JP2007115885A - Manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor device which can simplify processes by reducing a process of forming an alignment mark. <P>SOLUTION: The manufacturing method of a semiconductor device includes a process of forming a first trench 16a for an element isolation region 40 on a transistor forming region 10A of a semiconductor substrate 10, and forming a second trench 16b for an alignment mark 44 on an alignment mark forming region 10C of the semiconductor substrate; a process of forming a resist layer for covering one part of the transistor forming region by using the second trench as a first alignment mark; a process of introducing impurities into the semiconductor substrate to form a well 30 by using the resist layer as a mask; and a process of forming the element isolation region 40 on the transistor forming region by burying insulation layers into the first and second trenches, and forming the second alignment mark 44 on the alignment mark forming region. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device.

  A semiconductor device in which a low voltage drive transistor and a high voltage drive transistor are mixedly mounted on the same semiconductor substrate has the following problems. That is, the well in which the high voltage driving transistor is formed requires a step (drive-in step) for diffusing the implanted ions by a high-temperature heat treatment at about 1000 to 1200 ° C. When such heat treatment is performed after an element isolation region having an STI (Shallow Tnch Isolation) structure is formed, the trench insulating layer may expand due to thermal stress, which may cause crystal defects in the semiconductor substrate. Therefore, conventionally, before the heat treatment, it is usually necessary to form a dedicated alignment mark for patterning a mask used for ion implantation of the well.

  An object of the present invention is to provide a method of manufacturing a semiconductor device that can simplify the process by reducing the process of forming alignment marks.

A method for manufacturing a semiconductor device according to the present invention includes:
Forming a first trench for an element isolation region in a transistor formation region of a semiconductor substrate, and forming a second trench for an alignment mark in the alignment mark formation region of the semiconductor substrate;
Forming a resist layer covering a part of the transistor formation region using the second trench as a first alignment mark;
Forming a well by introducing impurities into the semiconductor substrate using the resist layer as a mask;
Forming an element isolation region in the transistor formation region by embedding an insulating layer in the first trench and the second trench, and forming a second alignment mark in the alignment mark formation region;
including.

  According to the present invention, the first trench is formed in the first and second transistor formation regions, the second trench is formed in the alignment mark formation region, and the second trench is used as the first alignment mark. The resist layer for forming can be patterned. Therefore, there is no need to form a dedicated alignment mark necessary for patterning the resist layer for introducing ions into the second well. Therefore, the number of processes can be reduced and the manufacturing process can be simplified.

  The present invention can further take the following aspects.

In the production method of the present invention,
The transistor formation region includes a first transistor formation region having a first well and a second transistor formation region having a second well deeper than the first well of the first transistor formation region. It can be a second well.

In the production method of the present invention,
The second well may be formed by implanting impurities into the semiconductor substrate and then diffusing the impurities by heat treatment.

In the production method of the present invention,
The alignment mark formation region may be in a scribe region.

In the production method of the present invention,
An offset gate MIS transistor may be formed in the second well.

In the production method of the present invention,
After forming the first trench and the second trench, the method may include a step of forming a block film that covers the surfaces of the first trench and the second trench.

1. First Embodiment A method of manufacturing a semiconductor device according to a first embodiment will be described with reference to FIGS. 1 to 11 are cross-sectional views schematically showing manufacturing steps of the semiconductor device of the first embodiment.

  In FIG. 1 to FIG. 11, as an example, a manufacturing method of one first transistor (low voltage driving transistor) is shown in the first transistor formation region 10A, and one second transistor (low voltage driving transistor) is shown in the second transistor formation region 10B. A high voltage driving transistor) is shown, and one alignment mark manufacturing method is shown in the alignment mark formation region 10C. The second transistor is driven with a higher driving voltage than the first transistor. Further, the alignment mark formation region 10C can be included in a scribe region where an element such as a transistor is not formed, for example. By providing the alignment mark formation region 10C in the scribe region, the wafer can be used effectively.

  Hereinafter, a method for manufacturing the semiconductor device of this embodiment will be described.

  (1) First, a description will be given with reference to FIG. A pad layer 12 is formed on the semiconductor substrate 10. As a material of the pad layer 12, for example, silicon oxide can be used. The pad layer 12 is formed by a thermal oxidation method or the like.

  Next, as shown in FIG. 1, a mask layer 14 is formed on the pad layer 12. As mask layer 14, for example, a single layer structure of any one of a silicon nitride layer, a polycrystalline silicon layer, and an amorphous silicon layer, or a silicon nitride layer, a polycrystalline silicon layer, and an amorphous silicon layer is used. A multilayer structure composed of at least two kinds selected can be used. As a method for forming the mask layer 14, a known method such as a CVD method can be used. The mask layer 14 has a film thickness sufficient to function as a stopper in a subsequent polishing process, for example, a CMP (Chemical Mechanical Polishing) process, for example, a film thickness of 50 to 200 nm.

  (2) As shown in FIG. 2, a resist layer 16 having a predetermined pattern is formed on the mask layer 14. The mask layer 14 is patterned by etching the mask layer 14 using the resist layer 16 as a mask. By this patterning, a first opening 15a for forming an element isolation region called STI (Shallow Trench Isolation) is formed in the mask layer 14 in the first transistor formation region 10A and the second transistor formation region 10B. In the mask layer 14 in the mark formation region 10C, a second opening 15b having a planar shape different from the planar shape of the first opening 15a is formed. Thereafter, the resist layer 16 is removed by a known method such as ashing or wet etching.

  (3) As shown in FIG. 3, the exposed portion of the pad layer 12 is removed by etching using the mask layer 14 as a mask. Next, the semiconductor substrate 10 is etched using the mask layer 14 as a mask. By this step, the first trench 16a for the element isolation region is formed in the first transistor formation region 10A and the second transistor formation region 10B, and the second trench 16b for the alignment mark is formed in the alignment mark formation region 10C. Form. The second trench 16b functions as an alignment mark (first alignment mark) in a subsequent well formation process or the like, and thus has a planar shape suitable for it. The planar shape of the second trench 16b is not particularly limited, and can be, for example, a box mark, a cross mark, a diffraction grating, or the like.

  (4) As shown in FIG. 4, a trench oxide film 18 made of silicon oxide is formed on the exposed surfaces of the first trench 16a and the second trench 16b by thermal oxidation called round oxidation. The trench oxide film 18 can prevent the semiconductor substrate 10 from being damaged or contaminated. The film thickness of the trench oxide film 18 is, for example, 10 to 50 nm.

  (5) As shown in FIG. 5, a resist layer 20 is formed so as to cover the first transistor formation region 10A and the alignment mark formation region 10C. The resist layer 20 is patterned by known lithography and etching using the second trench 16b as a first alignment mark.

  Next, ions are implanted into the semiconductor substrate 10 using the resist layer 20 as a mask. Thus, ions (p-type or n-type ions) 19 having a specific conductivity type are introduced into the second transistor formation region 10B not covered with the resist layer 20 to form a p-type or n-type impurity layer. .

  (6) As shown in FIG. 6, the resist layer 20 is removed. Next, for example, heat treatment is performed at 1000 to 1200 ° C., and ions in the impurity layer are diffused (drive-in), thereby forming the second well 30 in the semiconductor substrate 10. Thereafter, the resist layer 20 is removed by a method such as ashing.

  (7) As shown in FIG. 7, an insulating layer 40a is deposited on the entire surface so as to fill the first trench 16a and the second trench 16b. As a material of the insulating layer 40a, for example, silicon oxide can be used. The insulating layer 40a can have a film thickness that fills the trenches 16a and 16b and covers at least the stopper layer 14, for example, 360 to 1000 nm. Examples of the method for depositing the insulating layer 40a include high-density plasma CVD, thermal CVD, and TEOS plasma CVD.

  (8) As shown in FIG. 8, the insulating layer 40a is planarized by CMP. This planarization is performed until the stopper layer 14 is exposed. That is, the insulating layer 40a is planarized using the stopper layer 14 as a stopper.

  (9) As shown in FIG. 9, the mask layer 14 is removed. As a method for removing the mask layer 14, dry etching or wet etching can be used. When the mask layer 14 is made of silicon nitride, wet etching with hot phosphoric acid can be used. Next, if necessary, the protruding portion of the insulating layer 40a is removed by etching, and a trench insulating layer 42 having an upper surface substantially the same level as the upper surface of the semiconductor substrate 10 is formed.

  In this step, the element isolation region 40 is formed in the first and second transistor formation regions 10A and 10B by embedding the trench insulating layer 42 in the first trench 16a. In this step, simultaneously, the second alignment mark 44 can be formed by embedding the trench insulating layer 42 in the second trench 16b of the alignment mark formation region 10C. The second alignment mark 44 can be used as an alignment mark in a later photolithography process or the like, like a normal alignment mark.

  (10) As shown in FIG. 10, a resist layer 22 is formed so as to cover the second transistor formation region 10B and the alignment mark formation region 10C. The resist layer 22 is patterned by lithography and etching using the second alignment mark 44 as an alignment mark.

  Next, ions having a specific conductivity type (n-type or p-type ions) are formed in the first transistor formation region 10A not covered with the resist layer 22 by performing ion implantation into the semiconductor substrate 10 using the resist layer 22 as a mask. Then, a well (first well) 32 containing an n-type or p-type impurity is formed. In the formation process of the 1st well 32, it can have the diffusion process by heat processing as needed. The first well 32 is formed shallower than the second well 30.

  In the first transistor formation region 10A, the first transistor that is driven at a low voltage and has a lower drive voltage than the second transistor in the second transistor formation region 10B is formed, so that the well may be shallow. That is, since the second well 30 is formed with a second transistor having a drive voltage higher than that of the first transistor formed in the first well 32, the second well 30 has a sufficient depth to ensure well separation. Have

  (11) As shown in FIG. 11, the first transistor 50 is formed in the first transistor formation region 10A, and the second transistor 60 is formed in the second transistor formation region 10B. The first and second transistors 50 and 60 may have a typical MIS transistor structure. As described above, the second transistor 60 is a transistor having a higher breakdown voltage than the first transistor 50. The first transistor 50 includes a gate insulating layer 52, a gate electrode 54, a sidewall insulating layer 56, a source region 58, and a drain region 59. Similarly, the second transistor 60 includes a gate insulating layer 62, a gate electrode 64, a sidewall insulating layer 66, a source region 68, and a drain region 69. The gate insulating layer 62 of the second transistor 60 can be formed thicker than the gate insulating layer 52 of the first transistor 50 in order to increase the gate breakdown voltage.

  The first and second transistors 50 and 60 can be formed by a known method. Below, an example of the manufacturing method is described briefly.

  First, as shown in FIG. 11, the gate insulating layer 52 is formed in the first transistor formation region 10 </ b> A of the semiconductor substrate 10. Further, the gate insulating layer 62 is formed in the second transistor formation region 10B. Next, a conductive layer (not shown) is formed on the gate insulating layers 52 and 62. As the conductive layer, for example, a polycrystalline silicon layer can be formed. Next, gate electrodes 54 and 64 are formed by patterning the conductive layer. Next, impurities are ion-implanted into the first well 32 and the second well 30 in the same process or in another process to form a low concentration impurity layer. Next, sidewall insulating layers 56 and 66 are formed on both side surfaces of the gate electrodes 54 and 64. Next, impurities are ion-implanted into the first well 32 and the second well 30 to form source regions 58 and 68 and drain regions 59 and 69. The source region 58 and the drain region 59 and the source region 68 and the drain region 69 can also be formed by separate ion implantation.

  In the example shown in FIG. 11, the second transistor (high voltage drive transistor) 60 formed in the second transistor formation region 10B is a typical MIS transistor, but the second transistor is an offset gate MIS transistor shown in FIG. 70 may be sufficient.

  As shown in FIG. 12, the offset gate MIS transistor 70 is formed in the second well 30. The MIS transistor 70 includes an offset insulating layer 75 for electric field relaxation, a gate insulating layer 72 provided on the semiconductor layer 10, a part of the offset insulating layer 75 and a gate provided on the gate insulating layer 72. The electrode 74 includes a source region 78 and a drain region 79 provided at positions distant from the gate electrode 74. Under the offset insulating layer 75, offset impurity regions 76 and 77 having the same conductivity type as the source region 78 and the drain region 79 and a low impurity concentration are formed. In this example, the offset insulating layer 75 is formed in the same process as the trench insulating layer 42 in the element isolation region 40. In such an offset gate MIS transistor, since the gate electrode 74 and the source region 78 and the drain region 79 are separated from each other, the electric field on the drain region 79 side is particularly relaxed to improve the drain withstand voltage, and a high voltage driving transistor can be obtained. Can be configured.

  Next, features of the manufacturing method of this embodiment will be described.

  In the present embodiment, after forming the first trench 16a for the element isolation region 40 and the second trench 16b for the alignment mark 44, the second well 30 of the second transistor formation region 10B is formed. It has the following effects.

  That is, the first trench 16a is formed in the first and second transistor formation regions 10A and 10B, and the second trench 16b is formed in the alignment mark formation region 10C. Then, the resist layer 20 for forming the second well 30 can be patterned using the second trench 16b as the first alignment mark. Therefore, a process for forming a dedicated alignment mark for patterning the resist layer 20 is not required, and the manufacturing process can be simplified.

  In the second well 30 in which the high-voltage driving transistors 60 and 70 (see FIGS. 11 and 12) are formed, a step (drive-in step) of diffusing the implanted ions by high-temperature heat treatment at about 1000 to 1200 ° C. is required. And If such heat treatment is performed before the element isolation region having the STI structure is formed, the trench insulating layer may expand due to thermal stress, and crystal defects may occur in the semiconductor substrate. For this reason, conventionally, it has been necessary to form a dedicated alignment mark for patterning the well mask before the heat treatment. However, in this embodiment, since the second trench 16b formed simultaneously with the first trench 16a can be used as an alignment mark, a dedicated alignment mark forming process for the second well is not required.

  Further, during the high temperature processing for forming the second well 30, no trench insulating layer is embedded in the first trench 16 a for the element isolation region 40. Therefore, the above problem due to the heat treatment after the trench insulating layer (element isolation region) is formed does not occur.

  Furthermore, in the present embodiment, the second alignment mark 44 can be formed in the alignment mark formation region 10C simultaneously with the element isolation region 40 of the transistor formation regions 10A and 10B. The second alignment mark 44 can be used as a normal alignment mark in the subsequent lithography process.

  The present invention is useful for a so-called mixed type semiconductor device having a first transistor formation region 10A in which a low voltage drive transistor is formed and a second transistor formation region 10B in which a high voltage drive transistor is formed. However, the present invention can be applied to a semiconductor device having any transistor formation region.

2. Second Embodiment This embodiment is different from the first embodiment in that a block film is further formed on the surface of the trench. 13 to 18 are cross-sectional views schematically showing the manufacturing method of this embodiment.

  Since the process until the trench is formed is the same as the processes (1) to (5) (see FIGS. 1 to 5) of the first embodiment, the detailed description is omitted. In addition, the same code | symbol is attached | subjected and demonstrated to the part substantially the same as the part shown in FIGS. Hereinafter, a process after the trench oxide film 18 is formed on the exposed surfaces of the first trench 16a and the second trench 16b will be described.

  (1) As shown in FIG. 13, a block film 80 is formed on the surfaces of the trench oxide film 18 and the mask layer 14. As the block film 80, for example, silicon nitride can be used. The block film 80 is formed before the heat treatment in the drive-in process. The block film 80 can be formed by, for example, a CVD method.

  By forming the block film 80, the reaction between the silicon of the semiconductor substrate 10 and oxygen or nitrogen in the atmosphere can be reliably prevented. As a result, the trench insulating layer 42 embedded in the trenches 16a and 16b can be prevented from expanding due to the heat treatment, and further, the pileup phenomenon of impurities in the first well 32 and the second well 30 can be suppressed. A desired impurity profile can be obtained.

  (2) As shown in FIG. 14, a resist layer 20 is formed so as to cover the first transistor formation region 10A and the alignment mark formation region 10C. The resist layer 20 is patterned by known lithography and etching using the second trench 16b as a first alignment mark.

  Next, ions are implanted into the semiconductor substrate 10 using the resist layer 20 as a mask. Thus, ions (p-type or n-type ions) 19 having a specific conductivity type are introduced into the second transistor formation region 10B not covered with the resist layer 20 to form a p-type or n-type impurity layer. .

  (3) As shown in FIG. 15, the resist layer 20 is removed. Next, for example, heat treatment is performed at 1000 to 1200 ° C., and ions in the impurity layer are diffused (drive-in), thereby forming the second well 30 in the semiconductor substrate 10. Thereafter, the resist layer 20 is removed by a method such as ashing.

  (4) As shown in FIG. 16, an insulating layer 40a is deposited on the entire surface so as to fill the first trench 16a and the second trench 16b. As a material of the insulating layer 40a, for example, silicon oxide can be used. Since the insulating layer 40a is the same as that of the first embodiment, a detailed description thereof is omitted.

  (5) As shown in FIG. 17, the insulating layer 40a is planarized by CMP. This planarization is performed until the stopper layer 14 is exposed.

  (6) As shown in FIG. 18, the mask layer 14 is removed. Since the method for removing the mask layer 14 is the same as that in the first embodiment, a detailed description thereof is omitted. Next, if necessary, the protruding portion of the insulating layer 40a is removed by etching, and a trench insulating layer 42 having an upper surface substantially the same level as the upper surface of the semiconductor substrate 10 is formed.

  In this step, the element isolation region 40 is formed in the first and second transistor formation regions 10A and 10B by embedding the trench insulating layer 42 in the first trench 16a. In this step, simultaneously, the second alignment mark 44 can be formed by embedding the trench insulating layer 42 in the second trench 16b of the alignment mark formation region 10C. The second alignment mark 44 can be used as an alignment mark in a later photolithography process or the like, like a normal alignment mark.

  Thereafter, in the same manner as in the step (10) of the first embodiment (see FIG. 10), ions having a specific conductivity type (n-type or p-type ions) are introduced into the first transistor formation region 10A and n. A well (first well) 32 containing a p-type or p-type impurity is formed. Next, in the same manner as in step (11) of the first embodiment (see FIG. 11), the first transistor 50 is formed in the first transistor formation region 10A, and the second transistor 60 is formed in the second transistor formation region 10B. . Since the first and second transistors 50 and 60 have been described in the first embodiment, a detailed description thereof will be omitted. As the second transistor, the offset gate MIS transistor 70 shown in FIG. 12 can be used.

  The second embodiment also has the same features as the first embodiment. Furthermore, as described above, by having the block film 80, it is possible to prevent the element isolation region 40 from expanding and to optimize the impurity profile of the well.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

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Explanation of symbols

10 semiconductor substrate, 10A first transistor formation region, 10B second transistor formation region, 10C alignment mark formation region, 12 pad layer, 14 mask layer,
16a first trench, 16b second trench, 18 trench oxide film, 30 second well, 32 second well, 40 element isolation region, 42 trench insulating layer, 50 first transistor, 60, 70 second transistor, 80 block film

Claims (6)

Forming a first trench for an element isolation region in a transistor formation region of a semiconductor substrate, and forming a second trench for an alignment mark in the alignment mark formation region of the semiconductor substrate;
Forming a resist layer covering a part of the transistor formation region using the second trench as a first alignment mark;
Forming a well by introducing impurities into the semiconductor substrate using the resist layer as a mask;
Forming an element isolation region in the transistor formation region by embedding an insulating layer in the first trench and the second trench, and forming a second alignment mark in the alignment mark formation region;
A method for manufacturing a semiconductor device, comprising: In claim 1,
The transistor formation region includes a first transistor formation region having a first well and a second transistor formation region having a second well deeper than the first well of the first transistor formation region. A manufacturing method of a semiconductor device which is the second well. In claim 2,
The method of manufacturing a semiconductor device, wherein the second well is formed by ion-implanting impurities into the semiconductor substrate and then diffusing the impurities by heat treatment. In any of claims 1 to 3,
The method for manufacturing a semiconductor device, wherein the alignment mark formation region is in a scribe region. In any of claims 2 to 4,
A method of manufacturing a semiconductor device, wherein an offset gate MIS transistor is formed in the second well. In any of claims 1 to 5,
A method of manufacturing a semiconductor device, comprising: forming a block film that covers surfaces of the first trench and the second trench after forming the first trench and the second trench.

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