JP3005981U - Plasma CVD apparatus having a prefabricated susceptor and a prefabricated showerhead in which the change of thin film due to thermal expansion is improved - Google Patents

Abstract

(57) [Abstract] [Purpose] Plasma CVD for forming a continuous and stable thin film by having a screw tightening portion that is not affected by thermal expansion applied to the assembly type susceptor and the assembly type shower head.
Provide the device. A metal having a low coefficient of thermal expansion is melted to form an intermetallic compound in a female screw portion of an aluminum base material, which is an object to be fastened in an assembled susceptor and an assembled shower head, and a bolt seat surface portion. When isoconnel, which is a nickel-based metal, is used for the tightening bolt, nickel is melted in the relevant portion of aluminum as a base material to form an intermetallic compound of aluminum and nickel.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a single-wafer plasma CVD apparatus in which a susceptor and a shower plate forming a reaction chamber are assembled, and more particularly to a single-wafer plasma CVD apparatus that does not affect a formed thin film due to thermal expansion.

[0002]

[Prior art]

 In order to continuously form a thin film on an object to be processed by a single-wafer plasma device, the object to be processed is loaded into the reaction chamber to form a thin film, and after formation, the object to be processed is unloaded from the reaction chamber and processed. In order to remove the portion where the thin film is formed in addition to the body, the process of etching the reaction chamber and carrying the next object to be processed into the reaction chamber is continuously performed.

Since there is no object to be processed when etching the reaction chamber, a thin film is not formed on the upper surface of the susceptor and a thin film corresponding to the part on which the object is placed is not formed. The part exists. Since the etching of the reaction chamber cannot selectively etch only the portion where the thin film is formed, the aluminum surface where the thin film is not formed is also etched.

As described above, the susceptor deteriorates as the number of processed sheets increases, and needs to be replaced. The susceptor to be replaced has an integral structure that employs a heater that is a heating element and a casting or welding structure that includes a thermocouple for temperature control, so it is extremely difficult to replace it regularly. It is expensive. Therefore, it is desirable to use an assembly type susceptor structure so that only the upper surface that deteriorates due to etching can be replaced.

An object to be processed is placed on the upper surface of the susceptor portion. The susceptor is heated to 400 ° C by a heater which is a heat source built into the susceptor.

The susceptor has a built-in thermocouple so as to keep the temperature constant and is controlled by an external controller. If it is technically possible, it is desirable to control the temperature of the target object on which the thin film is formed, but it is technically difficult, so the susceptor on which the target object is placed is controlled to a constant temperature. are doing.

Conventionally, the susceptor has an integral structure that employs casting or welding structure. The reason for this is that in the assembly structure by screw connection, the screw part becomes loose due to the difference in the coefficient of thermal expansion between the tightening bolt and aluminum, which is the material of the susceptor.

Since the heat conduction of the top plate on which the object to be processed is mounted changes from the part containing the heater due to the loosening of the screw, the temperature of the object to be processed decreases and becomes stable continuously. It becomes difficult to form a thin film.

The upper wall of the chamber of the reaction chamber has a structure in which a shower head is attached below the intermediate plate in order to evenly flow the reaction gas to the object to be processed, and an assembly type is adopted. The plasma discharge at the time of forming a thin film and the heat from the susceptor forming the lower wall of the reaction chamber heat the upper wall of the chamber including the showerhead below the intermediate plate.

In the single-wafer plasma CVD apparatus, it is difficult to form a stable and continuous thin film unless the temperature of the shower head directly above the object to be processed placed on the susceptor is controlled to be constant. A thermocouple is placed on the upper wall of the chamber to control the temperature. The shower head, which is the intermediate plate that constitutes the heated chamber upper wall, loosens due to the difference in the coefficient of thermal expansion from the screw that attaches it, and the contact state with the part where the thermocouple is placed changes. As a result, the shower head cannot be controlled at a constant temperature, making it difficult to form a stable and continuous thin film.

[0011]

[Problems to be solved by the device]

 When using parts made of aluminum at a high temperature of 400 ° C with a screw assembly method, and using aluminum of the same material for the mounting screws, the torque tightened at room temperature decreases as the temperature increases, which is not suitable. For this reason, steel bolts that can maintain strength even at high temperatures of 400 ° C are used, but there is a large difference in the coefficient of thermal expansion from aluminum, which is the object to be tightened, and loosening is inevitable. The steel bolts also pressurize the aluminum, which is the object to be tightened, as the temperature rises and apply a compressive load. Aluminum, which has a low creep strength, collapses at the part under compressive load.

Therefore, an object of the present invention is to provide a plasma CVD apparatus that forms a continuous and stable thin film by having a screw tightening portion that is not affected by thermal expansion applied to the assembled susceptor and the assembled shower head. is there.

[0013]

[Means and Actions for Solving the Problems]

 To solve this problem, a metal having a low coefficient of thermal expansion is melted to form an intermetallic compound in the female screw portion and the bolt seat surface portion of aluminum which is the object to be tightened. When using nickel-based metal Isoconel for the tightening bolts, nickel is dissolved in the base material, aluminum, to form an intermetallic compound of aluminum and nickel.

By forming an intermetallic compound, the internal thread portion and the bolt seat surface portion of aluminum, which is the object to be tightened, can be brought close to the thermal expansion coefficient of Isoconel, which is the tightening bolt, and therefore the screw expansion caused by the difference in thermal expansion coefficient Relieves looseness. Since the difference in the coefficient of thermal expansion is small, the axial force of the bolt can be softened, the increase in stress applied around the tightened part can be suppressed, and the deformation of the female screw part and the depression of the bolt seat surface can be reduced.

The formation of the intermetallic compound secondarily improves the mechanical properties of the female screw portion and the bolt seating surface, resulting in partial strengthening.

Metals that can form an intermetallic compound with aluminum include nickel, copper, and chrome. Use one or a combination of metals suitable for the material of the tightening bolt to be used, the surface treatment to be performed in the subsequent process, and the operating conditions. obtain. High density thermal energy is required to partially dissolve the metal in the base material aluminum, and an electron beam welding machine or laser processing machine is suitable.

[0017]

【Example】

 FIG. 1 shows a partial sectional view of a single-wafer plasma CVD apparatus of the present invention. A reaction chamber is formed in the reaction chamber of the CVD device. An intermediate annular portion is attached to the inside of the upper portion of the reaction chamber, and an inner annular portion is attached to the inside thereof. A shower head is provided inside the inner annular portion.

The shower head is composed of a bottom plate having a large number of holes and forming an upper wall of the reaction chamber, and a top plate having a flat upper surface and connected to a pipe for sending a reaction gas. A flat circular cavity is provided in the shower head so that the reaction gas introduced by the pipes can evenly flow out from a large number of holes.

A susceptor that constitutes the lower wall of the reaction chamber is provided so as to be movable up and down, and the wafer is supported by the pins of the wafer lifting pin support mechanism provided therein. The susceptor is roughly divided into three parts. It consists of a top plate on which the wafer is placed, a heater plate for heating the top plate and a heater plate with a thermocouple, and a housing for fixing the heater plate to the lower wall of the reaction chamber.

The present invention stabilizes heat conduction between the top plate and the heater plate. The top plate and the heater plate are fastened with the fastening bolts of Isoconel material.However, in the case of the conventional product in which the intermetallic compound according to the present invention is not formed on the bolt bearing surface of the top plate and the female screw of the heater plate, When the temperature of the supporter is raised to 420 ° C, the top plate and the heater plate expand about 1.01 times due to their thermal expansion, increasing the axial force of the Isoconel material tightening bolt.

When aluminum is in a high temperature state of about 420 ° C., the mechanical properties are remarkably deteriorated, the female screw portion on the heater plate side is deformed, and the bolt seat surface portion on the top plate side is depressed, so that the screw is The attachment is loose. As a result of loose screwing, the adhesion between the top plate and heater plate changes, and the wafer on the top plate cannot be heated to the target temperature accurately. According to the present invention, as shown in FIG. 7, by forming an intermetallic compound on the bolt seat surface portion of the top plate side and the female screw portion of the heater plate side, the amount of screw loosening is greatly reduced.

The above description also applies to the assembly of the shower head bottom plate and top plate with screws.

FIG. 2 is a schematic plan view of the top plate, and the numbers shown in the drawing show the numbers of the screw portions. FIG. 2 (a) is a schematic plan view of a conventional top plate made of only aluminum, and FIG. 2 (b) is a schematic plan view of a plate having an intermetallic compound formed on a screw portion according to the present invention ( Here, “Ni” indicates that an intermetallic compound formed of nickel was formed in the screw portion of the aluminum top plate, and “Cu” indicates that copper was formed in the screw portion of the aluminum top plate. It shows that the intermetallic compound was formed by.

When the CVD apparatus incorporating the top plate shown in FIG. 2 was carried out according to the process shown in FIG. 3, the results shown in Table 1 and FIG. 4 were obtained. That is, each screw is tightened with a torque of 60 Kg · cm, the top plate is heated to 420 ° C., and after the thin film is formed, when the temperature is returned to room temperature, the screw rotation angle is shown when the screws are tightened again. The larger the turning angle, the more loose the screw. As is clear from Table 1 and FIG. 4, when comparing the top plate in which the intermetallic compound is formed with nickel or copper under the same conditions and the conventional product in which the intermetallic compound is not formed, it is found that the intermetallic compound is formed. Can reduce the amount of loosening to about 1/4.

[0025]

[Table 1] Table 1 Loose amount measurement testMaterial Ni Cu Al Screw number 1 2 3 1 2 3 1 2 3 4 5 6 Rotation angle 7.5-6.5 9.0 11.0 9.5 27 25 30 30 28 30  FIG. 6 is a schematic plan view of the top plate similar to that of FIG. 2 when the process is repeated for a long period of time under the condition of forming a thin film and the screw is tightened each time. Table 2 and FIGS. 8 and 9 show the results when the CVD apparatus incorporating this top plate was carried out according to the steps shown in FIG. 7. In this experiment, after heating, the screws were tightened 11 degrees every 6 hours and then measured when returning to room temperature. During the experiment, since 3 of the 6 female threads on the heater plate side of the conventional product were damaged during the process, the tightening torque was lowered from 60 Kg · cm to 30 Kg · cm and the process was continued. .

Under the same conditions, when comparing a top plate on which an intermetallic compound is formed with a conventional product that does not form an intermetallic compound, in the case of the conventional product, the top plate side bolt seat surface depression and the heater plate side The deformation of the female thread is large. Heater plate side The mechanical characteristics at 420 ° C are weak because the threads of 3 of the 6 internal threaded parts were damaged.

As can be seen from Tables 2 (a) and 2 (c), when the intermetallic compound formed of nickel is compared with the conventional product, the loosening amount at the first time is ⅛ and at the second time is 1 It can be suppressed to / 4.

From the deformation amount of the bolt seat surface portion on the top plate side after the 11th retightening shown in FIG. 9, it is possible to confirm the deformation amount that supports the loosening amount.

[0029]

[Table 2] Table 2 High temperature continuous retightening test results (a)Material Ni Number of retightening 1 2 3 4 5 6 7 8 9 10 11 Tightening torque 60 kg · cm Rotation angle (average of 3) 7.0 6.0 4.0 2.7 4.2 3.2 2.7 2.0 2.3 1.7 2.2  (B)Material Cu Number of retightening 1 2 3 4 5 6 7 8 9 10 11 Tightening torque 60 kg · cm Rotation angle (average of 3) 12.0 4.3 5.8 5.0 4.0 3.0 3.2 3.5 3.7 3.0 1.5  (C)Material Conventional product (Al) Number of retightening 1 2 3 4 5 6 7 8 9 10 11 Tightening torque 60.0 kg ・ cm 60 kg · cm Rotation angle (average of 3) 61.0 23.3 − 4.3 3.0 2.0 2.3 2.0 5.0 4.5 4.3

[0030]

【effect】

 By forming an intermetallic compound in the screw part according to the present invention, the looseness of the screw at high temperature can be reduced and the mechanical properties can be improved, so that the spring washer can be used. The conventional product cannot be used because it accelerates the deformation of the top plate side bolt bearing surface and the heater plate side female screw.

Further, if an intermetallic compound is formed, it becomes possible to absorb the slackness due to the difference in the coefficient of thermal expansion, which has become minute, by the spring washer, so that heat conduction between the top plate and the heater plate can be secured.

[Brief description of drawings]

FIG. 1 shows a schematic sectional view of a CVD apparatus.

FIG. 2 shows a schematic plan view showing the numbers of the screws that fasten the top plate of the assembled susceptor.

FIG. 3 shows a test process performed on a CVD apparatus.

FIG. 4 shows a rotation angle of a screw for tightening a screw indicated by a screw number.

FIG. 5 is a schematic cross-sectional view of a threaded portion formed with an intermetallic compound according to the present invention.

FIG. 6 shows a schematic plan view showing the numbers of the screws that fasten the top plate of the assembled susceptor.

FIG. 7 shows another test process performed on the CVD apparatus.

FIG. 8 shows the relationship between the number of times a screw is retightened and its rotation angle when a test process is performed for a long time.

FIG. 9 shows a deformation amount of a screw hole corresponding to a screw indicated by a screw number.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/31 // C23F 4/00 A 8414-4K

Claims (4)

[Scope of utility model registration request] 1. An object to be processed is placed on an assembly-type susceptor by screw connection, which constitutes a lower wall of the reaction chamber of the reaction chamber, and is positioned above the object to be treated, and constitutes an upper wall of the reaction chamber. In the plasma CVD apparatus in which the reaction gas flows from the shower head to the object to be processed and a thin film is formed on the object to be processed, it is stable by having the screw tightening portion that is not affected by the thermal expansion applied to the assembly type susceptor by the screw coupling. A plasma CVD apparatus characterized by forming a thin film. 2. The plasma CVD apparatus according to claim 1, wherein the material of the susceptor is aluminum so as to reduce the coefficient of thermal expansion in and around the female screw portion of the assembly type susceptor by the screw coupling. A plasma CVD apparatus, in which a metal having a coefficient of thermal expansion lower than that of aluminum is melted to form an intermetallic compound. 3. An object to be processed is placed on a susceptor forming the lower wall of the reaction chamber of the reaction chamber, and is positioned above the object to be processed, and is assembled by screw connection forming the upper wall of the reaction chamber. In a plasma CVD apparatus in which a reaction gas flows from a showerhead to the object to be processed to form a thin film on the object to be processed, a screw tightening portion that is not affected by the thermal expansion applied to the assembled showerhead by the screw coupling is provided, and thus stable Plasma CVD characterized by forming a thin film
apparatus. 4. The plasma CVD apparatus according to claim 3, wherein the showerhead is made of a material so as to reduce the coefficient of thermal expansion around the female screw portion and the periphery of the female screw portion of the assembled showerhead by the screw coupling. A plasma CVD apparatus characterized in that an intermetallic compound is formed by melting a metal having a coefficient of thermal expansion lower than that of aluminum in aluminum.