Deep trench isolation structure and manufacturing method thereof
By using a combined process to form three oxide layers at the bottom of deep trenches, the stress concentration problem caused by the sharp corners at the bottom of deep trenches is solved, thereby improving the performance and reliability of semiconductor devices.
Patent Information
- Application Number
- CN202511664153.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-13
- Publication Date
- 2026-02-06
AI Technical Summary
In existing technologies, sharp corners form at the bottom of deep trenches after the oxide layer is grown, leading to stress concentration and affecting the performance and reliability of semiconductor devices.
A combination of a first oxidation process in a chlorine-containing gas atmosphere, a wet oxidation process, and a high-density plasma chemical vapor deposition process is used to form a three-layer oxide layer, eliminating sharp corners and improving the uniformity and coverage of the oxide layer.
It effectively avoids the formation of sharp corners, reduces cracks in the filling material caused by stress accumulation, improves the performance and reliability of the device, and reduces the risk of leakage.
Smart Images
Figure CN121487570A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor integrated circuit technology, and in particular to a deep trench isolation structure and its fabrication method. Background Technology
[0002] In semiconductor manufacturing processes, deep trench isolation (DTI) structures are widely used to achieve electrical isolation between different device regions, thereby improving chip performance and reliability. With the continuous development of semiconductor technology and the shrinking of device dimensions, the performance requirements for deep trench isolation structures are also increasing.
[0003] In existing processes, after etching the deep trench, an oxide layer (Liner Wet OX) is typically grown using a wet oxidation process. Because the bottom of the deep trench is usually rounded, the silicon consumption rate at the rounded bottom is relatively slow during the growth of this oxide layer. This results in a sharp, outward-curving corner forming at the originally smooth bottom structure after growth, such as... Figure 1 As shown. Figure 1 This is a schematic diagram of an electron scanning microscope image after an oxide layer has formed within a deep trench in existing technology. Please refer to it. Figure 1 As shown, a deep trench 2 is formed in the substrate 1, and an oxide layer 3 is formed on the inner wall of the deep trench 2. The bottom of the oxide layer 3 has an outwardly concave sharp corner.
[0004] The presence of such a sharp corner at the bottom can cause many problems. For example, when filling polysilicon (POLY) later, the sharp corner will form a stress concentration point. As the process progresses, the stress will continue to accumulate, which may cause cracks in the filling material and form leakage channels, seriously affecting the performance and reliability of semiconductor devices.
[0005] Therefore, how to effectively eliminate the sharp corners that appear at the bottom of deep trenches after the growth of oxide layers has become an important problem that urgently needs to be solved in semiconductor manufacturing processes. Summary of the Invention
[0006] The purpose of this application is to provide a deep trench isolation structure and its fabrication method, which can avoid the formation of sharp corners when forming the oxide layer, thereby avoiding stress accumulation and improving the stability of the device structure.
[0007] To solve the above-mentioned technical problems, according to the first aspect of this application, a method for manufacturing a deep trench isolation structure is provided, comprising the following steps:
[0008] A substrate is provided in which deep trenches are formed;
[0009] The first oxidation process and the second oxidation process are performed sequentially to form a first oxide layer and a second oxide layer on the sidewall and bottom of the deep trench, respectively. The second oxide layer covers the first oxide layer. The first oxidation process is carried out in an atmosphere containing chlorine gas, and the second oxidation process is wet oxidation.
[0010] A high-density plasma chemical vapor deposition process is performed to form a third oxide layer on the sidewalls and bottom of the deep trench, the third oxide layer covering the second oxide layer; and,
[0011] The deep trench is filled with polycrystalline silicon.
[0012] Optionally, in the first oxidation process, the chlorine-containing gas includes dichloroethylene.
[0013] Optionally, in the second oxidation process, the introduced mixed gas includes oxygen and hydrogen, and the flow ratio of oxygen to hydrogen is 5:5 to 12:5.
[0014] Optionally, the first oxidation process and the second oxidation process are performed in a furnace tube, the temperature of which is 900℃~1000℃.
[0015] Optionally, the total thickness of the first oxide layer and the second oxide layer is 950 Å to 1050 Å; and / or, the thickness of the third oxide layer is 2850 Å to 3150 Å.
[0016] Optionally, the thickness of the first oxide layer is 175 Å to 225 Å, and the thickness of the second oxide layer is 775 Å to 825 Å.
[0017] Optionally, in the high-density plasma chemical vapor deposition process, the mixed gas includes silicon source gas, oxygen, and a gas used to generate high-density plasma.
[0018] To address the aforementioned technical problems, according to a second aspect of this application, a deep trench isolation structure is also provided, manufactured using the method described above for fabricating a deep trench isolation structure, wherein the deep trench isolation structure comprises:
[0019] A substrate in which deep trenches are formed;
[0020] The first oxide layer is located on the sidewalls and bottom of the deep trench;
[0021] A second oxide layer is located on the sidewalls and bottom of the deep trench, and the second oxide layer covers the first oxide layer;
[0022] A third oxide layer is located on the sidewalls and bottom of the deep trench, and the third oxide layer covers the second oxide layer; and,
[0023] Polycrystalline silicon is filled into the deep trench.
[0024] Optionally, the total thickness of the first oxide layer and the second oxide layer is 950 Å to 1050 Å; and / or, the thickness of the third oxide layer is 2850 Å to 3150 Å.
[0025] Optionally, the thickness of the first oxide layer is 175 Å to 225 Å, and the thickness of the second oxide layer is 775 Å to 825 Å.
[0026] In the deep trench isolation structure and its fabrication method provided in this application, a first oxide layer is first formed by a first oxidation process in a chlorine-containing gas atmosphere. The oxide layer formed by the chlorine-containing gas reaction has good step coverage and filling ability, and can be deposited relatively uniformly at the arc at the bottom of the deep trench. In addition, the chlorine element formed during the chlorine-containing gas reaction can effectively remove metal ion contamination, thereby improving the cleanliness and electrical stability of the material. Next, a second oxide layer is formed by wet oxidation. Wet oxidation can oxidize the substrate surface at the bottom of the deep trench relatively uniformly and can be well combined with the first oxide layer to form a relatively uniform initial oxide layer. Then, a third oxide layer is formed by high-density plasma chemical vapor deposition. The third oxide layer formed in this way has the advantages of high density and low stress, and can continue to be deposited uniformly on the initial oxide layer to further fill and cover the deep trench. It can also effectively avoid the generation of new defects or the deterioration of the bottom morphology during the growth process. This application utilizes a combination of a first oxidation process, a second oxidation process, and a high-density plasma chemical vapor deposition process. Without altering the thickness of the traditional oxide layer, it can eliminate the outward-concave sharp corners that easily appear at the bottom of deep trenches after the oxide layer is grown in the traditional process. This reduces stress accumulation-induced cracks in the filling material during polysilicon filling, lowers the risk of leakage current, improves process compatibility, and enhances device performance and reliability. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of an electron scanning microscope image taken after an oxide layer has formed in a deep trench in the prior art.
[0028] Figure 2 This is a schematic flowchart of a method for manufacturing a deep trench isolation structure according to an embodiment of this application.
[0029] Figure 3 This is a schematic diagram of a deep trench isolation structure provided in an embodiment of this application.
[0030] Figure 4 This is a schematic diagram of an electron scanning microscope image of a deep trench after an oxide layer has been formed, provided in one embodiment of this application.
[0031] Explanation of reference numerals in the attached figures:
[0032] Figure 1 In the diagram, 1-substrate; 2-deep trench; 3-oxide layer.
[0033] Figure 3 and Figure 4 In the diagram, 10 is the substrate; 11 is the deep trench; 20 is the oxide layer; 21 is the first oxide layer; 22 is the second oxide layer; 23 is the third oxide layer; and 30 is the polysilicon. Detailed Implementation
[0034] To make the objectives, advantages, and features of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, used only to facilitate and clarify the illustration of the embodiments of this application. Furthermore, the structures shown in the drawings are often part of the actual structures. In particular, different figures may emphasize different aspects and sometimes use different scales.
[0035] As used herein, the singular forms “a,” “an,” and “the” include plural objects unless otherwise expressly indicated. As used herein, the term “or” is generally used to include “and / or” unless otherwise expressly indicated. As used herein, the term “a number” is generally used to include “at least one” unless otherwise expressly indicated. As used herein, the term “at least two” is generally used to include “two or more” unless otherwise expressly indicated. Furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first,” “second,” or “third” may explicitly or implicitly include one or at least two of that feature, unless otherwise expressly indicated.
[0036] Figure 2 This is a flowchart illustrating a method for fabricating a deep trench isolation structure according to an embodiment of this application. Please refer to it. Figure 2 As shown, the method for manufacturing the deep trench isolation structure provided in this application embodiment includes the following steps:
[0037] S1: Provide a substrate in which deep trenches are formed;
[0038] S2: The first oxidation process and the second oxidation process are executed sequentially to form a first oxide layer and a second oxide layer on the sidewall and bottom of the deep trench, with the second oxide layer covering the first oxide layer. The first oxidation process is carried out in an atmosphere containing chlorine gas, and the second oxidation process is wet oxidation.
[0039] S3: Perform a high-density plasma chemical vapor deposition process to form a third oxide layer on the sidewalls and bottom of the deep trench, the third oxide layer covering the second oxide layer; and,
[0040] S4: Fill the deep trench with polycrystalline silicon.
[0041] Figure 3 This is a schematic diagram of a deep trench isolation structure provided in an embodiment of this application. Next, we will combine... Figure 2 and Figure 3 The method for manufacturing a deep trench isolation structure according to an embodiment of this application will be described in detail.
[0042] In step S1, a substrate 10 is provided, in which deep trenches 11 are formed.
[0043] The substrate 10 can be made of silicon, germanium, silicon germanide, silicon carbide, gallium arsenide, gallium nitride, or indium gallium nitride, or it can be silicon-on-insulator or germanium-on-insulator; or it can be other materials, such as gallium arsenide or other III-V compounds. In this embodiment, the substrate 10 is a silicon substrate.
[0044] For example, firstly, a photoresist layer is formed on the substrate 10, then the photoresist layer is exposed and developed to form a patterned photoresist layer. Next, using the patterned photoresist layer as a mask, the substrate 10 is etched. Then, the patterned photoresist layer is removed, ultimately forming a deep trench 11 within the substrate 10. Alternatively, the deep trench 11 can also be formed within an epitaxial layer on the substrate 10.
[0045] In one embodiment of this application, reactive ion etching or inductively coupled plasma etching technology is used to etch the substrate 10. By adjusting parameters such as the type of etching gas, flow rate, etching power and etching time, the depth, width and bottom shape of the deep trench 11 can be controlled to obtain a deep trench 11 with a predetermined depth, width and a rounded bottom, and the deep trench 11 has a smooth surface.
[0046] In step S2, a first oxidation process and a second oxidation process are executed sequentially, forming a first oxide layer 21 and a second oxide layer 22 sequentially on the sidewall and bottom of the deep trench 11. The second oxide layer 22 covers the first oxide layer 21. The first oxidation process is carried out in an atmosphere containing chlorine gas, and the second oxidation process is wet oxidation.
[0047] In one embodiment of this application, the chlorine-containing gas in the first oxidation process includes dichloroethylene. That is, during the execution of the first oxidation process, a mixture of dichloroethylene and oxygen is introduced into the furnace tube, forming a first oxide layer 21 on the sidewalls and bottom of the deep trench 11.
[0048] The second oxidation process is a wet oxidation process, and the mixed gas introduced into the furnace tube includes oxygen and hydrogen. Specifically, during the second oxidation process, after the mixed gas of oxygen and hydrogen is introduced into the furnace tube, a second oxide layer 22 is formed on the sidewalls and bottom of the deep trench 11, and the second oxide layer 22 covers the first oxide layer 21. For example, the flow ratio of oxygen to hydrogen is 5:5 to 12:5, such as 5:5, 6:5, 7:5, 8:5, 9:5, 10:5, 11:5, or 12:5.
[0049] Both the first oxidation process and the second oxidation process are performed in a furnace tube, and the temperature of the furnace tube is 900℃~1000℃, for example, the temperature of the furnace tube is 900℃, 950℃ or 1000℃.
[0050] The total thickness of the first oxide layer 21 and the second oxide layer 22 is 950 Å to 1050 Å, for example, the total thickness of the first oxide layer 21 and the second oxide layer 22 is 950 Å, 1000 Å, or 1050 Å. The thickness ratio of the first oxide layer 21 to the second oxide layer 22 can be 1:3 to 1:5, for example, the thickness ratio of the first oxide layer 21 to the second oxide layer 22 is 1:3, 1:4, or 1:5. The thickness of the first oxide layer 21 is 175 Å to 225 Å, for example, the thickness of the first oxide layer 21 is 175 Å, 200 Å, or 225 Å. The thickness of the second oxide layer 22 is 775 Å to 825 Å, for example, the thickness of the second oxide layer 22 is 775 Å, 800 Å, or 825 Å.
[0051] Both the first oxidation process and the second oxidation process are carried out in a furnace tube. After the first oxidation process is completed in the furnace tube, the second oxidation process can be executed directly.
[0052] The first oxide layer 21 formed by the first oxidation process has good step coverage and filling performance, and can be deposited relatively uniformly at the arc at the bottom of the deep trench 11. Furthermore, the chlorine element formed during the reaction with chlorine gas can effectively remove metal ion contamination, positively impacting subsequent processes, such as improving material cleanliness and electrical stability. In the second oxidation process, the substrate 10 reacts with oxygen to form the second oxide layer 22 (e.g., silicon reacts with water vapor to form silicon oxide). This oxidation method can achieve relatively uniform oxidation of the bottom surface of the substrate 10 and can bond well with the first oxide layer 21 to jointly form a relatively uniform initial oxide layer.
[0053] In one embodiment of this application, the substrate 10 is a silicon substrate, and the materials of the first oxide layer 21 and the second oxide layer 22 are silicon oxide.
[0054] In an exemplary embodiment of this application, a substrate 10 with etched deep trenches 11 is placed in a furnace tube, and a first oxidation process and a second oxidation process are performed sequentially. The temperature of the furnace tube is controlled at 950°C, and a mixture of dichloroethylene and oxygen is introduced to form a first oxide layer 21 with a thickness of 200 Å on the sidewalls and bottom of the deep trenches 11 (dichloroethylene decomposes at high temperature to produce chlorine-containing active substances, which participate in the oxygen reaction and assist in the formation of the first oxide layer 21). Next, a mixture of oxygen and hydrogen is introduced at a total flow rate of 16000 sccm, of which the oxygen flow rate is 11000 sccm and the hydrogen flow rate is 5000 sccm, forming a second oxide layer 22 with a thickness of 800 Å on the first oxide layer 21 on the sidewalls and bottom of the deep trenches 11. The first and second oxidation processes together grow an oxide layer with a total thickness of 1000 Å. The entire process requires precise control of parameters such as reaction time (e.g., approximately 8 hours) and gas flow rate to ensure the quality of the formed oxide layer.
[0055] In the first oxidation process, the chlorine-containing gas reacts and releases chlorine, which can effectively remove metal impurities (such as iron and copper ions) from the furnace tube and the surface of the substrate 10, reducing oxide layer defects. In the second oxidation process, a dense oxide layer is formed through the chemical reaction between the substrate 10 (such as silicon) and water vapor. The two processes work together to ensure the uniformity and quality of the formed oxide layer and the uniformity of the oxide layer coverage at the bottom of the deep trench 11, thus ensuring the insulation performance and structural stability of the oxide layer.
[0056] In step S3, a high-density plasma chemical vapor deposition process is performed to form a third oxide layer 23 on the sidewalls and bottom of the deep trench 11, the third oxide layer 23 covering the second oxide layer 22.
[0057] In this embodiment, a third oxide layer 23 is formed on the sidewalls and bottom of the deep trench 11 using a high-density plasma chemical vapor deposition process, and the third oxide layer 23 covers the second oxide layer 22.
[0058] In the high-density plasma chemical vapor deposition process, the mixed gas used includes a silicon source gas, oxygen, and a gas for generating high-density plasma. The silicon source gas includes, for example, silane, dichlorosilane, or tetraethoxysilane (TEOS). The gas for generating high-density plasma includes, for example, helium or nitrogen. In one embodiment, the flow rate of the silicon source gas is 16000 sccm to 17000 sccm, for example, 16000 sccm, 16500 sccm, or 17000 sccm. The flow rate of oxygen (which may also be ozone) is 13000 sccm to 15000 sccm, for example, 13000 sccm, 14000 sccm, or 15000 sccm. The temperature of the reaction chamber is 400°C to 500°C, for example, 400°C, 430°C, 450°C, 470°C, or 500°C.
[0059] The total thickness of the first oxide layer 21, the second oxide layer 22, and the third oxide layer 23 is 3800 Å to 4200 Å, for example, the total thickness of the first oxide layer 21, the second oxide layer 22, and the third oxide layer 23 is 3800 Å, 4000 Å, or 4200 Å. The thickness of the third oxide layer 23 is 2850 Å to 3150 Å, for example, the thickness of the third oxide layer 23 is 2850 Å, 3000 Å, or 3150 Å.
[0060] In one embodiment of this application, the substrate 10 is a silicon substrate, and the material of the third oxide layer 23 is silicon oxide.
[0061] A third oxide layer 23 is formed using a high-density plasma chemical vapor deposition process. The third oxide layer 23 has the advantages of high density and low stress, and can continue to be deposited uniformly on the initial oxide layer to further fill and cover the deep trench 11. It can also effectively avoid the generation of new defects or the deterioration of the bottom morphology during the growth process.
[0062] A first oxide layer 21 is formed through a first oxidation process, a second oxide layer 22 is formed through a second oxidation process, and a third oxide layer 23 is formed through a high-density plasma chemical vapor deposition process. By combining the first oxidation process, the second oxidation process, and the high-density plasma chemical vapor deposition process, the outward concave sharp corners that are prone to appear at the bottom of the deep trench 11 after the oxide layer is grown in the traditional process can be eliminated without changing the thickness of the traditional oxide layer film. This reduces stress accumulation and cracks in the filling material during subsequent polysilicon filling, reduces the risk of leakage current, improves process compatibility, and enhances the performance and reliability of the device.
[0063] In an exemplary embodiment of this application, the substrate on which the second oxide layer 22 is formed is transferred to a chemical vapor deposition (CVD) apparatus for the growth of a third oxide layer 23. In a high-density plasma chemical vapor deposition (HDPD) process, suitable process parameters are set, such as setting the reaction temperature to 430°C, introducing TEOS at a flow rate of 16500 sccm, ozone at a flow rate of 14000 sccm, and a gas (e.g., helium) for generating high-density plasma. The third oxide layer 23 is formed on the second oxide layer 22 through a plasma-enhanced reaction until the total oxide layer thickness reaches 3800 Å to 4200 Å. In the HDPD process, the precise control function of the CVD apparatus ensures that the third oxide layer 23 is uniformly deposited on the sidewalls and bottom of the deep trench 11, avoiding defects such as voids and cracks.
[0064] Figure 4 This is a schematic diagram of an electron scanning microscope image of a deep trench after an oxide layer has been formed, provided in one embodiment of this application. Please refer to it. Figure 4 As shown, a deep trench 11 is formed in the substrate 10, and an oxide layer 20 is formed in the deep trench 11 (wherein the oxide layer 20 includes a first oxide layer, a second oxide layer and a third oxide layer stacked in sequence). The bottom of the oxide layer 20 has a smooth structure and no sharp corners.
[0065] In step S4, polysilicon 30 is filled into the deep trench 11.
[0066] In this embodiment, polycrystalline silicon 30 is deposited in the deep trench 11 using a chemical vapor deposition process or a physical vapor deposition process. The polycrystalline silicon 30 fills the deep trench 11. The filling quality of the polycrystalline silicon 30 can be ensured by controlling parameters such as deposition temperature, pressure, and gas flow rate.
[0067] Because the three oxide layers are formed by steps S2 and S3, the bottom of the oxide layer does not have sharp corners and can be uniformly filled at a relatively smooth bottom. This reduces stress concentration points and lowers the risk of cracks in the filling material due to stress accumulation in subsequent processes, thereby reducing the possibility of leakage.
[0068] In the method for fabricating the deep trench isolation structure provided in this application embodiment, a first oxide layer 21 is first formed by a first oxidation process in a chlorine-containing gas atmosphere. The first oxide layer 21 formed by the chlorine-containing gas has good step coverage and filling ability, and can be deposited relatively uniformly at the arc at the bottom of the deep trench 11. In addition, the chlorine element formed during the reaction can effectively remove metal ion contamination, which can improve the cleanliness and electrical stability of the material. Then, a second oxide layer 22 is formed by wet oxidation. Wet oxidation can oxidize the surface of the substrate 10 at the bottom of the deep trench 11 relatively uniformly, and can be well combined with the first oxide layer 21 to form a relatively uniform initial oxide layer. Then, a third oxide layer 23 is formed by high-density plasma chemical vapor deposition. The third oxide layer 23 formed thereby has the advantages of high density and low stress, and can continue to be deposited uniformly on the initial oxide layer to further fill and cover the deep trench. It can also effectively avoid the generation of new defects or the deterioration of the bottom morphology during the growth process. This application utilizes a combination of a first oxidation process, a second oxidation process, and a high-density plasma chemical vapor deposition process. Without altering the thickness of the traditional oxide layer, it can eliminate the outward-concave sharp corners that easily appear at the bottom of the deep trench 11 after the oxide layer is grown in the traditional process. This reduces stress accumulation that can cause cracks in the filling material when filling polysilicon 30, lowers the risk of leakage, improves process compatibility, and enhances the performance and reliability of the device.
[0069] By eliminating the sharp corners at the bottom of the deep trench 11 after the oxide layer is formed, the polysilicon 30 can be more evenly distributed at the bottom of the deep trench 11 when it is filled, avoiding stress concentration points at the sharp corners. This significantly reduces the possibility of cracks in the filling material due to stress accumulation in subsequent processes and improves the stability of the semiconductor device structure.
[0070] The elimination of the sharp corners at the bottom of the deep trench 11 reduces stress-induced cracks in the filling material, thereby lowering the probability of leakage current path formation. This improves the electrical performance and reliability of semiconductor devices, making them suitable for applications with extremely stringent leakage current requirements, such as high-performance integrated circuits and automotive electronics.
[0071] In addition, the optimization method of this application improves upon existing semiconductor manufacturing processes, requiring only adjustments to the oxide layer growth process. It does not require the introduction of complex new equipment or new photolithography steps, has good compatibility with existing processes, and is easy to promote and apply in industrial production.
[0072] Meanwhile, semiconductor devices manufactured using the method of this application have been significantly improved in terms of signal transmission stability, power handling capability, and long-term reliability, and can better meet the ever-increasing market demands.
[0073] Accordingly, this application also provides a deep trench isolation structure, which is manufactured using the deep trench isolation structure manufacturing method described above. Please refer to... Figure 3 As shown, the deep trench isolation structure:
[0074] Substrate 10, wherein a deep trench 11 is formed therein;
[0075] The first oxide layer 21 is located on the sidewall and bottom of the deep trench 11;
[0076] The second oxide layer 22 is located on the sidewall and bottom of the deep trench 11, and the second oxide layer 22 covers the first oxide layer 21;
[0077] A third oxide layer 23 is located on the sidewalls and bottom of the deep trench 11, and the third oxide layer 23 covers the second oxide layer 22; and,
[0078] Polycrystalline silicon 30 is filled in the deep trench 11.
[0079] In one embodiment of this application, the total thickness of the first oxide layer 21 and the second oxide layer 22 is 950 Å to 1050 Å, wherein the thickness of the first oxide layer 21 is 175 Å to 225 Å, and the thickness of the second oxide layer 22 is 775 Å to 825 Å. The total thickness of the first oxide layer 21, the second oxide layer 22, and the third oxide layer 23 is 3800 Å to 4200 Å, and the thickness of the third oxide layer is 2850 Å to 3150 Å.
[0080] In one embodiment of this application, the first oxide layer 21, the second oxide layer 22 and the third oxide layer 23 are all silicon oxide layers.
[0081] The deep trench isolation structure and its fabrication method provided in this application are applicable to BCD (Bipolar-CMOS-DMOS, Bipolar Transistor-Complementary Metal-Oxide-Semiconductor-Double-Diffused Metal-Oxide-Semiconductor) process chips or high-voltage power devices, but are not limited to them.
[0082] In summary, the deep trench isolation structure and its fabrication method provided in this application firstly form a first oxide layer through a first oxidation process in a chlorine-containing gas atmosphere. The oxide layer formed by the chlorine-containing gas reaction has good step coverage and filling ability, and can be deposited relatively uniformly at the arc at the bottom of the deep trench. Moreover, the chlorine element formed during the chlorine-containing gas reaction can effectively remove metal ion contamination, thereby improving the cleanliness and electrical stability of the material. Next, a second oxide layer is formed by wet oxidation. Wet oxidation can oxidize the substrate surface at the bottom of the deep trench relatively uniformly and can be well combined with the first oxide layer to form a relatively uniform initial oxide layer. Then, a third oxide layer is formed by high-density plasma chemical vapor deposition. The third oxide layer formed in this way has advantages such as high density and low stress, and can continue to be deposited uniformly on the initial oxide layer to further fill and cover the deep trench. It can also effectively avoid the generation of new defects or the deterioration of the bottom morphology during the growth process. This application utilizes a combination of a first oxidation process, a second oxidation process, and a high-density plasma chemical vapor deposition process. Without altering the oxide layer thickness, it can eliminate the outward-concave sharp corners that tend to appear at the bottom of deep trenches after the oxide layer is grown in conventional processes. This reduces stress accumulation during polysilicon filling, leading to cracks in the filling material, lowers the risk of leakage, improves process compatibility, and enhances device performance and reliability.
[0083] The above description is merely a description of preferred embodiments of this application and is not intended to limit the scope of this application in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.
Claims
1. A method for forming a deep trench isolation structure, the method comprising: The method comprises the following steps: providing a substrate with a deep trench formed therein; sequentially performing a first oxidation process and a second oxidation process to sequentially form a first oxide layer and a second oxide layer on the sidewall and bottom of the deep trench, the second oxide layer covering the first oxide layer, wherein the first oxidation process is oxidation in an atmosphere containing chlorine gas, and the second oxidation process is wet oxidation; performing a high-density plasma chemical vapor deposition process to form a third oxide layer on the sidewall and bottom of the deep trench, the third oxide layer covering the second oxide layer; and filling the deep trench with polysilicon.
2. The method of claim 1, wherein In the first oxidation process, the chlorine-containing gas comprises dichloroethylene.
3. The method of claim 1, wherein: In the second oxidation process, the mixed gas comprises oxygen and hydrogen, and the flow ratio of oxygen to hydrogen is 5:5-12:
5.
4. The method of claim 1, wherein The first oxidation process and the second oxidation process are performed in a furnace tube with a temperature of 900-1000°C.
5. The method of claim 1, wherein The total thickness of the first oxide layer and the second oxide layer is 950-1050 angstroms; and / or the thickness of the third oxide layer is 2850-3150 angstroms.
6. The method of claim 1 or 5, wherein The thickness of the first oxide layer is 175-225 angstroms, and the thickness of the second oxide layer is 775-825 angstroms.
7. The method of claim 1, wherein In the high-density plasma chemical vapor deposition process, the mixed gas comprises a silicon source gas, oxygen, and a gas for generating high-density plasma.
8. A deep trench isolation structure, comprising: The deep trench isolation structure is manufactured by using the method according to any one of claims 1-7, and comprises: a substrate with a deep trench formed therein; a first oxide layer on the sidewall and bottom of the deep trench; a second oxide layer on the sidewall and bottom of the deep trench, the second oxide layer covering the first oxide layer; a third oxide layer on the sidewall and bottom of the deep trench, the third oxide layer covering the second oxide layer; and polysilicon filled in the deep trench.
9. The deep trench isolation structure of claim 8, wherein, The total thickness of the first oxide layer and the second oxide layer is 950-1050 angstroms; and / or the thickness of the third oxide layer is 2850-3150 angstroms.
10. The deep trench isolation structure of claim 8 or 9, wherein, The thickness of the first oxide layer is 175-225 angstroms, and the thickness of the second oxide layer is 775-825 angstroms.