JPH11274038A - Pattern drawing method and drawing apparatus thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the effects of resist heating and dimensional variations. SOLUTION: In this pattern drawing method, exposures by fine shots of electron beams are performed in order, a desired pattern is drawn on a chip, and the same patterns are doubly exposed on the chip. At this time, the drawing region of the chip 51 is drawn with the unit of a subfield 53 in which a frame 52 divided into strip shapes are more divided into small regions, and a second drawing is performed with the order reversed to the order of shots performed in the first drawing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern drawing technique using an electron beam, a laser beam or the like, and more particularly to a pattern drawing method and a drawing apparatus for drawing the same pattern a plurality of times (multiple drawing).

[0002]

2. Description of the Related Art In recent years, the miniaturization of patterns in the semiconductor industry has been remarkable. It is said that the pattern line width required for 1 Gbit DRAM or later is 0.15 μm (0.6 μm on the mask) or less.
The demand for high control of the resist process is very severe. One of the requirements is to increase the precision of the mask. That is,
The requirement for the dimensional variation on the mask also has the effect that the dimensional variation on the mask is emphasized on the wafer at the time of transfer, and is becoming stricter than the miniaturization ratio of the design rule.

[0003] Factors of dimensional variation on a mask include:
It can be classified into two major categories: process-based and drawing-device-based. What is said to be attributable to the drawing apparatus is variation due to connection of frames, subfields, shots, and the like, and beam instability (fluctuations in current density, noise in electrical circuits, and the like). Among the causes of the process, the in-plane variation and the reproducibility variation of each process such as resist coating, PEB, development, and etching are mainly involved. One of the causes of the variation is dimensional variation due to the resist heating effect.

[0004] The resist heating effect is a phenomenon in which the temperature of the resist rises due to the beam irradiation, and the dimensions of the resist fluctuate under the influence of the heat. In general, in a drawing method using an electron beam, first, drawing data is divided for each frame, and further divided for each subfield. In this case, the drawing order is drawn in a certain direction. This is the same for multiple writing. In this case, there is a problem that a dimensional difference occurs between the vicinity of the place where the shot with the earlier drawing order is shot and the place where the shot with the later drawing order is shot in the subfield.

In electron beam writing, studies on chemically amplified resists have been actively conducted for the purpose of increasing the sensitivity of resists, and the influence of resist heating is being reduced. However, the magnitude of the dimensional variation caused due to the resist heating effects are also surface can not be said to bite because some resist process dependent, but the number in the exposure amount of 10 [mu] C / cm ² in the evaluation of the present inventors It seems to be about nm. Accordingly, in consideration of the dimensional variation allowed for the mask, the actual size is still a size that cannot be ignored.

[0006]

As described above, in the conventional pattern writing method using an electron beam, there is a problem that a dimensional variation occurs in a writing pattern due to an effect of a resist heating effect. This was not negligible in view of the resulting dimensional variations.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has as its object to reduce the influence of the resist heating effect and reduce the dimensional variation in a drawing pattern. An object of the present invention is to provide a drawing method and a drawing device.

[0008]

(Structure) In order to solve the above-mentioned problem, the present invention employs the following structure.
That is, the present invention is a pattern drawing method for drawing a desired pattern on a sample by performing exposure with a fine shot of an energy beam in a predetermined order, and drawing the same pattern on a sample by superposing a plurality of times, It is characterized in that the order of writing shots on the sample is changed every time.

According to the present invention, there is provided a pattern drawing apparatus which draws a desired pattern on a sample by performing exposure with a fine shot of an energy beam in a predetermined order, and draws the same pattern on the sample a plurality of times. Means for changing the order of shots for writing on the sample each time,
Means for performing shot exposure on the sample in the order of shots determined by the means.

Here, preferred embodiments of the present invention include the following. (1) In a specific field on the sample, the second writing is performed in a reverse order to the shot order in the first writing.

(2) Within a specific rectangular field on the sample,
For the layout of the shot order in the first drawing, the second, third, and fourth drawing are performed by layouts rotated by 90 degrees, 180 degrees, and 270 degrees from the center of the field, respectively.

(3) The specific field is the entire drawing area on the sample, and the order of shots is changed for each drawing area. (4) The specific field is a frame obtained by dividing the drawing area on the sample into strips, and the order of shots is changed in frame units.

(5) The specific field is a subfield obtained by further dividing a frame into small areas, and the order of shots is changed in units of the subfield. (6) Use an electron beam or ion beam as the energy beam.

(7) A laser beam is used as an energy beam. (Operation) According to the present invention, in multiple writing using an energy beam, by giving a certain restriction on the order of shots in each writing, the influence of dimensional fluctuation due to the resist heating effect can be reduced.

Specifically, by performing double drawing when performing drawing in a certain field, and performing drawing in a completely reverse order in the second drawing with respect to the shot order drawn in the first drawing. First, the dimensional distribution due to the resist heating effect generated at the first time can be offset by the drawing having the opposite distribution by the second drawing, and the dimensional uniformity in the field can be improved.

When quadruple drawing is used, the order of shots to be drawn in a certain rectangular field is determined with respect to the layout of the order of shots shot in the first drawing with respect to the intersection (field center) of the diagonal line of the field. The second, third, and fourth renderings are each performed 90 times from the center of the field.
Each of the layouts rotated by 180 degrees, 180 degrees, and 270 degrees is drawn once. As a result, dimensional fluctuations due to resist heating in the field can be significantly reduced as compared with the conventional case, and dimensional uniformity can be significantly improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. (First Embodiment) FIG. 1 is a schematic configuration diagram showing an electron beam writing apparatus used in a first embodiment of the present invention.

In the figure, reference numeral 10 denotes a sample chamber.
A sample table 12 on which a sample 11 is placed and which can be moved in the X direction (left and right directions in the drawing) and the Y direction (front and back directions in the drawing) is accommodated. Reference numeral 20 denotes an electron optical column, and this column 2
Reference numeral 0 includes an electron gun 21, various lens systems 22a to 22e, various deflection systems 23 to 26, a blanking plate 27a, beam forming apertures 27b and 27c, and the like.

Reference numeral 31 denotes a sample stage drive circuit for driving the sample stage 12, 32 denotes a laser length measurement system for measuring the position of the sample stage 12, and 33 denotes a drive control of the scanning deflectors 25 and 26. A deflection control circuit section for driving and controlling the blanking deflector 23;
Reference numeral 5 denotes a variable shaping beam size control circuit for controlling the driving of the shaping deflector 24; 36, a buffer memory and a control circuit for temporarily storing a pattern to be drawn and for controlling each of the control circuits 34, 35; Control computer, 3
8, a data conversion computer for converting CAD data into EB data; and 39, a CAD system.

In the above configuration, the electron beam emitted from the electron gun 21 is turned on by the blanking deflector 23.
-Is turned off. By adjusting the irradiation time at this time, the present apparatus can change the irradiation amount according to the irradiation position. The beam that has passed through the blanking plate 27a is shaped into a rectangular beam or a triangular beam by the beam shaping deflector 24 and the beam shaping apertures 27b and 27c, and its dimensions are varied. Then, the shaped beam (shot) is applied to the scanning deflector 25,
The beam is deflected and scanned on the sample 11 by 26, and a desired pattern is drawn on the sample 11 by this beam scanning. The standard acceleration voltage in the present embodiment is 50 kV, and the maximum size of the variable shaped beam that can be generated is a rectangle of 2 μm square.

Generally, a drawing chip is divided into certain areas, and drawing is performed for each area. The minimum unit is called a subfield, and its area size is 16 to
20 μm square (variable). Further, the layer above it is called a frame (500 μm width). FIG. 3 shows these relationships. In the figure, reference numeral 51 denotes a chip (entire drawing area), 52 denotes a frame, and 53 denotes a subfield.

The drawing method according to the present embodiment is characterized in that the drawing order within a certain subfield in the double exposure method is reversed between the first drawing and the second drawing. That is, in the first writing and the second writing in the subfield, the writing is performed by reversing the order of sequentially exposing the fine shots of the beam. At this time, the exposure amount is set so that the total exposure amount does not change and the first and second exposure amounts become equal (for example, each resist having a resist sensitivity of 8 μC / cm ² is 4 μC / cm ² ). I do.

Next, an example in which the present embodiment is applied to the production of a Cr mask will be described more specifically with reference to the process chart of FIG. As shown in FIG. 2, first, a positive chemically amplified resist (sensitivity 8 μm) was coated on the surface of a 6-inch glass substrate with a Cr film.
(C / cm ² ) is applied to a resist with a thickness of 400 nm by a spin coating method.

Next, pre-bake is performed as necessary,
After that, in the above-described exposure method (in a certain subfield in the double exposure method, the drawing order is reversed between the first drawing and the second drawing, and the total exposure amount remains unchanged at this time, and The first exposure is performed by setting the exposure amounts to be equal to each other), and the exposure amount is set to 4 μC / c in the rendering order (order of shot exposure) shown in FIG.
It carried out in the m ^2. Subsequently, the second writing is performed while the exposure is set to 4 μC / cm ² in the drawing order shown in FIG.

Then, after performing PEB at 90 ° C. for 15 minutes, spray-type development was performed with 0.21 N TMAH. Subsequently, using a Cl ₂ / O ₂ gas system, high-frequency power 80 (W), pressure 50 (mtorr), flow rate 80/20
(Sccm), the Cr film was dry-etched, and the resist was removed and washed. After that, by performing multi-point measurement of the size of the pattern formed on the substrate using an optical microscope, the following operations and effects were remarkably observed.

FIG. 3A shows the order of shots in a single shot in a certain subfield. As shown in this figure, it is very common that the drawing is performed in an order according to a certain regularity.
In this figure, since the drawing order of the lower left side of the subfield is earlier, the heat generated at the time diffuses in the resist and the base, and when performing the drawing of the upper right side of the subfield with the lower drawing order, the heat is there. As a result, the dimensional variation as shown in FIG. 4A occurs in the subfield (the dimension is evaluated by a pattern cut by a dotted line). In the conventional multiple writing, this is repeated, so that the dimensional variation is further enlarged.

On the other hand, according to the present embodiment, the distribution of the dimensional variation can be reduced. The principle will be described below. The dimensional variation due to the resist heating effect that occurs in the first drawing order is as described above. The order of shots in the second drawing is
As shown in FIG. 3B, it is completely opposite to FIG.
Therefore, as shown in FIG. 4B, the dimensional variation due to the resist heating effect that occurs in the second drawing order has a relationship opposite to that of FIG. In other words, the size increases in the region where the resist heating effect is large,
In FIG. 4A, the right dimension is increased, and in FIG. 4B, the left dimension is increased.

In this embodiment, FIGS. 5A and 5B (FIG. 4)
Since the two distributions shown in FIGS. 5A and 5B are overlapped by the double exposure, a total dimensional distribution as shown in FIG. 5C is obtained. That is, the dimensional variation due to the resist heating in the first writing and the dimensional variation due to the resist heating in the second writing are mutually offset, and a dimensional distribution with extremely small dimensional variation is obtained.

As described above, according to the present embodiment, the dimensional variation in the sub-field was about 7 nm at the time of single-shot drawing, but by using the above-described drawing method, the dimensional variation in the sub-field was improved. Variation about 3
nm. By using this drawing method for producing a pattern on a mask, it has become possible to obtain a highly accurate mask with small variations.

(Second Embodiment) Next, a second embodiment of the present invention will be described. Note that the configuration of the device is the same as that of the first embodiment, and a description thereof will be omitted.

In the present embodiment, in the quadruple drawing, the drawing order in a certain field is determined by the shot order shot in the first drawing with respect to the intersection of the diagonal lines of the chip (chip center). It is characterized in that the layouts obtained by rotating the fourth and fourth times by 90 degrees, 180 degrees and 270 degrees from the center of the chip are drawn once each. At this time, quadruple exposure is performed, but the total exposure is not changed, and the first, second, third,
The fourth and fourth exposures are set so that the exposure amounts are equal (for example, ² μC / cm ² ), and drawing is performed.

An example in which the present embodiment is applied to the manufacture of a Cr mask will be described more specifically with reference to the process chart of FIG. As shown in FIG. 2, a positive chemically amplified resist (sensitivity 8 μC /
(cm ² ) is adjusted to 400 nm in film thickness by a spin coating method, and a resist is applied.

Next, pre-bake is performed as required,
Thereafter, the drawing method described above (the order of the first drawing, the second drawing, the third drawing, and the fourth drawing in a certain subfield in the quadruple exposure method is shown in FIGS. 6A and 6B, respectively)
(C) Perform in the order shown in (d). At this time, the exposure amount is set so that the total exposure amount does not change, and
Second, third and fourth exposure doses (each 2 μC /
cm ² ) were set to be equal), and drawing was performed while overlapping.

Specifically, in the first drawing, FIG.
As shown in (a), the order of shot exposure was determined so as to start from the lower left and end at the upper right. In the second drawing, FIG.
As shown in (b), the order of shot exposure was determined so as to start from the lower right and end at the upper left. In the third drawing, the order of shot exposure was determined so as to start from the upper right and end at the lower left, as shown in FIG. In the fourth drawing, the order of shot exposure was determined so as to start from the upper left and end at the lower right, as shown in FIG. Here, the layout of the shot exposure in FIG. 6B is obtained by rotating the layout in FIG. 6A by 90 degrees counterclockwise around the center of the subfield. Similarly, the layout of the shot exposure in FIGS. 6C and 6D is obtained by rotating the layout of FIG. 6A by 180 and 270 degrees counterclockwise around the center of the subfield.

Then, after performing PEB at 90 ° C. for 15 minutes, development by spraying with 0.21 N TMAH was performed. Subsequently, using a Cl ₂ / O ₂ gas system, high-frequency power 80 (W), pressure 50 (mtorr), flow rate 80/20
(Sccm), the Cr film was dry-etched, and the resist was peeled off and washed. After that, by performing multi-point measurement of the size of the pattern formed on the substrate using an optical microscope, the following operations and effects were remarkably observed.

In the case of one-time drawing, as described in the first embodiment, since the drawing order on the lower left side of the subfield is earlier, the heat generated during drawing diffuses in the resist and the base. However, when drawing is performed on the upper right side of the subfield in which the drawing order is slow, the heat is transmitted to the subfield, and dimensional variations as shown in FIG. (Evaluation of dimensions by pattern).

On the other hand, according to the present embodiment, the distribution of the dimensional variation can be reduced. That is, by drawing the subfields in the order shown in FIGS. 6A, 6B, 6C, and 6D, the four distributions are overlapped by the quadruple exposure, and as a result, as shown in FIG. A total dimensional distribution is obtained. That is, the diffusion of heat in the Y direction is also averaged in the plane by drawing four times (drawing starts near four corners), so that dimensional variations not only in the X direction but also in the Y direction in the subfield can be reduced. It is. Note that the order of FIGS. 6A, 6B, 6C, and 6D is not limited to this, and the same result can be obtained by appropriately changing the order.

As described above, according to the present embodiment, the dimensional variation in the sub-field was about 7 nm at the time of single-shot writing, but the dimensional variation in the sub-field was obtained by using the above-described writing method. The variation is X,
It was possible to improve the size in both Y directions to about 2 nm. By using this drawing method for producing a pattern on a mask, it has become possible to obtain a very accurate mask with extremely small dimensional variations.

The present invention is not limited to the above embodiments. In the embodiment, the drawing order is changed in units of subfields. In addition, the drawing order may be changed in units of frames. If the drawing shot speed is sufficiently high and the effect of resist heating in subfield units is negligibly small, the drawing order may be changed only in frame units. It is also possible to change the drawing order in larger field units, for example, in chip units.

In the embodiment, the multiple writing using the electron beam has been described. However, the present invention can be applied to the multiple writing using the ion beam. Furthermore, the present invention is not limited to charged particles such as electrons and ions, and can be applied to laser drawing in which laser light is scanned by a mirror to draw a pattern. In addition, various modifications can be made without departing from the scope of the present invention.

[0041]

As described above in detail, according to the present invention, the dimensional variation in a certain area (chip, frame, subfield, etc.) can be remarkably improved as compared with a single shot drawing. Becomes Therefore, by applying the present invention to the production of a pattern on a mask and the production of a pattern on a wafer, it becomes possible to obtain a very high-precision pattern with small dimensional variations.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an electron beam drawing apparatus used in a first embodiment.

FIG. 2 is a view showing a specific process when manufacturing a Cr mask.

FIG. 3 is a schematic diagram showing a drawing order according to the method of the first embodiment.

FIG. 4 is a schematic diagram showing a relationship between a drawing order and a dimensional variation.

FIG. 5 is a schematic diagram showing dimensional variations in a certain field when a Cr mask is manufactured by the method of the first embodiment.

FIG. 6 is a schematic diagram showing a drawing order according to the method of the second embodiment.

FIG. 7 is a schematic diagram showing a relationship between a drawing order and dimensional variation.

FIG. 8 is a schematic diagram showing dimensional variations in a certain field when a Cr mask is manufactured by the method of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Sample chamber 11 ... Sample 12 ... Sample stand 20 ... Electron optical column 21 ... Electron gun 22a-22e ... Various lens systems 23-26 ... Various deflection systems 27a ... Blanking plates 27b, 27c ... Beam forming aperture 31 ... Sample stage drive circuit unit 32 Laser measurement system 33 Deflection control circuit unit 34 Variable beam size control circuit unit 36 Buffer memory and control circuit 37 Control computer 38 Data conversion computer 39 CAD system. 51: chip 52: frame 53: subfield

Claims (5)

[Claims] 1. A pattern drawing method in which a desired pattern is drawn on a sample by performing exposure by a fine shot of an energy beam in a predetermined order, and the same pattern is drawn on a sample by overlapping a plurality of times. A pattern writing method characterized by changing the order of writing shots on a sample every time. 2. A pattern drawing method in which a desired pattern is drawn on a sample by performing exposure with a fine shot of an energy beam in a predetermined order, and the same pattern is drawn twice on the sample. A pattern writing method, wherein a second writing is performed in a reverse order to a shot order in the first writing in a specific field on a sample. 3. A pattern drawing method in which a desired pattern is drawn on a sample by performing exposure with a fine shot of an energy beam in a predetermined order, and the same pattern is drawn four times on the sample. Within a specific rectangular field on the sample, the second and third layout
The fourth and fourth drawing are 90 degrees from the center of the field, 18
A pattern drawing method characterized by performing each of the layouts rotated by 0 degrees and 270 degrees. 4. The method according to claim 1, wherein the specific field is a subfield obtained by further dividing a frame obtained by dividing the drawing area on the sample into strips into smaller areas, and the order of the shots is changed in units of the subfield. 4. The pattern drawing method according to claim 2, wherein 5. A pattern writing apparatus for writing a desired pattern on a sample by performing exposure with a fine shot of an energy beam in a predetermined order, and writing the same pattern on the sample a plurality of times. A pattern drawing apparatus comprising: means for changing the order of shots for writing on a sample each time; and means for performing shot exposure on the sample in the order of shots determined by the means.