JP4407793B2 - Electrostatic chuck and equipment equipped with electrostatic chuck - Google Patents

Description

  The present invention relates to an electrostatic chuck mounted on a semiconductor manufacturing apparatus component and a flat panel display (FPD) manufacturing apparatus, and an apparatus on which the electrostatic chuck is mounted.

Conventionally, electrostatic chucks have the following types depending on their adsorption principle.
One provided a very large dielectric volume resistivity on the electrode, described by parallel plate capacitor model consisting of a thin, vital attraction voltage the thickness of the dielectric was very large electrode and the attracted member and Ruiwayuru Coulomb force type, the volume resistivity of the dielectric, the dielectric thickness, the surface roughness John Sen Rahbek type electrostatic expressing strong adsorption force caused John Sen Rahbeck effect by adjusting the predetermined range This is an electric chuck (see Patent Document 1).

Moreover, an electrostatic chuck in which the volume resistivity of the dielectric is large is disclosed (see Patent Document 2 and Patent Document 3). In this case, the attracting force is determined by the electrostatic capacity between the electrode of the electrostatic chuck and the wafer and the applied voltage, but the attracting force is generally weak and a very high voltage is required. For this reason, in order to provide unevenness on the surface, there is a limit for ensuring sufficient force to attract the object to be adsorbed, and the contact area between the object to be adsorbed and the electrostatic chuck surface , that is, the dielectric surface must be increased. I didn't get it.
The details found in Patent Document 3 are as follows.
An electrostatic chuck consists of an electrode, a dielectric, and an electrical connection means between the electrode and an external power supply. The dielectric and the silicon wafer that is the object to be adsorbed are in physical contact with each other, and a high voltage is applied from the external power supply. To do. At this time, a contact resistance is formed between the dielectric and the wafer, and a current flows. The current causes a voltage drop across the contact interface, and the potential difference induces a charge at the contact interface, resulting in a Coulomb attractive force. In other words, a region where the electrostatic chuck and the object to be attracted are in physical contact has a minute gap, the capacitance is large, and a large amount of electric charge is accumulated.
In this case, it was possible to carry out convex protrusion processing on the surface of the electrostatic chuck (see Patent Document 4).
Japanese Patent No. 3275901 JP-A-5-8140 JP-A-6-291175 Japanese Patent Laid-Open No. 7-153825

Even in the conventional electrostatic chuck described in Patent Document 4, it was possible to provide a convex protrusion on the electrostatic chuck suction surface, but the area ratio (contact area ratio) between the convex protrusion and the object to be attracted ) Was limited to 1-10%. Semiconductor and FPD processes are required to reduce the physical contact area between the attracted member and the electrostatic chuck as much as possible because they dislike particle generation and contamination on silicon wafers and glass substrates.
Although the Coulomb force type electrostatic chuck has good responsiveness to the voltage application of the attractive force, a high voltage is used and the attractive force is weak, so that the above-mentioned problem cannot be overcome.
The magnitude of the attracting force of the John Senlerbeck electrostatic chuck is mainly determined by the surface roughness of both the area where the electrostatic chuck and the attracted object are physically contacted. Therefore, even if the surface of the electrostatic chuck is smooth, the surface roughness on the attracted member side cannot be controlled, and it is difficult to reduce the contact area ratio to 1% or less even with the attractive force. Further, since the responsiveness of the adsorption force is mainly determined by the volume resistivity of the dielectric layer, residual adsorption is likely to occur due to the fact that the silicon wafer does not easily come off even when the power is turned off depending on the operating temperature and material selection.

  In order to solve the above problems, the present invention can reduce the physical contact area between the electrostatic chuck and the object to be attracted to the utmost limit. An object is to provide an excellent new type of electrostatic chuck.

上記構成とすることにより、静電チャックと被吸着体の物理的な接触が非常に小さくても実用的な吸着力が発現する静電チャックが得られる。そのため、コンタミネーションやパーティクルの付着を防ぐことができる。
また、上記構成とすることにより、本発明にかかる静電チャックのうち更に吸着力の応答性のよい静電チャックを得る条件を記載した。その結果、残留吸着力の減衰が速く、被吸着体の着脱が良好に行える静電チャックが得られる。
In order to achieve the above object, the present invention provides an electrode, an electrical connection means for the electrode, a dielectric having a plurality of convex portions formed on the surface and mounting an adsorbed body on the top surfaces of the plurality of convex portions, an electrostatic chuck wherein the volume resistivity of the dielectric is greater than 10 ⁵ Omega m, less than 10 ^{1 1} Omega m, and the total area of the plurality of convex upper surface, said plurality of projections the area of the dielectric surface in section is formed region, the ratio is 0.001% or more state, and are 0.1% or less, the thickness of the dielectric in the periphery of the convex portion d (m), the volume resistivity When ρ (Ωm) and the height δ (m) of the convex portion are satisfied, these satisfy the following formula 2 .

By the above structure, an electrostatic chuck practical adsorption force even physical contact of the electrostatic chuck and the adsorbent is very small is expressed Ru are obtained, et al. Therefore, contamination and particle adhesion can be prevented.
Moreover, the conditions for obtaining an electrostatic chuck with better responsiveness of the attracting force among the electrostatic chucks according to the present invention by using the above-described configuration are described. As a result, an electrostatic chuck can be obtained in which the residual attracting force decays quickly and the attracted member can be attached and detached satisfactorily.

As a preferred aspect of the present invention, the height of the plurality of convex portions is 2 μm or more and 45 μm or less .
By the above structure, an electrostatic chuck more practical adsorption force is expressed Ru are obtained, et al.

As a preferred aspect of the present invention, a ring-shaped convex portion having the same height as the plurality of convex portions provided outside the region where the plurality of convex portions are formed, and a region where the plurality of convex portions are formed. a gas supply holes provided, and further comprising a.
By setting it as the said structure, in order to gas-cool the to-be-adsorbed body, the ring-shaped convex part (seal ring) was provided in the electrostatic chuck surface. As a result, the gas can be cooled to about 100 torr, the gas sealing area of the attracted member and the electrostatic chuck is considerably wider than that of the conventional electrostatic chuck, and the in-plane temperature distribution of the attracted member becomes uniform.

As a preferred aspect of the present invention, a groove-shaped recess is provided in a region where the plurality of protrusions are formed and communicates with the gas supply hole, and the depth of the recess is 500 μm or less. It is characterized by.
With the above configuration, grooves were formed on the surface of the electrostatic chuck in order to shorten the gas filling time. As a result, the gas pressure controllability that greatly affects the temperature controllability of the adsorbent is improved.

As a preferred aspect of the present invention, the electrode is provided so as not to overlap the plurality of convex portions when viewed from the electric field direction .
By the above structure, it was to have a related to the shape of the electrode pattern and the electrostatic chuck surface pattern in order to further reduce the particle contamination with respect to the adsorbent of the electrostatic chuck according to the present invention. As a result, particles can be further reduced.

As a preferred aspect of the present invention, in a region where the plurality of convex portions are formed, a surface other than a portion where the plurality of convex portions are formed is covered with a conductive film.
By the above-described configuration, as described with the electrostatic chuck are covered with a conductive film on the bottom surface of the convex portion of the present invention. As a result, a new type of electrostatic chuck could be provided.

In a preferred aspect of the present invention, the electrode is a conductive substrate bonded directly to the dielectric .
With the above configuration, a new type of electrostatic chuck can be provided.

Further, when mounted on the apparatus used for the electrostatic chuck in a semiconductor device or the manufacture of flat panel displays Lee, device having excellent particle contamination can be provided.

  According to the present invention, an electrostatic chuck can be obtained in which a practical attracting force is exhibited even if the physical contact between the electrostatic chuck and the object to be attracted is very small. Further, contamination and particle adhesion can be prevented.

Examples of preferred embodiments of the present invention are shown below.
FIG. 1 is a typical embodiment of claim 2, and the diameter of the convex portion is φ0.25 mm as shown in FIG. 2, and this is continuously arranged at a position corresponding to each vertex of an equilateral triangle having a side of 8 mm. The height of the convex portion was 2, 5, 10, 15, 20, 25, 30, 45 μm. At this time, the ratio of the total area of the convex portions to the area of the electrostatic chuck surface , that is, the dielectric surface (contact area ratio) is about 0.1%. The electrostatic chuck has a gas supply hole, and is provided on the surface of the electrostatic chuck for the purpose of sealing gas, and is provided with a ring-shaped convex portion (seal ring) having the same height as the dot-shaped convex portion. The width of the seal ring was 0.5 mm.
The object to be adsorbed attracted to the electrostatic chuck can cause a uniform heat transfer between the object to be adsorbed and the electrostatic chuck by sealing a gas in a gap between the electrostatic chuck and the object to be attracted. Since the contact area ratio can be made as small as possible, the contact area of the cooling gas becomes a wider area than ever.

As the dielectric layer, a transition metal oxide was added to aluminum oxide to produce a ceramic dielectric, and a planar electrode was formed therein. This material has a relative dielectric constant of 8.7 at 1 KHz, a volume resistivity of 10 ¹⁰ Ωcm, and a thickness up to the dielectric surface and the included electrode of 1000 μm.
The total area of the plurality of dot-like convex portions can be reduced to about 0.001%. In that case, it is necessary to make the diameter of the convex portions 0.05 mm and the distance between the convex portions about 15 mm.
Although it is possible in principle to make it smaller than 0.001%, there is a case where the bottom surface of the convex portion bottoms out due to a manufacturing problem and deflection of the object to be adsorbed due to the adsorption force. If the contact area ratio is greater than 1%, the Johnsen-Leck Beck force generated at the top of the convex portion cannot be ignored, and the concern about particle contamination on the adsorbed body increases.
When the volume resistivity is 10 ¹³ Ωcm (10 ¹¹ Ωm) or more, the time for which charges are accumulated in the gap is very long, and it becomes very difficult to use. In the case of a bipolar structure in the following 10 ⁵ Omega m, the current flowing between the electrodes becomes very large, and although the area in physical contact is very small, no longer be ignored current from the contact portion Come. For this reason, problems such as having to considerably increase the capacity of the external power supply are likely to occur. Here, the volume resistivity is the volume resistivity at the temperature at which the electrostatic chuck is used, and the temperature used is in the range of about −50 to 500 degrees as the temperature generally used.

  A silicon wafer is placed on the electrostatic chuck as an object to be attracted, and an external power source is connected to the electrical connection means that is conducted to the electrode of the electrostatic chuck dielectric. Since the electrostatic chuck of this embodiment has a so-called bipolar structure with two electrodes, the attracted member does not need to be grounded. When the electrode has a single electrode structure, the object to be adsorbed must be grounded.

The above configuration is installed in a vacuum chamber (about 1 Pa), and the object to be adsorbed is pulled up in the vertical direction after electrostatic adsorption under vacuum, and the load at that time is divided by the area where the object to be adsorbed and the electrostatic chuck overlap. Power. The unit was torr for comparison with the gas pressure described later. As a result, it was found that the adsorption force shown in FIG. 3 was generated. It can be seen that the force generated at this time requires a higher voltage as the clearance (projection height) becomes wider. When the height of the convex portion was 45 μm, the applied voltage was relatively high at 3 KV, but there was an adsorption force of about 70 torr. This value is sufficient as compared with the gas pressure sealed when the object to be adsorbed is gas-cooled in an actual semiconductor manufacturing process, and can sufficiently withstand practical use.
In principle, the lower limit of the clearance may be as close to zero as possible, but if it is 2 μm or less, depending on the material of the dielectric layer and the dielectric layer manufacturing process, the height of the convex part, the surface roughness, and the surface waviness can be distinguished It becomes difficult. In this region, the protrusions can be formed by exposure, etching, and film forming techniques used in semiconductor manufacturing processes and the like.

In this embodiment, a silicon wafer is used as the adsorbent, but any material can be applied as long as it has conductivity. For example, even a substrate in which a thin film electrode is formed on a glass substrate can be similarly adsorbed.
Although the diameter of the protrusions was changed from 0.25 mm to 0.1 mm and the distance between the protrusions was changed from 8 mm to 15 mm, the relationship shown in FIG. 3 was generally maintained. The contact area ratio at this time is about 0.001%. The relationship shown in FIG. 3 was generally maintained when the diameter of the protrusions was 0.6 mm and the distance between the protrusions was 6 mm. The contact area ratio at this time is about 0.9%.

A preferred second embodiment of the present invention is shown below.
FIG. 4 shows an example in which only the scattered convex portions are provided on the surface. Ultraviolet exposure machines, UV exposure machines, and inspection machines often do not use cooling gas, and flatness is required. In this embodiment, since only the dot-like convex portions are formed on the electrostatic chuck, flatness processing is easy.

A preferred third embodiment of the present invention will be described below.
FIG. 5 is characterized in that a groove for diffusing gas is provided in the first embodiment. The groove is arranged to pass through the supply hole.
The time (filling time) until the pressure in the clearance space becomes uniform by arranging the groove is about 5 seconds when the height of the convex portion is 10 μm. The shape shown in FIG. 5 has a depth of 100 μm. When the groove was provided, it could be made within 1 second. FIG. 6 is a schematic sectional view.

If the depth of the groove is 500 μm or more, a discharge is likely to occur between the groove and the adsorbed body, and the adsorbing force may be weakened. The conditions for discharging are known as Paschen's law when the two objects to be discharged are metal, but the conditions are not known for dielectrics and conductors.
The inventors confirmed that when 3 KV was applied, even when the He gas was 100 torr and the groove depth was 500 μm, the discharge did not occur so much and as a result, the adsorption force could be secured at 100 torr or more.

A preferred fourth embodiment of the present invention will be described below.
FIG. 7 is an equivalent circuit of the electrostatic chuck according to the present invention. In an electrostatic chuck composed of a planar electrode, electrical connection means, and a dielectric having a smooth surface on which the object to be adsorbed is placed, it is applied from an external power supply when a voltage is applied to the object to be adsorbed In accordance with the equivalent circuit shown in FIG. 7, the generated voltage is a capacitance component C1 constituted by a gap between the surface of the dielectric (the bottom surface of the convex portion) and the surface of the electrostatic chuck (corresponding to the height of the convex portion). It is considered that most of the adsorption voltage V is divided at both ends of the. This is because the contact area between the electrostatic chuck and the object to be attracted is very small, and even if the contact resistance between the two is ignored, it is considered that there is not much influence. Electric charges are instantaneously accumulated by the voltage, and a Coulomb attractive force is generated. Charges Q1 to be accumulated at this time shows the transient characteristics for the resistance R2 of the dielectric.
If the time when the charge Q1 decays by 98% from the time of saturation is ts (seconds) from this transient characteristic,
ts = 1.731 × 10 ⁻¹¹ × ρ (1 + d / δ)
Is calculated. Here ρ is the volume resistivity of the dielectric ([Omega] m), d is the dielectric thickness (m), [delta] is the protrusion height (m). This is obtained by approximating the contact resistance between the electrostatic chuck and the attracted member to infinity with the calculation formula disclosed in Japanese Patent No. 3275901.
In a semiconductor process or the like, it takes time to exhaust process gas, cool a silicon wafer, etc., so that the attachment and detachment of the object to be adsorbed as an electrostatic chuck can be sufficiently secured for about 60 seconds after the process is completed. Therefore, the electrostatic chuck according to the present invention is
1.731 × 10 ⁻¹¹ × ρ (1 + d / δ) <60
An electrostatic chuck having such a parameter is excellent in detachability of the attracted member, and is a more preferable embodiment. FIG. 8 shows this embodiment. Especially dielectric volume resistivity and the gap (convex height) it was confirmed that significantly affect the removability.

A preferred fifth embodiment of the present invention will be described below.
FIG. 9 shows an outline of the electrode pattern of the electrostatic chuck according to the present invention. The cross-sectional view is as shown in FIG.
Semiconductor and FPD manufacturing processes are very hateful of particle contamination and contamination, but electrostatic chucks are prone to contamination because they are in direct physical contact with the object to be attracted. Since the electrostatic chuck according to the present invention can realize a very low contact area which has not been obtained in the past, particle contamination and contamination can be suppressed to a very low level. Table 1 shows the number of particles on the silicon wafer after the silicon wafer is adsorbed to the electrostatic chuck according to the present invention, which is remarkable compared with the conventional electrostatic chuck having a relatively low contact area ratio. The difference is obtained. In addition, particle reduction directly leads to suppression of chemical contamination.
Moreover, since the attracting force due to the John Senler-Beck effect is inherently acting on the projecting region in contact, the projecting portion is likely to be contaminated with particles. Therefore, in Example 6, electrode protrusions were provided so as to avoid the convex region in the electrode pattern of the electrostatic chuck. As a result, the force concentrated on the contact portion of the convex portion was relatively reduced, and particle contamination and contamination could be further suppressed. It is desirable to provide the electrode dent also directly under the seal ring provided on the outer peripheral portion.

  Table 1 shows the particle count of the silicon wafer by the adsorption of the electrostatic chuck of Example 1.

A preferred seventh embodiment of the present invention will be described below.
FIG. 11 shows the electrostatic chuck according to the present invention in which the surface (bottom surface of the convex portion) is covered with a conductive film. At this time, the charge itself can be adsorbed because it exists opposite to the conductive film and the adsorbent.

A preferred eighth embodiment of the present invention will be described below.
In FIG. 12, the electrostatic chuck itself according to the present invention is a conductor, and the convex portion is an insulating material. Also at this time, the charge itself can be adsorbed because it exists opposite to the conductive film and the object to be adsorbed.

A preferred ninth embodiment of the present invention will be described below.
The electrostatic chucks of Examples 1 to 7 of the present invention are used by being bonded to a substrate. The base is generally provided with a refrigerant channel, a gas channel, and the like. In some cases, the substrate itself becomes an electrode, and in this case , only the dielectric is bonded to the substrate as shown in FIG.

Representative plan view of the present invention Typical enlarged plan view of the present invention Graph of clearance (convex height), adsorption voltage, and adsorption force Representative plan view of the present invention 1 Representative schematic sectional view of the present invention Representative schematic sectional view of the present invention Equivalent circuit and schematic diagram of electrostatic chuck of the present invention Graph of residual adsorption force and decay time of electrostatic chuck of the present invention Schematic plan view of the electrode of the electrostatic chuck of Example 5 (also described convex position) Schematic sectional view of the electrostatic chuck of Example 5 Schematic sectional view of the electrostatic chuck of Example 6 Schematic sectional view of the electrostatic chuck of Example 7 Schematic sectional view of the electrostatic chuck of Example 9

Explanation of symbols

1 ... protrusions 2 ... protrusion bottom surface 3 ... gas supply holes 4 ... ring convex portion: the seal ring 5 ... recess: gas diffusion grooves 6 ... electrode 7 ... dielectric 8 ... the adsorbent 9 ... external power supply 10 ... electrode Nige 11 ... Projection position 12 ... Electrical connection means 13 ... Conductive film 14 ... Insulating projection 15 ... Conductive base 16 ... Base 17 ... Refrigerant flow path 18 ... Refrigerant inlet / outlet 19 ... Gas flow path

Claims (8)

Electrodes,
Means for electrical connection to the electrodes;
A dielectric having a plurality of convex portions formed on the surface and placing an adsorbed body on the top surfaces of the plurality of convex portions;
An electrostatic chuck comprising:
The volume resistivity of the dielectric is greater than 10 ⁵ Ω m, less than ^{10 1 1 Ω} m,
And the total area of the plurality of protrusions top, and area of the dielectric surface in the plurality of convex portions are formed region, the ratio is 0.001% or more state, and are 0.1% or less,
When the thickness d (m), volume resistivity ρ (Ωm), and height δ (m) of the convex portion around the convex portion are satisfied, these satisfy the following formula 1. Electrostatic chuck.

  The electrostatic chuck according to claim 1, wherein a height of the plurality of convex portions is 2 μm or more and 45 μm or less. A ring-shaped convex portion having the same height as the plurality of convex portions provided outside the region where the plurality of convex portions are formed;
A gas supply hole provided in a region where the plurality of convex portions are formed;
The electrostatic chuck according to claim 1, further comprising: A groove-shaped concave portion provided in a region where the plurality of convex portions are formed and communicating with the gas supply hole;
The electrostatic chuck according to claim 3, wherein a depth of the concave portion is 500 μm or less. The electrodes, the electrostatic chuck according to, in any one of claims 1 4, characterized in that is provided so as not to overlap with the plurality of protrusions when viewed from the direction of the electric field. 5. The surface of the region where the plurality of protrusions are formed, the surface other than the portion where the plurality of protrusions are formed is covered with a conductive film. 5. The electrostatic chuck according to claim 1. The electrodes, the electrostatic chuck according to any one of claims 1 to 6, wherein said dielectric is bonded electrically conductive base directly. A device used for manufacturing a semiconductor device or a flat panel display,
An apparatus on which the electrostatic chuck according to any one of claims 1 to 7 is mounted.

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