JP2010103358A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device having a plurality of trenches 3 with different aperture widths that suppresses more variations of a sidewall angle to a surface of a semiconductor substrate 1 in each trench 3 than by a conventional method of manufacturing the same. <P>SOLUTION: The method of manufacturing the semiconductor device includes the steps of: forming a plurality of trenches 3 with different aperture widths corresponding to shapes of masks 2 for a semiconductor substrate 1; carrying out a trench protection film forming process including a process for forming in inner walls of a plurality of the trenches 3 a protection film 5 which is stronger in resistance against reactive ion etching than a polymer film 4 and that for forming a polymer film 4; and deepening the trenches by alternately repeating the trench forming process and trench protection film forming one. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device including a plurality of trenches having different opening widths.

  Conventionally, it is known that a trench is formed in a semiconductor substrate and a semiconductor device is manufactured using the trench. For example, Patent Document 1 previously filed by the present inventors discloses a semiconductor device manufacturing method using the following trench formation method.

First, a semiconductor substrate mainly composed of Si is etched with SF ₆ plasma to form a trench having a predetermined depth, and the inner wall of the formed trench is etched with C ₄ F ₈ plasma. A polymer film forming step for forming a polymer film is performed. Then, after the trench etching process and the polymer film forming process are repeated a plurality of times, the inner wall of the trench is oxidized with higher resistance to etching than the polymer film by irradiating the formed trench with O ₂ plasma. A step of forming a film is performed. Thereafter, a trench bottom etching process is performed in which the oxide film formed on the bottom of the trench is etched to expose the bottom of the trench, and the bottom of the trench is etched again. Subsequently, a polymer film forming process is performed on the formed trench and a trench etching process is performed to deepen the trench. Thereafter, if necessary, a step of repeatedly performing the trench etching step and the polymer film forming step, a step of forming an oxide film on the inner wall of the trench with O ₂ plasma, and a trench bottom etching step are sequentially repeated. The trench is made to the desired depth. Thereafter, the semiconductor device is manufactured by performing a desired semiconductor manufacturing process on the semiconductor substrate.

In such a trench formation method, the resistance to lateral etching can be increased by covering the sidewalls of the trench with a polymer film and an oxide film. And it can suppress that a trench becomes wide by adjusting the film thickness of a polymer film according to the magnitude | size of the opening width of a trench.
JP 2000-299310 A

  However, in the method of manufacturing a semiconductor device described in Patent Document 1, when the trenches having different opening widths are formed simultaneously, the thickness of the oxide film cannot be set for each trench. There is a problem in that the side wall angle varies.

  FIG. 3 is a diagram showing an experimental result when the present inventors simultaneously formed a plurality of trenches having different opening widths on a semiconductor substrate by applying the trench forming method of Patent Document 1 described above. As shown in FIG. 3, the sidewall angle of the trench with respect to the semiconductor substrate surface depends on the opening width, and it can be confirmed that the sidewall angle of the trench increases from 90 degrees as the opening width increases. .

This is due to the following reason. In the trench forming method of Patent Document 1, an oxide film is formed on the inner wall of the trench by O ₂ plasma. Since the oxide film formed by O ₂ plasma is an oxide film formed by oxidizing only the surface layer on the inner wall of the trench, the thickness of the oxide film is constant regardless of the opening width of the trench. Further, the oxide film formed by O ₂ plasma, the thickness of the oxide film for O ₂ plasma as the walls of the trench is deep portion is less likely to reach thinner.

On the other hand, in the etching with SF ₆ plasma, F radicals that affect the etching rate are introduced into the trench depending on the opening width of the trench, and the amount of F radicals introduced into the trench having a larger opening width than a trench having a smaller opening width. Increases the etching rate. Then, the etching with respect to not only the depth (thickness) direction of the semiconductor substrate but also the lateral direction becomes stronger as the trench has a larger opening width.

  For this reason, in the trench bottom etching process performed with the oxide film exposed, lateral etching becomes stronger as the opening width becomes larger, and a part of the oxide film formed on the sidewall of the trench is removed to remove the oxide film. The thickness of the becomes thinner. Then, in the polymer film forming process performed after the trench bottom etching process, the polymer film is formed on the inner wall of the trench in a state where the thickness of the oxide film becomes thinner as the trench having a larger opening width. Also, in the trench etching process performed after this polymer film forming process, the lateral etching becomes stronger as the trench has a larger opening width. Therefore, the polymer film formed on the sidewall of the trench is removed when the etching is performed. It becomes easy. Then, when the polymer film formed on the sidewall of the trench is completely removed during the trench etching process, a part of the oxide film is removed again, and the thickness of the oxide film is reduced. It becomes thinner.

  Therefore, while the trench etching process and the polymer film forming process are repeatedly performed in order to make the trench depth the desired depth, the oxide film formed on the inner wall of the trench is more completely formed in the trench having a larger opening width. It becomes easy to be removed. Moreover, since the tendency becomes stronger as the side wall is closer to the bottom of the trench, the amount of lateral etching increases as the side is closer to the bottom of the trench. As a result, the closer to the bottom of the trench, the wider the trench, and the side wall angle becomes larger than 90 degrees. That is, the sidewall angle with respect to the semiconductor substrate surface varies for each trench.

  SUMMARY OF THE INVENTION In view of the above, the present invention provides a method for manufacturing a semiconductor device having a plurality of trenches having different opening widths, and suppresses variation in sidewall angle with respect to the surface of the semiconductor substrate in each trench as compared with a conventional method for manufacturing a semiconductor device. And

  In order to achieve the above object, according to the first aspect of the present invention, a trench etching step for reactive ion etching of the semiconductor substrate (1) using the mask (2), and reactive ion etching of the semiconductor substrate (1). A plurality of trenches (3) having different opening widths corresponding to the shape of the mask (2) by repeating the first polymer film forming step of forming the polymer film (4) on the inner wall of the portion which has been made a plurality of times. Forming a trench, forming a protective film (5) having a higher resistance to reactive ion etching than the polymer film (4) on the inner walls of the plurality of trenches (3), and forming inner walls of the plurality of trenches (3); A trench protective film forming step including: forming a polymer film (4) through the protective film (5) after forming the protective film (5); And Ji forming step is characterized by a deep trench (3) by repeating the trench protective film forming step, the alternately.

  According to a second aspect of the present invention, a trench etching step for reactive ion etching of the semiconductor substrate (1) using the mask (2) and an inner wall of the reactive ion etched portion of the semiconductor substrate (1) are provided. A first polymer film forming step for forming the polymer film (4), and a trench forming step for forming a plurality of trenches (3) having different opening widths corresponding to the shape of the mask (2) by repeating a plurality of times. Forming a protective film (5) having a higher resistance to reactive ion etching than the polymer film (4) on the inner walls of the plurality of trenches (3), and a protective film (5 on the inner walls of the plurality of trenches (3). ), A second polymer film forming step for forming a polymer film (4) through a protective film (5), a trench protective film forming step, and a protective film on the inner wall of the trench (3) ( And a trench bottom etching step for exposing the bottom of the trench (3) by performing a trench etching step in a state covered with the polymer film (4), and a trench forming step, a trench protective film forming step, The trench (3) is deepened by repeating the trench bottom etching step in order.

  In the method for manufacturing a semiconductor device according to claim 1, by performing the trench formation process in a state where the inner wall of the trench (3) is covered with the protective film (5) and the polymer film (4), the trench (3) The bottom is exposed. Further, in the method of manufacturing a semiconductor device according to claim 2, the trench (3) is formed by performing the trench bottom etching process in a state where the inner wall of the trench (3) is covered with the protective film (5) and the polymer film (4). ) Is exposed at the bottom.

  At this time, the lateral etching becomes stronger as the trench (3) having a larger opening width. However, since the protective film (5) and the polymer film (4) are arranged on the inner wall of the trench (3), the polymer film (4) is provided. Will be removed. That is, the bottom of the trench (3) is exposed while protecting the protective film (5) with the polymer film (4), so that only the oxide film is disposed as the protective film in the trench (3). It is possible to suppress a part of the protective film (5) from being removed by the conventional method of manufacturing a semiconductor device in which the bottom of the trench (3) is exposed by performing an etching process. Further, when the bottom of the trench (3) is exposed by the trench formation step as in the method of manufacturing a semiconductor device according to claim 1, the protective film (5) disposed on the bottom of the trench (3) In addition, since the polymer film (4) is formed on the side wall of the trench (3) even while the polymer film (4) is removed, the removal of a part of the protective film (5) is further suppressed. Can do.

  Therefore, in the trench forming step after exposing the bottom of the trench (3), the protective film (5) is formed on the inner wall of the trench (3) in a state where the protective film (5) is thicker than the conventional method of manufacturing a semiconductor device. ) To form the polymer film (4).

  In addition, the polymer film (4) is a deposited film, and as the trench (3) having a larger opening width, more deposited species enter the inside of the trench (3) to form a thicker film. For this reason, even if the trench (3) having a larger opening width has a stronger etching action in the lateral direction, it is protected by a thicker film, so that variations in the sidewall angle of the trench (3) due to the opening width can be suppressed.

  For example, as in the invention described in claim 3, the film thickness of the polymer film (4) formed in the second polymer film forming step is set to the polymer film (4) formed in the first polymer film forming step ( It can also be made thicker than the film thickness of 4).

  Further, in the step of forming the protective film (5) as in the invention described in claim 4 or 5, the protective film (5) is introduced by introducing oxygen gas or oxygen gas and inert gas into the chamber (21). ) Can form an oxide film. And like invention of Claim 6, Ar gas can also be used as an inert gas.

  Furthermore, as in the invention according to claim 7 or 8, in the step of forming the protective film (5), the protective film (5) is introduced by introducing nitrogen gas or nitrogen gas and hydrogen gas into the chamber (21). A nitride film can also be formed.

Further, as in the invention described in claim 9, in the trench etching process, a gas containing SF ₆ can be introduced into the chamber (21). As in the invention described in claim 10, in the first and second polymer film forming steps, a gas containing C ₄ F ₈ can be introduced into the chamber (21).

  Further, as in the invention described in claim 11, the trench etching step, the first polymer film forming step, the protective film forming step, and the second polymer film forming step are performed by plasma treatment, and plasma generation in each step Conditions and processing time can be set for each process.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing the manufacturing process of the semiconductor device according to the present embodiment, and will be described based on FIG.

  As shown in FIG. 1A, first, an oxide film is formed on the surface of the Si substrate 1 corresponding to the semiconductor substrate of the present invention, and a portion corresponding to the trench formation planned region is opened in the oxide film to oxidize. A film mask 2 is formed. Thereafter, the Si substrate 1 is placed in the chamber. FIG. 2 is a schematic view of a chamber provided with the Si substrate 1.

  As shown in FIG. 2, the chamber 21 constituting the vacuum chamber is provided with a gas introduction port 22 and a gas exhaust port 23. Gas lines 22a to 22d corresponding to the number of gas types to be introduced are connected to the gas introduction port 22 so that a plurality of types of gas can be introduced. The gas lines 22a to 22d are provided with switching valves 24a to 24d, respectively. It has been. And various gas can control the inflow into the chamber 21 by each switching valve 24a-24d. The gas exhaust port 23 is also provided with a switching valve 23a, and the gas in the chamber 21 is provided by the switching valves 24a to 24d provided in the gas lines 22a to 22d and the switching valve 23a provided in the gas exhaust port 23. The pressure can be set to a desired value. In the present embodiment, the gas inlet 22 is provided with four gas lines 22a to 22d for introducing each of etching gas, film deposition gas, oxygen gas, and Ar gas. In this embodiment, Ar gas corresponds to the inert gas of the present invention.

  The chamber 21 is provided with an electrode 26a to which a high frequency power supply 25a for bias is applied, an electrode 26b to which a high frequency power supply 25b for plasma generation is applied, and a ground electrode 27 disposed opposite to the electrode 26b. A high frequency electric field is applied to the Si substrate 1. The frequency of the plasma generating high frequency power supply 25b can be set to 13.56 MHz, for example, and the frequency of the bias high frequency power supply 25a can be set to 13.56 MHz or 500 kHz or less, for example.

  And each process mentioned later is performed by arrange | positioning Si substrate 1 on the electrode 26a in the chamber 21 comprised in such a structure. In each step, after the chamber vacuum level in the chamber 21 is sufficiently increased from the gas exhaust port 23 using a vacuum pump, the gas exhaust port 23 is switched while various gases are introduced from the gas inlet 22. By adjusting and exhausting the valve 23a, the gas pressure in the chamber 21 is set to 1 to 5 MPa. In each process, a plasma is generated by applying a high-frequency electric field to the plasma-generating high-frequency power supply 25b to generate a plasma by the introduced gas type, and the high-frequency electric field is applied to the biasing high-frequency power supply 25a to plasma process the Si substrate. . In the present embodiment, the plasma generation high-frequency power supply 25b is turned into a plasma by introducing about 100W to 10KW of power, and the bias high-frequency power supply 25a is supplied with about 0W to 500W of power. The Si substrate 1 is plasma processed.

As shown in FIG. 1B, the etching gas is introduced into the chamber 21 by opening the gas line 22a for introducing the etching gas and closing the other gas lines 22b to 22d, and the oxide film mask 2 is masked. A trench etching process for reactive ion etching of the Si substrate 1 is performed. In the present embodiment, it uses a SF ₆ gas as an etching gas, a SF ₆ gas was introduced 100~200sccm into the chamber 21, and the Si substrate 1 was treated 5-20 seconds by the SF ₆ plasma.

Thereafter, as shown in FIG. 1C, the film deposition gas is introduced into the chamber 21 by opening the gas deposition gas introduction gas line 22b and closing the other gas lines 22a, 22c, and 22d. Then, a first polymer film forming step is performed in which the polymer film 4 is formed on the inner wall of the portion of the Si substrate 1 that has been subjected to reactive ion etching by the step of FIG. In the present embodiment, uses a _C 4 _{F 8} gas as a gas for film _deposition, the C 4 _{F 8} gas was introduced 100~200sccm into the chamber 21, the Si substrate 1 by _C 4 _{F 8} plasma 5 By performing the treatment for 20 seconds, for example, the polymer film 4 having a film thickness of 10 nm is formed. In this embodiment, the polymer film 4 is formed by applying 0 W to the bias high-frequency power supply 25a, that is, by forming the polymer film 4 with the bias high-frequency power supply 25a turned off. At this time, the oxide film mask 2 is prevented from being etched.

Subsequently, as shown in FIG. 1D, the trench etching process shown in FIG. 1B and the first polymer film forming process shown in FIG. 1C are alternately repeated a plurality of times. Then, a trench forming step is performed in which a plurality of trenches 3 having different opening widths corresponding to the shape of the oxide film mask 2 are formed on the Si substrate 1. At this time, the time of the trench etching process and the time of the first polymer film forming process are performed in the same time as the process of FIGS. 1B and 1C. In other words, in the trench formation step, assuming that the trench etching step and the first polymer film forming step are one cycle, these steps are performed for a plurality of cycles, and the Si substrate 1 is subjected to 3 to 20 by SF ₆ plasma and C ₄ F ₈ plasma. Processing for a minute.

  Next, a trench protective film forming process including an oxide film forming process and a second polymer film forming process is performed, and the oxide film 5 and the polymer film 4 are disposed on the inner wall of the trench 3. Specifically, first, as shown in FIG. 1E, gas lines 22c and 22d for introducing oxygen gas and Ar gas are opened, and gas lines 22a and 22b for introducing etching gas and film deposition gas are introduced. Is closed, oxygen gas and Ar gas are introduced into the chamber 21 to remove the reaction products formed on the inner wall of the trench 3 and to form the oxide film 5 on the inner wall of the trench 3.

In this oxide film forming step, oxygen gas was introduced into the chamber 21 at 10 to 1000 sccm, and the Si substrate 1 was treated with O ₂ plasma and Ar plasma for 0.5 to 5 minutes to adhere to the inner wall of the trench 3. The reaction product is removed by the sputtering effect of oxygen ions or oxygen radicals and Ar ions to expose the Si portion on the inner wall surface. Then, the oxide film 5 is formed on the inner wall portion of the trench 3 by the action of oxygen ions (or oxygen radicals) by processing the Si substrate 1 in a plasma atmosphere. The reaction product refers to all the deposits attached to the inner wall surface by the interaction between the inner wall surface of the trench 3 and the plasma during etching. In the present embodiment, the oxide film 5 corresponds to the protective film of the present invention.

Thereafter, as shown in FIG. 1 (f), the film deposition gas is introduced into the chamber 21 by opening the gas deposition gas introduction gas line 22b and closing the other gas lines 22a, 22c and 22d. Then, a second polymer film forming step is performed in which the polymer film 4 is formed on the inner wall of the trench 3 via the oxide film 5. In the present embodiment, C ₄ F ₈ gas is introduced into the chamber 21 at 100 to 200 sccm, and the Si substrate 1 is treated with C ₄ F ₈ plasma for 10 to 100 seconds. Moreover, it is preferable that the film thickness of the polymer film 4 formed in the second polymer film forming process is larger than the film thickness of the polymer film 4 formed in the first polymer film forming process. For this reason, in the present embodiment, in the second polymer film forming step, the time for processing the Si substrate 1 with C ₄ F ₈ plasma is made longer than in the first polymer film forming step. A polymer film 4 having a thickness of 50 nm is formed through the oxide film 5.

  Subsequently, as shown in FIG. 1 (g), the trench formation process of FIG. 1 (d) is performed with the inner wall of the trench 3 covered with the oxide film 5 and the polymer film 4, and the trench is disposed at the bottom of the trench. The formed oxide film 5 and polymer film 4 are removed to expose the bottom of the trench 3 and deepen the trench 3.

  Specifically, the trench etching process of FIG. 1B is performed in the trench formation process, and the inner wall of the trench 3 is covered with the oxide film 5 and the polymer film 4 and is disposed at the bottom of the trench 3. The oxide film 5 and the polymer film 4 are subjected to reactive ion etching to remove part of the polymer film 4 and the oxide film 5 disposed at the bottom of the trench 3. At this time, the oxide film 5 and the polymer film 4 are arranged on the sidewall of the trench 3 or only the oxide film 5 is arranged.

  Then, the polymer film 4 is formed on the inner wall of the trench 3 via the oxide film 5 by performing the first polymer film forming process of FIG. The thickness of the polymer film 4 disposed therebetween is increased.

  That is, by performing a trench formation step that repeats the trench etching step and the first polymer film formation step a plurality of times, the oxide film disposed on the bottom of the trench 3 is removed little by little to expose the bottom of the trench 3. The trench 3 is deepened.

  Thereafter, the trench protective film forming step shown in FIGS. 1E and 1F and the trench forming step shown in FIG. 1D are repeated to make the trench 3 have a predetermined depth. Subsequently, a semiconductor device including the trench 3 is manufactured by performing a desired semiconductor manufacturing process on the Si substrate 1.

  In such a semiconductor device manufacturing method, the trench formation step is performed in a state where the inner wall of the trench 3 is covered with the oxide film 5 and the polymer film 4, thereby exposing the bottom of the trench 3 and deepening the trench. . When the bottom of the trench 3 is exposed by performing the trench formation process, the lateral etching becomes stronger as the trench 3 has a larger opening width. However, the oxide film 5 and the polymer film 4 are disposed on the inner wall of the trench 3. Therefore, it is removed from the polymer film 4. That is, since the bottom of the trench 3 is exposed by performing the trench formation process while protecting the oxide film 5 with the polymer film 4, the trench bottom etching process is performed with only the oxide film 5 disposed in the trench 3. The removal of part of the oxide film 5 can be suppressed by the conventional method for manufacturing a semiconductor device in which the bottom of the trench 3 is exposed. Further, in the present embodiment, the bottom of the trench 3 is exposed by a trench formation step in which the trench etching step and the first polymer film formation step are repeated a plurality of times, and the oxide film 5 and the polymer film disposed at the bottom of the trench 3 are exposed. Since the polymer film 4 is formed on the side wall of the trench 3 while removing the film 4, it is possible to further suppress the removal of a part of the oxide film 5.

  Therefore, in the trench formation step after exposing the bottom of the trench 3, the polymer film 4 is formed on the inner wall of the trench 3 via the oxide film 5 in a state where the thickness of the oxide film 5 is thicker than that of the conventional method of manufacturing a semiconductor device. A film can be formed. Further, in the trench forming step after exposing the bottom of the trench 3, the polymer film 4 formed on the side wall of the trench 3 is more easily removed as the opening 3 has a larger opening width, and the polymer film 4 is completely removed. In this case, a part of the oxide film 5 is removed and the film thickness is reduced.

  However, according to the manufacturing method of the semiconductor device of this embodiment, the polymer film 4 can be formed with the oxide film 5 being thicker than the conventional manufacturing method of the semiconductor device. Even if a part of the oxide film 5 is removed, the film thickness of the oxide film 5 after the trench etching process can be made thicker than before. Therefore, it is possible to prevent the oxide film 5 from being completely removed by the conventional method of manufacturing a semiconductor device while performing the trench formation step to make the depth of the trench 3 a desired depth. it can. Further, since the film thickness of the polymer film 4 becomes thicker as the trench 3 having a larger opening width, if the film thickness of the polymer film 4 deposited in the trench 3 is appropriately set, the sidewall angle with respect to the surface of the Si substrate 1 in each trench 3 is increased. Variations can be reduced.

  Furthermore, in this embodiment, the film thickness of the polymer film 4 formed in the second polymer film forming process is larger than the film thickness of the polymer film 4 formed in the first polymer film forming process. For this reason, when the trench formation process is performed to expose the bottom of the trench 3 and the trench 3 is deepened, the polymer film 4 formed in the second polymer film formation process is prevented from being completely removed. be able to. Therefore, in the trench formation process after exposing the bottom of the trench 3, if the polymer film 4 formed during the second polymer film formation process remains, the process shown in FIG. The film thickness of the polymer film 4 can also be increased when the polymer film 4 is formed under the same conditions as those of the first polymer film forming process. For this reason, when performing the trench formation process, it can suppress that the polymer film 4 is removed completely, and can suppress that a part of oxide film 5 is removed.

  Further, in order to suppress the variation in the side wall angle with respect to the surface of the Si substrate 1 in each trench 3, only the polymer film 4 is formed on the inner wall of the trench 3, and the polymer film 4 disposed on the side wall of the trench 3 is thickened. In this method, the film thickness of the polymer film 4 disposed on the bottom of the trench 3 is also set to the film thickness of the polymer film 4 disposed on the side wall of the trench 3. Depending on the thickness, it may become thick and cause etching abnormalities. However, according to the manufacturing method of the semiconductor device of this embodiment, the thicknesses of the oxide film 5 and the polymer film 4 arranged at the bottom of the trench 3 are compared with the method of arranging only the polymer film 4 on the inner wall of the trench 3. Therefore, the possibility of causing an etching abnormality can be reduced. Further, in the method of forming only the polymer film 4 on the inner wall of the trench 3, the possibility that the polymer film 4 adheres to the chamber 21 is greatly increased, and if the attached polymer film 4 is not completely removed, the etching abnormality is caused. Although the life of the chamber 21 is remarkably shortened, according to the method for manufacturing a semiconductor device of the present embodiment, the possibility that the polymer film 4 adheres in the chamber 21 is not significantly increased.

(Other embodiments)
In the first embodiment, oxygen gas and Ar gas are introduced to form the oxide film 5 as a protective film on the inner wall of the trench 3, but nitrogen gas and hydrogen gas are used instead of oxygen gas and Ar gas. It is also possible to form a nitride film as a protective film on the inner wall of the trench 3 by introduction. According to such a method of manufacturing a semiconductor device, since the O ₂ plasma decomposes the resist as compared with the case where the oxide film 5 is formed as a protective film on the inner wall of the trench 3 by O ₂ plasma, it is disposed on the Si substrate. An oxide film or a metal material formed by CVD or the like can only be used as a mask to be formed, but when a nitride film is formed on the inner wall of the trench 3 by N ₂ plasma and H ₂ plasma, a resist material can be used. Can be simplified. In such a semiconductor device manufacturing method, it is necessary to newly add a gas line for introducing nitrogen gas and hydrogen gas to the gas inlet 22.

  Further, the oxide film 5 can be formed by introducing only oxygen gas without introducing oxygen gas and Ar gas, or the nitrogen film can be formed by introducing only nitrogen gas without introducing nitrogen gas and hydrogen gas. It can also be formed.

  Furthermore, in the first embodiment, a method for manufacturing a semiconductor device in which the bottom of the trench 3 is exposed by performing a trench formation process in a state where the inner wall of the trench 3 is covered with the oxide film 5 and the polymer film 4 has been described. However, a method for manufacturing a semiconductor device in which the bottom of the trench 3 is exposed by performing a trench bottom etching process in a state where the inner wall of the trench 3 is covered with the oxide film 5 and the polymer film 4 may be used. Specifically, in the trench bottom etching process, after the process of FIG. 1F is performed, SF 6 gas is introduced into the chamber 21 in the same manner as the process of FIG. In the state where the oxide film 5 and the polymer film 4 are covered, the oxide film 5 and the polymer film 4 disposed at the bottom of the trench 3 are subjected to reactive ion etching to expose the bottom of the trench 3.

  Thus, when the bottom of the trench 3 is exposed by the trench bottom etching process, the trench forming process in FIG. 1D, the trench protective film forming process in FIGS. 1E and 1F, and the trench bottom etching are performed. You may comprise a semiconductor device by making the trench 3 the predetermined depth by repeating a process in order. In this trench bottom etching process, the oxide film 5 and the polymer film 4 arranged at the bottom of the trench 3 need to be removed. Therefore, the etching efficiency is increased by changing conditions such as the acceleration voltage. May be.

  In such a semiconductor device manufacturing method as well, the polymer film 4 is formed on the wall surface of the trench 3 via the oxide film 5 before the trench bottom etching step, as in the first embodiment. Thus, the oxide film 5 can be prevented from being completely removed by the conventional method of manufacturing a semiconductor device, and variation in the side wall angle with respect to the surface of the Si substrate 1 in each trench 3 can be suppressed.

  Further, the thickness of the polymer film 4 to be formed in the second polymer film forming step in the step of FIG. 1 (f) is formed in the first polymer film forming step in the step of FIG. 1 (c). The film is formed so as to be thicker than the thickness of the polymer film 4, but the thickness of the polymer film 4 formed in the second polymer film forming process is set in the first polymer film forming process. It can be the same as the thickness of 4, or it can be made thin.

  Furthermore, the plasma generation conditions, processing time, gas flow rate, and the like in the trench etching process, the first polymer film forming process, the protective film forming process, the second polymer film forming process, and the trench bottom etching process are set for each setting. It can also be changed as appropriate.

It is sectional drawing which shows the manufacturing process of the semiconductor device concerning 1st Embodiment of this invention. It is a schematic diagram of the chamber provided with the Si substrate shown in FIG. It is a figure which shows the experimental result when applying the conventional trench formation method and forming simultaneously the several trench from which opening width differs in a semiconductor substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Si substrate 2 Oxide film mask 3 Trench 4 Polymer film 5 Oxide film 21 Chamber 22 Gas inlet 23 Gas exhaust 25a High frequency voltage for bias 25b High frequency voltage for plasma generation

Claims (11)

A semiconductor substrate (1) provided with a mask (2) having an opening in a region where a trench is to be formed is introduced into a chamber (21), and the semiconductor substrate (1) is etched by reactive ion etching. In the manufacturing method of the semiconductor device in which the trench (3) is formed in 1),
A trench etching process for reactive ion etching of the semiconductor substrate (1) using the mask (2), and a polymer film (4) on the inner wall of the reactive ion etched portion of the semiconductor substrate (1). A first polymer film forming step of forming a film, and a trench forming step of forming a plurality of trenches (3) having different opening widths corresponding to the shape of the mask (2) by repeating a plurality of times.
Forming a protective film (5) having a higher resistance to the reactive ion etching than the polymer film (4) on the inner walls of the plurality of trenches (3), and forming the protective film on the inner walls of the plurality of trenches (3). A second protective film forming step of forming the polymer film (4) through the protective film (5) after forming the film (5), and a trench protective film forming step,
A method of manufacturing a semiconductor device, wherein the trench (3) is deepened by alternately repeating the trench forming step and the trench protective film forming step. A semiconductor substrate (1) provided with a mask (2) having an opening in a region where a trench is to be formed is introduced into a chamber (21), and the semiconductor substrate (1) is etched by reactive ion etching. In the manufacturing method of the semiconductor device in which the trench (3) is formed in 1),
A trench etching process for reactive ion etching of the semiconductor substrate (1) using the mask (2), and a polymer film (4) on the inner wall of the reactive ion etched portion of the semiconductor substrate (1). A first polymer film forming step of forming a film, and a trench forming step of forming a plurality of trenches (3) having different opening widths corresponding to the shape of the mask (2) by repeating a plurality of times.
Forming a protective film (5) having a higher resistance to the reactive ion etching than the polymer film (4) on the inner walls of the plurality of trenches (3), and forming the protective film on the inner walls of the plurality of trenches (3). After forming the film (5), a second polymer film forming step of forming the polymer film (4) through the protective film (5), a trench protective film forming step,
A trench bottom etching step for exposing the bottom of the trench (3) by performing the trench etching step in a state where the inner wall of the trench (3) is covered with the protective film (5) and the polymer film (4). Including,
A method of manufacturing a semiconductor device, comprising: deepening the trench (3) by sequentially repeating the trench forming step, the trench protective film forming step, and the trench bottom etching step.   The film thickness of the polymer film (4) formed in the second polymer film formation step is made larger than the film thickness of the polymer film (4) formed in the first polymer film formation step. The method for manufacturing a semiconductor device according to claim 1, wherein:   The oxide film is formed as the protective film (5) by introducing oxygen gas into the chamber (21) in the step of forming the protective film (5). A method for manufacturing a semiconductor device according to claim 1.   The step of forming the protective film (5) is characterized by forming an oxide film as the protective film (5) by introducing oxygen gas and inert gas into the chamber (21). 4. A method for manufacturing a semiconductor device according to any one of items 1 to 3.   6. The method of manufacturing a semiconductor device according to claim 5, wherein in the step of forming the protective film (5), Ar gas is used as the inert gas.   4. The step of forming the protective film (5) includes forming a nitride film as the protective film (5) by introducing nitrogen gas into the chamber (21). A method for manufacturing a semiconductor device according to claim 1.   The step of forming the protective film (5) includes introducing a nitrogen gas and a hydrogen gas into the chamber (21) to form a nitride film as the protective film (5). 4. A method for manufacturing a semiconductor device according to any one of 3 above. 9. The method of manufacturing a semiconductor device according to claim 1, wherein the trench etching step is performed by introducing a gas containing SF ₆ into the chamber (21). 10. The method according to claim 1, wherein the first and second polymer film forming steps are performed by introducing a gas containing C ₄ F ₈ into the chamber (21). A method for manufacturing a semiconductor device.   The trench etching process, the first polymer film forming process, the protective film forming process, and the second polymer film forming process are performed by plasma processing, and plasma generation conditions and processing time in each process are set for each process. The method of manufacturing a semiconductor device according to claim 1, wherein

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