JP2001203149A - Beam adjustment device for charged particle beam apparatus, charged particle beam apparatus, and method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a beam adjustment device for a charged particle beam apparatus, with which the beam is accurately adjusted and the adjusting time can be reduced in the adjustment of positional relation between the particle beam in an object plane and in an image plane. SOLUTION: An electron beam 2 is scanned on openings 5 for beam adjustment by a deflector which is not illustrated. The scanning of the electron beam 2 changes coincidence situation between the image 3 and the openings 5 for beam adjustment, and this change changes the intensity of the electron beam 2 detected by a scintillator 6. The output of the scintillator 6 is converted into an electrical signal by a photomultiplier tube 7, and the signal is processed by a processor, which is not illustrated. Since not the reflected electrons but the very electrons of the electron beam are detected directly, the detected amount of the electron beam is large. In addition, since the scintillator 6 can be installed directly underneath the openings 5 for beam adjustment, viewing angle in the detection can be large, and the detection efficiency can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam adjusting device for adjusting a relative relationship between a beam position on an object surface of a charged particle beam and a beam position on an image surface to a predetermined relationship, and a charged particle beam device using the same.

[0002]

2. Description of the Related Art In recent years, fine processing techniques for semiconductors have been progressing year by year. Current exposure apparatuses mainly use light, but in order to carry out further fine processing, a shorter wavelength of light is required. However, there is a limit to shortening the wavelength, and although an exposure apparatus using X-rays has been considered, it has not been put to practical use at the present time because it is not easy to manufacture a reticle. From such a background, attention has been paid to transfer and exposure using a charged particle beam such as an electron beam.

FIG. 6 shows an example of a conventional electron beam exposure apparatus as an example of a charged particle beam apparatus. The electron beam 12 emitted from the electron source 11 irradiates the shaped opening 14 by the first irradiation lens 13. Electron beam 12 that has passed through forming aperture 14
Forms an image of the shaping aperture 14 on the reticle 17 by the second irradiation lens 15 and the third irradiation lens 16. A pattern to be transferred is formed on the reticle 17. The electron beam 12 that has passed through the reticle 17 is transferred to the wafer 20 by the first projection lens 18 and the second projection lens 19.
An image of the pattern on the reticle 17 is formed thereon.

[0004] In such an electron beam exposure apparatus,
The image of the pattern formed on the reticle 17 is
In order to accurately form an image at the target position of the reticle 17,
And the position of the electron beam at the position of the wafer 20 need to have a predetermined relationship. Adjusting the position of the electron beam so as to obtain such a predetermined relationship is described in reticle 1.
This is called alignment between the wafer 7 and the wafer 7. For this positioning, it is necessary to finally perform positioning between the position of the reticle 17 and the position of the wafer 20, but before that, a reticle stage or reticle on which the reticle 17 is mounted and a wafer on which the wafer 20 is mounted Usually, the stage is aligned.

[0005] An example of a conventional method of aligning a reticle stage and a wafer stage will be described with reference to FIG. In FIG. 7, an electron beam 2 focused by a projection lens 1 is transferred to a wafer stage 4 serving as an image plane.
Connect image 3 above. The image 3 is an image of a pattern for adjusting the projection optical system, and is usually a reticle (not shown) or a rectangular pattern row formed on a reticle stage. A beam adjusting pattern 9 is placed on the wafer stage 4 serving as an image plane.
Is provided. The beam adjustment pattern 9 is usually
An image 3 when a metal pattern is provided on a semiconductor or an uneven pattern is formed on a metal, and the projection optical system adjustment pattern is formed under ideal conditions of focus, magnification, rotation, astigmatism, and distortion. It has the same shape as.

[0006] The electron beam 2 is scanned over the beam adjustment pattern 9 by a deflector (not shown).
Generates reflected electrons according to the shape. The backscattered electrons are detected by a backscattered electron detector 10 installed on the lower surface of the projection lens 1. As the backscattered electron detector 10, a semiconductor detector is usually used. As the electron beam 2 scans, the degree of coincidence between the image 3 and the beam adjustment pattern 9 changes, and the intensity of the backscattered electrons detected by the backscattered electron detector 9 changes accordingly.

This will be described with reference to FIG. Statue 3
Moves as (a), (b), and (c) depending on the deflection position, depending on how the beam adjustment pattern 9 overlaps,
The signal waveform detected by the backscattered electron detector 10 is as shown in (d). This waveform shows the focus, magnification,
FIG. 9 shows signal waveforms when rotation, astigmatism, and distortion are ideal. When the focus, magnification, rotation, astigmatism, distortion, and the like of the image 3 deviate from ideal conditions and do not match the beam adjustment pattern 9. a waveform due to blurring and distortion of the image 3 is dull from triangular, also decreases the maximum intensity I _max. Projection lens, stigmator device or the like are adjusted such that the maximum intensity I _max of the waveform is maximized.

[0008] deflection position where the I _max is obtained is a position where the position of the reticle stage and the wafer stage are matched. Thus, when given a predetermined deflection, I _max is to adjust the relative positional relationship between the reticle stage and the wafer stage so as to obtain a predetermined position. Alternatively, the setting conditions of the deflector to provide a deflected position where I _max is obtained, as a state in which the optical axis suits the reticle stage and the wafer stage, so as to determine the operation of the deflector of this point as a reference.

[0009]

However, as described above, in the method of performing alignment by detecting the intensity of reflected electrons from the beam adjusting pattern 8 formed on the wafer stage, the reflected electrons are detected. Semiconductor detector 1
In the case of 0, a very large detection signal cannot be obtained because the expected angle for the backscattered electron detection cannot be made large.
Also, since the gain for incident electrons must be about 1000 times, the S / N ratio of the detection signal is not very good. For this reason, it is necessary to repeatedly scan or to lower the scanning speed to increase the S / N ratio, which has a problem that the adjustment time is long.

The present invention has been made in view of such circumstances, and when adjusting the positional relationship between charged particle beams on the object surface and the image surface, these positional relationships are accurately detected with a good S / N ratio. Accordingly, it is an object of the present invention to provide a beam adjustment device of a charged particle beam device capable of accurately performing beam adjustment and reducing the adjustment time, and a charged particle beam device using the same.

[0011]

According to a first aspect of the present invention, there is provided a beam adjusting apparatus for adjusting a relative relationship between a beam position on an object surface of a charged particle beam and a beam position on an image surface to a predetermined relationship. By irradiating the charged particle beam passing through the pattern provided at the object plane position to a charged particle beam shield or a charged particle beam scatterer having an opening of a predetermined shape provided at the image plane position, By scanning and forming an image of a pattern on the charged particle beam shield or the charged particle beam scatterer, and detecting and processing the charged particle beam passing through the aperture, the beam of the charged particle beam on the object plane It has a function of obtaining a relative relationship between the position and the beam position on the image plane, and adjusting the relative relationship between the beam position on the object plane of the charged particle beam and the beam position on the image plane to a predetermined relation based on the obtained relation. A beam controller of the charged particle beam apparatus (claim 1).

In this means, unlike the prior art, the image of the pattern provided at the object plane is scanned along the opening provided on the image plane, and the amount of the charged particle beam transmitted through the opening is measured. By performing the processing, the relative relationship between the beam position on the object plane and the beam position on the image plane is obtained. Therefore, unlike the conventional method using reflected electrons,
Since a large amount of charged particle beams can be detected, and a charged particle beam detector can be installed in the immediate vicinity of the opening, a prospective angle for detecting the charged particle beams can be increased.

Therefore, a large signal can be taken out of the detector with a good S / N ratio, and a sufficiently accurate signal can be obtained even when an image is scanned at a high speed. Therefore, the relative relationship between the beam position of the charged particle beam on the object plane and the beam position on the image plane can be quickly and accurately adjusted. As a means for matching the relative position between the beam position of the charged particle beam on the object plane and the beam position on the image plane, the method described in the prior art can be used as it is.

Needless to say, the charged particle beam shield and the charged particle beam scatterer are also relative, and the charged particle beam shield reflects most of the charged particle beams.
Shielded by absorption, but may scatter a part,
The charged particle beam scatterer may absorb and reflect a part of the charged particle beam.

[0015] A second means for solving the above-mentioned problems is as follows.
The first means, wherein the opening of a predetermined shape provided at the image plane position has the same shape as the image of the pattern provided at the object plane position at the image plane position ( Claim 2).

In this means, the maximum signal can be obtained when the image of the pattern provided on the object surface coincides with the aperture, so that a detection signal with a particularly good S / N ratio can be obtained.

A third means for solving the above-mentioned problem is as follows.
The first means or the second means, wherein the charged particle beam scatterer is formed of a thin film (Claim 3).

In order to accurately detect the relative relationship between the beam position on the object plane and the beam position on the image plane, it is necessary to make both the pattern provided at the object plane position and the aperture provided at the image plane position fine. is there. In particular, in a charged particle beam apparatus that performs reduction exposure transfer, the opening provided at the image plane position needs to be particularly fine.
If the charged particle beam scatterer is formed as a thin film in order to form such a fine opening, the fine opening can be accurately processed by a lithography technique or the like.

A fourth means for solving the above problem is as follows.
Any one of the first means to the third means for forming an image of the pattern on a charged particle beam scatterer, wherein the detector detects a charged particle beam passing through an opening; The distance from the image plane is at least three times the dimension of the opening (claim 4).

In order to detect the charged particle beam passing through the opening and accurately detect the relative relationship between the beam position on the object surface and the beam position on the image surface, the ratio of the width of the opening to the width between the openings is set to about 1 : 1 in many cases. In this means, the distance between the detector for detecting the charged particle beam passing through the aperture and the imaging surface is set to be three times or more the dimension of the aperture. The intensity ratio of the charged particle beam scattered by the charged particle beam scatterer to the charged particle beam that has spread sufficiently and smoothed before reaching the detector and that has passed through the width of the opening is not less than 10: 1. Become. With such a degree, it is easy to make the relative relationship between the beam position on the object surface and the beam position on the image surface the accuracy required for exposure transfer from the pattern of the amount of the charged particle beam detected.

A fifth means for solving the above problems is as follows.
A charged particle beam apparatus comprising any one of the first to fourth means (claim 5).

In this means, the relative position between the beam position of the charged particle beam on the object surface and the beam position on the image surface can be quickly and accurately adjusted, so that a fine pattern image can be accurately displayed on the image surface. An image can be formed, and the time for alignment is not required, so that the throughput is improved.

A sixth means for solving the above-mentioned problem is as follows.
A method of manufacturing a semiconductor device, comprising a step of exposing and transferring a pattern formed on a reticle or a mask to a wafer by using the fifth means.

In the present means, a fine pattern image can be accurately formed on the image plane, so that a semiconductor device with a high degree of integration can be manufactured with a high yield.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a main part of an example of a beam adjusting device of an electron beam exposure apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a projection lens, 2 is an electron beam, 3 is an image of a projection optical system adjustment pattern,
4 is a wafer stage, 5 is an opening formed in the wafer stage, 6 is a scintillator, and 7 is a photomultiplier tube.

The electron beam 2 focused by the projection lens 1 forms an image 3 on a wafer stage 4 serving as an image plane. The image 3 is an image of the pattern for adjusting the projection optical system.
It is a rectangular pattern row formed on a reticle or a reticle stage (not shown). A beam adjustment opening 5 is provided on the wafer stage 4 serving as an image plane. The beam adjustment aperture 5 has the same shape as the image 3 when the projection optical system adjustment pattern is formed under ideal focus, magnification, rotation, astigmatism, and distortion conditions.

The electron beam 2 is scanned over the beam adjusting aperture 5 by a deflector (not shown). With the scanning of the electron beam 2,
The degree of coincidence between the image 3 and the beam adjusting aperture 5 changes, and accordingly, the intensity of the electron beam 2 detected by the scintillator 6 changes. The output of the scintillator 6 is converted into an electric signal by a photomultiplier tube 7 and processed by a processing device (not shown). The relative relationship between the image 3 and the beam adjusting aperture 5 during scanning and the waveform of the obtained signal are the same as those shown in FIG. 8, and the beam adjusting pattern 8 in FIG. I just need.

However, in the present embodiment, since the electrons themselves of the electron beam can be directly detected instead of the reflected electrons, the amount of the detected electron beam increases. Since the scintillator 6 is used in combination with the photomultiplier tube 7 as a detector, the detection sensitivity can be increased. In addition, the scintillator 6 is connected to the beam adjusting aperture 5.
, It is possible to increase the expected angle of detection and increase the detection efficiency.

When these factors are combined, the sensitivity of the detector and the S / N ratio can be increased as compared with the conventional backscattered electron detection method. Therefore, the scanning speed can be reduced or the S / N ratio can be increased by repeating the scanning. Therefore, the relative positional relationship between the reticle or the reticle stage and the wafer stage can be detected quickly and accurately, and these positions can be aligned. Even if a semiconductor detector is provided instead of the scintillator 6 and the photomultiplier tube 7, the gain is slightly inferior, but the high S
/ N enables signal detection. Further, even if a conductor is provided instead of the scintillator 6 and the photomultiplier tube 7 and the current of the electron beam is directly detected, the signal can be detected although the gain, S / N and band are somewhat inferior.

After the pattern of the signal passed through the aperture is detected, the position of the reticle or the reticle stage and the wafer stage can be aligned by the same method as described in the section of the prior art.

By the way, in order to adjust the relative positional relationship between the reticle or the reticle stage and the wafer stage,
Since accuracy on the order of submicrons is required, the width of the beam adjusting aperture 5 must be very small.
Those having a thickness of about 100 nm are used. It is difficult to process such a fine opening into a thick wafer stage. Therefore, if a beam adjusting opening 5 is formed on a thin film using a silicon substrate or the like, a well-known lithography technique can be used, and a fine opening can be accurately manufactured.

FIG. 2 shows an example of the beam adjusting aperture 5 thus manufactured. In the following drawings, the same components as those shown in the preceding drawings are denoted by the same reference numerals, and description thereof may be omitted. In FIG. 2, 8 is
It is a Si substrate. An opening is provided in the wafer stage 4,
An Si substrate 8 having a beam adjusting opening 5 formed thereon is fixed thereon. A concave portion corresponding to the pattern of the beam adjusting opening 5 is formed on the surface of the Si substrate 8 using lithography technology, and the back side is anisotropically etched to form the Si substrate 8 having the shape shown in the figure. You.

A portion where the back side is anisotropically etched becomes a thin film, and a beam adjusting opening 5 is formed in this portion.
The portion where the back side is not anisotropically etched becomes a support member. In the drawing, the portion serving as the support member is written smaller than the thin film portion, but the portion serving as the support member is actually formed much larger. The structure shown in FIG. 2 is formed by turning over the thus formed Si substrate 8 and fixing it to the wafer stage 4.

When the beam adjusting aperture 5 is formed in the thin film, a part of the charged particle beam that has not passed through the opening is absorbed by the thin film, but most is scattered without being absorbed. Therefore, if the distance between the charged particle beam detector and the beam adjusting aperture 5 is short, the scattered radiation enters the detector before it spreads, forming a specially shaped pattern and deteriorating the S / N ratio. As the distance between the charged particle beam detector and the beam adjusting aperture 5 increases, the spatial density of the scattered radiation decreases and the amount detected by the detector decreases.

Normally, scattered radiation has a cos distribution, that is, an intensity distribution proportional to cos θ when the scattering angle is θ. On the other hand, since the ratio of the opening width of the beam adjusting aperture 5 to the interval therebetween is often 1: 1, taking these factors into account, the S / N ratio of the signal required for normal alignment is reduced. In order to make the S / N ratio equal to or more than 10, in FIG.
The distance d between the surface of the Si substrate (image plane) and the detection surface of the scintillator 6 (charged particle beam detector) needs to be at least three times the opening width x of the beam adjustment opening 5.

Hereinafter, an embodiment of a method for manufacturing a semiconductor device according to the present invention will be described. FIG. 4 is a flowchart showing an example of the semiconductor device manufacturing method of the present invention. The manufacturing process of this example includes the following main processes. Wafer manufacturing process for manufacturing a wafer (or wafer preparing process for preparing a wafer) Mask manufacturing process for manufacturing a mask to be used for exposure (or mask preparing process for preparing a mask) Wafer processing process for performing necessary processing on a wafer Wafer Chip assembling step of cutting out the chips formed on the chip one by one to make it operable Chip inspecting step of inspecting the resulting chips Each of the steps further includes several sub-steps.

Among these main steps, the main step that has a decisive effect on the performance of the semiconductor device is the wafer processing step. In this step, designed circuit patterns are sequentially stacked on a wafer to form a large number of chips that operate as memories and MPUs. This wafer processing step includes the following steps. A thin film forming step (using CVD, sputtering, etc.) for forming a dielectric thin film, a wiring portion, or a metal thin film for forming an electrode portion, which serves as an insulating layer. A lithography process of forming a resist pattern using a mask (reticle) in order to selectively process etc. An etching process of processing a thin film layer or a substrate according to a resist pattern (for example, using a dry etching technique) An ion / impurity implantation diffusion process Resist stripping step Inspection step of inspecting the processed wafer Further, the wafer processing step is repeated by a necessary number of layers to manufacture a semiconductor device that operates as designed.

FIG. 5 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. This lithography step includes the following steps. A resist coating step of coating a resist on a wafer on which a circuit pattern has been formed in the preceding step An exposing step of exposing the resist A developing step of developing the exposed resist to obtain a resist pattern Stabilizing the developed resist pattern The above-described semiconductor device manufacturing process, wafer processing process, and lithography process are well known, and will not require further explanation.

[0039]

As described above, according to the first aspect of the present invention, the relative relationship between the beam position on the object plane of the charged particle beam and the beam position on the image plane is quickly and accurately adjusted. be able to. In the invention according to claim 2, in addition to this, a detection signal having a particularly good S / N ratio can be obtained.

According to the third aspect of the present invention, in addition to these, a fine opening can be accurately processed by a lithography technique or the like. In the invention according to claim 4, in addition to these, the intensity ratio with the charged particle beam becomes 10: 1 or more, and a signal can be measured at a required S / N ratio.

According to the fifth aspect of the present invention, an image of a fine pattern can be accurately formed on the image plane, and the throughput is improved because no positioning time is required. In the invention according to claim 6, a semiconductor device with a high degree of integration can be manufactured with high yield.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a main part of an example of a beam adjusting device of an electron beam exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a beam adjusting aperture formed on a thin film.

FIG. 3 is a diagram showing a positional relationship between an image plane and a detector plane.

FIG. 4 is a diagram illustrating an example of a method for manufacturing a semiconductor device using the charged particle beam apparatus according to the embodiment of the present invention.

FIG. 5 is a diagram showing an example of a lithography step.

FIG. 6 is a diagram showing an example of a conventional electron beam exposure apparatus.

FIG. 7 is a diagram illustrating an example of a method of performing a conventional alignment of a reticle stage and a wafer stage.

FIG. 8 is a diagram showing a signal waveform and a forming process thereof in a conventional alignment of a reticle stage and a wafer stage.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Projection lens 2 Electron beam 3 Projection optical system adjustment pattern image 4 Wafer stage 5 Opening formed in wafer stage 6 Scintillator 7 Photomultiplier tube 8 Si substrate

Claims (6)

[Claims] 1. A beam adjusting device for adjusting a relative relationship between a beam position of a charged particle beam on an object plane and a beam position on an image plane to a predetermined relationship, wherein the charged particles have passed a pattern provided at the object plane position. A line is irradiated on a charged particle beam shield or a charged particle beam scatterer having an opening of a predetermined shape provided at an image plane position, and the image of the pattern is formed on the charged particle beam shield or the charged particle beam scatterer. And scan the image.
By detecting and processing the charged particle beam passing through the aperture, a relative relationship between the beam position on the object surface of the charged particle beam and the beam position on the image plane is obtained, and based on this, the beam on the object surface of the charged particle beam is obtained. A beam adjusting device for a charged particle beam apparatus, having a function of adjusting a relative relationship between a position and a beam position on an image plane to a predetermined relationship. 2. A beam adjusting device for a charged particle beam apparatus according to claim 1, wherein the aperture of a predetermined shape provided at the image plane position has an image at the image plane position of the pattern provided at the object plane position. A beam adjusting device for a charged particle beam device, wherein the beam adjusting device has the same shape as that of the charged particle beam device. 3. The beam adjusting device for a charged particle beam device according to claim 1, wherein the charged particle beam scatterer is formed of a thin film. Beam adjustment device. 4. A charged particle beam apparatus for a charged particle beam apparatus according to claim 1, wherein the image of the pattern is formed on a charged particle beam scatterer. A beam adjusting device for a charged particle beam apparatus, wherein a distance between a detector for detecting a line and the image forming plane is provided at a distance of at least three times a dimension of the aperture. 5. The method according to claim 1, wherein
A charged particle beam device comprising the beam adjusting device according to the above section. 6. A method for manufacturing a semiconductor device, comprising a step of exposing and transferring a pattern formed on a reticle or a mask to a wafer using the charged particle beam apparatus according to claim 5.