JP2012079762A - Insulation film forming apparatus and formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation film forming apparatus and a formation method capable of improving step coverage and insulation quality.SOLUTION: An insulation film forming apparatus and a formation method perform: a film formation step of supplying a main material gas and an auxiliary material gas used to form an insulation film for coating a step formed on a substrate, generating a plasma including an excited species whose deposition probability for the substrate is lower than a main excited species for plasma generation, and forming a precursor film on the step using the plasma; and a composition ratio reduction step (nitriding step) of supplying the auxiliary material gas, generating a plasma for the auxiliary material gas, and reducing the components of the main material gas from the precursor film using the plasma to form an insulation film after the film formation step. The insulation film forming apparatus and the formation method alternately perform the film formation step and the composition ratio reduction step.

Description

  The present invention relates to an insulating film forming apparatus and method.

  In a semiconductor device such as a semiconductor device, an insulating film such as a silicon oxide film or a silicon nitride film is used, and is formed using a plasma CVD (Chemical Vapor Deposition) apparatus or the like.

JP 2010-066793 A

  When a step necessary for manufacturing a semiconductor device is covered with a silicon nitride film (SiN film) which is one of insulating films, when a conventional plasma CVD apparatus is used, the step coverage as shown in FIG. It becomes. Specifically, in the trench 31 (step) having a high aspect ratio (for example, 10: 1) formed in the substrate 30, the thickness of the SiN film 33 on the side wall portion 32 is reduced, and the thickness of the thin portion is reduced. Insulation performance deteriorates. The reason why the thickness of the SiN film 33 is reduced in the side wall portion 32 is that the gas contributing to the film formation adheres to the side wall 32, so that the gas contributing to the film formation is formed in the side wall 32 in the deep portion of the trench 31. This is because the amount reached is reduced. Further, as shown in FIG. 9B, the higher the gas deposition probability to the side wall 32, the thinner the side wall 32 becomes.

In a conventional plasma CVD apparatus, in the case of a film forming method using SiH ₄ , N ₂ , and NH ₃ as raw materials, an excited species having a high adhesion probability, for example, SiH ₂ is used to form a SiN film having excellent insulation. It is necessary to use a condition in which (NH ₂ ) [adhesion probability: 0.08] occurs frequently. However, as described above, the gas having a higher adhesion probability has a property that the film thickness on the side wall becomes thinner, and sufficient step coverage cannot be obtained (refer to Conventional Example 2 in Table 1 described later).

On the other hand, when an excited species having a low adhesion probability, for example, SiH ₃ [adhesion probability: 0.05] is used, the step coverage is improved, but the film composition becomes Si-rich, resulting in a problem that the insulating property is lowered. (See Conventional Example 1 in Table 1 to be described later).

  As described above, in the conventional film formation method in the plasma CVD apparatus, it is difficult to achieve both step coverage and insulation.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an insulating film forming apparatus and method that improve the insulation as well as the step coverage.

An insulating film forming apparatus according to a first invention for solving the above-mentioned problems is as follows.
In an insulating film forming apparatus for forming an insulating film covering a step formed on a substrate,
A gas supply means for supplying a plurality of gases, including a main source gas containing Si and a sub-source gas not containing Si;
Plasma generating means for generating plasma of the gas;
Control means for controlling the gas supply means and the plasma generation means,
The control means includes
At least the main raw material gas is supplied by the gas supply means, and the plasma generation means generates plasma containing excited species having a lower probability of adhesion to the substrate than the main excited species at the time of plasma generation, and uses the plasma A film forming step for forming a precursor film on the step,
After the film formation step, the auxiliary material gas is supplied by the gas supply unit, the plasma of the auxiliary material gas is generated by the plasma generation unit, and the composition ratio of Si in the precursor film is generated using the plasma. The composition ratio reducing step is performed by reducing the thickness of the insulating film.

An insulating film forming apparatus according to a second invention for solving the above-mentioned problems is as follows.
In the insulating film forming apparatus according to the first invention,
The control means is characterized in that the film forming step and the composition ratio decreasing step are alternately performed a plurality of times.

An insulating film forming apparatus according to a third invention for solving the above-mentioned problems is as follows.
In the insulating film forming apparatus according to the first or second invention,
Furthermore, bias application means for applying a bias to the substrate,
The control means includes
In the composition ratio decreasing step, a bias is applied to the substrate by the bias applying means.

An insulating film forming apparatus according to a fourth invention for solving the above-mentioned problems is as follows.
In the insulating film forming apparatus according to the third invention,
The control means includes
Before the composition ratio reduction step,
A rare gas is supplied by the gas supply means, a bias is applied to the substrate by the bias application means, a plasma of the rare gas is generated by the plasma generation means, and the precursor film is sputter etched using the plasma. A sputter etch process is performed.

An insulating film forming apparatus according to a fifth invention for solving the above-mentioned problems is as follows.
In the insulating film forming apparatus according to the third invention,
The control means includes
After the composition ratio reduction step,
A rare gas is supplied by the gas supply means, a bias is applied to the substrate by the bias application means, a plasma of the rare gas is generated by the plasma generation means, and the insulating film is sputter etched using the plasma. A sputter etch process is performed.

An insulating film forming apparatus according to a sixth invention for solving the above-described problems is as follows.
In the insulating film forming apparatus according to any one of the first to fifth inventions,
When the insulating film is a silicon nitride film,
SiH ₄ is used as the main source gas,
Using at least one of NH ₃ or N ₂ as the auxiliary source gas,
SiH ₃ is generated as an excited species having a low adhesion probability.

An insulating film forming method according to a seventh invention for solving the above-described problems is as follows.
In an insulating film forming method for forming an insulating film covering a step formed on a substrate,
Supplying at least the main source gas out of the main source gas containing Si and the auxiliary source gas not containing Si, and generating plasma containing excited species having a lower adhesion probability to the substrate than the main excited species at the time of plasma generation And a film forming step of forming a precursor film on the step using the plasma,
After the film forming step, the auxiliary material gas is supplied, plasma of the auxiliary material gas is generated, and the composition ratio of Si in the precursor film is reduced by using the plasma to form an insulating film. And a reduction process.

An insulating film forming method according to an eighth invention for solving the above-described problems is as follows.
In the insulating film forming method according to the seventh invention,
The film forming step and the composition ratio decreasing step are alternately performed a plurality of times.

An insulating film forming method according to a ninth invention for solving the above-described problems is as follows.
In the insulating film forming method according to the seventh or eighth invention,
In the composition ratio reduction step, a bias is applied to the substrate.

An insulating film forming method according to a tenth invention for solving the above-mentioned problems is as follows.
In the insulating film forming method according to the ninth invention,
A sputter etch step of supplying a rare gas, applying a bias to the substrate, generating a plasma of the rare gas, and sputter-etching the precursor film using the plasma;
The sputter etching process is performed before the composition ratio decreasing process.

An insulating film forming method according to an eleventh invention for solving the above problem is as follows:
In the insulating film forming method according to the ninth invention,
A sputter etch step of supplying a rare gas, applying a bias to the substrate, generating a plasma of the rare gas, and sputter-etching the insulating film using the plasma;
The sputter etching process is performed after the composition ratio decreasing process.

An insulating film forming method according to a twelfth invention for solving the above-described problem is
In the insulating film forming method according to any one of the seventh to eleventh inventions,
When the insulating film is a silicon nitride film,
SiH ₄ is used as the main source gas,
Using at least one of NH ₃ or N ₂ as the auxiliary source gas,
SiH ₃ is generated as an excited species having a low adhesion probability.

  According to the first and seventh inventions, an insulating film having both step coverage and good insulating properties can be formed as the insulating film covering the step.

  According to the second and eighth inventions, an insulating film having a desired thickness can be formed on the side wall of the step.

  According to the third and ninth inventions, in the composition ratio reduction step, the reaction rate can be promoted to shorten the time.

  According to the fourth and tenth aspects of the present invention, in the film forming process, blockage near the entrance of the step can be prevented, and the step coverage can be further improved, and the composition ratio decreasing step after the sputter etching step The time can be shortened.

  According to the fifth and eleventh aspects, blockage in the vicinity of the step entrance can be prevented in the film forming process, and the step coverage can be further improved.

  According to the sixth and twelfth inventions, a silicon nitride film having good step coverage and high insulation can be formed as the insulating film covering the steps.

It is a schematic structure figure showing an example of an embodiment of an insulating film formation device concerning the present invention. 3 is a time chart showing an example (Example 1) of an insulating film forming method in the insulating film forming apparatus shown in FIG. FIGS. 3A and 3B are diagrams illustrating a process of forming a silicon nitride film by the insulating film forming method illustrated in FIG. 2, where FIG. 3A is a cross-sectional view of a step before formation, FIG. c) is a cross-sectional view of the step in the nitriding step, and (d) is a cross-sectional view of the step after the entire process is repeated a plurality of times. It is a graph explaining another example (Example 2) of the insulating film formation method which concerns on this invention. It is a time chart explaining other examples (Example 3) of the insulating film formation method which concerns on this invention. FIGS. 6A and 6B are diagrams illustrating a process of forming a silicon nitride film by the insulating film forming method illustrated in FIG. 5, in which FIG. 5A is a cross-sectional view of a step in a film forming process, and FIG. (C) is sectional drawing of the level | step difference in a nitriding process, (d) is sectional drawing of the level | step difference after repeating all the processes in multiple times. It is a time chart explaining other examples (Example 4) of the insulating film formation method concerning this invention. 8A and 8B are diagrams illustrating a process of forming a silicon nitride film by the insulating film forming method illustrated in FIG. 7, in which FIG. 7A is a cross-sectional view of a step in a film forming process, and FIG. (C) is sectional drawing of the level | step difference in a sputter etching process, (d) is sectional drawing of the level | step difference after repeating all the processes in multiple times. It is a figure explaining the level | step difference coverage in the conventional plasma CVD apparatus, (a) is a case where a sticking probability is 0.1, (b) is a case where a sticking probability is 0.8.

  Hereinafter, embodiments of an insulating film forming apparatus and a forming method according to the present invention will be described with reference to FIGS.

Example 1
FIG. 1 is a schematic configuration diagram showing an example of an embodiment of an insulating film forming apparatus according to the present invention.
The insulating film forming apparatus of this embodiment is a so-called plasma CVD apparatus. Specifically, as shown in FIG. 1, the inside of a metal cylindrical vacuum chamber 1 is configured as a processing chamber 2, and a circular opening made of an insulating material is formed in the upper opening of the vacuum chamber 1. A plate-like ceiling board 3 is disposed so as to close the upper opening. A lower support 10 that holds the support 4 and the support 4 is provided below the vacuum chamber 1, and a substrate 5 (for example, Si wafer) made of a semiconductor material is placed on the upper surface of the support 4. . The vacuum chamber 1 is made of, for example, a metal such as aluminum, and the inner wall thereof is anodized, and the ceiling plate 3 is made of, for example, ceramics such as alumina.

  A high-frequency antenna 6 composed of, for example, a plurality of circular rings is disposed above the ceiling plate 3, and a high-frequency (RF) with a frequency of several hundred kHz to several hundred MHz is connected to the high-frequency antenna 6 via a matching unit 7. ) A power source 8 is connected (plasma generating means). The vacuum chamber 1 is provided with a plurality of gas nozzles 9 for introducing a plurality of desired gases into the processing chamber 2 (gas supply means).

  An electrode unit 11 is provided on the support table 4 that supports the substrate 5, and a low frequency (LF) power source 13 is connected to the electrode unit 11 via a matching unit 12. The low frequency power supply 13 is configured to apply a lower frequency than that of the high frequency power supply 8 to the electrode portion 11 and to apply a bias power to the substrate 5 (bias applying means). Although not shown, the support table 4 is also provided with an electrostatic chuck mechanism, and the substrate 5 can be attracted and held on the surface of the support table 4 by power supply from the electrostatic chuck power source. ing. In addition, although not shown, the insulating film forming apparatus of this embodiment also includes a control device (control means) for controlling the above-described plasma generation means, gas supply means, and bias application means.

In the insulating film forming apparatus configured as described above, by supplying RF power to the high-frequency antenna 6, electromagnetic waves are incident on the vacuum chamber 1 through the ceiling plate 3 and introduced into the vacuum chamber 1 through the gas nozzle 9. The gas is turned into plasma by the incident electromagnetic wave. And the thin film is formed on the board | substrate 5 using the process gas converted into plasma. For example, when forming a SiN film, a process gas such as silane (SiH ₄ ), ammonia (NH ₃ ), nitrogen (N ₂ ) or the like is used.

  The insulating film forming apparatus having the above configuration is an example, and any other structure may be used as long as it is a plasma CVD apparatus capable of performing the insulating film forming method of the present embodiment described later. For example, a plasma generating unit, a gas supplying unit, etc. Various configurations can be applied.

Next, the insulating film forming method of this embodiment will be described.
In this embodiment, in order to form an insulating film that achieves both step coverage and good insulation for a step with a high aspect ratio in a semiconductor device (for example, a trench), the following outline is given. I'm doing some ingenuity. Specifically, first, in the insulating film forming apparatus having the above-described configuration, excited species having a low adhesion probability to the substrate surface are selected from the main source gas (containing Si) and the auxiliary source gas (containing no Si) used for forming the insulating film. A precursor film having good step coverage with respect to a step is formed by generating plasma containing the plasma and performing film formation using the plasma. Thereafter, the formed precursor film is subjected to plasma processing using the plasma of the auxiliary material gas, and the Si composition ratio is reduced from the precursor film, thereby forming an insulating film having high insulating properties.

  Hereinafter, as an example, the case where the step is a trench (aspect ratio = 10: 1) and the insulating film is a silicon nitride film (SiN film) is described with reference to the time chart of FIG. 2 and the cross-sectional view of FIG. The method for forming the insulating film of the example will be described in detail. FIG. 3A illustrates the trench 20 formed in the substrate 5 with a depth of 10 μm and a width of 1 μm. However, the step is not limited to the trench, and may be a step having another shape. The film is not limited to a silicon nitride film, and may be a silicon oxide film (SiO film), a silicon oxynitride film (SiON film), or the like.

In the insulating film forming method of this embodiment, first, a film forming process is performed.
In this film forming process, a gas nozzle 9 is used to supply SiH ₄ gas (main raw material gas) and NH ₃ gas (sub raw material gas) used for forming the SiN film, and plasma generating means (high frequency antenna 6, matching unit). 7. Using a high-frequency power source 8), SiH ₃ [attachment probability: 0.05], which is an excitation species having a lower adhesion probability to the substrate 5 than SiH ₂ (NH ₂ ) [0.08], which is the main excitation species, is used. At the same time, a plasma is generated so as to include more of the excited species than the main excited species, and a precursor film 22 is formed in the trench 20 using the plasma (FIGS. 2, 3A, and 3B). )reference).

At this time, it is important to generate a plasma containing a large amount of excited species SiH ₃ having a low adhesion probability. If a large amount of excited species SiH ₃ can be generated, even if only SiH ₄ gas is supplied as shown in Table 1 described later. Good. Further, in place of the NH ₃ gas, may be supplied with N ₂ gas, may be supplied with N ₂ gas with NH ₃ gas.

In this film forming process, plasma containing excited species SiH ₃ having a low adhesion probability is used, so that a decrease in the amount of excited species SiH ₃ contributing to film formation on the side wall 21 in the deep portion of the trench 20 is suppressed. As a result, a decrease in the film thickness of the precursor film 22 formed on the side wall 21 is also suppressed, and the step coverage can be improved (see FIGS. 3A and 3B). ). However, the precursor film 22 is Si-rich in the film composition (particularly when only the SiH ₄ gas is supplied), and the insulating property is not high in that state.

Therefore, in the insulating film forming method of this embodiment, a nitriding process (composition ratio decreasing process) is performed after the film forming process.
In this nitriding step, NH ₃ gas (or N ₂ gas), which is an auxiliary material gas, is supplied using a gas nozzle 9, and NH ₃ gas is supplied using plasma generation means (high frequency antenna 6, matching unit 7, high frequency power source 8). A plasma of ₃ gas (or N ₂ gas) is generated, and the Si composition ratio is reduced by using the plasma to form the SiN film 23 (see FIGS. 2 and 3C). That is, by nitriding the precursor film 22 having good step coverage but not high insulation with NH ₃ gas (or N ₂ gas) plasma, the Si composition ratio is reduced, and the step coverage is improved. The SiN film 23 is good and has high insulating properties.

  Then, a film forming process with good step coverage and a nitriding process with good insulation are alternately performed at least once to form a SiN film 23 having a desired film thickness on the side wall 21 of the trench 20. (See FIG. 3D). By passing through the process mentioned above, the SiN film 23 having a desired film thickness with good step coverage and high insulation can be formed.

Some of the process conditions of the present embodiment are illustrated and described in Experimental Examples 1 to 3 in Table 1 described later. One film formation process takes 2 seconds, and a precursor film 22 having a thickness of 0.1 nm is formed during this process. Further, as shown in Experimental Examples 1 to 3 in Table 1, the RF power conditions in the film forming process are 0.5 kW, 1.5 kW, and 4 kW, respectively, and the gas flow rate ratio [NH ₃ / (SiH ₄ + NH _3]. )] Was set to 0 or more and 0.2 or less, 0 or more and 0.35 or less, and 0 or more and 0.5 or less, respectively. In Experimental Examples 1 to 3, when changing the gas flow rate ratio, the flow rate of NH ₃ gas was changed by fixing the flow rate of SiH ₄ gas = 60 sccm.

One nitridation step is 180 seconds, and the precursor film 22 is nitrided with plasma of NH ₃ gas (or N ₂ gas). The RF power conditions at this time may be the same as the conditions in the film forming process, or may be changed as appropriate. Further, the flow rate conditions of the NH ₃ gas (or N ₂ gas), if used in the film forming step, in the case may be as flow rate, was only SiH ₄ gas, NH ₃ gas (or N ₂ gas) must be supplied at an appropriate flow rate. Under the same conditions, the film thickness that can be nitrided with NH ₃ gas plasma is 0.3 nm, the film thickness that can be nitrided with N ₂ gas plasma is 0.5 nm, and N ₂ gas is more NH ₃ gas. Thicker film that can be nitrided than gas.

  With respect to the film thickness of the inner wall of the trench, Experimental Examples 1 to 3 of this example and Conventional Examples 1 and 2 are compared. At this time, using the pattern substrate on which the trench 20 was formed, both the experimental examples 1 to 3 of this example and the conventional examples 1 and 2 were formed so that the film thickness on the surface of the substrate 5 was 30 nm. In Experimental Examples 1 to 3 of this example, the film formation process and the nitridation process are alternately repeated about 60 to 100 times to form a film. When the cross-sectional structure of the film obtained by the film formation is examined, in the conventional example, the thickness is 5 nm on the side wall 21 having a depth of 4 μm from the surface of the substrate 5 (FIG. 3 ( d) (see dotted line 24 in Table 1 and Conventional Example 2 in Table 1) In this example, it can be confirmed that the film thickness is 7 nm on the side wall 21 having a depth of 4 μm from the surface of the substrate 5 and the step coverage is good. (See FIG. 3D, Experimental Examples 1 to 3 in Table 1).

In addition, when the insulating properties were compared (film resistance was evaluated by forming a SiN film on a flat substrate), in the case of this example, all were 1 × 10 ¹⁴ Ω · m, and the conventional examples shown in Table 1 were used. It was confirmed that the insulating properties were higher than those of 1 and 2 (see Experimental Examples 1 to 3 and Conventional Examples 1 and 2 in Table 1).

  In Table 1, as well as Experimental Examples 1 to 3 and Conventional Examples 1 and 2 of this example, and Comparative Examples 1 and 2, film formation only in the film forming process of this example, that is, of this example Film formation without a nitriding step was also performed, and the step coverage and insulating properties of the film obtained by this film formation were also evaluated. In Comparative Examples 1 and 2, similarly to Conventional Examples 1 and 2, the step coverage and good insulation are not compatible. On the other hand, in this embodiment, as shown in Experimental Examples 1 to 3, both step coverage and good insulation can be achieved.

(Example 2)
This embodiment is based on the first embodiment. Therefore, the description of the present embodiment will be described with the description overlapping with that of the first embodiment, for example, the configuration of the insulating film forming apparatus and the basic portion of the insulating film forming method (film forming process, nitriding process) are omitted.

  In the present embodiment, a bias is applied to the substrate 5 using bias applying means (electrode unit 11, matching unit 12, low frequency power supply 13) in the nitriding step described in the first embodiment. By applying a bias to the substrate 5, ions and electrons in the plasma are irradiated to the substrate 5, and by applying energy to the precursor film 22 obtained in the film forming process, the nitriding reaction is promoted. ing.

  FIG. 4 is a graph obtained by standardizing the nitriding rate at each LF power, assuming that LF = 0 W, that is, the nitriding rate is 1 when no bias is applied to the substrate 5. As shown in FIG. 4, it can be seen that the nitriding rate is faster when LF = 30 W, 60 W, and 180 W than when LF = 0 W. On the other hand, when LF = 250 W, the nitriding rate is the same as when LF = 0 W, and when LF = 300 W, the nitriding rate is slower than when LF = 0 W. This is because as the LF power increases, the amount of sputter etch increases and does not contribute to the nitriding rate. Accordingly, the LF power is preferably 250 W or less, which is less affected by the sputter etch amount. Thus, in the nitriding step, by applying a bias to the substrate 5, the nitriding rate can be increased, and the nitriding time, in other words, the nitriding step can be shortened. For example, when LF = 30 W, the nitriding rate is about 1.1 times that when LF = 0 W, and the time can be reduced by about 10%.

Note that the substrate evaluated in FIG. 4 has a diameter of 300 mm (30 cm). Therefore, when the diameter of the substrate are different, in terms of the above 250W to the LF power density (W / cm ²⁾ per substrate area (approximately 0.35W / cm ^2.), Such LF power density A bias power as described below may be applied according to the substrate diameter (substrate area).

(Example 3)
This embodiment is also based on the first embodiment. Therefore, as in the second embodiment, the description overlapping with the first embodiment is omitted, and the present embodiment will be described. Note that the present embodiment may be based on the second embodiment.

  In this embodiment, a sputter etch process is added between the film forming process and the nitriding process described in the first embodiment. Specifically, as shown in the time chart of FIG. 5, the sputter etch process is performed after the film formation process and before the nitriding process. This is the same even when the film forming process and the nitriding process are repeated a plurality of times.

  In this sputter etching process, a rare gas such as Ar is supplied using a gas nozzle 9, and a bias is applied to the substrate 5 using bias applying means (electrode unit 11, matching unit 12, low frequency power supply 13). Then, plasma generation means (high frequency antenna 6, matching unit 7, high frequency power supply 8) is used to generate a rare gas plasma, and the precursor film 22 obtained in the film forming process using the plasma is sputter etched. Is going.

Each step shown in FIG. 5 will be described with reference to FIG. The precursor film 22 is formed in the trench 20 using the film formation process described in the first embodiment (see FIG. 6A). In this film forming process, plasma containing excited species SiH ₃ having a low adhesion probability is used. However, an overhang portion 22 a is still formed in the precursor film 22 near the entrance of the trench 20. In order to further improve the step coverage, it is preferable that the overhang portion 22a is small (thin film thickness is thin).

  Therefore, in the present embodiment, the overhang portion 22a is sputter-etched using a rare gas, for example, Ar gas plasma, by performing a sputter etch process after the film formation process is completed. The hang portion 22a is removed to prevent the vicinity of the entrance of the trench 20 (see FIG. 6B). In this sputter etch process, in order to increase the sputter etch amount, unlike the second embodiment, the LF power is also increased, for example, LF = 1500 W. By using such LF power, more ions and electrons in the plasma are irradiated onto the substrate 5 to increase the amount of sputter etch. However, since the overhang portion 22a to be shaved by sputter etching is thin, the sputter etching time does not have to be long, for example, about 0.1 second.

  Thereafter, using the nitriding step described in the first embodiment, the precursor film 22 formed in the trench 20 is nitrided to form the SiN film 23 (see FIG. 6C). Then, the film forming process, the sputter etching process, and the nitriding process are performed at least once in this order to form the SiN film 23 having a desired film thickness on the side wall 21 of the trench 20 (FIG. 6 ( d)).

  By passing through the process mentioned above, since the film thickness in the side wall 21 of the trench 20 becomes still thicker, the step coverage is further improved, and the SiN film 23 having a desired film thickness with high insulation can be formed. In particular, in the case of the present embodiment, since the sputter etching process is performed before the nitriding process, the film thickness to be nitrided in the nitriding process is reduced, so that the time in the nitriding process can be shortened.

Example 4
This embodiment is also based on the first embodiment. Therefore, as in the second embodiment, the description overlapping with the first embodiment is omitted, and the present embodiment will be described. This embodiment may also be based on the second embodiment. Further, this embodiment corresponds to a modification of the third embodiment.

  In this embodiment, as shown in the time chart of FIG. 7, the sputter etch process is performed after the nitriding process described in the first embodiment is completed. That is, the order of adding the sputter etch process is different from that of the third embodiment. This is the same even when the film forming process and the nitriding process are repeated a plurality of times.

  Also, in the sputter etch process of the present embodiment, a rare gas (for example, Ar) is supplied and a bias is applied to the substrate 5 to generate a rare gas plasma. Sputter etching of the SiN film 23 obtained after the nitriding process is performed using plasma.

  Each step shown in FIG. 7 will be described with reference to FIG. The precursor film 22 is formed in the trench 20 using the film forming process described in the first embodiment (see FIG. 8A), and then the trench 20 is formed using the nitriding process described in the first embodiment. The precursor film 22 thus formed is nitrided to form a SiN film 23 (see FIG. 8B).

In this film forming process, plasma containing excited species SiH ₃ having a low adhesion probability is used. However, an overhang portion 22a is still formed in the precursor film 22 near the entrance of the trench 20, and in the nitriding process, Since the precursor film 22 is nitrided, an overhang portion 23 a is formed near the entrance of the trench 20. In order to further improve the step coverage, it is preferable that the overhang portion 23a is small (thin film thickness is thin).

  Therefore, in the present embodiment, the overhang portion 23a is sputter-etched by using a rare gas, for example, Ar gas plasma, by performing a sputter etch process after the nitridation process is completed. The portion 23a is removed to prevent the vicinity of the entrance of the trench 20 (see FIG. 8C). Again, since the overhang portion 23a to be shaved by sputter etching is thin, the sputter etching time does not have to be long, for example, about 0.1 seconds.

  Then, the film forming process, the nitriding process, and the sputter etching process are performed at least once in this order to form the SiN film 23 having a desired film thickness on the side wall 21 of the trench 20 (FIG. 8 ( d)). By passing through the process mentioned above, since the film thickness in the side wall 21 of the trench 20 becomes still thicker, the step coverage is further improved, and the SiN film 23 having a desired film thickness with high insulation can be formed.

  The present invention is applied to a semiconductor device, and is particularly suitable as an insulating film covering a step having a high aspect ratio.

DESCRIPTION OF SYMBOLS 5 Substrate 6 High frequency antenna 7 Matching device 8 High frequency power supply 9 Gas nozzle 11 Electrode part 12 Matching device 13 Low frequency power supply 20 Trench 21 Side wall 22 Precursor film 22a Overhang part 23 SiN film 23a Overhang part

Claims (12)

In an insulating film forming apparatus for forming an insulating film covering a step formed on a substrate,
A gas supply means for supplying a plurality of gases, including a main source gas containing Si and a sub-source gas not containing Si;
Plasma generating means for generating plasma of the gas;
Control means for controlling the gas supply means and the plasma generation means,
The control means includes
At least the main raw material gas is supplied by the gas supply means, and the plasma generation means generates plasma containing excited species having a lower probability of adhesion to the substrate than the main excited species at the time of plasma generation, and uses the plasma A film forming step for forming a precursor film on the step,
After the film formation step, the auxiliary material gas is supplied by the gas supply unit, the plasma of the auxiliary material gas is generated by the plasma generation unit, and the composition ratio of Si in the precursor film is generated using the plasma. An insulating film forming apparatus is characterized in that a composition ratio reducing step is performed in which the composition ratio is reduced to form an insulating film. In the insulating film forming apparatus according to claim 1,
The said control means implements the said film-forming process and the said composition ratio reduction process alternately several times, The insulating film formation apparatus characterized by the above-mentioned. In the insulating film forming apparatus according to claim 1 or 2,
Furthermore, bias application means for applying a bias to the substrate,
The control means includes
In the composition ratio decreasing step, a bias is applied to the substrate by the bias applying means. In the insulating film forming apparatus according to claim 3,
The control means includes
Before the composition ratio reduction step,
A rare gas is supplied by the gas supply means, a bias is applied to the substrate by the bias application means, a plasma of the rare gas is generated by the plasma generation means, and the precursor film is sputter etched using the plasma. An insulating film forming apparatus that performs a sputter etching process. In the insulating film forming apparatus according to claim 3,
The control means includes
After the composition ratio reduction step,
A rare gas is supplied by the gas supply means, a bias is applied to the substrate by the bias application means, a plasma of the rare gas is generated by the plasma generation means, and the insulating film is sputter etched using the plasma. An insulating film forming apparatus that performs a sputter etching process. In the insulating film forming apparatus according to any one of claims 1 to 5,
When the insulating film is a silicon nitride film,
SiH ₄ is used as the main source gas,
Using at least one of NH ₃ or N ₂ as the auxiliary source gas,
An insulating film forming apparatus, wherein SiH ₃ is generated as an excited species having a low adhesion probability. In an insulating film forming method for forming an insulating film covering a step formed on a substrate,
Supplying at least the main source gas out of the main source gas containing Si and the auxiliary source gas not containing Si, and generating plasma containing excited species having a lower adhesion probability to the substrate than the main excited species at the time of plasma generation And a film forming step of forming a precursor film on the step using the plasma,
After the film forming step, the auxiliary material gas is supplied, plasma of the auxiliary material gas is generated, and the composition ratio of Si in the precursor film is reduced by using the plasma to form an insulating film. An insulating film forming method comprising: a reducing step. The insulating film forming method according to claim 7,
The method for forming an insulating film, wherein the film forming step and the composition ratio decreasing step are alternately performed a plurality of times. In the insulating film formation method according to claim 7 or 8,
In the composition ratio reduction step, a bias is applied to the substrate. In the insulating film formation method according to claim 9,
A sputter etch step of supplying a rare gas, applying a bias to the substrate, generating a plasma of the rare gas, and sputter-etching the precursor film using the plasma;
An insulating film forming method, wherein the sputter etching step is performed before the composition ratio reducing step. In the insulating film formation method according to claim 9,
A sputter etch step of supplying a rare gas, applying a bias to the substrate, generating a plasma of the rare gas, and sputter-etching the insulating film using the plasma;
An insulating film forming method, wherein the sputter etching process is performed after the composition ratio decreasing process. In the insulating film formation method according to any one of claims 7 to 11,
When the insulating film is a silicon nitride film,
SiH ₄ is used as the main source gas,
Using at least one of NH ₃ or N ₂ as the auxiliary source gas,
A method of forming an insulating film, wherein SiH ₃ is generated as an excited species having a low adhesion probability.

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