiates an electron beam to inspect a sample
• a surface potential sensor for detecting the position of the sample surface in the optical axis direction
• the focus value used at the time of sample inspection of the electron beam apparatus is the voltage applied to the focus lens of the electron beam apparatus. And is preferred. Furthermore, it is preferable that a storage unit be provided which stores the focus value obtained by the conversion unit in association with the coordinates of the point on the sample at which the surface potential is detected.
• the present invention is configured as described above and creates an AF-MAP without using an electron beam, the AF-MAP can be created in a relatively short time, and the force is also charge-up. There is a problem that can be achieved.
• FIG. 1 is a perspective view of a sample inspection apparatus according to a first embodiment of the present invention.
• FIG. 2 is a block diagram showing a configuration for focus map creation using an optical microscope in the sample inspection apparatus shown in FIG.
• FIG. 3 is a view showing a screen of a monitor of the PC device shown in FIG. 1, showing a screen for an operator to input when creating an autofocus map.
• FIG. 4 is a view for explaining a method for obtaining a best focus value using an optical microscope according to the present invention.
• FIG. 5 is a diagram showing a line & space pattern suitable for obtaining the best focus value and its image data (intensity).
• FIG. 6 is a flow chart showing a control procedure for creating an autofocus map in the sample inspection apparatus of the present invention.
• FIG. 7 is an external view showing an electrostatic capacitance sensor applicable to a focus map creating apparatus according to a second embodiment of the present invention.
• FIG. 1 is a perspective view of an embodiment of a sample inspection apparatus according to the present invention
• FIG. 2 is a block diagram showing a focus map creation apparatus used for the sample inspection apparatus.
• 100 is an electron beam apparatus for inspecting defects of a sample W which is a semiconductor wafer, etc.
• 1 is a PC apparatus which controls the operation of the entire focus map generating apparatus and has a monitor screen
• 2 is an auto focus (AF) controller
• 3 is an optical microscope.
• Image information from the electron beam apparatus 100 at the time of inspection of the sample W is supplied to the PC apparatus 1.
• the optical microscope 3 has an objective lens 31, a focus lens 32, a magnifying lens 33, spectroscopic prisms 34 and 35, low magnification and high magnification detection CCDs 36 and 37, and actuator actuators.
• the optical microscope 3 has an objective lens 31, a focus lens 32, a magnifying lens 33, spectroscopic prisms 34 and 35, low magnification and high magnification detection CCDs 36 and 37, and
• the autofocus control device 2 includes a motor driver 21 and an arithmetic device 22, and outputs a motor driver signal based on the contrast signal from the CCD 36 or 37, and the motor 38 (actuator not shown) is generated by the signal.
• a motor driver 21 and an arithmetic device 22
• the motor 38 is generated by the signal.
• a commercially available product can be adopted as the autofocus control device 2.
• AF-MAP autofocus map
• the operator displays an input screen as shown in FIG. 3 on the monitor of the PC device 1 and performs the following operation on the screen.
• a die pattern to be set it is preferable to adopt a pattern with high black and white contrast. Also, the black and white pattern does not necessarily have to appear periodically.
• the mode for automatically obtaining the best focus value is selected, and the focus map creation device shown in FIGS. 1 and 2 starts operation. Then, the best focus value of the die pattern position set in step b) of the die set in step a) is detected, and the best focus value for each measurement point is obtained.
• step a) the operator can also specify an arbitrary die. Settings such as selection of all dies and selection of n dies can be made. Also, the operator can select the input screen, whether it is a diagram that schematically represents the die arrangement in the wafer or an image that uses an actual image. You can choose. Furthermore, by operating the manual focus button B3, it is possible to manually set the best focus value manually using the focus switch B4 linked to the voltage value of the focusing electrode. In this case, step b) is skipped.
• Step c) is executed by the arithmetic device 22 of the autofocus control device 1 1S
• a procedure for automatically obtaining the best focus value of each measurement point in the arithmetic device 22 will be described with reference to FIG. Do.
• the focus value represents the position of the focus lens 42 on the optical axis (Z-axis)!
• the best focus value indicates the control position of the actuator 3 at that time, that is, the position on the optical axis (Z-axis) of the focus lens 42, and is 2.3 in the example of FIG.
• the contrast shows the shape if a black and white pattern is present. It can be measured regardless of.
• the best focus value obtained in the autofocus control device 2 is transmitted to the PC device 1 and stored in combination with the position coordinates of the measurement point. In this way, the best focus value is measured and stored for all measurement points.
• the best focus value is, as described above, the position on the optical axis (Z axis) of the focus lens 32 at each measurement point. Therefore, the best focus value is the Z direction of the surface of the sample W. It is a value corresponding to the position.
• the PC device 1 converts the obtained best focus value for each measurement point into a voltage (best focus voltage value) to be applied to the focus lens (electrostatic lens) of the electron beam device. This conversion process is performed as follows.
• the best focus value measured using the optical microscope shown in FIG. 1 and the voltage applied to the focus lens measured with the electron beam apparatus Assuming that voltage values are ZM and ZEB, respectively, the measured value Z of the optical microscope at another measurement point n
• ZEB can be obtained by obtaining the coefficient a and substituting the coefficient a and the best focus value (position on the Z axis) ZM obtained using the optical microscope into the equation (1).
• the positions to be measured in order to obtain the coefficient a in the above equation (1) are not one power point but a plurality of positions, and their average is determined, and the obtained average value is substituted into ZEM and ZM in the above equation. If you do
• the best focus value measured using the optical microscope shown in FIG. 1 and the voltage applied to the focusing lens measured with the electron beam apparatus are ZM and Zm respectively.
• coefficients a and b are obtained from the measurement values obtained at the first and second measurement points, and by substituting the coefficients a and b and ZM at the other measurement point n into equation (2), The ZEB of each measurement point can be obtained.
• the coefficients may be calculated by increasing the measurement position and solving the multinomial polynomial.
• the PC apparatus 1 has the best focus value measured using the optical microscope 3
• ZM value A ZEB value is calculated, and the obtained ZEB value is stored in association with the position coordinates of each measurement point. As a result, an AF-MAP for the electron beam apparatus is created.
• the best focus value of the point between the measurement points is calculated by interpolation. It may be calculated and stored in correspondence with the XY coordinates of the interpolation point.
• the AF execution command is transmitted to the AF control unit 2 in step S 3 to execute the autoforcing of the optical microscope 3. Then, when a response signal is returned from the AF control device 2, it is determined in step S4 whether the returned response signal indicates that the focus value has been successfully acquired normally or abnormally. Do. In the case of normal termination, the focus value obtained by the AF controller 2 is included in the response signal.
• step S4 the process proceeds from step S4 to step S5, and the focus value included in the response signal is converted to the electron beam apparatus 100 using the above equation (1) (or (2)).
• the voltage value to be applied to the focusing lens is converted to an AF value, which is stored in an appropriate storage device (not shown).
• the AF value is stored in association with 1 1. If the response signal is an abnormal end, error processing is performed in step S6, and it is stored in the storage device in correspondence with the coordinates of the measurement point.
• the error processing in this case is, for example, processing to repeat autofocus at the same position and repeat until normal end, and processing to substitute the focus value at the time of abnormal end with the focus value of the adjacent measurement point, etc. is there.
• the focus value obtained thereby is converted in step S5.
• the PC device 1 When storage in the storage device is completed, the PC device 1 receives the measurement point (X, y) at which the AF value is measured.
• the AF values for measuring points (X, y), (X, y), ... (X, y) are The AF value is stored in association with each coordinate.
• the AF values of all the measurement points are stored, and AF—MAP is created.
• the created AF—MAP is referred to when inspecting a defect on a sample, etc., the AF value corresponding to the coordinates of the inspection point on the wafer W is read out, and the voltage corresponding to that value is the focus lens of the electron beam apparatus 100 Applied to the
• FIG. 7 shows a capacitance sensor 4 that can be used in a sample inspection apparatus according to another embodiment of the present invention.
• the capacitance sensor 4 detects the capacitance formed between the probe and the object to be measured, and the capacitance changes in accordance with the change in the distance between them. .
• the measurement position is fixed by fixing such a capacitance sensor 4 and moving the stage on which the wafer W is mounted to position the measurement position on the wafer directly below the probe of the capacitance sensor.
• the capacitance value between the Z-axis coordinate of the sensor and the probe of the capacitance sensor can be detected, and the capacitance value can also calculate the distance between them.
• Capacitance and distance are in a linear relationship, and therefore, the linear form can be used to convert the capacitance into distance to detect the position of the surface of wafer W in the Z-axis direction.
• the value in the Z-axis direction is set to the voltage value to be applied to the focusing electrostatic lens of the electron beam apparatus, using the same equation as the above equation (1) or (2).
• An AF-MAP can be created by converting and storing the obtained voltage value in combination with the coordinates of the measurement position.
• the voltage to be applied to the focus lens of the electron beam apparatus also differs depending on the charged state of the surface of the wafer W. Therefore, instead of the capacitance sensor, an appropriate surface potential sensor is used to measure the surface potential of the wafer W to obtain charge information, and based on the charge information, a voltage to be applied to the focus lens, ie, AF You can get a value.

Landscapes

• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Testing Or Measuring Of Semiconductors Or The Like (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=37396426

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (10)

Citations (6)

Family Cites Families (6)

• 2005
  • 2005-05-02 JP JP2005134136A patent/JP4959149B2/ja not_active Expired - Lifetime
• 2006
  • 2006-04-27 KR KR1020077027719A patent/KR101213587B1/ko not_active Expired - Lifetime
  • 2006-04-27 US US11/913,387 patent/US7964844B2/en active Active
  • 2006-04-27 WO PCT/JP2006/308843 patent/WO2006120917A1/ja not_active Ceased
  • 2006-04-28 TW TW095115198A patent/TWI390648B/zh active

Patent Citations (6)

Also Published As

Similar Documents

Legal Events