JPH01201919A - Charge beam lithography equipment - Google Patents

Abstract

PURPOSE:To improve junction accuracy between fields, by memorizing in advance a polarizing angle which is obtained when the amplitude of a beam on a reference mark affixed to a cassette is adjusted to be constant, thereby obtaining the deflection angle at an optional point on a beam irradiation plane by performing an arithmetic operation on the basis of the above memorized polarizing angle. CONSTITUTION:Marks M are affixed to three corners at least out of four corners on a cassette 16. Using a mark detecting technique through those marks M as well as measuring results by laser length measuring machines 20a and 20b, the automatic adjustment of a beam scanning width at a reference point is performed by causing a CPU to adjust a deflection angle so that values of mark detection at times going to and from are equivalent. As the writing position of a beam pattern is determined beforehand, relations of deflection angles to respective positions of an irradiation plane are tabulated previously and they are housed in the CPU 21. When the beam pattern is written actually, the deflection angle alpha to the writing position is read and scanning quantity signals according to the above deflection angle alpha are given to a deflection amplifier 14. The deflection amplifier 14 drives a deflecting system 13 according to the input signals. Thus beam writing repeated in this way improves junction accuracy between fields.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a charged beam lithography apparatus, and more particularly to a charged beam lithography apparatus with improved joining accuracy between fields.

(Prior art) When performing beam lithography using a charged beam lithography system such as an electron beam lithography system or a focused ion beam system, there are cases in which the beam lithography is performed on a mask material for optical transfer, and in cases where it is directly applied to a wafer during the device fabrication process. May be drawn. By the way, when a charged beam is irradiated onto a material, the surface of the material is not always perpendicular (that is, horizontal) to the beam. FIG. 6 is a diagram showing a case where the irradiation surface of the charged beam 13i is tilted. (a) shows the case where the stage 1 itself on which the material 2 is placed is tilted, and (b) shows the case where the stage 1' is not tilted but the material 2 is tilted.

If the irradiation surface of the charged beam is tilted, the working distance will differ depending on the position irradiated with the charged beam, resulting in a decrease in drawing accuracy. This will be explained using FIG. The plane A-A' in the figure is the original irradiation plane, and the scanning distance at that time is.

Let h be the working distance. Due to the tilted irradiation surface,
Assume that the irradiation surface changes to BB' and CC'. The deflection angle θ of the beam scanned from the deflection fulcrum K is constant, and the amount of movement of the stage (in this case, the distance) is also constant. Therefore, in the case of c-c', the field joints are separated, and in the case of B-B', the field joints overlap.

(Problems to be Solved by the Invention) In the case of the above-mentioned direct drawing method, it is necessary to perform overlapping drawing, but alignment marks are placed on the material for this purpose. The tilt of the cassette to be held can be corrected. However, when drawing on a mask material such as glass, the inclination of the irradiation surface cannot be corrected because there is no alignment mark. For this reason, since the surface of the mask material is made uniform, the inclination of the cassette that holds the mask material and the material movement stage will affect the drawing accuracy (in other words, the field joining accuracy).

In order to prevent such problems, a method is used in which the height of the beam irradiation point on the material surface (the working distance) is measured and the amount of change is corrected. However, this method requires an additional optical system to measure the height of the irradiation point. For this reason, it is difficult to use it in a nanometer lithography machine having a narrow working distance of an electron beam lithography system. Moreover, even if this type of optical system is added, it will be expensive, and the structure will inevitably be complicated.Furthermore, careful attention will always be required to maintain this optical system.

The present invention has been made in view of these points, and
The purpose is to realize a charged beam lithography device that can improve the joining precision between fields.

(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, attaches reference marks to at least three of the four corners of a cassette that holds materials, and sets the amplitude of the beam to a constant value on each mark. The system memorizes the respective deflection angles when adjusted so that the angles are adjusted to , calculates the deflection angle corresponding to the writing position based on this deflection angle data, and performs beam scanning using the calculated deflection angles. It is something to do.

(Function) The deflection angle when adjusted so that the amplitude of the beam on the marks attached to the four corners of the cassette becomes constant is memorized.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, 11 is a charged beam source that emits a charged beam B1, and 12 is a converging lens that converges the charged beam B1. As the converging lens 12, an electron lens is used. 13 is a scanning deflector that deflects the charged beam Bi;
4 is a deflection amplifier that drives the deflector 13. The field is set by the maximum beam amplitude of the deflector 13.

15 is a stage, 16 is a cassette placed on the stage 15, and 17 is a mask material held by the cassette 16. M is a mark attached to at least three of the four corners of the cassette 16, and 18 is a detector for detecting a reflected signal from the mark M during beam scanning. 19 is a stage drive mechanism that moves the stage 15=4- by a predetermined amount in the x and y directions;
0a and 20b are laser length measuring devices that detect the position (coordinates) of the stage 15 in the x and y directions.

21 is the output of the detector 18 and a laser length measuring device 20a.

20b, performs various calculations, and provides scanning signal data to the deflection amplifier 14 based on the calculation results, as well as a stage drive signal to the stage drive mechanism 19;
22 is a keyboard for inputting various commands and data to the CPU 21;

The operation of the device configured as described above will be explained as follows.

First, the configuration of the cassette section will be explained. FIG. 2 is a diagram showing an example of the external configuration of the cassette section.

The mask material 17 is arranged inside the cassette 16 as shown in the figure, and its upper surface is regulated by upper surface regulating plates 23a to 23d attached to the four corners of the cassette 16, respectively. FIG. 3 is a diagram showing the biased state of the mark M, in which the downward spring 25 is applied with a biasing force toward the rear, and the mark M hits the opening 24 (24a to 24d in the figure) of the upper surface regulating plate 23. The position is fixed. As a result, the positions of the marks M at the four corners in the height direction match the positions of the upper surface regulating plate.

Mark detection method using these marks M and laser length measuring device 2
The beam scanning width is automatically adjusted using the measurement results of 0a and 20b. As shown in FIG. 4, the positions marked with marks M are A, B, and C, respectively.

Let it be D. Here, one of the four corners, that is, in this example, A
Specified beam scanning width for only one point, e.g. 2000.00 μm
Adjust to. Specifically, the mark M at point A is moved by a prescribed beam scanning width, and this movement amount is determined by the laser length measuring device 20a,
20b. The mark M moves back and forth by a prescribed scanning width under CPU control, detects the previous mark position and the backward mark position at the initial beam deflection angle, and calculates the value of this mark detection and the amount of movement of the mark for the prescribed scanning width. The CPU calculates the initial deflection angle from . The CPU adjusts the deflection angle, that is, the deflection voltage, so that the value of this mark detection becomes the same value during the forward and backward movements, thereby completing the automatic adjustment, ie, the alignment, of the beam scanning width at this point.

The deflection angle at the fitted point (point A in this case) is 2 of point A.
Considering that the direction is also a reference, it can be considered that the coordinates of point A are (x, y, z) - (0, O, O).

Among the planes based on point A, plane 11 (indicated by broken lines) in FIG. 4 is equivalent to the inclined plane shown in FIG. However,
The horizontal plane at point A where the scanning widths are actually matched is P2 (indicated by a solid line), and this is the plane where the stage movement and scanning width are accurately matched, so it is possible to draw the correct figure anywhere within this P plane. can. However, the actual drawing surface 11 does not match the ideal surface P2 and is therefore tilted. Therefore, in the present invention, the deflection angles required to scan one field aligned at the reference point A are αΔX and αAy (see Fig. 5).
. The scanning distance at this time is defined as LA.

Next, using marks M attached to each of the three points B, C, and D of the slack, align them at point A to obtain the deflection angle αAX.

In the same way as the method of aligning at point A using αAy, at these three points B, C, and D, simply move the stage once (for example, 2000.00 μm) and detect the mark without performing alignment. Measure the scanning width at each point. As a result, the deflection angles at each point are αB, αC9αD.

As shown in Fig. 4, if the lengths of the field plane in the X direction and y direction are LX and LY, respectively, then the deflection required to obtain the beam width at an arbitrary point Q on the beam irradiation surface (see Fig. 4) Assuming that each measurement point changes linearly, the angle α(x, y) is given by the following equation within the drawing area.

α(x, y) −X [(αB−αA)/Lx]+αA+y [(αD
−αΔ)/Ly] ...(1) However, (x
, y) are the coordinates of point Q. The deflection angle αC at the 0 point, which is clear from the above equation, is not included. The reason is that the deflection angle αC at the 0 point can be calculated by substituting x=IX and V=LV using equation (1). However, the difference between the calculated result and the actual measured value is a difference based on linear approximation. Therefore, it becomes more accurate if this difference is proportionally distributed to the result calculated using equation (1).

Since the drawing position of the beam pattern is determined in advance,
The relationship between the deflection angle α and each position (x, y) of the irradiation surface is made into a table in advance and stored in the CPU 21.

When actually writing a beam pattern, the deflection angle α with respect to the writing position is read out, and a scanning amount signal corresponding to the deflection angle α is provided to the deflection amplifier 14. Deflection amplifier 14 drives deflector 13 according to the input signal. As a result, beam writing with accurate dimensions can be performed at all times.

Once the beam drawing for one field is completed, the CPU
21 drives the stage drive mechanism 19 to move the beam irradiation surface by one field. At this time as well, the deflection correction angles α at the four corners with the first point A as a reference can be determined using equation (1).

By repeating such beam writing, the bonding between the fields becomes good, and the bonding accuracy can be improved.

In the above explanation, we have explained the case where a reference mark is added on the cassette, but when performing beam writing by pasting a piece such as GaAS on a wafer etc., QaA
Reference marks are attached to S itself, and deflection angle correction can be performed using at least three of these marks as representative points.

It goes without saying that the working distance shown in FIG. 7 must be determined in advance.

(Effects of the Invention) As described above in detail, according to the present invention, the deflection angle when adjusted so that the amplitude of the beam on the reference mark attached to the cassette is constant is stored in advance, By calculating the deflection angle at any point on the beam irradiation surface based on this deflection angle, it is possible to draw the beam with accurate dimensions on the irradiation surface metal, and it is possible to improve the joining accuracy between fields. .

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing an example of the external configuration of the cassette section, Fig. 3 is a diagram showing the biasing state of the mask material, and Fig. 4 is a beam irradiation surface. 5 is an explanatory diagram of deflection angle correction, FIG. 6 is a diagram illustrating the case where the beam irradiation surface is tilted, and FIG. 7 is a diagram illustrating the influence of the deflection angle on drawing accuracy. 1... Charged beam source 12... Focusing lens 13.
...Deflection angle 14...Deflection amplifier 15...Stage 16...Cassette 17...Mask material
18...Detector 19...Stage drive mechanism 20a, 20b...Laser length measurer 21...CPU 22...Keyboard M.
...Reference mark Bi...Charged beam patent applicant Japan Denshi Co., Ltd. Representative Patent attorney Ijima
Fuji Jigai 1 person Fig. 3 Fig. 25 Spring No. 4 Takuchi Fig. 5

Claims (1)

[Claims] Attach reference marks to at least three of the four corners of the cassette that holds the material, and memorize the deflection angles when adjusting the beam amplitude on each mark to a constant value. A charged beam drawing device characterized in that it is configured to calculate a deflection angle corresponding to a writing position based on deflection angle data, and perform beam scanning using the calculated deflection angle.