KR20030082473A - Electrostatic chucking stage and substrate processing apparatus - Google Patents

Abstract

The present application discloses a structure of an ESC stage in which an adsorption electrode is sandwiched by a relaxation layer and a cover layer. The relief layer and cover layer have a coefficient of thermal expansion between the dielectric plate and the adsorption electrode. The present application also discloses the optimum total thickness of the ESC stage, the optimal volume ratio of the composite to make the mitigating layer, and the optimal thermal expansion coefficient range of the composite. The present application further discloses a substrate processing apparatus that includes an electrostatic adsorption stage for securing a substrate during processing and for performing processing on the substrate when the substrate is maintained at a temperature higher than room temperature.

Description

Electrostatic adsorption stage and substrate processing apparatus {ELECTROSTATIC CHUCKING STAGE AND SUBSTRATE PROCESSING APPARATUS}

The present invention relates to a substrate processing apparatus comprising an electrostatic chucking stage (ESC) stage for holding a board-shaped object such as a substrate, and an ESC stage.

BACKGROUND ESC stages for chucking substrates by electrostatic forces are widely used in the field of substrate processing. In the manufacture of electronic devices such as LSI (Large-Scale Integrate circuits) and display devices such as liquid crystal displays (LCDs), for example, many steps are required to process the substrates on which the products are based. Are present. Of these steps, the ESC stage is used for process uniformity and process reproducibility. As an example, when etching the plasma, the substrate is etched using the action of ions and active species generated in the plasma. Here, the ESC stage is used to fix the substrate in an optimal position with respect to the plasma.

Generally, the ESC stage includes a chucking electrode to which a voltage for adsorption is applied, and a dielectric plate polarized by a voltage applied to the adsorption electrode. The fixed substrate is in contact with the dielectric plate and is adsorbed by static electricity induced on the surface of the dielectric plate.

The ESC stage is required to stabilize the substrate and to adsorb it. If the substrate is moved or repositioned on the ESC stage while the machining is being performed, it may cause a problem that the machining uniformity and the process reproducibility are degraded. During substrate processing, thermal transformation and thermal expansion of the ESC stage are dangerous in terms of processing homogeneity and processing reproducibility. During processing, the temperature of the substrate is often higher than room temperature. This is mainly due to the processing conditions, but in other cases due to the environment of the process chamber in which the processing is performed. In any case, when the temperature of the substrate rises, the temperature of the ESC stage also rises. When the thermal deformation and thermal expansion of the ESC stage occur due to the temperature rise, the fixed substrate may be transformed or displaced.

The invention of the present application is to solve the problems described and has the advantage of providing a high-performance ESC stage capable of preventing deformation and movement of the fixed substrate. Specifically, the present invention provides a structure of an ESC stage in which an adsorption electrode is sandwiched by a moderation layer and a covering layer. The relief layer and cover layer have a coefficient of thermal expansion between the dielectric plate and the adsorption electrode. The present invention also discloses the optimum total thickness of the ESC stage, the optimal volume ratio of the composite making the relief layer, and the range of the optimum coefficient of thermal expansion of the composite. The present invention further includes an ESC stage for fixing a substrate during processing, and further provides a substrate processing apparatus for performing processing on the substrate when the substrate is maintained at a temperature higher than room temperature.

1 is a schematic front cross-sectional view of an ESC stage that is an embodiment of the invention,

2 is a view schematically illustrating the advantages of the ESC stage shown in FIG.

3 is a schematic front cross-sectional view of a substrate processing apparatus that is an embodiment of the present invention;

4, 5, 6 and 7 are diagrams schematically showing the results of experiments to confirm the effect obtained from the structure of the embodiment,

8 is a schematic front cross-sectional view of another embodiment of the ESC stage.

Preferred embodiments of the invention will be described below. First, the implementation of the ESC stage will be described. 1 is a schematic front cross-sectional view of an embodiment of an ESC stage. The ESC stage includes a main body 41, a dielectric plate 42 on which the adsorbed object 9 is placed, and an adsorption electrode 43 to which a voltage for adsorption is applied.

The ESC stage resembles a table as a whole and holds the plate-forming object 9 on top. The main body 41 is made of metal such as aluminum or stainless steel. Body 41 is low column shaped. The adsorption electrode 43 is fixed on the body 41. As shown in FIG. 1, the adsorption electrode 43 has a flange-shaped portion 431 at the bottom end. This portion 431 is hereinafter referred to as an 'electrode flange'. The adsorption electrode 43 is fixed on the body 41 by screwing in the electrode flange 431. The adsorption electrode 43 is electrically shorted with the main body 41.

A protective ring 49 is provided surrounding the screwed electrode flange 431. The protective ring 49 is made of an insulator such as silicon oxide. The protection ring 49 protects these by covering the side surface of the adsorption electrode 43 and the electrode flange 431. As shown in FIG.

The dielectric plate 42 is located above the adsorption electrode 43. As shown in FIG. 1, the adsorption electrode 43 is formed of an upwardly convex portion and a flange-like portion surrounding the convex portion. The dielectric plate 42 is almost the same in diameter as the adsorption electrode 43.

Adsorption power source 40 is connected to the described ESC stage. The kind of adsorption power source 40 depends on that of electrostatic chucking. The ESC stage of this embodiment is a mono-electrode type. As the suction power source 40, a positive DC power source is selected. The suction power source 40 is connected to the main body 41 and applies a positive DC voltage to the suction electrode 43 through the main body 41. The voltage applied to the adsorption electrode 43 causes dielectric polarization that can adsorb the object 9. In this embodiment, since a positive DC voltage is applied, a positive charge is induced above the surface of the dielectric plate 42, resulting in the electrostatic attraction of the object 9.

Two electrostatic chucking mechanisms are known. One is by Coulomb force and the other is by Johnson-Rahbeck force. Johnson-Labeck force is the adsorption force generated by the concentration of current in the micro-zone. The surfaces of the dielectric plate 42 and the object 9 are microscopically uneven. The fine ridges on both surfaces abut each other. When electrostatic charge is induced by the adsorption power source 40, the flowing currents collect at the ridges in contact with each other, resulting in the Johnson-Labeck force. Johnson-Labeck force is dominant in the same ESC stage as this embodiment. However, the present invention is not limited only to the preponderance of Johnson-Labelhim.

One of the biggest features of the ESC stage in this embodiment is that the structure is effectively prevented from thermal movement and thermal deformation of the object 9. This point will be explained below. The ESC stage of this embodiment is supposedly used in hot temperature environment. This can occur, for example, when the object 9 is tested under a hot temperature environment, in addition to the case where the object 9 is a substrate to be machined. Even when used in a high temperature environment, heat transfer and thermal deformation are prevented in the ESC stage of the present embodiment.

Specifically, as shown in FIG. 1, an alleviation layer 44 is provided between the dielectric plate 42 and the adsorption electrode 43. The alleviation layer 44 can alleviate the thermal expansion coefficient difference between the dielectric plate 42 and the adsorption electrode 43, thereby preventing thermal movement and thermal deformation of the object 9. More specifically, the relaxation layer 44 has a median thermal expansion coefficient value between the dielectric plate 420 and the adsorption electrode 43. The "intermediate thermal expansion coefficient value" means that the thermal expansion coefficient of the adsorption electrode 43 is a dielectric plate. If higher than 42, it is lower than the adsorption electrode 43 and higher than the dielectric plate 42. And, if the thermal expansion coefficient of the dielectric plate 42 is higher than the adsorption electrode 43, it is lower than the dielectric plate 42 and the adsorption electrode ( 43) higher than that.

In this embodiment, in particular, the adsorption electrode 43 is made of aluminum and the dielectric plate 42 is made of alumina (Al ₂ O ₃ ). The mitigating layer 44 is made of a composite of ceramic and metal. Examples of the composite having a coefficient of thermal expansion between aluminum and magnesia include a composite of silicon carbide and aluminum, hereinafter referred to as "SiC-Al composite". The coefficient of thermal expansion of aluminum is 0.237 × 10 ⁻⁴ / K and magnesia is 14 × 10 ⁻⁶ / K. In this case, SiC-Al composites having a coefficient of thermal expansion of about 10 x 10 ^-6 / K are preferably selected as the material of the relaxation layer 44. This kind of SiC-Al composite is prepared by poring molten aluminum into a porous SiC bulk and filling it. Porous SiC bulk is prepared by high temperature high pressure sinter-molding of SiC powder. After cooling the forged aluminum, a relaxed layer 44 molded as in FIG. 1 is obtained by mechanical operations such as cutting. The volume opening ratio of the porous SiC-Al bulk, which can control the volume of the filled aluminium, is controlled by selecting the appropriate temperature and the appropriate pressure during sintering-casting. By comparing the density of the porous bulk with the non-porous bulk of the same size, the volume opening ratio is obtained. The coefficient of thermal expansion of the SiC-Al composites produced by the described method depends on the composition ratio of aluminum to SiC. The thermal expansion coefficient of 10 × 10 ⁻⁶ / K described is obtained by adjusting the composition ratio.

If any, the coefficient of thermal expansion of the relaxation layer 44 is preferably closer to the dielectric plate 42 than the adsorption electrode 43. Considering that the thermal expansion coefficient of aluminum is 0.237 × 10 ⁻⁴ / K and the aluminum is 7.3 × 10 ⁻⁶ / K, the thermal expansion coefficient of the relaxation layer 44 is preferably 9.5 × 10 ⁻⁶ / K to 10.5 × 10 ^-6 / K range. This is possible by making the volume ratio of silicon carbide 50 to 60 percent with respect to the total volume. "Coefficient of thermal expansion closer to the dielectric plate" means that it is closer to the value of the dielectric plate 42 than merely the median between the dielectric plate 42 and the adsorption electrode 43.

Additionally, in the ESC stage of this embodiment, the capping layer 45 is provided over the adsorption electrode 43 on the opposite side of the mitigating layer 44. That is, the ESC stage has a structure in which the adsorption electrode 43 is sandwiched by the relaxation layer 44 and the cover layer 45. The cover layer 45 is inserted between the adsorption electrode 43 and the main body 41. This cover layer 45 is also made of a material having a coefficient of thermal expansion between the dielectric plate 42 and the adsorption electrode 43. This is possible by choosing the same material as that of the mitigating layer 44. However, other materials may be selected for the cover layer 45.

The structure in which the adsorption electrode 43 is sandwiched by the buffer layer 44 and the cover layer 45 having an in-between thermal expansion coefficient between them can prevent movement and deformation of the adsorbed object 9. Can be. This will be explained in detail below with reference to FIG. 2. FIG. 2 schematically illustrates the advantages of the ESC stage shown in FIG. 1.

In general, the coefficient of thermal expansion between the adsorption electrode material, for example a metal, and the material of the dielectric plate 42, for example the dielectric, is largely different. In the prior art structure in which the dielectric plate 42 is fixed on the adsorption electrode 43, when the ESC stage is heated to a hot temperature, large deformation of the adsorption electrode is easy due to the difference in thermal expansion coefficient with the dielectric plate 42. Can occur. As a result, the dielectric plate 42 can also be convex, as shown in FIG. 2 (1) or concave, as shown in FIG. 2 (2). Such deformation of the dielectric plate 42 may result in the movement or deformation of the object 9 to be adsorbed.

In the prior art structure in which a relaxation layer 44 having a thermal expansion coefficient therebetween is inserted between the dielectric plate 42 and the adsorption electrode 43, the difference in the thermal expansion coefficient is alleviated, and as a result, the deformation of the dielectric plate 42 is suppressed. do. Investigations by the inventors have shown that, as shown in FIG. 4, when a layer similar to the relaxed layer 44 is additionally provided on the opposite side, deformation of the dielectric plate 42 is further suppressed. Although the reason is not fully understood, it is conceivable that the thermal expansion at both sides of the adsorption electrode 43 will be in a balanced state when sandwiched by the layers having the coefficient of thermal expansion therebetween. Moreover, it is conceivable that the inner-stress of the adsorption electrode 43 will be balanced by both layers with similar coefficients of thermal expansion.

In relation to the thermal stress, it is also conceivable that the thermal stress in the relaxation layer 44 and the cover layer 45 will act to suppress the deformation of the adsorption electrode 43. For example, when the adsorption electrode 43 is convexly deformed upward, the internal thermal stresses of the relief layer 44 and the cover layer 45 may act to convex it downward, for example, so that it deforms in the opposite direction. have. In addition, when a compressive stress is generated in the adsorption electrode 43, it may occur that a tension stress is generated in the relaxation layer 44 and the cover layer 45. Conversely, when tension is created in the adsorption electrode 43, compressive stress can be generated in the relaxation layer 44 and the cover layer 45. In general, it can be said that the alleviation layer 44 and the encapsulation layer 45 may have a stress that is opposite to the stress in the adsorption electrode 43. "Opposite" here does not always mean that the stress is directed in the completely opposite direction. Expressed as a vector, the stress vectors in the relaxation layer 44 and the cover layer 45 make an angle of 90 degrees or more with respect to the stress vectors in the adsorption electrode 43.

In any case, the condition of the lid layer 45 further suppresses the deformation of the adsorption electrode 43 and the deformation of the dielectric plate 42. As a result, movement and deformation of the object 9 can be suppressed together. The fact that the cover layer 45 has a similar thermal-expansion coefficient does not mean a perfect correspondence of the coefficient of thermal expansion, but in that the cover layer 45 has a coefficient of thermal expansion therebetween. It just means that it is similar. The same ceramic-metal composite as the relaxed layer 44, for example SiC-Al composite, can be used as the material of the capping layer 45. The composite on the cover layer 45 is conductive and has a sufficient metal content. This is not to insulate the adsorption electrode 43 from the main body 41.

The structure for fixing the dielectric plate 42 is also important in that it suppresses the deformation of the dielectric plate 42. When the dielectric plate 42 is locally fixed by, for example, screwing, the thermal deformation of the dielectric plate 42 is because the state is tight at the fixing point and the thermal conductivity is locally strengthened at the fixing point. This can get worse. In the present embodiment, the dielectric plate 42 is connected to the adsorption electrode 43 by a brazing material whose main component is either aluminum or indium. "Principal component" here implies pure aluminum or pure indium, in addition to including some additives. For example, the connection is made by brazing of the entire surface. Specifically, a thin film made of indium is inserted between the dielectric plate 42 and the alleviation layer 44. The dielectric plates 42 are fixed to the relief layer 44 by heating them to about 120 ° C. to 130 ° C. and then cooling them. In terms of thermal contact and strengthening of mechanical strength, during brazing, it is preferable to mechanically apply a pressure in the range of 1 MPa to 2 MPa while heating to a temperature in the range of 570 ° C to 590 ° C. The brazing connection more effectively suppresses the deformation of the dielectric plate 42. It is also practical to braze the relaxation layer 44 and the adsorption electrode 43, and to braze the adsorption electrode 43 and the cover layer 45 in the same manner.

The total thickness of the dielectric plate 42, the adsorption electrode 43, the relief layer 44, and the cover layer 45, hereinafter simply referred to as "total thickness", is preferably in the range of 28 mm to 32 mm. The reason for this is as follows. If the total thickness is less than 28 mm, thermal deformation, such as described as thin, can easily occur. In addition, when a cavity for cooling is provided in the ESC stage, which will be described later, the total thickness of less than 28 mm may cause the problem of insufficient cooling due to lack of space and contact area for the coolant for cooling. Can cause. On the contrary, if the total thickness exceeds 32mm, it may expand insignificantly and cause problems in the space and security. Furthermore, it causes a problem that longer screws are required to fix the adsorption electrode 43, and a problem that larger size protection rings 49 are required. As a result, the total thickness is preferably within the range of 28 mm to 32 mm.

In the following, an embodiment of the substrate processing apparatus of the present invention will be described. The device of the present invention is to process it while keeping the substrate at a temperature above room temperature. In the following description, a plasma etching apparatus is selected as an embodiment of the substrate processing apparatus. Also, in the following description, "object" is replaced by "substrate" which is a subordinate concept thereof.

3 is a schematic front cross-sectional view of a substrate processing apparatus as an embodiment of the present invention. The apparatus shown in FIG. 3 is a process chamber in which plasma etching is performed on a substrate 9, a process-gas inlet line 2 for introducing a process gas into the processing chamber 1, which is introduced. A plasma generator 3 for generating energy in the processing chamber 1 by applying energy to the processing gas, and electrostatic adsorption at a position where the substrate 9 can be etched by the action of the plasma; ESC stage 4 for fixing). The ESC stage 4 is almost identical to that in the described embodiment.

The processing chamber is a vacuum vessel through which no air flows, and is pumped by the pumping line 11. The processing chamber 1 is made of metal, such as stainless steel, and is electrically grounded. The pumping line 11 includes a vacuum pump 11, such as a drying pump and a pumping speed regulator 112, so that the pressure in the resulting processing chamber 1 can be maintained at 10 ^-3 pa to 10 pa.

The process-gas inlet line 2 can introduce a process gas for plasma etching at the required flow rate. In this embodiment, a reaction gas, such as trifluoromethane (CHF ₃ ), is introduced into the processing chamber 1 as the processing gas. The process-gas inlet line 2 comprises a gas bomb filled with process gas and a supply pipe connecting the gas chest and the processing chamber 1 to each other.

The plasma generator 3 generates a plasma by applying radio frequency (RF) energy to the introduced process gas. The plasma generator 3 comprises an opposite electrode 30 facing the ESC stage 4, and an RF power source 31 for applying an RF voltage to the opposite electrode 30. Hereinafter, the RF power source 31 is referred to as a 'plasma generating source'. The frequency of the plasma generating source 31 ranges from 100 kHz to several tens of MHz. The plasma generation source 31 is connected to the counter electrode 30 in which a matching circuit (not shown) is inserted. The output of the plasma generation source 31 may range from 300W to 2500W. By inserting the insulator 32, the counter electrode 30 is mounted in the processing chamber 1 to block the air.

When the plasma generation source 31 applies the RF voltage to the counter electrode 30, the RF charge is ignited using the processing gas introduced by the RF field provided in the processing chamber 1. Through the charge, the processing gas moves over the plasma. When the processing gas is fluoride, fluorine or fluoride ions and activated species are produced in abundance in the plasma. These ions and species reach the substrate 9 and etch the surface of the resulting substrate 9.

By inserting the capacitor, another RF power source 6 is connected with the ESC stage 4. This RF power source 6 is for injecting ions onto the substrate 9 efficiently. This RF power source 6 is hereinafter referred to as an "ion-incidence source." When the ion incident source 6 is operated in a state where a plasma is generated, a self-biasing voltage is provided to the substrate 9. The self-bias voltage is a negative DC voltage generated through the interaction of plasma and RF waves. The self-bias voltage effectively injects ions onto the substrate 9, enhancing the resulting etch rate.

In this embodiment, a correction ring 46 is provided to the ESC stage 4. In parallel with the substrate 9, a calibration ring 46 is installed over the flange portion of the dielectric plate 42. The calibration ring 46 is made of the same or similar material as the substrate 9, for example silicon mono-crystal. The calibration ring 46 is intended to prevent non-uniformity or non-uniformity of processing around the substrate 9. Due to the heat dissipation from the edge of the substrate 9, the temperature at the substrate 9 tends to be lower at the periphery compared to the center. To solve this problem, a calibration ring 46 made of the same or similar material as the substrate 9 is provided to surround the substrate 9 to compensate for heat dissipation. With etching, the plasma is supported by the ions and electrons emitted from the substrate 9. The plasma density tends to be lower in the space facing the periphery of the substrate 9 because smaller numbers of ions and electrons are emitted compared to the center. When a calibration ring 46 made of the same or similar material as the substrate 9 is provided to surround it, the amount of ions and electrons supplied to the space facing the periphery of the substrate 9 is increased, resulting in a more uniform plasma. And make it more uniform.

As described, the ESC stage 4 comprises a protection ring 49. The protective ring 49 protects the side of the adsorption electrode 43 and the electrode flange from damage by plasma or charge. If the substrate 9 is made of silicon, the protective ring 49 made of silicon-oxide reduces the possibility of contamination of the substrate 9 even after being etched.

The insulator 47 is inserted, and the ESC stage 4 is installed in the processing chamber 1. The insulator 47 is made of a material such as alumina and not only protects the body 41 from the plasma, but also insulates the body 41 from the processing chamber 1. In order to prevent the leakage of vacuum from the processing chamber 1, a vacuum sealant such as an O-ring is provided between the ESC stage 4 and the insulator 47 and between the processing chamber 1 and the insulator 47.

The apparatus of the present embodiment includes a temperature controller 5 for adjusting the temperature of the substrate 9 during processing. As explained, hereafter referred to as "optimal temperature", the temperature of the substrate 9 maintained during processing is mainly higher than room temperature. However, during plasma etching, the temperature of the substrate 9 easily receives heat from the plasma and easily exceeds the optimum temperature. In order to solve this problem, the temperature controller 5 cools the substrate 9 and adjusts its temperature to an optimum value during etching.

As shown in FIG. 3, the adsorption electrode 43 has a cavity by itself. The thermostat 5 circulates the coolant through the cavity to cool the adsorption electrode 43 and consequently cools the substrate 9. The temperature controller 51 includes a coolant inlet tube 51 for injecting coolant into the cavity, a coolant drain pipe 52 for discharging the coolant out of the cavity, and a circulator 53 for circulating the coolant adjusted to the required low temperature. do. As the coolant, for example, Fluorinate (trade name of 3M Corporation) is used. The temperature controller 51 cools the substrate 9 in a temperature range of 80 ° C to 90 ° C by circulating a coolant at 30 ° C to 40 ° C.

The substrate processing apparatus includes a heat-transfer gas inlet line (not shown) for introducing gas between the adsorbed substrate 9 and the dielectric plate 42. The heat-transfer gas inlet is to enhance the heat transfer efficiency between the adsorbed substrate 9 and the dielectric plate 42. The back surface of the substrate 9 and the top surface of the dielectric plate 42 are not completely flat, but are finely rough. In spaces formed with fine roughness on the surface, the heat transfer efficiency is poor because of the vacuum pressure. The heat-transfer gas inlet line introduces a high thermal conductivity gas, such as helium, into the space, improving the resulting heat transfer efficiency.

The ESC stage 4 includes a lift pin 48 therein for inserting and withdrawing the substrate 9. The lift pins 48 are lifted by an elevation mechanism (not shown). Although only one lift pin 48 is shown in FIG. 3, in practice three lift pins 48 are provided.

The operation of the substrate processing apparatus of this embodiment will be described next. After the movement mechanism (not shown) moves the substrate 9 into the processing chamber 1, the substrate 9 is placed on the ESC stage 4 by the operation of the lift pin 48. By operation of the adsorption power source 40, the substrate 9 is adsorbed onto the ESC stage 4. Furthermore, the processing chamber 1 is pumped to the required vacuum pressure. In this state, the processing gas inlet line 2 is operated to introduce the processing gas at the required flow rate. Next, the plasma generation source 31 is operated to generate plasma as a result. Etching is performed using plasma as described. The temperature controller 5 cools the substrate 9 to an optimum temperature. During etching, the ion-incident source 6 is activated to enhance the etching efficiency. After etching is performed for the required period, the operation of the process-gas inlet tube 2, the plasma generating source 31, and the ion incidence source 6 is stopped. Next, the operation of the adsorption power source 40 is stopped, and the adsorption to the substrate 9 is released. After the processing chamber 1 is pumped again, the substrate 9 is moved out of the processing chamber 1 by the moving mechanism.

In the substrate processing apparatus, even if the adsorption electrode 43 is heated higher than room temperature, the deformation is suppressed by the relaxation layer 44 and the cover layer as described. As a result, the deformation of the dielectric plate and the movement or deformation of the substrate 9 caused thereby are suppressed together. Thus, processing uniformity and processing unity are enhanced.

The advantages of the mitigating layer 44 and the covering layer 45 to suppress deformation are particularly evident in the structure in which the calibration ring 46 is provided. This will be explained in detail in the following. The calibration ring 46 essentially has the same arrangement as extending the substrate 9 outward. The material of the calibration ring 46 is the same or similar to the substrate 9. A calibration ring 46 is provided over the flange portion of the dielectric plate 42 and adsorbs the dielectric plate 42 as well as the substrate 9. Since the flange portion is thin and peripheral, the deformability and volume of the dielectric plate 42 will be relatively larger in the flange portion. If movement or deformation of the calibration ring 46 occurs due to the deformation of the dielectric plate 42, the action to compensate for heat dissipation from the edge of the substrate 9 will be uneven. Moreover, the thermal bonding of the calibration ring 46 to the dielectric plate 42 becomes poor due to movement or deformation, resulting in a higher temperature of the calibration ring than the substrate 9. Especially serious is the random occurrence of thermal bond degradation of the calibration ring to the dielectric plate. When the thermal bond degradation of the calibration ring 46 is random, the action of the calibration ring 46 to compensate the heating of the substrate 9 will also be random. This in particular leads to a decrease in the reproducibility of the temperature conditions for the substrate 9 during processing.

In this embodiment, however, since the deformation and movement of the dielectric plate 42 is limited by the suppression of deformation of the adsorption electrode 43, the calibration ring 46 is difficult to deform or move. As a result, this embodiment is free from problems such as non-uniformity and non-reproducibility of substrate temperature.

Experimental results for confirming the effect obtained from the structure of the embodiment will be described below. 4 to 7 schematically show the results of this experiment. In this experiment, the deformation and movement of the dielectric plate 42 surface relative to the ESC stage were measured under different temperature or conditions of different temperature strengths. Deformation and movement were measured with a distance meter. In order to measure the height of each point, the distance from each point on the surface of the dielectric plate 42 relative to the reference height was measured with a range finder, with the ESC stage as the reference height.

4 and 5 show the heights of the points on the surface of the convex portion of the dielectric plate 42. 4 shows the height in the case of the prior art ESC stage without the relief layer 44 and the cover layer 45. 5 shows the height in the case of an ESC stage of the described embodiment with a relief layer 44 and a cover layer 45. 6 and 7 show the heights of the points on the surface of the flange portion of dielectric plate 42. 6 shows the height in the case of a prior art ESC stage without the mitigating layer 44 and the capping layer 45. FIG. 7 shows the height in the case of the ESC stage of the described embodiment with a relief layer 44 and a cover layer 45. The positions of the respective points on the flange portions indicated by ①, ②, ③, ④ in FIGS. 6 and 7 represent the same ①, ②, ③, ④ respectively in FIG.

Experiments were performed by varying the temperature of the ESC stage. The temperature of the ESC stage is hereinafter referred to as "stage temperature". 4 to 7, "A" shows the data measured at stage temperature of 20 degreeC after leaving ESC stage overnight at 20 degreeC. "B" shows the data measured, maintaining stage temperature at 5 degreeC. "C" represents data measured at stage temperature 20 ° C after cooling the ESC stage to 5 ° C. "D" shows the data measured while maintaining stage temperature at 50 degreeC. "E" represents data measured while forcibly cooling the ESC stage to 20 ° C after making the stage temperature 50 ° C. Although the ESC stage 4 has openings for internal elements such as the lift pin 48, the data in these openings have been omitted in FIGS.

Typically, in Figures 4-7, the higher the stage temperature, the higher the height of the dielectric plate 42. This is the result obtained by the thermal expansion of the entire ESC stage 4, and is somewhat natural. The problem is that the movement and deformation of the dielectric plate 42 depends on the stage temperature or the strength of the stage temperature.

In particular, each line shown in FIG. 5 is drawn from points on the surface of the dielectric plate 42, hereinafter referred to as "surface level distance". As shown in FIG. 5, the surface height distribution rises and falls while maintaining the same shape, depending on the stage temperature or the strength of the stage temperature. In summary, they are moved in parallel. This probably demonstrates that the dielectric plate 42 thermally expands uniformly without deformation. In FIG. 4, on the contrary, the surface height distribution rises and falls in shape depending on stage temperature or stage temperature history. In summary, they do not move in parallel. This probably proves that deformation of the dielectric plate 42 has occurred. Of particular concern is that the surface height distribution changes shape with the stage temperature history. As shown in FIG. 4, even if the measurement is performed at the same stage temperature 20 ° C., the surface height distribution draws another curve when it is left at 20 ° C. overnight and degraded by forced cooling from 50 ° C. FIG.

The same analysis was applied to the results of the flange portion. As shown in FIG. 6, in the case where the relief layer 44 and the cover layer 45 are provided, the surface height distribution rises and falls while maintaining the same shape. On the contrary, as shown in Fig. 7, when the mitigating layer 44 and the capping layer 45 are not provided, the surface height distribution changes shape and up and down. Also at each stage temperature, the surface height distribution is shown in FIG. I've drawn another curve at 7.

The fact that the surface height distribution depends on the temperature strength causes serious problems for the reproducibility of substrate processing. Substrate processing equipment manufactured at the manufacturing plant is installed in the production line and used after work such as delivery inspection. However, until the actual substrate processing starts for the first time, none of the devices has the same temperature history. Even devices that have performed nearly the same machining always show different temperature strengths through operations such as feed inspection at the manufacturing plant and test runs on the user's work line. Furthermore, considering each unit machining on the substrate, the temperature strength exhibited by the ESC stage until the machining on the substrate is performed is different from the other temperature strength exhibited by the ESC stage until the machining on another substrate is performed. can be different. For example, the temperature strength exhibited by the ESC stage while unit processing is continuously performed may be different from the other temperature strength of the ESC stage first used for processing on the first substrate. This situation occurs, for example, when the device is started after stopping for maintenance.

The fact that the surface height distribution depends on the load capacity of the stage temperature means that even if the ESC stage is adjusted to a constant temperature by the temperature controller 5, the substrate 9 will be deformed or moved according to the load capacity. This can be a serious problem in terms of process reproducibility. When the mitigating layer 44 and the encapsulation layer 45 are provided, however, the surface height distribution with no deformation and no movement of the substrate 9 does not depend on the stage temperature history. As a result, processing with high reproducibility is possible by keeping the ESC stage 4 at the required temperature.

Another implementation of the ESC stage of the present invention will be described next. 8 is a schematic front sectional view of an ESC stage as another embodiment of the present invention. In this embodiment, the structure of the adsorption electrode 43 is different from the described embodiment. Adsorption electrode 43 includes a pair of cooling fin-plates 431, 432. Each pin-plate 431, 432 is each tightened with a pin, facing each other.

Specifically, the lower cooling fin-plate 431 is provided with a number of fins projecting upwards. In contrast, the upper cooling fin-plate 432 is provided with many fins projecting downward. Each pin for each pin-plate 431, 432 is circular-arc or circular, coaxial to the ESC stage 4. Each pin on the lower cooling fin-plate 431 is inserted between each pair of fins on the upper cooling fin-plate 432. Each pin above the upper cooling fin-plate 432 is inserted between each pair of fins above the lower cooling fin-plate 431.

As shown in FIG. 8, a cavity 430 having a complicated structure is formed by the cooling fin-plates 431, 432. The ESC stage includes a temperature controller and circulates a coolant through this cavity 430 to cool the adsorption electrode 43, as a result of which the substrate 9 is indirectly cooled. The temperature controller includes a coolant injection tube 51 for injecting coolant into the cavity 430, a coolant drain pipe 52 for discharging the coolant out of the cavity, and a circulator for circulating the coolant adjusted to the required low temperature (see FIG. 8). Not shown).

This embodiment has the advantage of higher cooling efficiency because the coolant is in contact with the adsorption electrode 43 in a large area. As a result, even when the input power to the plasma is increased to enhance the plasma density, the substrate 9 is easily maintained at the required low temperature, contributing to a higher processing speed.

More detailed embodiments belonging to the embodiment will be described below.

Adsorption electrode 43 material: aluminum

Dielectric Plate 42 Material: Alumina

Fixing of Dielectric Plate 42: Brazing with In

Material of Mitigating Layer 44: SiC-Al Composite

Thickness of mitigating layer 44: 12 mm

Material of Encapsulation Layer 44: SiC-Al Composite

Cover layer 44 thickness: 12 mm

Adsorption Voltage: 550V

The size of the substrate 9 adsorbed by the embodiment is 300 mm in diameter, for example.

The material of the alleviation layer 44 and the encapsulation layer 45 is not limited to the SiC-Al composite described. It can be another composite of ceramic and metal. For example, silicon carbide and copper composite, silicon carbide and nickel composite, silkycone carbide and Fe-Ni-Co alloy composite, silicon carbide and Fe-Ni alloy composite, silicon nitride (Si ₃ N ₄ ) And a composite of nickel or silicon nitride and a Fe-Ni alloy. Moreover, the materials of the relief layer 44 and the cover layer 45 are not limited to the composite of ceramic and metal. All that is needed is to have a coefficient of thermal expansion between the adsorption electrode 43 and the dielectric plate 42.

There are numerous types of electrostatic adsorption, such as the bi-electrode type and the multi-electrode type, as well as the described mono-electrode type. The double-electrode type includes a pair of adsorption electrodes, to which voltages of opposite polarities are applied. The multi-electrode type includes multiple pairs of adsorptive electrodes, and applies voltages of opposite polarity to each electrode of each pair. In these types, the adsorption electrode can be embedded into the dielectric plate 42. In the case of a single electrode type, a negative DC voltage can be applied for adsorption. The invention is also possible with these kinds. While the described ESC stage adsorbs the object or substrate 9 at the top surface, it is also possible, on the contrary, to adsorb the object and substrate 9 at the bottom surface, for example. Moreover, the ESC stage may be vertical to adsorb the object or substrate 9 from the side.

Although the plasma etching apparatus has been selected as an example for the substrate processing apparatus in the description, the present invention is also possible for other apparatuses such as plasma chemical vapor deposition (CVD) apparatuses and sputtering apparatuses. The thermostat 5 may heat the substrate 9 and maintain it at the required temperature. In addition to substrate processing, there are many other applications for ESC stages, such as testing objects, for example environmental test equipment.

Claims (7)

A dielectric plate onto which the object is adsorbed; An adsorption electrode applied with a voltage for dielectrically polarizing the dielectric plate; A relaxation layer provided between the dielectric plate and the adsorption electrode, the relaxation layer having a coefficient of thermal expansion between the dielectric plate and the adsorption electrode; And Provided over the adsorption plate on the opposite side of the dielectric plate, the cover layer having a coefficient of thermal expansion between the dielectric plate and the adsorption electrode, An electrostatic adsorption stage for electrostatically adsorbing an object, further comprising a structure in which the adsorption electrode is sandwiched by the alleviation layer and the overlying layer: At this time, The dielectric plate is made of alumina, The adsorption electrode is made of aluminum, The alleviation layer is made of a composite of silicon carbide and aluminum, and The dielectric plate and the relief layer are brazed by a brazing material whose main component is indium. The method of claim 1, An electrostatic adsorption stage for electrostatically adsorbing an object, wherein the total thickness of the dielectric plate, the adsorption electrode, the relief layer, and the cover layer is within the range of 28 mm to 32 mm. The method of claim 1, An electrostatic adsorption stage for electrostatically adsorbing an object, wherein the volume ratio of silicon carbide to total composite is within the range of 50 to 60 percent. The method of claim 1, An electrostatic adsorption stage for electrostatically adsorbing an object in which the thermal expansion coefficient of the composite is within the range of 9.5 × 10 ⁻⁶ / K to 10.5 × 10 ⁻⁶ / K. A substrate processing apparatus for performing processing on a substrate when the substrate is maintained at a temperature higher than room temperature, comprising the electrostatic adsorption stage according to claim 1 for fixing the substrate during processing. The method of claim 5, And a plasma generator for generating plasma in a space facing the substrate, wherein the processing uses plasma. The method of claim 5, The periphery of the dielectric plate is lowered, A calibration ring is provided on the stage to surround the substrate, and Wherein the calibration ring is to prevent non-uniformity of processing at the periphery of the substrate.