TWI342059B - Electrostatic chuck - Google Patents

Description

1342059 (1) EMBODIMENT OF THE INVENTION [Technical Field] The present invention relates to an electrostatic chuck in which an adsorbate such as a semiconductor wafer and a glass substrate for FPD is adsorbed and fixed by electrostatic force. [Prior Art] The conventional electrostatic chuck ceramic dielectric system is constructed for the purpose of controlling the characteristics of the electricity (for example, refer to Japanese Patent Laid-Open Publication No. Hei. In this case, when the ceramic structure is exposed to the plasma environment, the tissue is eroded and the surface is deteriorated. The result is that the contact state between the surface of the electrostatic chuck and the wafer changes, causing a change with time ( Variation with time ) or dust in which particles are detached from the sintered body to become particles, causing a cause of short-circuiting between wirings of the LSI or the like. In addition, an alumina ceramic material having a particle diameter of 2 // m or less and a relative density of 99.9% to improve the plasma resistance is used for an electrostatic chuck (for example, refer to Japanese Patent Laid-Open No. 2). However, in this case, although there is good resistance to plasma, the physical properties of the electricity are not described, and the basics of the so-called Johnsen-Rahbek type electrostatic chuck which can find a large adsorption force cannot be obtained. The function comes out. Further, an alumina ceramic having a volume resistivity of from 10 〇 G to 1 〇 4 Ω cm has been described for containing 0.1 to 1 wt% of titanium oxide (for example, refer to Japanese Patent Laid-Open Publication No. 3). However, in this case, the characteristics of the electric power that causes the electrostatic chuck to function are not obtained. Further, an electrostatic chuck in which 0.5 to 2 wt% of oxidized (2) 1,342,059 titanium is added to an alumina ceramic to reduce the volume resistivity has been described (for example, see Patent Document 4). In this case, adding less than 0.5 wt% of the electric resistance does not decrease. Adding 2 wt% or more, the current is excessively flowed. It is also described that the titanium oxide precipitates to the grain boundary of the alumina ceramic. That is, to reduce the volume resistivity, at least an additive of 0 · 5 w t % or more is added. 'The electrostatic chuck which has strict restrictions on the impurities to be adsorbed is too much additive. In addition, for alumina, the amount of alumina is 99% or more, and the average particle diameter is 1 to 3/zm. At 300 to 500 °C, the volume resistivity becomes 1〇8~1〇" It is described (for example, refer to Japanese Patent Laid-Open Publication No. 5). However, other than the above, for example, the physical properties of the dielectric body necessary for the electrostatic chuck used at a lower temperature of 100 ° C or less are not described. Japanese Patent Publication No. 3 0 8 4 8 9 9 Patent Document 2: Japanese Patent Laid-Open Publication No. Hei No. Hei. No. Hei. No. Hei. Japanese Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. After the pulverization, the smooth surface can be maintained. As a result, contamination of the particles caused by the adsorbate such as the ruthenium wafer can be suppressed, and the adsorption and detachment characteristics of the adsorbed body are excellent, and the -6 - (3) ) 1342059 • It is easy to make it by heating it. Electric chuck. <Means for Solving the Problem> In order to achieve the above object, the present invention is characterized in that it has an alumina of 99.4% by weight or more and a titanium oxide of more than 0.2 wt%. And an electrostatic chuck of a dielectric body for an electrostatic chuck having a volume resistivity of 0.6 wt% or less and a volume resistivity of 1 〇 8 to 10 11 Ω cm at room temperature and segregation of titanium oxide to the grain boundary of the alumina particles. φ This result is to improve the anti-plasma property of the electrostatic chuck dielectric and to improve the basic functions of the electrostatic chuck, and it can be manufactured at a low price. The volume resistivity must be 1 08~1 0 1 1 Ω cm, which is the application of the Johansen-Labbek effect as the electrostatic chuck. The Johansen-Larbek effect is applied to produce a very strong adsorption force. The result is that a convex portion is provided on the surface of the electrostatic chuck to reduce the contact area with the adsorbed object with respect to the area of the adsorption surface. 〜1 0% 〇# Further, the height of the convex portion provided on the surface is changed to 5 to thereby the adsorption force can be applied even by the contact portion. As a result, the area of the convex portion can be made 0.001% or more and less than 〇 · 5 % with respect to the area of the adsorption surface. The temperature of the adsorbate becomes smaller as the contact area of the convex portion becomes smaller, and heat is transmitted through the contact portion, so that the influence of the structure of the convex portion by plasma erosion is still small. Therefore, the improvement of the plasma resistance and the contact with the adsorbate are extremely reduced, and as a result, an electrostatic chuck which changes little with time can be realized. In addition, in order to make the above-mentioned adsorption force good, it is necessary to reduce the following formula (4) (4) (second ε r + d / h )

1342059 The son of the child. Ts = 1.731x10'1!x/9 Here, ts is the time (seconds) from the initial adsorption force of 100% to 2% until the destruction, volume resistivity (Ω cm), er is The thickness (m) of the specific dielectric layer of the electric layer, h is the height (m) of the convex portion of 0.001 to 0.6, and the height of the convex portion is 5 to 15 / / m. The area of the convex portion becomes 0.0 with respect to the adsorption surface. 0 1~ It can be formed as a voltage to which an adsorption force is applied, and an electrostatic chuck which is excellent in load.

The above equation is obtained by the equivalent circuit in Fig. 1 and derived from [Equation 1] to [Expression 4]. For this density, S is the electrode area, C is the electrostatic capacitor, G is applied with voltage, t is time (variable), T is voltage applied 丨 [Expression 1]) The adsorption force decreases P is the electrical potential of the dielectric, d For introduction. If the 値 of the formula is 〇 5 5 5 , , , 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5

91 (0 = 9, (0 + ^ (0)

Cl7r^-Kwpi =ci

Cr + C3 (2) l - fexp

Gl + / > Γ ?. (0 = ¢, (/) + grO) Γ) + - Γ)} (3) (4) [Expression 2] 2 (C, +C,) G, (5) 1342059 [Expression 3] C' = £〇f C2 = £0£r^-h G2 =—=— Pd [Expression 4] i>t 9i =ci

c, + c2 V - fexp + c; Further, the electrostatic chuck according to another embodiment of the present invention is characterized in that: alumina is 99.4% by weight or more, and titanium oxide is more than 2% by weight and 0.6 wt%. The following is an electrostatic chuck for a structure in which the bulk density is 3.97 g/cm3 or more, and the volume resistivity at room temperature is 1 08 to 1 0 1 1 Ω cm, and the titanium oxide is segregated to the grain boundary of the alumina particles. Electric body. The result is that the electrostatic chuck is such that the porosity of the structure is small, the resistance to plasma is improved, and the basic functions of the electrostatic chuck can be coexisted, and it can be manufactured at a low price.

An electrostatic chuck according to any one of claims 1 to 4, wherein the electrostatic chuck has a plurality of convex portions formed thereon and the adsorbed body is placed on the convex portion. a smooth surface dielectric body, wherein a ratio of a total area of the plurality of convex portions to an area of the surface of the dielectric body is 0.001% or more and less than 0.5%, and a height of the convex portion is 5 to 15 #m . As a result, the contact portion with the object to be adsorbed can be roughened by the erosion of the plasma, and the influence of the surface roughness on the adsorption state of the adsorbate can be minimized. At this time, the ratio of the contact area becomes 0.001% or less, and the size of each convex portion becomes (6) 1342059 Excessive fineness, which causes difficulty in processing. In addition, greater than! % The surface of the convex portion in contact with the adsorbent is not affected by the plasma erosion. [Embodiment] The raw material is alumina, titanium oxide, or other transition metal oxygen. The blending ratio shown in Table 1 is granulated. Alumina having an average of 0.1 z/m and a purity of 99.99% or more is prepared. Use pure titanium oxide. (Slurry adjustment, granulation, original processing) The above raw materials were mixed at a mixing ratio shown in Table 1, and after adding a propylene-based adhesive, the particles were prepared by spray drying granulation. The granule powder is packed into a CIP (pressure lton/cm2) in a rubber mold to form an ingot, and then the shape is processed to prepare an initial formed body. When mixing, use ion exchange. Do not mix impurities. (Calcination) The raw calcination temperature was set to 50 °C in a reducing atmosphere of nitrogen and hydrogen, and the firing time was set to a condition in which the bulk density of 1 to 8 was the largest. At this time, in order to remove the fat, it is necessary to carry out the reduction firing because the non-stoichiometric amount of the titanium oxide is performed, and the volume resistivity is adjusted. And it is ignored by the law. The material is pulverized by a particle diameter of 9 8 % or more, and then it is processed into a specific water or the like. When it is selected, wet gas is selected. The composition is for the purpose of -10- (7) (7) 1342059 (HIP processing) Next, HIP processing is performed. The HIP condition is set to Ar gas at 1,500 Torr. The temperature is set to be the same as or lower than the firing temperature by 3 (temperature of TC. (Measurement of physical properties). The article obtained by the HIP treatment described above is used, and the bulk density of the fired body and the fired body are used. The SEM observation was carried out to measure the average particle diameter, the volume resistivity, the friction in vacuum, and the residual time. The friction measurement and the residual time were determined by setting the thickness of the ceramic dielectric layer to 1 mm. The adsorption voltage of 200 V was applied, and after the voltage was applied for 1 minute, the power was cut off, and the residual frictional force was measured. The adsorbed material was the mirror surface of the crucible. The residual time was attenuated to 2% after the power supply was cut off. The time is taken as the residual time. In addition, the plasma is actually irradiated and the surface roughness (center line average roughness Ra) of the ceramic is measured. In the initial state, the surface roughness becomes Ra 0.05 /zm or less. The plasma is filled with reactive ions. In the device, the etching gas is CF4+02 1000W, and the plasma is discharged for 5 hours. In addition, after the pressure of He gas is applied to the adsorbed adsorbed body, The pressure (POP OFF adsorption force) when the adsorbed body is detached is recorded, and the practical adsorption force of the electrostatic chuck is evaluated for a part of the sample. The adsorption voltage at this time is 10 〇〇V. (Comparative) For the purpose of comparison, the alumina ceramics 11 - (8) (8) 1342059 of the conventional method was exemplified. The preparation of the comparative product 1 was a tin oxide having an average particle diameter of 0·5 μηι 98 wt / /, and a titanium oxide 2 wt % The blending of Comparative Product 2 was 99 wt% of alumina, 1 wt% of titanium oxide, and the calcination temperature was 1580 ° C. Further, in the initial state, the surface roughness of Comparative Product 1 was Ra 0.2 3 μm. In the initial state, the surface roughness of the comparative product 2 was R a 0 · 2 /zm. The comparative product was not subjected to IP treatment. The results of the above tests are shown in Tables 1 and 2. It is known that if the control is fired At the temperature, the addition amount of titanium oxide is more than 0.2 wt% and 0.6 wt% or less, and the bulk density is 3.97 g/cm 3 or more, and the volume resistivity of the function of the electrostatic chuck is obtained. It is known that the particle diameter is 50// The amount added in the case of m or more is compared, and the equivalent is obtained with a very small amount of addition. In the past, in order to increase the calcination temperature to 158 ° C, the added titanium oxide reacts with alumina to form a compound such as aluminum titanate (Al 2 Ti 05 ), whereas the present invention is An alumina raw material having a high particle diameter of 〇·2 μ m and a purity of 99.9% or more is used to lower the firing temperature to 1 300 ° C or lower, and the added titanium oxide does not react with oxidation and the titanium oxide remains It is confirmed that this is confirmed by the X-ray fold. It is known that the volume resistivity of aluminum titanate is relatively high, and it is considered that in order to reduce the volume resistivity of alumina, the efficiency is worse than that of titanium oxide. Add more amount. Next, an SEM photograph of a sample which is thermally etched at a temperature lower than the firing temperature by about 80 to 150 as a fine structure of the dielectric body for the electrostatic chuck of the present invention is shown in Fig. 4. It is known that titanium oxide (white portion of the photograph) segregates to the grain boundary of alumina particles with an average particle diameter of 2 // m or less (black portion of the photograph), -12- (9) (9) 1342059 is formed into continuity The structure of the link. It is considered that the network formed by the titanium oxide can be utilized to lower the volume resistivity. From the above results, compared with the conventional dielectric body for electrostatic chucks, the dielectric body for electrostatic chucks of the present invention can reduce the volume resistivity by adding a small amount of titanium oxide, because the added titanium oxide is not The alumina reacts, the titanium oxide remains, and the titanium oxide segregates to the grain boundary of the alumina particles, and is formed into a structure that is continuously connected. Further, it is considered that titanium oxide becomes a non-stoichiometric composition by reduction firing, and conductivity is further improved. It is considered that in this way, a small amount of titanium oxide can be used to control the volume resistivity, and the chemical contamination caused by the germanium wafer or the like can be more suppressed than in the past. [Table 1] NO. Alumina oxide firing temperature °c Bulk body bulk density g/cm3 1 100 wt% Owt% 1240 3.79 2 100 wt% Owt% 1270 3.88 3 99.9 wt% 0.1 wl% 1300 3.78 4 99.9 wt % 0.1 wt% 1240 3.89 5 99.8 wt% 0.2 wt% 1210 3.74 6 99.8 wt% 0.2 wt% 1240 3.89 7 99.7 wt% 0.3 wt% 1180 3.23 8 99.7 wt% 0.3 wt% 1210 3.91 9 99.6 wt% 0.4 wt% 1180 3.60 10 99.6 wt% 0.4 wt% 1210 3.92 11 99.5 wt% 0.5 wt% 1150 3.60 12 99.5 wtX 0.5 wt% 1180 3.92 13 99.4 wt% 0.6 wt% 1150 3.92 14 99.4 wt% 0.6 wt% 1180 3.92 Comparative 1 98 wt% 2wt% 1580 3.75 Comparative substance 2 99wt% 1wt% 1580 3.7 -13- (10) (10) 1342059 [Table 2] NO. mm bulk density g/cm3 average particle diameter of fired body X/m volume resistivity after HIP treatment Qcm 200V Friction force gf/cm2 when applied. Residual time seconds. Thick front surface of the plasma. «ISRa U m Surface roughness Ra Untreated after slurry treatment 2 3.98 0.9 >10,5 >400 >300 0.03 0 06 4 3.98 t.1 1015 >400 >300 0Ό3 0,06 6 3.98 1.3 To^ >400 120 0.03 0.06 8 3.98 1.4 10'° >400 5 0.03 0.06 10 3.98 1.5 10w >4〇〇A nmnm 12 3.98 1.5 1 08 5 ~~' >400 1 0.03 0 07 14 3.97 1.7 10® 3 >400 1 0.03 0.07 Comparison 1 - 80 1〇103 [>400 15 0.23 056 Comparison 2 - 70 10n >400 30 0.2 As a result of evaluation of the electrical characteristics of 0.6, it is known that it can be controlled by titanium oxide alone or titanium oxide + transition metal oxide in a wide range of 1 〇 8 〜 8 〇 16 Ω C m . In the case of using a resist, it is preferable to use an electrostatic chuck at 100 ° C or less in consideration of the heat resistant temperature. The electrical characteristics required for the dielectric body for the electrostatic chuck are preferably such that the volume resistivity is 1 〇 8 〜 1 〇 UQ cm at the temperature at which the electrostatic chuck is used. If the lower limit is less than 081 08 Ω c m, there is a fear that the current flowing into the wafer will become excessively large and damage the device. Above the lower limit 値10MQcm, the response to the application of the detached voltage of the wafer is reduced. For example, in the etching process of 100 ° C or higher, it is preferable that the lower limit 1 is 1 08 to 1 0 1 1 Ω cm. When the titanium oxide is more than 0.6 wt%, the volume resistivity becomes less than 1 〇8. There is a fear that the current flowing into the wafer will become excessively large and damage the device. Further, the amount of titanium oxide is 0.2 wt%, and the effect of reducing the volume resistivity by adding titanium oxide is small. If the energy of the ions in the plasma is too large, the substance -14-(11) 1342059 will be etched, so the resistance to plasma is evaluated by the change in surface roughness. As a result, in the ceramic dielectric body of the present invention, the change in surface roughness is remarkably smaller than in the past. This situation is presumed to be due to the small size of the dust particles. Formed: a plurality of convex portions are formed and have a smooth surface on which the adsorbed body is placed on the convex portion, and the convex portion of the electrostatic chuck containing the dielectric constant of the electrostatic chuck for the volume resistivity of 1093 Ω cm The ratio of the total area of the upper surface to the area of the surface of the dielectric body was 0.089 % by electrostatic chuck. At this time, on the surface, a convex portion of Φ 〇.25ιηιη is arranged in connection with each vertex of an equilateral triangle having a side of 8 mm. The height of the convex portion is 10/m. As a result, the temperature change of the tantalum wafer belonging to the adsorbate during the process can be changed in a state in which the change in the surface roughness after the plasma irradiation is small and the contact area with the adsorbate is extremely small. The change over time is extremely rare. • The record of POPOFF adsorption is 100 rr or more for all samples. That is, it is known that when an adsorbed body such as a tantalum wafer is to be adsorbed, a sufficiently practical adsorption force is obtained. [Effect of the Invention] According to the present invention, it is possible to maintain a smooth surface after being exposed to a plasma, and as a result, it is possible to suppress contamination of particles caused by an adsorbate such as a ruthenium wafer, and to have an excellent adsorbed body. The adsorption and detachment characteristics are produced by low-temperature firing, and it is easy to make the electrostatic chuck -15-

Claims (1)

1342059 X. Patent application No. 096 1 04666 Patent application Chinese patent application scope revision The Republic of China 9 9 years 1 Revision year Ε...t 1. An electrostatic chuck with sintering of alumina and titanium oxide The dielectric body formed by the body is characterized by: When the weight percentage of alumina is X, the weight percentage of titanium oxide is (100-X), X is 99.4 wt% or more, smaller than 99.8 wt%, and the volume resistivity at room temperature is 1 08~1 Ο &quot ; Ω cm, and the dielectric layer of the electrostatic chuck for the segregation of the titanium oxide to the grain boundary of the alumina particles and the continuous connection structure 1 342 059 064 046 046 096 096 096 096 096 096 096 096 096 096 096 096 096 096 096 Π r VII (single simplification: rhyme is a symbol of the table element generation 圊: means that the table pattern represents the present generation /-N /-N fixed 2 fingers / IV 1) Description: no 1 convex part 2 convex part bottom surface 3 Gas supply hole 4 Annular convex part (sealing ring) 5 Concave part (gas diffusion groove) 6 Electrode 7 Dielectric layer 8 Adsorbed body 9 Electrical connection means 10 Base plate 11 Power supply 8. If there is a chemical formula in this case, please disclose The chemical formula that best shows the characteristics of the invention: none -4-