JP2010219372A - Electron beam drawing device, and method of deciding cathode life of electron gun - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device capable of detecting abnormality of an electron gun and a high-voltage power circuit. <P>SOLUTION: The drawing device 100 includes: the electron gun 201 which emits an electron beam 200; the high-voltage power circuit 110 which applies an acceleration voltage for electron to the electron gun 201; an emitter resistance variation detection circuit 54 arranged in the high-voltage power circuit 110 and detecting variation in emitter resistance of the electron gun 201; a recording circuit 80 arranged in the high-voltage power circuit 110 and recording the detected variation in emitter resistance; and an electron optical system which irradiates a desired position of a sample with the electron beam 200 emitted by the electron gun 201. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electron beam drawing apparatus and a method for determining the cathode life of an electron gun, and more particularly to an electron beam drawing apparatus having a function of monitoring an abnormality of an electron gun.

  Lithography technology, which is responsible for the progress of miniaturization of semiconductor devices, is an extremely important process for generating a pattern among semiconductor manufacturing processes. In recent years, with the high integration of LSI, circuit line widths required for semiconductor devices have been reduced year by year. In order to form a desired circuit pattern on these semiconductor devices, a highly accurate original pattern (also referred to as a reticle or a mask) is required. Here, the electron beam (electron beam) drawing technique has an essentially excellent resolution, and is used for producing a high-precision original pattern.

  FIG. 10 is a conceptual diagram for explaining the operation of a conventional variable shaping type electron beam drawing apparatus. The variable shaped electron beam (EB) drawing apparatus operates as follows. In the first aperture 410, a rectangular opening for forming the electron beam 330, for example, a rectangular opening 411 is formed. Further, the second aperture 420 is formed with a variable shaping opening 421 for shaping the electron beam 330 having passed through the opening 411 of the first aperture 410 into a desired rectangular shape. The electron beam 330 irradiated from the charged particle source 430 and passed through the opening 411 of the first aperture 410 is deflected by the deflector, passes through a part of the variable shaping opening 421 of the second aperture 420, and passes through a predetermined range. The sample 340 mounted on a stage that continuously moves in one direction (for example, the X direction) is irradiated. That is, the drawing area of the sample 340 mounted on the stage in which the rectangular shape that can pass through both the opening 411 of the first aperture 410 and the variable shaping opening 421 of the second aperture 420 is continuously moved in the X direction. Drawn on. A method of creating an arbitrary shape by passing both the opening 411 of the first aperture 410 and the variable shaping opening 421 of the second aperture 420 is referred to as a variable shaping method.

  In an electron beam drawing apparatus, an electron beam is emitted from an electron gun, and a high voltage power supply circuit for applying an acceleration voltage is connected to the electron gun. Conventionally, it has been difficult to detect abnormalities in such an electron gun and a high-voltage power supply circuit. In particular, it was difficult to determine the lifetime of the cathode that is a consumable. For this reason, conventionally, there are many cases in which the cathode has to be replaced suddenly during operation of the drawing apparatus, and the user has been forced to stop the apparatus unexpectedly. Therefore, a method for predicting the life of the cathode has been demanded. Further, it is difficult to detect an abnormality of a high-voltage power source applied to an electron gun with high accuracy during drawing. With the recent miniaturization of patterns, for example, acceleration voltage that affects pattern dimensions must be controlled with high accuracy. However, conventionally, for example, it has been possible to confirm a very large fluctuation of about 10 to 100 times, and it has been difficult to detect a highly accurate fluctuation of the acceleration voltage.

  Here, as a technique related to the electron gun, PID control is performed in which the current density is periodically measured during drawing so that the current density becomes substantially constant, and the control value is changed according to the measured current density. A technique is disclosed (for example, see Patent Document 1).

JP 2009-010078 A

  As described above, it has been difficult to detect abnormalities in the electron gun and the high-voltage power supply circuit during drawing. In addition, it is difficult to determine the life of the cathode that is a consumable.

  It is an object of the present invention to provide an apparatus and a method that can overcome such problems and detect an abnormality in an electron gun and a high-voltage power supply circuit.

An electron beam drawing apparatus according to one embodiment of the present invention includes:
An electron gun that emits an electron beam;
A high voltage power supply circuit for applying an electron acceleration voltage to the electron gun;
An emitter resistance variation detector that is disposed in the high voltage power supply circuit and detects the variation of the emitter resistance of the electron gun,
A recording unit that is arranged in the high-voltage power supply circuit and records the detected variation of the emitter resistance;
An electron optical system for irradiating a desired position of the sample with an electron beam emitted from an electron gun;
It is provided with.

An electron beam drawing apparatus according to another aspect of the present invention includes:
An electron gun that emits an electron beam;
A high voltage power supply circuit for applying an electron acceleration voltage to the electron gun;
An acceleration voltage DC fluctuation detection unit that is arranged in the high-voltage power supply circuit and detects fluctuations in the DC component of the acceleration voltage applied to the electron gun;
A recording unit that is arranged in the high-voltage power supply circuit and records a change in the DC component of the detected acceleration voltage exceeding the threshold;
An electron optical system for irradiating a desired position of the sample with an electron beam emitted from an electron gun;
It is provided with.

An electron beam drawing apparatus according to another aspect of the present invention includes:
An electron gun that emits an electron beam;
A high voltage power supply circuit for applying an electron acceleration voltage to the electron gun;
An emission current fluctuation detection unit that is arranged in the high-voltage power supply circuit and detects fluctuations in the emission current flowing through the electron gun;
An emission current fluctuation detection unit that is arranged in the high-voltage power supply circuit and detects fluctuations in the bias voltage applied to the electron gun;
A recording unit that is arranged in the high-voltage power supply circuit and records the detected emission current fluctuation and bias voltage fluctuation exceeding a threshold;
An electron optical system for irradiating a desired position of the sample with an electron beam emitted from an electron gun;
It is provided with.

An electron beam drawing apparatus according to another aspect of the present invention includes:
An electron gun that emits an electron beam;
A high voltage power supply circuit for applying an electron acceleration voltage to the electron gun;
An accelerating voltage DC fluctuation detection unit that is arranged in the high-voltage power supply circuit and detects fluctuations in power supplied to the filament of the electron gun;
A recording unit that is arranged in the high-voltage power supply circuit and records the detected power fluctuation of the filament exceeding the threshold;
An electron optical system for irradiating a desired position of the sample with an electron beam emitted from an electron gun;
It is provided with.

The method for determining the cathode life of the electron gun of one embodiment of the present invention is as follows.
Detecting a change in emitter resistance of an electron gun that emits an electron beam during drawing;
Recording the detected variations in emitter resistance;
Determining the lifetime of the cathode of the electron gun when the variation of the emitter resistance exceeds at least one of a predetermined frequency and a predetermined magnitude;
It is provided with.

  According to one embodiment of the present invention, an abnormality in emitter resistance can be detected. Further, according to one embodiment of the present invention, an abnormality in the emission current can be detected. Further, according to one embodiment of the present invention, abnormality in the bias voltage can be detected. Further, according to one embodiment of the present invention, it is possible to detect an abnormal power of a filament. In addition, according to one embodiment of the present invention, the lifetime of the cathode can be determined.

1 is a conceptual diagram illustrating a configuration of a drawing apparatus according to Embodiment 1. FIG. 2 is a conceptual diagram illustrating an internal configuration of a high-voltage power supply circuit and an electron gun according to Embodiment 1. FIG. 6 is a diagram illustrating an example of a variation factor of a DC component in Embodiment 1. FIG. FIG. 10 is a diagram showing another example of the DC component variation factor in the first embodiment. 6 is a diagram illustrating an example of fluctuations of a direct current component in the first embodiment. FIG. 6 is a diagram illustrating an example of fluctuations in alternating current components in the first embodiment. FIG. 6 is a diagram illustrating an example of fluctuations in alternating current components in the first embodiment. FIG. 6 is a diagram showing an example of variations in emitter resistance in the first embodiment. FIG. 6 is a diagram showing an example of a state of J drop in Embodiment 1. FIG. It is a conceptual diagram for demonstrating operation | movement of a variable shaping type | mold electron beam exposure apparatus.

Embodiment 1 FIG.
FIG. 1 is a conceptual diagram illustrating a configuration of a drawing apparatus according to the first embodiment. In FIG. 1, the drawing apparatus 100 includes a high-voltage power supply circuit 110, a control computer 120, a control circuit 140, and a drawing unit 150. The drawing apparatus 100 draws a desired pattern on the sample 101 using the electron beam 200. The drawing unit 150 includes an electron column 102 and a drawing chamber 103.

  In the electron column 102, an electron gun 201, an illumination lens 202, a first aperture 203, a projection lens 204, a deflector 205, a second aperture 206, an objective lens 207, and a deflector 208 are provided. The illumination lens 202, the first aperture 203, the projection lens 204, the deflector 205, the second aperture 206, the objective lens 207, and the deflector 208 are examples of an electron optical system. An XY stage 105 is disposed in the drawing chamber 103. On the XY stage 105, a sample 101 to be drawn is placed.

  The high-voltage power supply circuit 110, the control computer 120, and the control circuit 140 are connected to each other by a bus (not shown). The high voltage power supply circuit 110 and the control circuit 140 are controlled by the control computer 120. The high voltage power supply circuit 110 is connected to the electron gun 201 by a high voltage cable 130. The drawing unit 150 is controlled by the control circuit 140.

  In FIG. 1, constituent parts necessary for explaining the first embodiment are shown. The drawing apparatus 100 may include other configurations. The operation of the drawing unit 150 when drawing a pattern on the sample 101 will be described below.

  The electron beam 200 emitted from the electron gun 201 illuminates the entire first aperture 203 having a rectangular hole, for example, a rectangular hole, by the illumination lens 202. Here, the electron beam 200 is first formed into a rectangle, for example, a rectangle. Then, the electron beam 200 of the first aperture image that has passed through the first aperture 203 is projected onto the second aperture 206 by the projection lens 204. The position of the first aperture image on the second aperture 206 is controlled by the deflector 205, and the beam shape and size can be changed. Then, the electron beam 200 of the second aperture image that has passed through the second aperture 206 is focused by the objective lens 207, deflected by the deflector 208, and the sample 101 on the XY stage 105 that is movably disposed. The desired position is irradiated.

  FIG. 2 is a conceptual diagram showing the internal configuration of the high-voltage power supply circuit and the electron gun in the first embodiment. In FIG. 2, the electron gun 201 has a cathode 21 and an anode 23. The cathode 21 has a Wehnelt electrode 26, an emitter 27, a filament 28, and an insulator 29. The anode 23 is grounded (ground fault) although not shown. An emitter 27 is disposed at a tip portion where two bipolar filaments are coupled. A heating current is passed through the two poles of the filament 28 through the high-voltage power supply circuit 110 via the high-voltage cable 130 in a state where the negative voltage (−) side of the DC acceleration voltage is applied to the intermediate voltage between the two poles of the filament 28. Further, a DC bias voltage (Wernert voltage) is applied from the high voltage power supply circuit 110 via the high voltage cable 130 between the intermediate voltage of the both electrodes of the filament 28 and the Wehnelt electrode 26. The positive electrode (+) side of the DC acceleration voltage is grounded. An emission current flows as electrons are emitted from the emitter 27 heated by the filament 28. The emitted electrons are accelerated by being pulled by the anode 23 and emitted from the electron gun 201.

  In the high voltage power supply circuit 110, there are a booster circuit 10, a filter circuit 20, a bias circuit 30, an emission current detection circuit 40, a filament circuit 50, an acceleration voltage detection circuit 60, a determination circuit 70, and a recording circuit 80 (an example of a recording unit). Is arranged. A bias voltage DC / AC fluctuation detection circuit 22 (an example of a bias voltage fluctuation detection unit) is disposed in the filter circuit 20. An acceleration voltage AC fluctuation detection circuit 32 (an example of an acceleration voltage fluctuation detection unit) is disposed in the bias circuit 30. In the emission current detection circuit 40, an emission current DC / AC fluctuation detection circuit 42 (an example of an emission current fluctuation detection unit) is arranged. In the filament circuit 50, a filament DC / AC fluctuation detection circuit 52 (an example of a filament power fluctuation detection unit) and an emitter resistance fluctuation detection circuit 54 (an example of an emitter resistance fluctuation detection unit) are arranged. An acceleration voltage DC fluctuation detection circuit 62 (an example of an acceleration voltage fluctuation detection unit) is disposed in the acceleration voltage detection circuit 60.

  After the voltage of the power supplied from the power supply on the user side is boosted by the booster circuit 10, it is rectified by the filter circuit 20, and a bias voltage (Wernert voltage) is applied to the Wehnelt electrode 26. Further, the boosted voltage is output to the bias circuit 30. The bias circuit 30 applies the negative side of the DC acceleration voltage to the intermediate voltage between the two poles of the filament 28, and from the emission current detection circuit 40 to the emission current detection circuit 40. A control signal based on the detected emission current is input so as to be periodically fed back every time a predetermined fixed time elapses, for example, and the bias voltage is variably controlled so as to become a target emission current. Then, the filament circuit 50 allows a heating current to flow through both electrodes of the filament 28. Further, the acceleration voltage detection circuit 60 periodically detects the acceleration voltage, and outputs a control signal based on the detected acceleration voltage to the booster circuit 10 so as to be periodically fed back every time a predetermined fixed time elapses, for example. The booster circuit 10 is controlled.

  Here, the bias voltage DC / AC fluctuation detection circuit 22 constantly detects each fluctuation between the DC component of the bias voltage and the AC component that becomes noise, and outputs the detected result to the determination circuit 70. The acceleration voltage AC fluctuation detection circuit 32 constantly detects the fluctuation of the AC component that becomes noise of the acceleration voltage, and outputs the detected result to the determination circuit 70. The emission current DC / AC fluctuation detection circuit 42 always detects each fluctuation of the DC component of the emission current and the AC component that becomes noise, and outputs the detected result to the determination circuit 70. The filament DC / AC fluctuation detection circuit 52 constantly detects each fluctuation between the DC component of the filament power and the AC component that becomes noise, and outputs the detected result to the determination circuit 70. The emitter resistance fluctuation detection circuit 54 calculates the emitter resistance from the voltage value and the current value that are the basis of the filament power calculation, constantly detects such emitter resistance fluctuation, and outputs the detected result to the determination circuit 70. To do.

  FIG. 3 is a diagram illustrating an example of a variation factor of the DC component in the first embodiment. As shown in FIG. 3, the DC component of each detection target may have a long-term and gentle fluctuation due to, for example, a drift accompanying a change with time.

  FIG. 4 is a diagram showing another example of the variation factor of the DC component in the first embodiment. As shown in FIG. 4, the DC component of each detection target may vary due to, for example, a phenomenon that the output value remains shifted after a steep variation.

  FIG. 5 is a diagram illustrating an example of fluctuations in the DC component in the first embodiment. FIG. 5 shows, as an example, fluctuations in the DC component of the acceleration voltage. The determination circuit 70 receives a DC fluctuation detection average value calculation request from the control computer 120. Based on such a request, the determination circuit 70 calculates, for example, an average value of the DC component values of the acceleration voltage detected during a predetermined period. Such an average value is a reference. Further, the determination circuit 70 receives, for example, a threshold value for dc component variation of the acceleration voltage from the control computer 120. The threshold value is an allowable variation range between the upper and lower limits from the reference average value. The determination circuit 70 also receives a monitoring (monitoring) start request from the control computer 120. When the monitoring start request is input, the determination circuit 70 determines whether or not the DC component of the acceleration voltage that is constantly detected, for example, exceeds a threshold value. As for the direct current component, for example, the result of steep fluctuation by one point is not determined to exceed the threshold value. A sudden change is determined by an AC component described later. The same operation is performed for the bias voltage, emission current, and filament power.

  The recording circuit 80 records, for example, the generation time, the convergence time, and the maximum fluctuation amount for the portion where the determination circuit 70 determines that the threshold value has been exceeded for the DC component of the acceleration voltage. When a recording output request is input from the control computer 120, the recorded result is output to the control computer 120. The same operation is performed for the bias voltage, emission current, and filament power.

  FIG. 6 is a diagram illustrating an example of fluctuations in the AC component in the first embodiment. As shown in FIG. 6, instantaneous fluctuations are captured for the AC components to be detected.

  FIG. 7 is a diagram illustrating an example of the variation of the AC component in the first embodiment. FIG. 7 shows, as an example, fluctuations in the AC component that becomes noise of the acceleration voltage. When detecting the AC fluctuation, each detection circuit removes the value of the DC component, and sets the reference voltage of the acceleration voltage and the bias voltage, the reference current of the emission current, and the reference power of the filament power to zero. Thereby, it can detect in the range only of a noise component. As a result, the resolution at the time of detection can be improved. Then, the determination circuit 70 inputs each detection result from which the DC component has been removed. The determination circuit 70 inputs, for example, a threshold for changing the AC component of the acceleration voltage from the control computer 120. The threshold value is an allowable range of fluctuation between the upper and lower limits from the reference value 0. The determination circuit 70 also receives a monitoring (monitoring) start request from the control computer 120. When the monitoring start request is input, the determination circuit 70 determines whether or not the AC component of the acceleration voltage that is constantly detected, for example, exceeds a threshold value. As for the AC component, it is determined that the result of instantaneous fluctuation has also exceeded the threshold. The same operation is performed for the bias voltage, emission current, and filament power.

  The recording circuit 80 records, for example, the generation time and the maximum fluctuation amount at a location where the determination circuit 70 determines that the threshold value has been exceeded for the DC component of the acceleration voltage. When a recording output request is input from the control computer 120, the recorded result is output to the control computer 120. The same operation is performed for the bias voltage, emission current, and filament power.

  The result recorded as described above is output to the control computer 120 by the recording circuit 80 in response to a recording output request from the control computer 120. Then, it is possible to monitor whether or not each detection target has an abnormality by checking the detection record periodically after the drawing is completed or during the drawing. Alternatively, the control computer 120 may control to stop the drawing operation when there is an abnormality.

Next, the variation of the emitter resistance will be described.
FIG. 8 is a diagram illustrating an example of variation in emitter resistance in the first embodiment. The inventor has found that the behavior of the variation of the emitter resistance and the behavior of the variation of the current density substantially coincide as shown in FIG.

  FIG. 9 is a diagram illustrating an example of a J drop state according to the first embodiment. In the drawing apparatus, as shown in FIG. 9, the current density instantaneously reaches the maximum fluctuation value and gradually converges to the value before the fluctuation over several minutes to ten and several minutes (this phenomenon is referred to as “J drop”). Defined) may occur. When such a phenomenon occurs, a large error occurs in the electron beam irradiation amount, resulting in an abnormal pattern dimension. Therefore, it can be said that the cathode 21 in which such a phenomenon occurs has already expired. Therefore, it is required to replace the cathode 21 before such a phenomenon occurs. Conventionally, however, it has been difficult to predict when such a phenomenon will occur, and it has been difficult to determine the cathode life.

  Therefore, in the first embodiment, as shown in FIG. 8, the cathode life is determined by constantly monitoring the variation of the emitter resistance that exhibits substantially the same behavior as the variation of the current density. The determination circuit 70 receives the emitter resistance threshold value from the control computer 120. The threshold value is an allowable range of fluctuation between the upper and lower limits from the reference stable period value. Alternatively, the threshold value is an allowable range of the variation frequency of the emitter resistance. Then, the determination circuit 70 inputs a monitoring start request from the control computer 120. When the monitoring start request is input, the determination circuit 70 determines whether or not the constantly detected variation of the emitter resistance exceeds the frequency or magnitude indicated by the threshold value.

  The recording circuit 80 records the variation of the emitter resistance, and also records the occurrence time and the maximum variation amount at the location determined by the determination circuit 70 that exceeds the threshold value. When a recording output request is input from the control computer 120, the recorded result is output to the control computer 120. Then, the control computer 120 determines that the life of the cathode of the electron gun 201 is at least one of the frequency and the magnitude of the fluctuation of the emitter resistance, and outputs the result. Alternatively, the state of variation of the emitter resistance may be output, and the user may determine the life of the cathode of the electron gun 201 from the state of variation. In any case, the cathode 21 may be replaced before the lifetime is exceeded. The control computer 120 is connected to an output function (not shown) such as an external interface for outputting information to a monitor, a printer, or a network.

  The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

  In addition, although descriptions are omitted for parts and the like that are not directly required for the description of the present invention, such as a device configuration and a control method, a required device configuration and a control method can be appropriately selected and used. For example, although the description of the control unit configuration for controlling the drawing apparatus 100 is omitted, it goes without saying that the required control unit configuration is appropriately selected and used.

  In addition, all high-voltage power supply circuits and drawing apparatuses that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Booster circuit 20 Filter circuit 21 Cathode 22 Bias voltage DC / AC fluctuation detection circuit 23 Anode 26 Wehnelt electrode 27 Emitter 28 Filament 29 Insulator 30 Bias circuit 32 Acceleration voltage AC fluctuation detection circuit 40 Emission current detection circuit 42 Emission current DC / AC fluctuation Detection circuit 50 Filament circuit 52 Filament DC / AC fluctuation detection circuit 54 Emitter resistance fluctuation detection circuit 60 Acceleration voltage detection circuit 62 Acceleration voltage DC fluctuation detection circuit 70 Determination circuit 80 Recording circuit 100 Drawing apparatus 101, 340 Sample 102 Electronic lens barrel 103 Drawing Chamber 105 XY stage 110 High voltage power supply circuit 120 Control computer 130 High voltage cable 140 Control circuit 150 Drawing unit 200 Electron beam 201 Electron gun 202 Illumination lenses 203, 206, 410, 42 Aperture 204 a projection lens 205, 208 the deflector 207 an objective lens 330 electron beam 411 opening 421 variable-shaped opening 430 a charged particle source

Claims (5)

An electron gun that emits an electron beam;
A high-voltage power supply circuit for applying an electron acceleration voltage to the electron gun;
An emitter resistance variation detector disposed in the high-voltage power supply circuit for detecting variations in the emitter resistance of the electron gun;
A recording unit that is disposed in the high-voltage power supply circuit and records the detected variation of the emitter resistance;
An electron optical system for irradiating a desired position of the sample with an electron beam emitted from the electron gun;
An electron beam drawing apparatus comprising: An electron gun that emits an electron beam;
A high-voltage power supply circuit for applying an electron acceleration voltage to the electron gun;
An acceleration voltage DC fluctuation detection unit that is arranged in the high-voltage power supply circuit and detects a fluctuation of a DC component of the acceleration voltage applied to the electron gun;
A recording unit that is arranged in the high-voltage power supply circuit and records a change in a DC component of a detected acceleration voltage that exceeds a threshold value;
An electron optical system for irradiating a desired position of the sample with an electron beam emitted from the electron gun;
An electron beam drawing apparatus comprising: An electron gun that emits an electron beam;
A high-voltage power supply circuit for applying an electron acceleration voltage to the electron gun;
An emission current fluctuation detection unit that is arranged in the high-voltage power supply circuit and detects fluctuations in the emission current flowing through the electron gun;
An emission current fluctuation detection unit that is arranged in the high-voltage power supply circuit and detects a fluctuation of a bias voltage applied to the electron gun;
A recording unit that is disposed in the high-voltage power supply circuit and records a detected emission current fluctuation and a bias voltage fluctuation exceeding a threshold;
An electron optical system for irradiating a desired position of the sample with an electron beam emitted from the electron gun;
An electron beam drawing apparatus comprising: An electron gun that emits an electron beam;
A high-voltage power supply circuit for applying an electron acceleration voltage to the electron gun;
An accelerating voltage DC fluctuation detection unit that is arranged in the high-voltage power supply circuit and detects a power fluctuation supplied to the filament of the electron gun;
A recording unit that is arranged in the high-voltage power supply circuit and records a detected power fluctuation of the filament that exceeds a threshold value;
An electron optical system for irradiating a desired position of the sample with an electron beam emitted from the electron gun;
An electron beam drawing apparatus comprising: Detecting a change in emitter resistance of an electron gun that emits an electron beam during drawing;
Recording the detected variations in emitter resistance;
Determining the lifetime of the cathode of the electron gun when the variation of the emitter resistance exceeds at least one of a predetermined frequency and a predetermined magnitude;
A method for determining the cathode life of an electron gun, comprising:

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