JP2007129060A - Method and apparatus for manufacturing semiconductor device, control program, and computer storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device manufacturing method or the like for preventing occurrence of roughness on the surface of a silicon nitride film, while obtaining a high selection ratio of the silicon nitride film to a silicon oxide film. <P>SOLUTION: A polysilicon film 102, the silicon oxide film 103, and the silicon nitride film 104 are formed on a silicon substrate 101. Plasma etching is executed from that state. The silicon nitride film 104 is etched so as to leave the silicon nitride film 104 only around the polysilicon film 102. In an etching gas, at least a C<SB>m</SB>F<SB>n</SB>(m and n are respectively an integer of ≥1) gas having a flow rate of ≤10% of that of an O<SB>2</SB>gas is added to a mixed gas including a CH<SB>x</SB>F<SB>y</SB>(x and y are respectively an integer of ≥1) gas and the O<SB>2</SB>gas. The etching gas is used for the plasma etching. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor device manufacturing method, a semiconductor device manufacturing apparatus, a control program, and a computer storage medium including a step of selectively plasma etching a silicon nitride film with respect to a silicon oxide film.

Conventionally, in a manufacturing process of a semiconductor device, a silicon nitride film such as a SiN film is selective to a silicon oxide film such as a SiO ₂ film or an SiOC film (oxygen-added silicon oxide film) formed on the lower side. Plasma etching is performed. In such plasma etching, for example, a mixed gas of CH ₃ F and O ₂ is used as an etching gas, and the selectivity of the silicon nitride film to the silicon oxide film in etching (etching rate of silicon nitride film / silicon oxide film A technique for increasing the etching rate is known (for example, see Patent Document 1).
JP 2003-229418 A

As described above, it has been conventionally known that a silicon nitride film is selectively etched with respect to a silicon oxide film by using a mixed gas of CH ₃ F and O ₂ or the like as an etching gas. It is also known to stabilize the plasma by adding a rare gas such as Ar as a diluent gas to such an etching gas.

In the above technique, since O ₂ in the etching gas hardly contributes to the etching of the silicon oxide film, the addition of O ₂ is a factor that increases the selectivity of the silicon nitride film to the silicon oxide film. However, when O ₂ is added in this way to increase the selectivity of the silicon nitride film to the silicon oxide film, a micromask that is presumed to be oxidized on the surface of the silicon nitride film is formed. It has been found that a rough surface having a rough shape occurs, which may lead to deterioration of characteristics in the semiconductor device.

  The present invention has been made in response to the above-described conventional circumstances, and can obtain a high selection ratio of the silicon nitride film to the silicon oxide film and can prevent the surface of the silicon nitride film from being roughened. An object is to provide a semiconductor device manufacturing method, a semiconductor device manufacturing apparatus, a control program, and a computer storage medium.

The method of manufacturing a semiconductor device according to claim 1, wherein a plasma etching step of selectively etching the silicon nitride film with respect to the silicon oxide film on a substrate to be processed in which a silicon nitride film is formed on the silicon oxide film. a method of manufacturing a semiconductor device having, on the plasma etch _{process, CH x F y (x,} y is an integer of 1 or more) in a mixed gas containing a gas and O ₂ gas, the O ₂ gas flow rate A method for manufacturing a semiconductor device, comprising using an etching gas to which C _m F _n (m, n is an integer of 1 or more) gas having a flow rate of 10% or less is used.

  The method for manufacturing a semiconductor device according to claim 2 is the method for manufacturing a semiconductor device according to claim 1, wherein the silicon nitride film is plasma-etched to form a spacer made of the silicon nitride film at the gate. And

A method for manufacturing a semiconductor device according to claim 3 is the method for manufacturing a semiconductor device according to claim 1 or 2, wherein the CH _x F _y (x, y is an integer of 1 or more) gas is CH ₃ F gas or It is characterized by being CH ₂ F ₂ gas.

The method for manufacturing a semiconductor device according to claim 4 is the method for manufacturing a semiconductor device according to any one of claims 1 to 3, wherein the C _m F _n (m and n are integers of 1 or more) gas is C ₂ F ₆ gas, C ₃ F ₈ gas, C ₄ F ₆ gas, C ₄ F ₈ gas, or C ₅ F ₈ gas.

The method for manufacturing a semiconductor device according to claim 5 is the method for manufacturing a semiconductor device according to any one of claims 1 to 4, wherein an amount of the C _m F _n (m and n are integers of 1 or more) gas added. Is 8% or less of the flow rate of the O ₂ gas.

The method for manufacturing a semiconductor device according to claim 6 is the method for manufacturing a semiconductor device according to any one of claims 1 to 4, wherein an amount of the C _m F _n (m and n are integers of 1 or more) gas added. Is 6% or less of the flow rate of the O ₂ gas.

  A method for manufacturing a semiconductor device according to a seventh aspect is the method for manufacturing a semiconductor device according to any one of the first to sixth aspects, wherein the etching gas further contains a rare gas.

9. The semiconductor device manufacturing apparatus according to claim 8, wherein a processing chamber for accommodating a substrate to be processed, an etching gas supply means for supplying the etching gas into the processing chamber, and the etching gas supplied from the etching gas supply means. A plasma generating means for plasma-etching the substrate to be processed and a control section for controlling the semiconductor device manufacturing method according to claim 1 to be performed in the processing chamber; It is provided with.

  A control program according to claim 9 operates on a computer and controls a semiconductor device manufacturing apparatus so that the semiconductor device manufacturing method according to any one of claims 1 to 7 is performed at the time of execution. Features.

  The computer storage medium according to claim 10 is a computer storage medium in which a control program that operates on a computer is stored, and the control program is executed by the semiconductor device according to any one of claims 1 to 7. The semiconductor device manufacturing apparatus is controlled so that the manufacturing method is performed.

  According to the present invention, it is possible to obtain a high selection ratio of the silicon nitride film to the silicon oxide film and to prevent the surface of the silicon nitride film from being roughened.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged view of a cross-sectional configuration of a semiconductor wafer as a substrate to be processed in the semiconductor device manufacturing method according to the present embodiment. FIG. 2 shows the configuration of a plasma etching apparatus as a semiconductor device manufacturing apparatus according to this embodiment. First, the configuration of the plasma etching apparatus will be described with reference to FIG.

  The plasma etching apparatus has a chamber 1 that is hermetically configured and is electrically grounded. The chamber 1 has a cylindrical shape and is made of, for example, aluminum. A support table 2 that horizontally supports a semiconductor wafer 30 as a substrate to be processed is provided in the chamber 1. The support table 2 is made of, for example, aluminum, and is supported by a conductor support 4 via an insulating plate 3. A focus ring 5 made of, for example, single crystal silicon is provided on the outer periphery above the support table 2.

  An RF power source 10 is connected to the support table 2 via a matching box 11. A high frequency power having a predetermined frequency (for example, 13.56 MHz) is supplied from the RF power supply 10 to the support table 2. On the other hand, a shower head 16 is provided in parallel with each other so as to face the support table 2, and the shower head 16 is grounded. Accordingly, the support table 2 and the shower head 16 function as a pair of electrodes.

  An electrostatic chuck 6 for electrostatically adsorbing the semiconductor wafer 30 is provided on the upper surface of the support table 2. The electrostatic chuck 6 is configured by interposing an electrode 6a between insulators 6b, and a DC power source 12 is connected to the electrode 6a. When the DC voltage is applied from the DC power supply 12 to the electrode 6a, the semiconductor wafer 30 is attracted by the Coulomb force.

  A refrigerant flow path (not shown) is formed inside the support table 2, and the semiconductor wafer 30 can be controlled to a predetermined temperature by circulating an appropriate refrigerant therein. An exhaust ring 13 is provided outside the focus ring 5. The exhaust ring 13 is electrically connected to the chamber 1 through the support 4.

  A shower head 16 is provided on the top wall portion of the chamber 1 so as to face the support table 2. The shower head 16 is provided with a large number of gas discharge holes 18 on the lower surface thereof, and has a gas introduction portion 16a on the upper portion thereof. And the space 17 is formed in the inside. A gas supply pipe 15a is connected to the gas introduction part 16a, and a processing gas supply system 15 for supplying a processing gas for etching (etching gas) is connected to the other end of the gas supply pipe 15a.

The processing gas supplied from the processing gas supply system 15 reaches the space 17 inside the shower head 16 via the gas supply pipe 15 a and the gas introduction part 16 a and is discharged toward the semiconductor wafer 30 from the gas discharge hole 18. In the present embodiment, the processing gas supply system 15 supplies at least 10% or less of the O ₂ gas flow rate to the mixed gas containing CH _x F _y (x and y are integers of 1 or more) gas and O ₂ gas. An etching gas to which C _m F _n (m, n is an integer greater than or equal to 1) gas is added, or an etching gas to which a rare gas such as Ar gas or He gas is further added is supplied.

  An exhaust port 19 is formed in the lower portion of the chamber 1, and an exhaust system 20 is connected to the exhaust port 19. The inside of the chamber 1 can be depressurized to a predetermined degree of vacuum by operating a vacuum pump provided in the exhaust system 20. On the other hand, a gate valve 24 for opening and closing the loading / unloading port for the wafer 30 is provided on the side wall of the chamber 1.

  On the other hand, a concentric ring magnet 21 is arranged around the chamber 1 so as to exert a magnetic field on the space between the support table 2 and the shower head 16. The ring magnet 21 can be rotated by a rotating means such as a motor (not shown).

  The operation of the plasma etching apparatus having the above configuration is comprehensively controlled by the control unit 60. The control unit 60 includes a process controller 61 that includes a CPU and controls each unit of the plasma etching apparatus, a user interface 62, and a storage unit 63.

  The user interface 62 includes a keyboard that allows a process manager to input commands to manage the plasma etching apparatus, a display that visualizes and displays the operating status of the plasma etching apparatus, and the like.

  The storage unit 63 stores a recipe in which a control program (software) for realizing various processes executed by the plasma etching apparatus under the control of the process controller 61 and processing condition data are stored. Then, if necessary, an arbitrary recipe is called from the storage unit 63 by an instruction from the user interface 62 and is executed by the process controller 61, so that a desired process in the plasma etching apparatus is performed under the control of the process controller 61. Processing is performed. In addition, recipes such as control programs and processing condition data may be stored in a computer-readable computer storage medium (eg, hard disk, CD, flexible disk, semiconductor memory, etc.), or It is also possible to transmit the data from other devices as needed via a dedicated line and use it online.

  A procedure for selectively performing the plasma etching of the silicon nitride film formed on the semiconductor wafer 30 with respect to the silicon oxide film as the base film by the plasma etching apparatus configured as described above will be described. First, the gate valve 24 is opened, and the semiconductor wafer 30 is loaded into the chamber 1 via a load lock chamber (not shown) by a transfer robot (not shown) and placed on the support table 2. Thereafter, the transfer robot is retracted out of the chamber 1 and the gate valve 24 is closed. Then, the inside of the chamber 1 is exhausted through the exhaust port 19 by the vacuum pump of the exhaust system 20.

  After the inside of the chamber 1 reaches a predetermined degree of vacuum, a predetermined processing gas (etching gas) is introduced into the chamber 1 from the processing gas supply system 15, and the inside of the chamber 1 is maintained at a predetermined pressure, for example, 8.0 Pa. In this state, high frequency power having a frequency of, for example, 13.56 MHz and a power of, for example, 100 to 5000 W is supplied from the RF power source 10 to the support table 2. At this time, a predetermined DC voltage is applied from the DC power source 12 to the electrode 6a of the electrostatic chuck 6, and the semiconductor wafer 30 is adsorbed by Coulomb force.

  In this case, an electric field is formed between the shower head 16 as the upper electrode and the support table 2 as the lower electrode by applying the high frequency power to the support table 2 as the lower electrode as described above. The On the other hand, since a horizontal magnetic field is formed by the ring magnet 21 in the upper part 1a of the chamber 1, magnetron discharge is generated in the processing space where the semiconductor wafer 30 exists due to electron drift, and plasma of the processing gas formed thereby is generated. Thus, the silicon nitride film formed on the semiconductor wafer 30 is etched.

  Then, when the predetermined etching process is completed, the supply of the high frequency power and the supply of the processing gas are stopped, and the semiconductor wafer 30 is carried out of the chamber 1 by a procedure reverse to the procedure described above.

Next, with reference to FIG. 1, a method for manufacturing the semiconductor device according to the present embodiment will be described. FIG. 1A and FIG. 1B are enlarged views of the main configuration of a semiconductor wafer as a substrate to be processed in the present embodiment. In the figure, reference numeral 101 denotes a silicon substrate constituting a semiconductor wafer. A polysilicon film 102 patterned in a predetermined shape is formed at a predetermined portion on the silicon substrate 101. A silicon oxide film (for example, a SiO ₂ film, for example) is formed so as to cover the polysilicon film 102 and the surface of the silicon substrate 101. (SiOC film etc.) 103 is formed. In the state shown in FIG. 1A, a silicon nitride film (eg, SiN film) 104 is formed so as to cover the entire surface of the silicon oxide film 103.

Then, plasma etching is performed from the state shown in FIG. 1A to etch the silicon nitride film 104, leaving the silicon nitride film 104 only around the polysilicon film 102 as shown in FIG. 1B. State. Such a structure is used, for example, when a nitride film spacer is formed at the gate of a semiconductor device. In this plasma etching, C _m F _{n having} a flow rate of 10% or less of the flow rate of O ₂ gas is added to a mixed gas containing at least CH _x F _y (x and y are integers of 1 or more) gas and O ₂ gas. (M and n are integers of 1 or more) An etching gas to which a gas is added or an etching gas to which a rare gas is further added to this etching gas is used.

As CH _x F _y gas, for example, CH ₃ F gas or CH ₂ F ₂ gas can be preferably used. As the C _m F _n gas, for example, it can be suitably used C ₂ F ₆ gas, C ₃ F ₈ gas, C ₄ F ₆ gas, C ₄ F ₈ gas, a C ₅ F ₈ gas or the like . By adding C _m F _n gas, it is possible to prevent the surface of the silicon nitride film from being roughened. However, if the amount of addition is excessive, the selectivity of the silicon nitride film to the silicon oxide film decreases. . Therefore the addition amount of the upper limit of C _m F _n gas is 10% or less of the flow rate of O ₂ gas. Further, from the viewpoint of the selectivity of the silicon nitride film to the silicon oxide film, the amount of C _{m Fn} gas added is preferably 8% or less of the flow rate of O ₂ gas, and more preferably 6% or less. preferable. The lower limit of the amount of C _m F _n gas added is limited by the fact that the lower limit of the gas flow rate control range of the plasma etching apparatus is usually about 1 sccm, etc., but the surface roughness is suppressed by suppressing the oxidation of the silicon nitride film. In order to obtain the effect of preventing, the flow rate is preferably 1% or more of the flow rate of O ₂ gas, more preferably 3% or more. In addition, as a rare gas as a dilution gas, for example, a gas such as He, Ne, Ar, Kr, or Xe can be used.

  As an example, the plasma processing apparatus shown in FIG. 2 was used, and the above-described plasma etching process was performed on the semiconductor wafer having the structure shown in FIG. 1 according to the following recipe.

In addition, the process recipe of the Example shown below is read from the memory | storage part 63 of the control part 60, is taken in by the process controller 61, and the process controller 61 controls each part of a plasma processing apparatus based on a control program. As a result, the etching process according to the read processing recipe is executed.
Etching gas: CH ₃ F / Ar / O ₂ / C ₄ F ₈ = 60/90/38/2 sccm
Pressure: 8.0Pa (60mTorr)
Power: 200W

The etching rate of the silicon nitride film (SiN film) in the plasma etching step is 50.4 nm / min, and the selectivity to the silicon oxide film (SiO ₂ film) (the etching rate of the silicon nitride film / the etching rate of the silicon oxide film) ) Was 11.0. Further, when the surface of the etched silicon nitride film was observed with an electron microscope, as shown in FIG. 1B, the surface of the silicon nitride film 104 was smooth and no roughness was observed. .

As a comparative example, C ₄ F ₈ was not added to the etching gas, and the plasma etching process was performed according to the recipe shown below.
Etching gas: CH ₃ F / Ar / O ₂ = 60/90/32 sccm
Pressure: 6.6 Pa (50 mTorr)
Power: 200W

The etching rate of the silicon nitride film (SiN film) in the plasma etching step is 37.2 nm / min, and the selectivity to the silicon oxide film (SiO ₂ film) (the etching rate of the silicon nitride film / the etching rate of the silicon oxide film). ) Was 11.0. Further, when the surface of the etched silicon nitride film was observed with an electron microscope, as shown in FIG. 3, unevenness 110 having irregularities was generated on the surface of the silicon nitride film 104. .

  As can be seen from the above results, in the above embodiment, the same silicon nitride film to silicon oxide film selection ratio as in the comparative example can be obtained, and the surface roughness of the silicon nitride film as in the comparative example can be obtained. Did not occur.

  As described above, according to the present embodiment, in the plasma etching process in the manufacturing method of the semiconductor manufacturing apparatus, a high selection ratio of the silicon nitride film to the silicon oxide film can be obtained, and the surface of the silicon nitride film is roughened. This can be prevented. In addition, this invention is not limited to said embodiment, Various deformation | transformation are possible. For example, the plasma etching apparatus is not limited to the parallel plate type lower one frequency application type shown in FIG. 2, but includes various types of plasma etching apparatuses such as an upper and lower two frequency application type, a lower two frequency application type plasma etching apparatus, and the like. The plasma etching apparatus can be used.

The figure which shows the cross-sectional structure of the semiconductor wafer which concerns on embodiment of the manufacturing method of the semiconductor device of this invention. The figure which shows schematic structure of the manufacturing apparatus of the semiconductor device which concerns on embodiment of this invention. The figure for demonstrating the surface state of the silicon nitride film in a comparative example.

Explanation of symbols

  101... Silicon substrate 102. Polysilicon film 103. Silicon oxide film 104. Silicon nitride film

Claims (10)

A method for manufacturing a semiconductor device, comprising: a plasma etching step of selectively plasma-etching the silicon nitride film with respect to the silicon oxide film on a substrate to be processed in which a silicon nitride film is formed on the silicon oxide film;
In the plasma etching step, a mixed gas containing CH _x F _y (x, y is an integer of 1 or more) gas and O ₂ gas is mixed with C _m F _n (with a flow rate of 10% or less of the flow rate of the O ₂ gas. m and n are integers greater than or equal to 1) An etching gas added with a gas is used. A method of manufacturing a semiconductor device according to claim 1,
A method of manufacturing a semiconductor device, comprising: plasma-etching the silicon nitride film to form a spacer made of the silicon nitride film at a gate. A method of manufacturing a semiconductor device according to claim 1 or 2,
The method of manufacturing a semiconductor device, wherein the CH _x F _y (x, y is an integer of 1 or more) gas is CH ₃ F gas or CH ₂ F ₂ gas. A method of manufacturing a semiconductor device according to claim 1,
The C _m F _n (m, n is an integer of 1 or more) gas is any of C ₂ F ₆ gas, C ₃ F ₈ gas, C ₄ F ₆ gas, C ₄ F ₈ gas, and C ₅ F ₈ gas. A method for manufacturing a semiconductor device, wherein: A method of manufacturing a semiconductor device according to claim 1,
A method of manufacturing a semiconductor device, wherein the amount of C _m F _n (m, n is an integer of 1 or more) gas is 8% or less of the flow rate of the O ₂ gas. A method of manufacturing a semiconductor device according to claim 1,
A method of manufacturing a semiconductor device, wherein the amount of C _m F _n (m, n is an integer of 1 or more) gas is 6% or less of the flow rate of the O ₂ gas. A method of manufacturing a semiconductor device according to claim 1,
The method for manufacturing a semiconductor device, wherein the etching gas further contains a rare gas. A processing chamber for accommodating a substrate to be processed;
Etching gas supply means for supplying the etching gas into the processing chamber;
Plasma generating means for converting the etching gas supplied from the etching gas supply means into plasma and plasma etching the substrate to be processed;
A semiconductor device manufacturing apparatus, comprising: a control unit that controls the semiconductor device manufacturing method according to claim 1 to be performed in the processing chamber.   8. A control program that operates on a computer and controls a semiconductor device manufacturing apparatus so that the semiconductor device manufacturing method according to claim 1 is performed during execution. A computer storage medium storing a control program that runs on a computer,
8. A computer storage medium, wherein the control program controls a semiconductor device manufacturing apparatus so that the method of manufacturing a semiconductor device according to claim 1 is performed at the time of execution.

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