TWI545688B - A method for manufacturing electrostatic chuck and electrostatic chuck - Google Patents

Description

Method for manufacturing electrostatic chuck and electrostatic chuck

The present invention relates to the field of semiconductor manufacturing technology, and in particular, to a method for manufacturing an electrostatic chuck and an electrostatic chuck.

As shown in Figure 1, the plasma processing apparatus includes a reaction chamber 10 that includes a susceptor 33 within which a lower electrode is included. Above the susceptor 33 includes an electrostatic chuck 34 on which the substrate 30 to be treated is disposed, and an edge ring 36 surrounds the electrostatic chuck 34. A radio frequency power source having a lower frequency (e.g., 2 Mhz to 400 Khz) is connected to the lower electrode in the susceptor 33 through a matching device. The top of the reaction chamber 10 also includes a gas distribution device 40, such as a gas shower head, or a nozzle for introducing a reaction gas into the reaction chamber 10. The gas distribution device 40 is connected to a gas source 20 by a flow dividing device or a switching valve. The gas showerhead can function as an upper electrode to cooperate with a lower electrode in the pedestal 33 to form a capacitor, and at least one high frequency RF power source is coupled to at least one end of the upper electrode to produce a capacitively coupled (CCP) plasma. An induction coil can also be mounted above the top of the reaction chamber 10. The induction coil is connected to a high frequency RF power source (greater than 13 Mhz), and the generated high frequency electromagnetic field passes through the insulating window at the top of the reaction chamber 10 into the space above the substrate 30 to make the reaction gas Ionization produces plasma. The substrate 30 is fixed to the susceptor 33 by an underlying electrostatic chuck 34, wherein the electrostatic chuck 34 includes at least one conductive electrode connected to a DC power source, a high voltage DC voltage (700V-3000V) on the conductive electrode. Charge can be induced on the substrate 30, and the charge on the substrate 30 and the electrodes of the electrostatic chuck 34 are electrostatically attracted to each other to secure the substrate to the electrostatic chuck 34. Quiet The specific structure of the electric chuck 34 is as shown in FIG. 2, and includes a first insulating material layer 340 at the bottom. The conductive electrode 341 is laid on the first insulating material layer 340, and a second insulating material layer 342 is covered on the conductive electrode 341. And a first insulating material layer 340. The first insulating material layer 340 and the second insulating material layer 342 are generally made of Al2O3 or AlN to insulate between the conductive electrode 341 and the substrate 30 or between the conductive electrode 341 and the lower base 33. The conductive electrode material is usually selected from tungsten. Or molybdenum to withstand high temperature processing environments.

The suction between the electrostatic chuck 34 and the substrate 30 satisfies the formula F = k V/d ² (1), where V is the applied DC voltage and d is the distance between the substrate 30 and the electrode 341, which is the second insulation. The thickness of the material layer 342. Therefore, the best way to increase the suction is to reduce d, but as the thickness of the insulating material layer 342 is reduced, impurities or bubbles in the second insulating material layer 342 may cause the second insulating material layer 342 to be broken down by high voltage. This can cause the electrostatic chuck 34 to break and seriously affect the processing effect of the substrate 30. Therefore, the prior art generally adopts a method of adjusting the voltage to obtain a voltage interval that does not cause the second insulating material layer 342 to break down or the suction force is insufficient. However, the range of the insulating material above the electrostatic chuck 34 in the prior art is usually from 400 μm to 600 μm due to the limitation of the material.

On the other hand, the temperature of the electrostatic chuck 34 changes frequently during the plasma processing, and the relative displacement occurs due to the difference in thermal expansion coefficient between the conductive electrode 341 and the second insulating material layer 342, and the second insulating material is caused after a long time of operation. A crack appears on the layer 342 even from the conductive electrode 341. In order to prevent the peeling off, as shown in FIG. 3, a rough upper surface of the unevenness is usually provided on the conductive electrode 341 to increase the contact surface between the second insulating material 342 and the conductive electrode 341. Rough contact surfaces increase the adhesion between the two materials, so the greater the roughness The combination of the two materials is stronger. However, the greater the roughness, the discharge of the tip end of the upper surface of the conductive electrode 341 is broken through the second insulating material layer 342. Therefore, in order to prevent the occurrence of breakdown, only the surface of the conductive electrode 341 of lower roughness can be selected, or a layer of insulating material of a higher thickness. This easily causes the hidden layer of the insulating material or the hidden danger of insufficient suction.

Therefore, the electrostatic chuck 34 of the plasma processor has the contradiction between improving the electrostatic attraction and the material to easily break down or falling off on the basis of the prior art, and requires a new technical solution to solve this contradiction, obtain higher electrostatic attraction and prevent the insulation material from being struck. Wear or fall off.

The problem solved by the present invention is that the thickness of the insulating material layer of the electrostatic chuck affects the suction force and the insulation effect, resulting in a limited selection range of the DC voltage. The present invention provides an electrostatic chuck comprising: a first insulating material layer, a conductive electrode, and a second insulating material layer, wherein the conductive electrode is located between the first insulating material layer and the second insulating material layer, and the upper surface of the second insulating material layer For fixing a substrate to be processed, characterized in that the second insulating material layer is fluorophlogopite.

Wherein the thickness of the second insulating material layer is less than 200 μm, and most preferably between 80 μm and 150 μm, to shorten the distance between the electrode and the substrate to increase the suction force.

Wherein the roughness of the contact surface between the conductive electrode and the second insulating material layer in the electrostatic chuck is greater than 0.3 μm, most preferably between 0.4 μm and 0.8 μm, to provide the adsorption capacity of the two material layers.

Wherein the upper surface of the second insulating material layer further comprises a layer of anti-plasma etching layer or anti-wearing material, the anti-plasma etching layer comprises cerium oxide or cerium fluoride, and the wear-resistant material layer is made of alumina material. And the thickness is smaller than the second insulating material layer. The material of the first insulating material layer is selected from one of alumina, aluminum nitride, and fluorophlogopite.

The present invention also provides a method for manufacturing an electrostatic chuck, comprising forming a first insulating material layer, the first insulating material layer being selected from aluminum oxide or aluminum nitride; forming a conductive electrode on the first insulating material layer, The conductive electrode material is selected from molybdenum or tungsten; a second insulating material layer is formed over the conductive electrode, and the second insulating material layer is fluorophlogopite, wherein the second insulating material layer is formed by a physical gas phase Deposition. Wherein the physical vapor deposition method comprises the steps of: providing a reaction furnace comprising a crucible containing fluorophlogopite; providing a heating device to heat the fluorophlogopite in the crucible to greater than 1375 ° C; The workpiece of the first insulating material layer formed with the conductive electrode is placed at a position opposite to the crucible to make the workpiece have a temperature of less than 300 ° C; the electrostatic chuck manufacturing method of the present invention may further comprise a step of forming a plasma etching resistant layer, A layer of ruthenium oxide or ruthenium fluoride is formed on the second insulating material layer.

10‧‧‧Reaction chamber

20‧‧‧ gas source

30‧‧‧Substrate

33‧‧‧Base

34‧‧‧Electrostatic chuck

340‧‧‧First insulating material layer

341‧‧‧Conductive electrode

342‧‧‧Second layer of insulating material

36‧‧‧Edge ring

40‧‧‧ gas distribution device

100‧‧‧Reaction furnace

110‧‧‧坩锅

120‧‧‧heat source

134‧‧‧Electrical chuck workpiece

1 is a schematic view showing the structure of a prior art plasma processing apparatus.

2 is a schematic view showing the structure of a prior art electrostatic chuck.

Figure 3 is a partial enlarged view of a portion A in Figure 2 .

Figure 4 is an electrostatic chuck insulating material coating apparatus of the present invention.

The invention solves the contradiction between the electrostatic chuck suction force and the material easily breaking or falling off in the plasma processing device, and proposes to replace the original alumina (Al ₂ O ₃ ) or aluminum nitride (AlN) with a new material. The breakdown characteristics of alumina or aluminum nitride materials commonly used in the prior art are 40 KV/mm, such as the thickness of the insulating layer, the surface roughness of the conductive electrode, and the magnitude of the applied DC voltage in the prior art electrostatic chuck without changing the material. The selection range is limited, and the design of the electrostatic chuck must be considered in the long-term operation of the plasma processing apparatus. These optimization options require a lot of experimentation and analysis cost.

The invention selects fluorophlogopite as the constituent material of the first insulating material layer 340 or the second insulating material layer 342 of the electrostatic chuck 34, and the breakdown characteristic of the fluorophlogopite is >200 kV/mm, compared with the existing material 40Kv. /mm has been enhanced by more than 5 times. Fluorphlogopite can be artificially synthesized, so the material properties are uniform and stable, and the inclusion of impurities is less likely to be broken down, and its properties can be maintained for long-term use. Since the second insulating material layer 342 of the present invention is selected from the fluorophlogopite, the thickness of the second insulating material layer 342 can be significantly reduced to less than 200 μm (for example, 80 μm to 150 μm), and the same DC voltage can be ensured. Will be broken down. At the same time, as expressed in the suction formula (1), the suction will increase rapidly as the thickness decreases to a square relationship, so reducing the thickness to the original 1/5 will cause the suction to become 25 times the original. Similar suction in the prior art requires only about 1/25 of the original voltage amplitude. The use of the fluorophlogopite of the present invention as a material for the electrostatic chuck insulating material layer can greatly reduce the thickness of the insulating material layer, and can also use a lower DC voltage to reduce power loss while ensuring that it is not broken down. On the other hand, due to the use of fluorophlogopite, the roughness selection on the conductive electrode can also be obtained in a larger range. For example, when the surface roughness is greater than 0.3 μm (such as 0.4 μm-0.8 μm), the insulating material can be ensured for a long time. It will not be broken down at the same time.

Since the application of the present invention requires precise control of its thickness, if the second insulating material layer 342 on the electrostatic chuck 34 is uneven, the substrate 30 may be uneven when it is fixed, which may cause the substrate 30 to be processed with high precision (for example, the CD is less than 60 nm). The etch is) when the graphics are distorted. At the same time, the uneven thickness causes the thermal resistance on the electrostatic chuck 34 to be different, the temperature on the substrate 30 is also uneven, and the uniformity of the processing of the substrate 30 is also affected. Therefore, when applied to the electrostatic chuck 34 in the field of semiconductor processing, the thickness of the fluorophlogopite coating must be uniform even in the case of a very thin film. Prior art fluorophlogopite often Seen as solid flakes or granules, the size of these solids or granules is far from being adapted to the needs of such high precision processing in the semiconductor field. The commonly used plasma spray can obtain a relatively uniform coating, but because of the large particle size, there are a large number of holes between different particles in the formed coating, so the electrical insulation performance is significantly reduced, and the uneven pore distribution will be Different breakdown characteristics are produced in different regions and therefore still fail to meet the needs of semiconductor processing devices. Similarly, the preparation of the fluorophlogopite of the present invention by the sinter method is also unsuitable for application to an electrostatic chuck because the pores between the particles are too much to control.

To this end, the inventors chose a new method of coating a fluorophlogopite insulating layer: physical vapor deposition (PVD). As shown in FIG. 4, the invention relates to an electrostatic chuck insulation material coating device, which comprises a reaction furnace 100, a crucible 110 located in the reaction furnace 100, and a coating material of fluorophlogopite mica placed in the crucible 110, as opposed to the crucible 110. Above is the electrostatic chuck workpiece 134 to be coated. The heat source 120 located on the side wall of the reaction furnace 100 emits an electron beam to the coating material in the crucible 110 to heat the fluorophlogopite solid material to a surface temperature greater than the melting point of 1375 ° C, followed by gasification. The upper electrostatic chuck workpiece 134 has a lower temperature (e.g., about 200 ° C) of less than 300 ° C, and the vaporized rising fluorophlogopite material is condensed and deposited on the surface of the electric chuck workpiece 134 to form a uniform and dense layer of insulating material. The electrostatic chuck workpiece 134 in the present invention may be a combination of a first insulating material layer 340 and a conductive electrode 341 as shown in FIG. 2, and a second insulating material layer 342 is grown on the conductive electrode 341 by vapor deposition in the object. A combination of the second insulating material layer 342 and the conductive electrode 341 may also be used to grow a first insulating material layer 340 by physical vapor deposition. When the fluorophlogopite insulating material is coated, physical vapor deposition of the fluorophlogopite material of the present invention can be achieved by providing a heater under the crucible 110 in addition to electron beam heating.

Since the electrostatic chuck 34 of the present invention is applied to a plasma processor, a portion of the electrostatic chuck 34 (such as a gap region between the edge ring 36 and the electrostatic chuck 34) is treated when the substrate 30 is processed by plasma. It will be exposed to the plasma, so the surface of the electrostatic chuck 34 needs to be protected. The electrostatic chuck 34 of the present invention may be coated with a layer of anti-plasma corrosion on the basis of a layer covered with a fluorophlogopite, typically such as yttrium oxide Y ₂ O ₃ or YF ₃ . The coating method of the plasma etching resistant layer may also be the above physical vapor deposition method. The friction between the substrate 30 and the electrostatic chuck 34 occurs when the substrate 30 is clamped, removed, or removed from the electrostatic chuck 34. Since the mechanical strength of the fluorophlogopite is insufficient, the operation may occur after a certain period of operation. abrasion. In order to improve the durability of the electrostatic chuck using fluorophlogopite as the insulating layer material, a thin layer of alumina (Al ₂ O ₃ ) may be deposited on the surface of the fluorophlogopite layer, the thickness of which can be resistant to friction, such as It can be less than 50 μm. Thus, the sum of the wear resistant material layer and the fluorophlogopite layer is still much smaller than the thickness of the second insulating material layer of the conventional electrostatic chuck of 400 μm to 600 μm. Since the demand for preventing breakdown is mainly achieved by the fluorophlogopite layer, the wear-resistant alumina thin layer has no such problem, and thus the alumina thin layer can be coated by various coating methods such as plasma spraying, sintering, PVD, and the like.

The invention utilizes fluorophlogopite, especially the fluorophlogopite which is deposited by physical vapor deposition as the insulating material layer of the electrostatic chuck, can significantly reduce the thickness of the insulating layer, reduce the DC voltage amplitude, and increase the between the insulating material layer and the conductive electrode. The adsorption force also ensures the uniformity of the insulating material layer.

Although the present invention has been disclosed above, the present invention is not limited thereto. Any changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be determined by the scope of the claims.

340‧‧‧First insulating material layer

341‧‧‧Conductive electrode

342‧‧‧Second layer of insulating material

Claims (10)

An electrostatic chuck includes: a first insulating material layer, a conductive electrode, and a second insulating material layer, wherein the conductive electrode is located between the first insulating material layer and the second insulating material layer, and the upper surface of the second insulating material layer is used for The substrate to be processed is fixed, characterized in that the second insulating material layer is fluorophlogopite. The electrostatic chuck according to claim 1, wherein the second insulating material layer has a thickness of less than 200 μm. The electrostatic chuck according to claim 2, wherein the second insulating material layer has a thickness of between 80 μm and 150 μm. The electrostatic chuck according to claim 1, wherein a roughness of a contact surface between the conductive electrode and the second insulating material layer is greater than 0.3 μm. The electrostatic chuck according to claim 4, wherein a roughness of a contact surface between the conductive electrode and the second insulating material layer is from 0.4 μm to 0.8 μm. The electrostatic chuck according to claim 1, wherein the upper surface of the second insulating material layer further comprises a layer of anti-plasma etching layer or a wear resistant material, and the anti-plasma etching layer comprises cerium oxide or lanthanum fluoride. The layer of wear resistant material is made of an alumina material and has a thickness smaller than that of the second layer of insulating material. The electrostatic chuck according to claim 1, wherein the material of the first insulating material layer is selected from one of alumina, aluminum nitride, and fluorophlogopite. A method for manufacturing an electrostatic chuck, comprising forming a first insulating material layer selected from aluminum oxide or aluminum nitride; forming a conductive electrode on the first insulating material layer, the conductive electrode material Selecting from molybdenum or tungsten; forming a second insulating material layer over the conductive electrode, the second insulating material layer being fluorophlogopite, wherein the second insulating material layer forming method is physical vapor deposition. The electrostatic chuck manufacturing method according to claim 8, wherein the physical vapor deposition method comprises the steps of: providing a reaction furnace comprising a crucible containing fluorophlogopite; Providing a heating device for heating the fluorophlogopite in the crucible to greater than 1375 ° C; placing the first insulating material layer forming the conductive electrode in a position opposite to the crucible, so that the workpiece has a temperature of less than 300 ° C . The electrostatic chuck manufacturing method according to claim 8, further comprising a plasma etching resistant layer forming step of forming a layer of tantalum oxide or hafnium fluoride on the second insulating material layer.