Source: http://www.google.com/patents/US7462838?ie=ISO-8859-1
Timestamp: 2014-12-18 22:08:26
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Matched Legal Cases: ['art 108', 'art 2', 'art 4', 'art 1', 'art 2', 'art 4', 'art 2', 'art 2', 'art 2', 'art 2', 'art 2', 'art 2']

Patent US7462838 - Electrostatic deflection control circuit and method of electronic beam ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsAn electrostatic deflection circuit and method of an electronic beam measuring apparatus which can achieve the high precision of the electronic beam measuring and contribute to the simplification of the structure of the apparatus is provided. In an analog arithmetic circuit included in an analog operation...http://www.google.com/patents/US7462838?utm_source=gb-gplus-sharePatent US7462838 - Electrostatic deflection control circuit and method of electronic beam measuring apparatusAdvanced Patent SearchPublication numberUS7462838 B2Publication typeGrantApplication numberUS 11/521,465Publication dateDec 9, 2008Filing dateSep 15, 2006Priority dateSep 16, 2005Fee statusPaidAlso published asUS8044369, US20070063146, US20090121150Publication number11521465, 521465, US 7462838 B2, US 7462838B2, US-B2-7462838, US7462838 B2, US7462838B2InventorsHiroshi SasakiOriginal AssigneeHitachi High-Technologies CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (4), Referenced by (4), Classifications (16), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetElectrostatic deflection control circuit and method of electronic beam measuring apparatusUS 7462838 B2Abstract An electrostatic deflection circuit and method of an electronic beam measuring apparatus which can achieve the high precision of the electronic beam measuring and contribute to the simplification of the structure of the apparatus is provided. In an analog arithmetic circuit included in an analog operation part constituting an electrostatic deflection circuit, output voltages of multipliers are added and output by an adder. When the magnification is low, as the side of an ordinarily closed contact is closed driven by a relay driving circuit, the output of the adder is amplified by a high gain amplifier with a high amplification factor and applied to an electrostatic deflecting board. When the magnification is high, the side of an ordinarily open contact is closed and it is amplified by a low gain amplifier with a low amplification factor and applied to the electrostatic deflecting board in the same way.
1. An electrostatic deflection circuit of an electronic beam measuring apparatus which outputs a deflection signal to an electrostatic deflector to deflect an electronic beam to scan on a sample, comprises:
a deflection circuit for low magnification comprising a first operational amplifier of a first amplification factor which amplifies the deflection signal by the first operational amplifier;
a deflection circuit for high magnification comprising a second operational amplifier of a second amplification factor which is lower than the first amplification factor, which amplifies the deflection signal by the second operational amplifier; and
a switch circuit which switches to the deflection circuit for low magnification and outputs the deflection signal to the electrostatic deflector when a scan magnification of the electronic beam measuring apparatus is no more than a given value, and switches to the deflection circuit for high magnification and outputs the deflection signal to the electrostatic deflector when the scan magnification is over the given value.
2. The electrostatic deflection circuit of the electronic beam measuring apparatus according to claim 1, wherein
the switch circuit performs the switching by a relay with contact.
3. The electrostatic deflection circuit of the electronic beam measuring apparatus according to claim 1, wherein
the switch circuit performs the switching by a semiconductor relay.
4. An electrostatic deflection method of an electronic beam measuring apparatus which outputs a deflection signal to an electrostatic deflector to deflect an electronic beam to scan on a sample, comprises:
a deflection process for low magnification with a first operational amplifier of a first amplification factor amplifying the deflection signal by the first operational amplifier;
a deflection process for high magnification with a second operational amplifier of a second amplification factor which is lower than the first amplification factor amplifying the deflection signal by the second operational amplifier; and
a switching process which switches to the deflection process for low magnification and outputs the deflection signal to the electrostatic deflector when a scan magnification of the electronic beam measuring apparatus is no more than a given value, and switches to the deflection process for high magnification and outputs the deflection signal to the electrostatic deflector when the scan magnification is over the given value.
INCORPORATION BY REFERENCE The present application claims priority from Japanese application JP2005-270660 filed on Sep. 16, 2005, the content of which is hereby incorporated by reference into this application.
BACKGROUND OF THE INVENTION The present invention relates to an electrostatic deflection circuit and method for controlling the deflection of an electronic beam in an electronic beam measuring apparatus which scans a sample by an electron beam (electronic beam) and measures minute patterns.
SUMMARY OF THE INVENTION However, in the case of the first conventional apparatus described above, it is provided with both of the electrostatic deflector and the electromagnetic deflector and the electromagnetic deflector includes a coil and it generates the electromagnetic induction. Therefore, in this apparatus even while the deflection is being performed by the electrostatic deflector the beam passes through within the electromagnetic deflector and it is affected by the electromagnetic induction. For this reason, there has been a problem that it is difficult to obtain an image of high precision or high magnification because the center of the field of vision is shifted with the change of the scan magnification or the aberration such as a distortion is generated on the beam. Also, as it is provided with two kinds of deflectors there have been problems that it is difficult to mechanically match the light axes of the deflectors each other, moreover, that the structure of the entire deflector would be complicated, large, and expensive.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a principle structure diagram of an electronic beam measuring apparatus according to an embodiment of the present invention.
DESCRIPTION OF THE EMBODIMENTS Next, an embodiment of the present invention will be explained in detail referring to the drawings.
More specifically, the electronic beam measuring apparatus 10 is provided with an electron source 101 which generates an electron beam (electronic beam), a condenser lens 6 which once converges the electronic beam generated at the electron source 101, a deflector 3 which deflects the electronic beam by generating an electrostatic field, an electrostatic deflection circuit (corresponding to an �electrostatic deflection circuit� stated in the claims) 100 which supplies a deflection voltage to the deflector 3, an object lens 5 which focuses the electronic beam on a sample P by the object lens 5, a secondary electron detector 106 which detects a secondary electron radiated resulting from the electronic beam being irradiated on the sample P, an amplifier 107 which amplifies a detection signal which is output when the secondary electron detector 106 detects the secondary electron, a signal processing part 108 which generates an image data (or an image signal) of the sample P based on the amplified detection signal, and an observation monitor 109 which displays an image of the sample P based on the generated image data (or image signal).
The analog operation part 2 is provided with analog arithmetic circuits 2 x 1-2 x 4, 2 y 1-2 y 4. To the analog arithmetic circuits 2 x 1-2 x 4, 2 y 1-2 y 4 the magnification switch signal Sd is input from the control part 4 as well as the X deflection signal Sx and the Y deflection signal Sy are input from the D-A conversion part 1. Also, the deflection voltages X1-X4, Y1-Y4 output from the analog arithmetic circuits 2 x 1-2 x 4, 2 y 1-2 y 4 are applied to the electrostatic deflecting boards 3 x 1-3 x 4, 3 y 1-3 y 4 (described later) of the deflector 3 respectively.
The deflector 3 comprises a plurality of electrostatic deflecting boards 3 x 1-3 x 4, 3 y 1-3 y 4 which work as deflecting factors for the electronic beam, and these are arranged in a ring around the light axis (a central axis along the forward direction of the electronic beam). Namely, as shown in FIG. 1, the electronic beam (electron probe) with the given current value passes within the ring of the deflector 3 and receives an influence of the electrostatic field in the ring and gets deflected at any of point on the path of being radiated out from the electron source 101, converged by the condenser lens 6, and focused on the sample P by the object lens 5.
Returning to FIG. 4, in this embodiment, for example from the point of view that the large amount of deflection can be obtained and the precision is good, as the deflector 3, an example using an 8 poles deflector which is provided with 8 electrostatic deflecting boards 3 x 1-3 x 4, 3 y 1-3 y 4 will be explained. Of course, the 8 poles deflector is an example and as the deflector 3 an electrostatic deflector which has another structure corresponding to the use object or mode, for example, a 4 poles deflector which is provided with 4 electrostatic deflecting boards X+, X−, Y+, and Y− (neither of them is shown) and has a simpler structure, etc. may be used.
FIG. 5 is a block diagram showing an example of the structure of the analog arithmetic circuit 2 x 1 included in the analog operation part 2 in detail.
The structures of the analog arithmetic circuits 2 x 1-2 x 4, 2 y 1-2 y 4 are the same structures except that the multiplication rates of multipliers 21 x and 21 y (described later) are different.
The analog arithmetic circuit 2 x 1 is provided with a multiplier 21 x which has the X deflection signal Sx input and multiplies its voltage (X deflection voltage Vx) by given times and output it, a multiplier 21 y which has the Y deflection signal Sy input and multiplies its voltage (Y deflection voltage Vy) by given times and output it, an adder 22 which outputs a voltage which results from adding the output voltage of the multiplier 21 x and the output voltage of the multiplier 21 y, a high gain amplifier 23 q and a low gain amplifier 23 p which amplify the output voltage of the adder 22 by given gain and output it, a relay with contact 25 which switches either of the output of the high gain amplifier 23 q or the output of the low gain amplifier 23 p and output it to the electrostatic deflecting board 3 x 1, and a relay driving circuit 24 which drives the relay with contact 25.
The multipliers 21 x, 21 y are both operational amplifiers. The multipliers 21 x, 21 y of each of the analog arithmetic circuits 2 x 1-2 x 4, 2 y 1-2 y 4 amplify the voltage (the X deflection voltage Vx or the Y deflection voltage Vy) of the input signal (the X deflection signal Sx or the Y deflection signal Sy) by the following multiplication rate and output it. The multiplication rate α, β are set to add the main deflection signal and the deflection signal of its 90 degree direction to obtain a uniform electrostatic field in the deflector 3.
sign of analog
multiplier 21y
The adder 22 is structured including an operational amplifier. The output voltages of the adders 22 of each of the analog arithmetic circuits 2 x 1-2 x 4, 2 y 1-2 y 4 are as the followings.
of adder 22
+αVx +βVy
+αVx −βVy
−αVx +βVy
−αVx −βVy
+βVx +αVy
−βVx +αVy
+βVx −αVy
−βVx −αVy
The low gain amplifier 23 p is an operational amplifier including a differential amplifier circuit, a level shift circuit, an output circuit (either of them are not shown). The low gain amplifier 23 p has a function to linearly amplify and output the input voltage from the adder 22, and when the input signal from the adder 22 is no input the output voltage is 0. The low gain amplifier 23 p has a relatively small amplification factor, but as its noise figure (NF) is small (therefore the noise rate in the output signal is small), its linearity is good and its offset voltage is low, it can perform the highly precise amplification.
The high gain amplifier 23 q is a similar circuit to the low gain amplifier 23 p, but it is a so-called power operational amplifier and although the amplification factor and the output can be greater, the characteristics such as the noise figure, the linearity, and the lowness of the offset voltage are slightly worse than the low gain amplifier 23 p. The low gain amplifier 23 p and the high gain amplifier 23 q can be obtained at a low price and easily as a uniform one by using an appropriate kind from among the ones on the market as a packaged IC (Integrated Circuit) and by doing so a trouble of design or packaging can be saved. Of course the circuit may be implemented by combining the discrete devices.
Assuming that the amplification factor of the high gain amplifier 23 q is A1, the output voltages of the high gain amplifiers 23 q of each of the analog arithmetic circuits 2 x 1-2 x 4, 2 y 1-2 y 4 are the value which is the output voltage of the adder 22 multiplied by A1. Also, assuming that the amplification factor of the low gain amplifier 23 p is A2, the output voltages of the low gain amplifiers 23 p of each of the analog arithmetic circuits 2 x 1-2 x 4, 2 y 1-2 y 4 are the value which is the output voltage of the adder 22 multiplied by A2.
The relay with contact 25 is a relay of a 1a1b contact (c contact) mode relay which has mechanical contacts, and is provided with an ordinarily open contact (a contact) 25 a connected to the low gain amplifier 23 p, an ordinarily closed contact (b contact) 25 b connected to the high gain amplifier 23 q, a movable contact piece 25 m consisting of a magnetic alloy and connected to the electrostatic deflecting board 3 x 1, and a coil 25 h which generates a magnetic force when the operating current is supplied.
As shown in FIG. 5, when the operating current is not supplied to the coil 25 h, by the movable contact piece 25 m returning to the ordinarily closed contact 25 b side by a spring (not shown) or the elasticity of the movable contact piece 25 m itself or a magnetic force of a magnet (not shown), between the ordinarily closed contact 25 b and the movable contact piece 25 m it is closed and at the same time the ordinarily open contact 25 a is released. Also, when the operating current is supplied to the coil 25 h, a magnetic force is generated to the coil 25 h and by the movable contact piece 25 m operating to the ordinarily open contact 25 a side, between the ordinarily open contact 25 a and the movable contact piece 25 m it is closed and at the same time the ordinarily closed contact 25 b is released.
The relay driving circuit 24 drives the relay with contact 25 according to the magnification switch signal Sd input from the control part 4. That is, the relay driving circuit 24 does not supply the operating current to the coil 25 h when the magnification switch signal Sd indicates the �low magnification�. At this time, the output side of the high gain amplifier 23 q is connected to the electrostatic deflecting board 3 x 1 and the output voltage (the deflection voltage X1) of the high gain amplifier 23 q is applied to the electrostatic deflecting board 3 x 1. In the same way, the summary about the other analog arithmetic circuits 2 x 2-2 x 4, 2 y 1-2 y 4 is as the following. Here, the amplification factor of the high gain amplifier 23 q is assumed to be A1.
deflecting board
X1 = A1 (+αVx +βVy)
X2 = A1 (+αVx −βVy)
X3 = A1 (−αVx +βVy)
X4 = A1 (−αVx −βVy)
Y1 = A1 (+βVx +αVy)
Y2 = A1 (−βVx +αVy)
Y3 = A1 (+βVx −αVy)
Y4 = A1 (−βVx −αVy)
Also, the relay driving circuit 24 supplies the operating current to the coil 25 h when the magnification switch signal Sd indicates the �high magnification�. At this time, the output side of the low gain amplifier 23 p is connected to the electrostatic deflecting board 3 x 1 and the output voltage (the deflection voltage X1) of the low gain amplifier 23 p is applied to the electrostatic deflecting board 3 x 1. In the same way, the summary about the other analog arithmetic circuits 2 x 2-2 x 4, 2 y 1-2 y 4 is as the following. Here, the amplification factor of the low gain amplifier 23 p is assumed to be A2.
X1 = A2 (+αVx +βVy)
X2 = A2 (+αVx −βVy)
X3 = A2 (−αVx +βVy)
X4 = A2 (−αVx −βVy)
Y1 = A2 (+βVx +αVy)
Y2 = A2 (−βVx +αVy)
Y3 = A2 (+βVx −αVy)
Y4 = A2 (−βVx −αVy)
In this way, by inputting the necessary X deflection signal Sx and Y deflection signal Sy to the analog operation part 2, it is possible to create a desired electrostatic field within the ring of the deflector 3, and by changing the X deflection voltage Vx and the Y deflection voltage Vy by time, it is possible to change the deflection direction and the deflection amount of the electronic beam to scan on the sample. Further, by switching the magnification switch signal Sd to �low magnification� or �high magnification�, the scan magnification can be switched to the low magnification or the high magnification.
The electronic beam measuring apparatus of this embodiment can be used with the scan magnification of low magnification and high magnification. As the deflection voltage when the scan magnification is low magnification is, for example, a few hundreds V at the most, the output circuit (not shown) of the high gain amplifier 23 q needs to have a high pressure resistance to resist this voltage. Also, as the deflection voltage when the scan magnification is high magnification is, for example, a few V−a few hundreds mV at the most, the output circuit (not shown) of the low gain amplifier 23 p only needs to have the pressure resistance for this pressure.
Also, in the case when the image obtained by the measuring is displayed for example using an image display device (not shown) of 512 pixel�512 pixel, as the deflection voltage per 1 pixel at the low magnification is a few hundreds mV/pixel−a few V/pixel, the deflection system for low magnification including the high gain amplifier 23 q only needs to have the precision corresponding to this. Also, as the deflection voltage per 1 pixel at the high magnification is about a few mV/pixel, the deflection system for high magnification including the low gain amplifier 23 p is supposed to have a high precision corresponding to this.
For example, if the design rule of the integrated circuit to be a sample is 200 nm, the pattern measuring would be performed with the magnification of 200 thousands times, and the deflection voltage per 1 pixel at that time would be about 3.4 mV/pixel. Also, if the design rule is 90 nm, the pattern measuring would be performed with the magnification of 400 thousands times, and the deflection voltage per 1 pixel at that time would be about � of that of when the magnification is 200 thousands times, namely about 1.7 mV/pixel. The value of the deflection voltage at this time is almost equal to the noise level or the offset voltage of the power operational amplifier device.
In this embodiment, the problems described above are solved by switching to the output from the high gain amplifier 23 q which has a high pressure resistance and high output by the relay with contact 25 at the time of low magnification when it is necessary to output a high deflection voltage to the deflector 3, and by switching to the output from the low gain amplifier 23 p with low noise and low offset voltage by the relay with contact 25 at the time of high magnification when it is necessary to output a high precision deflection voltage waveform to the deflector 3.
Therefore, when the magnification is low as the deflection signal is amplified by the high gain amplifier 23 q the electronic beam measuring of wide field of view can be performed with sufficient precision, and when the magnification is high as the deflection signal is amplified by the low gain amplifier 23 p the electronic beam measuring with small noise and aberration and with high precision can be performed.
On switching to the low magnification or to the high magnification, if it is configured to be performed with the magnification with which the deflection voltage per 1 pixel would be greater than the offset voltage of the high gain amplifier 23 q, the image shift resulting from the switching of the low magnification and the high magnification is rarely generated. By this configuration, it is possible to omit the offset adjustment of the high gain amplifier 23 q. Also, by performing the switching by the relay with contact 25, as the structure of the analog arithmetic circuits 2 x 1-2 x 4, 2 y 1-2 y 4 except the high gain amplifier 23 q and the low gain amplifier 23 p can be used in common at the time of the low magnification and the high magnification, the deterioration of the precision by the device scattering can be restrained as well as the circuit can be simplified. Also, as the deflection of the electronic beam at the time of the low magnification and the high magnification can be performed by one deflector 3, the deflection mechanism of the electronic beam such as the deflector 3 can be simplified.
FIG. 6 is a block diagram showing an analog arithmetic circuit 2 bx 1 included in an analog operation part 2 b of a deformed example in detail.
The analog operation part 2 b can be used instead of the analog operation part 2 and has the similar function. The analog operation part 2 b is provided with, instead of the analog arithmetic circuits 2 x 1-2 x 4, 2 y 1-2 y 4 (see FIG. 3), analog arithmetic circuits 2 bx 1-2 bx 4, 2 by 1-2 by 4 which have the similar function.
The analog arithmetic circuit 2 bx 1 has the similar structure to the analog arithmetic circuit 2 x 1 except that it is provided with an optical MOS relay 26 instead of the relay with contact 25 and a relay driving circuit 24 b instead of the relay driving circuit 24. Also, as the analog arithmetic circuits 2 bx 2-2 bx 4, 2 by 1-2 by 4 have the similar structure to the analog arithmetic circuit 2 bx 1, their illustration is omitted.
The optical MOS relay 26 is provided with an ordinarily open device 26 a including a light receiving device and a power MOSFET, a light emitting device 26 c on the side of the ordinarily open device 26 a, an ordinarily closed device 26 b including a light receiving device and a power MOSFET, and a light emitting device 26 d on the side of the ordinarily closed device 26 b. The relay driving circuit 24 b, when the magnification switch signal Sd indicates the �low magnification�, puts the light emitting device 26 c off and puts the ordinarily open device 26 a in a non-conductive state, as well as lights the light emitting device 26 d and puts the ordinarily closed device 26 b in a conductive state. Thereby, the output voltage (the deflection voltage X1) of the high gain amplifier 23 q is applied to the electrostatic deflecting board 3 x 1.
Also, the relay driving circuit 24 b, when the magnification switch signal Sd indicates the �high magnification�, lights the light emitting device 26 c and puts the ordinarily open device 26 a in a conductive state, as well as puts the light emitting device 26 d off and puts the ordinarily closed device 26 b in a non-conductive state. Thereby, the output voltage (the deflection voltage X1) of the low gain amplifier 23 p is applied to the electrostatic deflecting board 3 x 1.
FIG. 7 is a block diagram showing an analog arithmetic circuit 2 cx 1 included in an analog operation part 2 c of another embodiment in detail.
In this analog arithmetic circuit 2 cx 1 it does not have the function of switching the low magnification and the high magnification and it amplifies the input voltage from the adder 22 by one amplifier 23 and applies it to the electrostatic deflecting board 3 x 1.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS3911321 *Aug 27, 1973Oct 7, 1975IbmError compensating deflection coils in a conducting magnetic tubeUS5546319 *Jan 27, 1995Aug 13, 1996Fujitsu LimitedMethod of and system for charged particle beam exposureJP2002117796A Title not availableJPH10199460A Title not available* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS7898447 *Jul 16, 2009Mar 1, 2011Nuflare Technology, Inc.Methods and systems for testing digital-to-analog converter/amplifier circuitsUS8044369 *Dec 3, 2008Oct 25, 2011Hitachi High-Technologies CorporationElectrostatic deflection control circuit and method of electronic beam measuring apparatusUS8129695 *Dec 28, 2009Mar 6, 2012Varian Semiconductor Equipment Associates, Inc.System and method for controlling deflection of a charged particle beam within a graded electrostatic lensUS20110155921 *Dec 28, 2009Jun 30, 2011Varian Semiconductor Equipment Associates, Inc.System and method for controlling deflection of a charged particle beam within a graded electrostatic lens* Cited by examinerClassifications U.S. Classification250/396.00R, 315/403, 250/396.0ML, 315/391, 315/395, 250/311, 250/397, 315/364, 315/370, 315/371, 250/310International ClassificationH01J3/26Cooperative ClassificationH01J37/24, H01J2237/2814, H01J2237/1516European ClassificationH01J37/24Legal EventsDateCodeEventDescriptionMay 9, 2012FPAYFee paymentYear of fee payment: 4Sep 15, 2006ASAssignmentOwner name: HITACHI HIGH-TECHNOLOGIES CORPORATION, JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SASAKI, HIROSHI;REEL/FRAME:018317/0374Effective date: 20060901RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google