JP2006156666A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device manufacturing method removing off a deposit attached on the surface of a substrate sufficiently. <P>SOLUTION: An Si oxide film 2 and an Si nitride film 3 are successively formed on an Si substrate 1. Then, a resist mask 4 which discloses a part where an element isolation region is provided is formed on the Si nitride film 3. Then, the Si nitride film 3 and the Si oxide film 2 are subjected to an etching process. The above etching process is carried out using, for instance, a magnetic field-applied plane parallel plate dry etching device. As the result of this etching, a deposit film 5 is formed on the Si substrate 1. The deposit film 5 is mainly formed of fluorocarbon. Thereafter, the internal pressure of a chamber provided to the magnetic field-applied plane parallel plate dry etching device is set at 3.3 kPa or so, the intensity of a magnetic field is set at 2 mT or so, and an RF power is set at 200 W or so. SF<SB>6</SB>gas is fed into the chamber at a flow rate of 10 sccm or so. A processing time is set at 10 seconds or so. As the result of this processing, the deposit film 5 is completely removed off without producing a by-product. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor device that improves the cleanliness of a substrate.

Conventionally, there is shallow trench isolation (STI) as one method of insulation isolation. In STI, it is necessary to etch a Si substrate after forming a mask on the Si substrate. Further, since a deposition film is formed on the Si substrate when the mask is formed, it is necessary to remove it. In this removal, CF ₄ is often used as a cleaning gas. CF ₄ dissociates into a CF ₃ radical and an F radical, and the F radical mainly acts as a cleaning species.

  However, in such a conventional method, the surface of the Si substrate cannot be sufficiently cleaned, and a deposit film may remain. When the deposition film remains, the bottom of the trench formed for STI is not flat, and it becomes difficult to obtain desired characteristics.

JP 2002-64089 A Japanese Patent Laid-Open No. 10-233387 Japanese Patent Laid-Open No. 2004-87738 JP 2002-367960 A Japanese Patent Publication No. 6-38406 JP 2004-71996 A

  An object of this invention is to provide the manufacturing method of the semiconductor device which can fully remove the deposit | attachment on the substrate surface.

As a result of searching for the reason why the surface of the Si substrate cannot be sufficiently cleaned even by the conventional method, the inventors of the present application have adsorbed the CF ₃ radical on the surface of the Si substrate to form a polymer layer. I found out. And based on this knowledge, as a result of intensive studies to solve the above-mentioned problems, the inventors have arrived at the following aspects of the invention.

  In the method for manufacturing a semiconductor device according to the present invention, after a film is formed on a semiconductor substrate, the film is patterned to expose a part of the semiconductor substrate. Then, the semiconductor substrate is cleaned in a plasma atmosphere using a fluorine compound gas not containing carbon as a process gas.

  According to the present invention, the semiconductor substrate can be cleaned while suppressing the generation of by-products. For this reason, the deposits on the substrate surface can be sufficiently removed.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. 1A to 1H are cross-sectional views showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps.

  In this embodiment, first, as shown in FIG. 1A, a Si oxide film 2 and a Si nitride film 3 are sequentially formed on a Si substrate 1. The thicknesses of the Si oxide film 2 and the Si nitride film 3 are, for example, 12 nm and 120 nm, respectively. Next, a resist mask 4 is formed on the Si nitride film 3 to expose a portion where an element isolation region is to be formed.

  Next, as shown in FIG. 1B, the Si nitride film 3 and the Si oxide film 2 are etched. This etching is performed using, for example, a magnetic field application type parallel plate dry etching apparatus as shown in FIG. In the magnetic field application type parallel plate dry etching apparatus, electrodes 102 and 103 are disposed in a chamber 101 so as to face each other. A wafer such as the Si substrate 1 is placed on the electrode 102. A power source 104 is connected to the electrodes 102 and 103. Further, a magnet 105 is provided outside the chamber 101. In such an apparatus, plasma can be generated between the electrodes 102 and 103.

When etching the Si nitride film 3 and the Si oxide film 2, for example, the pressure in the chamber 101 is set to about 4 kPa (30 mTorr), the magnetic field strength is set to about 1 mT (10 G), and the RF power is set to about 400 W. Further, CHF ₃ gas and O ₂ gas are supplied into the chamber 101 at a flow rate of about 70 sccm and 6 sccm, respectively. The etching time is about 60 seconds, for example. As a result, a deposition film 5 is formed on the Si substrate 1 as shown in FIG. 1B. The deposition film 5 is a film containing, for example, fluorocarbon as a main component.

Thereafter, the pressure in the chamber 101 of the magnetic field applied parallel plate dry etching apparatus is set to about 3.3 kPa (25 mTorr), the magnetic field strength is set to about 2 mT (20 G), and the RF power is set to about 200 W. In addition, SF ₆ gas is supplied into the chamber 101 at a flow rate of about 10 sccm. The processing time is about 10 seconds, for example. As a result of this treatment, as shown in FIG. 1C, the deposition film 5 is completely removed without generating by-products.

In the conventional method, cleaning is performed using CF ₄ gas. However, as described above, since new deposits are generated, sufficient cleaning cannot be performed. On the other hand, in the present embodiment, since SF ₆ gas not containing carbon is used without using CF ₄ gas containing carbon, new deposits are not generated, and sufficient cleaning is performed. Can do.

Subsequently, as shown in FIG. 1D, the trench 6 is formed by etching the Si substrate 1 using the resist mask 4 as a mask. When the trench 6 is formed, for example, the pressure in the chamber 101 is set to about 11.3 kPa (85 mTorr), the magnetic field strength is set to about 2 mT (20 G), and the RF power is set to about 400 W. In addition, HBr gas, Cl ₂ gas, and CF ₄ gas are supplied into the chamber 101 at flow rates of about 90 sccm, 10 sccm, and 40 sccm, respectively. The etching time is about 155 seconds, for example.

  Next, as shown in FIG. 1E, the resist mask 4, the Si nitride film 3, and the Si oxide film 2 are removed. Note that the resist mask 4 may be removed before the trench 6 is formed. In this case, for example, the trench 6 can be formed by etching the Si substrate 1 using the Si nitride film 3 as a hard mask.

  Next, as shown in FIG. 1F, an element isolation insulating film 7 is embedded in the trench 6.

  Thereafter, as shown in FIG. 1G, a gate insulating film 8, a gate electrode 9, and an impurity diffusion layer 10 are formed in the element active region partitioned by the element isolation insulating film 7. That is, a MOS transistor is formed.

  Subsequently, as shown in FIG. 1F, an interlayer insulating film 11 is formed on the entire surface, contact holes are formed in the interlayer insulating film 11, and contact plugs 12 are embedded therein. Further, a wiring 13 connected to the contact plug 12 is formed on the interlayer insulating film 11. Then, an upper layer wiring or the like is formed to complete the semiconductor device.

  According to the first embodiment, since the secondary reaction does not occur when the deposition film 5 is removed, the surface of the Si substrate 1 can be sufficiently cleaned. That is, the deposition film 5 can be removed while avoiding the regeneration of the polymer layer. Therefore, the flatness of the bottom portion of the trench 6 to be formed thereafter is sufficient.

FIG. 3A shows an SEM photograph (scanning electron micrograph) of a trench actually formed according to the above-described embodiment. For comparison, FIG. 3B shows an SEM photograph of a trench formed by a conventional method. In forming the trench shown in FIG. 3B, CF ₄ gas was supplied into the chamber 101 at a flow rate of about 10 sccm in order to remove the deposition film. The other conditions were matched with the conditions for forming the trench shown in FIG. 3A.

  As is clear from a comparison between FIG. 3A and FIG. 3B, in the conventional method, a large number of needle-like residues were present at the bottom of the trench (FIG. 3B). This is because the surface of the Si substrate is not sufficiently cleaned before the trench is formed, and etching of this portion is delayed. If such a residue is present, for example, electric field concentration is likely to occur, and the withstand voltage becomes insufficient. On the other hand, in the method according to the embodiment of the present invention, no acicular residue was present (FIG. 3A).

The process gas used for removing the deposition film is not limited to SF ₆ gas, and any fluorine compound gas not containing carbon such as NF ₃ gas can be used. Further, O ₂ gas may be contained in the process gas.

  Further, the present invention can be applied not only to cleaning before etching the Si substrate, but also to cleaning the Si substrate after forming contact holes, for example.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1)
Forming a film on a semiconductor substrate;
Exposing the part of the semiconductor substrate by patterning the film;
A step of cleaning the semiconductor substrate in a plasma atmosphere using a fluorine compound gas containing no carbon as a process gas;
A method for manufacturing a semiconductor device, comprising:

(Appendix 2)
_{2. The} method of manufacturing a semiconductor device according to appendix 1, wherein a gas further containing O ₂ gas is used as the process gas.

(Appendix 3)
_{3. The} method of manufacturing a semiconductor device according to appendix 1 or 2, wherein at least one gas selected from the group consisting of SF ₆ gas and NF ₃ gas is used as the fluorine compound gas.

(Appendix 4)
4. The semiconductor device according to claim 1, further comprising a step of forming a resist mask on the film between the step of forming the film and the step of patterning the film. Production method.

(Appendix 5)
The method of manufacturing a semiconductor device according to any one of appendices 1 to 4, wherein a Si oxide film and a Si nitride film are sequentially formed as the film.

(Appendix 6)
After the step of performing the cleaning,
Etching the semiconductor substrate with the film remaining, thereby forming a trench;
Embedding an insulating film in the trench;
The method for manufacturing a semiconductor device according to any one of appendices 1 to 5, wherein:

(Appendix 7)
7. The method of manufacturing a semiconductor device according to any one of appendices 1 to 6, wherein the cleaning is performed in a magnetic field applied parallel plate dry etching apparatus.

It is sectional drawing which shows the manufacturing method of the semiconductor device which concerns on embodiment of this invention to process order. FIG. 1B is a cross-sectional view illustrating the manufacturing method of the semiconductor device in order of processes following FIG. 1A. FIG. 2B is a cross-sectional view illustrating the manufacturing method of the semiconductor device in order of processes following FIG. 1B. FIG. 2D is a cross-sectional view illustrating the manufacturing method of the semiconductor device in order of processes following FIG. 1C. FIG. 2D is a cross-sectional view illustrating the manufacturing method of the semiconductor device in order of processes following FIG. 1D. FIG. 2E is a cross-sectional view showing the manufacturing method of the semiconductor device in order of processes following FIG. 1E. FIG. 2D is a cross-sectional view illustrating the manufacturing method of the semiconductor device in order of processes following FIG. 1F. FIG. 2D is a cross-sectional view illustrating the manufacturing method of the semiconductor device in order of processes following FIG. 1G. It is a schematic diagram which shows a magnetic field application type parallel plate dry etching apparatus. It is a SEM photograph which shows the trench formed with the method according to embodiment of this invention. It is a SEM photograph which shows the trench formed with the conventional method.

Explanation of symbols

1: Si substrate 2: Si oxide film 3: Si nitride film 4: Resist mask 5: Deposition film 6: Trench 7: Element isolation insulating film 8: Gate insulating film 9: Gate electrode 10: Impurity diffusion layer 11: Interlayer insulating film 12: Contact plug 13: Wiring

Claims (5)

Forming a film on a semiconductor substrate;
Exposing the part of the semiconductor substrate by patterning the film;
A step of cleaning the semiconductor substrate in a plasma atmosphere using a fluorine compound gas containing no carbon as a process gas;
A method for manufacturing a semiconductor device, comprising: The method for manufacturing a semiconductor device according to claim 1, wherein the process gas further contains an O ₂ gas. As the fluorine compound gas, a method of manufacturing a semiconductor device according to claim 1 or 2, characterized by using at least one gas selected from the group consisting of SF ₆ gas and NF ₃ gas.   4. The semiconductor device according to claim 1, further comprising a step of forming a resist mask on the film between the step of forming the film and the step of patterning the film. 5. Manufacturing method.   5. The method of manufacturing a semiconductor device according to claim 1, wherein a Si oxide film and a Si nitride film are sequentially formed as the film. 6.

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