JP2006108447A - Charged particle beam lithography device and lithography method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently suppress-dimensional fluctuations caused by resist heating without waste and maintaining high accuracy and high throughput. <P>SOLUTION: The charged particle beam lithography device is provided with a deflector 14 for varying beam dimension, which forms a variable-forming beam, by controlling the shape and the dimension of a charged beam emitted from a charged beam source 6, a pattern data decoder 23 for dividing a pattern to be drawn on the resist on a sample 2 into a plurality of shot figures which can be formed with the deflector 14 for varying a beam dimension, an area recognizing unit 30 for detecting an area for each shot figure, and a drawing data corrector 31 which reconstructs each shot figure so that the area to be detected for each shot figure approximates the preset maximum area. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charged beam drawing technique for drawing a pattern such as an LSI on a sample such as a mask or a wafer, and more particularly to a variable shaped beam type charged beam drawing apparatus and drawing method.

  In recent years, LSI patterns have become increasingly fine and complex. Accordingly, the accuracy required for the pattern on the mask is becoming strict, and an electron beam lithography apparatus for mask production with high resolution is required. In order to realize the high resolution of the electron beam drawing apparatus, it is effective to increase the beam acceleration voltage and the beam current density.

  On the other hand, increasing the acceleration voltage and increasing the current density of the electron beam lithography apparatus causes a phenomenon called resist heating. Resist heating is a phenomenon in which energy obtained by subtracting energy required for resist exposure from energy transported to a resist by an electron beam is accumulated as heat, resulting in local sensitivity change. The fact that the mask material is glass with poor thermal conductivity is another factor that amplifies this phenomenon.

  Sensitivity changes due to resist heating are observed as dimensional changes. This is shown in FIG. FIG. 6A shows a line and space drawn inside the subfield 60. In the drawing order, the X direction is from left to right, and the Y direction is from bottom to top. FIG. 6B shows the result of measuring the dimensions in the subfield 60 two-dimensionally. It can be seen that as the drawing is later in time, the heat of the portion drawn before that is affected, so that the dimensions are thicker toward the back than the front.

  As a first conventional technique for reducing this sensitivity change, there is a multiple drawing technique in which a dose required for resist exposure is divided into a plurality of patterns and patterns are overlapped with each dose. However, even if multiple drawing is performed, it cannot be said that the amount of dimensional change is sufficiently reduced, and it is necessary to further reduce the amount of dimensional change because of the demand for higher accuracy.

  As a second conventional technique, there is a method of limiting the maximum shot size at the time of drawing. FIG. 7 is a graph showing the relationship between the shot size (Sx = Sy) of the variable shaped beam 73 and the size variation in the subfield, using the line and space drawing area ratio inside the subfield as a parameter. 70 is a drawing area ratio of 25%, 71 is a drawing area ratio of 50%, and 72 is a drawing area ratio of 70%. It can be seen that the dimensional variation increases as the drawing area ratio and the shot size increase. In this example, in order to minimize the dimensional variation, the maximum shot size may be limited to 0.25 [μm].

  However, the limitation on the maximum shot size is advantageous for manufacturing a high-accuracy mask, but causes a decrease in productivity, that is, throughput.

  As a third conventional technique, there is a method of extending the settling time of a deflection amplifier or the like. The settling time is the time required for an electric circuit such as an amplifier to be stabilized, and corresponds to the time between shots from the viewpoint of drawing. If the time interval between shots is long, that is, if the settling time is long, the heat generated in the resist diffuses, and the amount of dimensional variation due to resist heating can be reduced. Therefore, it is possible to relax the limit of shot size while maintaining accuracy.

However, in this method, since the same settling time is set for all shots, useless time is generated. A pattern including oblique line approximation as shown in FIG. 8 is typical. In this figure, 80 is a maximum size shot that minimizes resist heating at the settling time t ₀ , and 81 is a size shot that can ignore resist heating. The number of 80 shots is 8, and the number of 81 shots is 22. When the settling time is uniformly imposed, the drawing time of this pattern is T, where T is the electron beam irradiation time of this pattern,
T + (8 + 22) × t ₀ (1)
It is. However, since the resist shot can be ignored in the 81 shot at the settling time t ₀ , the third term of the equation (1) includes a waste time.

As a fourth conventional technique, there is a method of changing the settling time in accordance with the shot size (see, for example, Patent Document 1). FIG. 9A shows the relationship between the shot instruction timing signal and the settling time. Even if the shot instruction comes at time t ₀ , the shot cannot actually be made until the signal is stabilized. If a shot is taken at time t ₂ after the signal has stabilized, t ₂ -t ₀ is the settling time. According to this figure, it is understood that there is a lower limit (t ₁ −t ₀ ) in setting the settling time because the shot cannot be performed faster than time t ₁ . Therefore, as shown in FIG. 9B, when the shot size is smaller than S ₀ , the settling time becomes constant. In other words, the throughput reaches its peak.
JP 2001-189262 A

  As described above, various drawing methods or drawing apparatuses have been proposed in the past, and their drawbacks have been clarified. However, there are still no effective methods for further improving drawing accuracy and improving throughput.

  That is, in the first prior art, dimensional variation due to resist heating has been reduced by applying multiple drawing, but it has become necessary to further suppress dimensional variation along with a demand for higher mask accuracy. The second prior art has a problem in that the productivity, that is, the throughput is lowered in order to limit the maximum shot size so as to suppress the dimensional variation due to resist heating to a desired accuracy. In the third conventional technique, the settling time of an amplifier or the like, in other words, the time interval between shots is extended to improve both accuracy and high throughput, but the dead time increases with a pattern containing many small shots. There was a problem of doing. The fourth prior art has a problem that there is a lower limit even if the settling time is made variable, which limits the throughput.

  The present invention has been made in consideration of the above circumstances, and the object of the present invention is to maintain a high accuracy and a high throughput and to effectively prevent dimensional variation caused by resist heating without waste. It is an object to provide a beam drawing apparatus and a drawing method.

  In order to solve the above problems, the present invention adopts the following configuration.

  That is, the charged beam drawing apparatus according to one aspect of the present invention controls the shape and size of the charged beam emitted from the charged beam source and forms a variable shaped beam, and draws on the resist on the sample. Means for dividing a power pattern into a plurality of shot figures that can be shaped by the beam shaping means; means for detecting the area of each shot figure; and a maximum area in which the area of each shot figure to be detected is predetermined. Means for reconstructing each of the shot figures so as to be close to each other.

  Further, a charged beam drawing apparatus according to another aspect of the present invention includes a beam shaping means for shaping a variable shaped beam by controlling the shape and size of a charged beam emitted from a charged beam source, and drawing on a sample. Means for dividing a power pattern into a plurality of shot figures that can be shaped by the beam shaping means, means for detecting the area of each shot figure, and the area of each shot figure to be detected is one shot figure. Each shot figure is reconstructed so that the dimensional variation due to resist heating, which is determined by the settling time until the next beam is drawn to draw the next shot figure after the beam irradiation for drawing, approaches the maximum value that can be ignored. And means.

  According to the present invention, the area of the shot figure obtained by dividing the pattern to be drawn on the sample is detected, and the shot figure is reconstructed in accordance with this area, so that the area of the shot figure is resist-heated. Dimensional variation due to can be brought close to the maximum value that can be ignored. For this reason, it is possible to maintain high drawing accuracy and high throughput, and to efficiently suppress dimensional variations caused by resist heating.

  The details of the present invention will be described below with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 is a schematic diagram showing a schematic configuration of a variable shaped beam type electron beam drawing apparatus according to a first embodiment of the present invention.

  In the figure, reference numeral 1 denotes a sample chamber. A stage 3 on which a sample 2 such as a mask substrate is placed is accommodated in the sample chamber 1. The stage 3 is driven in the X direction (left and right direction on the paper surface) and Y direction (front and back direction on the paper surface) by the stage drive circuit 4 under a command from the control computer 20. The moving position of the stage 3 is measured by the position detection circuit 5 using a laser length meter or the like, and the measurement information is input to the control computer 20.

  An electron beam optical system 10 is installed above the sample chamber 1. The electron beam optical system 10 includes an electron gun 6, various lenses 7, 8, 9, 11, 12, a blanking deflector 13, a beam size variable deflector 14, a beam scanning main deflector 15, and a beam scanning. The auxiliary deflector 16 and two beam shaping apertures 17 and 18 are included.

  Then, the main deflector 15 positions a predetermined sub-deflection region (subfield) on the sample 2, and the sub-deflector 16 positions the figure drawing position in the sub-field, and the beam size variable deflector 14 and The beam shape is controlled by the beam shaping apertures 17 and 18, and the subfield is drawn while the stage 3 is continuously moved in one direction. In this way, when drawing of one subfield is completed, the process proceeds to drawing of the next subfield. Further, when drawing of a frame which is a set of a plurality of subfields is completed, the stage 3 is moved stepwise in a direction orthogonal to the continuous movement direction, and the above processing is repeated to sequentially draw each frame region.

  Here, the frame is a strip-shaped drawing region determined by the deflection width of the main deflector 15, and the subfield is a unit drawing region determined by the deflection width of the sub-deflector 16.

  On the other hand, the control computer 20 reads the mask drawing data recorded on the magnetic disk 21 as a storage medium, and the read drawing data is temporarily stored in the pattern memory 22 for each frame area.

  The drawing data for each frame area stored in the pattern memory 22, that is, the frame information composed of the drawing position and drawing graphic data, etc. is recognized through the pattern data decoder 23 and the drawing data decoder 24 which are data analysis units. To the unit 30, the main deflector driver 27, and the sub deflector driver 28.

  The pattern data decoder 23 creates desired beam shape data (shot figure) based on the drawing data, and sends the beam shape data to the area recognition unit 30. That is, desired beam shape data is created based on the drawing data, and the beam shape data is sent to the area recognition unit 30.

  The area recognition unit 30 calculates the area from the beam shape data, and this information is sent to the drawing data correction unit 31. In the present embodiment, the area recognition unit 30 and the drawing data correction unit 31 are separately provided, but may be integrated. The drawing data correction unit 31 reconstructs drawing data so that the beam shape does not exceed the maximum area based on the maximum surface precision information corresponding to the type of resist and substrate transferred from the control computer 20. Then, these correction data are sent to the deflection control unit 32 controlled by the control computer 20, and while measuring the drawing timing of the graphic data, the blanking circuit 25, the beam shaper driver 26, the main deflector driver 27, the auxiliary deflector Set to any of the deflector drivers 28.

  In the beam shaper driver 26, a predetermined deflection signal is applied to the beam size varying deflector 14 of the electron beam optical system 10, thereby controlling the size of the electron beam.

  The drawing data decoder 24 creates subfield positioning data based on the drawing data, and sends the subfield positioning data to the main deflector driver 27. Then, a predetermined deflection signal of the main deflector 15 of the electron beam optical system 10 is applied from the main deflector driver 27, whereby the electron beam is deflected and scanned to a specified subfield position.

  Further, the drawing data decoder 24 generates a sub deflector scanning control signal based on the drawing data, and sends this control signal to the sub deflector driver 28. Then, a predetermined sub deflection signal is applied from the sub deflector driver 28 to the sub deflector 16, thereby drawing inside the sub field.

  FIG. 2 is a flowchart showing the flow of drawing data from the pattern data decoder 23 to the deflection control unit 32, which is a feature of the present embodiment.

  First, shot position data (X, Y) and size data (Lx, Ly) are sequentially read from the pattern data decoder 23 into the area recognition unit 30 (step S1). Subsequently, the area (Lx × Ly) of each shot is calculated (step S2), and the areas of adjacent shots are added (step S3).

  Next, it is determined whether or not the added area is equal to or smaller than a pre-registered allowable area (an area in which dimensional variation due to resist heating can be ignored) (step S4). If the added area is equal to or smaller than the allowable area, these shots are merged (step S5), and the shot position data and size data are rewritten (step S6). On the other hand, if the added area is larger than the allowable area, the data is sent as it is to the deflection control unit.

  As described above, according to the present embodiment, the area of the graphic data is calculated by the area recognition unit 30 and the drawing data correction unit 31, and the drawing data is reconstructed so as to have the maximum area determined based on the resist and substrate information. Therefore, even if the same settling time is set, the dead time does not increase depending on the pattern. Therefore, it is possible to suppress dimensional variations caused by resist heating without reducing accuracy and throughput. This effect is particularly effective for an electron beam lithography apparatus for a mask having a high beam acceleration voltage (for example, 20 keV or more) and a high beam current density and high resolution.

(Second Embodiment)
The feature of the electron beam drawing method in this embodiment is that the maximum area of the variable shaped beam to be drawn is referred to a table in which a correlation obtained in advance experimentally according to the type of resist and substrate is registered. It is to decide.

  FIG. 3 is a test pattern for examining how the area of the variable shaped beam and the type of resist and substrate are related to the drawing accuracy. In this embodiment, both the line width (Lw) and the space width (Sw) are fixed to 2.0 [μm]. That is, the drawing area ratio is 50%. For a certain resist, the inside of the line is drawn in four sizes of Sx = Sy = 0.25 [μm], 0.5 [μm], 1.0 [μm], and 2.0 [μm]. ing. In the figure, 35 is a subfield, and 36 is a shot figure.

FIG. 4 is a graph in which the range of dimensional variation within the subfield 35 of the pattern is plotted against the area (Sx × Sy) of the shot 36. The parameter is the type of resist, 40 is resist A, 41 is resist B, and 42 is resist C. According to this graph, the maximum area of the variable shaped beam that suppresses the dimensional variation in the subfield to 2.5 [nm] or less is 4.0 [μm ² ] in the resist A and 1.4 [μm ² ] in the resist B. In the resist C, the thickness is 0.4 [μm ² ]. If these values are registered as data in the memory section of the control computer 20 in FIG. 1, the optimum maximum beam area according to the type of resist can be selected.

  The effect is compared with the pattern of FIG. In the pattern of FIG. 8, four square beams 81 at the upper end and the lower end are drawn with the maximum beam sizes Sx and Sy (Sx = Sy). However, the diagonal line in the middle of the pattern has half the Sy in order to reduce the unevenness due to the rectangular approximation. Regarding Sx, it cannot be increased any more due to the limitation of the maximum beam size in the X direction. Therefore, conventionally, 30 beams had to be hit to draw this pattern.

  On the other hand, according to the present embodiment, the vertical and horizontal sizes of the beam can be defined by the beam area, so that drawing can be performed as shown in FIG. That is, the area of the beam 52 is (2Sx) × (Sy / 2) = Sx × Sy, and the area can be the same as that of the beam 50 (the beam 80 in FIG. 8). As a result, the drawing is completed with a small number of beams without impairing the drawing accuracy. In this example, the number of beams is reduced from 30 to 19, and the net 37% throughput is improved.

  Furthermore, if the surface precision of the beam changes, the blur of the electron beam due to the Coulomb repulsive force changes and deteriorates the drawing accuracy. However, in this embodiment, the beam area is kept as constant as possible, so this effect is minimized. There is also an advantage that can be suppressed to the limit.

(Modification)
In addition, this invention is not limited to embodiment mentioned above. The configuration of the drawing apparatus is not limited to that shown in FIG. 1 and can be changed as appropriate according to the specifications. In short, any method may be used as long as a variable shaped beam is produced and shot drawing is performed. In the embodiment, the drawing method using an electron beam has been described as an example. However, the present invention can be applied to a drawing method using an ion beam as well as the electron beam. Furthermore, the present invention is not limited to mask drawing, and the present invention can also be applied to a method of drawing a pattern directly on a wafer.

  In addition, various modifications can be made without departing from the spirit of the present invention.

1 is a schematic configuration diagram showing a variable shaped beam type electron beam drawing apparatus according to a first embodiment; 6 is a flowchart showing a flow of drawing data from the pattern data decoder to the deflection control unit. The schematic diagram which shows the test pattern for investigating 2nd Embodiment, and investigating the relationship between the area of a beam, and drawing precision. The schematic diagram which shows the relationship between the beam area and the dimensional variation in a subfield which used the kind of resist as a parameter. The schematic diagram which shows the example of the shot division | segmentation by 2nd Embodiment. The schematic diagram which shows the dimension fluctuation | variation resulting from resist heating. The schematic diagram which shows the relationship between the shot size which used the drawing area ratio as a parameter, and dimensional variation. The schematic diagram which shows the example of the shot division | segmentation by 3rd prior art. The characteristic view which shows the relationship between shot size and a dimensional variation for demonstrating the problem of a 4th prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sample chamber 2 ... Sample 3 ... Stage 4 ... Stage drive circuit 5 ... Position detection circuit 6 ... Electron gun 7, 8, 9, 11, 12 ... Various lenses 10 ... Electron beam optical system 13 ... Blanking deflector 14 ... Beam size variable deflector 15... Beam scan main deflector 16... Beam scan sub deflector 17, 18... Beam shaping aperture 20... Control computer 21 .. Magnetic disk 22. Drawing data decoder 25 ... Blanking circuit 26 ... Beam shaper driver 27 ... Main deflector driver 28 ... Sub-deflector driver 30 ... Area recognition unit 31 ... Drawing data correction unit 32 ... Deflection control unit 35 ... Subfield 36 ... Shot figure 40. Resist A
41 ... Regist B
42. Resist C
50 ... Maximum size shot to minimize resist heating 52 ... Shot with the same area as 50

Claims (6)

Beam shaping means for shaping the variable shaped beam by controlling the shape and size of the charged beam emitted from the charged beam source;
Means for dividing a pattern to be drawn on a resist on a sample into a plurality of shot figures that can be formed by the beam forming means;
Means for detecting an area of each shot figure;
Means for reconstructing each shot graphic such that the area of each detected shot graphic approaches a predetermined maximum area;
A charged beam drawing apparatus comprising: Beam shaping means for shaping the variable shaped beam by controlling the shape and size of the charged beam emitted from the charged beam source;
Means for dividing a pattern to be drawn on the sample into a plurality of shot figures that can be shaped by the beam shaping means;
Means for detecting an area of each shot figure;
The area of each shot figure detected is subject to dimensional variation due to resist heating, which is determined by the settling time from beam irradiation to draw one shot figure to beam irradiation to draw the next shot figure. Means for reconstructing each of the shot figures so as to approach a negligible maximum value;
A charged beam drawing apparatus comprising:   3. The maximum area of each shot figure is determined with reference to a table in which a correlation obtained experimentally in advance according to the type of resist and sample is registered. The charged beam drawing apparatus described.   The charged beam drawing apparatus according to claim 1, wherein as the means for reconstructing each shot figure, adjacent shot figures are merged within a range not exceeding the maximum area. Forming a variable shaped beam by controlling the shape and dimensions of the charged beam emitted from the charged beam source;
Dividing the pattern to be drawn on the resist on the sample into a plurality of shot figures that can be formed by the beam forming means;
Detecting the area of each shot figure;
Reconstructing each shot graphic such that the area of each detected shot graphic approaches a predetermined maximum area;
A charged beam writing method comprising: Forming a variable shaped beam by controlling the shape and dimensions of the charged beam emitted from the charged beam source;
Dividing the pattern to be drawn on the sample into a plurality of shot figures that can be shaped by the beam shaping means;
Detecting the area of each shot figure;
The area of each shot figure detected is subject to dimensional variation due to resist heating, which is determined by the settling time from beam irradiation to draw one shot figure to beam irradiation to draw the next shot figure. Reconstructing each of the shot figures so as to approach a negligible maximum value;
A charged beam writing method comprising:

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