JP2786671B2 - Charged beam drawing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a charged beam for drawing a pattern of a semiconductor integrated circuit such as an LSI on a sample such as a mask or a wafer with high speed and high accuracy. The present invention relates to a drawing method, and more particularly to a charged beam drawing method for improving a drawing throughput by optimizing a table moving speed.

(Prior Art) In recent years, LSI patterns have become increasingly finer and more complex, and electron beam lithography systems have been used as devices for forming such patterns. When drawing a desired pattern using this apparatus, it is not possible to supply design pattern data created using an LSI pattern design tool such as CAD as drawing pattern data of the above-described drawing apparatus in the same format. Can not. The reasons are summarized as follows.

The design pattern data is generally represented by a polygon, whereas the data supplied to the electron beam drawing apparatus is limited to basic figures such as trapezoids and rectangles.

If the figures overlap each other, multiple exposure is performed, and the drawing accuracy deteriorates.

The data supplied to the electron beam lithography must be divided into unit lithography areas according to the lithography method.

Therefore, the design data is subjected to, for example, contouring processing to remove multiple exposure portions, and then divided into basic figures such as rectangles and trapezoids for each unique unit drawing area (frame area) determined by the beam deflection area. In this way, the graphic data is made acceptable to the electron beam drawing apparatus. Through these steps, drawing pattern data relating to the integrated circuit is generated, and this data is stored in a storage medium such as a magnetic disk.

In the drawing process, the drawing pattern data is read out for each frame area and temporarily stored in a pattern data buffer. This data is decoded, and a basic figure is formed into a group of drawing unit figures that can be formed by the beam forming means. To divide. Then, while controlling the beam position and the beam shape based on the result, the table on which the sample is placed is continuously moved in the X direction or the Y direction to draw a desired pattern in the frame area. Next, the table is moved stepwise in the direction orthogonal to the continuous movement direction by the width of the frame area, and the above processing is repeated to perform the drawing processing of the entire desired area.

In the two-stage deflection system in which the main deflection unit determines the sub-deflection position and performs the drawing by the sub-deflection unit, a frame region is formed by an aggregate of unit drawing regions (sub-fields), and the width of the frame region is mainly determined. It is defined by the beam deflection width of the deflection means. Also in this drawing method, drawing pattern data is read out for each frame area in the same manner as described above, and drawing processing is performed while continuously moving the table.

As described above, in the drawing process, the table moving speed when drawing the frame area is determined by the patterning time of all the drawing unit figures in the frame area (the time for drawing the desired pattern by controlling the position and shape of the beam). In the case of the two-stage deflection method, in addition to this, the positioning time of all the unit drawing areas is
If the value does not sufficiently follow the table moving speed, drawing becomes impossible. The following two methods have been used to determine the table moving speed that satisfies this condition.

At the time of drawing in the drawing stripe region, an extremely low table moving speed is set so that patterning can sufficiently follow the table moving speed, and drawing processing is performed at the moving speed over the entire frame region.

Prior to the actual drawing process of a mask or a wafer, a table moving speed that does not cause a patterning error (an error that occurs when the patterning process cannot follow the table moving speed) is tried for each drawing stripe region constituting the drawing region. It is found and set by the AND error method, and the drawing process is executed at the table moving speed.

However, this type of method has the following problems. That is, when determining the table moving speed when drawing the frame area, in the method of determining the table moving speed by the above-described method, most of the drawing stripe area which is a set of frame areas constituting the LSI chip is used. It is necessary to set a value equal to or less than the table moving speed at which the drawing stripe region having a high pattern density can be drawn without error. In a frame region other than the drawing stripe region, drawing is performed at an unnecessarily low table moving speed. An extremely large amount of time is wasted in drawing the entire area.

On the other hand, in the method (1), it is possible to perform a less wasteful drawing process for each of the drawing stripe regions constituting the drawing region. However, in order to determine the table speed, a mask or a wafer to be drawn is set on the table. As a pre-process for mounting on the drawing stripe, it is necessary to determine the table moving speed that can minimize waste of drawing time by repeating trial and error for each drawing stripe region. The time spent in the above steps in the entire drawing process is not negligible, and in some cases, the time required for determining the table moving speed is longer than the time required for the actual drawing process. It is possible.

Under such circumstances, in the current writing process, the writing time is increased, that is, the writing throughput is reduced due to the method of determining the table moving speed of each writing stripe region. As described above, the problem is that the rapid progress of the electron beam lithography system has a large effect on the improvement of the reliability and the operation rate of the LSI pattern drawn by the electron beam lithography system due to the miniaturization and improvement of the integration degree of the pattern. It is a hindrance.

(Problems to be Solved by the Invention) As described above, conventionally, when drawing is performed at a sufficiently low table moving speed that does not cause a drawing error and a drawing defect, a drawing time loss is large and a drawing throughput is significantly reduced. On the other hand, in the drawing step of finding and drawing the table moving speed that minimizes the loss of the drawing processing, time is spent in the pre-processing step of determining the table moving speed, and the time of the entire drawing step is reduced. This results in a longer time, and there is a problem that the drawing throughput also decreases.

Further, the above problem is not limited to the electron beam writing method, but can be applied to a general charged beam writing method for forming a desired pattern on a sample using a charged beam such as an ion beam.

The present invention has been made in consideration of the above-described circumstances, and has as its object to achieve a substantially optimum table moving speed in consideration of pattern density without reducing the time required for actual drawing processing. Provided is a charged beam writing method which can be determined for each writing stripe region, can easily determine a substantially optimum table moving speed without actually moving the table, and can improve the writing throughput. Is to do.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is a beam positioning control obtained by decoding drawing pattern data related to a writing stripe region to be written independently of an actual writing process. The signal, the beam shaping control signal, and the monitor signal of the pseudo table position generated according to the set value of the table moving speed make it possible to determine the table moving speed at which drawing can be performed without drawing errors without actually driving the table. Is to decide.

That is, the present invention divides a drawing area, which is a set of LSI chips arranged on a sample, into a drawing stripe area determined by a beam deflection width of a beam deflecting device, and The drawing pattern data in which the position and the figure shape are defined are read from the storage medium, and while the drawing pattern data is being decoded, the drawing unit figures are formed into a drawing unit figure group that can be formed by the beam forming means, and the table on which the sample is placed is placed in the X direction. Alternatively, in the charged beam drawing method of drawing a desired pattern by controlling the beam deflecting means while continuously moving in the Y direction to control the position and shape of the beam, driving the table prior to actual drawing processing. The drawing pattern data is decoded to make a drawing unit figure, and a positioning signal and a beam of the drawing unit figure are read. A beam shaping signal for controlling the shape is sent to the beam deflecting means and a deflection control unit for driving the beam shaping means to virtually perform beam positioning and beam shaping, and a table obtained when the table is driven. A monitor signal of a table that changes according to the moving speed is simulated, and a process of determining whether or not the drawing stripe region can be drawn at a predetermined table moving speed is repeated to actually perform the drawing process. This is a method for determining the table moving speed (claim 1).

Further, the present invention provides at least one of decoding means for decoding the drawing pattern data to be a group of drawing unit figures used for actual drawing processing and the like and for determining the table moving speed prior to the drawing processing. In this method, two types are provided so that the actual drawing process and the determination of the table moving speed can be performed independently of each other (claim 2).

(Operation) According to the method of the first aspect of the present invention, according to the beam control signal (the beam positioning signal and the shaping signal) and the set value of the table speed without driving the table on which the sample is placed. Determining whether or not drawing is possible at the table setting speed based on a pseudo monitor signal of the table position obtained by analyzing the timing of the beam positioning signal and the monitor signal to determine a substantially optimum table moving speed. Can be.

As a result, it is possible to increase the operation rate of the charged beam writing apparatus and to improve the productivity of the LSI. In addition, the above-described drawing method is expected to exhibit more effective effects on miniaturization of patterns and improvement of integration with the rapid progress of LSI in the future.

According to the method of the second aspect of the present invention, the actual drawing processing and the above-described table speed determination processing can be performed independently, and the drawing processing is performed without any reduction in the actual drawing processing time. It is possible to further increase the operation rate of the charged beam writing apparatus and the productivity of the LSI.

(Examples) Hereinafter, details of the present invention will be described with reference to the illustrated examples.

FIG. 1 is a schematic configuration diagram showing an electron beam writing apparatus used in a method according to one embodiment of the present invention. In the figure, reference numeral 10 denotes a sample chamber, in which a table 12 on which a sample 11 such as a semiconductor wafer or a glass mask is placed is accommodated. The table 12 is driven by a table driving circuit 13 in the X direction (left and right directions on the paper) and the Y direction (front and back directions on the paper). The moving position of the table 12 is measured by a position circuit 14 using a laser length meter or the like.

Above the sample chamber 10, an electron beam optical system 20 is arranged. The optical system 20 includes an electron gun 21, various lenses 22 to 26,
It comprises a blanking deflector 31, a beam size varying deflector 32, a beam scanning main deflector 33, a beam scanning sub deflector 34, and beam shaping apertures 35 and 36.
The main deflector 33 is used to position a predetermined unit drawing area (sub-field), the sub-deflector 34 is used to position the figure drawing position in the sub-field, and the beam size changing deflector 32 and the shaping aperture 35 are used. , 36, the table 12 is continuously moved in one direction, and a drawing stripe area is formed by collecting frame areas obtained by dividing the LSI chip into strips according to the beam deflection width. Further, the table 12 is step-moved in a direction orthogonal to the continuous direction, and the above processing is repeated to sequentially draw each drawing stripe region.

On the other hand, the control computer 40 has a magnetic disk (storage medium) 41.
The disk 41 stores LSI chip data (drawing pattern data of the LSI chip and layout data describing the layout position of the chip on the sample). The chip data read from the magnetic disk 41 is temporarily stored in a pattern memory (data buffer unit) 42 as drawing pattern data for each drawing stripe area. The drawing pattern data for each drawing stripe stored in the data buffer unit 42, that is, drawing stripe information including a drawing position and basic graphic data,
The data is decoded by a pattern data decoder 43 and a drawing data decoder 44 which are data decoding units, and a blanking circuit 4
5, sent to the beam shaper driver 46, main deflector driver 47 and sub deflector driver 48.

That is, the pattern data decoder 43 receives the above data, and performs inversion processing on the graphic data included in the drawing stripe area as necessary to generate inverted pattern data. Then, the basic figure data defined as the drawing stripe data is divided into drawing unit figure groups that can be formed by the combination of the shaping apertures 35 and 36, and beam control data is created based on this data. It is sent to the ranking circuit 45. Then, desired beam size data is created, and the beam forming control data is sent to the beam shaper driver 46. Next, a predetermined deflection signal is applied from the beam shaper driver 46 to the beam size changing deflector 32 of the optical system 20, whereby the size of the electron beam is controlled.

In the drawing data decoder 44, positioning data of a subfield is created based on the drawing stripe data, and a predetermined signal is applied to the data from the main deflector driver 47 to the main deflector 33 of the optical system. As a result, the electron beam is deflected and scanned to a designated subfield position. Further, the drawing data decoder 44 generates a sub-deflector scanning control signal, and this signal is sent to the sub-deflector driver 48. Then, a predetermined sub-deflection signal is applied from the sub-deflector driver 48 to the sub-deflector 34, whereby drawing for each sub-field is performed.

Next, an electron beam writing method using the above-configured apparatus will be described. FIG. 2 shows a process of generating data for performing a drawing process. The LSI pattern is
Normally, a CAD system is designed and created for each LSI chip area, and the design pattern data is converted into drawing pattern data by the host computer. Then, the drawing pattern data is read out to perform the electron beam drawing.

Here, the data created by the CAD system usually has a figure data system in which the pattern is constituted by a group of polygonal figures and the patterns are allowed to overlap each other. In order to make LSI pattern data of such a format a graphic data system that can be accepted by an electron beam lithography system,
The host computer performs a contouring process on the figure to remove the multiple exposure area of the beam, and then, as shown in FIG. 3A, the area of the LSI chip is a unit drawing area which is deflected by the beam. The area is divided into frame areas 53a to 53d and a subfield area 54. FIG. 3B shows a drawing figure in a subfield area 54 which is made into polygons 51 and 52 by removing the beam multiple exposure area. Next, this drawing figure is subjected to figure division processing into a basic figure group 56 composed of rectangular and trapezoidal figures as shown in FIG. 3 (c).

The graphic data obtained by such a data generation process is represented by a graphic shape flag, a graphic position, and a graphic size,
The data is defined as a group of graphic data in units of a subfield area and a frame area and stored in the magnetic disk 41.

Then, as shown in FIG. 4, the drawing pattern data created through such a data generation process is selectively transferred from the LSI chips included in the drawing area to the chips having the same position in the step moving direction of the table. Take out. Further, the magnetic disk 41 is used as a unit area which can be drawn by one table movement for each drawing stripe area (shaded area) formed by collecting only frame areas having the same position in the step moving direction of the table from the chip group. To be drawn. However, the pattern density of the graphics included in the drawing stripe region varies significantly depending on the type of the LSI chip and the region within the chip. Accordingly, the time required for patterning differs for each drawing stripe region in the drawing region, and accordingly, it is desired to optimize the table moving speed at the time of patterning set for each drawing stripe region from the viewpoint of improving the drawing throughput. .

Therefore, the pattern memory 42 used when reading the basic graphic data divided into the frame area and the subfield area as shown in FIG. The drawing pattern data of the drawing stripe area read from the magnetic disk 41 is temporarily stored in a separately prepared pattern memory 42 'as shown in FIG. Then, as in the case where the actual drawing processing is performed by the pattern data decoder 43 ', the data is used as an aggregate of drawing unit figures 59 which can be formed by combining the forming apertures 57 and 58 as shown in FIG. The drawing position S1 is sent to the table speed determination circuit 70 for each unit drawing figure. On the other hand, the drawing data decoder 4
Similarly, at the time of actual drawing processing, the drawing pattern data stored in the pattern memory 42 'is read out for 4' and the drawing position S2 of the subfield is determined by the table speed determination circuit.
Send to 70. Then, in the table speed determination circuit 70,
The optimum value of the table speed is determined based on S1 and S2 and the table moving speed set value S3 output from the control computer 40.

Here, the specific configuration and operation of the table speed determination circuit 70 will be described in detail. The table speed determining circuit 70 stores the table moving speed set value S3 in the speed register 71 as shown in FIG. 7, and indicates the table position in a pseudo manner by an operation start command from the control computer according to the speed set value. The count value of the position counter 72 is counted up at a constant speed. On the other hand, the drawing pattern data stored in the pattern memory 42 'is decoded, and the relative table position (position in the continuous moving direction) from the frame origin for each subfield is input to the table speed determination circuit 70 for each subfield area. S2 is input from the drawing data decoder 44 'to the addition circuit 73 via the synchronization circuit 77. Furthermore, the relative drawing position S1 from the subfield area origin for each unit drawing figure
Is input from the pattern data decoder 43 'to the addition circuit 73 via the synchronization circuit 77 in the same manner as described above.

S1 + S2 obtained by adding the above S1 and S2 is a relative table position (position in the table continuous movement direction) from the frame origin for each drawing unit figure, and this value is input to S1 from the pattern data decoder 43 '. Each time it is performed, it is calculated by the adding circuit 73. Then, the addition value (S1 + S2) of the addition circuit 73 is input to the subtraction circuit 74 together with the count value S4 of the position counter 72, and the difference S5 (S5 = S4) between the relative table position (S1 + S2) and the pseudo table position S4. − (S1 + S2)) subtraction circuit
Calculate at 74.

The difference data S5 obtained as a result is sent to the comparison circuit 75, and the comparison circuit 75 calculates the minimum value Smin of the difference data held in the latch circuit 76 up to the present time (in the case of a negative value, the absolute value is increased). The above S5 is compared, and only when S5 is smaller than Smin, S5 is set as Smin and the data of the latch circuit 76 is updated. Such processing is performed on all the unit drawing figures included in the drawing stripe area, and a value at which the difference between the drawing position and the table position is the minimum is obtained at the table speed set.

Further, in the comparison circuit 75, when the above S5 is larger than 0,
It is assumed that the table position is not reached to the position to be drawn, and the synchronization circuit 77 is controlled according to the value of S5 to delay the processing for the next unit drawing figure. Also, S5
Is not greater than 0, the synchronization circuit 77
Sends S1 and S2 to the addition circuit 73, and then sends the next S1 and S2 to the addition circuit 73 after a certain time delay according to the value set by the control computer 40.

This delay time is equal to S2 from the drawing data decoder 44 '.
Is input, this corresponds to the positioning settling time of the subfield position, and when S1 is input from the pattern data decoder 43 ', the positioning settling time of the unit drawing figure and the beam irradiation time are calculated. Although this is a time corresponding to the added value, if the data decoding time of the pattern data decoder 43 'and the drawing data decoder 44' is longer than the above-mentioned delay time, this delay time is not necessary effectively,
The decoding time becomes a substantial delay time.

The value of Smin in one drawing stripe region obtained in this way is taken into the control computer 40 to determine whether or not it can be included in a predetermined deflection field, and a drawing error occurs at the set table moving speed. It is possible to determine whether or not drawing is possible, and to calculate a substantially optimum table moving speed from the value of Smin.

In other words, if the value of Smin is negative, it means that the provisionally set table speed is too high.
Is positive, it means that the table can be moved at a higher speed, so the table speed set temporarily is corrected according to the value of Smin, and the table movement speed used for the actual drawing process is corrected. Is determined for each drawing stripe. By setting the table moving speed obtained in the above-described processing steps as a provisional value of the table moving speed and performing the above-described series of processing again, a “more optimal” table moving speed can be obtained. This reprocessing is particularly effective when the provisionally set table moving speed is low (S> 0).

By the processing steps as described above, the table moving speed for each drawing stripe constituting the drawing area is determined, and the drawing processing is performed based on the table moving speed.
The drawing process can be performed at high speed without affecting the actual drawing process time at all, and as a result, the throughput of the drawing process can be improved and the productivity of the LSI can be improved.

Thus, according to the method of the present embodiment, when determining the table speed of the drawing stripe region, which is a unit region that can be drawn by one continuous table movement, the pattern memory, the pattern data decoder and the drawing data decoder used in the actual drawing process are used. By preparing two formulas and performing parallel processing with the actual drawing processing, it is possible to determine the optimum table moving speed without any waste time without any influence on the drawing time.
In addition, the table speed determination process does not involve actual table driving, and does not involve trial and error many times while further changing the table moving speed setting. An optimal moving speed can be determined. Therefore, it is possible to significantly reduce the dead time in the drawing process, improve the drawing speed, and increase the operation rate of the charged beam drawing apparatus.

The present invention is not limited to the embodiments described above. For example, the means for storing the drawing pattern data is not limited to a magnetic disk, but may be another storage medium such as a magnetic tape or a semiconductor memory. Further, the preprocessing for determining the table moving speed from the drawing pattern data related to the drawing stripe area may be performed not by the control computer but by the host computer that performs the data conversion processing. Instead, determine the table moving speed for each frame area that composes the LSI chip by the above method, and select the slowest table moving speed from the table moving speeds of the frame areas that compose the drawing stripe area when drawing. The drawing process may be performed. Furthermore, data Sm used for determining the table moving speed
In may not be obtained for each unit drawing figure, but may be obtained for each subfield area, and the table speed may be determined in consideration of a margin value for the calculated table speed.

Further, the configuration of the electron beam lithography apparatus is not limited to what is shown in FIG. 1 and can be changed as appropriate. Although the embodiment has been described by taking an electron beam as an example, the invention is not limited to the electron beam but can be applied to a charged beam such as an ion beam or a laser beam. In addition to the one-stage deflection method,
A deflection method having more than two stages may be used, and a shot method using a variable shaped beam and an apparatus method using a circular beam can be applied.

Further, the drawing pattern data stored in the storage medium is not limited to the figure system of the basic figure, but is applicable to a drawing unit figure and a polygon figure. In addition, various modifications can be made without departing from the scope of the present invention.

[Effects of the Invention] As described above in detail, according to the present invention, independently of actual writing processing, a beam positioning control signal obtained by decoding writing pattern data relating to a writing stripe region to be written, By using the beam shaping control signal and the monitor signal of the pseudo table position generated according to the set value of the table moving speed, the table moving speed at which drawing can be performed without drawing error without actually driving the table is determined. Therefore, it is possible to determine a substantially optimum table moving speed for each drawing stripe region in consideration of the pattern density without reducing the time required for the actual drawing process, and without actually moving the table. It is possible to easily determine a table moving speed that is almost optimal for the above, and it is possible to increase the drawing speed and improve the drawing throughput.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an electron beam lithography apparatus used in the method of one embodiment of the present invention, FIG. 2 is a schematic diagram showing a generation process of lithography pattern data, and FIG. Schematic diagram showing pattern division and region division of
FIG. 4 is a schematic diagram for explaining a drawing stripe region,
FIG. 5 is a block diagram showing the configuration of a main part of the present invention, FIG. 6 is a schematic diagram for explaining a graphic system of drawing unit graphics, and FIG. 7 is an internal configuration diagram of a table speed determination circuit. 10 ... Sample chamber, 11 ... Sample, 12 ... Table, 20 ... Electronic optics, 21 ... Electron gun, 22-26 ... Lens, 31-34 ... Deflector, 35,36 ... Beam Forming aperture, 40 ... Control computer, 41 ... Magnetic disk (storage medium), 42,42 '... Pattern memory, 43,43' ... Pattern data decoder, 44,44 '... Drawing data decoder, 45 ... ... Blanking circuit, 46-48 ... Deflector driver, 51,52 ... Design pattern, 53a-53d ... Frame area, 54 ... Subfield area, 56 ... Basic figure, 70 ... Table speed judgment circuit , 71: Speed register, 72: Position counter, 73: Addition circuit, 74: Subtraction circuit, 75: Comparison circuit, 76: Latch circuit, 77: Synchronization circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/027 G03F 7/20

Claims (3)

(57) [Claims] A drawing area, which is a set of LSI chips arranged on a sample, is divided into drawing stripe areas of a predetermined width, and writing pattern data is read from a storage medium for each of the writing stripe areas, and the writing pattern data is read out. The beam is deciphered into a drawing unit figure group that can be formed by the beam shaping unit, and the beam is positioned by the beam deflecting unit and the beam shaping unit while the table on which the sample is placed is continuously moved in one direction for each of the drawing stripe regions. In a charged beam drawing method for controlling a shape and drawing a desired pattern, prior to actual drawing processing, the drawing pattern data is decoded for each drawing stripe area to generate a drawing unit figure group, and the drawing is performed. Based on a positioning signal for each unit figure and a pseudo monitor signal of the table position obtained when the table is driven. Then, the deviation amount between the drawing position and the table position for each drawing unit figure is calculated, and the drawing stripe region can be drawn at a predetermined table moving speed from the relationship between the deviation amount and the deflectable area by the beam deflecting means. Or not, and determining an optimum table moving speed for each writing stripe region based on the result of the determination. 2. The decoding means for decoding the drawing pattern data to form a drawing unit figure group includes at least two sets of means for use in actual drawing processing and means for determining the table moving speed prior to the drawing processing. 2. The charged beam writing method according to claim 1, further comprising: independently performing an actual writing process and determining the table moving speed. 3. A table used for an actual drawing process by correcting a predetermined table moving speed provisionally set according to the shift amount based on a minimum value of the shift amount in one drawing stripe area. 2. The charged beam drawing method according to claim 1, wherein the moving speed is determined.