JPH08222504A - Charged particle beam exposure system - Google Patents

Abstract

(57) [Summary] [Object] To provide a charged particle beam exposure apparatus for exposing a fine pattern with high accuracy. A means for extracting a portion for performing raster scanning exposure around a pattern, a means for continuously generating a scanning instruction signal to perform raster scanning exposure for a pattern end portion, and a portion for performing raster scanning exposure from pattern data. A means for separating and exposing at high speed by a vector scanning method is provided. [Effect] The processing accuracy around the pattern including the hypotenuse can be improved, and high-speed and good pattern exposure can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for exposing a fine pattern in a charged particle beam exposure system mainly used in the semiconductor industry.

[0002]

2. Description of the Related Art A charged particle beam exposure apparatus comprises an electron optical housing, a sample stage, a sample stage controller, a deflection driver, an exposure data controller, a control computer and the like.

CAD data of an LSI or the like is decomposed into basic figures of a plurality of types and given to an exposure data control section. This basic figure constitutes pattern data with information such as a figure code indicating the type of figure, coordinates indicating the origin, size of the figure, and exposure amount. The exposure data control unit
The exposure is controlled by performing deflection distortion correction based on the pattern data.

The exposure method of the charged particle beam exposure apparatus is roughly classified into a raster scanning method and a vector scanning method according to the deflection method.

In the raster scanning method, a deflection range is sequentially scanned using a scan instruction signal at a constant speed, and a desired figure is exposed by turning on a beam while scanning a range to be exposed. Hereinafter, this state is referred to as raster scanning exposure. FIG. 6 shows a raster scanning type exposure method. Patterns A and B to be exposed exist in the deflection range 600. The raster scanning method scans the entire deflection range sequentially,
While scanning on the patterns A and B, on / off of the blanking signal is controlled so as to turn on the beam. Thus, the raster scanning method scans the entire deflection range regardless of the presence or absence of a pattern.

Next, the vector scanning method will be described. FIG. 7 shows a vector scanning type exposure method in which a charged particle beam is generated in a spot (circle) shape and the spot beam is used. In the vector scanning method, exposure is performed while the spot beam is moved stepwise at a feed pitch that is set to a value smaller than the beam diameter. After the step movement is settled, the beam is turned on for a predetermined time to expose one dot, and this is repeated to expose the pattern.

FIG. 8 shows a vector scanning method using a variable shaped beam. The patterns A and B are finely decomposed and converted into shot figures. For example, the figure B is b1,
It is decomposed into b2, b3, b4, and the hypotenuse part b4 is
It is decomposed into shot figures having a value in which the unevenness of the hypotenuse can be ignored (for example, several tenths of μm or less). The charged particle beam is shaped into a shot pattern, and stepwise movement is performed to perform one shot exposure. This is repeated to expose the pattern.

Regarding the prior art, the following publicly known examples are given to improve the exposure accuracy of the hypotenuse. That is, regarding the raster scanning method, Japanese Patent Publication No. 53-24790 discloses that scanning exposure is performed in the linear characteristic region of the scanning line to improve the pattern accuracy at the end of the figure, and the scanning speed of the charged particle beam is changed from the start point of the exposure to the end point. The same scanning method is described.
The vector scanning method was devised in Japanese Patent Laid-Open No. 53-8004 for the purpose of accurately matching the timing of the blanking signal and the operation signal, and the correction data corresponding to the scanning speed was stored in the memory. , A method of correcting the delay of the scanning signal at the timing of the blanking signal is described. As the last variable shaped vector method, Japanese Patent Laid-Open No. 3-116922 discloses a method of improving the pattern accuracy by reducing the beam size on the hypotenuse area and exposing with a beam size larger than that on the areas other than the hypotenuse area. .

[0009]

In recent years, as LSIs have been highly integrated, the performance of semiconductor elements such as LSIs is determined by the pattern size, so that pattern processing accuracy of sub-micron or less is required. . In the charged particle beam exposure system, it is a problem to expose a semiconductor pattern at high speed and with high accuracy. The issues will be specifically described below.

The raster scanning method is advantageous in that since the charged particle beam is continuously scanned and exposed, the unevenness of the pattern in the scanning direction and the vertical direction is extremely small, and excellent processing accuracy can be obtained. However, the pattern parallel to the scanning direction has a problem that the exposure amount decreases at the position where the exposure starts and the position where the exposure ends, and the pattern becomes thin. In addition, since the entire deflection area is uniformly scanned, the exposure time becomes huge.

In the vector scanning method using the spot beam, the exposure pitch is set finer than the beam diameter and the exposure is sequentially performed. Therefore, the number of exposures becomes enormous with the miniaturization of the spot beam, which causes a decrease in throughput. There is. On the other hand, even with the vector scanning method using the variable shaped beam, a rectangle or the like can be pattern-exposed at high speed, but the hypotenuse portion shown by b4 in FIG. This is a cause of reduced throughput.

An object of the present invention is to expose a pattern in a charged particle beam exposure system at high speed and with high accuracy.

[0013]

In order to achieve the above object, a charged particle beam exposure apparatus of the present invention comprises a conventional exposure method employing a raster method or a vector method,
It also has a method of continuously raster-exposing the periphery of the pattern including the oblique side. This will be described with reference to FIG. FIG. 3 shows a state in which the exposure method of the present invention is carried out in a charged particle beam exposure apparatus which performs vector scanning with a spot beam. 201 to 205 are conventional exposure results in which the spot beam is exposed while being stepwise moved. Reference numerals 206 to 209 denote exposure portions of a method of performing raster scanning exposure around the pattern.

In order to realize the above-mentioned exposure method, the charged particle beam exposure apparatus of the present invention comprises a pattern data separating means for separating a portion for performing raster scanning exposure around a pattern from pattern data, and a raster scanning exposure. A coordinate calculation means for obtaining the coordinates of the start point and the end point, a means for generating a scanning instruction signal for raster scanning exposure of the pattern periphery, and an exposure amount that specifies the exposure amount for raster scanning exposure of the pattern periphery including the hypotenuse. And an exposure amount control means for controlling the scanning speed so as to coincide with.

In the raster scanning exposure, a flag for designating which side of the periphery is to be subjected to the raster scanning exposure by referring to the graphic code of the pattern data is provided, and the predetermined peripheral raster scanning is referred by referring to the flag. And a means for performing exposure.

Further, when performing raster scanning exposure around the pattern, a means for correcting the scanning instruction signal for performing the raster scanning exposure using the correction coefficient used when performing the internal exposure of the pattern is configured. .

[0017]

The present invention improves the processing accuracy by performing the raster scanning exposure along the periphery of the pattern.
In order to realize this, the charged particle beam exposure system of the present invention operates as follows. Note that the pattern data is composed of a rectangle having a figure origin (x, y) and a figure size a × b, and a case where raster scanning exposure is performed around the pattern with a spot beam having a radius d will be described.

The pattern data separating means separates a portion to be subjected to raster scanning exposure from the pattern data. The origin of the figure is (x + d, y + d) and the pattern size is (a-2
Calculation is performed so that d) × (b−2d). The origin of the figure shifts to the inside of the pattern, and the pattern size is separated only in the portion for raster scanning exposure. The pattern obtained by separating the portion for raster scanning exposure is exposed by a conventional vector method or raster scanning method.

Next, the operation of performing raster scanning exposure around the pattern will be described with reference to FIG. The coordinate calculation means adds the figure origin of the pattern data and the figure size to obtain the vertices (p1, p2, p3, p4) of the pattern. Furthermore, the coordinates (s) of the start and end points of the raster scanning exposure
1, e2), (s2, e3), (s3, e4), (s4
Calculate e1). Raster scanning exposure is performed at the start point and end point coordinates.

The exposure amount control unit calculates and obtains the scanning speed so that the exposure amount and the set value when performing raster scanning exposure become equal. The scanning speed is further converted into an integrated input voltage Vs because the scanning instruction signal is generated by the integrator. The integrator determines an integration constant based on the deflection sensitivity and the exposure amount, and integrates the integrated input voltage Vs to generate a scanning instruction signal that matches the set exposure amount.

This scanning instruction signal is connected to the analog inputs of two multipliers (multiplying digital / analog converters). Further, the digital inputs of the two multipliers are given by converting the coordinate components around the pattern into a digital code. As for the outputs of the two multipliers, one of them outputs an x-channel scanning signal and the other outputs a y-channel scanning instruction signal.
When performing raster scan exposure on the hypotenuse, for example, assuming that the angle between the x axis and the line for raster scan exposure is θ, the coordinate component in the x direction is 1, and the coordinate component of tan θ is given in the y direction to give a two-dimensional image. The scan instruction signal is generated. in this case,
Since the scanning speed is cos θ times, the integrated input voltage is cos θ
Calculate and set to 1 / min.

This two-dimensional scanning instruction signal is added to the figure origin (x, y) by the adding means to form an x, y two-dimensional scanning instruction signal for performing scanning exposure from an arbitrary position in the deflection area. .

Turning on / off the beam for raster scanning exposure
It is controlled by the blanking signal. At the same time when the scanning instruction signal is generated, a blanking signal for turning on the beam is generated, and when the coordinate component (x or y) of the raster scanning exposure coincides with the scanning instruction signal, a blanking signal for turning off the beam is generated.

The flag for designating the side of the pattern for raster scanning exposure is designed to input the graphic code and raster scan expose the side corresponding to the graphic code. For example, when the figure code is a trapezoid as shown in FIG. 3, only the oblique side can be raster-scan exposed. In this case, the pattern data separating means separates only the portion to be subjected to raster scanning exposure from the pattern data. By changing the contents of the flag, raster scanning exposure is performed by designating the entire periphery of the pattern or an arbitrary side.

The x, y two-dimensional scanning instruction signal for performing scanning exposure from an arbitrary position in the deflection area is corrected by using a circuit so as to perform a correction calculation using a conventional correction coefficient. . This correction circuit inputs an x, y two-dimensional scanning instruction signal and calculates a correction amount by a correction calculation circuit using a conventional correction coefficient. This correction amount and the x, y two-dimensional scanning instruction signal are analog-added to perform the correction.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is capable of performing raster scan exposure around a pattern in a charged particle beam exposure system of raster scan type or vector scan type.
Hereinafter, the present invention will be described in detail based on examples.

FIGS. 1 and 2 are block diagrams of a charged particle beam exposure system of the present invention configured such that the inside of a pattern is exposed by a vector method and the periphery of the pattern is subjected to raster scanning exposure. 3 and 4 show a pattern exposure method of the charged particle beam exposure system according to the present invention. Figure 2
FIG. 3 is a block diagram showing in detail a circuit configuration for performing raster scanning exposure along the periphery of a pattern. Hereinafter, description will be given with reference to the drawings.

The electron optical housing 103 of FIG. 1 is provided with a blanking plate for generating a charged particle beam, irradiating the beam to a desired position with an electron lens or a deflector, and controlling the beam on / off.

The control computer 100 includes a pattern memory 11
The pattern data is input from 0 and set in the conversion designation unit 101. The conversion designation unit 101 determines the graphic code of the pattern data and generates a scan flag. The scan flag is
This is a flag for designating the presence / absence of raster scanning exposure for each side of the pattern, and makes it possible to perform raster scanning exposure around the arbitrary pattern. The bit of the scan flag is determined and the corresponding raster scan exposure of the periphery is performed.

The pattern data separation unit 109 separates the portion for raster scanning exposure from the pattern data with reference to the scanning flag. A description will be given in combination with FIG. The pattern data separation unit 109 first adds the origin of the pattern data and the figure size to obtain the coordinate p of each vertex of the pattern.
1, p2, p3, p4 are obtained. Next, referring to the scan flag, the portion to be subjected to raster scan exposure is determined. Is c
It is separated into patterns having vertices p1, cp2, cp3, and cp4. The separated patterns are sequentially exposed by the vector scanning method.

In the above description, the case where all the sides of the pattern are scanned and exposed, but other than this, it is possible to perform the raster scanning exposure of any side of the pattern. In this case, the pattern separation unit 109 separates the portion to be raster-scan exposed by the scanning flag designating an arbitrary side.
The separated patterns are sequentially exposed by the vector scanning method. Raster scan exposure is performed on the side designated by the scan flag.

Next, the case of performing raster scanning exposure will be described in detail. The coordinate calculation means 104 in FIG. 1 calculates the coordinates of the start point and the end point of the raster scanning exposure from the coordinates of the vertices of the pattern. For example, when raster scanning exposure is performed on 207 in the direction perpendicular to the x axis in FIG. 3, the starting point coordinate s1 is (xp1-d,
yp1-d), where d is the beam radius. The end point e2 is calculated by (xp2-d, yp2 + d). Further, the exposure amount control unit 105 calculates the scanning speed (straight line inclination) when performing raster scanning exposure with the exposure amount of the pattern data.

The scanning signal generator 106 is composed of an integrator, a multiplication type digital / analog converter, and the like. The time constant of the integrator is determined by conditions such as exposure amount, deflection sensitivity, current density and the like. The integrator is configured to start integration from a negative offset potential and continuously increase the potential from negative to positive. The output of the integrator is connected to the analog inputs of the two multiplying digital / analog converters. To the digital inputs of the two multiplication type digital / analog converters, coordinate components around the pattern are converted into digital codes and then input.

The scanning instruction signal generator 106 will be described in detail with reference to FIG. In FIG. 2, 900 is an integrating circuit, 901 and 9
Reference numeral 02 is a digital / analog converter for setting the start point of raster scanning exposure, 903 is a digital / analog converter for setting the timing of turning on the beam, 904 is a digital / analog converter for setting the timing of turning off the beam, 905 And 906 are multiplication type digital / analog converters, 907 and 908 are adders for adding the scanning instruction signal and the starting point coordinates, 909 and 910 are adders, and 911 and 912 are means for setting coordinate components.

In FIG. 2, the digital input of the multiplication digital / analog converter 905 gives a digital code corresponding to the coordinate component 1 by setting 911 the coordinate component. Multiplying Digital / Analog Converter 906
In the digital input of, the digital code corresponding to tan θ is given by 911 which sets the coordinate component. 9
The output of the integrator 900 is connected to the analog inputs of 05 and 906. When the outputs of the multiplying type digital / analog converters 905 and 906 are combined, the scanning speed becomes the set value.
Since the scanning instruction signal is cosθ times, the exposure amount control unit 105 in FIG. 1 calculates the integrated input voltage / cosθ and supplies it to the integrator 900. In this way, a two-dimensional scanning instruction signal for the x and y axes is generated.

The scanning signal generator 106 is also realized by the following method. x-axis multiplication type digital / analog converter 9
A digital code corresponding to the coordinate component cos θ is given to 05, and the y-axis multiplication type digital-analog converter 906
Is given a digital code corresponding to the coordinate component sin θ, and the integrated voltage sets the value calculated by the exposure amount. As a result, a scanning instruction signal having a scanning speed that matches the set exposure amount can be obtained.

Multiplying Digital / Analog Converter 905
And the outputs of 906 are digital / analog converters 901.
And the output of 902 are added at 907 and 908, and x, y
A two-dimensional scanning instruction signal is obtained. As a result, raster scanning exposure is performed at an arbitrary angle from arbitrary coordinates.

The deflection distortion correction when performing raster scanning exposure will be described below. The two-dimensional scanning instruction signal is converted into a digital amount by the analog / digital converters 913 and 914, and correction calculation circuits 917 and 9 for performing a correction calculation with the deflection distortion correction coefficient used when exposing the inside of the pattern.
18 is input. Correction operation circuit 9 requires a predetermined time
The correction data output from 17, 918 are converted into analog correction amounts by digital / analog converters 919, 920. The delay calculators 915 and 916 include correction calculation circuits 91.
The delayed scanning instruction signal and the correction amount are input for the time required for operations of 7 and 918. As a result, the scanning instruction signal in which the deflection distortion correction is performed in real time is obtained.

Next, the blanking signal performs on / off control of the beam by comparing the output of the integrator of the scanning signal generator with the length of the pattern periphery. The digital / analog converter 903 in FIG. 2 corrects the timing difference between the scanning instruction signal and the blanking signal due to a delay in the response time of the blanking circuit when the scanning speed changes depending on the exposure amount. ing. For example, if the scanning instruction signal has an offset of several millivolts at the time of turning on the beam, the start point is displaced. Furthermore, when scanning at high speed, this positional deviation tends to increase. In order to prevent this, a correction value according to the scanning speed is set in the digital / analog converter 903 to correct the voltage generated by several millivolts to zero.

In the blanking control, the beam is turned on when the result of addition of the scanning instruction signal and the start point correction amount, that is, when the output of the adder 909 crosses zero volt, and then the scanning instruction signal and the length of the pattern periphery are set. , I.e., when the output of the adder 910 crosses zero volts, the beam is turned off.

An exposure method of the charged particle beam exposure system of the present invention using a variable shaped beam is shown in FIG. The rectangles 301 to 307 are exposed by normal vector scanning. The pattern data separation unit inputs the scan flag in which the bit indicating the hypotenuse portion is set, and separates the portion for raster scan exposure from the pattern data for exposure. Here, the case where only the oblique side is subjected to scanning exposure has been described, but other than this, it is possible to perform raster scanning exposure at any side of the pattern. In this case, the pattern separation unit 109 separates the portion to be raster-scan exposed by the scanning flag designating the corresponding side. The separated patterns are sequentially exposed by the variable shaped vector scanning method. Raster scan exposure is performed on each side of the pattern designated by the scan flag.

Now, a method of performing raster scanning exposure around the pattern in the charged particle beam exposure system which exposes the pattern by raster scanning will be described. FIG. 5 shows a situation in which the pattern 200 is exposed by the raster scanning method. In the exposure method of the present invention, the deflection area 600 is sequentially raster-scanned as shown by the dotted line, and the pattern data separation unit 1
A part 40 for scanning exposure from the pattern 200 according to 09
401 is obtained by separating 2 and 403 and is exposed. Further, raster scan exposure of the portions indicated by 402 and 403 is performed to expose the pattern 200.

In the charged particle beam exposure system, when performing raster scanning exposure around the pattern, it is possible to divide it into n times. In this case, the exposure amount is 1 / n
Is set, and the coordinates of the same start point and end point are controlled to perform raster scan exposure n times.

The beam shape in the case of raster scanning exposure is arbitrary, and it may be a spot shape or a rectangular shape. In any case, when performing raster scan exposure around the pattern, the pattern data separation unit 109 operates so that the portion corresponding to the shape of the beam for raster scan exposure is separated from the pattern data.

[0045]

According to the present invention, the periphery of the pattern is formed with high accuracy by the raster scanning exposure which is performed by continuously scanning along the periphery of the pattern. Further, since the scanning instruction signal is continuously generated, the pattern end portion is exposed at high speed without wasteful waiting time. Since the scanning speed around the pattern is controlled by the angle, a uniform exposure amount can be obtained. Therefore, the periphery of the pattern is formed with high accuracy.
Uniformity of the exposure amount can be improved by dividing the raster scanning exposure into n times and performing overlapping exposure. The position of the raster scanning exposure is controlled with high accuracy because the timings of the scanning instruction signal and the blanking signal are matched with each other with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram of a charged particle beam exposure system of the present invention.

FIG. 2 is an explanatory diagram showing a specific operation of the present invention.

FIG. 3 is an explanatory diagram of a pattern exposure method using a spot beam according to the present invention.

FIG. 4 is an explanatory diagram of a pattern exposure method using a variable shaped beam according to the present invention.

FIG. 5 is an explanatory diagram of a pattern exposure method by raster scanning according to the present invention.

FIG. 6 is a block diagram showing a raster scanning method.

FIG. 7 is an explanatory diagram showing a vector scanning system using a spot beam.

FIG. 8 is an explanatory diagram showing a vector scanning system using a variable shaped beam.

[Explanation of symbols]

Reference numeral 100 ... Control computer, 101 ... Conversion designation unit, 102 ... Sample stage control unit, 103 ... Electro-optical mirror body, 104 ... Coordinate calculation unit, 105 ... Exposure amount control unit, 106 ... Scan signal generation unit, 107 ... Blanking control Reference numeral 109, pattern data separation unit, 110, pattern memory, 111, figure decomposition unit, 112, correction calculation unit, 113, drive unit, 114, lens power supply, 115, signal processing unit.

Claims (3)

[Claims] 1. A deflection data control means for converting an exposure pattern into deflection data, a deflection driving means for applying the deflection data to a deflector, an electron optical housing for generating a charged particle beam and deflecting it to a desired position, In a charged particle beam exposure apparatus equipped with a sample stage for controlling the movement of the sample position and sample stage control means, and a control computer for controlling the entire system, the exposure pattern data is decomposed into a plurality of basic patterns, Pattern data for designating the type of basic figure, origin coordinates, figure size, and pattern data composed of exposure amount; means for scanning exposure of a beam along the periphery of the basic figure having a predetermined angle; A means for controlling the scanning speed corresponding to a predetermined angle of the basic figure, and a means for exposing the portion for scanning exposure by separating from the pattern data. Charged particle beam exposure apparatus. 2. A flag means for instructing to perform scanning exposure of a predetermined periphery in accordance with a graphic code of pattern data, and means for performing scanning exposure by referring to said flag means. A charged particle beam exposure apparatus comprising: means for performing exposure by separating the corresponding peripheral scanning exposure portion from pattern data by referring to the flag means. 3. The scan instruction signal for performing raster scan exposure around a pattern according to claim 1 or 2, wherein raster scan exposure around the pattern is performed using a correction coefficient used when performing an internal exposure of the pattern. A charged particle beam exposure apparatus comprising: means for obtaining a correction amount of a scanning instruction signal, and means for adding the correction amount and the scanning instruction signal to correct the scanning instruction signal.