JP3933289B2 - Electrostatic chuck - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic chuck having an insulating layer on an electrode and electrostatically adsorbing an object to be adsorbed such as a semiconductor wafer on the insulating layer by applying a voltage to the electrode.
[0002]
[Prior art]
In a semiconductor manufacturing apparatus, an electrostatic chuck is used as a jig for attracting and fixing a substrate to be processed such as a semiconductor wafer in a reduced pressure atmosphere. The electrostatic chuck has an electrode and an insulating layer provided on the electrode, and places the substrate to be processed on the insulating layer, and electrostatically attracts the substrate to be processed by supplying power to the electrode. is there.
[0003]
As a material for such an electrostatic chuck insulating member, a resin such as polyimide or a ceramic such as alumina is known.
[0004]
[Problems to be solved by the invention]
However, electrostatic chucks tend to attract dust and dirt when attracting semiconductor wafers by electrostatic attraction, and when the semiconductor wafer is brought into contact with the electrostatic chuck, the back surface is contaminated by particles. There is a problem that it is easy. On the other hand, it has been reported that the contact area between the insulating layer and the non-adsorbed material is reduced by processing the surface of the insulating layer such as ceramics to form the protrusion, but the protrusion is formed by processing. In this case, there is a problem that particles are likely to be generated from the end of the protrusion.
[0005]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electrostatic chuck in which the adsorbed object is less contaminated.
[0006]
[Means for Solving the Problems]
The present inventors have made intensive studies to solve the above problems, by covering the entire surface of a resin sheet, not only particles such as dust and dirt, the projection when processed to form a protrusion It has been found that the problem of particles generated from the end is also solved.
[0007]
The present invention has been made based on such knowledge, and has an electrode and an insulating layer provided thereon, and by applying a voltage to the electrode, an adsorbent is placed on the insulating layer. an electrostatic chuck for electrostatically attracting, has a projection formed by pasting a resin tape to the surface of the electrode, the electrode having a protrusion is covered by the resin sheet functions as an insulating layer, the resin sheet is a surface An electrostatic chuck is provided in which irregularities corresponding to the protrusions are formed .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
1 and 2 are sectional views showing an electrostatic chuck according to an embodiment of the present invention. FIG. 1 shows a monopolar type, and FIG. 2 shows a bipolar type.
[0009]
The monopolar electrostatic chuck 1 of FIG. 1 is configured by providing an electrode 2 between upper and lower insulating layers 3 and is fixed on a base 4. The electrode 2 is made of copper, for example, and a DC power source 5 is connected to the electrode 2. Then, by supplying power to the electrode 2 from the DC power source 5, an object to be adsorbed, for example, a semiconductor wafer W is electrostatically adsorbed to the upper insulating layer 3.
[0010]
The bipolar electrostatic chuck 1 ′ in FIG. 2 is provided with a pair of electrodes 2 a and 2 b between upper and lower insulating layers 3, to which a power source 5 is connected, and from the power source 5 to these electrodes. Charges having opposite polarities are supplied to each other, and an object to be adsorbed, for example, a semiconductor wafer W is electrostatically adsorbed on the insulating layer 3.
[0011]
Both the electrostatic chucks of FIGS. 1 and 2 are provided with projections 6 on the surface 3a of the insulating layer 3 on which the semiconductor wafer is adsorbed as shown in the figure, and the entire surface of the insulating layer 3 on which the projections 6 are formed. A resin sheet 7 is provided so as to cover the surface. Thus, by providing the protrusion 6 on the surface 3a of the insulating layer 3 and further providing the resin sheet 7 thereon, the contact area between the insulating layer 3 and the object to be adsorbed such as the semiconductor wafer W is reduced, and the adsorbed semiconductor. Contamination of the wafer W or the like can be reduced, and particles from the processed portion of the protrusion 6 can be prevented.
[0012]
The reason why the resin sheet 7 is made of resin is that the resin generates less particles than ceramics and the like, and can reduce the contamination of the adsorbent. The resin constituting the resin sheet 7 is not particularly limited, but is preferably a resin having plasma resistance such as a polyimide resin or a tetrafluoroethylene resin, and in particular, a polyimide resin having excellent plasma resistance. It is preferable to comprise resin.
[0013]
The thickness of the resin sheet 7 is not particularly limited, but is preferably 100 μm or less. When the thickness of the resin exceeds 100 μm, the electrostatic adsorption force is greatly reduced.
[0014]
The material and formation method of the protrusion 6 are not particularly limited. Ceramics or resin can be used as the material. In addition, as a method of forming the protrusions, the adsorption surface of a ceramic or resin-based electrostatic chuck may be processed and formed, or a resin tape or the like may be attached to the adsorption surface. When a resin tape or the like is affixed to the adsorption surface, there is no problem of particles generated from the material itself, but there is a problem that the affixed resin tape peels off when used repeatedly. This peeling of the resin tape can also be eliminated by covering the protrusion formed by applying the resin tape with the resin tape.
[0015]
Further, the ratio of the area of the protrusion 6 to the total area of the insulating layer 3 is preferably 5 to 30%. If it is less than 5%, the adsorptive power becomes weak, and there is a possibility that the object to be adsorbed such as a semiconductor wafer cannot be sufficiently held. If it exceeds 30%, the contact area between the object to be adsorbed and the insulating layer increases. As a result, adhesion of particles such as dust and dust increases.
[0016]
Furthermore, the height of the protrusion 6 is desirably 5 to 25 μm. If the thickness is less than 5 μm, the object to be adsorbed may come into contact with the insulating layer other than the protrusions 6 and particles such as dust and dust may increase. There is a risk that it cannot be held.
[0017]
A large number of protrusions 6 can be arranged on the surface 3a of the insulating layer 3, for example, as shown in FIG. In this case, the shape of the protrusion is not particularly limited, and various shapes such as a circle, an ellipse, and a rectangle can be adopted. Further, the projection 6 is not limited to such an arrangement, and various other arrangements can be adopted. For example, as shown in FIGS. 4, 5, 6, and 7, a ring shape, a mesh shape, a lattice shape, A radial arrangement or the like can be employed.
[0018]
The protrusion 6 may be formed over the entire surface. However, in the case of an electrostatic chuck having a structure in which the internal electrode shape is raised on the attracting surface, it is disposed only on the portion corresponding to the electrode, so that the adsorbed semiconductor wafer or the like The flatness of the adsorbent can be increased.
[0019]
In any case, it is desirable to form the protrusions 6 uniformly on the surface 3 a of the insulating layer 3. By thus forming the protrusions uniformly on the surface 3a, the flatness of the adsorbed object such as an adsorbed semiconductor wafer can be increased. Further, from the viewpoint of minimizing the contact area with the object to be adsorbed such as a semiconductor wafer and generating sufficient adsorbing force on the object to be adsorbed, the protrusion 6 is preferably disposed immediately above the electrode.
[0020]
Further, as shown in FIG. 8, a protrusion 6 ′ may be formed by applying a resin tape to the electrode 2, and a resin sheet 7 ′ functioning as an insulating layer may be formed thereon. Also in this case, the thickness of the resin sheet 7 ′ is preferably 100 μm or less for the above reason.
[0021]
Thus, by forming the protrusion and covering the resin sheet with the resin sheet, there is no possibility of generating particles from the peeled or processed portion, and there is little contamination of the adsorbed body such as the adsorbed semiconductor wafer W. An electric chuck can be obtained.
[0022]
【Example】
Examples of the present invention will be described below.
Example 1
The surface of the insulating layer of a φ300 mm bipolar electrostatic chuck having an alumina insulating layer was processed to form a protrusion of φ10 mm × 0.020 ^t mm. The ratio of the upper surface of the protrusion to the total area of the insulating layer was 20%. Further, the entire surface of the insulating layer on which the protrusions were formed was covered with a polyimide sheet having a thickness of 30 μm. A voltage of ± 500 V was applied to the electrode of the obtained electrostatic chuck to electrostatically attract the Si wafer, and the attracting force was measured. The adsorption force was measured by pulling the Si wafer adsorbed on the electrostatic chuck upward and measuring the force with a spring balance. Furthermore, the number of particles on the back surface of the wafer adsorbed on the electrostatic chuck was measured using a foreign matter inspection apparatus. As a result, the adsorption force was 60 g / cm ² and the number of particles was 150/300 mm wafer).
[0023]
(Example 2)
A plurality of φ3 mm × 0.020 ^t mm polyimide tapes were applied to a φ300 mm alumina substrate having electrodes formed on the surface to form protrusions. The ratio of the upper surface of the protrusion to the total area of the alumina substrate was 15%. Furthermore, a 70 μm-thick polyimide sheet was applied to the entire surface on which the protrusions were formed, and this was used as an insulating layer to produce an electrostatic chuck. The obtained chucking force of the electrostatic chuck was 48 g / cm ² and the number of particles was 130/300 mm wafer. Further, the wafer adsorption / desorption was repeated 500 times, but no separation of the protrusions formed on the alumina substrate was observed.
[0024]
(Comparative Example 1)
The surface of the insulating layer of a φ300 mm bipolar electrostatic chuck having an alumina insulating layer was processed to form a protrusion of φ20 mm × 0.020 ^t mm. The ratio of the upper surface of the protrusion to the total area of the insulating layer was 15%. The obtained chucking force of the electrostatic chuck was 70 g / cm ² and the number of particles was 800/300 mm wafer.
[0025]
(Comparative Example 2)
A 70 μm-thick polyimide sheet was attached to a 300 mm φ alumina substrate on which electrodes were formed, and an electrostatic chuck without protrusions was produced as an insulating layer. The obtained electrostatic chuck had an adsorption force of 80 g / cm ² and had a particle count of 600/300 mm wafer.
[0026]
【The invention's effect】
As described above, according to the present invention, by covering the electrode on which the protrusion is formed by applying the resin tape with the resin sheet, the generation of particles due to processing is suppressed, and the contact area with the adsorbent is increased. Particle suppression can be achieved by reducing the size, and an electrostatic chuck with less contamination of the adsorbed object can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a monopolar electrostatic chuck according to an embodiment of the present invention.
FIG. 2 is a sectional view showing a bipolar electrostatic chuck according to another embodiment of the present invention.
FIG. 3 is a schematic diagram showing an example of a protrusion arrangement in the present invention.
FIG. 4 is a schematic view showing another example of the protrusion arrangement in the present invention.
FIG. 5 is a schematic view showing still another example of the protrusion arrangement in the present invention.
FIG. 6 is a schematic view showing still another example of the protrusion arrangement in the present invention.
FIG. 7 is a schematic view showing still another example of the protrusion arrangement in the present invention.
FIG. 8 is a cross-sectional view showing a monopolar electrostatic chuck according to still another embodiment of the present invention.
[Explanation of symbols]
1, 1 '... Electrostatic chuck 2, 2a, 2b ... Electrode 3 ... Insulating layer 4 ... Base 5 ... Power source 6, 6' ... Projection 7, 7 '... Resin sheet

Claims (1)

An electrostatic chuck having an electrode and an insulating layer provided thereon, and electrostatically adsorbing an object to be adsorbed on the insulating layer by applying a voltage to the electrode, wherein a resin is applied to the surface of the electrode It has a protrusion formed by affixing a tape, and the electrode having the protrusion is covered with a resin sheet functioning as an insulating layer , and the resin sheet has an unevenness corresponding to the protrusion formed on the surface thereof. Electrostatic chuck.

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