JPH03230514A - Electron beam aligner and aligning method - Google Patents

Abstract

PURPOSE:To realize highly precise calibration of the deflection coordinate value of a beam and the mask coordinate system, by determining the position and the dimension of a beam on a mask plate, from the deflection condition of a block deflecting means for conditions, and the previously known dimension and arrangement position of a mark pattern. CONSTITUTION:A mark pattern 61 for calibration is formed on a stencil mask 39. Mask deflectors 38A-38D form a block deflecting means 51. In order to pass a beam through a desired aperture in a pattern group, according to the output of a deflector driving circuit 40, the block deflecting means 51 deflects the beam from the optical axis determined by lens system 36, 37, and projects the beam on the desired aprertutre in the pattern group. On the wafer 47 side, the beam current value is measured with a current measuring apparatus 49, and the deflection coordinate values of the mask deflectors 38A-38D are calibrated by using the mask coordinate system. Thereby highly precise calibration is realized, and exposure quality can be improved.

Description

[Detailed Description of the Invention] [Required] Regarding an electron beam exposure apparatus and an exposure method, an electrician beam capable of highly accurately calibrating the deflection coordinate values of a beam J and a mask coordinate system to improve exposure performance. The object of the present invention is to provide an exposure apparatus and an exposure method, the apparatus comprising: a mask plate having a pattern group consisting of two or more aperture patterns that shape the cross-sectional shape of a charged particle beam emitted from an electron gun; A lens system is arranged to sandwich the mask plate, and maintains the charged particle beam passing through the mask plate into a nearly parallel beam; On the side, the beam is deflected from the optical axis determined by the lens system,
The beam is irradiated to a desired aperture in the pattern group, and at the beam exit side of the mask plate, the beam passes through a block deflection means that returns the beam to the optical axis again after exiting the mask, and a desired aperture pattern of the mask plate. A reduction lens that reduces the cross section of the charged particle beam is placed near the sample, deflects the charged particle beam with a reduced cross section, and projects and irradiates it onto a predetermined position on the sample to expose a desired aperture pattern on the mask plate. The mask plate includes an irradiation deflection means and a current measurement means for measuring a current when the sample is irradiated with the charged particle beam, and the mask plate has a calibration mark pattern whose size and arrangement position are known in advance. , R? under at least two conditions in which the beam passing situation can be recognized by measuring the current value accompanying charged particle beam irradiation on the sample side using the current measuring means. Pass the beam through the mark pattern for calibration described in f, and determine the beam position and size on the mask plate from the deflection conditions of the block deflection means for each condition and the size and arrangement position of the mark pattern for calibration that are known in advance. Configure it to do so.

In addition, the method involves shaping the cross-sectional shape of a charged particle beam emitted from an electron gun using a mask plate having a pattern group consisting of two or more aperture patterns, and forming a cross-sectional shape of a charged particle beam that passes through the mask plate. Keeping the beam parallel, on the beam incidence side of the mask plate, deflect the beam from the optical axis determined by the lens system and irradiate the beam to a desired aperture in the pattern group, and on the beam exit side of the mask plate, After exiting the mask, the beam is returned to the optical axis again, the cross section of the charged particle beam that has passed through the desired aperture pattern of the mask plate is reduced, and the charged particle beam with the reduced cross section is deflected and projected onto a predetermined position on the sample. The size and location of the formation on the mask plate were known in advance by exposing the sample to the desired opening of the mask plate and measuring the current value accompanying the irradiation of the charged particle beam on the sample side. The beam is passed through the calibration mark pattern under conditions of at least 2i11 or more that allow the passage of the charged particle beam through the calibration mark pattern to be recognized, and the deflection conditions of the mask plate for each condition are known in advance. The beam position and size on the mask plate are determined from the size and arrangement position of the calibration mark pattern.

[Industrial Application Field] The present invention relates to an electron beam exposure apparatus and an exposure method,
More specifically, the present invention relates to an apparatus and method for forming fine patterns using electron beams.

In recent years, with the increasing density of integrated circuits, new exposure methods using electron beams have been studied and are now being used in place of photolithography, which has been the mainstream method for forming fine patterns for many years.

[Conventional technology]

A conventional electron beam exposure apparatus is a drawing apparatus that uses a variable rectangular beam to deflect and scan an electron beam on a sample wafer to draw a pattern.

This type of device uses pattern data, which is software, to
It is a device that has a baton generation function that creates hardware called patterns, but since the pattern is drawn by connecting rectangular shots, the smaller the pattern size, the more the number of exposures per unit area generally increases.
There is a problem that throughput decreases.

Therefore, in order to deal with this problem and obtain a realistic throughput even in exposure of ultra-fine patterns, a block exposure method has been proposed.

In other words, semiconductor devices that require ultra-fine patterns are
For example, in many cases, like 64MDRAM, most of the exposed area is a repetition of a certain basic pattern, although it is fine. If a basic pattern, which is a unit of a repeating pattern, can be generated in a single process regardless of its own complexity, it becomes possible to expose such a pattern with a constant throughput regardless of its fineness. .

Therefore, the block exposure method is a method in which the basic pattern described above is held on a transmission mask and irradiated with an electron beam to generate the basic pattern in one shot, and then the basic pattern is connected to repeatedly expose the pattern. .

An example of such an exposure method is IEEE TRANS,
0NELECTRON DEVICE vol, E
D-26 (1979) 663, and has a configuration as shown in FIG.

In the figure, an electron beam 2 emitted from an electron gun 1 passes through a first rectangular aperture 3 and is condensed by a lens 4, and is then deflected by a pattern selection deflector 5 placed at the image point of the crossover to form a stencil. An arbitrary pattern portion on the mask 6 is irradiated. The stencil mask 6 has a variable rectangular aperture 6A and a two-round alignment mark pattern 6B.
, a repeating basic pattern 6C is formed, and a lens 7 is placed close to the stencil mask 6. Therefore, after the cross section of the electron beam 2 is patterned by the stencil mask 6, it is returned to the optical axis by the converging action of the lens 7, passes through the deflector 8 for deflection, and is reduced in cross section by the reduction lens 9, and the projection lens 10 , passes through the deflection system 11 and is exposed onto the wafer 12. As a result, in the case of memory cells, for example, several cells are exposed in one shot.

However, in this method, the electrons 2 that have been deflected from the optical axis are returned to the optical axis only by the contraction of the lens 7, so depending on which pattern is selected, the electrons 2 will pass through different trajectories within the magnetic lens 7. I'm coming. In addition, in order to arrange as many patterns as possible on the stencil mask 6, it is necessary to make the electron trajectory pass through a part as far away from the optical axis as possible. The impact may be significant.

Therefore, the applicant of the present invention has previously proposed an apparatus having an electron optical system that solves this problem. The configuration of this device is the same as that of the embodiment described later, so a description thereof will be omitted. In this device, two lenses are installed above and below the stencil mask, and the electron beam is swung by an aperture pattern selection deflector above and below the stencil mask, and then deflected back so that the electron beam passes through the center of the upper and lower lenses. Selecting a pattern.

[Problems to be Solved by the Invention] By the way, in the block pattern transfer type electron beam exposure apparatus according to the above-mentioned prior application, an electron optical system is used so that the image of the first rectangular aperture is formed on the stencil mask. Set up the system, change this image position on the stencil mask using the entrance side mask deflector, select the desired block pattern position and pass the beam, or change the way the beam passes on the same block pattern. Since the configuration changes the shape and size of the beam cross section on the wafer, the input data to the incident side mask deflector and the aperture image position on the stencil mask (beam 1ffl
It is necessary to calibrate the relationship between overposition (excessive position) with high precision and to determine the size of the aperture image on the stencil mask, but this is difficult in practice, resulting in the problem that exposure performance cannot be improved. Ta.

For example, if the shot size is specified on the wafer with an accuracy of 0.01 μm, the reduction rate from the mask to the wafer is 1/100.
In this case, it is necessary to set the aperture image position (beam passing position) on the mask with an accuracy of 1 μm. For this calibration, a calibration mark pattern is formed on the mask. Note that the calibration mark pattern has a reduced reduction rate of 300 μm.
It is a rectangular pattern about the size of a mouth, and the size of this mark pattern is accurately determined at the time of forming the mask pattern.

On the other hand, the size of the aperture image on the stencil mask is rectangular with an opening of about 300 μm, and this size varies depending on lens conditions and cannot be specified accurately. However, as shown in Figure 7, the size is ~300
By passing a beam whose cross-sectional size is not determined through the calibration mark pattern (rectangular hole) 21 whose placement position (X, yo) is known in advance, the beam position and size are determined with an accuracy of within 1 μm. There is a need.

For example, the aperture image 22 on the stencil mask is expressed by the position of the lower left representative point B of the beam and the beam sizes x and y, and the deflector calibration is finally performed in this coordinate system. In beam calibration, the conditions under which the calibration mark pattern part 212 is normally adjusted are determined and adjusted.

However, with this method, unless the size of the calibration mark pattern and the beam size on the stencil mask are exactly equal, the beam passing conditions cannot be set with sufficient accuracy, resulting in a decrease in exposure performance. There is.

That is, FIG. 8 shows an example in which the size of the beam 23 is larger than the size of the calibration mark pattern 21.Although the beam positions are different in FIG. Since it is not possible to distinguish between the two, it is not possible to set beam passage conditions with sufficient accuracy. In addition, Fig. 9 shows an example in which the size of the beam 23 is smaller than the size of the calibration mark pattern 21, and in this case as well, although the beam positions are different in Fig. 9 (a) and (b), the amount of passing beam is almost the same. Since it is not possible to distinguish between the two, it is also impossible to set beam passage conditions with sufficient accuracy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electron beam exposure apparatus and an exposure method that can calibrate beam deflection coordinate values and a mask coordinate system with high precision and improve exposure performance.

[Means to solve the problem]

In order to achieve the above object, the electron beam exposure apparatus and exposure method according to the present invention include a pattern group consisting of two or more aperture patterns that shape the cross-sectional shape of a charged particle beam emitted from an electron gun. a mask plate; a lens system disposed across the mask plate to keep a charged particle beam passing through the mask plate into a substantially parallel beam; On the beam incidence side of the mask plate, the beam is deflected from the optical axis determined by the lens system, and the beam is irradiated onto a desired aperture in the pattern group.At the same time, on the beam output side of the mask plate, the beam is redirected to the optical axis after exiting the mask. a block deflection means for returning the charged particle beam to a reduced cross section; a reducing lens for reducing the cross section of the GI electron beam that has passed through the desired aperture pattern of the mask plate; The mask comprises an irradiation deflecting means for projecting irradiation onto a predetermined position on the sample to expose a desired aperture of the mask plate, and a current measuring means for measuring the current when the charged particle beam is irradiated onto the sample. Temporarily, it has a calibration mark pattern whose size and placement position are known in advance, and +j
Ij telegram? ! A charged particle beam is generated on the sample side by the lε measurement stage! ((By measuring the current value accompanying the radiation, the beam passing situation can be recognized and identified.The beam is passed through the calibration mark pattern under at least two conditions, and the block deflection means is adjusted for each condition. The beam position and size on the mask plate are determined from the deflection conditions and the size and arrangement position of a calibration mark pattern that is known in advance.

In addition, the method involves shaping the cross-sectional shape of the charged particle beam emitted from the electron gun using a temporary mask having a pattern group consisting of two or more aperture patterns, and forming the charged particle beam passing through the temporary mask into approximately Keeping the beam parallel, on the beam incidence side of the mask plate, deflect the beam from the optical axis determined by the lens system and irradiate the beam to a desired aperture in the pattern group, and on the beam exit side of the mask plate, After exiting the mask, the beam is returned to the optical axis again, the cross section of the charged particle beam that has passed through the desired aperture pattern of the mask plate is reduced, the charged particle beam with the reduced cross section is deflected, and projected onto a predetermined position on the sample. By exposing the sample to the desired opening pattern of the mask plate and measuring the current value associated with the irradiation of the charged particle beam on the sample side, the size and arrangement position of the formation on the mask plate can be known in advance. The beam is passed through the calibration mark pattern under at least two conditions under which the passing state of the charged particle beam through the calibration mark pattern can be recognized, and the mask temporary deflection conditions for each condition are known in advance. The beam position and size on the mask plate are determined from the size and arrangement position of the calibration mark pattern.

[Effect]

In the present invention, the current value accompanying the irradiation of the charged particle beam is measured on the sample side, and from this, the passage status of the charged particle beam through the calibration mark pattern formed on the mask plate and whose size and placement position are known in advance. A beam is passed through the calibration mark pattern under at least two conditions that can be recognized. The position and size of each person on the board are determined.

Therefore, since the mask coordinate system is known in advance, the beam deflection coordinate values can be calibrated with high precision using the mask coordinate system.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

1 to 5 are diagrams showing an embodiment of an electron beam exposure apparatus and an exposure method according to the present invention. FIG. 1 is a configuration diagram of this device. In this figure, 31 is an electron gun, 32 is an anode, 33 is an aperture, 34 is a lens, 35 is a deflector, 36 is a second lens, 37 is a third lens, and 38A
, 38B is an entrance mask deflector, 38C and 38D are exit mask deflectors, 39 is a stencil mask, 40 is a deflector drive circuit that provides deflection conditions to each deflector,
41 is a blanking electrode, 42 is a reduction lens, 43 is an aperture stop, 44 is a first projection lens, 45 is a second projection lens, 46 is a deflector (corresponding to irradiation deflection means), 47 is a wafer, and 48 is an electron beam. , 49 is a current measuring device (corresponding to current measuring means) for measuring the current value of the wafer 47.

The electron beam 48 becomes a nearly parallel beam between the second lens 36 and the third lens 37 (corresponding to a lens system), and an incident mask deflector 38 that selects the aperture pattern
8. 38B and exit mask deflector 38C, 38D
The electron beam 48 is placed under the stencil mask 39.
By swinging and swinging back, the mask pattern on the stencil mask 39 is selected one length without hitting the center of the lenses 36 and 37.

The stencil mask 39 (attached to the mask plate) has a structure as shown in Fig. 2, and the mask W plate is made of 291Si.
Semiconductors and metal plates, etc., are used. 2(a) is a plan view of the stencil mask 39, and FIG. 2(b) is a sectional view of the stencil mask 39. stencil mask 39
As shown in the cross-sectional view, the pattern forming portion is made thin by 119 mm, and a punched pattern is formed using O-etching technique. The stencil mask 39 has an electron beam irradiation area 3g+'1 and a pattern forming area 39B, and a non-repetitive pattern opening 39C and a pattern 39D are formed in the area 39B.

Also, a mask deflector 3 is placed on the stencil mask 39.
A plurality of pattern groups (sets of patterns), which are collections of patterns selectable by 8A to 38D, are prepared, and each set of patterns includes X, which supports the mask,
It can be moved near the electron optical axis using the Y stage. Furthermore, a mark pattern 61 for calibration, which will be described later, is formed on the stencil mask 39. In order to load the mask 39 onto this stage, a mask loading sub-chamber is provided which can be separated from the column body with a gate valve.

Mask deflectors 33A to 38D are block deflection means 5
1, and the block deflection means 51 is determined by lens systems 36 and 37 on the beam incidence side of the stencil mask 39 so as to pass the beam through a desired aperture in the pattern group based on the output of the deflector drive circuit 40. The beam is deflected from the optical axis to irradiate a desired opening in the pattern group, and the beam is returned to the optical axis after exiting the mask on the beam exit side of the stencil mask 39. In this embodiment, the beam current value is measured by a current measuring device 4 on the wafer 47 side.
9, the mask deflector 33A
The configuration is such that the deflection coordinate values of ~38D are calibrated using the mask coordinate system.

In the above configuration, in this embodiment, the sample (wafer) 47
On the side, the current value accompanying the irradiation of the electron beam 48 is measured by the current measuring device 4.
9, thereby making the stencil mask 39
The electron beam 48 is formed in a calibration mark pattern whose size and placement position are known in advance.
The beam is passed through the calibration mark pattern under at least two conditions under which the passing situation of the beam can be recognized, and the deflection condition of the stencil mask 39 for each condition and the size of the calibration mark pattern known in advance The beam position and size on the stencil mask 39 are determined from the arrangement position.

A concrete explanation of this is as follows.

Reference numeral 61 shown in FIG. 3 is a calibration mark pattern formed on the stencil mask 39, and its size Ll, L2 (~300 t-tm) and arrangement position (xo, YO) in the mask coordinate system are shown in FIG. is known in advance when creating the mask. However, L1≠■.

2 is also fine. The electron beam 48 is applied to this mark pattern 61.
The position of the beam origin and the beam sizes x and y in the mask coordinate system must be determined through .

Therefore, first, the beam current value was observed on the wafer 47 side, and the mark pattern 61 was set under conditions such that the beam was irradiated onto the beam patterns 62 and 63 shown in the position shown in FIG. Set the circumstances to pass. This can be done by finding the conditions under which the current value becomes zero when the electron beam 48 is slightly shifted to the +X side and +Y side, respectively. The deflection coordinates of the block deflection means 51 at this time (the coordinates at which the block deflection means 51 deflects the beam) are (XI, Yl'') and (Xz, Yz), respectively.
), the deflection coordinates of the professional deflection means 51 corresponding to the corner P point of the mark pattern 61 are (XI, yz
) can be decided. Therefore, since the coordinates of point P in the mask coordinate system are known in advance, the deflection coordinate value of the block deflecting means 51 can be calibrated in the mask coordinate system by using the relationship between the two.

In addition, the beam current value was observed on the wafer 47 side, and the mark pattern 61 was set under conditions such that the beam was irradiated onto the beam patterns 64 and 65 shown in the position shown in FIG. Set the circumstances to pass. For dirt, add a little +X to each electron beam 48.
What is necessary is to find the conditions under which the current value becomes zero when the current value is shifted to the -Y side. If the deflection coordinates of the block deflection means 51 at this time are (X3, Y3) and (x, , y,), the difference in deflection amount X3 Y4 is equal to the size Ll' of the mark pattern 61. It becomes a mouse by adding the size of the beam in the X direction. :1-Yarifiraision I
The deflection coordinates of the block deflection means 51 correspond to the mask coordinate system, and the size L of the mark pattern 61 is
Since l or L2 is known in advance, the size X of the beam in the X direction can be determined from this.

husband? Refrainion (2) Further, the beam current value is observed on the wafer 47 side, and a situation is set in which the beam passes through the mark pattern 61 under such conditions that the beam is irradiated onto the beam patterns 65 and 66 shown in the position shown in FIG. This increases the electron beam 48 by a little +
What is necessary is to find the conditions under which the current value becomes zero when shifted to the Y side and the -Y side. When the deflection coordinates of the block deflection means 51 at this time are respectively (Xl, Ys) and (X6, Y6), the difference in deflection amount x5 - y6 is equal to the size L2 of the mark pattern 61. It becomes a mouse by adding the size y in the X direction. In calibration (2), the deflection coordinates of the block deflection means 51 correspond to the mask coordinate system, and the mark pattern 610 size Ll or L2
Since this is known in advance, the size y of the beam in the X direction can be determined from this.

In this way, since the coordinates of point P in the mask coordinate system are known in advance, the deflection coordinate values of the block deflecting means 51 can be calibrated in the mask coordinate system by using the relationship between the two. Therefore, the beam deflection coordinate values and the mask coordinate system can be calibrated with high accuracy, and exposure performance can be improved.

〔Effect of the invention〕

According to the present invention, the beam deflection coordinate values and the mask coordinate system can be calibrated with high precision, and exposure performance can be improved.

[Brief explanation of drawings]

1 to 5 are diagrams showing one embodiment of the electron beam exposure apparatus and exposure method according to the present invention, in which FIG. 1 is a configuration diagram thereof, FIG. 2 is a diagram showing the structure of a stencil mask, and FIG. Figure 4 is a diagram explaining the method of calibration (■), Figure 5 is a diagram explaining the method of calibration (■), and Figures 6 to 9 are conventional FIG. 6 is a diagram showing its configuration, FIG. 7 is a diagram explaining its calibration method, and FIG. 8 is a diagram showing the case where the beam size is larger than the mark pattern size. , FIG. 9 is a diagram showing the case where the beam size is smaller than the mark pattern size. 31...Electron gun, 32...Anode, 33...Aperture, 34...Luns, 35...Deflector, 36. ...Second lens (lens system), 37...
...Third lens (lens system), 33A, 38B...
...Incidence mask deflector, 38C138D...
... Output mask deflector, 39 ... Stencil mask (mask plate), 40 ... Deflector drive circuit, 41 ... Blanking electrode, 42 ... - Reduction lens, 43... Diaphragm aperture, 44... First projection lens, 45... Second projection lens, 46... Deflector (irradiation deflection means), 47...
... wafer (sample), 48 ... electron beam, 49 ... current measuring device (current measuring means), 51.
...Block deflection means, 61...Mark pattern for calibration, 62-66...Beam pattern. A diagram showing the structure of a stencil mask in one embodiment of the pattern Figure 2B, (X, Y) A diagram explaining the calibration method in one embodiment Figure 6 explains the conventional calibration method. Figure 7 (a) (b) Figure 7 (a) (b)

Claims (2)

[Claims] (1) A mask plate having a pattern group consisting of two or more aperture patterns that shape the cross-sectional shape of the charged particle beam emitted from the electron gun, and the mask plate is placed across the mask plate and passes through the mask plate. a lens system that maintains the charged particle beam to be a substantially parallel beam; and a lens system that deflects the beam from an optical axis determined by the lens system on the beam incidence side of the mask plate so that the beam passes through a desired aperture in the pattern group. , block deflection means for irradiating the beam onto a desired aperture in the pattern group and returning the beam to the optical axis again after exiting the mask on the beam exit side of the mask plate; A reduction lens is placed near the sample to reduce the cross section of the charged particle beam, and the charged particle beam, whose cross section has been reduced, is deflected and projected onto a predetermined position on the sample to expose a desired aperture pattern on the mask plate. and current measuring means for measuring the current when the sample is irradiated with the charged particle beam, and the mask plate has a calibration mark pattern whose size and arrangement position are known in advance. By measuring the current value accompanying the irradiation of the charged particle beam on the sample side with the current measuring means, the beam is applied to the calibration mark pattern under at least two conditions under which the beam passage situation can be recognized. The beam position and size on the mask plate are determined from the deflection conditions of the block deflection means for each condition and the size and arrangement position of a calibration mark pattern known in advance. Beam exposure equipment. (2) The cross-sectional shape of the charged particle beam emitted from the electron gun is shaped by a mask plate having a pattern group consisting of two or more aperture patterns, and the charged particle beam passing through the mask plate is shaped into a nearly parallel beam. On the beam incidence side of the mask plate, the beam is deflected from the optical axis determined by the lens system to irradiate the beam to a desired aperture in the pattern group, and on the beam exit side of the mask plate, the beam is deflected from the optical axis determined by the lens system. The beam is returned to the optical axis again, the cross section of the charged particle beam that has passed through the desired aperture pattern of the mask plate is reduced, the charged particle beam with the reduced cross section is deflected, and projected onto a predetermined position on the sample. By exposing the sample to the desired aperture pattern of the mask plate and measuring the current value associated with the irradiation of the charged particle beam on the sample side, calibration is performed in which the size and arrangement position of the formation on the mask plate are known in advance. A beam is passed through the calibration mark pattern under at least two conditions under which the passing state of the charged particle beam in the mark pattern for use can be recognized, and the deflection conditions of the mask plate for each condition and the calibration are known in advance. An electron beam exposure method characterized in that the beam position and size on a mask plate are determined from the size and arrangement position of a mark pattern for exposure.