JP2011014688A - Method of manufacturing semiconductor device - Google Patents

Abstract

In manufacturing a semiconductor device, a manufacturing method is provided in which the amount of hydrogen contained in a silicon nitride film is reduced to ensure long-term reliability of memory operation.
A manufacturing method of a semiconductor device includes an oxygen-containing gas and a hydrogen-containing gas in a processing chamber in a state where the pressure in the processing chamber containing a silicon substrate 101a having a silicon nitride film 103 formed on the surface is lower than atmospheric pressure. And a step of oxidizing a part of the silicon nitride film 103 and a step of removing the oxidized portion 104 of the silicon nitride film 103.
[Selection] Figure 2

Description

  The present invention relates to a method for manufacturing a semiconductor device.

A charge trap type nonvolatile memory capable of trapping electrons at a defect level in an insulating film is known, and a silicon nitride film (Si ₃ N ₄ ) having many defect levels is an insulating film for capturing electrons. As widely used.

There are various methods for forming Si ₃ N ₄ , such as CVD (Chemical Vapor Deposition), in which dichlorosilane gas (SiH ₂ Cl ₂ ) and ammonia gas (NH ₃ ) are vapor-phase reacted under reduced pressure, and atoms are deposited. It is known to form each layer by ALD (Atomic Layer Deposition) method or the like, but all formed Si ₃ N ₄ has a high concentration of 10 ²¹ atoms / cm ² or more in the film. Contains hydrogen (H).

  Since the hydrogen (H) contained in the silicon nitride film has a weak bond with silicon (Si), the hydrogen-silicon bond is broken by repeated stress due to the application of a high electric field accompanying writing and erasing of the memory. The amount decreases. When the amount of hydrogen contained decreases, silicon dangling species are formed in the silicon nitride film, which functions as an electron trapping site. Since the number of electrons trapped in the silicon nitride film is an element that affects the operability of the memory, if the number of electrons changes, the operability of the memory becomes unstable and long-term reliability is lost. .

  Therefore, an object of the present invention is to provide a stable silicon nitride film forming technique with a low hydrogen content.

According to one embodiment of the present invention, an oxygen-containing gas and a hydrogen-containing gas are supplied into the processing chamber in a state where the pressure in the processing chamber containing a substrate having a silicon nitride film formed on the surface is lower than atmospheric pressure. Oxidizing a part of the silicon nitride film,
Removing the oxidized portion of the silicon nitride film;
A method of manufacturing a semiconductor device is provided.

According to another aspect of the present invention, after forming a silicon nitride film on the surface of the substrate by supplying a film forming gas into the processing chamber containing the substrate, the pressure in the processing chamber is set lower than atmospheric pressure. Supplying an oxygen-containing gas and a hydrogen-containing gas into the processing chamber to oxidize a part of the silicon nitride film;
Removing the oxidized portion of the silicon nitride film;
A method of manufacturing a semiconductor device is provided.

  According to the present invention, since a silicon nitride film with a small amount of hydrogen can be formed on the substrate surface, the influence of hydrogen desorption from the silicon nitride film can be suppressed.

It is a graph which shows the result of having analyzed and compared the composition of the silicon nitride film. It is process drawing which showed the manufacturing process of the silicon nitride film. It is a graph which shows the result of having analyzed and compared the composition of the silicon nitride film in each step of the manufacturing process of a silicon nitride film. It is a schematic longitudinal cross-sectional view which shows the processing furnace of a substrate processing apparatus. FIG. 5 is a cross-sectional view of a part of the processing furnace, taken along the cutting line VV in FIG. 4. It is a processing flow figure of manufacture of a silicon nitride film.

The inventors have discovered the following properties in one step of the semiconductor device manufacturing process.
FIG. 1 shows the result of analysis and comparison of the composition by SIMS (Secondary Ion Mass Spectroscopy) for an evaluation sample manufactured by the method shown below.
A processing chamber containing a silicon wafer having a silicon nitride film with a thickness of about 20 nm (200 mm) on the surface is set to a pressure lower than atmospheric pressure, and an oxygen-containing gas and a hydrogen-containing gas are supplied into the processing chamber. And the target evaluation sample was manufactured by oxidizing the surface layer part (part from the surface to a certain depth) of a silicon nitride film. O ₂ gas was used as the oxygen-containing gas, and H ₂ gas was used as the hydrogen-containing gas. In preparing the evaluation sample, the pressure in the processing chamber was set to about 1 to 100 Pa, O ₂ gas was supplied at a flow rate of 1 to 10 slm, and H ₂ gas was supplied at a flow rate of 0.1 to 1 slm. In addition, the temperature in the processing chamber was set to two temperatures of 900 ° C. and 750 ° C., and two evaluation samples were prepared.

1A and 1B, the horizontal axis indicates the depth (nm) from the wafer outermost surface, the left vertical axis indicates the concentration of H, C, and N (atoms / cm ³ ) and the right side. The vertical axis represents the secondary ion intensity (counts / sec) of O and Si. In FIGS. 1A and 1B, a silicon nitride film having a thickness of about 20 nm (200 mm) is oxidized under the condition that a silicon oxide film of 70 mm can be formed on a silicon substrate at 900 ° C. and 750 ° C., respectively. This is based on the film obtained. Further, the broken line indicated by “Si ₃ N ₄ reference” in FIG. 1 is a comparative example showing the hydrogen content of silicon nitride not subjected to oxidation treatment.

Referring to FIGS. 1A and 1B, from the value of the secondary ion intensity of oxygen (O), the surface layer portion includes silicon oxide and silicon oxynitride, and the silicon nitride film is oxidized in the lower layer. I understand that it is not. In both cases of FIGS. 1A and 1B, the hydrogen content in the silicon nitride film below the surface layer is greatly reduced as compared with the silicon nitride film not subjected to oxidation treatment. I understand that. This effect is not observed in an annealing process under an inert gas atmosphere such as N ₂ or Ar at a reduced pressure and high temperature (up to 900 ° C.) with respect to the silicon nitride film or in a single atmosphere of H ₂ gas, and the pressure is lower than atmospheric pressure. It can be said that the effect is obtained by oxidizing the surface layer portion of the silicon nitride film by supplying an oxygen-containing gas and a hydrogen-containing gas into the set processing chamber. Then, by removing the surface layer portion of the silicon nitride film oxidized by this oxidation treatment, a silicon nitride film having a small amount of hydrogen can be obtained.
Hereinafter, specific steps of this method will be described with reference to FIG.

FIG. 2 is a process diagram showing a processing method for manufacturing a silicon nitride film having a small hydrogen content. This step includes a silicon nitride film forming step, an oxidation treatment step, and an etching treatment step. FIG. 2A shows the case of processing a silicon substrate, and FIG. 2B shows the case of processing a silicon substrate having an oxide film (SiO ₂ film) formed on the surface.

  2A, first, a silicon substrate 101a is accommodated in a processing chamber, and a silicon nitride film 103 having a film thickness c is deposited on the silicon substrate 101a by a CVD method or an ALD method (silicon nitride film formation). Membrane process). Here, the film thickness c of the silicon nitride film 103 is 500 mm or less, for example, 100 mm or less.

Subsequently, an oxygen-containing gas and a hydrogen-containing gas are supplied into the processing chamber set to a pressure lower than the atmospheric pressure to oxidize the silicon nitride film 103 (oxidation processing step). As a result, the surface layer portion (portion from the surface to the depth b) of the silicon nitride film 103 is oxidized to form the oxide film 104, and the remaining portion (portion of the film thickness a) is not oxidized. The oxide film 104 is made of silicon oxide (SiO _x ) or silicon oxynitride (SiO _x N _y ). At this time, the processing chamber temperature is set to a temperature in the range of 400 to 1000 ° C., the processing chamber pressure is set to a pressure in the range of 0.1 to 1000 Pa, and the O ₂ gas flow rate is set to a flow rate in the range of 20 sccm to 10 slm. The H ₂ gas flow rate is set to a flow rate in the range of 10 sccm to 5 slm.
Here, the thickness control of the oxide film 104 is performed based on the following method.
The amount of oxidation that forms the film thickness b on the surface of the silicon nitride film is defined by the film thickness that oxidizes the surface of the silicon substrate under the same oxidation conditions, so that the oxidation amount does not exceed the film thickness c of the silicon nitride film that is the oxide. In addition, the target film thickness a that is originally required is not exceeded. The relationship between the thickness of the silicon oxide film formed when the surface of the silicon substrate is oxidized under the same oxidation condition and the thickness of the silicon oxide film formed when the surface of the silicon nitride film is oxidized is obtained. This is estimated from the thickness of the silicon oxide film formed when the surface is oxidized.

  The oxide film 104 formed by the oxidation treatment is removed by wet etching using a hydrofluoric acid aqueous solution (HF) or the like (etching treatment step). Note that the oxide film 104 may be removed by dry etching.

As described above, a silicon nitride film having a small hydrogen content can be formed on the silicon substrate surface.
In the oxidation process, the hydrogen concentration in the silicon nitride film can be reduced as the temperature in the processing chamber is higher and the concentration of the supplied H ₂ gas is lower.

  FIG. 2B shows a case where the same processing as described above is performed on a silicon substrate having an oxide film formed on the surface.

FIG. 3 shows the results of analysis and comparison of the composition by SIMS for the wafers in each stage after (a) the silicon nitride film formation step, (b) the oxidation treatment step, and (c) the etching treatment step.
FIG. 3 (a) is measured after the silicon nitride film forming step is performed at 600 ° C. by the ALD method, and FIG. 3 (b) is after the above-described oxidation processing step is performed at a processing chamber temperature of 900 ° C. FIG. 3C shows the measurement after the wafer is once exposed to the atmosphere after the etching process.

3A, 3B, and 3C, the horizontal axis indicates the depth (nm) from the wafer outermost surface, and the vertical axis indicates the concentration of H, C, O, and Cl (atoms / cm ³ ). Is shown.

The results of FIGS. 3A and 3B show that the hydrogen content is reduced after the oxidation treatment process than after the silicon nitride film formation process. Further, the results of FIGS. 3B and 3C show that the hydrogen content reduced by the oxidation treatment process is maintained after the etching treatment process.
This will be specifically described below. Referring to FIG. 3A, it can be seen that the hydrogen concentration in the silicon nitride film is approximately constant at about 10 ²² atoms / cm ³ within a depth range of about 5 to 23 nm. On the other hand, in FIG. 3B, silicon oxide or silicon oxynitride is formed in the range of about 3 nm from the outermost surface, and the hydrogen concentration is in the range of about 3 to 10 nm below the lower layer. Is about 6 × 10 ²⁰ atoms / cm ³ . Therefore, it was shown that the amount of hydrogen contained in the unoxidized portion of the underlying silicon nitride film can be reduced by oxidizing the surface by the above-described oxidation method after the silicon nitride film forming step.
Referring to FIG. 3C, the oxide film (silicon oxide or silicon oxynitride) is removed by etching, and the silicon nitride film has a hydrogen content of 6 within a depth of 1 to 7 nm of the silicon nitride film. It is about × 10 ²⁰ atoms / cm ³ , and this value almost coincides with the hydrogen content shown in FIG. Thus, it can be seen that even when the oxide film is removed and exposed to the atmosphere, the state in which the hydrogen content is reduced is maintained.

Examples of the present invention will be described below.
The substrate processing apparatus in this embodiment will be described with reference to FIGS. FIG. 4 is a schematic longitudinal sectional view showing a processing furnace 202 of a substrate processing apparatus suitably used in an embodiment of the present invention. FIG. 5 is a cross-sectional view taken along the cutting line VV of FIG. The present invention can be suitably applied not only to the substrate processing apparatus according to this embodiment but also to a substrate processing apparatus having a single wafer type hot wall type or cold wall type processing furnace.

  As shown in FIG. 4, the processing furnace 202 includes a heater 207 as a heating unit (heating mechanism). The heater 207 has a cylindrical shape and is vertically installed by being supported by a heater base (not shown) as a holding plate.

Inside the heater 207, a process tube 203 as a reaction tube is disposed concentrically with the heater 207. The process tube 203 is made of quartz (SiO ₂ ), silicon carbide (SiC), or other heat resistant material, and is formed in a cylindrical shape with the upper end closed and the lower end opened. A processing chamber 201 is formed in a hollow portion of the process tube 203, 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.

  A manifold 209 is disposed below the process tube 203 concentrically with the process tube 203. The manifold 209 is made of stainless steel or other metal material and is formed in a cylindrical shape with an upper end and a lower end opened. The manifold 209 is engaged with the process tube 203 and is provided to support the process tube 203. An O-ring 220a as a seal member is provided between the manifold 209 and the process tube 203. Since the manifold 209 is supported by the heater base, the process tube 203 is installed vertically. A reaction vessel (processing vessel) is formed by the process tube 203 and the manifold 209.

  In the manifold 209, a first nozzle 233a as a first gas introduction part, a second nozzle 233b as a second gas introduction part, and a third nozzle 233c as a third gas introduction part pass through the side wall of the manifold 209. The first gas supply pipe 232a, the second gas supply pipe 232b, and the third gas supply pipe 232c are connected to the first nozzle 233a, the second nozzle 233b, and the third nozzle 233c, respectively. Thus, three gas supply pipes are provided in the processing chamber 201 as gas supply paths for supplying a plurality of types, here three types of processing gases.

The first gas supply pipe 232a is provided with a mass flow controller 241a as a flow rate controller (flow rate control means) and a valve 243a as an on-off valve in order from the upstream direction. A first inert gas supply pipe 234a that supplies an inert gas is connected to the downstream side of the valve 243a of the first gas supply pipe 232a. The first inert gas supply pipe 234a is provided with a mass flow controller 241c that is a flow rate controller (flow rate control means) and a valve 243c that is an on-off valve in order from the upstream direction. The first nozzle 233a is connected to the tip of the first gas supply pipe 232a. The first nozzle 233 a is disposed in an arcuate space between the inner wall of the process tube 203 constituting the processing chamber 201 and the wafer 200, and extends along the inner wall of the process tube 203 and along the loading direction of the wafer 200. , Extending from bottom to top. A plurality of gas supply holes 248a, which are gas supply holes, are provided on the side surface of the first nozzle 233a. These gas supply holes 248a have the same area and are arranged vertically at equal intervals. The first gas supply pipe 232a, the mass flow controller 241a, the valve 243a and the first nozzle 233a constitute a first gas supply system, and the first inert gas supply pipe 234a, the mass flow controller 241c and the valve 243c provide the first inert gas. A supply system is configured.
A gas containing oxygen as a constituent element (oxygen-containing gas), for example, oxygen (O ₂ ) gas, is supplied from the first gas supply pipe 232a. Therefore, the first gas supply system is configured as an oxygen-containing gas supply system. As the oxygen-containing gas, ozone (O ₃ ) gas, nitrogen monoxide (NO) gas, nitrous oxide (N ₂ O) gas, or the like may be used instead of oxygen (O ₂ ) gas. Moreover, you may use these mixed gas.

The second gas supply pipe 232b is provided with a mass flow controller 241b as a flow rate controller (flow rate control means) and a valve 243b as an on-off valve in order from the upstream direction. A second inert gas supply pipe 234b that supplies an inert gas is connected to the downstream side of the valve 243b of the second gas supply pipe 232b. The second inert gas supply pipe 234b is provided with a mass flow controller 241d as a flow rate controller (flow rate control means) and a valve 243d as an on-off valve in order from the upstream direction. The second nozzle 233b is connected to the tip of the second gas supply pipe 232b. The second nozzle 233 b is disposed in an arc-shaped space between the inner wall of the process tube 203 constituting the processing chamber 201 and the wafer 200, and extends along the inner wall of the process tube 203 and along the loading direction of the wafer 200. , Extending from bottom to top. A plurality of gas supply holes 248b that are gas supply holes are provided on the side surface of the second nozzle 233b. These gas supply holes 248b have the same area and are arranged in the vertical direction at equal intervals. The second gas supply pipe 232b, the mass flow controller 241b, the valve 243b and the second nozzle 233b constitute a second gas supply system, and the second inert gas supply pipe 234b, the mass flow controller 241d and the valve 243d supply the second inert gas. A system is constructed.
The second gas supply pipe 232b is configured to supply a gas containing hydrogen as a constituent element (hydrogen-containing gas), for example, hydrogen (H ₂ ) gas. Therefore, the second gas supply system is configured as a hydrogen-containing gas supply system. As the hydrogen-containing gas, ammonia (NH ₃ ) gas or methane (CH ₄ ) gas may be used instead of hydrogen (H ₂ ) gas. Moreover, you may use these mixed gas.

The third gas supply pipe 232c is provided with a mass flow controller 241e as a flow rate controller (flow rate control means) and a valve 243e as an on-off valve in order from the upstream direction. Further, a third inert gas supply pipe 234c for supplying an inert gas is connected to the downstream side of the valve 243e of the third gas supply pipe 232c. The third inert gas supply pipe 234c is provided with a mass flow controller 241f as a flow rate controller (flow rate control means) and a valve 243f as an on-off valve in order from the upstream direction. The third nozzle 233c described above is connected to the tip of the third gas supply pipe 232c. The third nozzle 233 c is disposed in an arc-shaped space between the inner wall of the process tube 203 constituting the processing chamber 201 and the wafer 200, and extends along the inner wall of the process tube 203 and along the loading direction of the wafer 200. , Extending from bottom to top. A plurality of gas supply holes 248c, which are supply holes for supplying gas, are provided on the side surface of the third nozzle 233c. These gas supply holes 248c have the same area and are arranged in the vertical direction at equal intervals. The third gas supply pipe 232c, the mass flow controller 241e, the valve 243e and the third nozzle 233c constitute a third gas supply system, and the third inert gas supply pipe 234c, the mass flow controller 241f and the valve 243f supply the third inert gas. A system is constructed.
From the third gas supply pipe 232c, a raw material gas, that is, a gas containing silicon as a constituent element (silicon-containing gas), for example, hexachlorodisilane (Si ₂ Cl ₆ , abbreviated as HCD) gas is supplied. Therefore, the third gas supply system is configured as a source gas supply system (silicon-containing gas supply system). As the silicon-containing gas, an inorganic raw material such as TCS (tetrachlorosilane, SiCl ₄ ), DCS (dichlorosilane, SiH ₂ Cl ₂ ) or SiH ₄ (monosilane) may be used instead of HCD, or an aminosilane-based gas may be used. 4DMAS (tetrakisdimethylaminosilane, Si (N (CH ₃ ) ₂ )) ₄ ), 3DMAS (trisdimethylaminosilane, Si (N (CH ₃ ) ₂ )) ₃ H), 2DEAS (bisdiethylaminosilane, Si (N (C Organic raw materials such as ₂ H ₅ ) ₂ ) ₂ H ₂ ), BTBAS (Bisturary butylaminosilane or SiH ₂ (NH (C ₄ H ₉ )) ₂ ) may be used.

The fourth gas supply pipe 232d is provided with a mass flow controller 241g as a flow rate controller (flow rate control means) and a valve 243g as an on-off valve in order from the upstream direction. The second inert gas supply pipe 234b is connected to the downstream side of the valve 243g of the fourth gas supply pipe 232d. The fourth gas supply pipe 232d is connected to the second gas supply pipe 232b through the second inert gas supply pipe 234b. A fourth gas supply system is mainly configured by the fourth gas supply pipe 232d, the mass flow controller 241g, the valve 243g, and the second nozzle 233b.
The fourth gas supply pipe 232d is configured to supply a gas containing nitrogen as a constituent element (nitrogen-containing gas), for example, ammonia (NH ₃ ) gas. Therefore, the fourth gas supply system is configured as a nitrogen-containing gas supply system. As the nitrogen-containing gas, hydrazine (N ₂ H ₄ ) or the like may be used instead of NH ₃ gas. Moreover, you may use these mixed gas.

  In this embodiment, the hydrogen-containing gas and the nitrogen-containing gas are supplied from the same nozzle into the processing chamber 201. However, the hydrogen-containing gas and the nitrogen-containing gas are separately supplied from the separate nozzles to the processing chamber. You may make it supply in 201. FIG. In this embodiment, the oxygen-containing gas, the hydrogen-containing gas or the nitrogen-containing gas, and the silicon-containing gas are configured to be supplied into the processing chamber 201 from separate nozzles. The silicon-containing gas may be supplied into the processing chamber 201 from the same nozzle. Further, the oxygen-containing gas and the nitrogen-containing gas may be supplied into the processing chamber 201 from the same nozzle. As described above, if the nozzles are shared by a plurality of types of gases, the number of nozzles can be reduced, the apparatus cost can be reduced, and maintenance can be facilitated.

  The manifold 209 is provided with a gas exhaust pipe 231 that exhausts the inside of the processing chamber 201. A downstream side of the gas exhaust pipe 231 opposite to the connection side with the manifold 209 is connected via a pressure sensor 245 as a pressure detector and an APC (Auto Pressure Controller) valve 242 as a pressure regulator (pressure regulator). A vacuum pump 246 as a vacuum exhaust device is connected. The APC valve 242 is configured such that the valve can be opened and closed to evacuate / stop the evacuation of the processing chamber 201, and the pressure can be adjusted by adjusting the valve opening. By adjusting the opening degree of the APC valve 242 based on the pressure detected by the pressure sensor 245 while operating the vacuum pump 246, the pressure in the processing chamber 201 becomes a predetermined pressure (degree of vacuum). It is configured to be evacuated. The gas exhaust pipe 231, the pressure sensor 245, the APC valve 242 and the vacuum pump 246 constitute an exhaust system.

  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 configured to contact the lower end of the manifold 209 from the lower side in the vertical direction. The seal cap 219 is made of stainless steel or other metal material and is formed in 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. On the opposite side of the seal cap 219 from the processing chamber 201, a rotation mechanism 267 for rotating a boat 217 as a substrate holder described later is installed. A rotation shaft 255 of the rotation mechanism 267 passes through the seal cap 219 and is connected to the boat 217. The rotation mechanism 267 is configured to rotate the wafer 200 by rotating the boat 217. The seal cap 219 is configured to be lifted and lowered in the vertical direction by a boat elevator 115 as a lifting mechanism that is vertically installed outside the process tube 203. The boat elevator 115 is configured such that the boat 217 can be carried into and out of the processing chamber 201 by moving the seal cap 219 up and down.

  The boat 217 as the substrate holder is made of quartz, silicon carbide, or other heat-resistant material, and is configured to hold a plurality of wafers 200 in a horizontal posture and aligned in a state where the centers are aligned with each other in multiple stages. Has been. A heat insulating member 218 made of quartz, silicon carbide, or other heat resistant material is provided at the lower part of the boat 217 so that heat from the heater 207 is not easily transmitted to the seal cap 219 side. Instead of providing the heat insulating member 218, a heat insulating material constituted by a plurality of heat insulating plates made of quartz, silicon carbide or other heat resistant materials and a heat insulating plate holder that supports these heat insulating plates in a multi-stage in a horizontal posture is provided. You may do it. A temperature sensor 263 as a temperature detector is installed in the process tube 203, and the temperature in the processing chamber 201 is adjusted by adjusting the degree of energization to the heater 207 based on the temperature information detected by the temperature sensor 263. Is configured to have a desired temperature distribution. The temperature sensor 263 is provided along the inner wall of the process tube 203, similarly to the first nozzle 233a, the second nozzle 233b, and the third nozzle 233c.

  The controller 280 as a control unit (control means) includes mass flow controllers 241a, 241b, 241c, 241d, 241e, 241f, 241g, valves 243a, 243b, 243c, 243d, 243e, 243f, 243g, pressure sensors 245, APC valves 242. , Heater 207, temperature sensor 263, vacuum pump 246, rotation mechanism 267, boat elevator 115, and the like. The controller 280 controls the gas flow rate by the mass flow controllers 241a, 241b, 241c, 241d, 241e, 241f, 241g, the opening / closing operation of the valves 243a, 243b, 243c, 243d, 243e, 243f, 243g, the opening / closing of the APC valve 242 and the pressure sensor. The pressure adjustment operation based on H.245, the temperature adjustment of the heater 207 based on the temperature sensor 263, the start / stop of the vacuum pump 246, the rotation speed adjustment of the rotation mechanism 267, and the lifting / lowering operation of the boat 217 by the boat elevator 115 are performed.

  Next, an example of a method for manufacturing a silicon nitride film according to the present invention, which is performed as one step of a manufacturing process of a semiconductor device (device) using the above-described processing furnace, will be described. In the following description, the operation of each part constituting the substrate processing apparatus is controlled by the controller 280.

  FIG. 6 shows a processing flowchart in the present embodiment. In the processing sequence of this embodiment, a silicon-containing layer (raw material adsorption layer or silicon layer) is formed on a substrate by supplying a silicon-containing gas as a source gas into a processing container containing the substrate, The step of reforming the silicon-containing layer formed on the substrate to a nitride layer by supplying a nitrogen-containing gas into the container is defined as one cycle, and this cycle is performed at least once, so that a predetermined amount is formed on the substrate. A silicon nitride film having a thickness is formed (silicon nitride film forming step). Subsequently, the surface layer portion of the silicon nitride film is oxidized by supplying an oxygen-containing gas and a hydrogen-containing gas into the processing chamber in a state where the pressure in the processing chamber is lower than the atmospheric pressure, and silicon oxide and silicon oxynitride Is formed (oxidation treatment step). By removing these oxide films by etching, a silicon nitride film having a low hydrogen content can be obtained on the surface (etching process).

  The step of forming a silicon-containing layer on the substrate is performed under conditions where an ALD reaction or a CVD reaction occurs. At this time, a silicon-containing layer (raw material adsorption layer or silicon layer) of less than one atomic layer to several atomic layers is formed on the substrate. ). The layer having less than one atom means an atomic layer formed discontinuously. Under conditions where an ALD reaction occurs, a raw material adsorption layer is formed on the substrate, and under conditions where a CVD reaction occurs, a silicon layer is formed on the substrate. The raw material adsorption layer includes a continuous adsorption layer of raw material molecules and a discontinuous adsorption layer. The silicon layer includes a continuous layer made of silicon, a discontinuous layer, and a silicon thin film formed by overlapping these layers. A continuous layer made of silicon may be referred to as a silicon thin film.

  Further, in the oxidation treatment process, an oxygen-containing gas and a hydrogen-containing gas are reacted in a processing chamber having a pressure lower than atmospheric pressure to generate oxygen-containing oxidizing species, and the surface layer portion of the silicon nitride film is oxidized by the oxidizing species. Then, the surface layer portion of the silicon nitride film is modified to silicon oxynitride or silicon oxide. According to this oxidation treatment step, the oxidizing power can be greatly improved as compared with the case where the oxygen-containing gas is supplied alone. The oxidation process is performed in non-plasma.

This will be specifically described below. In the embodiments described below, carried out by using HCD gas as a source gas, NH ₃ gas as the nitrogen-containing gas, O ₂ gas as an oxygen-containing gas, H ₂ gas as the hydrogen-containing gas. As the inert gas, N ₂ gas, Ar gas, He gas, Ne gas, Xe gas and other inert gases are used.

  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. It is carried in (boat loading). In this state, the seal cap 219 seals the lower end of the manifold 209 via the O-ring 220b.

  The processing chamber 201 is evacuated by a vacuum pump 246 so that a desired pressure (degree of vacuum) is obtained. At this time, the pressure in the processing chamber 201 is detected by the pressure sensor 245, and the controller 280 performs feedback control of the APC valve 242 based on the detected pressure (pressure adjustment). Further, the processing chamber 201 is heated by the heater 207 so as to have a desired temperature. At this time, based on the temperature information detected by the temperature sensor 263 so that the inside of the processing chamber 201 has a desired temperature distribution, the controller 280 feedback-controls the power supply to the heater 207 (temperature adjustment). Subsequently, the wafer 200 is rotated by rotating the boat 217 by the rotation mechanism 267. Thereafter, the four operations of steps 1 to 4 are sequentially executed.

[Step 1]
The controller 280 opens the valve 243e of the third gas supply pipe 232c and the valve 243f of the third inert gas supply pipe 234c, and the HCD gas and the third inert gas supply pipe as the film forming gas are supplied to the third gas supply pipe 232c. An inert gas is allowed to flow through 234c. The HCD gas is supplied from the third gas supply pipe 232c and the flow rate is adjusted by the mass flow controller 241e. The inert gas is supplied from the third inert gas supply pipe 234c, and the flow rate is adjusted by the mass flow controller 241f. The HCD gas whose flow rate has been adjusted is mixed with the inert gas whose flow rate has been adjusted in the third gas supply pipe 232c, and is heated from the gas supply hole 248c of the third nozzle 233c into the heated processing chamber 201 in a reduced pressure state. While being supplied, the gas is exhausted from the gas exhaust pipe 231 (HCD gas supply).

  At this time, the controller 280 appropriately adjusts the APC valve 242 to maintain the pressure in the processing chamber 201 at a pressure lower than atmospheric pressure, for example, in a range of 10 to 1000 Pa. The supply flow rate of the HCD gas controlled by the mass flow controller 241e is set, for example, within a range of 10 to 1000 sccm. The time for exposing the wafer 200 to the HCD gas is, for example, a time within a range of 1 to 180 seconds. The temperature of the heater 207 is set so as to cause an ALD reaction or a CVD reaction in the processing chamber 201, and the temperature of the wafer 200 is set to a temperature within a range of 300 to 650 ° C., for example. When the temperature of the wafer 200 is less than 300 ° C., it becomes difficult for HCD to be adsorbed on the wafer 200. Further, when the temperature of the wafer 200 exceeds 650 ° C., the CVD reaction becomes strong, and the uniformity tends to deteriorate. Therefore, the temperature of the wafer 200 is preferably 300 to 650 ° C. The temperature of the wafer 200 is preferably set to the same temperature in steps 1 to 4.

  By supplying the HCD gas into the processing chamber 201 under the above-described conditions, a silicon-containing layer of less than one atomic layer to several atomic layers is formed on the wafer 200 (surface base film). Note that, under conditions where an ALD reaction occurs, HCD is adsorbed on the surface of the wafer 200 to form an adsorption layer of a raw material by HCD. Under conditions where a CVD reaction occurs, the HCD self-decomposes to deposit silicon molecules on the wafer 200 to form a silicon layer. When the thickness of the silicon-containing layer formed on the wafer 200 exceeds several atomic layers, the nitriding action in step 3 described later does not reach the entire silicon-containing layer. The minimum value of the silicon-containing layer that can be formed on the wafer 200 is less than one atomic layer. Therefore, the thickness of the silicon-containing layer is preferably less than one atomic layer to several atomic layers.

[Step 2]
When the silicon-containing film is formed for a predetermined time and a silicon-containing layer having a predetermined thickness is formed on the wafer 200, the controller 280 closes the valve 243e of the third gas supply pipe 232c and stops the supply of the HCD gas. At this time, the APC valve 242 of the gas exhaust pipe 231 is kept open, the processing chamber 201 is evacuated by the vacuum pump 246, and the remaining HCD gas is removed from the processing chamber 201 (residual gas removal). At this time, if an inert gas is supplied into the processing chamber 201, the effect of removing the residual gas is further enhanced.

[Step 3]
After the residual gas in the processing chamber 201 is removed, the controller opens the valve 243g of the fourth gas supply pipe 232d and the valve 243d of the second inert gas supply pipe 234b, and supplies the film forming gas to the fourth gas supply pipe 232d. An inert gas is passed through the NH ₃ gas and the second inert gas supply pipe 234b. The NH ₃ gas is supplied from the fourth gas supply pipe 232d, and the flow rate is adjusted by the mass flow controller 241g. The inert gas is supplied from the second inert gas supply pipe 234b, and the flow rate is adjusted by the mass flow controller 241d. The NH ₃ gas whose flow rate has been adjusted is mixed with the inert gas whose flow rate has been adjusted in the second inert gas supply pipe 234b, and is heated from the gas supply hole 248b of the second nozzle 233b to be heated in a decompressed processing chamber. The gas is exhausted from the gas exhaust pipe 231 while being supplied into the 201 (NH ₃ gas supply). Note that NH ₃ gas is supplied into the processing chamber 201 without being activated by plasma.

At this time, the controller 280 appropriately adjusts the APC valve 242 to set the pressure in the processing chamber 201 to a pressure in the range of 50 to 3000 Pa, for example. The supply flow rate of NH ₃ gas controlled by the mass flow controller 241b is, for example, a flow rate in the range of 100 to 10,000 sccm. Note that the time for exposing the wafer 200 to the NH ₃ gas is, for example, a time within a range of 1 to 180 seconds.

By supplying NH ₃ gas into the processing chamber 201 under the above-described conditions, the NH ₃ gas is thermally activated in a heated reduced pressure atmosphere. That is, it is activated by non-plasma. A nitriding process is performed on the silicon-containing layer formed on the wafer 200 in step 1 by the activated NH ₃ gas. By this nitriding treatment, the silicon-containing layer is modified into a silicon nitride layer. It is to be noted that the nitriding treatment can proceed more gently when the NH ₃ gas is supplied by being activated by heat than by being activated by plasma.

[Step 4]
After modifying the silicon-containing layer into the silicon nitride layer, the controller 280 closes the valve 243g of the fourth gas supply pipe 232d and stops the supply of NH ₃ gas. At this time, the APC valve 242 of the gas exhaust pipe 231 is kept open, the process chamber 201 is evacuated by the vacuum pump 246, and the remaining NH ₃ gas is removed from the process chamber 201 (residual gas removal). At this time, if an inert gas is supplied into the processing chamber 201, the effect of removing the residual gas is further enhanced.

  The above-described steps 1 to 4 are set as one cycle, and this cycle is repeated a plurality of times to grow a silicon nitride film having a predetermined thickness on the wafer 200.

  When a silicon nitride film having a predetermined thickness is formed, the inside of the processing chamber 201 is purged with the inert gas (purge) by exhausting the inert gas while being supplied into the processing chamber 201.

  Thereafter, the inside of the processing chamber 201 is adjusted to a predetermined oxidation processing pressure. At this time, the pressure in the processing chamber 201 is measured by the pressure sensor 245, and the controller 280 performs feedback control of the APC valve 242 based on the measured pressure (pressure adjustment). Further, the inside of the processing chamber 201 is adjusted to a predetermined oxidation processing temperature. At this time, based on the temperature information detected by the temperature sensor 263 so that the inside of the processing chamber 201 has a desired temperature distribution, the controller 280 feedback-controls the power supply to the heater 207 (temperature adjustment).

Subsequently, the controller 280 opens the valve 243a of the first gas supply pipe 232a and the valve 243c of the first inert gas supply pipe 234a, and supplies the O ₂ gas and the first inert gas supply pipe 234a to the first gas supply pipe 232a. Flow inert gas through O ₂ gas is supplied from the first gas supply pipe 232a, and the flow rate is adjusted by the mass flow controller 241a. The inert gas is supplied from the first inert gas supply pipe 234a, and the flow rate is adjusted by the mass flow controller 241c. The O ₂ gas whose flow rate has been adjusted is mixed with the inert gas whose flow rate has been adjusted in the first gas supply pipe 232a, and is heated from the gas supply hole 248a of the first nozzle 233a into the heated processing chamber 201 in a reduced pressure state. Is exhausted from the gas exhaust pipe 231. At the same time, the controller 280 opens the valve 243b of the second gas supply pipe 232b and the valve 243d of the second inert gas supply pipe 234b, and supplies the H ₂ gas and the second inert gas supply pipe 234b to the second gas supply pipe 232b. Flow inert gas through The inert gas flows from the second inert gas supply pipe 234b, and the flow rate is adjusted by the mass flow controller 241d. The H ₂ gas flows from the second gas supply pipe 232b and the flow rate is adjusted by the mass flow controller 241b. The H ₂ gas whose flow rate has been adjusted is mixed with the inert gas whose flow rate has been adjusted in the second gas supply pipe 232b, and is heated from the gas supply hole 248b of the second nozzle 233b into the heated processing chamber 201 in a reduced pressure state. Are exhausted from the gas exhaust pipe 231 (O ₂ gas and H ₂ gas supply). Note that the O ₂ gas and the H ₂ gas are supplied into the processing chamber 201 without being activated by plasma.

At this time, the controller 280 appropriately adjusts the APC valve 242 to maintain the pressure in the processing chamber 201 at a pressure lower than the atmospheric pressure, for example, within a range of 0.1 to 1000 Pa. The supply flow rate of O ₂ gas controlled by the mass flow controller 241a is, for example, a flow rate within a range of 20 sccm to 10000 sccm (10 slm). The supply flow rate of H ₂ gas controlled by the mass flow controller 241b is, for example, a flow rate in the range of 10 sccm to 5000 sccm (5 slm). The time for exposing the wafer 200 to the O ₂ gas and the H ₂ gas is determined according to the amount of oxidation on the surface of the silicon nitride film. The temperature of the heater 207 is set so that the temperature of the wafer 200 becomes a temperature within a range of 400 to 1000 ° C., for example. It has been confirmed that if the temperature is within this range, the effect of improving the oxidizing power by adding H ₂ gas to O ₂ gas in a reduced-pressure atmosphere can be obtained. In order to obtain this effect, the temperature in the processing chamber 201 needs to be 350 ° C. or higher. However, the temperature in the processing chamber 201 is preferably 400 ° C. or higher, and more preferably 450 ° C. or higher. preferable. If the temperature in the processing chamber 201 is 400 ° C. or higher, an oxidizing power exceeding the oxidizing power by the O ₃ oxidation treatment performed at a temperature of 400 ° C. or higher can be obtained. For example, an oxidizing power exceeding the oxidizing power by the O ₂ plasma oxidation treatment performed at a temperature of 450 ° C. or higher can be obtained.

By supplying O ₂ gas and H ₂ gas into the processing chamber 201 under the above-described conditions, the O ₂ gas and H ₂ gas are activated and reacted in a heated reduced-pressure atmosphere, whereby atomic oxygen Oxidized species such as O are produced. Then, an oxidation treatment is performed on the silicon nitride film formed on the wafer 200 mainly by this oxidation species. Thereby, the surface layer portion of the silicon nitride film is modified into silicon oxynitride (SiO _x N _y ) or silicon oxide (SiO _x ).

  After oxidizing the surface layer portion of the silicon nitride film having a predetermined thickness, the inside of the processing chamber 201 is purged with the inert gas (purge) by exhausting while supplying the inert gas into the processing chamber 201. Thereafter, the atmosphere in the processing chamber 201 is replaced with an inert gas, and the pressure in the processing chamber 201 is returned to normal pressure (return to atmospheric pressure).

  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 unloaded). Thereafter, the processed wafer 200 is taken out from the boat 217 (wafer discharge).

  Then, the processed wafer 200 is transferred to an etching apparatus, and the surface layer portion of the silicon nitride film formed on the wafer 200 is removed by etching.

  As described above, in this embodiment, the silicon nitride film forming step and the oxidation treatment step are continuously performed in the same apparatus. However, it is possible to save the trouble of transporting to another apparatus and improve the throughput. Can do. The substrate on which the silicon nitride film is formed may be accommodated in the processing chamber 201 and the oxidation process may be performed. Note that the silicon nitride film forming step and the oxidation treatment step may be performed in separate apparatuses (processing furnaces).

101a silicon substrate 102 silicon oxide film 103 silicon nitride film 104 oxide film 115 boat elevator 200 wafer 201 processing chamber 202 processing furnace 203 process tube 207 heater 217 boat 245 pressure sensor 246 vacuum pump 263 temperature sensor 267 rotating mechanism 280 controller

Claims (2)

A part of the silicon nitride film is supplied by supplying an oxygen-containing gas and a hydrogen-containing gas into the processing chamber in a state where the pressure in the processing chamber containing the substrate on which the silicon nitride film is formed is lower than the atmospheric pressure. A step of oxidizing
Removing the oxidized portion of the silicon nitride film;
A method for manufacturing a semiconductor device, comprising: After forming a silicon nitride film on the substrate surface by supplying a film forming gas into the processing chamber containing the substrate, an oxygen-containing gas and a hydrogen-containing gas in the processing chamber in a state where the pressure in the processing chamber is lower than the atmospheric pressure. And oxidizing a part of the silicon nitride film;
Removing the oxidized portion of the silicon nitride film;
A method for manufacturing a semiconductor device, comprising:

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