Substrate support and substrate processing apparatus

Described herein is a technique capable of preventing a susceptor made of quartz from being damaged by contacting a reflector deformed by thermal expansion. A substrate support according to the technique may include an upper susceptor made of quartz; a lower susceptor made of quartz; and a reflector reflecting heat and made of a metal in a planar shape. A lower surface of the upper susceptor is bonded with an upper surface of the lower susceptor such that the reflector is interposed therebetween, a first recess accommodating the reflector is provided at the upper surface of the lower susceptor, and a portion of the lower surface of the upper susceptor facing the first recess is roughened.

TECHNICAL FIELD

The present disclosure relates to a substrate support and a substrate processing apparatus.

BACKGROUND

In a manufacturing process of a semiconductor device, for example, a wafer (hereinafter, also referred to as a “substrate”) is heated and a desired process is performed on the heated wafer by a substrate processing apparatus. In order to heat the wafer, for example, a heater provided in a substrate support (susceptor) of the substrate processing apparatus is used. However, when the wafer is heated by the heater provided in the susceptor, the temperature of a surface of the susceptor on which wafer is placed may be unstable. Thus, the wafer placed on the susceptor may not be uniformly heated or the heat radiated from the heater leaks to an outer periphery or a lower side of the susceptor. Therefore, heating of the wafer may not be performed efficiently.

In order to address the above-described problems, for example, the semiconductor manufacturing apparatus and the susceptor may include a reflector configured to reflect the radiant heat from the heater. The reflector is disposed under the heater. It is possible to reduce power consumptions of the heater by the reflector.

However, when the susceptor includes the reflector under the heater, the reflector deformed by thermal expansion may contact the susceptor made of quartz. Thus, the susceptor may be damaged by the adhesion between the reflector and the susceptor.

SUMMARY

Described herein is a technique capable of preventing the susceptor made of quartz from being damaged by contacting the reflector deformed by thermal expansion.

According to one aspect of the technique described herein, there is provided a substrate support including: an upper susceptor made of quartz; a lower susceptor made of quartz; and a reflector reflecting heat and made of a metal in a planar shape, wherein a lower surface of the upper susceptor is bonded with an upper surface of the lower susceptor such that the reflector is interposed therebetween, a first recess accommodating the reflector is provided at the upper surface of the lower susceptor, and a portion of the lower surface of the upper susceptor facing the first recess is roughened.

DETAILED DESCRIPTION

Hereinafter, a preferred embodiment (first embodiment) will be described with reference to the drawings.

(1) Configuration of Substrate Processing Apparatus

Hereafter, a substrate processing apparatus according to the first embodiment will be described. The substrate processing apparatus is an example of a semiconductor manufacturing apparatus used for manufacturing a semiconductor device.

In the following description, as an example of the substrate processing apparatus according to the first embodiment, an apparatus configured to perform a process such as a film-forming process to a substrate will be described.FIG. 1schematically illustrates a vertical cross-section of a substrate processing apparatus100according to the first embodiment described herein.

The substrate processing apparatus100includes a process furnace202where a wafer200is processed by plasma. The process furnace202includes a process vessel203. A process chamber201is defined by the process vessel203. The process vessel203includes a dome-shaped upper vessel210serving as a first vessel and a bowl-shaped lower vessel211serving as a second vessel. By covering the lower vessel211with the upper vessel210, the process chamber201is defined. The upper vessel210is made of, for example, a non-metallic material such as aluminum oxide (Al2O3) and quartz (SiO2), and the lower vessel211is made of, for example, aluminum (Al).

A gate valve244is provided on a lower side wall of the lower vessel211. While the gate valve244is open, the wafer200can be loaded into the process chamber201through a substrate loading/unloading port245using a transfer mechanism (not shown) or unloaded out of the process chamber201through the substrate loading/unloading port245using the transfer mechanism (not shown). While the gate valve244is closed, the gate valve244maintains the process chamber201airtight.

As described later, the process chamber201includes a plasma generation space201A that a resonance coil212described later is provided therearound and a substrate processing space201B where the wafer200is processed. The substrate processing space201B communicates with the plasma generation space201A. The plasma generation space201A refers to a space where the plasma is generated, for example, a space above a lower end of the resonance coil212(indicated by a dashed line inFIG. 1) in the process chamber201. The substrate processing space201B refers to a space where the wafer200is processed by plasma, for example, a space below the lower end of the resonance coil212.

A susceptor217serving as a substrate support (substrate placement part) is provided at a center of a bottom portion of the process chamber201. The wafer200can be placed on the susceptor217. The susceptor217includes a heater218and a reflector219serving as a reflection part. The susceptor217is made of a non-metallic material. According to the first embodiment, the susceptor217is made of quartz. A susceptor cover (not shown) configured to uniformly transfer the heat from the susceptor217(that is, the heater218) to the wafer200may be provided between the susceptor217and the wafer200. The susceptor cover is made of a non-metallic material such as aluminum nitride (AlN), ceramics, quartz and silicon carbide (SiC).

The heater218serving as a heating mechanism is integrally embedded in the susceptor217. The heater218is constituted by a resistance heating type heating element (also referred to as a “heater element”). For example, the heater element is made of a material such as SiC, carbon, nickel and glassy carbon. Electric power is supplied from a heater power supply275to the heater218via a feed line. When the electric power is supplied, the heater218is configured to heat the wafer200such that a surface temperature of the wafer200may range, for example, from 25° C. to 700° C.

The reflector219in a planar shape is provided in the susceptor217under the heater218. The reflector219reflects radiant heat radiated from the heater218toward the wafer200. As a result, the wafer200is efficiently heated. The reflector219is made of a material having high reflectance in order to efficiently reflect the radiant heat radiated from the heater218. For the reflector219, such material that has a constant reflectance and is chemically stable at high temperature is needed. Thus, for example, metal with high melting point such as molybdenum (Mo), tungsten (W), nickel (Ni), platinum (Pt), palladium (Pd), platinum-rhodium alloy and gold (Au) is used for the reflector219. In addition to above-described metal, a material such as carbon and SiC may be used for the reflector219. However, the first embodiment is preferably applied when a material with a high thermal expansion coefficient or having the property of adhering to quartz under high temperature (for example, the above-described metal) is used for the reflector219.

A susceptor elevating mechanism268configured to elevate and lower the susceptor217is provided at the susceptor217. Wafer lift pins266are provided at the bottom of the lower vessel211. Holes220wherethrough the wafer lift pins266penetrate are provided in the susceptor217corresponding to the wafer lift pins266. The holes220and the wafer lift pins266are provided at least three positions facing each other. When the susceptor217is lowered by the susceptor elevating mechanism268, the wafer lift pins266pass through the holes220without contacting the susceptor217.

The susceptor217, the heater218and the reflector219of the first embodiment will be described later in detail.

Gas Supply System

A shower head236is provided above the process chamber201, that is, on an upper portion of the upper vessel210. The shower head236includes a cap-shaped lid233, a gas inlet port234, a buffer chamber237, an opening portion238, a shield plate240and a gas outlet port239. The shower head236is configured to supply a reactive gas into the process chamber201. The buffer chamber237functions as a dispersion space for dispersing the reactive gas supplied through the gas inlet port234.

A downstream end of a oxygen-containing gas supply pipe232A configured to supply an oxygen (O2) gas serving as a oxygen-containing gas, a downstream end of a hydrogen-containing supply pipe232B configured to supply a hydrogen (H2) gas serving as a hydrogen-containing gas and a downstream end of an inert gas supply pipe232C configured to supply an argon (Ar) gas serving as an inert gas are connected to join the gas inlet port234. An oxygen gas supply source250A, a mass flow controller (MFC)252A serving as a flow rate controller (flow rate control mechanism) and a valve253A serving as an opening/closing valve are provided in order from the upstream side to the downstream side of the oxygen-containing gas supply pipe232A. A hydrogen gas supply source250B, a mass flow controller (MFC)252B serving as a flow rate controller (flow rate control mechanism) and a valve253B serving as an opening/closing valve are provided in order from the upstream side to the downstream side of the hydrogen-containing supply pipe232B. An argon gas supply source250C, a mass flow controller (MFC)252C serving as a flow rate controller (flow rate control mechanism) and a valve253C serving as an opening/closing valve are provided in order from the upstream side to the downstream side of the inert gas supply pipe232C. A valve243A is provided on the downstream side whereat the oxygen-containing gas supply pipe232A joins the hydrogen-containing supply pipe232B and the inert gas supply pipe232C. That is, the valve243A is provided at a gas supply pipe232shown inFIG. 1. The valve243A is connected to the upstream end of the gas inlet port234. Reactive gases such as the oxygen-containing gas, the hydrogen-containing gas and the inert gas can be supplied into the process chamber201via the gas supply pipes232A,232B,232C and232by opening and closing the valves253A,253B,253C and243A while adjusting the flow rates of the respective gases by the MFCs252A,252B and252C.

Exhaust System

A gas exhaust port235is provided on the side wall of the lower vessel211. The gas such as the reactive gases is exhausted from the process chamber201through the gas exhaust port235. An upstream end of a gas exhaust pipe231is connected to the gas exhaust port235. An APC (Automatic Pressure Controller)242serving as a pressure controller (pressure adjusting mechanism), a valve243B serving as an opening/closing valve and a vacuum pump246serving as a vacuum exhaust device are provided in order from the upstream side to the downstream side of the gas exhaust pipe231.

Plasma Generator

A helical resonance coil212is provided so as to surround the process chamber201at the outer periphery of the process chamber201, that is, on the outer side of the side wall of the upper vessel210. An RF sensor272, a high frequency power supply273and a frequency matching mechanism274are connected to the resonance coil212. The high frequency power supply273supplies a high frequency power to the resonance coil212. The RF sensor272is provided at an output side of the high frequency power supply273. The RF sensor272monitors information of the traveling wave or reflected wave of the supplied high frequency power. The frequency matching mechanism274controls the high frequency power supply273so as to minimize the reflected wave based on information of the reflected wave monitored by the RF sensor272.

When the high frequency power is applied from the high frequency power supply273to the resonance coil212, a high frequency electric field is generated in the plasma generation space201A by the resonance coil212. The gas such as the oxygen gas and the hydrogen gas supplied into the process chamber201is excited by the high frequency electric field. The excited gas in the plasma state generates a reactive species such as active species and ions containing the gas element (that is, oxygen or hydrogen).

Controller

A controller221is configured to control the APC242, the valve243B and the vacuum pump246via a signal line A, the susceptor elevating mechanism268via a signal line B, the heater218via a signal line C, the gate valve244via a signal line D, the RF sensor272, the high frequency power supply273and the frequency matching mechanism274via a signal line E, and MFCs252A,252B and252C and the valves253A,253B,253C and243A via a signal line F.

The controller221is embodied by a computer operated by a program for controlling each of the above-described components, and the program may be stored in a computer-readable recording medium. For example, the recording medium is electrically connected to the substrate processing apparatus100, and the controller221of the substrate processing apparatus100can read the program from the recording medium and control the above-described components.

Hereinafter, a substrate processing according to the first embodiment will be described. The substrate processing according to the first embodiment is performed by the above-described substrate processing apparatus100, as one of the manufacturing processes of the semiconductor device such as a flash memory. In the following description, the components of the substrate processing apparatus100are controlled by the controller221.

Substrate Loading Step

First, the wafer200is loaded into the process chamber201. Specifically, the susceptor217is lowered to a position for transferring the wafer200(“wafer transfer position”) by the susceptor elevating mechanism268. The wafer lift pins266penetrate the holes220of the susceptor217. As a result, the wafer lift pins266protrude from the surface of the susceptor217by a predetermined height.

Next, the gate valve244is opened and the wafer200is loaded into the process chamber201from a vacuum transfer chamber (not shown) adjacent to the process chamber201by the transfer mechanism (not shown). As a result, the wafer200is horizontally supported by the wafer lift pins266protruding from the surface of the susceptor217. After the wafer200is transferred into the process chamber201, the transfer mechanism is retracted to the outside of the process chamber201, and the gate valve244is closed to seal the process chamber201. Thereafter, the susceptor elevating mechanism268elevates the susceptor217until the wafer200is at a predetermined position between the lower end of the resonance coil212and an upper end245A of the substrate loading/unloading port245. As a result, the wafer200is placed on an upper surface of the susceptor217and supported by the susceptor217.

Temperature Elevating and Vacuum Exhaust Step

Next, the temperature of the wafer200loaded into the process chamber201is elevated. The heater218embedded in the susceptor217is heated in advance. By placing the wafer200on the susceptor217where the heater218is embedded, the wafer200is heated to a predetermined temperature. For example, the predetermined temperature of the wafer200ranges from 150° C. to 650° C. While the wafer200is being heated, the vacuum pump246vacuum-exhausts the inside of the process chamber201through the gas exhaust port235such that an inner pressure of the process chamber201is at a predetermined pressure. For example, the predetermined pressure ranges from 0.1 Pa to 1,000 Pa. The vacuum pump246vacuum-exhausts the inside of the process chamber201at least until a substrate unloading step described later is completed.

Reactive Gas Supply Step

Next, the oxygen gas serving as the reactive gas is supplied. Specifically, the valve253A is opened to supply of the oxygen gas into the process chamber201via the buffer chamber237while the flow rate of the oxygen gas is adjusted by the MFC252A. In the reactive gas supply step, for example, the amount of the oxygen gas supplied into the process chamber201is set within a range from 100 sccm to 1,000 sccm. The inside of the process chamber201is exhausted by adjusting the opening degree of the APC242such that the inner pressure of the process chamber201is at a predetermined pressure ranging from 1 Pa to 1,000 Pa. The oxygen gas is continuously supplied while the inside of the process chamber201is properly exhausted until a plasma process step described later is completed.

Plasma Process Step

After the inner pressure of the process chamber201is stabilized, the high frequency power is applied to the resonance coil212via the frequency matching mechanism274from the high frequency power supply273.

As a result, a high frequency electric field is generated in the plasma generation space201A, and a donut-shaped induction plasma is excited at a height corresponding to an electric midpoint of the resonance coil212in the plasma generation space201A. The oxygen gas in plasma state is dissociated to generate a reactive species such as an oxygen active species (radicals) including oxygen (O) and ions. The oxygen radicals and ions are uniformly supplied to the surface of the wafer200placed on the susceptor217in the substrate processing space201B. The oxygen radicals and ions react with a silicon film on the wafer200, and the silicon film is modified to a silicon oxide film having high step coverage.

After a predetermined process time elapses, for example, after 10 second to 300 seconds elapse, the output of the electrical power from the high frequency power supply273is stopped to stop the plasma discharge in the process chamber201. The valve253A is closed to stop the supply of the oxygen gas into the process chamber201. Thereby, the plasma process step is completed.

Vacuum Exhaust Step

After the predetermined processing time elapses and the supply of the oxygen gas is stopped, in the vacuum exhaust step, the inside of the process chamber201is vacuum-exhausted through the gas exhaust port235. As a result, the gas such as an exhaust gas produced by the reaction of the oxygen gas in the process chamber201and the oxygen gas is exhausted to the outside of the process chamber201. Thereafter, the opening degree of the APC242is adjusted such that the inner pressure of the process chamber201is adjusted to the same pressure as that of the vacuum transfer chamber (not shown) where the wafer200is transferred in a substrate unloading step described below. For example, the process chamber201is adjusted to 100 Pa.

Substrate Unloading Step

After the inner pressure of the process chamber201reaches a predetermined pressure, the susceptor217is lowered to the wafer transfer position described above until the wafer200is supported by the wafer lift pins266. Then, the gate valve244is opened and the wafer200is unloaded from the process chamber201to the outside of the process chamber201by the transfer mechanism (not shown). Thereby, the substrate processing according to the first embodiment is completed.

According to the first embodiment, an oxide film (i.e., the silicon oxide film) is formed on the silicon film on the wafer200by supplying the oxygen gas into the process chamber201and exciting the oxygen gas by plasma to oxidize the silicon film. However, in the first embodiment, the oxygen gas and the hydrogen gas may be supplied into the process chamber201together as the gas excited by plasma. When the first embodiment is applied to form a nitride film by nitriding the silicon film instead of forming the oxide film by oxidizing the silicon film, a nitrogen (N2) gas, an ammonia (NH3) gas or both of the nitrogen gas and the ammonia gas are supplied into the process chamber201and excited by plasma to nitride the silicon film.

Structure of Susceptor217

Next, the structure of the susceptor217, the heater218and the reflector219according to the first embodiment will be described in comparison with that of the susceptor217, the heater218and the reflector219according to a comparative example.

FIG. 2schematically illustrates a horizontal cross-section of the susceptor217where the reflector219is provided. The structure of the susceptor217according to the first embodiment and the structure of the susceptor217according to the comparative example are the same when viewed from the horizontal cross-section. The reflector219is provided so as to be accommodated in a space provided inside the susceptor217. In order to stably maintain the space accommodating the reflector219, an outer peripheral portion217A is provided on an outer periphery of the circular susceptor217, and a plurality of column portions217B are provided on an inner side of the circular susceptor217. In order to prevent the reflector219from contacting the outer peripheral portion217A and the plurality of column portions217B and from damaging the outer peripheral portion217A and the plurality of column portions217B when the reflector219is expanded and deformed due to the heat, gaps222are provided between the reflector219and the outer peripheral portion217A and between the reflector219and the plurality of column portions217B, respectively.

COMPARATIVE EXAMPLE

FIG. 3schematically illustrates a vertical cross-section of the susceptor217with the heater218and the reflector219embedded therein according to the comparative example. Specifically,FIG. 3schematically illustrates the vertical cross-section taken along the dot-and-dash line A-A′ of the susceptor217shown inFIG. 2.

The susceptor217is constituted by stacking an upper quartz plate217-1, a middle quartz plate217-2and a lower quartz plate217-3in order from the top. The wafer200is placed directly on an upper surface of the upper quartz plate217-1or via a component such as a susceptor cover (not shown). The upper quartz plate217-1and the middle quartz plate217-2are bonded by bonding a bonding surface223A and a bonding surface223B. The bonding surface223A is formed on a lower surface of the upper quartz plate217-1, and the bonding surface223B is formed on an upper surface of the middle quartz plate217-2, as shown inFIG. 3. The middle quartz plate217-2is bonded with the lower quartz plate217-3by bonding a bonding surface224A with a bonding surface224B. The bonding surface224A is formed on a lower surface of the middle quartz plate217-2, and the bonding surface224B is formed on an upper surface of the lower quartz plate217-3, as shown inFIG. 3. In a positional relationship with the bonding surface224A and224B, the upper quartz plate217-1and the middle quartz plate217-2constitute an upper susceptor, and the lower quartz plate217-3constitutes a lower susceptor.

A heater housing portion225which is a space where the heater218is accommodated is provided at the middle quartz plate217-2. The heater218is sealed between the upper quartz plate217-1and the middle quartz plate217-2by housing the heater218in the heater housing portion225and bonding the upper quartz plate217-1and the middle quartz plate217-2. Since the heater218is sealed in the susceptor217, the heater218does not contact with the gas in the process chamber201. According to the first embodiment, for example, the heater housing portion225is formed as a groove whose shape corresponds to the shape of the heater218. However, the shape of the heater housing portion225is not limited thereto. For example, the heater housing portion225may be formed as a recess of various shapes in the middle quartz plate217-2according to the shape of the heating element of the heater218.

A reflector housing portion226which is a space where the reflector219is accommodated is provided at the lower quartz plate217-3. The reflector219is sealed between the middle quartz plate217-2and the lower quartz plate217-3by accommodating the reflector219in the reflector housing portion226and bonding the middle quartz plate217-2and the lower quartz plate217-3. Since the reflector219is sealed in the susceptor217in a vacuum state, the reflector219does not contact with the gas in the process chamber201. According to the first embodiment, for example, the reflector housing portion226is formed as a recess in the lower quartz plate217-3according to the shape of the reflector219shown inFIG. 2.

According to the first embodiment, the susceptor217has a structure made of quartz and includes components such as the plurality of column portions217B at the inner side. Thus, it is generally difficult to bond the upper quartz plate217-1, the middle quartz plate217-2and the lower quartz plate217-3of the first embodiment using a welding technique for a susceptor made of a metal such as aluminum and stainless steel. Therefore, the quartz plates217-1,217-2and217-3are bonded one another using a thermocompression bonding technique (process). The thermocompression bonding process is performed by pressing the bonding surfaces223A,223B,224A and224B of the quartz plates217-1,217-2and217-3with one another at a predetermined pressure for a predetermined time at a high temperature whereat the viscosity of quartz decreases. In order to integrate the quartz of the quartz plates217-1,217-2and217-3with one another substantially without a boundary by using the thermocompression bonding process, the flatness of the bonding surfaces223A,223B,224A and224B is an important factor in addition to the temperature, the pressure and the time described above. Thus, for example, the bonding surfaces223A,223B,224A and224B are polished into a transparent and flat surface. Specifically, an entire surface of the bonding surface223A, a surface of the bonding surface223B excluding the portion where the heater housing portion225is provided, an entire surface of the bonding surface224A and a surface of the bonding surface224B excluding the portion where the reflector housing portion226is provided (that is, portions corresponding to the outer peripheral portion217A and the plurality of column portions217B) are processed into a transparent and flat surface. However, when the bonding surfaces223A,223B,224A and224B are formed and the thermocompression bonding process is performed as in the comparative example, the reflector219is expanded and deformed due to the heat to thereby cause the following problems.

FIGS. 4A and 4Bschematically illustrate a vertical cross-section of the susceptor217with the heater218and the reflector219embedded therein according to the comparative example. Specifically,FIG. 4Aschematically illustrates a state of the reflector219according to the comparative example while performing the thermocompression bonding process. While the thermocompression bonding process is performed, the quartz plates217-1,217-2and217-3are heated to a temperature at which the viscosity of the quartz decreases. However, the reflector219made of a metal material is also heated, and the metal material causes thermal expansion. It is difficult to heat the planar-shaped reflector219in a completely uniform manner. Thus, the reflector219is deformed by a difference in temperature distribution. Thus, for example, as shown inFIG. 4A, some portions of the reflector219may contact the bonding surface224A. In particular, when the temperature of the thermocompression bonding is high, the metal material of the reflector219thermally expands so much that the above contact is likely to occur due to deformation (refer to contact portions227indicated by dashed circles inFIG. 4A). Further, the portions of the reflector219contacting the bonding surface224A may be adhered to the bonding surface224A which is a transparent and flat surface.

FIG. 4Bschematically illustrates a state of the reflector219according to the comparative example when the susceptor217is cooled after the thermocompression bonding process. When the thermocompression bonding process is completed and the cooling of the susceptor217is performed, the reflector219contracts and tries to return to its original shape. If some portions of the reflector219are adhered to the bonding surface224A as shown inFIG. 4Abefore the reflector219starts contracting, a separating force acts on the adhered portions to separate them from the bonding surface224A. As a result, as shown inFIG. 4B, the surface of the bonding surface224A may peel off together with the adhered portions of the reflector219. Thus, cracks may occur on the surface of the bonding surface224A (refer to portion228where the cracks occur indicated by dashed circles inFIG. 4B). In addition, due to the adhesion during the thermocompression bonding process, the reflector219may not return to its original shape after cooling and may remain deformed.

When the cracks occur in the bonding surface224A, not only transmission of the radiant heat radiated from the heater218is hindered and the radiant heat is reflected in a non-uniform manner, but also the susceptor217may be damaged. Specifically, for example, when the inside of the process chamber201is vacuum exhausted in the substrate processing described above, the stress is generated in the susceptor217by the pressure difference between the inner pressure of the reflector housing portion226and the inner pressure of the process chamber201or the pressure difference between the inner pressure of the heater housing portion225and the inner pressure of the process chamber201, and the stress is concentrated in the cracks. As a result, the susceptor217may be damaged.

In order to address the above problems, it is possible to increase the depth of the reflector housing portion226so that the reflector219does not contact the bonding surface224A in the thermocompression bonding process. However, when the depth of the reflector housing portion226is increased, the plurality of column portions217B should be thickened or the number of the plurality of column portions217B should be increased to secure the strength of the susceptor217to withstand the stress applied when vacuum exhausting the inside of the processing chamber201(that is, the strength to withstand vacuum). Thereby, the area that the reflector219can be installed is reduced. As a result, the area for reflecting the radiant heat from the heater218is decreased, and the efficiency or the uniformity of the heating by the heater218deteriorates. Therefore, it is desirable to address the above problems without increasing the depth of the reflector housing portion226.

First Embodiment

Hereinafter, the first embodiment compared with the above-described comparative example will be described with reference toFIGS. 5, 6, 7A and 7B.FIG. 5schematically illustrates a vertical cross-section of the susceptor217with the heater218and the reflector219embedded therein according to the first embodiment. Specifically,FIG. 5schematically illustrates the vertical cross-section taken along the dot-and-dash line A-A′ of the susceptor217shown inFIG. 2.FIG. 6is a partial enlarged view of the susceptor217shown inFIG. 5. In the following description, the same components as those of the comparative example are denoted by the same reference numerals.

According to the first embodiment, a reflector facing recess229facing the reflector housing portion226is provided at the lower surface of the middle quartz plate217-2of the susceptor217. A ceiling surface (the surface facing the reflector housing portion226) of the reflector facing recess229is roughened to have a surface roughness equal to or greater than a predetermined value. InFIG. 6, the roughened ceiling surface is illustrated as a ceiling rough surface230.

The surface roughness of the ceiling rough surface230is at least greater than the surface roughness of the transparent and flat surface of the bonding surface224A. Therefore, as will be described later, as compared with the comparative example, it is possible to suppress the reflector219from adhering to the lower surface of the middle quartz plate217-2during the thermocompression bonding process. The surface roughness (hereinafter, also referred to as “Ra”) of the bonding surface224A is, for example, in the range of “Ra≤0.05 μm”, that is, Ra of the bonding surface224A is equal to or less than 0.05 μm, so that the bonding surface224A is easy to adhere to the bonding surface224B in the thermocompression bonding process. The surface roughness of the ceiling rough surface230according to the first embodiment is greater than Ra of the bonding surface224A. In order to more reliably suppress the adhesion of the reflector219to the ceiling rough surface230, preferably, the surface roughness of the ceiling rough surface230is, for example, in the range of “Ra≥0.1 μm”, that is, Ra of the ceiling rough surface230is equal to or greater than 0.1 μm. For example, in the first embodiment, “Ra=about 2 μm”, that is, Ra of the ceiling rough surface230is about 2 μm

It is possible to form the reflector facing recess229by grinding the polished bonding surface224A before the thermocompression bonding process. It is also possible to use a rough surface as the ceiling rough surface230. The rough surface is generated on the inner wall surface of the reflector facing recess229by grinding the polished bonding surface224A. In addition, the ceiling rough surface230is formed inside the reflector facing recess229. Thus, even after the reflector facing recess229is formed, it is also possible to polish the lower surface of the middle quartz plate217-2with the reflector facing recess229to form the bonding surface224A. The ceiling rough surface230may be formed by other roughening techniques including physical processing such as sandblasting or heat treatment and chemical processing using hydrogen fluoride.

In addition, a bottom surface (the surface on which the reflector219is placed) of the reflector housing portion226may be roughened having a surface roughness equal to or greater than a predetermined value. InFIG. 6, the roughened bottom surface is illustrated as a bottom rough surface262. By providing the bottom rough surface262, it is possible to suppress the reflector219from adhering to the bottom surface of the reflector housing portion226during the thermocompression bonding. The surface roughness of the bottom rough surface262may be the same as that of the ceiling rough surface230or may be appropriately selected within the range of the surface roughness of the ceiling rough surface230described above. Similar to the reflector facing recess229, it is possible to form the reflector housing portion226by grinding the upper surface of the lower quartz plate217-3before the thermocompression bonding process. It is also possible to use a rough surface as the bottom rough surface262. The rough surface is generated on the inner wall surface of the reflector housing portion226by grinding the upper surface of the lower quartz plate217-3. The polishing process for forming the bonding surface224B may be performed before or after forming the reflector housing portion226. Similar to the ceiling rough surface230, the bottom rough surface262may be formed by other roughening techniques.

FIGS. 7A and 7Bschematically illustrate the vertical cross-section of the susceptor219with the heater218and the reflector219embedded therein according to the first embodiment.FIG. 7Aschematically illustrates a state of the reflector219during the thermocompression bonding process, andFIG. 7Bschematically illustrates a state of the reflector219when the susceptor217is cooled after the thermocompression bonding process. Even in the first embodiment, the reflector219heated by the thermocompression bonding process is deformed by thermal expansion, and some portions of the reflector219may contact the ceiling rough surface230as shown in the contact portions227inFIG. 7A. However, according to the first embodiment, even if the deformed reflector219contacts with the lower surface of the middle quartz plate217-2, the contact portions227are located on a roughened surface (i.e., ceiling rough surface230). This makes it possible to suppress the reflector219from adhering to the ceiling rough surface230compared with the comparative example where the reflector219comes into contact with the bonding surface224A which is transparent and flat for the thermocompression bonding process. Therefore, as shown inFIG. 7B, even if the reflector219returns to its original shape after cooling, it is possible to prevent the reflector219from peeling or cracking the lower surface of the middle quartz plate217-2due to the adhering of the reflector219. It is also possible to reduce the problem that the reflector219can not return to its original shape by adhesion even after cooling.

In the above description, the first embodiment is described based on an example that the reflector219is deformed in the thermocompression bonding process of the susceptor217. However, when there is a possibility that the reflector219is deformed by being heated at a high temperature other than the thermocompression bonding process, the first embodiment can be applied. When the susceptor217is configured according to the first embodiment, it is possible to suppress the occurrence of the damage such as the cracks.

In addition, the bottom rough surface262on which the reflector219is placed is also roughened according to the first embodiment. Thus, it is possible to prevent the reflector219from adhering to the bottom surface of the reflector housing portion226during the thermocompression bonding process. It is also possible to suppress surface peeling that may occur at the bottom surface of the reflector housing portion226after cooling and reduce failure of the reflector219to return to its original shape from the deformed state.

According to the first embodiment, even if the deformed reflector219contacts with the lower surface of the middle quartz plate217-2, it is possible to suppress the reflector219from adhering to the lower surface of the middle quartz plate217-2. Thus, it is unnecessary to increase the depth of the reflector housing portion226for preventing the reflector219from contacting the lower surface of the middle quartz plate217-2. Therefore, it is possible to reduce the depth of the reflector housing portion226compared with the comparative example. It is also possible to improve the strength to withstand vacuum and to make the susceptor217having a thickness thinner than that of the comparative example. It is preferable to reduce the depth of the reflector facing recess229from the viewpoint of resistance to vacuum. According to the first embodiment, for example, the depth of the reflector facing recess229ranges from 0.2 mm to 0.4 mm, in consideration of machining accuracy.

Second Embodiment

Hereinafter, a second embodiment will be described with reference toFIGS. 8 and 9.FIG. 8schematically illustrates a vertical cross-section of the susceptor219with the heater218and the reflector219embedded therein according to the second embodiment. Specifically,FIG. 8schematically illustrates the vertical cross-section taken along the dot-and-dash line A-A′ of the susceptor217shown inFIG. 2.FIG. 9is a partial enlarged view of the susceptor217shown inFIG. 8. In the following description, the same components as those of the comparative example or the first embodiment are denoted by the same reference numerals.

The second embodiment is a modified example of the first embodiment described above. According to the second embodiment, the reflector facing recess229of the first embodiment is not provided. According to the second embodiment, portions of the lower surface of the middle quartz plate217-2facing the reflector housing portion226are roughened to have a surface roughness equal to or greater than a predetermined value. InFIG. 9, the lower surface of the roughened middle quartz plate217-2is illustrated as an upper rough surface261.

The surface roughness of the upper rough surface261is similar to that of the ceiling rough surface230in the first embodiment. That is, the surface roughness of the upper rough surface261is at least greater than the surface roughness of the transparent and flat surface of the bonding surface224A. Therefore, it is possible to suppress the reflector219from adhering to the lower surface of the middle quartz plate217-2during the thermocompression bonding process. In order to more reliably suppress the adhesion of the reflector219to the lower surface of the middle quartz plate217-2, preferably, the surface roughness of the upper rough surface261is, for example, in the range of “Ra≥0.1 μm”, that is, Ra of the upper rough surface261is equal to or greater than 0.1 μm.

As described above, according to the second embodiment, the reflector facing recess229of the first embodiment is not provided. Therefore, in order to form the upper rough surface261, it is preferable to use a roughening technique capable of performing a partial surface roughening to roughen the portions of the polished bonding surface224A facing the reflector housing portion226before the thermocompression bonding process. The roughening technique capable of performing the partial surface roughening includes, for example, physical processing such as sandblasting or heat treatment and chemical processing using hydrogen fluoride. However, other techniques may be used. For example, it is possible to form the bonding surface224A by polishing the lower surface of the middle quartz plate217-2without polishing the upper rough surface261formed in advance.

As described above, according to the second embodiment, the reflector facing recess229in the first embodiment is not provided. Therefore, it is possible to improve the strength to withstand vacuum and to make the susceptor217having a thickness thinner than that of the first embodiment.

While the embodiments described above exemplify a modification process such as an oxidation process and a nitridation process to the silicon film, the above-described technique is not limited thereto. The above-described technique may also be applied to other processes. For example, the above-described technique may be applied to an apparatus configured to perform a substrate processing such as a film-forming process by alternately supplying a source gas and a reactive gas, a heat treatment process, an annealing process, an ashing process and an etching process.

According to the technique described herein, it is possible to prevent the susceptor made of quartz from being damaged by contacting the reflector deformed by thermal expansion.