Novel structure in silicon-based capacitor and manufacturing method

Abstract

The invention discloses a novel structure in a silicon-based capacitor and a manufacturing method. The novel structure comprises a deep groove entering a substrate from the surface of the substrate; and the side wall of the deep groove is provided with a zigzag surface appearance along the depth direction. According to the invention, the surface area of the deep trench can be increased, so that the capacitance value and density in unit area are improved, and the stability of the device performance is ensured at the same time.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor integrated circuit technology, and in particular to a novel structure and manufacturing method of a silicon-based capacitor. Background Art

[0002] Compared with traditional ceramic capacitors, silicon-based capacitors (Si-Cap) have gradually become high-end alternatives to ceramic capacitors due to their advantages such as high density, miniaturization, low insertion loss, high integration, high stability and high reliability. However, how to provide a larger capacitance value in a small silicon-based capacitor is an important factor affecting the application of silicon-based capacitors.

[0003] Silicon-based capacitors use semiconductor technology to form deep trenches on silicon substrates, which can achieve high-density stacking of multiple layers of capacitor materials in the deep trenches. Since the surface area of ​​the capacitor layer has a greater impact on the capacitance value, the deeper the trench, the higher the capacitance value can be provided. The mainstream etching technology for manufacturing deep trenches, such as BOSCH etching technology, is greatly restricted by its aspect ratio (AR) process capability, which greatly restricts silicon-based capacitors from pursuing higher capacitance density per unit area. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects in the prior art and provide a new structure and manufacturing method of a silicon-based capacitor.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] The present invention provides a novel structure in a silicon-based capacitor, comprising:

[0007] A deep trench extending from a surface of a substrate into the substrate;

[0008] The sidewall of the deep trench has a sawtooth surface morphology along the depth direction, which is used to increase the surface area of ​​the deep trench and improve the capacitance value.

[0009] Furthermore, the sawtooth surface is formed by mapping a plurality of rhombuses or a plurality of pairs of Σ-shaped boundaries with openings facing each other stacked in the depth direction onto the sidewalls on both sides of the deep groove.

[0010] Furthermore, two side walls on opposite sides of the deep groove have the sawtooth surfaces which are symmetrical along the depth direction.

[0011] Furthermore, a vertex corner of the rhombus or a pair of top ends of the Σ-shape closest to the top of the deep trench passes through the surface of the substrate to form a top opening of the deep trench with a constricted shape.

[0012] Furthermore, a bottom corner of the rhombus or a pair of bottom ends of the Σ shapes closest to the bottom of the deep trench intersect and are mapped onto the bottom of the deep trench to form a bottom of the deep trench with a pointed shape; or, a bottom corner of the rhombus or a pair of bottom ends of the Σ shapes closest to the bottom of the deep trench pass through the bottom of the deep trench and form a bottom surface of the deep trench parallel to the surface of the substrate between the passing points on both sides.

[0013] Furthermore, the substrate includes 110 a silicon substrate.

[0014] Furthermore, the sidewall of the deep trench forms the serrated surface by the angle of the (111) crystal plane of the 110 silicon and / or the angle between the (111) crystal plane and the (110) crystal plane; the bottom surface of the deep trench forms a pointed morphology by the angle of the (111) crystal plane of the 110 silicon, or forms a planar morphology parallel to the surface of the 110 silicon substrate by the angle between the (111) crystal plane and the (100) crystal plane.

[0015] The present invention also provides a method for manufacturing a novel structure in a silicon-based capacitor, comprising:

[0016] providing a substrate;

[0017] forming a deep trench on a surface of the substrate and extending into the substrate;

[0018] A sawtooth surface topography is formed on the sidewall of the deep trench along the depth direction to increase the depth and surface area of ​​the deep trench.

[0019] Further, the substrate includes a 110 silicon substrate; the deep trench entering the 110 silicon substrate is formed on the surface of the 110 silicon substrate by using a BOSCH etching technique; the inner wall surface of the deep trench is processed by using an etching technique with different crystal planes, so that the side wall of the processed deep trench has the sawtooth surface morphology formed by the angle of the (111) crystal plane of the 110 silicon and / or the angle between the (111) crystal plane and the (110) crystal plane, and the bottom surface of the processed deep trench has a pointed angle morphology formed by the angle of the (111) crystal plane of the 110 silicon, or a plane morphology parallel to the surface of the 110 silicon substrate formed by the angle between the (111) crystal plane and the (100) crystal plane.

[0020] Furthermore, tetramethylammonium hydroxide is used to perform anisotropic wet etching treatment on the inner wall surface of the deep trench, and the sharp corner morphology or the plane morphology at the bottom of the deep trench is formed by adjusting the wet etching treatment time.

[0021] It can be seen from the above technical scheme that the present invention can increase the surface area of ​​the deep trench by forming a deep trench with a sawtooth surface morphology sidewall along the depth direction (formed by diamond-shaped (Diamond-Shape) stacking or Σ shape (Sigma-Shape) stacking, so that after filling each capacitor layer material in the deep trench, the contact area of ​​the capacitor layer in the deep trench can be significantly increased, thereby improving the capacitance value of the device. In addition, by using a 110 silicon substrate, and after forming a deep trench by using a mainstream dry etching process (such as a BOSCH etching process), the inner wall surface of the deep trench is processed by a wet etching process (such as a tetramethylammonium hydroxide (TMAH) wet etching process) with different crystal planes, and a deep trench with a diamond stack or a Σ shape stack is produced, the depth and surface area of ​​the deep trench can be further improved without changing the BOSCH etching process capability, thereby affecting the material contact surface area during the subsequent stacking process of filling the dielectric layer and the conductive layer in the deep trench, thereby improving the capacitance value and density per unit area. At the same time, by utilizing the original crystal plane characteristics of the silicon-based substrate, the silicon spike surface defects generated on the trench sidewalls after BOSCH etching can also be repaired, ensuring the stability of device performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1-Figure 2 It is a schematic diagram of a novel structure in a silicon-based capacitor according to a preferred embodiment of the present invention.

[0023] Figure 3-Figure 5 The figure is a schematic diagram of the process steps of a method for manufacturing a novel structure in a silicon-based capacitor according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0025] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0026] refer to Figure 1A novel structure in a silicon-based capacitor of the present invention includes a substrate 10 and a deep trench 11 disposed in the substrate 10 .

[0027] The deep trench 11 is disposed on the upper surface of the substrate 10, and the bottom of the deep trench 11 extends downward from the upper surface of the substrate 10 into the substrate 10. The sidewall of the deep trench 11 has a sawtooth surface 15 along the depth direction of the deep trench 11. Since the sidewall of the deep trench 11 is not a straight line morphology, but has a plurality of sawtooth fold line morphologies with repeated turns, the surface area of ​​the deep trench 11 is significantly increased. When the capacitor layer material is filled in the deep trench 11 along the inner wall of the deep trench 11, the contact area of ​​the capacitor layer in the trench can be significantly increased, thereby increasing the capacitance value.

[0028] refer to Figure 1 In some embodiments, the serrated surface 15 on the sidewall of the deep trench 11 can be regarded as formed by mapping the boundaries of multiple diamond shapes 12 (diamond-shapes) stacked (overlapped) along the depth direction of the deep trench 11 on the sidewalls of the deep trench 11 .

[0029] Alternatively, the serrated surface 15 on the sidewall of the deep trench 11 can also be considered to be formed by mapping the boundaries of multiple pairs of Sigma-Shape structures with openings facing each other and stacked along the depth direction of the deep trench 11 on the sidewalls of the deep trench 11 .

[0030] In some embodiments, the sidewalls on two opposite sides of the deep trench 11 have a serrated surface 15 that is symmetrical along the depth direction of the deep trench 11. In other words, the vertical diagonal of each stacked rhombus 12 corresponding to the serrated surface 15 of the sidewall of the deep trench 11 coincides with the axis of the deep trench 11. Alternatively, two Σ shapes 13 in each pair of stacked Σ shapes 13 corresponding to the serrated surface 15 of the sidewall of the deep trench 11 are symmetrically distributed on both sides of the axis of the deep trench 11.

[0031] In some embodiments, among the stacked rhombuses 12, the top corner of a rhombus 12 closest to the top of the deep trench 11 passes through the upper surface of the substrate 10, thereby forming a top opening of the deep trench 11 with a necked shape on the upper surface of the substrate 10 (or, the separated top ends of a pair of Σ shapes 13 closest to the top of the deep trench 11 pass through the upper surface of the substrate 10, thereby forming a top opening of the deep trench 11 with a necked shape on the upper surface of the substrate 10).

[0032] The bottom corner of a rhombus 12 closest to the bottom of the deep trench 11 protrudes from the bottom of the deep trench 11, so that a planar bottom surface 14 of the deep trench 11 parallel to the upper surface of the substrate 10 is formed between the protrusion points (connecting lines) of the two rhombus 12 sides on the left and right sides (or, the separated bottom ends of a pair of Σ shapes 13 closest to the bottom of the deep trench 11 protrude from the bottom of the deep trench 11, so that a planar bottom surface 14 of the deep trench 11 parallel to the upper surface of the substrate 10 is formed between the protrusion points (connecting lines) of the bottom ends of the two Σ shapes 13 on the left and right sides).

[0033] Alternatively, the bottom angle of a rhombus 12 closest to the bottom of the deep trench 11 is completely mapped on the bottom of the deep trench 11, forming a pointed bottom 16 of the deep trench 11 with a pointed shape corresponding to the bottom of the rhombus 12 (or, the bottom ends of a pair of Σ shapes 13 closest to the bottom of the deep trench 11 intersect and are completely mapped on the bottom of the deep trench 11, forming a pointed bottom 16 of the deep trench 11 with a pointed shape corresponding to the intersecting bottom ends), such as Figure 2 shown.

[0034] refer to Figure 1 In some embodiments, the substrate 10 includes a 110 silicon (wafer) substrate 10. The upper surface of the 110 silicon (wafer) substrate 10 is parallel to the (100) crystal plane. The sidewall of the deep trench 11 forms a serrated surface 15 due to the angle between the (111) crystal plane of the 110 silicon.

[0035] Alternatively, the sidewall of the deep trench 11 may form a serrated surface 15 due to the included angle between the (111) crystal plane and the (110) crystal plane of 110 silicon.

[0036] Alternatively, the sidewall of the deep trench 11 may also form a sawtooth surface 15 by the angle between the (111) crystal plane of 110 silicon and the angle between the (111) crystal plane and the (110) crystal plane.

[0037] In some embodiments, the bottom surface of the deep trench 11 is formed by the angle between the (111) crystal plane and the (100) crystal plane of the 110 silicon to form a planar bottom surface 14 parallel to the upper surface of the 110 silicon substrate 10 .

[0038] Alternatively, the bottom surface of the deep trench 11 is formed into a pointed bottom 16 by the angle (inner angle) of the (111) crystal plane of 110 silicon, such as Figure 2 shown.

[0039] The rhombus 12 or Σ-shaped 13 morphology structure on the sidewall of the deep trench 11 is a sawtooth boundary (sawtooth surface 15) morphology formed by the angle of the (111) crystal plane of 110 silicon or the angle between the (111) crystal plane and the (110) crystal plane. A pointed boundary (pointed bottom 16) morphology is formed at the bottom of the deep trench 11 by the angle of the (111) crystal plane (the bottom angle of a rhombus 12 closest to the bottom of the deep trench 11 or the bottom intersection angle of a pair of Σ-shaped 13 closest to the bottom of the deep trench 11), or a plane boundary (plane bottom surface 14) morphology is formed by the angle between the (111) crystal plane and the (100) crystal plane.

[0040] After each capacitor layer material is filled in the deep trench 11, it can be used to form a silicon-based capacitor. By using this structure of the present invention, the contact area of ​​the capacitor layer in the deep trench 11 can be increased, and the capacitance value can be improved.

[0041] The following is a further detailed description of a novel structure manufacturing method in a silicon-based capacitor of the present invention through specific implementation modes and in conjunction with the accompanying drawings.

[0042] refer to Figure 3-Figure 4 The novel structure manufacturing method of the silicon-based capacitor of the present invention can be used to manufacture the above-mentioned Figure 1 A novel structure in a silicon-based capacitor is shown and may include the following steps:

[0043] Step S1: providing a substrate 10 .

[0044] like Figure 3 As shown, a conventional 110 silicon wafer substrate 10 is used to manufacture a novel structure in a silicon-based capacitor of the present invention.

[0045] Step S2 : forming a deep trench 11 on the surface of the substrate 10 and penetrating into the substrate 10 .

[0046] like Figure 3 As shown, first, a deep trench 11 is formed on the upper surface ((100) crystal plane) of the silicon substrate 10 by using the mainstream BOSCH etching technology.

[0047] It can be seen that the deep trench 11 formed after BOSCH etching has a boundary structure similar to the arc shape 17 at the sidewall edge. In addition, after BOSCH etching, a surface defect of silicon spike 18 will be generated on the sidewall at the junction of two adjacent arc shapes 17 of the deep trench 11.

[0048] It can also be seen that the deep trench 11 formed after BOSCH etching has a (110) crystal plane along the vertical direction at the opening sidewall of the top of the deep trench 11 and at the bottom of the sidewall of the arc shape 17 .

[0049] Step S3 : forming a sawtooth surface 15 on the sidewall of the deep trench 11 along the depth direction.

[0050] like Figure 4 As shown, the inner wall surface of the deep trench 11 is then processed using a wet etching technique with anisotropy of the crystal planes.

[0051] For example, tetramethylammonium hydroxide (TMAH) can be used as a chemical solution for wet etching, and the anisotropic property of each crystal plane when TMAH etches silicon 110 can be utilized to implement anisotropic wet etching of each crystal plane on the inner wall surface of the deep trench 11 .

[0052] After the wet etching is completed, the sidewall of the deep trench 11 treated with TMAH will have a sawtooth surface 15 morphology of a rhombus 12 stack (or Σ-shaped 13 stack) formed by the angle of the (111) crystal plane of 110 silicon and / or the angle of the (111) crystal plane and the (110) crystal plane (reference Figure 1 ).

[0053] Furthermore, the bottom surface of the deep trench 11 has a planar bottom surface 14 parallel to the upper surface of the 110 silicon substrate 10 and formed by the angle between the (111) crystal plane and the (100) crystal plane.

[0054] contrast Figure 3 It can be seen that after the TMAH treatment, the depth of the deep trench 11 has increased to a certain extent. Therefore, the present invention can increase the trench depth and surface area without changing the aspect ratio process capability of the BOSCH process, thereby increasing the contact area of ​​the capacitor layer filled in the deep trench 11, thereby improving the capacitance value.

[0055] It can also be seen that after the TMAH treatment, the silicon spike 18 defect caused by BOSCH etching has been eliminated by the TMAH treatment, and the side wall of the deep trench 11 is replaced by a regularly turned broken line morphology (serrated surface 15 morphology) instead of a circular arc 17. Thus, the inherent crystal plane characteristics of the silicon-based substrate 10 are utilized to almost perfectly repair the silicon spike 18 surface defect that appears at the boundary of the circular arc 17 on the side wall of the deep trench 11 after BOSCH etching.

[0056] According to different needs, the process parameters during TMAH treatment, such as the time of wet etching treatment, can be adjusted to form, for example, Figure 4 ( Figure 1 ) shows that the bottom of the deep trench 11 is a planar bottom surface 14 formed by the angle between the (111) crystal plane and the (100) crystal plane of 110 silicon.

[0057] Alternatively, by increasing the TMAH wet etching treatment time, it is also possible to form, for example Figure 5( Figure 2 ) shows that the bottom of the deep trench 11 has a pointed bottom 16 formed by the angle of the (111) crystal plane of 110 silicon.

[0058] In summary, the present invention can increase the surface area of ​​the deep trench 11 by forming a deep trench 11 with a serrated surface 15 sidewall along the depth direction (formed by stacking diamond 12 or Σ-shaped 13). Therefore, after filling the deep trench 11 with various capacitor layer materials, the contact area of ​​the capacitor layer in the deep trench 11 can be significantly increased, thereby improving the capacitance value of the device. Furthermore, by adopting a 110 silicon substrate 10, and in the silicon-based capacitor process step, first using a mainstream dry etching process such as a BOSCH etching process to form a deep trench 11, and then using the characteristics of anisotropic etching of each crystal plane of a TMAH wet etching process, the inner wall surface of the deep trench 11 is further processed to produce a deep trench 11 with a rhombus 12 stack or a Σ-shaped 13 stack. Under the condition that the original process capability of the BOSCH etching is not changed, the depth and surface area of ​​the deep trench 11 can be further improved, thereby affecting the material contact surface area during the subsequent stacking process of filling the dielectric layer and the conductive layer in the deep trench 11, thereby improving the capacitance value and density per unit area. In addition, the original crystal plane characteristics of the 110 silicon-based substrate 10 can also be used to repair the silicon spike 18 surface defects generated on the side wall of the trench after the BOSCH etching, thereby further ensuring the stability of the device performance.

[0059] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A novel structure in a silicon-based capacitor, characterized in that: include: A deep trench extending from a surface of a substrate into the substrate; The sidewall of the deep trench has a sawtooth surface morphology along the depth direction, which is used to increase the surface area of ​​the deep trench and improve the capacitance value.

2. The novel structure in the silicon-based capacitor according to claim 1 is characterized in that: The sawtooth surface is formed by mapping a plurality of rhombuses or a plurality of pairs of Σ-shaped boundaries with openings facing each other stacked in the depth direction onto the sidewalls of both sides of the deep trench.

3. The novel structure in the silicon-based capacitor according to claim 1 is characterized in that: The two side walls at opposite sides of the deep trench have the sawtooth surfaces symmetrical along the depth direction.

4. The novel structure in the silicon-based capacitor according to claim 2, characterized in that: A vertex corner of the rhombus or a pair of top ends of the Σ-shape closest to the top of the deep trench protrudes from the surface of the substrate to form a top opening of the deep trench with a constricted shape.

5. The novel structure in the silicon-based capacitor according to claim 2, characterized in that: The bottom corner of the rhombus or the bottom ends of a pair of Σ shapes closest to the bottom of the deep trench intersect and are mapped onto the bottom of the deep trench to form a bottom of the deep trench with a pointed shape; or, the bottom corner of the rhombus or the bottom ends of a pair of Σ shapes closest to the bottom of the deep trench pass through the bottom of the deep trench and form a bottom surface of the deep trench parallel to the surface of the substrate between the passing points on both sides.

6. The novel structure in the silicon-based capacitor according to claim 1, characterized in that: The substrate includes 110 a silicon substrate.

7. The novel structure in the silicon-based capacitor according to claim 6, characterized in that: The sidewalls of the deep trench are formed into the serrated surface by the angle of the (111) crystal plane of the 110 silicon and / or the angle between the (111) crystal plane and the (110) crystal plane; the bottom surface of the deep trench is formed into a pointed angle by the angle of the (111) crystal plane of the 110 silicon, or is formed into a planar morphology parallel to the surface of the 110 silicon substrate by the angle between the (111) crystal plane and the (100) crystal plane.

8. A method for manufacturing a novel structure in a silicon-based capacitor, characterized in that: include: providing a substrate; forming a deep trench on a surface of the substrate and extending into the substrate; A sawtooth surface topography is formed on the sidewall of the deep trench along the depth direction to increase the depth and surface area of ​​the deep trench.

9. The method for manufacturing a novel structure in a silicon-based capacitor according to claim 8, characterized in that: The substrate includes a 110 silicon substrate; the deep trench entering the 110 silicon substrate is formed on the surface of the 110 silicon substrate by using a BOSCH etching technique; The inner wall surface of the deep trench is processed by using an etching technology with different crystal planes, so that the side wall of the deep trench after processing has the sawtooth surface morphology formed by the angle of the (111) crystal plane of the 110 silicon and / or the angle between the (111) crystal plane and the (110) crystal plane, and the bottom surface of the deep trench after processing has the pointed angle morphology formed by the angle of the (111) crystal plane of the 110 silicon, or the plane morphology parallel to the surface of the 110 silicon substrate formed by the angle between the (111) crystal plane and the (100) crystal plane.

10. The method for manufacturing a novel structure in a silicon-based capacitor according to claim 9, characterized in that: Tetramethylammonium hydroxide is used to perform anisotropic wet etching treatment on the inner wall surface of the deep trench, and the sharp corner morphology or the plane morphology at the bottom of the deep trench is formed by adjusting the wet etching treatment time.

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