JP2010080811A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device provided with processes capable of processing a substrate by suppressing of roughness of the surface of the substrate. <P>SOLUTION: The method is provided with a process (step 302) of carrying in the substrate on the surface of which an oxide film with a thickness of 2 nm≤ is formed in a processing chamber; a process (step 305) of performing purge by N<SB>2</SB>O gas in the processing chamber after that; a process (step 306) of processing the substrate in the processing chamber after that; and a process (step 309) of carrying out the substrate from the processing chamber after that. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device including a step of forming a silicon oxide film on a semiconductor wafer using a CVD (Chemical Vapor Deposition) apparatus.

When an oxide film (CVD oxide film) is formed on a semiconductor silicon wafer using a CVD apparatus, an N ₂ purge box or the like is used to suppress the natural oxide film formed on the silicon wafer surface. Means for lowering the O ₂ concentration in the loading area may be used.

On the silicon wafer in which the natural oxide film is suppressed in this way, a silicon oxide film is formed by a CVD method using, for example, SiH ₂ Cl ₂ gas (DCS gas) and N ₂ O gas by a CVD apparatus. In order to improve the film quality of the CVD oxide film, an oxide film (DCS-HTO: Dichlorosilane High Temperature Oxide) may be formed at a high temperature of 800 ° C. or higher.

  When the natural oxide film is thin (2 nm or less) as described above, the wafer surface is rough at a high temperature of 800 ° C. or higher, and as a result, particle inspection is not performed in the particle inspection of the DCS-HTO film formed thereon. There was a problem that it would appear as.

  Accordingly, a main object of the present invention is to provide a method of manufacturing a semiconductor device including a process capable of processing a substrate while suppressing the roughness of the substrate surface.

According to the present invention,
Carrying a substrate having an oxide film of 2 nm or less formed on the surface thereof into the processing chamber;
Purging with N ₂ O gas in the processing chamber;
Processing the substrate in the processing chamber;
Unloading the substrate from the processing chamber;
A method of manufacturing a semiconductor device having the above is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a semiconductor device provided with the process which can suppress the roughness of a substrate surface and can process a board | substrate is provided.

Next, a preferred embodiment of the present invention will be described with reference to the drawings.
First, the phenomenon that the surface of the wafer is rough at a high temperature of 800 ° C. or more when the natural oxide film is thin (2 nm or less) will be described.

  Under a high pressure of 800 ° C. or higher and a low pressure (about 0.1 Torr to 10 Torr) commonly used in low pressure CVD (LP-CVD), as shown in FIG. 1, the natural oxide film 271 formed on the silicon substrate 270 When the film thickness t is thin (2 nm or less), SiO molecules 272 generated at the interface between the silicon substrate 270 and the natural oxide film 271 are gasified and escape from the surface of the natural oxide film 271 to cause etching (thermal etching). Therefore, the surface state of the wafer 200 is roughened. As a result, in the particle inspection of the DCS-HTO film formed on the natural oxide film 271, the surface of the DCS-HTO film appears as particles.

  On the other hand, when the film thickness t of the natural oxide film 271 of the wafer 200 is thick (exceeds 2 nm), SiO molecules generated at the interface between the silicon substrate 270 and the natural oxide film 271 as shown in FIG. 272 cannot escape from the surface of the natural oxide film 271 and thermal etching does not occur.

FIG. 3 is a diagram for explaining the reaction between Si and O ₂ with respect to the O ₂ gas partial pressure and the temperature of the wafer 200. Below the line 280, the reaction of the following formula (1) proceeds, and etching is performed. Occur.
2Si + O ₂ → 2SiO (1)
On the other hand, above the line 280, the reaction of the following formula (2) proceeds, and oxidation of Si occurs.
Si + O2 → SiO ₂ (2)

As shown in FIG. 3, in order not to cause thermal etching when the thickness t of the natural oxide film 271 is thin (2 nm or less), the wafer temperature and the O ₂ partial pressure are set so as to be in a region above the line 280. I think it would be good. For example, when the wafer temperature is 800 ° C., the O ₂ partial pressure may be 10 ⁻⁵ Torr or more. However, depending on the type of gas, increasing the O ₂ partial pressure not only suppresses thermal etching, but also makes the natural oxide film too thick, so it is preferable to select an appropriate gas type.

Therefore, in this embodiment, before forming a silicon oxide film (DCS-HTO film) by a CVD method at a high temperature of 800 ° C. or higher using SiH ₂ Cl ₂ gas (DCS gas) and N ₂ O gas. In addition, purging with N ₂ O gas is performed in the process of stabilizing the wafer temperature at a high temperature of 800 ° C. or higher. By purging with N ₂ O gas, thermal etching can be suppressed and the growth of the natural oxide film can also be suppressed. The pressure in the processing furnace when purging with N ₂ O gas is preferably about 0.1 Torr to 10 Torr.

  Next, a substrate processing apparatus used in this embodiment and a method for forming a DCS-HTO film using the apparatus will be described.

  FIG. 4 is a schematic configuration diagram of the processing furnace 202 of the substrate processing apparatus preferably used in the embodiment of the present invention, and is shown as a longitudinal sectional view.

  As shown in FIG. 4, the processing furnace 202 includes a heater 206 as a heating mechanism. The heater 206 has a cylindrical shape and is vertically installed by being supported by a heater base 251 as a holding plate.

A process tube 203 as a reaction tube is disposed inside the heater 206 concentrically with the heater 206. The process tube 203 includes an inner tube 204 as an internal reaction tube and an outer tube 205 as an external reaction tube provided on the outer side thereof. The inner tube 204 is made of a heat-resistant material such as quartz (SiO ₂ ) or silicon carbide (SiC), and is formed in a cylindrical shape having upper and lower ends opened. A processing chamber 201 is formed in the cylindrical hollow portion of the inner tube 204, and is configured so that wafers 200 as substrates can be accommodated in a state of being aligned in multiple stages in a horizontal posture and in a vertical direction by a boat 217 described later. The outer tube 205 is made of a heat-resistant material such as quartz or silicon carbide, and is formed in a cylindrical shape having an inner diameter larger than the outer diameter of the inner tube 204 and closed at the upper end and opened at the lower end. It is provided in the shape.

  A manifold 209 is disposed below the outer tube 205 concentrically with the outer tube 205. The manifold 209 is made of, for example, stainless steel and is formed in a cylindrical shape with an upper end and a lower end opened. The manifold 209 is engaged with the inner tube 204 and the outer tube 205, and is provided so as to support them. An O-ring 220a as a seal member is provided between the manifold 209 and the outer tube 205. Since the manifold 209 is supported by the heater base 251, the process tube 203 is installed vertically. A reaction vessel is formed by the process tube 203 and the manifold 209.

  A nozzle 230 as a gas introduction unit is connected to a seal cap 219 described later so as to communicate with the inside of the processing chamber 201, and a gas supply pipe 232 is connected to the nozzle 230. A processing gas supply source and an inert gas supply source (not shown) are connected to an upstream side of the gas supply pipe 232 opposite to the connection side with the nozzle 230 via an MFC (mass flow controller) 241 as a gas flow rate controller. Has been. A gas flow rate control unit 235 is electrically connected to the MFC 241 and is configured to control at a desired timing so that the flow rate of the supplied gas becomes a desired amount.

  The manifold 209 is provided with an exhaust pipe 231 that exhausts the atmosphere in the processing chamber 201. The exhaust pipe 231 is disposed at the lower end portion of the cylindrical space 250 formed by the gap between the inner tube 204 and the outer tube 205 and communicates with the cylindrical space 250. A vacuum exhaust device 246 such as a vacuum pump is connected to the downstream side of the exhaust pipe 231 opposite to the connection side with the manifold 209 via a pressure sensor 245 and a pressure adjustment device 242 as a pressure detector. The chamber 201 is configured to be evacuated so that the pressure in the chamber 201 becomes a predetermined pressure (degree of vacuum). A pressure control unit 236 is electrically connected to the pressure adjustment device 242 and the pressure sensor 245, and the pressure control unit 236 is installed in the processing chamber 201 by the pressure adjustment device 242 based on the pressure detected by the pressure sensor 245. Control is performed at a desired timing so that the pressure becomes a desired pressure.

  Below the manifold 209, a seal cap 219 is provided as a furnace port lid that can airtightly close the lower end opening of the manifold 209. The seal cap 219 is brought into contact with the lower end of the manifold 209 from the lower side in the vertical direction. The seal cap 219 is made of a metal such as stainless steel and has a disk shape. On the upper surface of the seal cap 219, an O-ring 220b is provided as a seal member that contacts the lower end of the manifold 209. A rotation mechanism 254 for rotating the boat is installed on the side of the seal cap 219 opposite to the processing chamber 201. A rotation shaft 255 of the rotation mechanism 254 passes through the seal cap 219 and is connected to a boat 217 described later, and is configured to rotate the wafer 200 by rotating the boat 217. The seal cap 219 is configured to be lifted vertically by a boat elevator 115 as a lifting mechanism vertically installed outside the process tube 203, and thereby the boat 217 is carried into and out of the processing chamber 201. Is possible. A drive control unit 237 is electrically connected to the rotation mechanism 254 and the boat elevator 115, and is configured to control at a desired timing so as to perform a desired operation.

  The boat 217 serving as a substrate holder is made of a heat-resistant material such as quartz or silicon carbide, and is configured to hold a plurality of wafers 200 in a horizontal posture and in a state where the centers are aligned with each other and held in multiple stages. ing. A plurality of heat insulating plates 216 as a disk-shaped heat insulating member made of a heat resistant material such as quartz or silicon carbide are arranged in a multi-stage in a horizontal posture at the lower part of the boat 217, and the heat from the heater 206 is arranged. Is difficult to be transmitted to the manifold 209 side.

  A temperature sensor 263 is installed in the process tube 203 as a temperature detector. A temperature control unit 238 is electrically connected to the heater 206 and the temperature sensor 263, and the temperature in the processing chamber 201 is adjusted by adjusting the power supply to the heater 206 based on the temperature information detected by the temperature sensor 263. Is controlled at a desired timing so as to have a desired temperature distribution.

  The gas flow rate control unit 235, the pressure control unit 236, the drive control unit 237, and the temperature control unit 238 also constitute an operation unit and an input / output unit, and are electrically connected to a main control unit 239 that controls the entire substrate processing apparatus. ing. These gas flow rate control unit 235, pressure control unit 236, drive control unit 237, temperature control unit 238, and main control unit 239 are configured as a controller 240.

Next, referring to FIGS. 4 and 5, SiH ₂ Cl ₂ gas (DCS gas) and N ₂ O gas are used as one step of the semiconductor device manufacturing process using the processing furnace 202 according to the above configuration. A method of forming a silicon oxide film (DCS-HTO film) on the wafer 200 by a CVD method at a high temperature of 800 ° C. or higher will be described. In the following description, the operation of each part constituting the substrate processing apparatus is controlled by the controller 240.

  When a plurality of wafers 200 are loaded into the boat 217 (wafer charge), as shown in FIG. 4, the boat 217 holding the plurality of wafers 200 is lifted by the boat elevator 115 and processed in the processing chamber 201. Is loaded (boat loading) (step 302, see FIG. 5). After the boat 217 is carried into the processing chamber 201, the seal cap 219 seals the lower end of the manifold 209 via the O-ring 220b.

Note that when the boat 217 loaded with the wafers 200 is carried into the processing chamber 201, the temperature in the processing chamber 201 is maintained at 600 ° C. Further, by using a N ₂ purge box (not shown) connected to the lower end of the manifold 209, the boat 217 is loaded into the processing chamber 201 in a state where the loading area is filled with the N ₂ atmosphere. O ₂ is prevented from being mixed. By doing so, the growth of the natural oxide film is suppressed when the wafer 200 is carried into the processing chamber 201 maintained at 600 ° C.

  The processing chamber 201 is evacuated by the evacuation device 246 so that the pressure in the processing chamber 201 is changed from atmospheric pressure to a desired pressure (degree of vacuum), for example, about 0.1 Pa to 1.0 Pa. Further, the heater 206 is heated so that the temperature in the processing chamber 201 rises from 600 ° C. to 800 ° C. or more. (See step 303, FIG. 5). The temperature rising rate is about 20 ° C./min, and since the time for which thermal etching occurs is short, thermal etching hardly occurs during this temperature rising.

  The pressure in the processing chamber 201 is measured by the pressure sensor 245, and the pressure regulator 242 is feedback controlled based on the measured pressure. Further, when the inside of the processing chamber 201 is heated (temperature rise, temperature drop, temperature maintenance) by the heater 206, the heater is based on temperature information detected by the temperature sensor 263 so that the inside of the processing chamber 201 has a desired temperature distribution. The degree of energization to 206 is feedback controlled.

  Thereafter, a leak check is performed (step 304, see FIG. 5). The pressure in the processing chamber 201 at this time is 0.1 Pa to 0.5 Pa, the temperature is 800 ° C. or higher, and the time is about 1 to 3 minutes. Since the time is short, thermal etching hardly occurs during the leak check.

Next, the temperature in the processing chamber 201 is stabilized at 800 ° C. or more (see step 305, FIG. 5). Since this stabilization takes about 40 minutes, thermal etching is suppressed by purging the inside of the processing chamber 201 with N ₂ O. Further, since N ₂ O gas is used as the purge gas, the growth of the natural oxide film is also suppressed. The pressure in the processing chamber 201 when purging with N ₂ O gas is 0.1 Torr to 10 Torr.

Subsequently, the wafer 200 is rotated by rotating the boat 217 by the rotation mechanism 254. Next, the gas supplied from the processing gas supply source and controlled to have a desired flow rate by the MFC 241 is introduced into the processing chamber 201 from the nozzle 230 through the gas supply pipe 232. The introduced gas rises in the processing chamber 201, flows out from the upper end opening of the inner tube 204 into the cylindrical space 250, and is exhausted from the exhaust pipe 231. The gas contacts the surface of the wafer 200 when passing through the processing chamber 201, and at this time, a thin film is deposited on the surface of the wafer 200 by a thermal CVD reaction (step 306, see FIG. 5).
In this embodiment, a silicon oxide film (DCS-HTO film) is formed by a CVD method using SiH ₂ Cl ₂ gas (DCS gas) and N ₂ O gas at 800 ° C. or higher.

When a preset processing time has elapsed, the supply of SiH ₂ Cl ₂ gas (DCS gas) and N ₂ O gas is stopped, and the rotation of the boat 217 is also stopped.
Thereafter, a cycle of repeatedly evacuating the processing chamber 201 by the evacuating apparatus 246 of the processing chamber 201 and supplying an inert gas (N ₂ gas in the present embodiment) from the inert gas supply source into the processing chamber 201. Purge is performed (see step 307, FIG. 5). Further, during the cycle purge, the temperature in the processing chamber 201 is lowered from 800 ° C. to 600 ° C.

Thereafter, an inert gas (N ₂ gas in the present embodiment) from an inert gas supply source is supplied into the processing chamber 201, the processing chamber 201 is filled with the inert gas, and the pressure in the processing chamber 201 is increased. Is restored to normal pressure (step 308, see FIG. 5).

  Thereafter, the seal cap 219 is lowered by the boat elevator 115, the lower end of the manifold 209 is opened, and the processed wafer 200 is carried out from the lower end of the manifold 209 to the outside of the process tube 203 while being held by the boat 217 ( Boat unloading) (see step 309, FIG. 5). Thereafter, the processed wafer 200 is taken out from the boat 217 (wafer discharge).

Note that when the boat 217 loaded with the wafers 200 is unloaded from the processing chamber 201, the temperature in the processing chamber 201 is maintained at 600 ° C. Further, an N ₂ purge box (not shown) is connected to the lower end of the manifold 209, and the boat 217 is taken out of the processing chamber 201 in a state where the loading area is filled with the N ₂ atmosphere, so that the processing chamber 201 is filled with O. ₂ is prevented from being mixed.

  Next, a film forming sequence for comparison will be described with reference to FIGS. In this comparative example, the processing chamber 201 is evacuated to a desired pressure (degree of vacuum) from the atmospheric pressure, and heated so that the temperature in the processing chamber 201 rises from 600 ° C. to 800 ° C. or more. The process up to step 403 is the same as the process up to step 303 in the preferred embodiment of the present invention described above.

Next, in the comparative example, the temperature in the processing chamber 201 is stabilized at 800 ° C. or higher (step 404, see FIG. 7). At the time of stabilization, the inside of the processing chamber 201 is purged with N ₂ . This stabilization takes about 40 minutes. The pressure in the processing chamber 201 when purging with N ₂ gas is 0.1 Torr to 1.0 Torr.

  Thereafter, a leak check is performed (step 405, see FIG. 7). The pressure in the processing chamber 201 at this time is 0.1 Pa to 0.5 Pa, the temperature is 800 ° C. or higher, and the time is about 1 to 3 minutes.

Subsequently, the wafer 200 is rotated by rotating the boat 217 by the rotation mechanism 254. Next, a silicon oxide film (DCS-HTO film) is formed by a CVD method at 800 ° C. or higher using SiH ₂ Cl ₂ gas (DCS gas) and N ₂ O gas (see step 406 and FIG. 7). The processes after Step 406 are the same as the processes after Step 306 in the above-described preferred embodiment of the present invention.

FIG. 6 shows a comparison result of the number of particles and the film thickness uniformity in the preferred embodiment of the present invention in which the N ₂ O purge is performed and the comparative example in which the N ₂ purge is performed at the time of temperature stabilization before the film formation.

  In FIG. 6, the film forming temperature is 800 ° C. or higher, but there is a variation in temperature depending on the position of the wafer 200 in the boat 217. In the column of temp representing the temperature during film formation, U represents the upper zone of the heater, CU represents the center upper zone of the heater, C represents the center zone of the heater, CL represents the center lower zone of the heater, L represents the lower zone of the heater.

The flow rate of SiH ₂ Cl ₂ gas (DCS gas) that flows during film formation is 20 sccm, and the flow rate of N ₂ O gas is 100 sccm. At the time of film formation, N ₂ for stabilizing the opening degree of the pressure control valve is also flowed by 200 sccm from the outside of the inner tube (see the column BP-N ₂ ).

The pressure during film formation is 0.25 Torr, and the film formation time is 16.5 minutes. The film formation rate is 4.060 Å / min in the preferred embodiment of the present invention in which the N ₂ O purge is performed, and 3.630 Å / min in the comparative example in which the N ₂ purge is performed.

  Refer to the thickness & unif. Column for the thickness of the silicon oxide film deposited and the uniformity of the film thickness within the wafer surface. In this column, TOP represents the monitor wafer in the boat top section, CT represents the monitor wafer in the boat center top section, CEN represents the monitor wafer in the boat center section, CB represents the monitor wafer in the boat center bottom section, BTM represents a monitor wafer in the boat bottom section.

  Refer to the WtoW column for the average value of the thickness of the deposited silicon oxide film and the uniformity between the wafers.

  See the Particle (> 0.12 μm) and Particle (> 0.5 μm) columns for the particle inspection results of the deposited silicon oxide film. Here, “Particle” (> 0.12 μm) means that the particle size of the particle is> 0.12 μm, and “Particle” (> 0.5 μm) means that the particle size of the particle is> 0.5 μm.

In the comparative example in which the N ₂ purge is performed, the wafer surface is roughened by thermal etching and counted as particles. On the other hand, in the preferred embodiment of the present invention in which the N ₂ O purge is performed, it is considered that particles are dramatically reduced and thermal etching is prevented. Further, there is no deterioration in uniformity due to the N ₂ O purge.

According to a preferred embodiment of the present invention, it is possible to form a high-quality DCS-HTO film at a high temperature and a low pressure of 800 ° C. or higher while suppressing a natural oxide film using N ₂ purge BOX. This can contribute to improving the performance of semiconductor devices in the future.

Further, by using the N _{2 O} gas used in film formation DCS-HTO, when the temperature stabilization before film formation, it is possible to prevent thermal etching by performing the N 2 _O purge, the introduction of new equipment It is not necessary and there is no need to cost equipment.

In the preferred embodiment of the present invention, DCS and N ₂ O gas are supplied as the film forming gas. However, even if other gases are used as the film forming gas as long as thermal etching is likely to occur. Can be applied as well.

The preferred embodiment of the present invention has been described above. However, according to the preferred embodiment of the present invention,
Carrying a substrate having an oxide film of 2 nm or less formed on the surface thereof into the processing chamber;
Purging with N ₂ O gas in the processing chamber;
Processing the substrate in the processing chamber;
Unloading the substrate from the processing chamber;
A method of manufacturing a semiconductor device having the above is provided.

Preferably, the film formed in the step of processing the substrate is a SiO ₂ film formed by vapor deposition, and DCS gas and N ₂ O gas are supplied as film forming gases.

Also, according to a preferred embodiment of the present invention,
A processing chamber for processing the substrate;
A first gas supply system that supplies N ₂ O gas that is a purge gas;
A second gas supply system for supplying a processing gas;
A control unit for controlling the configuration of each unit;
Have
The control unit includes a step of carrying a substrate having an oxide film of 2 nm or less formed on the surface thereof into the processing chamber and performing a purge with N ₂ O gas, and a step of processing the substrate in the processing chamber. Thus, a substrate processing apparatus for controlling is provided.

It is a schematic sectional drawing for demonstrating the state of the silicon wafer surface when an oxide film is thin. It is a schematic sectional drawing for demonstrating the state of the silicon wafer surface in case an oxide film is thick. It is a figure which shows the relationship between oxygen gas partial pressure and reaction of the silicon wafer surface. It is a schematic block diagram of the vertical processing furnace used with the substrate processing apparatus of preferable embodiment of this invention, and its accompanying member, It is the longitudinal cross-sectional view which cut | disconnected the processing furnace part in the vertical direction especially. It is a flowchart for demonstrating the film-forming sequence in preferable embodiment of this invention. It is a table for explaining an effect of the N _{2 O} purge in the preferred embodiment of the present invention. It is a flowchart for demonstrating the film-forming sequence for a comparison.

Explanation of symbols

115 Boat Elevator 200 Wafer 201 Processing Chamber 202 Processing Furnace 203 Process Chu 204 Inner Tube 205 Outer Tube 206 Heater 209 Manifold 216 Heat Insulation Plate 217 Boat 219 Seal Cap 220a, 220b O-ring 230 Nozzle 231 Exhaust Pipe 232 Gas Supply Pipe 235 Gas Flow Control 236 Pressure controller 237 Drive controller 238 Temperature controller 239 Main controller 240 Controller 241 Mass flow controller (MFC)
242 Pressure adjusting device 245 Pressure sensor 246 Vacuum exhaust device 250 Cylindrical space 251 Heater base 254 Rotating mechanism 255 Rotating shaft 263 Temperature sensor 270 Si substrate 271 Natural oxide film 272 SiO

Claims (2)

Carrying a substrate having an oxide film of 2 nm or less formed on the surface thereof into the processing chamber;
Purging with N ₂ O gas in the processing chamber;
Processing the substrate in the processing chamber;
Unloading the substrate from the processing chamber;
A method for manufacturing a semiconductor device comprising: The method for manufacturing a semiconductor device according to claim 1, wherein the film formed in the step of processing the substrate is a SiO ₂ film formed by vapor phase growth, and DCS gas and N ₂ O gas are supplied into the processing chamber as film forming gases. .

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