JPH0758677B2 - Sample stage used in electron beam lithography system used for manufacturing semiconductor devices - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electron beam drawing used for manufacturing a semiconductor device, which includes a sample holder on which a sample is mounted and a mounting table on which the sample holder is mounted. It belongs to the technical field of the sample stage of the device.

[Technical background of the invention and its problems]

With the trend of miniaturization and high integration of semiconductor elements, LSI
High-precision and high-speed pattern drawing performance is required for an electron beam drawing apparatus that creates a (large-scale integrated circuit) circuit pattern. In order to increase the speed of the electron beam writing system, the "continuous sample moving system" is adopted as the writing system, in which the stage on which the sample is placed is moved in one direction to perform pattern writing. It is an effective method to improve the deflection area of the electron beam, which was 100 micrometers, by an order of magnitude and expand it to about several millimeters. Further, in order to perform highly accurate pattern writing, it is necessary to reduce the aberration of the electron beam as much as possible. For this purpose, the objective lens located at the lowest stage of the electron optical lens barrel and the sample should be brought as close as possible to each other. It is effective to shorten the range.

In an ordinary electron beam drawing apparatus, the objective lens and the sample holder located at the uppermost stage of the sample stage are separated from each other by at most about 10 to several tens of millimeters. Since the magnetic field distribution formed by the objective lens leaks downward from the bore portion of the lens, the stage of the sample stage moves in the leakage magnetic field from the objective lens. The movable part of the conventional sample stage is made of a non-magnetic metal material such as an aluminum alloy, phosphor bronze, or titanium in order to prevent the stray magnetic field from affecting the electron beam. In this case, since the conductor moves in the magnetic field, an induced current is induced in the conductor such as the sample holder and the stage.

In an electron beam lithography system that employs the continuous-movement sample writing method to speed up pattern writing, if the distance between the objective lens and the sample is set to 10 mm, which is close to the practical limit, in order to minimize lens aberration, The strength of the magnetic field leaking to the holder side is as high as 30 gauss. At this time, if the sample holder and the stage are made of non-magnetic metal material, that is, conductors as in the past, the position of the electron beam projected on the sample is several times due to the induced current induced in those conductors. There is a drawback that the pattern drawing accuracy of the electron beam drawing apparatus is remarkably deteriorated due to the deviation of micrometer.

On the other hand, when the sample stage is made of ceramics or the like to prevent induction of induced current, electric charge is accumulated, the electric field is generated by the accumulated electric charge, the electron beam is bent, and the desired electron beam projection position is obtained. There is a problem during drawing, such as an error in the drawing. It is extremely difficult to release the charge accumulated in such a material due to the physical properties of the material. In order to prevent the accumulation of such charges, a person skilled in the art often uses a sample holder or a stage which is a metal coating on ceramics such as alumina (Al ₂ O ₃ ) and silicon nitride (Si ₃ N ₄ ). Was. However, as is well known, the ceramics and the like have high electrical insulation (specific resistance 10 ¹⁴
Ω · cm or more), which is often used as an insulating material, and the electrons of the electron beam are accumulated in the insulating material through the coated metal and are not released, so the effect of the coating is thin. Furthermore, when such a material is coated and used, the surface of the ceramic is rough (the characteristic of ceramics is that there are many agglomerates on the surface and it does not become a mirror surface like metal).
Insulation exposure is unavoidable due to pinhole-shaped coating defects caused by the scratches and scratches caused by tools during assembly and adjustment, and local charge accumulation occurs at that part.
After all, there was a problem that it could not be used.

[Problems to be Solved by the Invention]

The problem to be solved by the present invention is to configure at least the sample holder and the stage with a semiconductive material,
It is to solve the above-mentioned conflicting problems at the same time.

[Means for Solving the Problems] The present invention is, in order to solve the above problems, in the above technical field, at least the sample holder and the above-described object stage have a specific resistance of 10 ⁻³ to 10 ⁶ Ω · cm of semiconductivity. Made of a flexible material,
In addition, a means of grounding the sample holder and the above-mentioned object stand was taken.

[Action]

Since the resistivity of the sample holder and the stage is higher than 10 ^-3 Ωcm, the induced current generated in the sample holder or stage even when the sample stage moves in the leakage magnetic field from the objective lens. Can be suppressed to a small value, and the "deviation" at the irradiation position of the electron beam due to the induced current can be made sufficiently smaller than the resolution (about 0.05 μm) at the irradiation position of the electron beam exposure apparatus on a typical stage. can do.

Further, since the specific resistance of the sample holder and the stage is lower than 10 ⁶ Ωcm and they are grounded, it is possible to shorten the time for releasing the charges accumulated in the sample holder and the stage.
Charge accumulation does not occur even within the time of the electron beam irradiation cycle of every several tens of ns. Therefore, the influence of the potential of the sample stage on the ground potential of the electron optical system is small,
The “shift” at the irradiation position of the electron beam can be made sufficiently smaller than the resolution (about 0.05 μm) at the irradiation position of the electron beam exposure apparatus.

Furthermore, even when a semiconductive material with a specific resistance of 10 ^-3 to 10 ⁶ Ωcm is coated with a metal, pinhole-shaped coating defects due to the surface roughness of ceramics and tooling during assembly and adjustment Even if the semiconductive material is exposed due to scratches, the local accumulation of electric charge at that portion can be reduced.

Example of Invention

FIG. 1 is an embodiment of the present invention, in which 1 is a stage for placing a sample and moving in the X and Y directions, and 2 is a sample holder for holding the sample on the stage. . The stage 1 is provided with a plurality of sliding legs 3, and the end faces of the sliding legs 3 have a PT (not shown).
A sliding piece made of a material with a low friction coefficient such as FE (tetrafluoroethylene) is attached. Reference numeral 4 is a surface plate that serves as a reference in the vertical direction when the table is moved in the X and Y directions, and when the table 1 is moved, the sliding legs 3 move while sliding on the surface plate 4. 5 is an X reference guide, which is a stage 1
Is the horizontal reference when moving in the X direction. The stage base 1 is formed with an X reference guide groove 6 which penetrates the X reference guide 5 and has a sufficient space for disposing a preload roller described later. A clearance is provided between the upper surface of the X reference guide groove 6 and the upper surface of the X reference guide 5 so as not to contact each other when moving in the X direction. A Y reference guide groove 6 ′ is formed in the central portion of the surface plate 4. In the Y reference guide groove 6 ', a Y reference guide 7 serving as a horizontal reference when the stage 1 moves in the Y direction is mounted so as to be orthogonal to the X reference guide 5. X reference guide 5
A Y sliding rod 8 is fixed to the lower side of the X base 5 in a positional relationship orthogonal to the X reference guide 5. X reference guide 5
Rollers 9 which are rotatable around the central axis are attached to both ends of the table, and are arranged at the end portions of the surface plate and arranged in parallel to the Y direction as the table is moved in the Y direction. Roll on the Y guides 10 and 10 '. Also, due to the support of the rollers 9,
The lower surface of the X reference guide 5 has a slight clearance with respect to the surface plate 4 to prevent generation of frictional force when moving in the Y direction.

The stage 1 has an X drive shaft 11 and the Y sliding rod 8 has a Y drive shaft 11.
The drive shafts 12 are coupled to each other and transmit a driving force for moving the stage 1. When driving the stage 1 in the X direction, the stage 1 is moved along the reference surface 5a of the X reference guide 5.
And the X drive shaft 11 move integrally. When driving in the Y direction, along the reference surface 7a of the Y reference guide 7,
The stage 1, X reference guide 5, Y sliding rod 8, and Y drive shaft 12 move integrally.

FIG. 2 (a) is a view of an example of a method for pressing the stage 1 against the X reference guide 5 by applying a preload thereto from above. In the X reference guide groove 6, a slide piece 15 made of a low friction material such as PTFE is attached to a side surface 6a of the X reference guide 5 which faces the reference surface 5a. Further, a preload roller 14 supported by a leaf spring 13 and rotatable about a central axis is coupled to another side surface 5b of the X reference guide 5 which is parallel to the reference surface 5a. With this configuration, the sliding piece 15 is pressed against the reference surface 5a by using the pressing force from the leaf spring 13 as a preload.

FIG. 2 (b) is a view of an example of a method of pressing the Y sliding rod 8 against the Y reference guide 7 by applying a preload thereto from above. A sliding piece 15 made of a low friction material is attached to a sliding surface 8a of the Y sliding rod 8 which faces the reference surface 7a of the Y reference guide 7. Sliding surface 8a of Y sliding rod 8
A preload roller 14 supported by a leaf spring 13 and rotatable about a central axis is coupled to the other side surface 8b parallel to. With this configuration, the sliding piece 15 is pressed against the reference surface 7a by using the pressing force from the leaf spring 13 as a preload. The Y sliding rod 8 is fixed to the X reference guide 5 as described above,
Since the stage 1 is pressed against the X reference guide 5, when the Y slide rod 8 is driven in the Y direction by the Y drive shaft 12, the stage 1 also moves in the Y direction as a unit. To do.

In the configuration of the sample stage for the electron beam drawing apparatus described above, in the process of performing pattern drawing on the sample, the mechanical parts of the sample stage exposed to the electron beam projected from the electron optical lens barrel and its reflected electrons, The sample holder and the stage are made of a semiconductive material with a specific resistance of 10 ⁻³ to 10 ⁶ Ω · cm. Semi-conductive materials are roughly classified into ceramic materials and glass materials. Since ordinary ceramics are insulating substances, special processing such as introduction of impurities must be performed in order to make them semi-conductive substances. Specific semiconductive ceramic-based materials used in the present invention include SiC, LaCrO ₃ , BaTiO _{3 and the} like, and semiconductive glass-based materials include V ₂ O ₅ -P ₂ O ₅ based glass and Fe. ₂ O
_{There are 3-} PbO-B ₂ O ₃ based glass, etc., but for example, SiC has a surface of insulating SiC that is cut by about 2 mm in order to achieve the above resistance,
It is necessary to use a semiconductive material having the above resistance value. This is because the normal insulating SiC formed by sintering has different surface resistance values and internal resistance values, a high surface resistance value and a low internal resistance value. Further, when a mechanical component is manufactured from these semiconductive materials, a ceramic material is more advantageous than a glass material because it has better workability and moldability.

It has been considered that conventional ceramic materials cannot manufacture highly accurate parts due to shrinkage and thermal strain during sintering. However, with advances in fine ceramics technology in recent years, if grinding and lapping are performed after sintering, it becomes possible to obtain accuracy and stability superior to metal materials in ceramic materials. In this case, for example, even if the ceramic-based material moves at a velocity of 40 mm / s in a leakage magnetic field of 30 Gauss, the electron beam projection position error due to the induced current induced in the ceramic-based material is 6 × 10 ^{−. It} is only ⁶ micrometers, which is not a problem at all.

As described above, when the sample holder and the stage are made of a semi-conductive material, they are exposed to an electron beam and reflected electrons, so that charges are accumulated inside the material. The accumulated charges form an electric field, which causes an electron beam projection position error. Therefore, it is necessary to electrically ground the semi-conductive material by connecting a grounding conductor. In order to enhance the grounding effect, it is effective to coat the surface of the semiconductive material with a conductive thin film such as aluminum (Al) and connect the grounding conductor to the coated thin film. In this case, for example, assuming that the aluminum thin film moved at a velocity of 40 mm / s in a stray magnetic field of 30 gauss, the electron beam projection position error caused by the induced current induced in the aluminum thin film is the thickness of the aluminum thin film. On the other hand, it is considered that there is a relationship as shown in FIG. Therefore, when a semiconductive material is coated with, for example, an aluminum thin film and the film thickness is set to about 20 μm, the electron beam projection position error due to the induced current induced in this thin film is at most It can be 0.01 micrometer, which is not a problem for practical use.

〔The invention's effect〕

As described above, according to the present invention, even when the stage of the sample stage continuously moves in the leakage magnetic field from the objective lens of the electron beam drawing apparatus, at least the sample holder and the stage described above are provided. Is composed of a semiconductive material having a specific resistance of 10 ⁻³ to 10 ⁶ Ω · cm, and the sample holder and the above-mentioned platform are grounded, so that the sample holder and the above-mentioned platform are induced. The induced current and the accumulation of electric charge are extremely small, and the resolution of the electron beam exposure apparatus at the electron beam irradiation position (about
An electric field that causes an error larger than 0.05 μm) is not generated. That is, since there is no electric field at the irradiation position of the electron beam that causes an error larger than the resolution (0.05 μm) of the electron beam exposure apparatus, the positioning accuracy of the electron beam is improved and highly accurate pattern writing is possible. Become.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, and FIG. 2 (a).
Is a top view showing an example of a method of pressing the stage on the X reference guide by applying a preload, and FIG.
FIG. 3 is a top view showing an example of a method of applying a preload to a reference guide and pressing it, and FIG. 3 is a view showing a relationship between an aluminum film thickness and an electron beam projection position error. 1 ... Stage, 2 ... Sample holder, 3 ... Sliding legs, 4 ... Surface plate,
5 ... X reference guide, 5a ... X reference guide reference surface, 5b ... X reference guide side surface, 6 ... X reference guide groove, 6a ... X reference guide groove side surface, 6 '... Y reference guide groove, 7 ... Y reference guide, 7a
... Y reference guide reference surface, 8 ... Y sliding rod, 8a ... Y sliding rod sliding surface, 8b ... Y sliding rod side surface, 9 ... roller, 10,1
0 '... Y guide, 11 ... X drive shaft, 12 ... Y drive shaft, 13 ... Leaf spring, 14 ... Preload roller, 15 ... Sliding piece.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teruo Hosokawa 1839 Ono, Atsugi City, Kanagawa Pref., Atsugi Electro-Communications Research Laboratories, Nippon Telegraph and Telephone Public Corporation (72) Inoue Fujinami, 1839, Ono City, Atsugi, Kanagawa Prefecture Nippon Telegraph and Telephone Corporation Public Corporation Atsugi Institute of Electrical Communication (56) Reference JP-A-58-21327 (JP, A) JP-A-52-116078 (JP, A) JP-A-55-96951 (JP, A)

Claims (1)

[Claims] 1. A sample stage used in an electron beam drawing apparatus used for manufacturing a semiconductor device, comprising a sample holder on which a sample is mounted and a stage on which the sample holder is mounted. Resistivity with the above-mentioned platform
An electron beam drawing apparatus used for manufacturing a semiconductor device, characterized in that it is made of a semiconductive material of 10 ⁻³ to 10 ⁶ Ω · cm, and that the sample holder and the above-mentioned object stand are grounded. The sample stage to use.