FILLING METHOD AND FILM FORMING APPARATUS

A filling method according to one aspect of the present disclosure is a method of filling a recess formed in a surface of a substrate with a metal oxide film. The method includes forming the metal oxide film by supplying a metallic raw material gas and an oxidant to the recess, and etching a part of the metal oxide film by supplying an etching gas including at least one selected from a group including SOCl2 and (COCl)2 to the metal oxide film.

TECHNICAL FIELD

The present disclosure relates to a filling method and a film forming apparatus.

BACKGROUND

A technique for forming an aluminum-containing oxide thin film by atomic layer deposition using, as a raw material, an aluminum-containing composition containing trimethylaluminum and dimethylaluminum hydride and an oxygen-containing compound containing oxygen atoms is known (see Patent Document 1, for example). Further, a technique for removing the Al2O3film from the reactor surface by reacting an Al2O3film coated over a surface of a reactor with BCl3and COCl2to produce a volatile product and by removing the volatile product from the reactor, is known (see Patent Document 2, for example).

PRIOR ART DOCUMENTS

Patent Documents

The present disclosure provides a technique capable of forming a high-quality metal oxide film with good filling characteristics.

SUMMARY

A filling method according to one aspect of the present disclosure is a method of filling a recess formed in a surface of a substrate with a metal oxide film, the method including forming the metal oxide film by supplying a metallic raw material gas and an oxidant to the recess, and etching a part of the metal oxide film by supplying an etching gas including at least one selected from a group including SOCl2and (COCl)2to the metal oxide film.

According to the present disclosure, it is possible to form a high-quality metal oxide film with good filling characteristics.

DETAILED DESCRIPTION

Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. In all the accompanying drawings, the same or corresponding members or components will be denoted by the same or corresponding reference numerals, and redundant descriptions thereof will be omitted.

There is a need to fill a recess with a high-quality metal oxide film. The high-quality metal oxide film is formed by a high-temperature process at, for example, 500 degrees C. or higher. However, the high-temperature process tends to deteriorate a step coverage to the recess, and degrades filling characteristics.

Therefore, the present inventors have extensively studied a method of forming a high-quality metal oxide film with good filling characteristics. As a result, it was found that a high-quality metal oxide film having good filling characteristics can be formed by a filling method including a process of forming a metal oxide film and a process of etching a part of the metal oxide film by thionyl chloride [SOCl2] and/or oxalyl chloride [(COCl)2]. Details will be described below.

An example of a filling method of an embodiment will be described with reference toFIGS.1A to1C. The filling method of the embodiment is a method of filling a recess formed in a surface of a substrate with an aluminum oxide film (Al2O3film) by repeating a cycle including a film forming process and an etching process.

In the film forming process, as illustrated inFIG.1A, an Al2O3film120is formed by supplying an Al raw material gas and an oxidant to a recess110formed in a surface of a substrate100. The substrate100may be, for example, a wafer such as a silicon wafer. The recess110may be, for example, a trench or a via. For example, the film forming process forms the Al2O3film120so as not to block an opening of the recess110. In the film forming process, the Al2O3film120may be formed by atomic layer deposition (ALD). That is, in the film forming process, the Al2O3film120is preferably formed in the recess110by repeating the supply of the Al raw material gas, the supply of a purge gas, the supply of the oxidant, and the supply of the purge gas in this order. Thus, the Al2O3film120may be formed conformally in the recess110, so that voids, seams, and the like are less likely to occur when the Al2O3film120is filled in the recess110. Further, in the film forming process, the substrate may be heated to a high temperature of 500 degrees C. or higher. Thus, the high-quality Al2O3film120may be formed. In film formation by ALD which is performed while the substrate is heated to a temperature of 500 degrees C. or higher, for example, a halogen-containing Al raw material gas such as AlCl3, (CH3)3Al2Cl3, EADC[(CH3CH2)AlCl2], DEAC[(CH3CH2)2AlCl], EASC[(CH3CH2)1.5AlCl1.5], DMAC[(CH3)2AlCl] may be used as the Al raw material gas. For example, O2gas, O3gas), H2O gas, H2O2gas, a mixed gas of H2and O2, isopropyl alcohol (IPA) gas may be used as the oxidant. An inert gas such as N2gas or Ar gas may be used as the purge gas.

For example, when DMAC[(CH3)2AlCl] is used as the Al raw material gas and the H2O gas is used as an oxidizing gas, the Al2O3film120is formed by a chemical reaction represented by the following formula (A).

In the etching process, as illustrated inFIG.1B, a part of the Al2O3film120is etched by supplying an etching gas including at least one selected from a group including thionyl chloride [SOCl2] and oxalyl chloride [(COCl)2] to the Al2O3film120. For example, in the etching process, the Al2O3film120is selectively etched so as to widen the opening of the recess110. In the etching process, the substrate may be heated to the same temperature as or substantially the same temperature as the temperature in the film forming process, for example, to a high temperature of 500 degrees C. or higher. The substantially same temperature means a temperature within a range of ±5% with respect to the same temperature. SOCl2and (COCl)2have an etching rate of 1 nm/min to 100 nm/min for the Al2O3film120at a temperature of 500 degrees C. or higher. Therefore, by using SOCl2and (COCl)2as the etching gas, a part of the Al2O3film120may be etched with good controllability without changing the processing temperatures of the film forming process and the etching process. In this way, in the etching process, the etching gas having an etching rate of 1 nm/min and 100 nm/min for the Al2O3film120at a temperature of 500 degrees C. or higher is preferably used. Further, more preferably, the etching gas having an etching rate of 5 nm/min to 50 nm/min is used. Further, SOCl2and (COCl)2have a low etching rate for the Al2O3film120at a temperature less than 500 degrees C. Therefore, the film deposited on an inner wall of a processing container, which has a lower temperature than the substrate, is hardly etched, so that generation of particles due to peeling of the deposited film from the inner wall of the processing container can be prevented. For example, when a SOCl2gas is used as the etching gas, a part of the Al2O3film120may be etched by a chemical reaction represented by the following formula (B).

According to the filling method of the embodiment described above, by repeating a cycle including the film forming process and the etching process, as illustrated inFIG.1C, the Al2O3film120is filled in the recess110on the recess110formed in the surface of the substrate100. Then, in the etching process, the etching gas including at least one selected from a group including SOCl2and (COCl)2is supplied to the Al2O3film120to etch a part of the Al2O3film. Thus, a high-quality metal oxide film with good filling characteristics can be formed.

In the above, a case where the Al2O3film120is filled in the recess110only having a vertical holes has been described with reference toFIGS.1A to1C, but the present disclosure is not limited thereto. For example, as illustrated inFIGS.2A to2C, a filling method of the embodiment may also be applied to a case where a recess210formed in a surface of a substrate200includes a vertical hole211extending in the thickness direction of the substrate200and a horizontal hole212extending in a direction parallel to the surface of the substrate200from a sidewall211aof the vertical hole211.

Specifically, in the film forming process, as illustrated inFIG.2A, an Al2O3film220is formed by supplying an Al raw material gas and an oxidant to the recess210formed in the surface of the substrate200. In the etching process, as illustrated inFIG.2B, a part of the Al2O3film220is etched by supplying an etching gas including at least one selected from a group including thionyl chloride [SOCl2] and oxalyl chloride [(COCl)2] to the Al2O3film220. Then, by repeating a cycle including the film forming process and the etching process, as illustrated inFIG.2C, the Al2O3film220can be filled in the recess210.

An example of a film forming apparatus for performing the filling method of the embodiment will be described with reference toFIG.3. The film forming apparatus of the embodiment is configured as an apparatus capable of performing film formation by an atomic layer deposition (ALD) method and film formation by a chemical vapor deposition (CVD) method.

The film forming apparatus includes a processing container1, a stage2, a shower head3, an exhauster4, a gas supplier5, a controller6, and the like.

The processing container1is formed of a metal such as aluminum and has a substantially cylindrical shape. The processing container1accommodates a substrate W therein. The substrate W may be, for example, a semiconductor wafer. A loading/unloading port11for loading or unloading substrate W is formed in a sidewall of the processing container1. The loading/unloading port11is opened and closed by a gate valve12. An annular exhaust duct13having a rectangular cross section is provided on a main body of the processing container1. A slit13ais formed in the exhaust duct13along an inner peripheral surface thereof. An exhaust port13bis formed in an outer wall of the exhaust duct13. A ceiling wall14is provided on an upper surface of the exhaust duct13so as to close an upper opening of the processing container1. A space between the exhaust duct13and the ceiling wall14is airtightly sealed with a seal ring15.

The stage2horizontally supports the substrate W inside the processing container1. The stage2takes the form of a disk larger than the substrate W, and is formed of a ceramic material such as an aluminum nitride (AlN) or a metallic material such as an aluminum or nickel alloy. A heater21for heating the substrate W is embedded inside the stage2. The heater21generates heat upon receiving power from a heater power supply (not illustrated). Then, the substrate W is controlled to a predetermined temperature by controlling the output of the heater21in response to a temperature signal of a thermocouple (not illustrated) provided near an upper surface of the stage2. A cover member22formed of ceramics such as alumina is provided on the stage2so as to cover an outer peripheral region of the upper surface and a side surface of the stage2.

The stage2is supported by a support member23. The support member23passes through a hole formed in a bottom wall of the processing container1from the center of a bottom surface of the stage2to extend downward of the processing container1, and is connected at a lower end thereof to a lifting mechanism24. The stage2is lifted by the lifting mechanism24between a processing position illustrated inFIG.3and a transfer position thereunder where the substrate W may be transferred as illustrated by the two-dotted dash line. A flange25is attached to the support member23at a position below the processing container1. A bellows26is provided between a bottom surface of the processing container1and the flange25. The bellows26separates the atmosphere inside the processing container1from outside air, and is adapted to expand and contract according to a lifting operation of the stage2.

Three (only two of which are illustrated) wafer support pins27are provided near the bottom surface of the processing container1so as to protrude upward from a lifting plate27a. The wafer support pins27are lifted by a lifting mechanism28provided below the processing container1via a lifting plate27a. The wafer support pins27are inserted into through-holes2aprovided in the stage2which is at the transfer position, and are capable of protruding and retracting to and from the upper surface of the stage2. The wafer W is transferred between a transfer robot (not illustrated) and the stage2by lifting/lowering the wafer support pins27.

The shower head3supplies a processing gas in the form of a shower into the processing container1. The shower head3is formed of, for example, a metallic material, and is arranged to face the stage2. The shower head3has substantially the same diameter as the stage2. The shower head3includes a main body31and a shower plate32. The main body31is fixed to a lower surface of the ceiling wall14. The shower plate32is connected below the main body31. A gas diffusion space33is defined between the main body31and the shower plate32. A gas introduction hole36is provided in the gas diffusion space33so as to penetrate the center of the ceiling wall14and the main body31. An annular protrusion34is formed on a peripheral edge portion of the shower plate32to protrude downward. A plurality of gas discharge holes35is formed in an inner flat surface of the annular protrusion34of the shower plate32.

In a state where the stage2is moved to the processing position, a processing space37is created between the stage2and the shower plate32, and an upper surface of the cover member22and the annular protrusion34become closer to each other to create an annular gap38.

The exhauster4exhausts the interior of the processing container1. The exhauster4includes an exhaust pipe41and an exhaust mechanism42. The exhaust pipe41is connected to the exhaust port13b. The exhaust mechanism42is connected to the exhaust pipe41, and includes a vacuum pump, a pressure control valve, and the like. The exhaust mechanism42exhausts the gas inside the processing container1through the exhaust duct13and the exhaust pipe41.

The gas supplier5supplies various gases to the shower head3. The gas supplier5includes a gas source51and a gas line52. The gas source51includes, for example, a source for various processing gases, a mass flow controller, and a valve (none of which are illustrated). The various processing gases include the Al raw material gas, the oxidant, and the etching gas used in the filling method of the above-described embodiment. These various gases are introduced into the gas diffusion space33from the gas source51through the gas line52and the gas introduction hole36.

The controller6controls each part of the film forming apparatus, thereby performing, for example, the above-described filling method. The controller6may be, for example, a computer. Further, a program of a computer that operates each part of the film forming apparatus is stored in a storage medium. The storage medium may be, for example, a flexible disk, a compact disk, a hard disk, a flash memory, a DVD, or the like.

Next, a case of performing the filling method of the embodiment illustrated inFIGS.1A to1C and2A to2Cwill be described as an example of an operation of the film forming apparatus.

First, the controller6opens the gate valve12, transfers the substrate W having a recess in a surface thereof into the processing container1by the transfer mechanism (not illustrated), and places the substrate W on the stage2. The substrate W is placed horizontally with the surface facing upward. The controller6closes the gate valve12after retracting the transfer mechanism from the interior of the processing container1. Next, the controller6heats the substrate W to a predetermined temperature by the heater21of the stage2, and adjusts the interior of the processing container1to a predetermined pressure by the exhaust mechanism42.

Next, the controller6controls each part of the film forming apparatus to perform the filling method of the above-described embodiment. That is, the controller6controls the exhauster4, the gas supplier5, and the like to repeat a cycle including the film forming process and the etching process, thereby filling the recess with the Al2O3film.

After the Al2O3film is filled in the recess formed in the surface of the substrate W, the controller6unloads the substrate W from the processing container1in the reverse order of loading the substrate W into the processing container1.

In addition, in the above embodiment, the Al raw material gas is an example of a metallic raw material gas, and the Al2O3film is an example of a metal oxide film.

The embodiments disclosed herein should be considered to be exemplary and not limitative in all respects. The above embodiments may be omitted, replaced or modified in various embodiments without departing from the scope of the appended claims and their gist.

In the above embodiment, a case of forming the Al2O3film as the metal oxide film has been described, but the present disclosure is not limited thereto. For example, the metal oxide film may be a high-k film such as HfO2film or ZrO2film. For example, in a case of forming the HfO2film, for example, HfCl4may be used as the metallic raw material gas. Further, for example, in a case of forming the ZrO2film, a ZrCl4gas may be used as the metallic raw material gas. SOCl2and (COCl)2have an etching rate of 1 nm/min to 100 nm/min for the HfO2film and the ZrO2film at a temperature of 500 degrees C. or higher. Therefore, by using SOCl2and (COCl)2as the etching gas, a part of the HfO2film and the ZrO2film may be etched with good controllability without changing the processing temperatures of the film forming process and the etching process, as in the case of the Al2O3film.

In the above embodiments, a case of using thionyl chloride [SOCl2] and oxalyl chloride [(COCl)2] as the etching gas has been described, but the present disclosure is not limited thereto. For example, a Cl2gas, a BCl3gas, or a ClF3gas may be used as the etching gas.

In the above embodiments, a case where the film forming apparatus is a single wafer type apparatus that processes substrates one by one has been described, but the present disclosure is not limited thereto. For example, the film forming apparatus may be a batch type apparatus that processes on a plurality of substrates at once. Further, for example, the film forming apparatus may be a semi-batch type apparatus that revolves a plurality of substrates disposed on a rotation table inside a processing container by the rotation table, thereby sequentially passing the substrates through a region to which a first gas is supplied and a region to which a second gas is supplied to perform a processing on the substrates.

In the above embodiment, a case where the film forming apparatus is an apparatus having no plasma generator has been described, but the present disclosure is not limited thereto. For example, the film forming apparatus may be an apparatus having a plasma generator.

This international application claims priority to Japanese Patent Application No. 2020-172144 filed on Oct. 12, 2020, which is incorporated herein by reference in its entirety.

EXPLANATION OF REFERENCE NUMERALS