JP3401120B2 - Wafer holding device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a susceptor or a susceptor for holding a wafer such as a semiconductor wafer or a liquid crystal glass substrate used in a manufacturing process of a semiconductor or a liquid crystal substrate. The present invention relates to a wafer holding device such as an electric chuck. 2. Description of the Related Art Conventionally, in a CVD apparatus for forming a thin film on a wafer such as a semiconductor wafer or a glass substrate for a liquid crystal during a manufacturing process of a semiconductor or a liquid crystal substrate, the wafer is held in a processing chamber. At the same time, a wafer holding device such as a susceptor or an electrostatic chuck having a built-in resistance heating element for heating a wafer to a temperature required for film formation has been used. For example, the susceptor has a resistance heating element 13 buried inside a disk-shaped aluminum nitride sintered body 12 as shown in FIG. Lead terminal 1 for energizing body 13
Some were equipped with five. The electrostatic chuck is a base 21 made of a disc-shaped aluminum nitride sintered body as shown in FIG.
In some cases, an electrostatic electrode 24 and a resistance heating element 23 are buried inside, and a lower surface of the base 21 is provided with a lead terminal 25 for supplying electricity to the electrodes 23 and 24. As shown in FIG. 6, the electrodes 13, 23, 24 and the lead terminals 15, 25 are joined by forming an inner hole A on the lower surface of the base 12, 22, A metallized layer B is formed on the surface of A, and lead terminals 15 and 25 made of a metal such as molybdenum or tungsten are joined by a brazing material C. However, in order to form a film on a wafer, a wafer holding device such as the susceptor 11 or the electrostatic chuck 21 must be heated to a temperature of 600 ° C. or more. , Lead terminals 15, 2 of electrodes 13, 23, 24 directly joined to bases 11, 21.
5 was heated to a high temperature in the atmosphere and oxidized. As a result, the resistance values of the lead terminals 15 and 25 change greatly, and it becomes impossible to heat the wafer holding device to a predetermined temperature. In addition, the lead terminals 15 and 25 are
The brazing material C to be bonded to the lead terminals 15 and 2 also reacts with oxygen in the air at a high temperature and corrodes.
There was also a problem that 5 dropped out. Therefore, it is conceivable to coat the lead terminals 15 and 25 and the joints thereof with Ni which is hardly oxidized. However, a Ni film has poor reliability and a wafer holding device having sufficient durability can be obtained. I didn't. In view of the above-mentioned problems, the present invention provides a resistance heating element inside a substrate made of an aluminum nitride sintered body, and the resistance heating element on a lower surface of the substrate. In a wafer holding device provided with a lead terminal for energizing to, a ring-shaped seal member is joined to the lower surface of the base so as to wrap the lead terminal,
The entire lower surface of the base including the lead terminals and the sealing member is coated with any one of ceramic films of silicon carbide, silicon nitride, sialon, and aluminum nitride. According to the present invention, at least the lead terminals and the joints thereof on the lower surface of the base are covered with a ceramic film having excellent oxidation resistance, so that the characteristics of the lead terminals are deteriorated and corrosion of the brazing material is caused. Can be prevented for a long period of time. Also, in the present invention, the use of any one of silicon carbide, silicon nitride, sialon, and aluminum nitride, which is close to the coefficient of thermal expansion of an aluminum nitride sintered body among ceramics, as a ceramic film, enables high temperature operation. Adhesion with the substrate can be improved. Therefore, even if the wafer holding device generates heat at a high temperature, oxygen in the atmosphere does not enter the ceramic film, and the ceramic film does not peel off. Particularly, when aluminum nitride is used as the ceramic film, the ceramic film is made of the same material as the aluminum nitride sintered body constituting the base, so that the reliability can be improved. In addition, when the wafer holding device is disposed inside a processing chamber such as a CVD device, the lead terminals and their joints are exposed to a halide gas. The lead terminals and brazing material are not eroded even in a gas atmosphere. Embodiments of the present invention will be described below. FIG. 1 is a partially cutaway perspective view showing an electrostatic chuck 1 which is an example of a wafer holding device according to an embodiment of the present invention. The heating element 3 and the electrostatic electrode 4 are buried above the inside. Also, as shown in FIG. 2, an inner hole A communicating with the resistance heating element 3 and the electrostatic electrode 4 is formed on the lower surface of the base 2, and a surface of the inner hole A is molybdenum-free.
A metallized layer B made of a manganese alloy is laid, and a metal lead terminal 5 such as tungsten or molybdenum is joined via a brazing material C containing silver. The lead terminal 5 is provided on the lower surface of the base 2.
Ring-shaped sealing member 8 is joined so as to wrap
As shown in FIG. 3, a seal is provided between the seal member 8 and the processing chamber 9 of the film forming apparatus via an O-ring 10 or the like. The entire lower surface of the base 2 including the lead terminals 5 and the seal member 8 is covered with a ceramic film 6 made of one of silicon carbide, silicon nitride, sialon, and aluminum nitride. Lead wires 7 are respectively connected to the tips of the wires 5 so as to energize them. In order to form a film on a wafer 20 such as a semiconductor wafer or a glass substrate for liquid crystal using the electrostatic chuck 1, first, the wafer 20 is placed on the mounting surface 1 a and formed in the processing chamber 9. Supply membrane gas. By applying a voltage between the wafer 20 and the electrostatic electrode 4, a Coulomb force due to dielectric polarization or a Johnson-Rahbek force due to a small leakage current is generated, and the wafer 20 is placed on the mounting surface 1a.
The wafer 20 is heated and fixed to a predetermined temperature by energizing the resistance heating element 3 while adsorbing and fixing the wafer 2 thereon.
0 can form a thin film. Particularly, in the electrostatic chuck 1 according to the present invention, since the base 2 is formed of an aluminum nitride sintered body having a high thermal conductivity among ceramics, the electrostatic chuck 1 itself can generate heat in a short time. In addition, since the wafer 20 can be uniformly heated, a highly accurate thin film can be formed. At this time, the lower surface of the electrostatic chuck 1 is exposed to the atmosphere, and the electrostatic chuck 1 itself is
Since the heat is generated at a high temperature of 0 ° C. or more, the resistance heating element 3
And the lead material 5 for energizing the electrostatic electrode 4 is oxidized, and the brazing material C joining the lead terminals 5 reacts with oxygen in the atmosphere to corrode. The chuck 1 has excellent oxidation resistance over the entire lower surface of the base 2 including the lead terminals 5 and has a silicon carbide, silicon nitride, sialon, and aluminum nitride having a thermal expansion coefficient similar to that of the aluminum nitride sintered body forming the base 2. Are coated with the ceramic film 6 made of one of the above, the ceramic film 6 does not peel off even if the electrostatic chuck 1 generates heat at a high temperature. The lead terminals 5 can be prevented from falling off due to corrosion. However, in order to completely prevent the oxidation of the lead terminals 5 and the corrosion of the brazing material C, the thickness of the ceramic film 6 to be coated is desirably 0.001 mm or more. This is because the thickness of the ceramic film 6 is 0.00
If the thickness is less than 1 mm, the thickness of the ceramic film 6 is too thin, so that it is difficult to sufficiently prevent the oxidation of the lead terminals 5 and the corrosion of the brazing material C. If the thickness of the ceramic film 6 is set to be larger than 1.0 mm, it takes a long time to form the film, and the work efficiency is deteriorated. Therefore, the optimum thickness range of the ceramic film 6 is 0.001 to 1.0 mm, preferably 0.01 to 1.0 mm.
What is necessary is just to make it the range of 5-1.0 mm. On the other hand, in order to manufacture the electrostatic chuck 1 shown in FIG. 1, first, tungsten, molybdenum, titanium carbide,
A green sheet made of aluminum nitride coated with a conductive metal such as titanium nitride or tungsten carbide is laminated in two layers, and a green sheet made of aluminum nitride is laid on the outermost layer to form a laminate. At this time, a small amount of aluminum nitride powder may be added to the conductive metal applied on the green sheet in order to minimize the difference in thermal expansion from the green sheet forming the base 2 and increase the adhesion. Then, after the obtained laminate is subjected to a cutting process to obtain a disc-shaped body, the laminate is subjected to 1600 to 19 in a non-oxidizing atmosphere.
By firing at a temperature of 50 ° C., the base 2 in which the resistance heating element 3 and the electrostatic electrode 4 are embedded is formed. Next, in order to join the lead terminal 5 to the resistance heating element 3 and the electrostatic electrode 4 embedded in the base 2, an inner hole A is formed in the surface of the base 2, and molybdenum is formed in the inner hole A. -1200-150 by applying paste such as manganese alloy
The metallized layer B is formed by baking in a temperature range of 0 ° C., the lead terminal 5 is inserted into the inner hole A on which the metallized layer B is formed, and joined with the brazing material C. Around the lead terminal 5, a ring-shaped sealing member 8 made of tungsten is joined to the lower surface of the base 2 via a brazing material C. In addition, as the material of the lead terminal 5, it is preferable to use a material made of a metal such as tungsten or molybdenum from the viewpoint of enhancing the adhesion to the base 2. As the brazing material C, silver having excellent heat resistance is used. It is good to use the brazing material C containing. Thereafter, the entire lower surface of the substrate 2 including the lead terminals 5 and the sealing member 8 is formed to a thickness of 0.001 to 1 mm by a thin film forming means such as a PVD method such as sputtering or ion plating or a CVD method. The electrostatic chuck 1 shown in FIG. 1 can be obtained by coating the ceramic film 6 made of one of silicon carbide, silicon nitride, sialon, and aluminum nitride. In the above embodiment, the entire lower surface of the electrostatic chuck 1 is covered with the ceramic film 6, but it is sufficient if at least the lead terminals 5 and their joints are covered with the ceramic film 6. Although only the electrostatic chuck 1 has been described in the above embodiment, at least a lead terminal and a joint thereof are formed of silicon carbide, silicon nitride, sialon, and aluminum nitride for a susceptor having a resistance heating element embedded therein. What is necessary is just to cover with the ceramic film 6 which consists of one kind. (Experimental Example) Here, a prototype of an electrostatic chuck 1 made of an aluminum nitride sintered body having a resistance heating element 3 and an electrostatic electrode 4 embedded therein was manufactured. An electrostatic chuck 1 according to the present invention in which the lead terminals 5 of the present invention are coated with two types of ceramic films 6 of an aluminum nitride film and a silicon carbide film, and an electrostatic chuck 1 in which the lead terminals 5 are coated with an alumina film as a comparative example. An endurance test was performed by preparing an electrostatic chuck in which the lead terminal 5 was not covered with the ceramic film 6. The electrostatic chuck 1 of each sample was prepared by adding Y ₂ O ₃ to aluminum nitride powder in an amount of 2% by weight, further adding a binder and a solvent to obtain a slurry, and then forming a plurality of green sheets by a doctor blade method. Was formed. Aluminum nitride powder was added to two green sheets.
3% of tungsten paste added in the range of about
Screen printing was performed at a thickness of 0 μm, and a laminate was sandwiched by other green sheets, and then subjected to cutting to form a disc. Thereafter, the disk-shaped body is placed in a nitrogen atmosphere at 1750.
By firing at a firing temperature of about ° C., an electrostatic chuck 1 having a thickness of about 5 mm in which the resistance heating element 3 and the electrostatic electrode 4 were embedded as shown in FIG. 1 was formed. The porosity of the aluminum nitride sintered body constituting the base 2 of the electrostatic chuck 1 was about 2.0%. Next, an inner hole A having a diameter of about 3 mm communicating with the resistance heating element 3 and the electrostatic electrode 4 is formed on the lower surface of the electrostatic chuck 1, and a paste containing molybdenum-manganese as a main component is applied. Then, a metallized layer is formed by baking at a temperature of 1350 ° C. in a forming gas, and a lead terminal 5 made of molybdenum is inserted into the inner hole A via a brazing material C containing silver. The lead terminal 5 was joined to the base 2 by firing at the temperature of (2). Four electrostatic chucks 1 obtained as described above are prepared, and three of the electrostatic chucks 1
Using an apparatus, an aluminum nitride film, a silicon nitride film, and an alumina film having a thickness of about 0.015 mm were respectively coated. Then, a voltage was applied to the resistance heating element 3 of the electrostatic chuck 1 to generate heat at about 600 ° C., left in the air, and the time until the resistance value of the lead terminal changed was measured. The results are as shown in Table 1. [Table 1] According to the results, in the electrostatic chuck 1 in which the ceramic film 6 is not coated on the lead terminal 5, the resistance value of the lead terminal 5 changes after 10 hours of use, and the lead terminal 5 falls off after 50 hours of use. have done. In the electrostatic chuck 1 in which the lead terminal 5 was coated with an alumina film, the alumina film cracked before 100 hours had elapsed, and the resistance value of the lead terminal 5 changed. On the other hand, in the electrostatic chuck 1 according to the present invention in which the lead terminal 5 is covered with the aluminum nitride film and the silicon nitride film, the ceramic film 6 has no abnormality even after 1000 hours of use, and the resistance of the lead terminal 5 There was no change in the values. Next, of the electrostatic chuck 1 according to the present invention, an aluminum nitride film 6 having a different thickness was covered, and a durability test was performed until the resistance value of the lead terminal 5 made of molybdenum changed. The thickness of the aluminum nitride film 6 and the results are as shown in Table 2. [Table 2] As can be seen from Table 2, Sample No. In the case of coating the aluminum nitride film 6 having a thickness of 0.0008 mm, which is 1, the lead terminal 5 was oxidized and the resistance value changed in 25 hours. In Examples 2 to 5, since the thickness of the aluminum nitride film 6 was 0.001 mm or more, the time required for the resistance value of the lead terminal 5 to change was significantly increased to 900 hours or more. Especially 0.01
Sample N coated with aluminum nitride film 6 of 5 mm or more
o. In the case of 3 to 5, even if heat is generated for 1000 hours, the lead terminal 5
Did not change. Therefore, at least the thickness of the aluminum nitride film 6 is set to 0.001 μm or more, preferably 0.01 μm or more.
If it is 15 mm or more, the lead terminals 5
It can be seen that the oxidation of can be prevented. In the above experiment, an aluminum nitride film and a silicon nitride film were used as the ceramic film 6 covering the lower surface of the electrostatic chuck 1. However, similar results were obtained with other silicon carbide films and sialon films. Obtained. As described above, the present invention provides at least a resistance heating element inside a substrate made of an aluminum nitride sintered body, and a method for supplying electricity to the resistance heating element on the lower surface of the substrate. In a wafer holding device provided with a lead terminal, at least the lead terminal and a joint thereof are covered with a ceramic film of any one of silicon nitride, silicon carbide, sialon, and aluminum nitride, so that a semiconductor wafer or a liquid crystal glass Even if the wafer holding device is heated to heat the substrate, it does not oxidize the lead terminals or corrode the brazing material. Therefore, it is possible to provide a wafer holding device that can stably generate heat for a long period of time without deteriorating the characteristics of the lead terminals.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially broken perspective view showing an electrostatic chuck which is an example of a wafer holding device according to the present invention. FIG. 2 is an enlarged cross-sectional view showing the vicinity of a lead terminal joint of FIG. FIG. 3 is a cross-sectional view showing one state when the electrostatic chuck of FIG. 1 is disposed in a processing chamber of a film forming apparatus. FIG. 4 is a partially broken perspective view showing a susceptor as a conventional wafer holding device. FIG. 5 is a partially broken perspective view showing an electrostatic chuck which is a conventional wafer holding device. FIG. 6 is an enlarged cross-sectional view showing the vicinity of a lead terminal joint of FIGS. 3 and 4; [Description of Signs] 1 electrostatic chuck 2 base 3 resistance heating element 4 electrostatic electrode 5 lead terminal 6 ceramic film

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/205 C23C 14/50 H01L 21/68

Claims (1)

(57) [Claim 1] For holding a wafer such as a semiconductor wafer or a glass substrate for liquid crystal, the base is made of an aluminum nitride sintered body, and a resistance heat is generated inside the sintered body. A wafer holding device having a body and a lead terminal on the lower surface of the base for supplying electricity to the resistance heating element, wherein the lead terminal is wrapped on the lower surface of the base.
And a ceramic film made of any one of silicon carbide, silicon nitride, sialon, and aluminum nitride is coated on the entire lower surface of the base including the lead terminals and the seal member. Wafer holding device.