Film forming apparatus, control device, and pressure gauge adjustment method

A film forming apparatus includes: a pressure-reducible processing container; a pressure gauge configured to detect a pressure in the processing container; and a controller, wherein the controller is configured to repeat a cycle including a step of adjusting a zero point of the pressure gauge and a step of executing a film forming process in the processing container until an ultimate pressure, which is detected by the pressure gauge when an interior of the processing container is evacuated to a highest reachable vacuum degree after the step of executing the film forming process, reaches a target range.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-191461, filed on Oct. 18, 2019, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a film forming apparatus, a control device, and a pressure gauge adjustment method.

BACKGROUND

Among diaphragm-type pressure measurement devices for measuring the pressure inside a pressure-reducible pressing container, there is known a pressure measurement device capable of reducing, even when a solid is attached to the diaphragm, the influence of stress exerted by the attached solid on the deformation of the diaphragm (see, for example, Patent Document 1).

PRIOR ART DOCUMENT

Patent Document

SUMMARY

According to one embodiment of the present disclosure, there is provided a film forming apparatus including: a pressure-reducible processing container; a pressure gauge configured to detect a pressure in the processing container; and a controller, wherein the controller is configured to repeat a cycle including a step of adjusting a zero point of the pressure gauge and a step of executing a film forming process in the processing container until an ultimate pressure, which is detected by the pressure gauge when an interior of the processing container is evacuated to a highest reachable vacuum degree after the step of executing the film forming process, reaches a target range.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments. In all of the accompanying drawings, the same or corresponding members or components will be denoted by the same or corresponding reference numerals, and redundant explanations will be omitted.

FIG. 1is a schematic view illustrating an exemplary configuration of a film forming apparatus according to an embodiment. As illustrated inFIG. 1, a film forming apparatus1includes, for example, a processing container10, a gas supply part30, an exhaust part40, a heater50, a pressure gauge60, and a controller80.

The processing container10is pressure-reducible and accommodates a semiconductor wafer (hereinafter referred to as a “wafer W”), which is a substrate. The processing container10has a cylindrical inner tube11having a ceiling and a lower open end, and a cylindrical outer tube12having a lower open end and a ceiling covering the outside of the inner tube11. The inner tube11and the outer tube12are formed of a heat-resistant material such as quartz, and are arranged coaxially so as to form a double-tube structure.

The ceiling of the inner tube11is, for example, flat. On one side of the inner tube11, an accommodation part13configured to accommodate a gas nozzle is installed along the longitudinal direction (vertical direction) of the inner tube11. In an embodiment, a portion of the side wall of the inner tube11protrudes outward so as to form a convex portion14, and the inside of the convex portion14is formed as the accommodation portion13.

In the side wall of the inner tube11opposite the nozzle accommodation part13, a rectangular opening15is formed in the longitudinal direction thereof (the vertical direction).

The opening15is a gas exhaust port formed so as to be capable of exhausting the gas within the inner tube11. The length of the opening15is equal to the length of a wafer boat16, or extends in the vertical direction to be longer than the length of the wafer boat16.

The lower end of the processing container10is supported by a cylindrical manifold17formed of, for example, stainless steel. A flange18is formed at the upper end of the manifold17, and the lower end of the outer tube12is installed and supported on the flange18. A seal member19, such as an O-ring, is interposed between the flange18and the lower end of the outer tube12such that the inside of the outer tube12is hermetically sealed.

An annular support part20is installed in the inner wall of the upper portion of the manifold17, and the lower end of the inner tube11is installed and supported on the support part20. A lid21is hermetically installed to the opening at the lower end of the manifold17via a sealing member22, such as an O-ring, so as to hermetically close the opening at the lower end of the processing container10, that is, the opening of the manifold17. The lid21is formed of, for example, stainless steel.

A rotary shaft24configured to rotatably support the wafer boat16via a magnetic fluid seal23is installed in the central portion of the lid21. The lower portion of the rotary shaft24is rotatably supported by an arm25A of a lift mechanism25configured as a boat elevator.

A rotary plate26is installed at the upper end of the rotary shaft24, and the wafer boat16that holds wafers W is placed on the rotary plate26via a quartz heat insulating base27. Therefore, by moving the lift mechanism25up and down, the lid21and the wafer boat16integrally move up and down so that the wafer boat16can be inserted into and removed from the inside of the processing container10. The wafer boat16is a substrate holder that is capable of being accommodated in the processing container10and holds a plurality of wafers W substantially horizontally at predetermined intervals in the vertical direction.

The gas supply part30is installed in the manifold17. The gas supply part30introduces gases, such as a film forming gas, a cleaning gas, and a purge gas, into the inner tube11. The gas supply part30has a gas nozzle31.

The gas nozzle31is made of, for example, quartz, and is installed within the inner tube11in the longitudinal direction of the inner tube11. The base end of the gas nozzle31is bent in an L shape and passes through the manifold17so as to be supported. The gas nozzle31has a plurality of gas holes32formed along the longitudinal direction thereof, and a gas is ejected horizontally from the gas holes32. The gas holes32are arranged, for example, at the same interval as the interval between the wafers W supported by the wafer boat16. The gas nozzle31is a nozzle that supplies a gas, such as a film forming gas, a cleaning gas, or a purge gas, and supplies the gas into the processing container10as necessary while controlling the flow rate.

The film forming gas is a gas for forming a film on the wafers W, and is selected according to the type of film to be formed. For example, when forming a silicon oxide film, a silicon source gas and an oxidizing gas may be used as film forming gases.

Examples of the silicon source gas include aminosilane gases such as diisopropylaminosilane (DIPAS), trisdimethylaminosilane (3DMAS), tetrakis(dimethylamino)silane (4DMAS), and bis(tertiary-butylamino)silane (BTBAS).

Examples of the oxidizing gas includes O2gas, O3gas), CO2gas. NO gas, N2O gas, and H2O gas, and these gases are plasmarized by a radio-frequency electric field so as to be used as oxidizing species, if necessary. As the oxidizing species, O2plasma is preferable. When O3gas) is used, plasma is unnecessary.

The cleaning gas is a gas for removing the film deposited in the interior of the processing container10. Examples of the cleaning gas may include fluorine-containing gases, such as HF gas, F2gas, and ClF3gas.

The purge gas is a gas for removing and purging the film forming gas and the cleaning gas remaining in the processing container10. Examples of the purge gas may include inert gases such as nitrogen gas and argon gas.

In addition, in the example ofFIG. 1, the case in which the gas supply part30has one gas nozzle31has been described, but the form of the gas supply part30is not limited thereto. For example, the gas supply part30may have a plurality of gas nozzles therein.

The exhaust part40exhausts the gas discharged from the inside of the inner tube11through the opening15and discharged from the gas outlet41through the space P1between the inner tube11and the outer tube12. The gas outlet41is formed in the upper sidewall of the manifold17and above the support part20. An exhaust passage42is connected to the gas outlet41. A pressure adjustment valve43and a vacuum pump44are sequentially interposed in the exhaust passage42so as to evacuate the inside of the processing container10.

The heater50is installed around the outer tube12. The heater50is installed, for example, on the base plate28. The heater50has a cylindrical shape so as to cover the outer tube12. The heater50includes, for example, a heating element, and heats the wafers W in the processing container10.

The pressure gauge60is installed in the upstream side of the pressure adjustment valve43in the exhaust passage42, and detects the pressure in the processing container10. The pressure gauge60may be, for example, a diaphragm vacuum gauge. The pressure gauge60transmits a detected pressure to the controller80. Further, the zero point of the pressure gauge60is automatically adjusted by the controller80.

The controller80is an example of a control device, and controls the operation of the film forming apparatus1. The controller80may be, for example, a computer. A computer program for executing the overall operation of the film forming apparatus1is stored in a storage medium90. The storage medium90may be, for example, a flexible disc, a compact disc, a hard disc, flash memory, or a DVD.

[Operation of Film Forming Apparatus]

First, as an example of the operation of the film forming apparatus1, a film forming process for forming a silicon oxide film on wafers W will be described.

At normal temperature, a wafer boat16accommodating, for example, 50 to 150 wafers W is loaded into the processing container10, the temperature of which is controlled, by raising the wafer boat16from the lower side of the processing container10. In addition, the inside of the processing container10is sealed by closing the opening at the lower end of the manifold17with the lid21. The wafers W have a diameter of, for example, 30 mm.

Subsequently, the inside of the processing container10is evacuated to maintain the process pressure, and the power supplied to the heater50is controlled so as to raise the wafer temperature to maintain the process temperature at a temperature of, for example, 450 degrees C. or lower. Then, the film forming process is started in a state in which the wafer boat16is rotated.

The film forming process is a process of forming a silicon oxide film on wafers W by, for example, so-called atomic layer deposition (ALD) in which a step of supplying a silicon source gas and a step of supplying an oxidizing gas are alternately repeated. Further, the film forming process may include a step of removing the gas remaining in the processing container10(hereinafter referred to as “residual gas”) from the inside of the processing container10between the step of supplying the silicon source gas and the step of supplying the oxidizing gas.

In the step of supplying the silicon source gas, the silicon source gas is adsorbed onto the wafers W by supplying the silicon source gas into the processing container10through the gas holes32in the gas nozzle31. The time for which the silicon source gas is supplied in the step of supplying the silicon source gas is, for example, 1 to 180 sec, the flow rate of the silicon source gas is, for example, 1 to 1000 sccm, and the pressure in the processing container10is, for example, 13.3 to 1333 Pa (0.1 to 10 Torr).

In the step of supplying the oxidizing gas, the silicon source gas adsorbed on the wafers W is oxidized by supplying the oxidizing gas from the gas holes32of the gas nozzle31into the processing container10. At this time, if necessary, radio-frequency power may be applied to plasmarizing the oxidizing gas to generate oxygen radicals so as to oxidize the silicon source gas adsorbed on the wafers W. The time for supplying the oxidizing gas in the step of supplying the oxidizing gas is, for example, 1 to 300 sec, the flow rate of the oxidizing gas is, for example, 100 to 20000 sccm, and the pressure in the processing container10is, for example, 13.3 to 1333 Pa (0.1 to 10 Torr). The frequency of the radio-frequency power when applying the radio-frequency power is, for example, 13.56 MHz, and the power is, for example, 5 to 1000 W.

In the step of removing the residual gas, the purge gas is supplied into the processing container10through the gas holes32of the gas nozzle31while the processing container10is evacuated. The step of removing the residual gas is performed, for example, after the step of supplying the silicon source gas and after the step of supplying the oxidizing gas. The time for supplying the purge gas in the step of removing the residual gas is, for example, 1 to 60 sec, the flow rate of the purge gas is, for example, 50 to 20000 sccm, and the pressure in the processing container10is, for example, 13.3 to 1333 Pa (0.1 to 10 Torr). In the step of removing the residual gas, for example, the evacuation may be continued without supplying the purge gas in a state in which the supply of all the gases is stopped. However, it is possible to remove the residual gas in the processing container10in a short time by supplying the purge gas.

In this manner, by repeating the step of intermittently supplying the silicon raw material and the step of supplying the oxidizing gas alternately with the step of removing the residual gas from the inside of the processing container10interposed therebetween, it is possible to form a silicon oxide film having a desired film thickness. After the film forming process is finished, the wafers W are unloaded from the inside of the processing container10in the reverse order of the procedure of loading the wafers W into the processing container10.

Next, as another example of the operation of the film forming apparatus1, a cleaning process for removing the film deposited in the processing container10will be described.

In the cleaning process, in a state in which the wafer boat16, which does not accommodate product wafers W, is placed on the heat insulating base27, the wafer boat16is loaded into the processing container10, which is heated to a set temperature, by being raised from the lower side of the processing container10. Subsequently, the inside of the processing container10is sealed by closing the opening in the lower end of the manifold17with the lid21. Subsequently, the cleaning gas is supplied into the processing container10through the gas holes32of the gas nozzle31while the processing container10is evacuated. Asa result, reaction products attached to, for example, the inner wall of the processing container10, the wafer boat16, the heat insulating base27, and the gas nozzle31, are removed. The temperature in the processing container10during the cleaning process is, for example, 0 to 600 degrees C., preferably 25 to 475 degrees C.

FIG. 2is a view illustrating an exemplary pressure gauge60. As illustrated inFIG. 2, the pressure gauge60is a diaphragm vacuum gauge that detects deformation of a diaphragm61disposed at a boundary between a reference pressure chamber62and a measurement pressure chamber63communicating with the inside of the processing container10, thereby measuring the pressure in the measurement pressure chamber63.

The diaphragm61is bent due to the pressure difference between one side surface and the other side surface thereof. That is, the diaphragm61is deformed axially symmetrically about the center thereof. For example, when the pressure of the measurement pressure chamber63is higher than the internal pressure of the reference pressure chamber62, the central portion of the diaphragm61is moved (deformed) upward (the −y direction in the drawing).

In the diaphragm61, when the gas flowing into the measurement pressure chamber63contains solids (e.g., particles), and when the solids are attached to the surface of the diaphragm61, stress is generated in the surface of the diaphragm61by the solids attached thereto. In the diaphragm61, for example, when the attached solids form a film and the film contracts, contraction stress is generated on the surface of the diaphragm61. At this time, when the pressure is measured based on the deformation of the diaphragm61, the generated stress is a positive shift stress (f in the drawing) that causes the measured pressure to be excessively high, or a negative shift stress that causes the pressure to be measured to be excessively low (f2in the drawing). As described above, in the pressure gauge60, when the solids are attached to the surface of the diaphragm61, an error is included in the deformation of the diaphragm61due to the pressure difference, and the accuracy with which the pressure is measured decreases.

FIG. 3is a flowchart illustrating a method of adjusting the pressure gauge60according to an embodiment. The method of adjusting the pressure gauge60according to the embodiment is executed, for example, after the cleaning process. The cleaning process is performed, for example, each time when a film forming process is performed multiple times.

As illustrated inFIG. 3, the method of adjusting the pressure gauge60according to the embodiment includes steps S31to S34.

In step S31, the controller80executes the film forming process in the processing container10. In an embodiment, the controller80executes the film forming process in a state in which the wafers W are not present in the processing container10or dummy wafers are accommodated in the processing container10. In step S31, some of the film forming gas supplied into the processing container10during the film forming process flows into the measurement pressure chamber63of the pressure gauge60, and a film is deposited on the surface of the diaphragm61. The film forming process in step S31is performed using, for example, the same gas as the film forming gas used in the film forming process in which the product wafers are accommodated in the processing container10. Further, the film forming process in step S31is preferably executed under, for example, the same conditions as the film forming process executed while accommodating the product wafers in the processing container10. The film forming process may be, for example, a process of forming a silicon oxide film by alternately supplying an aminosilane gas and an oxidizing gas into the processing container10.

In step S32, the controller80adjusts the zero point of the pressure gauge60. In an embodiment, the controller80controls the exhaust part40to evacuate the inside of the processing container10to the highest reachable vacuum degree. Subsequently, the controller80detects the pressure in the processing container10evacuated to the highest reachable vacuum degree (hereinafter, referred to as an “ultimate pressure”) using the pressure gauge60. Subsequently, the controller80adjusts the zero point of the pressure gauge60such that the ultimate pressure detected by the pressure gauge60becomes a target pressure. The target pressure may be, for example, the ultimate pressure detected by the pressure gauge60when the difference between the ultimate pressures detected by the pressure gauge60before and after the film forming process is within a predetermined range. In addition, the target pressure may be, for example, the ultimate pressure detected by the pressure gauge60in a state in which a film having a predetermined thickness or more is deposited on the surface of the diaphragm61of the pressure gauge60. The target pressure may be, for example, the ultimate pressure detected by the pressure gauge60immediately before the cleaning process for removing, for example, the film deposited in the processing container10.

In step S33, the controller80executes the film forming process in the processing container10. The film forming process in step S33may be the same as the film forming process in step S31.

In step S34, the controller80determines whether there is a zero-point shift in the pressure gauge60. In an embodiment, the controller80controls the exhaust part40to evacuate the inside of the processing container10to the highest reachable vacuum degree. Subsequently, the controller80detects the pressure in the processing container10evacuated to the highest reachable vacuum degree using the pressure gauge60. Subsequently, the controller80determines whether or not the ultimate pressure detected by the pressure gauge60has reached a target range. When it is determined that the ultimate pressure detected by the pressure gauge60has reached the target range, the controller80determines that there is no zero-point shift in the pressure gauge60, and finishes the process. Meanwhile, when it is determined that the ultimate pressure detected by the pressure gauge60has not reached the target range, the controller80determines that there is a zero-point shift in the pressure gauge60, and returns the process to step S32.

Next, a specific example of the method of adjusting the pressure gauge60according to the embodiment will be described.FIG. 4is a view illustrating a specific example of the method of adjusting the pressure gauge60according to the embodiment. InFIG. 4, the target pressure PT is indicated by a solid line, and the upper limit value PHand the lower limit value PLof the target range are indicated by broken lines. In the example ofFIG. 4, the target pressure PT is the ultimate pressure after the film forming process executed immediately before the cleaning process. DIPAS was used as the film forming gas during the film forming process, O2plasma was used as the oxidizing gas, and HF gas was used as the cleaning gas during the cleaning process.

As illustrated inFIG. 4, the ultimate pressure after the film forming process1(step S31) performed after the cleaning process is higher than the upper limit PHof the target range. The ultimate pressure after the zero-point adjustment (step S32) executed after the film forming process1(step S31) is the target pressure PT, and the ultimate pressure after the film forming process2(step S33) executed after the zero-point adjustment (step S32) has a value lower than the lower limit value PLof the target range. Therefore, it is determined in step S34that there is a zero-point shift, and the zero-point adjustment (step S32) is performed again.

The ultimate pressure after the second zero-point adjustment (step S32) is the target pressure PT, and the ultimate pressure after the film forming process3(step S33) executed after the zero-point adjustment (step S32) has a value higher than the upper limit value PHof the target range. Therefore, it is determined in step S34that there is a zero-point shift, and the zero-point adjustment (step S32) is performed again.

The ultimate pressure after the third zero-point adjustment (step S32) is the target pressure Pr, and the ultimate pressure after the film forming process4(step S33) executed after the zero-point adjustment (step S32) has a value that falls within the target range. Therefore, it is determined in step S34that there is no zero-point shift, and the process is finished.

As described above, in an embodiment, the controller80repeats a cycle including the step of adjusting the zero point of the pressure gauge60and the step of executing the film forming process in the processing container10until the ultimate pressure after the step of executing the film forming process reaches the target range. By automating the zero-point adjustment of the pressure gauge60in this way, it is possible to reduce downtime accompanying with the adjustment of the pressure gauge60. This improves productivity. Further, it is possible to reduce a difference in devices that may occur when an operator manually adjusts the zero point of the pressure gauge60.

[System Including Film Forming Apparatus]

FIG. 5is a view illustrating an exemplary system including the film forming apparatus1. As illustrated inFIG. 5, the system includes three film forming apparatuses1, a group management controller2, and a terminal3.

Each film forming apparatus1has a pressure gauge60and a controller80. Each film forming apparatus1is communicatively connected to the group management controller2via a communication line in a semiconductor factory. Although three film forming apparatuses1are illustrated inFIG. 5, the number of film forming apparatuses1is not particularly limited.

The group management controller2is an example of a control device, and may be, for example, a computer. The group management controller2is communicatively connected to the terminal3via a communication line of a semiconductor factory. The group management controller2acquires log data when the film forming apparatus1executes a process, and stores the acquired log data. The log data includes a detection value of the pressure gauge60. Further, the group management controller2may be configured to execute the method of adjusting the pressure gauge60according to the embodiment together with or in place of the controller80described above.

The communication line is separated from, for example, an external network. However, the communication line may be communicatively connected to the external network.

It should be understood that the embodiments disclosed herein are illustrative and are not limiting in all aspects. The above-described embodiments may be omitted, replaced, or modified in various forms without departing from the scope and spirit of the appended claims.

In the embodiments described above, the case in which the processing container is a container having a double-tube structure has been described, but the present disclosure is not limited thereto. For example, the processing container may be a container having a single-tube structure.

In the embodiments described above, the case in which the processing apparatus is an apparatus that supplies gas from the gas nozzle arranged in the longitudinal direction of the processing container and exhausts the gas from the slit arranged to face the gas nozzles has been described, but the present disclosure is not limited thereto. For example, the processing apparatus may be an apparatus that supplies gas from a gas nozzle arranged along the longitudinal direction of the wafer boat and exhausts the gas from an exhaust port arranged above the wafer boat. In addition, for example, the processing apparatus may be an apparatus that supplies a processing gas from a gas nozzle arranged below the processing container and exhausts the gas from an exhaust port arranged above the processing container.

In the embodiments described above, the case in which the heater is installed around the processing container has been described, but the present disclosure is not limited thereto. For example, the heater may not be provided.

In the embodiments described above, the case in which the processing apparatus is an apparatus that does not use plasma has been described, but the present disclosure is not limited thereto. For example, the processing apparatus may be an apparatus that uses plasma such as capacitively coupled plasma (CCP).

In the embodiments described above, the case in which the processing apparatus is a batch-type apparatus that performs a process on a plurality of wafers at one time has been described, but the present disclosure is not limited thereto. For example, the processing apparatus may be a single-wafer processing apparatus that processes wafers one by one. Further, for example, the processing apparatus may be a semi-batch-type apparatus that causes a plurality of wafers placed on a rotary table within a processing container to revolve such that the wafers sequentially pass through an area in which a first gas is supplied and an area in which a second gas is supplied, thereby processing the wafers.

In the embodiments described above, the case in which the substrate is a semiconductor wafer has been described, but the present disclosure is not limited thereto. For example, the substrate may be a large substrate for a flat panel display (FPD), a substrate for an organic EL panel, or a substrate for a solar cell.

According to the present disclosure, it is possible to automatically execute zero-point adjustment of a pressure gauge.