CN115775765A - Method for forming trench isolation structure - Google Patents
Method for forming trench isolation structure Download PDFInfo
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- CN115775765A CN115775765A CN202211440394.3A CN202211440394A CN115775765A CN 115775765 A CN115775765 A CN 115775765A CN 202211440394 A CN202211440394 A CN 202211440394A CN 115775765 A CN115775765 A CN 115775765A
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- trench isolation
- isolation structure
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- silicon dioxide
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Abstract
The invention provides a method for forming a trench isolation structure, which comprises the following steps: providing a substrate, the substrate comprising silicon; etching the substrate to form a plurality of spaced trenches in a region where a trench isolation structure is to be formed, wherein the trenches are separated by silicon columns, the silicon columns are made of silicon, and the ratio of the width of each silicon column to the width of each trench is greater than or equal to 0.45; and performing thermal oxidation treatment on the silicon column to form the silicon dioxide column, wherein the silicon dioxide expands when the silicon dioxide column is subjected to thermal oxidation so that the groove is filled with the silicon dioxide. In the wider trench isolation structure, the surface of the trench isolation structure is kept flat, and the surface of the trench isolation structure is flush with the surface of the substrate.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a method for forming a trench isolation structure.
Background
In an integrated circuit process, a plurality of functional devices or functional elements need to be simultaneously manufactured on the same semiconductor silicon wafer, and therefore, the functional devices or the functional elements need to be isolated by using a trench isolation structure. Shallow trench isolation structures are commonly used trench isolation structures, and the width of the shallow trench isolation structure (the width between adjacent functional devices or adjacent functional elements) is generally greater than 20um. Shallow trench isolation structures are typically formed by filling trenches with silicon dioxide.
In the prior art, a method for forming a trench isolation structure includes: referring to fig. 1, first, a substrate 110 is provided, the substrate 110 may be a wafer, a silicon oxide layer 120 is formed on the surface of the substrate 110, the silicon oxide layer 120 may be formed by depositing a layer of silicon dioxide, a silicon nitride layer 130 is formed on the surface of the silicon oxide layer 120, and the silicon nitride layer 130 may be formed by depositing silicon oxide. Next, referring to fig. 2, the silicon nitride layer 130, the silicon oxide layer 120 and a portion of the substrate 110 are etched from the surface of the silicon nitride layer 130 toward the inner side of the substrate 110, and the etching stop portion is the inner side of the substrate 110, and a trench is formed by etching. The trench is filled with silicon dioxide 140, and the silicon dioxide 140 may be grown by high density plasma or thermal oxidation. At this time, silicon dioxide covers the surface of the silicon nitride layer 130. Next, referring to fig. 3, the silicon dioxide 140 on the surface of the silicon nitride layer 130 is removed, and the silicon dioxide 140 on the surface of the silicon nitride layer 130 may be removed by grinding, or the silicon dioxide 140 on the surface of the silicon nitride layer 130 may be removed by etching, so that the surface of the silicon nitride layer 130 is exposed after the silicon dioxide 140 is removed. The remaining silicon dioxide within the trench serves as a trench isolation structure 150. And finally, removing the silicon nitride layer 130 and the silicon oxide layer 120, wherein the silicon nitride layer 130 and the silicon oxide layer 120 can be removed by an etching method, and the surface of the substrate 110 is exposed after the removal.
However, since the width of the trench isolation structure is wide, i.e. the width within the substrate 110 is wide, and is generally greater than 20 μm, the trench is also formed with a width greater than 20 μm. Due to the wide width, the surface of the trench isolation structure 150 may be uneven by using the prior art trench isolation structure forming method, and particularly, the surface of the trench isolation structure 150 may not be flush with the surface of the substrate 110 due to the recess in the middle portion of the trench isolation structure 150.
Disclosure of Invention
The invention aims to provide a method for forming a trench isolation structure, wherein in a wider trench isolation structure, the surface of the trench isolation structure can be kept flat, and the surface of the trench isolation structure can be flush with the surface of a substrate.
In order to achieve the above object, the present invention provides a method for forming a trench isolation structure, comprising:
providing a substrate, the substrate comprising silicon;
etching the substrate in a region where a trench isolation structure is to be formed to form a plurality of spaced trenches, wherein the trenches are separated by silicon columns, the silicon columns are made of silicon, and the ratio of the width of each silicon column to the width of each trench is greater than or equal to 0.45;
and carrying out thermal oxidation treatment on the silicon column to form the silicon dioxide column, wherein during thermal oxidation of the silicon dioxide column, the silicon dioxide expands to fill the groove with the silicon dioxide.
Optionally, in the method for forming the trench isolation structure, the substrate is dry etched to form a plurality of spaced trenches.
Optionally, in the method for forming the trench isolation structure, the silicon pillar is a cuboid.
Optionally, in the method for forming a trench isolation structure, there are a plurality of silicon pillars.
Optionally, in the method for forming the trench isolation structure, the widths of the plurality of silicon pillars are the same.
Optionally, in the method for forming the trench isolation structure, the plurality of trenches have the same width.
Optionally, in the method for forming the trench isolation structure, the method for performing thermal oxidation treatment on the silicon pillar includes: dry oxygen oxidation or steam oxidation.
Optionally, in the method for forming a trench isolation structure, the substrate includes: single crystal silicon, silicon-on-insulator (SOI), or stacked silicon-on-insulator (SSOI).
Optionally, in the method for forming a trench isolation structure, after performing thermal oxidation treatment on the plurality of silicon pillars to form silicon dioxide pillars, and expanding the silicon dioxide pillars to fill the trenches with silicon dioxide, the method further includes: and grinding the silicon dioxide to enable the surface of the silicon dioxide to be flush with the surface of the substrate.
The method for forming the trench isolation structure provided by the invention comprises the following steps: providing a substrate comprising silicon; etching the substrate in a region where a trench isolation structure is to be formed to form a plurality of spaced trenches, wherein the trenches are separated by silicon columns, the silicon columns are made of silicon, and the ratio of the width of each silicon column to the width of each trench is greater than or equal to 0.45; and carrying out thermal oxidation treatment on the silicon column to form the silicon dioxide column, wherein during thermal oxidation of the silicon dioxide column, the silicon dioxide expands to fill the groove with the silicon dioxide. In the wider trench isolation structure, the surface of the trench isolation structure is kept flat, and the surface of the trench isolation structure is flush with the surface of the substrate.
Drawings
Fig. 1 to 3 are schematic views illustrating a method of forming a trench isolation structure according to the prior art;
FIG. 4 is a flow chart of a method of forming a trench isolation structure according to an embodiment of the present invention;
fig. 5 to 8 are schematic views illustrating a method of forming a trench isolation structure according to an embodiment of the present invention;
in the figure: 110-substrate, 120-silicon oxide layer, 130-silicon nitride layer, 140-silicon dioxide, 150-trench isolation structure, 210-substrate, 220-silicon oxide layer, 230-trench, 240-silicon column, 250-silicon dioxide, 260-trench isolation structure.
Detailed Description
The following describes in more detail embodiments of the present invention with reference to the schematic drawings. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
In the following, the terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances. Similarly, if the method described herein comprises a series of steps, the order in which these steps are presented herein is not necessarily the only order in which these steps may be performed, and some of the described steps may be omitted and/or some other steps not described herein may be added to the method.
Referring to fig. 4, the present invention provides a method for forming a trench isolation structure, including:
s11: providing a substrate, the substrate comprising silicon;
s12: etching the substrate to form a plurality of spaced trenches in a region where a trench isolation structure is to be formed, wherein the trenches are separated by silicon columns, the silicon columns are made of silicon, and the ratio of the width of each silicon column to the width of each trench is greater than or equal to 0.45;
s13: and performing thermal oxidation treatment on the silicon column to form the silicon dioxide column, wherein the silicon dioxide expands when the silicon dioxide column is subjected to thermal oxidation so that the groove is filled with the silicon dioxide.
First, referring to fig. 5, a substrate 210 is provided, the substrate 210 including silicon. Thus, the substrate 210 may be single crystal silicon, silicon-on-insulator (SOI), or stacked silicon-on-insulator (SSOI). In other embodiments of the present invention, a silicon-on-insulator (SOI) or a silicon-on-insulator-stack (SSOI) wafer may also be selected. Next, a silicon oxide layer 220 is formed on the surface of the substrate 210, and the silicon oxide layer 220 may be formed by depositing silicon dioxide, and in other embodiments of the present invention, the silicon oxide layer may be formed in other manners, which are not described herein.
Referring to fig. 5, in the region where the trench isolation structure is to be formed, the substrate 210 is etched to form a plurality of spaced trenches 230, the substrate may be dry etched to form a plurality of spaced trenches 230, the plurality of trenches 230 have the same width, and the plurality of trenches 230 have the same depth. Since the substrate 210 comprises silicon and the embodiment of the present invention uses single crystal silicon, the spacing between the trenches 230 is necessarily the substrate 210, that is, silicon, and since the longitudinal section of the trench 230 is rectangular and the inner wall of the trench 230 is straight, the substrate 210 between the trenches 230 can form a columnar structure, that is, the silicon pillars 240 are rectangular and referred to as silicon pillars 240. Since the number of the trenches 230 is plural, the silicon pillars 240 are also plural, and the widths of the plural silicon pillars 240 are the same. The trenches 230 are separated by silicon pillars 240, and the silicon pillars 240 are silicon. The ratio of the width of the silicon pillar 240 to the width of the trench 230 is greater than or equal to 0.45, 0.55, for example, if the width of the silicon pillar 240 is 0.45 μm, the width of the trench 230 is 0.55 μm, and the width of the silicon pillar 240 and the width of the trench 230 and the width of the trench isolation structure both refer to the width in a direction parallel to the surface of the substrate 210 and between the devices (the devices being separated by the trench isolation structures). The silicon oxide layer 220 on the surface of the substrate 210 is necessarily etched when the substrate 210 is etched to form the trench 230, and therefore, the etched silicon oxide layer 220 is also the patterned silicon oxide layer 220, and the patterned silicon oxide layers 220 are respectively located on the surfaces of the silicon pillars 240. The etching of the silicon oxide layer 220 in the embodiment of the present invention is not a key point, and is not described herein.
Next, referring to fig. 6, the patterned silicon oxide layer 220 is removed, that is, the patterned silicon oxide layer 220 on the surface of the substrate 210 and the silicon pillars 240 are removed. The etching method may be adopted for removing, specifically, dry etching or wet etching is adopted, and may be determined according to actual conditions, and details are not repeated in the embodiments of the present invention.
Referring to fig. 6 and 7, the silicon pillar 240 is thermally oxidized to form a silicon dioxide pillar, and the silicon pillar 240 expands when thermally oxidized to form silicon dioxide, i.e., the silicon pillar 240 becomes silicon dioxide and then becomes larger in volume. The silicon pillar 240 expands into the trench in the left and right directions during thermal oxidation, so that if the ratio of the width of the silicon pillar 240 to the width of the trench is designed, the trench can be filled with silicon dioxide. Theoretically, 1nm of SiO2 needs to consume 0.45nm of Si, and the ratio of the width of the silicon pillar 240 to the width of the trench 230 is greater than or equal to 0.45, so the embodiment of the present invention can make the silicon dioxide fill the trench 230. The method for performing thermal oxidation treatment on the silicon pillar 240 comprises the following steps: dry oxygen oxidation or water vapor oxidation, the specific oxidation time may be specifically determined according to the height of the silicon column 240, and the oxidation temperature may be a common oxidation temperature, which is not described herein.
After the silicon pillar 240 is oxidized, the trench is filled with silicon dioxide 250, and at this time, the silicon dioxide also partially spreads to the surface of the substrate 210, and the surface of the silicon dioxide 250 is not flat. Therefore, referring to fig. 8, the silicon dioxide 250 is polished so that the surface of the silicon dioxide 250 is flush with the surface of the substrate 210. In other embodiments of the present invention, the silicon dioxide 250 may be etched, so that the surface of the silicon dioxide 250 is flush with the surface of the substrate 210. Finally, in the embodiment of the present invention, the trench isolation structure with a width greater than 20 μm may be formed by using the embodiment of the present invention, but in other embodiments of the present invention, the trench isolation structure with a width less than or equal to 20 μm may also be applied. Compared with the method for forming the trench isolation structure by filling the trench with the method for depositing the silicon dioxide by using the plasma in the prior art, the embodiment of the invention does not have the situation that the surface of the trench isolation structure formed in the prior art is uneven and uneven with the surface of the substrate. In addition, the trench isolation structure 260 formed by the embodiment of the present invention is compact and does not crack. Finally, the trench isolation structures 260 formed using embodiments of the present invention may be used to isolate devices. The devices of the embodiments of the present invention may be CMOS devices or the like, and the devices may be formed directly anywhere on the substrate 210 outside the trench isolation structures 260, such as within the substrate 210 or on the surface of the substrate 210. It is feasible to have trench isolation structures 260 between the devices. The embodiment of the present invention is exemplified by forming one trench isolation structure 260, i.e., forming one trench isolation structure 260 needs to be formed through a plurality of trenches 230 and a plurality of silicon pillars 240. In practice, a plurality of trench isolation structures 260 need to be formed, and the forming method of each trench isolation structure 260 is the same as that of the trench isolation structure 260 described above.
In summary, the method for forming a trench isolation structure according to an embodiment of the present invention includes: providing a substrate, the substrate comprising silicon; etching the substrate to form a plurality of spaced trenches in a region where a trench isolation structure is to be formed, wherein the trenches are separated by silicon columns, the silicon columns are made of silicon, and the ratio of the width of each silicon column to the width of each trench is greater than or equal to 0.45; and performing thermal oxidation treatment on the silicon column to form the silicon dioxide column, wherein the silicon dioxide expands when the silicon dioxide column is subjected to thermal oxidation so that the groove is filled with the silicon dioxide. In the wider trench isolation structure, the surface of the trench isolation structure is kept flat, and the surface of the trench isolation structure is flush with the surface of the substrate.
The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any way. Any person skilled in the art can make any equivalent substitutions or modifications on the technical solutions and technical contents disclosed in the present invention without departing from the scope of the technical solutions of the present invention, and still fall within the protection scope of the present invention without departing from the technical solutions of the present invention.
Claims (9)
1. A method for forming a trench isolation structure, comprising:
providing a substrate comprising silicon;
etching the substrate in a region where a trench isolation structure is to be formed to form a plurality of spaced trenches, wherein the trenches are separated by silicon pillars, the silicon pillars are made of silicon, and the ratio of the width of each silicon pillar to the width of each trench is greater than or equal to 0.45;
and carrying out thermal oxidation treatment on the silicon column to form the silicon dioxide column, wherein during thermal oxidation of the silicon dioxide column, the silicon dioxide expands to fill the groove with the silicon dioxide.
2. The method of forming a trench isolation structure of claim 1 wherein dry etching said substrate forms a plurality of spaced trenches.
3. The method of forming a trench isolation structure as claimed in claim 1, wherein the silicon pillar has a rectangular parallelepiped shape.
4. The method of forming a trench isolation structure as claimed in claim 3, wherein the silicon pillar is plural.
5. The method of forming a trench isolation structure as claimed in claim 4, wherein the silicon pillars have the same width.
6. The method of claim 1, wherein a plurality of the trenches have the same width.
7. The method of claim 1, wherein the step of performing a thermal oxidation process on the silicon pillar comprises: dry oxygen oxidation or steam oxidation.
8. The method of forming a trench isolation structure of claim 1, wherein the substrate comprises: single crystal silicon, silicon-on-insulator (SOI), or silicon-on-insulator (SSOI).
9. The method of claim 1, wherein performing a thermal oxidation process on the plurality of silicon pillars to form the silicon dioxide pillars, wherein the silicon dioxide pillars expand to fill the trenches, further comprises: and grinding the silicon dioxide to enable the surface of the silicon dioxide to be flush with the surface of the substrate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211440394.3A CN115775765A (en) | 2022-11-17 | 2022-11-17 | Method for forming trench isolation structure |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211440394.3A CN115775765A (en) | 2022-11-17 | 2022-11-17 | Method for forming trench isolation structure |
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| Publication Number | Publication Date |
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| CN115775765A true CN115775765A (en) | 2023-03-10 |
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| CN202211440394.3A Pending CN115775765A (en) | 2022-11-17 | 2022-11-17 | Method for forming trench isolation structure |
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