JP2007273686A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device capable of stably assuring a high film-formation rate when forming an ozone TEOS film with a CVD device, and capable of forming an ozone TEOS film in good film quality and uniformity. <P>SOLUTION: In the method of manufacturing a semiconductor device, an interlayer dielectric is formed on a semiconductor substrate where a wiring structure is formed. The method includes: a first interlayer dielectric formation step of forming a plasma CVD silicon oxide film on the semiconductor substrate where a wiring structure is formed, a surface reforming step of performing plasma-processing for surface reforming of the plasma CVD silicon oxide film formed in the first interlayer dielectric formation step; and a second interlayer dielectric formation step of forming an ozone TEOS film on the plasma CVD silicon oxide film whose surface has been reformed in the surface reforming step. In the surface reforming step, the deposites in the device for plasma-processing are removed before the plasma-processing for surface reforming. <P>COPYRIGHT: (C)2008,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 in which an interlayer insulating film is formed on a semiconductor substrate on which a wiring structure is formed and planarization is performed.

As semiconductor devices have been highly integrated and densified in recent years, planarization techniques for alleviating the increasing surface step are becoming increasingly important. At present, silane-based CVD films and TEOS-based plasma CVD films are mainly used as interlayer insulating films, but overhang shapes and voids have been generated with miniaturization. For this reason, TEOS-O ₃ -based atmospheric pressure CVD films that can obtain a reflow shape during film formation have come to be used.

However, the TEOS-O ₃ -based atmospheric pressure CVD film is highly dependent on the base material, and, for example, the deposition rate is slower on a silicon oxide film such as a thermal oxide film or an HTO film than on WSi or Poly-Si. There is a problem that a good embedding shape cannot be obtained due to deterioration of the surface morphology.

In order to solve such a problem, various surface modification techniques for eliminating the base dependency of the TEOS-O ₃ system atmospheric pressure CVD film and performing good embedding have been disclosed. For example, Patent Document 1 discloses a method for performing surface modification by irradiating a substrate with high frequency plasma while the substrate is heated as a method for canceling the substrate dependency. Further, Patent Document 2, while applying a low frequency power and high frequency power to the first electrode and the second electrode, the N ₂ gas into a plasma state between the first electrode and the second electrode A method of performing surface modification by performing irradiation is disclosed. In the method described in Patent Document 2, in the method described in Patent Document 1, an insulating film is formed on a dense surface step in the submicron device, and further, a TEOS-O ₃ atmospheric pressure CVD film ( Hereinafter, when an attempt is made to form and embed an "ozone TEOS film"), a void is generated and a good embedment characteristic cannot be obtained. By using the method of Patent Document 2, even a dense surface step in a submicron device can be embedded without voids, and high-quality film characteristics can be obtained.
JP-A-4-94539 JP-A-8-203891

  However, even when the methods described in Patent Document 1 and Patent Document 2 are used, when the ozone TEOS film is formed by a CVD apparatus, the film formation rate becomes slow or the film thickness is in-plane. In some cases, the uniformity was extremely deteriorated.

  Accordingly, the present invention provides a semiconductor device capable of stably securing a high film formation rate and forming an ozone TEOS film with good uniformity and good quality when forming an ozone TEOS film with a CVD apparatus. It aims at providing the manufacturing method of.

  Even when using the methods described in Patent Document 1 and Patent Document 2 described above, the present inventors have found that when the ozone TEOS film is formed by a CVD apparatus, the film formation rate becomes slow, The cause of the extremely in-plane uniformity of the wafer was investigated. When conducting a surface modification process using a plasma CVD apparatus having parallel plate electrodes during the examination, for example, in order to suppress the oxide film deposited during the CVD film formation and dust generation in the CVD apparatus. When an oxide film such as a precoat film is deposited, the inventors have found the fact that the above-described phenomenon occurs in which the film formation rate decreases and the in-plane uniformity deteriorates. Therefore, the oxide film deposited in the CVD apparatus is removed before the surface modification process is performed, and then the surface modification process is performed without deposits in the apparatus. I understood.

The present invention has been made based on the above findings and has the following characteristics.
[1] A method of manufacturing a semiconductor device in which an interlayer insulating film is formed on a semiconductor substrate on which a wiring structure is formed, wherein a plasma CVD silicon oxide film is formed on the semiconductor substrate on which the wiring structure is formed. An interlayer insulation film forming step, a surface modification step for performing plasma treatment for surface modification of the plasma CVD silicon oxide film formed by the first interlayer insulation film formation step, and a surface modification step by the surface modification step. A second interlayer insulating film forming step of forming an ozone TEOS film on the plasma CVD silicon oxide film subjected to the modification, and in the surface modification step, plasma for surface modification Before performing the treatment, deposits accumulated in the apparatus for performing the plasma treatment are removed.
[2] In the method of manufacturing a semiconductor device according to [1], removal of deposits deposited in the plasma CVD apparatus by the first interlayer insulating film forming step after the first interlayer insulating film forming step is performed. A surface removal step, and a pre-coating step of depositing a plasma CVD silicon oxide film having a predetermined thickness in the plasma CVD apparatus from which the deposit has been removed by the deposit removal step. The removal of deposits deposited in the apparatus prior to the plasma treatment in (1) is to remove the plasma CVD silicon oxide film deposited by the pre-coating process.

  According to the present invention, when forming an ozone TEOS film with a CVD apparatus, it is possible to stably ensure a high film formation rate and to form an ozone TEOS film with good uniformity and good film quality. A method of manufacturing a device is provided.

  Hereinafter, an example of the best mode for carrying out the present invention will be described.

  FIG. 1 is an explanatory view for explaining a method of manufacturing a semiconductor device according to the present invention, and is a cross-sectional view showing a process of forming an interlayer insulating film on a semiconductor substrate on which a wiring structure is formed.

  FIG. 1A is a diagram in which a wiring structure 2 including a laminated wiring composed of an Al alloy film 2 a and an antireflection film 2 b such as TiN is provided on a semiconductor substrate 1. Here, as the Al alloy film 2a and the antireflection film 2b, those usually used in a semiconductor process can be used and are not particularly limited.

FIG. 1B shows a plasma CVD film 3 formed on the semiconductor substrate 1 on which the wiring structure 2 shown in FIG. 1A is formed as a first interlayer insulating film forming step. . Here, as the plasma CVD film 3, a plasma TEOS-CVD film having good step coverage is generally used (the following is mainly described in the case of a plasma TEOS-CVD film), but is not limited thereto. Instead, a SiH ₄ plasma CVD film or other insulating film may be used.

FIG. 1C is a diagram showing a surface modification process in which the surface of the plasma CVD film 3 formed in the first interlayer insulating film formation process is treated with plasma as a surface modification process. Here, the plasma treatment is preferably performed using N ₂ gas or NH ₃ gas in a plasma state. The plasma processing conditions are, for example, high frequency (13.56 MHz) 700 W, pressure 667 Pa, gas flow rate N ₂ = 1500 sccm, NH ₃ = 100 sccm, temperature 400 ° C., and processing time is about 30 seconds. .

FIG. 1D is a diagram in which an ozone TEOS film 4 is formed on the plasma CVD film 3 whose surface has been modified by the surface modification process as the second interlayer insulating film formation process. is there. Note that the ozone TEOS film is deposited under the conditions of, for example, a gas flow rate of O ₃ = 80 g / m ³ , O ₂ = 0.008 sccm, TEOS = 0.0018 sccm, N ₂ = 0.018 sccm, and a temperature of 415 ° C. The film thickness is 200 nm to 400 nm.

  Here, the present invention further removes deposits deposited in the apparatus for performing the plasma treatment before performing the plasma treatment for the surface modification in the surface modification step.

FIG. 2 is an explanatory diagram for explaining an example of a method for removing deposits deposited in an apparatus for performing plasma processing, and is a view showing a cross section of the apparatus for performing plasma processing. In FIG. 2, a case where a plasma TEOS-CVD apparatus is used as the apparatus for performing the plasma processing will be described. However, the present invention is not limited to this, and a SiH ₄ -based plasma CVD or other apparatus is used. Also good.

Hereinafter, a procedure for removing deposits deposited in the plasma TEOS-CVD apparatus will be described with reference to FIG. 2, but the same applies to the case of using a SiH ₄ -based plasma CVD apparatus.

  As shown in FIG. 2, the plasma TEOS-CVD apparatus 5 includes an upper electrode 7 and a lower electrode 8 in a CVD reaction chamber 6. A high frequency is applied to the upper electrode 7, and the lower electrode 8. Is grounded. Then, as shown in FIG. 2A, a material gas is introduced into the CVD reaction chamber 6 from a gas introduction system (not shown), and a high frequency is applied to the upper electrode 7. The material gas is turned into plasma, and a plasma TEOS-CVD film 3 ′ as a first interlayer insulating film is formed on the semiconductor substrate 9 placed on the lower electrode 8.

  The semiconductor substrate 9 on which the plasma TEOS-CVD film 3 ′ as the first interlayer insulating film is formed is carried out of the CVD reaction chamber 6 after film formation. FIG. 2B is a view showing a state in the CVD reaction chamber 6 after the semiconductor substrate 9 after film formation is unloaded. As shown in the drawing, a plasma TEOS-CVD film 3 ′ is deposited in the CVD reaction chamber 6, particularly on the electrodes 7 and 8, in a portion other than the semiconductor substrate 9.

Next, as shown in FIG. 2 (c), as a deposit removal step, a cleaning gas is introduced into the CVD reaction chamber 6, and the gas is turned into plasma, whereby the plasma TEOS-CVD deposited in the chamber. Remove the membrane. Here, the cleaning time and the like are adjusted according to the thickness of the plasma TEOS-CVD film formed on the semiconductor substrate 9. As cleaning conditions and the like, for example, C ₂ F ₆ is used as the cleaning gas, gas flow rates are C ₂ F ₆ = 600 sccm, O ₂ = 650 sccm, high frequency (13.56 MHz) 900 W, and pressure is 400 Pa.

  Next, as shown in FIG. 2D, as a pre-coating process, the plasma TEOS-CVD film deposited in the chamber by the deposit removing process is removed, and a plasma having a predetermined film thickness is formed in the CVD reaction chamber 6. A CVD film 10 is deposited (pre-coated). Fine dust particles are scattered in the CVD reaction chamber 6 immediately after the deposit removal process is performed. A thin oxide film is deposited in the CVD reaction chamber 6 for the purpose of suppressing the particles so that the particles do not adhere to the next semiconductor substrate to be formed. This is a process called pre-coating, and this process also has a role of stabilizing the next film formation.

  Here, as the film thickness of the plasma CVD film 10 to be precoated, it is necessary to suppress the scattering particles and to stabilize the next film formation, and therefore the film thickness is usually about 100 nm. It is preferable that

  Next, as shown in FIG. 2E, the plasma CVD film 10 pre-coated by the pre-coating process is removed. Here, the pre-coated plasma CVD film can be removed by the same method as the deposit removing step.

  In addition, since the film thickness to be precoated is almost constant and this is a thin plasma CVD film, it is possible to remove the precoated film with certain short time processing. It becomes.

  As described above, first, the inside of the CVD reaction chamber 6 after the deposition of the plasma TEOS-CVD film as the first interlayer insulating film is cleaned, and pre-coating is performed by a pre-coating process, and then the pre-coated plasma is further performed. By performing the procedure of removing the CVD film, the following effects are obtained.

  That is, in the conventional method, the plasma TEOS-CVD film as the first interlayer insulating film is formed thicker than the thickness of the precoat film as described above, and the film thickness is also set for each process. Different. Therefore, in the cleaning step in the CVD reaction chamber 6 after the deposition of the plasma TEOS-CVD film which is the first interlayer insulating film, a part of the surface in the chamber 6 to which the insulating film is not attached is applied. However, there is a risk of unnecessary cleaning. In that case, the exposed surface of the chamber 6 is damaged by being exposed to plasma, and there is a risk of generating a large amount of particles. Therefore, when the semiconductor substrate for performing the surface modification process in this state is charged into the CVD reaction chamber 6, particles may adhere to the surface of the semiconductor substrate.

  On the other hand, in the present invention, since the film thickness of the precoat film is almost constant, the time for removing it can also be made constant. Therefore, the above unnecessary cleaning is not performed. Therefore, after removing the precoat film, there is little possibility that particles adhere to the surface of the semiconductor substrate even when the semiconductor substrate to be subjected to the surface modification process is inserted into the CVD reaction chamber 6. For this reason, it is preferable to use the above procedure. That is, in order to avoid the risk of performing cleaning on a part of the surface to which the insulating film is not attached, after pre-coating by the pre-coating process, the procedure of further removing the pre-coated plasma CVD film is performed. is necessary.

  Next, as shown in FIG. 2F, a semiconductor substrate 9 for surface modification is inserted into the CVD reaction chamber 6 from which the precoat film has been removed, and the semiconductor substrate 9 is used as a surface modification step. The surface of the plasma TEOS-CVD film 3 that is the first interlayer insulating film formed on the surface of the film is treated with plasma. The plasma treatment method for surface modification is as described above.

  Next, as a second interlayer insulating film formation step, an ozone TEOS film is formed on the plasma TEOS-CVD film 3 whose surface has been modified by the surface modification step. The method for forming the ozone TEOS film is as described above.

An example of a processing procedure when the plasma TEOS-CVD film forming step, the deposit removing step, the pre-coating step, the pre-coating film removing step, and the surface modifying step are performed in the same apparatus. It is shown below. The following processing procedure is an example of a procedure for processing N semiconductor substrates (wafers) as one lot by using a single wafer type CVD apparatus, but is not limited to this. Various processing procedures can be taken depending on the configuration, operating conditions, operating conditions, and the like.
(1) First, the first wafer is placed inside the CVD reaction chamber to form a plasma TEOS-CVD film (plasma TEOS-CVD film formation process).
(2) Next, the wafer is taken out from the CVD reaction chamber, and the deposit in the CVD reaction chamber from which the wafer has been taken out is removed (deposit removal step).
(3) Next, a precoat film is deposited in the CVD reaction chamber from which deposits have been removed (precoat step).
(4) The second wafer is loaded into the CVD reaction chamber on which the precoat film is deposited, and the processing from (1) above is repeated.
(5) After the above process is repeated up to the Nth sheet, the precoat film is removed in the precoat process performed after the Nth wafer is unloaded from the CVD reaction chamber (precoat film removal process). .
(6) The wafer on which the plasma TEOS-CVD film has been formed according to (1) above is loaded into the CVD reaction chamber from which the precoat film has been removed, and surface modification of the plasma TEOS-CVD film is performed. Perform (surface modification step).
(7) Next, the wafer is taken out from the CVD reaction chamber, and surface modification is performed on the second wafer on which the plasma TEOS-CVD film is formed.
(8) The above (7) is repeated up to the Nth wafer on which the plasma TEOS-CVD film is formed.
(9) End of 1 lot.

  The procedure for performing the plasma TEOS-CVD film forming step, the deposit removing step, the pre-coating step, the pre-coating film removing step and the surface modification step in the same apparatus has been described above. However, it is not limited to the case where it is performed within the same apparatus, and may be performed using different apparatuses. The important point in the present invention is that, in the surface modification step, before the plasma treatment for the surface modification is performed, deposits deposited in the apparatus for performing the plasma treatment, for example, the formation of the CVD film in this apparatus Remove the oxide film deposited during the pre-coating and the oxide film during the pre-coating to suppress dust generation in the CVD device, and then modify the surface without deposits in the device. The plasma treatment is performed.

  As a result, when the ozone TEOS film is formed in the subsequent second interlayer insulating film forming step, a high film formation rate is stably ensured, and an ozone TEOS film having good uniformity and good film quality is formed. It becomes possible.

  Note that the formation of the ozone TEOS film as the second interlayer insulating film may be performed continuously in a chamber in which the surface modification process is performed, or may be performed by a different apparatus.

  The same conditions except that the lot (1) to (9) as an example of the present invention and the steps (1) to (9) as a comparative example are not performed (5). Thereafter, the film formation rate of the ozone TEOS film and the uniformity of the ozone TEOS film within the wafer surface were evaluated.

The conditions for forming the ozone TEOS film were the same in the following examples for both the inventive example and the comparative example. That is, the deposition conditions for the ozone TEOS film were as follows: gas flow rates of O ₃ = 80 g / m ³ , O ₂ = 0.008 sccm, TEOS = 0.0018 sccm, N ₂ = 0.018 sccm, and a temperature of 415 ° C.

  As a result, the deposition rate of the ozone TEOS film was 1.3 times that of the comparative example in the case of the present invention. The film formation rate was calculated by measuring the film thickness after film formation and dividing this by the film formation time.

  Further, when the in-wafer uniformity of the ozone TEOS film was evaluated, in the case of the example of the present invention, for example, the electrode on which the precoat film 100 nm was formed was subjected to plasma treatment by cleaning for 100 nm. In this case, the film thickness variation of the ozone TEOS (4000 mm) film was 2.5%. On the other hand, as a comparative example, when only cleaning for 50 nm was performed, the film thickness variation was 5%, and a tendency of deterioration was observed.

  Such a tendency that the film thickness uniformity in the wafer surface deteriorates (i.e., an increase in film thickness variation) occurs when the cleaning of the electrode is insufficient or when it is performed halfway. .

  Further, the film thickness variation in the wafer surface is calculated by the following equation by measuring the film thickness at nine points in the wafer surface.

Variation in film thickness = (maximum film thickness value−minimum film thickness value) / (maximum film thickness value + minimum film thickness value) × 100
From the above, it was confirmed that application of the present invention greatly improved both the deposition rate of the ozone TEOS film and the uniformity within the wafer surface.

It is explanatory drawing for demonstrating the manufacturing method of the semiconductor device which concerns on this invention, and is sectional drawing which showed the process of forming an interlayer insulation film on the semiconductor substrate in which the wiring structure was formed. It is explanatory drawing for demonstrating an example of the method of removing the deposit deposited in the apparatus which performs plasma processing based on this invention, and is the figure which showed the cross section of the apparatus which performs plasma processing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Wiring structure 3 Plasma CVD film 4 Ozone TEOS film 5 Plasma TEOS-CVD apparatus 6 CVD reaction chamber 7 Upper electrode 8 Lower electrode 9 Semiconductor substrate

Claims (2)

A method of manufacturing a semiconductor device, wherein an interlayer insulating film is formed on a semiconductor substrate on which a wiring structure is formed,
A first interlayer insulating film forming step of forming a plasma CVD silicon oxide film on the semiconductor substrate on which the wiring structure is formed;
A surface modification step for performing plasma treatment for surface modification of the plasma CVD silicon oxide film formed by the first interlayer insulating film formation step;
A second interlayer insulating film forming step of forming an ozone TEOS film on the plasma CVD silicon oxide film whose surface has been modified by the surface modifying step;
Further, in the surface modification step, before the plasma treatment for surface modification is performed, deposits deposited in the apparatus for performing the plasma treatment are removed. A deposit removing step of removing deposits deposited in the plasma CVD apparatus by the first interlayer insulating film forming step after the first interlayer insulating film forming step;
A pre-coating step of depositing a plasma CVD silicon oxide film having a predetermined film thickness in the plasma CVD apparatus from which the deposit is removed by the deposit removing step;
The removal of the deposit deposited in the apparatus performed before the plasma treatment in the surface modification step is to remove the plasma CVD silicon oxide film deposited in the precoat step. A method for manufacturing a semiconductor device.

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