JP2922188B1 - Electron beam lithography system - Google Patents

Abstract

An anti-reflection mechanism having a structure in which thin plates are stacked is easily attached without narrowing a space between an objective lens and a sample. An electron beam provided with an anti-reflection mechanism on the lower surface of an objective lens facing a sample in order to prevent reflected electrons or secondary electrons emitted from the sample surface by the irradiation of the electron beam from re-reflecting to the sample side. In the drawing apparatus, the anti-reflection mechanism is configured such that a plurality of thin plates 1 having a plurality of openings are stacked, and a hole for connecting each of the openings to suppress emission of reflected electrons or secondary electrons is formed. The head of a screw for fixing the anti-reflection mechanism to the lower surface of the objective lens sinks toward the objective lens from the lower surface of the anti-reflection mechanism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam drawing apparatus used for drawing a fine pattern of a semiconductor device, and more particularly to an electron beam drawing apparatus with an improved antireflection structure above a sample surface.

[0002]

2. Description of the Related Art In a lithography process among the most advanced semiconductor manufacturing processes, an electron beam drawing apparatus using an electron beam is expected to become mainstream in the future. This is because electron beam lithography has a great advantage that a higher resolution than that obtained by lithography using light can be obtained.

In an electron beam lithography apparatus, as shown in FIG. 6, a resist 62 applied on a sample 63 such as a mask or a wafer is irradiated with an electron beam (incident electron) 71 through an objective lens 61 to further form a pattern. According to the beam 7
Scan 1. At this time, the reflected electrons 73 reflected or scattered on the sample surface are reflected again on the lower surface of the objective lens 61, and the re-reflected electrons 74 return to the sample surface. The resist 62 is also exposed by the re-reflected electrons 74. In other words, a so-called long-distance sensitizing effect occurs in which the resist 62 on the surface of the sample other than where the electron beam is incident by the re-reflected electrons 74 is generated.

Conventionally, a method has been adopted in which an anti-reflection plate made of a low atomic number material such as carbon is provided on the upper surface of the sample chamber (the lower surface of the objective lens) to suppress the generation of re-reflected electrons. However, as the required drawing accuracy increases, the use of a material having a low atomic number alone becomes insufficient in the anti-reflection effect. It has also been proposed to make the surface of the anti-reflection plate not a flat plate but a structure having a plurality of holes. In this case, it is desirable that the opening has a honeycomb structure in order to increase the opening ratio.

[0005] Making the anti-reflection plate having the opening structure as described above by ordinary machining requires a great deal of processing time, and the cost becomes extremely high. In addition, it is difficult to sufficiently increase the aperture ratio because the beam supporting the hole needs to be thick enough to withstand processing.

Accordingly, the present inventors have proposed an anti-reflection mechanism in which a plurality of thin plates having a plurality of openings are arranged one on top of another, and holes are formed by connecting the openings to suppress emission of reflected electrons or secondary electrons. doing. In this case, by using a thin plate, the aperture ratio can be easily increased by chemical etching or the like, and an antireflection plate can be manufactured at low cost.

However, in order to accurately process a thin plate by isotropic etching, its thickness needs to be about 0.2 mm or less. When such anti-reflection mechanisms are manufactured by stacking such thin plates, a method of fixing the thin plates becomes a problem.

That is, when an anti-reflection mechanism is manufactured by stacking thin plates, the head of a screw for fixing the anti-reflection mechanism to the lower surface of the objective lens protrudes more toward the sample than the lower surface of the anti-reflection mechanism. On the other hand, in order to reduce the aberration of the electron beam, the distance between the lower surface of the objective lens and the sample is reduced. In addition to the anti-reflection mechanism, there is a stage for transferring the sample and a reflected electron detector for beam adjustment. Various components such as a sensor (hereinafter abbreviated as SSD) and a sensor for measuring a sample position (hereinafter abbreviated as Z sensor) must be inserted. For this reason, there is little space in this part, and if an unnecessary protrusion such as a screw head is exposed, the design is greatly restricted.

In the conventional antireflection plate, measures for preventing re-reflected electrons are not sufficient in a region where reflected electrons measured by the SSD pass. Further, no measures have been taken to prevent re-reflected electrons in the portion through which the light from the Z sensor passes.

[0010]

As described above, in an anti-reflection mechanism having a structure in which thin plates are stacked, the head of a screw for fixing the anti-reflection mechanism protrudes toward the sample, and the lower surface of the objective lens There is a problem that the space between the sample and the sample is narrowed. In addition, measures for reducing re-reflected electrons in a region where reflected electrons measured by the SSD pass and a region where light from the Z sensor passes are not sufficient.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an anti-reflection mechanism having a structure in which thin plates are stacked, which can be easily attached to a lower portion of an objective lens. An object of the present invention is to provide an electron beam writing apparatus capable of preventing a space between a lens and a sample from being narrowed by a fixing member for attachment. Another object of the present invention is to provide an electron beam writing apparatus capable of reducing reflected electrons from an opening for an SSD or a Z sensor.

[0012]

(Structure) In order to solve the above problems, the present invention employs the following structure.
That is, according to the present invention, in order to prevent reflected electrons or secondary electrons emitted from the sample surface by the irradiation of the electron beam from being re-reflected to the sample side, an electron with an antireflection mechanism provided below the objective lens facing the sample. In the beam writing apparatus, the antireflection mechanism is configured such that a plurality of thin plates having a plurality of openings are stacked, and a hole for connecting each opening to suppress emission of reflected electrons or secondary electrons is formed. The anti-reflection mechanism is provided with a concave portion such that the lowermost part of a fixing member for fixing the anti-reflection mechanism to the lower part of the objective lens is located closer to the objective lens than the lower surface of the anti-reflection mechanism. It is characterized by the following.

Here, preferred embodiments of the present invention include the following. (1) The fixing member is composed of a screw, and the head of the screw is located closer to the objective lens than the lower surface of the antireflection mechanism.

(2) Of the plurality of thin plates constituting the anti-reflection mechanism, a portion of the thin plate near the sample is bent or bent, and the bent or bent portion is fixed by a fixing member. That you are.

(3) A backscattered electron detector is provided on the objective lens side of the antireflection mechanism, and openings are provided in a plurality of thin plates constituting the antireflection mechanism in a region where the electron beam irradiation position looks at the backscattered electron detector. And a hole is provided along a straight line connecting the electron beam irradiation position and a point on the backscattered electron detector.

(4) A plurality of thin plates constituting an anti-reflection mechanism are provided with holes through which the laser beam of the sample position detector passes, and the side walls of the holes are not visible from the electron beam irradiation position.

(Function) According to the present invention, a head such as a screw for fixing the anti-reflection mechanism having a structure in which thin plates are stacked to a lower portion of the objective lens sinks below the lower surface of the anti-reflection mechanism toward the objective lens. Therefore, when fixing the anti-reflection mechanism with a screw or the like, the head of the screw is embedded in the anti-reflection mechanism.
Therefore, the head of the screw does not protrude toward the sample, and the space on the lower surface of the objective lens can be used effectively.
Also, by providing holes along the trajectory of the backscattered electrons in portions where an opening is required in the antireflection plate for the SSD or Z sensor, it is possible to reduce the number of re-reflected electrons.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. Since the basic configuration of the electron beam lithography apparatus is not different from that of a known apparatus, the antireflection mechanism attached to the lower surface of the objective lens, which is a feature of the present invention, will be described here.

(First Embodiment) First, a thin plate 1 as shown in FIG. 1 is processed and formed. In order to reduce electron re-reflection, it is necessary to use a substance having a small atomic number Z. For this reason, this thin plate 1 may be directly processed by machining or etching a material having a small atomic number such as C or Be,
After processing Cu or Al by machining or etching, the surface may be coated with a substance having a small atomic number such as Be or C by vapor deposition, sputtering, plating, or the like.

In the case of coating, the thickness of the coating film is set to be larger than the reaching depth of the reflected electrons. In the case of an electron beam lithography apparatus with an acceleration voltage of 50 kV, the thickness may be about 10 μm or more. The coating may be performed for each thin plate, or the whole may be coated once after the thin plates 1 are stacked and attached as described below.

An opening 2 for passing an electron beam is formed in the center of the thin plate 1. The opening 2 is made small as long as the electron beam can easily pass therethrough. In an area 3 indicated by oblique lines in the drawing, an opening for absorbing reflected electrons is formed as described later. Further, an opening 4 for passing a positioning pin, an opening 5 for passing a screw, and an opening 6 for an optical sensor (Z sensor) for measuring the position of a sample are opened. In addition, a groove 7 for applying an adhesive for bonding the thin plates 1 to each other is formed.

The processing of the thin plate 1 is performed by etching or mechanical processing using lithography technology. When processing by etching, first, a resist is applied to both sides of the thin plate 1. Next, the opening drops the resist on both sides. On the other hand, groove 7
In the part, only the resist on the surface where the groove is dug is dropped, and the resist on the back surface is left. When etching is performed from both sides so that the resist in the opening is removed, only the one surface of the groove 7 where the resist remains on one surface is etched and the opposite surface is not etched.

When the process conditions are adjusted, the thin plate 1 is etched halfway, and a desired groove 7 is formed. A method of separately processing the groove 7 and the opening portion is also possible. In this case, only the groove 7 is formed by adjusting the etching process conditions. After that, an opening is made. In this method, etching is performed from both sides of the thin plate 1,
It is also possible to dig grooves on both sides. Characters or marks indicating the number of sheets when a plurality of thin sheets 1 are stacked are put on a part of the thin sheets 1.

The opening for absorbing the reflected electrons is formed in a honeycomb shape as shown in FIG. The region 3 where this opening is formed is a region where the reflected electrons spread. Assuming that the distribution of the reflected electrons is a cosine distribution, and assuming that the distance between the beam irradiation position and the antireflection plate is 10 mm, a region 3 where an opening is formed
When φ is set to φ60 nm, about 90% of the reflected electrons enter this opening region 3. Also, the diameter of the opening 2
R is set to be 1/3 or less of the thickness when the thin plates 1 are stacked. Further, the aperture ratio is set to be 80% or more.

FIG. 3 is a cross-sectional view when the thin plates 1 are stacked and combined. 9 denotes an SSD, and 10 denotes a Z sensor. The Z sensor 10 is installed outside the vacuum through a window, but is simply shown in FIG. The right is the laser light source and the left is the light receiving unit. Although not shown, the antireflection mechanism is fixed to the lower surface of the objective lens by screws.

As shown in FIG. 3, the opening region 3 for absorbing the reflected electrons is arranged so as to be a hole along the locus of the reflected electrons. That is, the opening regions 3 for absorbing the reflected electrons are arranged on a straight line passing through the beam irradiation position 8. Note that the thin plate 1 'furthest from the sample is not provided with the opening 3 for absorbing the reflected electrons. However, SSD
An opening is also provided in the thin plate 1 'at a place where an opening is required, such as in front of 9. By arranging the opening in this way, the reflected electrons enter the hole formed by connecting the openings, and if the aspect ratio of the hole is sufficiently large, most of the reflected electrons that have entered the hole exit the outside of the hole again. Will not come.

[0027] From the electron beam irradiation position 8 in the region expected to SSD9, to allow holes along the trajectory of the reflection electrons, an opening along a line connecting the point on the electron beam irradiation position 8 and SSD9 . Thus, it is possible to prevent the electrons re-reflected by the SSD 9 from flying back to the sample surface without significantly impairing the effective area of the SSD 9.
Such an opening is also effective in a region where an opening is required to increase the conductance for drawing a vacuum.

In the holes through which the light of the Z sensor 10 passes, openings 6 are respectively provided in the thin plates 1 along a straight line drawn from the beam irradiation position. By making the opening smaller than the opening 6, the influence of reflection from the side wall is reduced.

A plurality of thin plates 1 are bonded together. When bonding, the positioning is performed using the positioning pins 4 '.
This positioning pin 4 'may be removed after the thin plate 1 is bonded. As a method of bonding, there are a method in which an adhesive or a thin metal film is sandwiched between thin plates, and a method in which nothing is sandwiched between the thin plates and heat is applied to the thin plates.

When an adhesive is used, a groove 7 for applying the adhesive is formed at a place not overlapping the opening area. Also, the thin films are arranged with a gap so that the residual gas is exhausted. An adhesive is flowed into the groove 7, and the thin plates are bonded to each other in a state where the position of the thin plates is adjusted by passing the positioning pin 4 'through the hole formed by the opening 4 through which the pin is inserted. This adhesive should have a small degree of degassing so as not to deteriorate the degree of vacuum of the apparatus. In addition, the adhesive does not protrude from the groove 7 and does not adhere to a place where charge-up occurs. It is also possible to use a conductive adhesive or a metal thin film for laminating the thin plates 1.

As a metal thin film for bonding the thin plate 1, a soft metal such as Au, Ag, or In is suitable. Depending on the combination of materials, it may be better to heat the thin plate 1 after bonding. Since the thickness of the substance sandwiched between the thin plates 1 cannot be ignored, the design is performed in consideration of the thickness. Further, the thin plates can be joined to each other by diffusion bonding without sandwiching a substance for adhesion between the thin plates 1.

The laminated thin plate 1 is fixed with screws using holes 5 for screwing. Here, screw holes 5 are designed so that the heads of the screws are buried in the laminated thin plate. Specifically, an opening larger than the screw hole is provided so that the head of the screw is hidden in a plurality of thin plates on the sample side. This eliminates the need for exposing the head of the screw out of the anti-reflection mechanism.

A thin film substrate that transmits an electron beam or an X-ray is called a membrane. In the case of a device that irradiates a beam onto the membrane, a part of the irradiated beam passes through the membrane, and the antireflection plate is used as a sample. On the other side (the side opposite to the beam source). Therefore, in this case, the opening is formed so that a hole is formed along the trajectory of the electrons scattered by the sample.

As described above, according to the present embodiment, the screw hole 5 is designed so that the head of the screw is buried in the anti-reflection mechanism to which the thin plate 1 is attached. At the time of fixing, the head of the screw does not protrude toward the sample side, and the space on the lower surface of the objective lens can be used effectively. Also, holes are provided along the trajectory of the backscattered electrons in portions where an opening is required for the SSD or Z sensor, so that it is possible to reduce re-reflected electrons.

(Second Embodiment) FIGS. 4 and 5 are views for explaining a second embodiment of the present invention, and show the structure and fixing method of an antireflection mechanism. From the side close to the sample, several thin plates 1 were etched by etching as shown in FIG.
Make a cut in a U-shape as in 2, and make an opening inside the screw to pass the screw. 1 to 4 in the figure are the same as those in FIG. An opening is made in the remaining thin plate 1 as shown in FIG.

FIG. 5 is a sectional view showing a state in which these thin plates are fixed. 5 is the thin plate 1 shown in FIG. 4A, and 14 is the thin plate 1 shown in FIG. 4B.
The cut portion 12 in FIG. 4A is replaced with the opening 13 in FIG.
And fixed with screws 16. Since the head of the screw 16 is embedded in the anti-reflection mechanism, the space between the lower surface of the objective lens and the sample can be used efficiently. The cut portion 12 may be bent without bending, and the portion may be fixed with a screw. The number of sheets to be processed as shown in FIG. 4A among the plurality of thin plates 1 constituting the anti-reflection mechanism may be adjusted so that the heads of the screws are hidden in the screws and the thin plates are not distorted during assembly.

(Third Embodiment) FIG. 7 is a view for explaining another embodiment of a method for fixing an antireflection plate. (A) is the figure which looked at the antireflection plate from above. The anti-reflection plate has a rectangular shape and is made by stacking thin plates. The thin plates constituting the anti-reflection plate are aligned with each other by pins and then bonded by diffusion bonding. An opening for absorbing reflected electrons and a hole for passing the light of the Z sensor are provided in a circular area in the rectangular anti-reflection plate.

FIG. 4B is a sectional view showing a state where the antireflection plate is fixed. The side surface of the anti-reflection plate has a groove 16 as shown. The groove 16 is realized by adjusting the shape of the laminated thin plates. On the other hand, there is a fixing member 17 with a hook in the lens barrel. The groove 16 of the anti-reflection plate is inserted into the hook portion, and it is pushed to the back. Further, as shown in (c), the plate 18 is screwed so as to fix the side opposite to the abutted side. The fixing plate 18 does not protrude to the sample side from the antireflection plate.

In this fixing method, since the fixing member does not protrude from the anti-reflection plate toward the sample, the space between the sample and the anti-reflection plate can be used effectively. Further, the anti-reflection plate can be taken out from the side surface, and when dirt such as a resist adheres, the anti-reflection plate can be easily taken out of the apparatus and washed.

The present invention is not limited to the above embodiments. In the embodiment, the example in which the screw is used as the fixing member of the antireflection mechanism has been described. However, the present invention is not limited to the screw, and the fixing may be performed by another method. Further, the configuration of the optical system side of the electron beam writing apparatus is not limited at all, and the present invention can be applied to various apparatuses. Further, the material, shape, and the like of the thin plate constituting the anti-reflection mechanism can be appropriately changed according to specifications. Others
Various modifications can be made without departing from the scope of the present invention.

[0041]

As described above, according to the present invention, the antireflection mechanism in which the antireflection mechanism is fixed to the lower part of the objective lens is provided at the bottom of the antireflection mechanism by fixing the antireflection mechanism to the lower part of the objective lens. Since the lens is positioned closer to the objective lens than the lower surface, the fixing member does not protrude between the objective lens and the antireflection mechanism, and the antireflection mechanism can be compactly mounted on the lower surface of the objective lens. Also, S
By providing holes required for the SD and Z sensors along the trajectory of the reflected electrons, it is possible to reduce the number of reflected electrons from the openings for the SSD and the Z sensor.

[Brief description of the drawings]

FIG. 1 is a plan view showing the shape of a thin plate constituting an antireflection mechanism according to a first embodiment.

FIG. 2 is a schematic diagram for explaining a shape of an opening for preventing reflection in FIG. 1;

FIG. 3 is a sectional view showing the structure of an antireflection mechanism and peripheral components according to the first embodiment.

FIG. 4 is a plan view showing the shape of a thin plate used for an anti-reflection mechanism according to a second embodiment.

FIG. 5 is a sectional view showing a method of attaching an anti-reflection mechanism according to the second embodiment.

FIG. 6 is a diagram illustrating the principle of long-range interaction.

FIG. 7 is a diagram showing a method of attaching an antireflection plate by insertion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... The thin plate which comprises an anti-reflection mechanism 1 '... The thin plate located farthest from the sample 2 ... The opening for passing a beam 3 ... The area where the opening for reducing re-reflected electrons is formed 4 ... The opening for passing a positioning pin 5 An opening through which the fixing screw passes 6 An opening through which the light from the Z sensor passes 7 A groove for the adhesive 8 A beam irradiation position 9 An SSD 10 A Z sensor 12 A notch for fixing a thin plate 13 An opening 14 for fixing a thin plate 14 A thin plate with an opening for screwing 15 ... A thin plate with a cut for screwing 16 ... A groove for fixing the anti-reflective plate 17 ... A fixing member for the hook-shaped anti-reflective plate 18 ... A fixing plate

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shusuke Yoshitake 1 Toshiba R & D Center, Komukai, Kawasaki City, Kanagawa Prefecture (72) Inventor Kenji Oki 2-11 Ginza 4-chome, Chuo-ku, Tokyo No. Toshiba Machine Co., Ltd. (72) Inventor Tohru Tojo 4-2-1-11 Ginza, Chuo-ku, Tokyo Toshiba Machine Co., Ltd. (72) Inventor Jun Takamatsu 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki City, Kanagawa Prefecture, Ltd. In the Toshiba Research and Development Center (56) References JP-A-6-232032 (JP, A) JP-A-7-134964 (JP, A) JP-A-60-53021 (JP, A) JP-A-4-147611 ( JP, A) JP-A-60-226121 (JP, A) JP-A-3-99420 (JP, A) JP-A-63-196556 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , (DB name) H01L 21/027

Claims (5)

(57) [Claims] An electron device having an anti-reflection mechanism provided below an objective lens facing a sample in order to prevent reflected electrons or secondary electrons emitted from the sample surface by the irradiation of an electron beam from re-reflecting to the sample side. In the beam writing apparatus, the antireflection mechanism is configured such that a plurality of thin plates having a plurality of openings are stacked, and a hole for connecting each opening to suppress emission of reflected electrons or secondary electrons is formed. The antireflection mechanism is provided with a concave portion such that the lowermost part of a fixing member for fixing the antireflection mechanism to the lower part of the objective lens is located closer to the objective lens than the lower surface of the antireflection mechanism. An electron beam drawing apparatus characterized by the above-mentioned. 2. The electron beam writing apparatus according to claim 1, wherein the fixing member is formed of a screw, and a head of the screw is located closer to the objective lens than a lower surface of the antireflection mechanism. 3. A part of the plurality of thin plates constituting the anti-reflection mechanism, which is close to the sample is bent or bent, and the bent or bent portion is fixed by the fixing member. 3. An electron beam lithography apparatus according to claim 1, wherein the electron beam lithography is performed. 4. A reflection electron detector is provided on the objective lens side of the antireflection mechanism, and openings are provided in a plurality of thin plates constituting the antireflection mechanism in a region where an electron beam irradiation position looks at the reflection electron detector. 2. An electron beam writing apparatus according to claim 1, wherein said openings are connected to form holes along a straight line connecting an electron beam irradiation position and a point on a reflection electron detector. 5. A method for forming a hole through which a laser beam of a sample position detector passes through a plurality of thin plates constituting the anti-reflection mechanism ,
It is applied to the sheet along a straight line drawn from the beam irradiation position.
Each opening is provided, and it is directed from the sample position detector side to the sample side.
2. An electron beam lithography apparatus according to claim 1 , wherein the openings of the thin plate are formed sequentially smaller .