JP4387984B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device in which an element isolation film is formed by a LOCOS method.

  In recent years, with the high integration and high functionality of semiconductor devices, element isolation formed by a LOCOS (Local Oxidation of Silicon) method in an internal region where fine functional elements such as memory cells are arranged with a high degree of integration. It is necessary to reduce the buzz beak of the film to narrow the space between elements. However, in a peripheral region where a peripheral element to which a high voltage is applied, such as a power supply element, is arranged, by maintaining the bird's beak of the element isolation film to a certain size, a transistor due to concentration of an electric field at the bottom of the step caused by the bird's beak It is necessary to prevent the deterioration of characteristics and the deterioration of gate oxide film quality.

  Therefore, in the manufacturing process of the semiconductor device, the element isolation film in the internal region and the element isolation film in the peripheral region, which are required to have different shapes as described above, are formed in separate processes. Here, when forming the element isolation film by the LOCOS method, the following steps are performed. That is, a step of forming a pad oxide film and an anti-oxidation film on a semiconductor substrate, a step of etching the anti-oxidation film and the pad oxide film using a resist pattern formed by lithography as a mask, and forming an oxidation window, and a heat This is a step of growing an oxide film to be an element isolation film on the surface of the semiconductor substrate by an oxidation method. For this reason, in the manufacturing process of the semiconductor device in which the functional circuit has been highly integrated as described above, for example, the step of removing the antioxidant film and the pad oxide film after forming the element isolation film in the peripheral region by the above procedure. After that, the above procedure is newly repeated to form an element isolation film in the inner region.

  However, in the method of forming a semiconductor device, as described above, the element isolation region in the inner region and the element isolation region in the peripheral region are formed in completely separate processes, so that the pad oxide film and the antioxidant film are formed. The film forming process and the thermal oxidation process must be performed twice, and there is a problem that the number of process steps for forming the element isolation region is large.

A method for manufacturing a semiconductor device of the present invention for solving the above-described problem is a method for manufacturing a semiconductor device in which an element isolation region is formed by a LOCOS method.

  In the method of manufacturing a semiconductor device according to claims 1 and 2, when forming the first element isolation film and the second element isolation film having different shapes, the respective oxidation windows are formed into the same pad oxide film and antioxidant film. After forming and forming a groove only on the surface of the semiconductor substrate on the bottom surface of one of the oxidation windows, thermal oxidation is performed on the bottom surfaces of both oxidation windows.

  In such a method, even if each oxidation window is formed on the same pad oxide film and antioxidant film by forming a groove only on the surface of the semiconductor substrate at the bottom of one oxidation window and performing thermal oxidation, An isolation film having a different bird's beak is formed on the oxidation window. For this reason, the film formation process of the pad oxide film and the antioxidant film when forming the first element isolation film and the second element isolation film having different shapes is reduced to one time.

  Furthermore, in the method of manufacturing a semiconductor device according to claims 3 to 5, when forming the first element isolation film and the second element isolation film having different shapes, first, a pad oxide film and an antioxidant film having different thicknesses are formed. It is formed on the same semiconductor substrate. Thereafter, a step of forming a first oxidation window and a second oxidation window provided in the pad oxide film and the antioxidant film, and a thermal oxidation step for forming the element isolation films on the bottom surfaces of the oxidation windows In the same process.

  In such a method, since the thickness of the pad oxide film and the thickness of the antioxidant film are different, even if the same thermal oxidation is performed on the bottom surface of each oxidation window formed in each film thickness portion, In the oxidation window, element isolation films having different bird's beak sizes are formed. For this reason, the process of forming each oxidation window and the process of thermal oxidation when forming the first element isolation film and the second element isolation film having different shapes are reduced to one time.

  As described above, according to the first or second aspect of the present invention, the groove is formed only on the surface of the semiconductor substrate on the bottom surface of one of the oxidation windows, so that the same pad oxide film and antioxidant film can be formed. Since the element isolation films having different shapes are formed on the bottom surfaces of the formed first oxidation window and the second oxidation window, formation of the pad oxide film and the antioxidant film when forming the element isolation films having different shapes is performed. The film process can be reduced to one time.

  According to the third to fifth aspects of the present invention, each oxidation window is provided in a portion where the film thicknesses of the pad oxide film and the antioxidant film are different. Since the element isolation films having different bird's beak sizes are formed, the oxidation window forming process and the thermal oxidation process for forming the first element isolation film and the second element isolation film having different shapes Can be reduced to one time.

  As described above, according to the first to fifth aspects of the present invention, the manufacturing process of the semiconductor device can be reduced.

  Embodiments to which the present invention is applied will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the component which is common in each embodiment, and the overlapping description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a cross-sectional process diagram for explaining a method for manufacturing a semiconductor device according to a first embodiment as a reference invention. The method according to the first embodiment will be described below with reference to FIG. First, in the first step, as shown in FIG. 1A, a semiconductor substrate 11 made of, for example, single crystal silicon is prepared. The semiconductor substrate 11 is provided with a first region 11a and a second region 12b on the surface side. Then, a pad oxide film 12 made of silicon oxide is formed on the semiconductor substrate 11, and an antioxidant film 13 made of silicon nitride is formed on the pad oxide film 12.

  Next, in the second step, as shown in FIG. 1B, a resist pattern 14 is formed on the antioxidant film 13 by lithography. The resist pattern 14 has an opening pattern corresponding to the element isolation film forming portion of the first region 11a. Next, using the resist pattern 14 as a mask, the antioxidant film 13 and the pad oxide film 12 are etched, whereby the antioxidant film 13 and the pad oxide film 12 in the first region 11 a reach the semiconductor substrate 11. A pattern of the oxidation window 15a is formed.

  Next, in the third step, as shown in FIG. 1 (3), after removing the resist pattern (14), the surface layer portion of the semiconductor substrate 11 exposed on the bottom surface of the first oxidation window 15a is removed by thermal oxidation. Selectively oxidize. Here, thermal oxidation is performed at 900 ° C. to 1100 ° C. using the antioxidant film 13 as a mask, and an oxide film 16 having a thickness of about 400 nm to 500 nm is grown on the surface layer of the semiconductor substrate 11.

  Thereafter, in the fourth step, a resist pattern 17 is newly formed on the antioxidant film 13 as shown in FIG. The resist pattern 17 has an opening pattern that fills the first oxidation window 15a and corresponds to the element isolation film forming portion of the second region 11b. Next, the anti-oxidation film 13 and the pad oxide film 12 are etched using the resist pattern 17 as a mask, whereby the anti-oxidation film 13 and the pad oxide film 12 in the second region 11 b reach the semiconductor substrate 11. The two oxidation window 15b is patterned.

  Next, in the fifth step, as shown in FIG. 1 (5), after removing the resist pattern (17), a second thermal oxidation treatment is performed at a temperature of 900 ° C. to 1100 ° C. As a result, the oxide film 16 on the bottom surface of the first oxidation window 15a is further grown to a thickness of about 450 nm to 600 nm, and the first element isolation film 16a made of the oxide film 16 further grown in the first region 11a is formed. . Along with this, an oxide film having a thickness of about 250 nm to 400 nm is newly grown on the bottom surface of the second oxidation window 15b, and a second element isolation film 16b made of the newly grown oxide film is formed in the second region 11b. .

  According to the above method, the oxidation process is performed twice on the bottom surface of the first oxidation window 15a, whereas only one oxidation process is performed on the bottom surface of the second oxidation window 15b. Is called. For this reason, the first element isolation film 16a formed in the first region 11a is thicker than the second element isolation film 16b formed in the second region 11b, whereby the second element isolation film 16b is larger than the second element isolation film 16b. Become a big bird's beak. Therefore, the first element isolation film 16a having a large bird's beak suitable for isolation of peripheral elements to which a high voltage is applied is formed in the first region 11a. On the other hand, in the second region 11b, the second element isolation film 16b having a small bird's beak that does not hinder the high integration of the miniaturized functional elements is formed. In addition, since the first element isolation film 16a disposed in the first region 11a is thicker than the second element isolation film 16b, a high voltage is applied to the first element isolation film 16a. Peripheral elements are surely separated.

  In the method of the first embodiment, the same pad oxide film 12 and antioxidant film 13 are used to form the first element isolation film 16a and the second element isolation film 16b. Therefore, as compared with the case where the first element isolation film 16a and the second element isolation film 16b having different shapes are formed by the conventional method, the removal process of the pad oxide film 12 and the antioxidant film 13 and the pad oxide film 12 and It is possible to reduce the number of steps of forming the antioxidant film 13.

(Second Embodiment)
FIG. 2 is a cross-sectional process diagram for explaining a semiconductor device manufacturing method according to a second embodiment to which another reference invention is applied. The second embodiment will be described below with reference to this drawing. Here, first, similarly to the first embodiment, the first process described with reference to FIG. 1A to the fourth process described with reference to FIG. A second oxidation window 15b is formed in 11b. Thereafter, as shown in FIG. 2A, the surface layer of the semiconductor substrate 11 on the bottom surface of the second oxidation window 15b is etched using the resist pattern 17 used for forming the second oxidation window 15b as a mask. As a result, a groove h having a depth of about 100 nm to 300 nm is formed on the surface of the semiconductor substrate 11.

  In the next fifth step, as shown in FIG. 2 (2), after removing the resist pattern (17), a second thermal oxidation process is performed at a temperature of 900 ° C. to 1100 ° C. This fifth step is performed in the same manner as described with reference to FIG. 1 (5) in the first embodiment.

  According to the above method, since the second element isolation film 16b is formed by oxidizing and growing the surface layer of the semiconductor substrate 11 in which the groove h is formed, the second element isolation film is compared with the first embodiment. The surface level difference of 16b becomes small, and thereby, the bird's beak of the second element isolation film 16b can be further reduced. In addition, since the formation of the groove h is performed continuously with the etching for forming the second oxidation window 15b, the manufacturing process does not increase specially as compared with the first embodiment.

(Third embodiment)
FIGS. 3A and 3B are cross-sectional process diagrams for explaining a semiconductor device manufacturing method according to a third embodiment to which the invention described in claim 1 is applied. The third embodiment will be described below with reference to FIGS. Here, first from the first step to the third step is the same as from the first step explained using FIG. 1 (1) to the third step explained using FIG. 1 (3) in the first embodiment. Then, an oxide film 16 is formed in the first region 11 a of the semiconductor substrate 11. However, the thickness of the oxide film 16 is about 100 nm to 300 nm.

  Thereafter, in the fourth step, as shown in FIG. 3A, the oxide film 16 on the bottom surface of the first oxidation window 15a is removed by etching using the antioxidant film 13 as a mask, and a groove h is formed on the surface of the semiconductor substrate 11. Form.

  In the next fifth step, a resist pattern 31 is newly formed on the antioxidant film 13 as shown in FIG. The resist pattern 31 has an opening pattern that fills the first oxidation window 15a and corresponds to the element isolation film forming portion of the second region 11b. Next, the anti-oxidation film 13 and the pad oxide film 12 are etched using the resist pattern 31 as a mask, whereby the anti-oxidation film 13 and the pad oxide film 12 in the second region 11 b reach the semiconductor substrate 11. The two oxidation window 15b is patterned.

  Thereafter, in the sixth step, as shown in FIG. 3 (3), after removing the resist pattern (31), a second thermal oxidation process is performed at a temperature of 900 ° C. to 1100 ° C. As a result, the bottom layers of the first oxidation window 15a and the second oxidation window 15b are oxidized to form the first element isolation film 16a made of an oxide film in the first region 11a and the oxide film in the second region 11b. A second element isolation film 16b is formed. These element isolation films 16a and 16b are grown to a thickness of about 400 nm to 600 nm.

  According to the above method, since the first element isolation film 16a is formed by oxidizing and growing the surface layer of the semiconductor substrate 11 in which the groove h is formed, the first element isolation film is more than the second element isolation film 16b. The step difference of the surface of 16a is reduced, whereby the first element isolation film 16a in which the bird's beak is suppressed smaller than the second element isolation film 16b is obtained. For this reason, the first element isolation film 16a having a small bird's beak is formed in the first region 11a without hindering the high integration of the miniaturized functional elements. On the other hand, the second element isolation film 16b having a large bird's beak suitable for isolation of peripheral elements to which a high voltage is applied is formed in the second region 11b.

  In the method of the third embodiment, as in the first embodiment, the same pad oxide film 12 and antioxidant film 13 are used to form the first element isolation film 16a and the second element isolation film 16b. Yes. Therefore, as compared with the case where the first element isolation film 16a and the second element isolation film 16b having different shapes are formed by the conventional method, the removal process of the pad oxide film 12 and the antioxidant film 13 and the pad oxide film 12 and the oxide film are oxidized. It is possible to reduce the number of steps of forming the prevention film 13.

  In addition, since the formation of the groove h is performed by etching and removing the oxide film 16 grown on the surface layer of the semiconductor substrate 11, the depth of the groove h is controlled as compared with the second embodiment. It can be performed with high accuracy by the film thickness. Furthermore, since the edge of the groove h becomes smooth, the edge of the first element isolation film 16a becomes smooth, and the stress generated in this portion can be kept small. In addition, since both the first element isolation film 16a and the second element isolation film 16b are formed by one thermal oxidation, the film thickness can be easily controlled.

(Fourth embodiment)
FIG. 4 is a cross-sectional process diagram for explaining a method of manufacturing a semiconductor device to which the invention according to claim 2 is applied. The fourth embodiment will be described below with reference to FIG. First, in the first step, as shown in FIG. 4A, a pad oxide film 12 and an antioxidant film 13 are formed on the semiconductor substrate 11. This step is performed in the same manner as the first step of the first embodiment.

  Next, in the second step, as shown in FIG. 4B, a resist pattern 41 is formed on the antioxidant film 13 by lithography. The resist pattern 41 has an opening pattern corresponding to the element isolation film forming portions of the first region 11a and the second region 11b. Next, the antioxidant film 13 and the pad oxide film 12 are etched using the resist pattern 41 as a mask, thereby the first oxidation reaching the semiconductor substrate 11 to the antioxidant film 13 and the pad oxide film 12 in the first region 11a. A window 15a is formed, and at the same time, a second oxidation window 15b reaching the semiconductor substrate 11 is formed in the antioxidant film 13 and the pad oxide film 12 in the second region 11b.

  Thereafter, in the third step, as shown in FIG. 4 (3), after removing the resist pattern (41), thermal oxidation is performed at 900 ° C. to 1100 ° C. An oxide film 16 having a thickness of 400 nm to 500 nm is grown on the bottom layer of the oxidation window 15b.

Next, in the fourth step, as shown in FIG. 4 (4), a resist pattern 42 covering the first region 11 a is formed on the semiconductor substrate 11. Then, using the resist pattern 42 and the antioxidant film 13 as a mask, only the oxide film 16 on the bottom surface of the second oxidation window 15b in the second region 11b is removed by etching. Thus, a groove h is formed on the surface of the semiconductor substrate 11 on the bottom surface of the second oxidation window 15b.

  Thereafter, in the fifth step, as shown in FIG. 4 (5), after removing the resist pattern (42), a second thermal oxidation treatment is performed at a temperature of 900 ° C. to 1100 ° C. As a result, the oxide film 16 on the bottom surface of the first oxidation window 15a is further grown to a thickness of about 450 nm to 600 nm, and the first element isolation film 16a made of the oxide film 16 further grown in the first region 11a is formed. . Along with this, an oxide film having a thickness of about 250 nm to 400 nm is newly grown on the bottom surface of the second oxidation window 15b, and a second element isolation film 16b made of the newly grown oxide film is formed in the second region 11b. .

  As described above, the first element isolation film 16a is formed in the first region 11a by two thermal oxidations, and the second region 11b is a film thinner than the first element isolation film 16a by one thermal oxidation. A thick second element isolation film 16b is formed. Moreover, since the second element isolation film 16b is formed by oxidizing and growing the surface layer of the semiconductor substrate 11 in which the groove h is formed, the second element isolation film 16b is formed in the first embodiment. The bird's beak is smaller than the second element isolation film 16b. For this reason, a first element isolation film 16a having a large bird's beak suitable for isolation of peripheral elements to which a high voltage is applied is formed in the first area 11a, and a highly functional element having a high density is formed in the second area 11b. The second element isolation film 16b having a small bird's beak that does not hinder integration is formed. In addition, since the first element isolation film 16a disposed in the first region 11a is thicker than the second element isolation film 16b, a high voltage is applied to the first element isolation film 16a. Peripheral elements are surely separated.

  In the method of the fourth embodiment, the same pad oxide film 12 and antioxidant film 13 are used to form the first element isolation film 16a and the second element isolation film 16b. In addition, the formation of the first oxidation window 15a and the formation of the second oxidation window 15b, which require high alignment accuracy, are performed in the same process. Therefore, as compared with the case where the first element isolation film 16a and the second element isolation film 16b having different shapes are formed by the conventional method, the removal process of the pad oxide film 12 and the antioxidant film 13 and the pad oxide film 12 and the oxide film are oxidized. It is possible to reduce the step of forming the prevention film 13 and the step of forming the oxidation window.

  Furthermore, since the formation of the groove h is performed by removing the oxide film 16 grown on the surface layer of the semiconductor substrate 11, the depth of the groove h can be controlled with high precision as in the third embodiment. The edge of the second element isolation film 16b becomes smooth and the stress generated in this portion can be kept small.

(Fifth embodiment)
FIGS. 5A and 5B are cross-sectional process diagrams for explaining a semiconductor device manufacturing method according to a fifth embodiment to which the invention described in claim 3 is applied. The fifth embodiment will be described below with reference to FIGS. First, in the first step, a pad oxide film 12 is formed on the semiconductor substrate 11 as shown in FIG. Thereafter, a resist pattern (not shown) is formed so as to cover the pad oxide film 12 in the first region 11a, and the pad oxide film 12 in the second region 11b is removed by etching using the resist pattern as a mask. Here, in order to prevent damage due to etching from being applied to the active region of the semiconductor substrate 11 in the second region 11b, wet etching using hydrogen fluoride water as an etching solution is performed.

  Next, after removing the resist pattern, as shown in FIG. 5B, the pad oxide film 12 in the first region 11a is further grown by performing a thermal oxidation process to form the first pad oxide film 12a. At the same time, an oxide film is newly grown on the surface layer of the semiconductor substrate 11 in the second region 11b to form a second pad oxide film 12b. Thus, the first pad oxide film 12a and the second pad oxide film 12b having a smaller thickness are formed without causing damage due to etching.

  If the pad oxide films 12a and 12b are damaged by etching, nitrogen is intruded from the antioxidant film into the semiconductor substrate through the damage in the subsequent element isolation film forming process. This nitride causes deterioration of the device. However, when it is not necessary to consider these problems, a silicon oxide film is formed on the semiconductor substrate 11, and only the silicon oxide film portion in the second region 11b is etched back to a predetermined depth. Pad oxide films having different film thicknesses may be formed in the first region 11a and the second region 11b.

  Thereafter, in the second step, as shown in FIG. 5C, an antioxidant film 13 is formed on the first pad oxide film 12a and the second pad oxide film 12b.

  Next, in the third step, as shown in FIG. 5 (4), a resist pattern 51 is formed on the antioxidant film 13 by lithography. The resist pattern 51 has an opening pattern corresponding to the element isolation film forming portions of the first region 11a and the second region 11b. Thereafter, the antioxidant film 13, the first pad oxide film 12a, and the second pad oxide film 12b are etched using the resist pattern 51 as a mask. Thus, a first oxidation window 15a reaching the semiconductor substrate 11 is formed in the antioxidant film 13 and the first pad oxide film 12a in the first region 11a, and at the same time, the antioxidant film 13 and the second film in the second region 11b. A second oxidation window 15b reaching the semiconductor substrate 11 is formed in the pad oxide film 12b.

  Thereafter, in the fourth step, as shown in FIG. 5 (5), after removing the resist pattern (51), a thermal oxidation process is performed at 900 ° C. to 1100 ° C., whereby the first oxidation window 15a and the second oxidation window 15a. An oxide film having a film thickness of 400 nm to 600 nm is grown on the bottom layer of the oxidation window 15b, the first element isolation film 16a made of the oxide film is formed in the first region 11a, and the oxide film made of the oxide film is formed in the second region 11b. A two-element isolation film 16b is formed.

  In the manufacturing method of the fifth embodiment, the first element isolation film 16a is formed in the first region 11a where the first pad oxide film 12a is formed, and the second pad is thinner than the first pad oxide film 12a. A second element isolation film 16b is formed in the second region 11b where the oxide film 12b is formed. For this reason, the first element isolation film 16a is larger in bird's beak than the second element isolation film 16b. Accordingly, the first element isolation film 16a having a large bird's beak suitable for isolation of peripheral elements to which a high voltage is applied is formed in the first area 11a, while the miniaturized functional element is formed in the second area 11b. The second element isolation film 16b having a small bird's beak that does not hinder high integration is formed.

  The first element isolation film 16a and the second element isolation film 16b are formed by the same thermal oxidation process. In addition, the formation of the first oxidation window 15a and the formation of the second oxidation window 15b, which require high alignment accuracy, are performed in the same process. Therefore, compared with the case where the first element isolation film 16a and the second element isolation film 16b having different shapes are formed by the conventional method, the thermal oxidation process for forming the element isolation film and the oxidation window are formed. It is possible to reduce the number of forming steps to one.

(Sixth embodiment)
FIG. 6 is a cross-sectional process diagram for explaining a method of manufacturing a semiconductor device according to a sixth embodiment to which the invention described in claim 4 is applied. The sixth embodiment will be described below with reference to this drawing. First, in the first step, a pad oxide film 12 is formed on the semiconductor substrate 11 as shown in FIG.

  Next, in the second step, as shown in FIG. 6B, a first silicon nitride film 61 is formed on the pad oxide film 12. Thereafter, a resist pattern (not shown) is formed so as to cover the first silicon nitride film 61 in the second region 11b, and the first silicon nitride film 61 in the first region 11a is removed by etching using the resist pattern as a mask. To do. Here, in order to prevent the semiconductor substrate 11 from being nitrided when an element isolation film is formed in the first region 11a due to etching damage applied to the pad oxide film 12 in the first region 11a, wet etching is performed. To do. At this time, by using hot phosphoric acid as an etching solution, the first silicon nitride film 61 is etched while maintaining a good selection ratio with respect to the pad oxide film 12, and the film thickness of the pad oxide film 12 is maintained.

  Thereafter, as shown in FIG. 6C, a second silicon nitride film 62 is formed on the pad oxide film 12 in the first region 11a and the first silicon nitride film 61 in the second region 11b. As a result, the first antioxidant film 13a made of the second silicon nitride film 62 is formed in the first region 11a. On the other hand, in the second region 11b, a second antioxidant film 13b composed of a first silicon nitride film 61 and a second silicon nitride film 62 is formed. As described above, the first antioxidant film 13a and the second antioxidant film 13b having a larger film thickness are formed without causing damage due to etching and with good controllability of the film thickness.

  Note that when the antioxidant films 13a and 13b are damaged by etching, the antioxidant film may not partially become an oxidation-resistant mask in the subsequent process of forming the element isolation film. However, when it is not necessary to consider such a problem, a silicon nitride film is formed on the pad oxide film 12, and only the silicon nitride film portion in the first region 11a is etched back to a predetermined depth. Thus, the first antioxidant film 13a and the second antioxidant film 13b made of this silicon nitride film may be formed.

  Next, in the third step, as shown in FIG. 6D, a resist pattern 63 is formed on the first antioxidant film 13a and the second antioxidant film 13b by lithography. The resist pattern 63 has an opening pattern corresponding to the element isolation film forming portions of the first region 11a and the second region 11b. Thereafter, the first antioxidant film 13a, the second antioxidant film 13b, and the pad oxide film 12 are etched using the resist pattern 63 as a mask. Thus, a first oxidation window 15a reaching the semiconductor substrate 11 is formed in the first antioxidant film 13a and the pad oxide film 12 in the first region 11a, and at the same time, the second antioxidant film 13b in the second region 11b and A second oxidation window 15 b reaching the semiconductor substrate 11 is formed in the pad oxide film 12.

  Thereafter, in the fourth step, as shown in FIG. 6 (5), after removing the resist pattern (63), a thermal oxidation process is performed at 900 ° C. to 1100 ° C. to thereby form the first oxidation window 15a and the second oxidation window 15a. An oxide film having a film thickness of 400 nm to 600 nm is grown on the bottom layer of the oxidation window 15b, the first element isolation film 16a made of the oxide film is formed in the first region 11a, and the oxide film made of the oxide film is formed in the second region 11b. A two-element isolation film 16b is formed.

  In the manufacturing method of the sixth embodiment, the first element isolation film 16a is formed in the first region 11a where the first antioxidant film 13a is formed, and the second oxidation film having a thickness larger than that of the first antioxidant film 13a. A second element isolation film 16b is formed in the second region 11b where the prevention film 13b is formed. For this reason, the first element isolation film 16a is larger in bird's beak than the second element isolation film 16b. Accordingly, the first element isolation film 16a having a large bird's beak suitable for isolation of peripheral elements to which a high voltage is applied is formed in the first area 11a, while the miniaturized functional element is formed in the second area 11b. The second element isolation film 16b having a small bird's beak that does not hinder high integration is formed.

  Here, as in the fifth embodiment, the first element isolation film 16a and the second element isolation film 16b are formed by the same thermal oxidation treatment, and the first oxidation window 15a and the second oxidation window are formed. The formation of 15b is performed in the same process. Therefore, compared with the case where the first element isolation film 16a and the second element isolation film 16b having different shapes are formed by the conventional method, the thermal oxidation process for forming the element isolation film and the oxidation window are formed. It is possible to reduce the number of forming steps to one.

(Seventh embodiment)
FIG. 7 is a cross-sectional process diagram for explaining a method of manufacturing a semiconductor device to which the invention of claim 5 is applied, and the seventh embodiment will be described below with reference to this figure. First, in the first step, as shown in FIG. 7A, a first silicon oxide film 71 is formed on the semiconductor substrate 11, and a first silicon nitride film 72 is formed on the first silicon oxide film 71. Form a film. Thereafter, a resist pattern (not shown) having a shape covering the first silicon nitride film 72 in the second region 11b is formed, and the first silicon nitride film 72 and the first oxidation in the first region 11a are formed using this resist pattern as a mask. The entire surface of the silicon film 71 is removed by etching. Here, the first silicon nitride film 72 is wet etched using hot phosphoric acid, and then the first silicon oxide film 71 is wet etched using hydrogen fluoride water. Thus, a second pad oxide film 12b made of the first silicon oxide film 71 is formed on the semiconductor substrate 11 in the second region 11b.

  Next, after removing the resist pattern, as shown in FIG. 7B, the surface of the semiconductor substrate 11 in the first region 11a is performed by performing thermal oxidation using the first silicon nitride film 72 as a mask. The layer is oxidized and grown to form a first pad oxide film 12a. The first pad oxide film 12a is formed to be thicker than the second pad oxide film 12b. As described above, the first pad oxide film 12a and the second pad oxide film 12b are formed in each individual process with good film thickness controllability.

  Thereafter, a second silicon nitride film 73 is formed on the first pad oxide film 12a in the first region 11a and on the first silicon nitride film 72 in the second region 11b. As a result, the first antioxidant film 13a made of the second silicon nitride film 73 is formed on the first pad oxide film 12a in the first region 11a. On the other hand, on the second pad oxide film 12b in the second region 11b, a second antioxidant film 13b composed of a first silicon nitride film 72 and a second silicon nitride film 73 is formed. The second antioxidant film 13b is thicker than the first antioxidant film 13a.

  Next, in the second step, as shown in FIG. 7C, a resist pattern 74 is formed on the first antioxidant film 13a and the second antioxidant film 13b by lithography. The resist pattern 74 has an opening pattern corresponding to the element isolation film forming portions of the first region 11a and the second region 11b. Thereafter, the first antioxidant film 13a, the second antioxidant film 13b, the first pad oxide film 12a, and the second pad oxide film 12b are etched using the resist pattern 74 as a mask. Thus, the first oxidation window 15a reaching the semiconductor substrate 11 is formed in the first antioxidant film 13a and the first pad oxide film 12a in the first region 11a, and at the same time, the second antioxidant film in the second region 11b. A second oxidation window 15b reaching the semiconductor substrate 11 is formed in 13b and the second pad oxide film 12b.

  Thereafter, in the third step, as shown in FIG. 7 (4), after removing the resist pattern (74), a thermal oxidation process is performed at 900 ° C. to 1100 ° C., whereby the first oxidation window 15a and the second oxidation window 15a. An oxide film having a film thickness of 400 nm to 600 nm is grown on the bottom layer of the oxidation window 15b, the first element isolation film 16a made of the oxide film is formed in the first region 11a, and the oxide film made of the oxide film is formed in the second region 11b. A two-element isolation film 16b is formed.

  In the manufacturing method of the seventh embodiment, the first element isolation film 16a is formed in the first region 11a where the first pad oxide film 12a and the first anti-oxidation film 13a are formed, and more than the first pad oxide film 12a. The second element isolation film 16b is formed in the second region 11b where the second antioxidant film 13b having a larger thickness than the second pad oxide film 12b and the first antioxidant film 13a having a smaller film thickness is formed. For this reason, the first element isolation film 16a is larger in bird's beak than the second element isolation film 16b. Accordingly, the first element isolation film 16a having a large bird's beak suitable for isolation of peripheral elements to which a high voltage is applied is formed in the first area 11a, while the miniaturized functional element is formed in the second area 11b. The second element isolation film 16b having a small bird's beak that does not hinder high integration is formed.

  As in the fifth and sixth embodiments, the first element isolation film 16a and the second element isolation film 16b are formed by the same thermal oxidation process, and the first oxidation window 15a is formed. The formation of the second oxidation window 15b is performed in the same process. Therefore, compared with the case where the first element isolation film 16a and the second element isolation film 16b having different shapes are formed by the conventional method, the thermal oxidation process for forming the element isolation film and the oxidation window are formed. It is possible to reduce the number of forming steps to one.

It is sectional process drawing explaining the manufacturing method of the semiconductor device of 1st Embodiment. It is sectional process drawing explaining the manufacturing method of the semiconductor device of 2nd Embodiment. It is sectional process drawing explaining the manufacturing method of the semiconductor device of 3rd Embodiment. It is sectional process drawing explaining the manufacturing method of the semiconductor device of 4th Embodiment. It is sectional process drawing explaining the manufacturing method of the semiconductor device of 5th Embodiment. It is sectional process drawing explaining the manufacturing method of the semiconductor device of 6th Embodiment. It is sectional process drawing explaining the manufacturing method of the semiconductor device of 7th Embodiment.

Explanation of symbols

11 Semiconductor substrate 11a First region 11b Second region 12 Pad oxide film 12a First pad oxide film 12b Second pad oxide film 13 Antioxidant film 13a First antioxidant film 13b Second antioxidant film 15a First oxidation window 15b First 2 Oxidation window 16 Oxide film 16a First element isolation film 16b Second element isolation film h Groove

Claims (2)

A first step of sequentially forming a pad oxide film and an antioxidant film on a first region and a second region of a semiconductor substrate in order from the lower layer;
A second step of patterning a first oxidation window reaching the semiconductor substrate on the pad oxide film and the antioxidant film in the first region;
A third step of growing an oxide film on the bottom layer of the first oxidation window by thermal oxidation;
Etching the oxide film on the bottom surface of the first oxidation window, and forming a groove on the surface of the semiconductor substrate on the bottom surface of the first oxidation window;
A fifth step of patterning a second oxidation window reaching the semiconductor substrate in the pad oxide film and the antioxidant film in the second region;
An oxide film is grown on the bottom layer of the first oxidation window and the second oxidation window by a thermal oxidation method, and a first element isolation film made of the oxide film is formed in the first area, and the second area A sixth step of forming a second element isolation film made of the oxide film,
A method of manufacturing a semiconductor device. A first step of sequentially forming a pad oxide film and an antioxidant film on a first region and a second region of a semiconductor substrate in order from the lower layer;
The antioxidant film and the pad oxide film in the first region are patterned to form a first oxidation window reaching the semiconductor substrate, and the antioxidant film and the pad oxide film in the second region are formed on the semiconductor substrate. A second step of patterning a second oxidation window reaching up to
A third step of growing an oxide film on a bottom layer of the first oxidation window and the second oxidation window by a thermal oxidation method;
A fourth step of etching only the oxide film on the bottom surface of the second oxide window to form a groove in the surface of the semiconductor substrate in the second region;
A first element isolation film is formed by growing the oxide film on the bottom surface of the first oxide window by a thermal oxidation method, and a second oxide film is formed on the bottom surface of the oxidation window in the second region. A fifth step of forming an element isolation film;
A method for manufacturing a semiconductor device, comprising:

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