JP2005032480A - Charged particle beam exposure apparatus and device manufacturing method using the apparatus - Google Patents

Abstract

Provided is a charged particle beam drawing apparatus capable of suppressing generation of other aberrations and exposing a desired pattern when correcting astigmatism of a reduction electron optical system.
A beam shaping optical system 2 that forms an image SI of a charged particle source that emits a charged particle beam, an aperture array 5 that forms an image of a plurality of charged particle sources from the charged particle source image SI, and an electrostatic lens 6 In order to correct the astigmatism generated in the reduced electron optical system 8 for reducing and projecting the images of the plurality of charged particle sources on the wafer 9 and the reduced electron optical system 8, the beam shaping optical system 2 is charged with the charged particle source image SI. And the first stigmator 3 for generating astigmatism.
[Selection] Figure 1

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charged particle beam exposure apparatus such as an electron beam exposure apparatus or an ion beam exposure apparatus mainly used for exposure of a semiconductor integrated circuit, and more particularly to an electron beam for directly pattern-drawing an exposed substrate such as a wafer with an electron beam. The present invention relates to an exposure apparatus or an electron beam exposure apparatus that illuminates an original such as a mask with an electron beam and projects and exposes an electron beam from the original onto an exposure substrate via a reduced electron optical system.
[0002]
[Prior art]
Conventional electron beam exposure apparatuses include a point beam type that uses a beam in the form of a spot, and a variable rectangular beam type that uses a variable size rectangular cross section.
[0003]
The point beam type electron beam exposure system uses a single electron beam for drawing, so it can be drawn with high resolution, but its throughput is low, so it is only for certain applications such as research and development and exposure mask manufacturing. not being used. In the variable rectangular beam type electron beam exposure apparatus, the throughput is one to two orders of magnitude higher than that of the point beam type. However, since a single electron beam is basically used for drawing, a fine pattern of about 0.1 μm is formed. In the case of exposing a pattern packed with a high degree of integration, there are still many problems in terms of throughput.
[0004]
As an apparatus for solving this problem, a pattern to be drawn is formed as a pattern transmission hole in a stencil mask, and the stencil mask is illuminated with an electron beam, whereby the pattern to be drawn is transferred to the sample surface via the reduced electron optical system. There is a stencil mask type electron beam exposure apparatus. In addition, a substrate having a plurality of apertures is illuminated with an electron beam, and a plurality of electron beams transmitted through the plurality of apertures are irradiated to a sample surface via a reduced electron optical system, and the plurality of electron beams are deflected. There is a multi-electron beam type exposure apparatus that scans a sample surface and draws a desired pattern by individually turning on / off a plurality of electron beams according to a pattern to be drawn (see, for example, Patent Document 1). Both of them have a feature that the area to be exposed at one time, that is, the exposure area is wider than that of the conventional case, so that the throughput can be further improved.
[0005]
[Patent Document 1]
JP-A-9-245708 (FIG. 1 etc.)
[0006]
[Problems to be solved by the invention]
However, since the area to be exposed at one time, that is, the exposure area, is wider than before, when correcting the astigmatism of the reduced electron optical system, using the astigmatism provided in the reduced electron optical system, other aberrations (Especially distortion) occurs. Therefore, it is difficult to form a desired pattern on the wafer.
[0007]
The present invention has been made in view of the above-described conventional problems, and when correcting astigmatism of a reduction electron optical system, charged particles that reduce exposure of other aberrations and can expose a desired pattern. An object of the present invention is to provide a line exposure apparatus.
[0008]
[Means to solve the problem]
To achieve the above object, in the present invention, in a charged particle beam exposure apparatus that exposes a substrate to be exposed using a charged particle beam, a first forming unit that forms an image of a charged particle source that emits a charged particle beam; Second forming means for forming images of a plurality of charged particle sources from the charged particle source image, a reduction electron optical system for reducing and projecting the images of the plurality of charged particle sources on the substrate to be exposed, and the reduction electron optical system In order to correct the astigmatism caused by the above, the first forming means has first astigmatism generating means for generating astigmatism when forming the charged particle source image.
[0009]
In the present invention, there is further provided second astigmatism generating means for generating astigmatism in the reduced electron optical system, and among the astigmatism generated in the reduced electron optical system, astigmatism that does not change during drawing is It is preferable that correction is performed by the first astigmatism generation means, and astigmatism that fluctuates is corrected by the second astigmatism generation means.
[0010]
The charged particle beam exposure apparatus of the present invention can be suitably used for manufacturing a device having a minute pattern such as a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, or a micromachine.
[0011]
[Action]
According to the present invention, the first astigmatism generating means generates astigmatism when the first forming means forms the charged particle source image to correct the astigmatism on the exposed substrate, When correcting the astigmatism of the reduction electron optical system, it is possible to suppress the occurrence of other aberrations and expose a desired pattern.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
As an example of the charged particle beam exposure apparatus, in the present embodiment, an example of an electron beam exposure apparatus is shown. The present embodiment is not limited to an electron beam, and can be similarly applied to an exposure apparatus using an ion beam.
[0013]
<Description of components of electron beam exposure apparatus>
FIG. 1 is a schematic diagram of a main part of an electron beam exposure apparatus according to an embodiment of the present invention. In FIG. 1, an electron beam generated by an electron gun (not shown) forms a crossover image 1 (hereinafter, this crossover image is referred to as an electron source 1). The electron beam emitted from the electron source 1 forms an image SI of the electron source 1 via the beam shaping optical system 2. At that time, astigmatism can be generated in the image SI by the first stigmator 3 which is a magnetic field type octupole stigmator. With this astigmatism, astigmatism of an electron beam image projected onto the wafer 9 described later can be corrected.
[0014]
The electron beam from the image SI becomes a substantially parallel electron beam by the collimator lens 4. The substantially parallel electron beam illuminates the aperture array 5 having a plurality of apertures. The aperture array 5 has a plurality of apertures, and the substantially parallel electron beam passes through these apertures and is divided into a plurality of electron beams. The plurality of electron beams divided by the aperture array 5 forms an intermediate image of the image SI by the electrostatic lens array 6 in which a plurality of electrostatic lenses are formed. A blanker array 7 in which a plurality of blankers are formed is disposed on the intermediate image plane.
[0015]
Downstream of the intermediate image plane, there is a reduction electron optical system 8 composed of two stages of symmetrical magnetic tablet lenses 81 and 82, and a plurality of intermediate images are projected onto the wafer 9. At this time, since the electron beam deflected by the blanker array 7 is blocked by the blanking aperture BA, the wafer 9 is not irradiated. On the other hand, since the electron beam that is not deflected by the blanker array 7 is not blocked by the blanking aperture BA, it is irradiated onto the wafer 9. That is, the blanker array 7 controls (on / off) whether or not the plurality of electron beams divided by the aperture array 5 are individually irradiated onto the wafer 9.
[0016]
In the lower tablet lens 82, a deflector 10 for simultaneously displacing a plurality of electron beams to desired positions in the X and Y directions, and an electrostatic type 8 for simultaneously adjusting astigmatism of the plurality of electron beams. A second stigmator 11 that is a pole stigmator and a focus coil 12 that simultaneously adjusts the focus of a plurality of electron beams are arranged. Reference numeral 13 denotes an XY stage on which the wafer 9 is mounted and can be moved in the XY directions orthogonal to the optical axis. On the XY stage 13, there is an electrostatic chuck 15 for fixing the wafer 9, and a semiconductor detector 14 having a single knife edge extending in the X and Y directions on the electron beam incident side for measuring the shape of the electron beam. Has been placed. By changing the output of the semiconductor detector 14 when the electron beam is scanned in the Y direction with respect to the single knife edge extending in the X direction, the shape of the electron beam in the X direction can be measured, and the single knife edge extending in the Y direction can be measured. On the other hand, by scanning in the X direction, the shape of the electron beam in the Y direction can be measured.
[0017]
The first stigmator 3 may be disposed anywhere between the light source 1 and the aperture array 5, but is preferably disposed between the light source 1 and the position where the image SI is formed. In this case, the first stigmator 3 generates astigmatism when the beam shaping optical system 2 forms the charged particle source image SI.
[0018]
<Description of system configuration and drawing method>
FIG. 2 shows a system configuration diagram of the present embodiment.
The first stigmator control circuit 21 adjusts the focal length difference in the orthogonal direction of the first stigmator 3 to control the astigmatism of the electron source image SI. The blanker array control circuit 22 A circuit that individually controls a plurality of blankers constituting the array 7, a deflector control circuit 23 is a circuit that controls the deflector 10, and a second stigmeter control circuit 24 is an orthogonal direction of the second stigmeter 11. A circuit for controlling the astigmatism of the reduction electron optical system 8 by adjusting the difference in focal length, an electron beam shape detection circuit 25, a circuit for processing a signal from the semiconductor detector 14, and a focus control circuit 26 for focusing. The stage drive control circuit 27, which controls the focal position of the reduction electron optical system 8 by adjusting the focal length of the coil 12, A control circuit for controlling the XY stage 13 in cooperation with a laser interferometer (not shown) for detecting a. The main control system 28 controls the plurality of control circuits and manages the entire electron beam exposure apparatus.
[0019]
An explanatory diagram of the drawing method of this embodiment is shown in FIG.
The main control system 28 commands the deflection control circuit 23 based on the exposure control data, deflects a plurality of electron beams by the deflector 6, and commands the blanker array control circuit 22 to expose (draw) on the wafer 9. The blankers of the blanker array 7 are individually turned on / off according to the pattern. Each electron beam scans and exposes a corresponding element exposure region (EF) on the wafer 9 as shown in FIG. Since the element exposure area (EF) of each electron beam is set so as to be adjacent in two dimensions, as a result, a subfield (SF) composed of a plurality of element exposure areas (EF) that are exposed simultaneously is formed. Exposed.
[0020]
In one embodiment, the number of electron beams is 32 × 32 = 1024, and each electron beam draws an element exposure area (EF) of about 2 μm square. Here, the diameter of one electron beam is about 60 nm on the wafer 9. One subfield (SF) is formed by 32 × 32 = 1024 element exposure regions. The size of one subfield (SF) is about 64 μm square.
[0021]
The main control system 28 instructs the deflection control circuit 23 to deflect the plurality of electron beams by the deflector 10 in order to expose the next subfield (SF2) after exposing the subfield (SF1). At this time, the subfield changes due to the deflection, so that the aberration when each electron beam is reduced and projected via the reduction electron optical system 8 also changes. Based on a command from the main control system 28, the second stigmeter control circuit 24 performs correction so that this aberration becomes constant. This aberration can be measured as the shape of an electron beam using the semiconductor detector 14 and a knife edge extending in the XY direction. The relationship between the deflection position and the beam shape is obtained in advance, and astigmatism that changes due to deflection by subfield switching or the like during drawing is controlled by the second stigmator 11 under the command of the second stigmometer control circuit 24. Use to correct.
[0022]
In the above embodiment, when a subfield group of about 2 mm square consisting of 32 × 32 = 1024 subfields of about 64 μm square is exposed, the XY stage is moved about 2 mm to expose the next 1024 subfield groups. To do. Although not shown, the deflector 10 includes a main deflector used when the deflection width is wide and a sub-deflector used when the deflection width is narrow. The main deflector is an electromagnetic deflector. The sub deflector is an electrostatic deflector. Scanning at the time of drawing is performed by an electrostatic sub-deflector, and sub-field switching is performed by an electromagnetic main deflector.
[0023]
<Description of operation>
The operation of the electron beam exposure apparatus of this embodiment will be described with reference to FIG. For wafer processing of the exposure apparatus, the main control system 22 executes the following steps.
[0024]
(Step 1) The main control system 28 deflects a plurality of electron beams to the subfield SF1 by the deflector control circuit 23, and only the center beam located at the approximate center of the subfield by the electron beam shape detection circuit 25 is a semiconductor. The detector 14 is scanned over the knife edge, and the beam diameters in the X and Y directions of the beam are measured. Further, the focus is changed by the focus control circuit 26, and the beam diameters in the X direction and Y direction of the beam are measured. A focus position at which the beam diameter in the X direction is minimum is Fx, a focus position at which the beam diameter in the Y direction is minimum is Fy, and the astigmatism of the subfield is Fx−Fy. The subfield is sequentially changed, and the astigmatism of the center beam for each subfield is detected.
[0025]
(Step 2) By step 1, the astigmatism of the center beam for each subfield as shown in FIG. 5 is obtained. From this, the maximum astigmatism amount (H_AS) and the minimum astigmatism amount (L_AS) are obtained, and the average astigmatism amount (M_AS = (H_AS + L_AS) / 2) is calculated.
[0026]
(Step 3) The astigmatism obtained by subtracting the average astigmatism from the astigmatism for each subfield is set as a variable astigmatism for each subfield. As a result, the average astigmatism can be regarded as a non-fluctuating astigmatism during rendering with subfield changes, and the variable astigmatism can be regarded as a fluctuating astigmatism.
[0027]
(Step 4) The average astigmatism amount is corrected by the first stigmator 3. The function of the first stigmator will be described with reference to FIG. When the driving of the first stigmator is off, the electron source image SI is substantially circular, and the plurality of electron source images on the blanker array are also substantially circular. However, due to astigmatism of the reduction electron optical system 8, the plurality of electron source images on the wafer 9 are elliptical. On the other hand, when the drive of the first stigmator is turned on, the electron source image SI becomes an ellipse so as to cancel the astigmatism of the reduction electron optical system 8, and at the same time, a plurality of electron source images on the blanker array also become an ellipse. Become. As a result, the plurality of electron source images on the wafer are substantially circular. Further, when correcting the astigmatism, the astigmatism is generated in the original electron source image SI, so that other aberrations of the reduced electron optical system 8 do not occur.
[0028]
Since the first stigmator 3 adjusts the amount of astigmatism before the electron source image SI is reduced, the second stigmator 11 is used when correcting the astigmatism of the same reduced electron optical 8 from the relationship of the vertical magnification. Compared to, a larger astigmatism must be added. Therefore, the first stigmator 3 is an electromagnetic type that can increase the astigmatism drive amount. On the other hand, the second stigmator is an electrostatic type. The electromagnetic type is less responsive than the electrostatic type. Therefore, in this embodiment, the average astigmatism is corrected by the magnetic field type first stigmator 3 and the fluctuation astigmatism is corrected by the electrostatic type second stigmator 11.
[0029]
(Step 5) The wafer 9 is carried into the stage 13.
(Step 6) The main control system 28 deflects the plurality of electron beams to the subfield to be exposed by the deflector control circuit 23.
(Step 7) At the same time as Step 5, the main control system 28 instructs the second stigmator to correct the fluctuation astigmatism corresponding to the subfield to be exposed.
[0030]
(Step 8) Draw a subfield to be exposed.
(Step 9) When drawing of all the subfields is completed, the process proceeds to Step 10; otherwise, the process returns to Step 6.
(Step 10) The wafer 9 is unloaded from the stage 13.
[0031]
According to this embodiment, it is possible to correct astigmatism of the reduction electron optical system while suppressing the occurrence of other aberrations. Thereby, a desired fine pattern can be exposed on the wafer. Therefore, if a device is manufactured using this apparatus, the device can be manufactured with a higher yield than before.
[0032]
<Device production method>
Next, an embodiment of a device production method using the electron beam exposure apparatus described above will be described.
[0033]
FIG. 7 shows a flow of manufacturing a microdevice (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, a micromachine, etc.). In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (exposure control data creation), exposure control data for the exposure apparatus is created based on the designed circuit pattern. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the wafer and the exposure apparatus to which the prepared exposure control data is input. The next step 5 (assembly) is referred to as a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 4, such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), and the like. including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, the semiconductor device is completed and shipped (step 7).
[0034]
FIG. 8 shows a detailed flow of the wafer process. In step 11 (oxidation), the wafer surface is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern is printed onto the wafer by exposure using the exposure apparatus described above. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.
[0035]
By using the manufacturing method of the present embodiment, a highly integrated semiconductor device that has been difficult to manufacture can be manufactured at low cost.
[0036]
【The invention's effect】
As described above, according to the charged particle beam exposure apparatus of the present invention, when correcting astigmatism of the reduction electron optical system, it is possible to reduce the occurrence of other aberrations and expose a desired pattern. . Moreover, if a device is manufactured using this apparatus, a device having a higher yield than conventional devices can be manufactured.
[Brief description of the drawings]
FIG. 1 is a view showing an outline of a main part of an electronic exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a system according to the present embodiment.
FIG. 3 is a diagram illustrating a drawing method according to the present embodiment.
FIG. 4 is a view for explaining an exposure operation of the present embodiment.
FIG. 5 is a diagram for explaining an average astigmatism amount;
FIG. 6 is a diagram illustrating the function of a first stigmator.
FIG. 7 is a diagram illustrating a flow of a device manufacturing process.
FIG. 8 is a diagram for explaining the wafer process in FIG. 7;
[Explanation of Symbols] 1: Electron source, 2: Beam shaping optical system, 3: First stigmator, 4: Collimator lens, 5: Aperture array, 6: Electrostatic lens array, 7: Blanker array, 8: Reduction Electron optical system, 9: wafer, 10: deflector, 11: second stigmator, 12: focus coil, 13: XY stage, 14: semiconductor detector, 15: electrostatic chuck.

Claims (3)

In a charged particle beam exposure apparatus that exposes a substrate to be exposed using a charged particle beam,
First forming means for forming an image of a charged particle source emitting a charged particle beam;
Second forming means for forming images of a plurality of charged particle sources from the charged particle source image;
A reduced electron optical system for reducing and projecting images of the plurality of charged particle sources onto the substrate to be exposed;
In order to correct astigmatism generated in the reduced electron optical system, the first forming means includes first astigmatism generating means for generating astigmatism when forming the charged particle source image. Charged particle beam exposure system. Second astigmatism generating means for generating astigmatism in the reduced electron optical system is further provided, and among the astigmatism generated in the reduced electron optical system, astigmatism that does not change during drawing is the first astigmatism. 2. The charged particle beam exposure apparatus according to claim 1, wherein the astigmatism is corrected by a point generation unit, and fluctuating astigmatism is corrected by the second astigmatism generation unit. 3. A device manufacturing method for manufacturing a device using the charged particle beam exposure apparatus according to claim 1.

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