Shallow trench isolation structure and forming method thereof

Abstract

The invention provides a shallow trench isolation structure and a forming method thereof, the shallow trench isolation structure comprises a first isolation layer formed in a first shallow trench of a substrate, the first isolation layer is provided with a second shallow trench, and the stress of the first isolation layer to the substrate is tensile stress; the second shallow trench is filled with the second isolation layer, and the second isolation layer is used for providing pressure stress to balance and relieve the tensile stress generated by the first isolation layer, so that the tensile stress generated by the first isolation layer to the substrate is counteracted, the tensile stress of the shallow trench isolation structure to the substrate is adjusted, the OSE effect is improved, and the performance and yield of the device are improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a shallow trench isolation structure and a forming method thereof. Background Art

[0002] As the feature size of semiconductor components continues to shrink, the isolation area between components must also be reduced accordingly to prevent short circuits between adjacent components. Shallow trench isolation (STI) technology has become the mainstream isolation technology in current semiconductor device manufacturing. As the aspect ratio of shallow trenches increases, the technical difficulty of filling the shallow trenches with isolation layers also increases. Currently, the method for forming a shallow trench isolation structure includes: first, forming a shallow trench in a substrate; then, using a high aspect ratio process or flowable chemical vapor deposition to fill an isolation layer in the shallow trench to form a shallow trench isolation structure. However, the isolation layer filled in the shallow trench will shrink in volume after film formation or during subsequent curing, that is, the isolation layer filled in the shallow trench is a tensile stress film. Therefore, STI will generate tensile stress on the substrate, causing the threshold voltage (Vt) of the metal gate on the substrate to drift, and OSE (Oxide space effect) will also occur, resulting in a decrease in the threshold voltage (Vt), transconductance (gm) and saturation current (Ids) of the device, thereby affecting the performance and yield of the device. Summary of the Invention

[0003] The object of the present invention is to provide a shallow trench isolation structure and a method for forming the same, so as to adjust the tensile stress of the shallow trench isolation structure on the substrate.

[0004] To achieve the above object, the present invention provides a shallow trench isolation structure, comprising:

[0005] A first isolation layer is formed in a first shallow trench of a substrate, wherein the first isolation layer has a second shallow trench, and the stress exerted by the first isolation layer on the substrate is tensile stress;

[0006] The second isolation layer fills the second shallow trench, and the second isolation layer is used to provide compressive stress.

[0007] Optionally, in the shallow trench isolation structure, the material of the first isolation layer includes silicon oxide, and the material of the second isolation layer includes silicon nitride.

[0008] Optionally, in the shallow trench isolation structure, the first isolation layer covers the sidewalls and the bottom of the first shallow trench, and the top surface of the first isolation layer is flush with the top surface of the second isolation layer.

[0009] Based on the same inventive concept, the present invention also provides a method for forming a shallow trench isolation structure, comprising:

[0010] Providing a substrate having a first shallow trench therein;

[0011] forming a first isolation layer, wherein the first isolation layer is formed in the first shallow trench, the first isolation layer has a second shallow trench, and the stress exerted by the first isolation layer on the substrate is tensile stress; and

[0012] A second isolation layer is formed, where the second isolation layer fills the second shallow trench and is used to provide compressive stress.

[0013] Optionally, in the method for forming the shallow trench isolation structure, the material of the first isolation layer includes silicon oxide; and the material of the second isolation layer includes silicon nitride.

[0014] Optionally, in the method for forming the shallow trench isolation structure, the method for forming the first shallow trench in the substrate includes:

[0015] forming a pad oxide layer and a hard mask layer in sequence on the substrate, wherein the pad oxide layer covers the substrate; and

[0016] The hard mask layer, the pad oxide layer and the substrate are sequentially etched to form the first shallow trench.

[0017] Optionally, in the method for forming the shallow trench isolation structure, the method for forming the first isolation layer includes:

[0018] forming a first isolation material layer by using a high aspect ratio process or a flowable chemical vapor deposition process, wherein the first isolation material layer fills the first shallow trench and extends to cover the hard mask layer;

[0019] planarizing the first isolation material layer to a top surface of the hard mask layer;

[0020] The first isolation material layer is etched back to form the first isolation layer and the second shallow trench.

[0021] Optionally, in the method for forming the shallow trench isolation structure, the method of etching back the first isolation material layer includes:

[0022] forming a patterned protection layer on the first isolation material layer, wherein the patterned protection layer has an opening, the opening exposing a portion of the first isolation material layer, and the width of the opening is smaller than the width of the first shallow trench;

[0023] Using the patterned protective layer as a mask, a dry etching process is used to etch back the first isolation material layer to form the first isolation layer and the second shallow trench, wherein the first isolation layer covers the sidewalls and bottom of the first shallow trench, and the depth of the second shallow trench is one twentieth to one half of the depth of the first shallow trench; and

[0024] The patterned protective layer is removed.

[0025] Optionally, in the method for forming the shallow trench isolation structure, the method for forming the second isolation layer includes:

[0026] forming a second isolation material layer, wherein the second isolation material layer fills the second shallow trench and extends to cover a top surface of the first isolation layer and a top surface of the hard mask layer;

[0027] planarizing the second isolation material layer to the top surface of the hard mask layer to expose the top surface of the first isolation layer;

[0028] etching the exposed first isolation layer so that a top surface of the first isolation layer is lower than a top surface of the hard mask layer; and

[0029] The hard mask layer and a portion of the second isolation material layer are removed to form the second isolation layer, wherein a top surface of the second isolation layer is flush with a top surface of the first isolation layer.

[0030] Optionally, in the method for forming the shallow trench isolation structure, the second isolation material layer is formed by a plasma enhanced atomic layer deposition process with a process temperature of 350° C. to 550° C., a pressure of 10 Torr to 30 Torr, and a power of 500W to 1200W.

[0031] In the shallow trench isolation structure and formation method provided by the present invention, the shallow trench isolation structure includes a first isolation layer formed in a first shallow trench of a substrate, the first isolation layer has a second shallow trench, and the stress of the first isolation layer on the substrate is tensile stress; the second isolation layer fills the second shallow trench, and the second isolation layer is used to provide compressive stress to balance and relieve the tensile stress generated by the first isolation layer, thereby offsetting the tensile stress generated by the first isolation layer on the substrate, thereby achieving the adjustment of the tensile stress of the shallow trench isolation structure on the substrate, improving the OSE effect, and improving the performance and yield of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic cross-sectional view of a shallow trench isolation structure according to an embodiment of the present invention;

[0033] Figure 2 1 is a schematic flow chart of a method for forming a shallow trench isolation structure according to an embodiment of the present invention;

[0034] Figures 3 to 13 A schematic cross-sectional view of a structure formed in a method for forming a shallow trench isolation structure according to an embodiment of the present invention;

[0035] The description of the accompanying drawings is as follows:

[0036] 100 - substrate; 101 - pad oxide layer; 102 - hard mask layer; 110 - first shallow trench; 111 - liner layer; 120 - first isolation material layer; 120a - first isolation layer; 130 - patterned protection layer; 130a - opening; 140 - second shallow trench; 150 - second isolation material layer; 150a - second isolation layer; 160 - active area. DETAILED DESCRIPTION

[0037] The following is a further detailed description of the shallow trench isolation structure and its formation method proposed by the present invention, in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are highly simplified and not to exact scale, and are intended solely to facilitate and clearly illustrate the embodiments of the present invention.

[0038] Figure 1 FIG is a schematic cross-sectional view of a shallow trench isolation structure according to an embodiment of the present invention. Figure 1 As shown, the shallow trench isolation structure provided in this embodiment includes a first isolation layer 120a and a second isolation layer 150a.

[0039] Specifically, the first isolation layer 120a is formed in the first shallow trench 110 of the substrate, the first isolation layer 120a has a second shallow trench 140, and the stress of the first isolation layer 120a on the substrate 100 is tensile stress.

[0040] It should be noted that the material of the substrate 100 in this embodiment can be silicon, for example, single crystal silicon, polycrystalline silicon, amorphous silicon, silicon germanium compound or silicon-on-insulator (SOI), etc., or other materials known to those skilled in the art. <100> Crystalline silicon substrate.

[0041] In this embodiment, the first shallow trench 110 in the substrate 100 extends through a portion of the thickness of the substrate 100. The cross-section of the first shallow trench 110 is an inverted trapezoid. The first isolation layer 120a covers the sidewalls and bottom of the first shallow trench 110. The top surface of the first isolation layer 120a may be higher than the top surface of the substrate 100.

[0042] In this embodiment, the material of the first isolation layer 120a includes silicon oxide. Since the first isolation layer 120a is in contact with the substrate 100 (i.e., the sidewalls and bottom of the first shallow trench 110), the first isolation layer 120a is made of silicon oxide, and the interface fusion degree with the sidewalls and bottom of the first shallow trench 110 is high, so that the interface stability between the first isolation layer 120a and the substrate 100 is high.

[0043] like Figure 1 As shown, the second isolation layer 150a fills the second shallow trench 140 and is used to provide compressive stress. The second isolation layer 150a completely fills the second shallow trench 140. In this way, the compressive stress generated by the second isolation layer 150a can offset the tensile stress generated by the first isolation layer 120a on the substrate 100, thereby adjusting the tensile stress of the shallow trench isolation structure on the substrate 100, improving the OSE effect, and enhancing device performance and yield.

[0044] In this embodiment, the material of the second isolation layer 150a is different from that of the first isolation layer 120a. The material of the second isolation layer 150a includes silicon nitride. Silicon nitride has good adhesion and can effectively transmit compressive stress, thereby balancing and alleviating the tensile stress generated by the first isolation layer 120a, thereby offsetting the tensile stress of the first isolation layer 120a on the substrate 100. Silicon nitride also has good electrical isolation effect and high interface stability with the first isolation layer 120a.

[0045] In this embodiment, the top surface of the second isolation layer 150a is higher than the top surface of the substrate 100. The top surface of the second isolation layer 150a can be flush with the top surface of the first isolation layer 120a, which is beneficial to improving the isolation performance of the shallow trench isolation structure.

[0046] Figure 2 FIG. 1 is a flow chart of the method for forming a shallow trench isolation structure provided in this embodiment. Figure 2 As shown, the method for forming the shallow trench isolation structure provided in this embodiment includes:

[0047] Step S1: providing a substrate having a first shallow trench;

[0048] Step S2: forming a first isolation layer, wherein the first isolation layer is formed in the first shallow trench, the first isolation layer has a second shallow trench, and the stress of the first isolation layer on the substrate is tensile stress; and

[0049] Step S3: forming a second isolation layer, where the second isolation layer fills the second shallow trench and is used to provide compressive stress.

[0050] Figures 3 to 13The following is a schematic cross-sectional view of the structure formed in the method for forming a shallow trench isolation structure according to an embodiment of the present invention. Figures 3 to 13 The method for forming the shallow trench isolation structure provided in this embodiment is described in more detail.

[0051] refer to Figure 3 In step S1, a substrate 100 is provided, wherein the substrate 100 has a first shallow trench 110. Specifically, the method for forming the first shallow trench 110 in the substrate 100 includes:

[0052] A pad oxide layer 101 is formed on the top surface of the substrate 100 using a thermal oxidation process to relieve stress on the substrate 100 during subsequent hard mask layer deposition. The pad oxide layer 101 may be made of silicon oxide and may have a thickness of, for example, 20 angstroms to 80 angstroms.

[0053] Next, a hard mask layer 102 is formed on the substrate 100. The hard mask layer 102 covers the substrate 100. The material of the hard mask layer 102 may be silicon nitride and may be formed by a furnace process. The thickness of the hard mask layer may be 500 angstroms to 700 angstroms. Then, the hard mask layer 102, the pad oxide layer 101, and the substrate 100 are sequentially etched to form the first shallow trench 110. The hard mask layer 102 and the substrate 100 may be sequentially etched by a dry etching process.

[0054] In this embodiment, the first shallow trench 110 extends through a portion of the thickness of the substrate 100. The cross-section of the first shallow trench 110 is an inverted trapezoid, i.e., the cross-sectional area of ​​the first shallow trench 110 gradually increases from the bottom of the first shallow trench 110 to the notch of the first shallow trench 110. The depth of the first shallow trench 110 may be 1000 angstroms to 3000 angstroms.

[0055] Then, if Figure 8 As shown, step S2 is performed to form a first isolation layer 120a. The first isolation layer 120a is formed in the first shallow trench 110. The first isolation layer 120a has a second shallow trench 140. The stress exerted by the first isolation layer 120a on the substrate 100 is tensile stress. The material of the first isolation layer 120a includes silicon oxide.

[0056] like Figure 4As shown, before forming the first isolation layer 120a, a liner layer 111 may be formed in the first shallow trench 110 to buffer the tensile stress of the subsequently formed first isolation layer 120a on the substrate 100. The liner layer 111 covers the bottom of the first shallow trench 110 and extends to cover the sidewalls of the substrate 100 in the first shallow trench 110. The material of the liner layer 111 may be silicon oxide and may be formed using a thermal oxidation process.

[0057] After forming the lining layer 111, a first isolation layer 120a is formed, that is, the first isolation layer 120a covers the lining layer 111. Specifically, the method of forming the first isolation layer 120a includes:

[0058] First, if Figure 5 As shown, a first isolation material layer 120 is formed using a high aspect ratio process (HARP) or a flowable chemical vapor deposition process (FCVD). The first isolation material layer 120 fills the first shallow trench 110 and extends to cover the hard mask layer 102. The material of the first isolation material layer 120 may be silicon oxide, so that the interface between the first isolation material layer 120 and the first shallow trench is highly integrated, thereby enhancing the interface stability between the first isolation layer 120a and the substrate 100. Furthermore, the stress generated by the first isolation material layer 120 on the substrate 100 is tensile stress, that is, the first isolation material layer 120 will shrink in volume after film formation, thereby generating tensile stress on the substrate 100.

[0059] Then, if Figure 6 As shown, the first isolation material layer 120 is planarized to the top surface of the hard mask layer 102. Specifically, the first isolation material layer 120 can be planarized by a chemical mechanical polishing process (CMP) so that the top surface of the first isolation material layer 120 is flush with the top surface of the hard mask layer 102.

[0060] Then, if Figure 9 As shown, the first isolation material layer 120 is etched back by a dry etching process to form the first isolation layer 120a and the second shallow trench 140, that is, the first isolation material layer 120 on the sidewalls and bottom of the first shallow trench 110 is retained to form the first isolation layer 120a. The dry etching process can be a plasma etching process or a chemical gas etching (Certas) process, but is not limited thereto, and can also be other dry etching processes known to those skilled in the art. It should be noted that Figure 9 The depths of the second shallow trench 140 and the first shallow trench 110 shown in FIG. 1 are only for the purpose of facilitating understanding of the difference in depths between the two shallow trenches, and do not represent the actual depth difference between the two shallow trenches.

[0061] In this embodiment, the method for etching back the first isolation material layer 120 includes: first, Figure 7 As shown, a patterned protective layer 130 is formed on the first isolation material layer 120. The patterned protective layer 130 has an opening 130a therein. The opening 130a exposes a portion of the first isolation material layer 120, and the width of the opening 130a is smaller than the width of the first shallow trench 110. The material of the patterned protective layer 130 can be photoresist or spin-on carbon (SOC).

[0062] Afterwards, if Figure 8 As shown, using the patterned protective layer 130 as a mask, a dry etching process is used to etch back the first isolation material layer 120 to form the first isolation layer 120a and the second shallow trench 140, wherein the first isolation layer 120a covers the sidewalls and bottom of the first shallow trench 110. The depth of the etch-back of the first isolation material layer 120 can be 50 angstroms to 200 angstroms, that is, the depth of the second shallow trench 140 can be 50 angstroms to 1500 angstroms.

[0063] Then, if Figure 9 As shown, the patterned protection layer 130 is removed, wherein the patterned protection layer 130 can be removed by an ashing process or a wet cleaning method.

[0064] In this embodiment, the second shallow trench 140 is located in the first isolation layer 120a and can define the position of the subsequently formed second isolation material layer 150. The cross-sectional shape of the second shallow trench 140 can be an inverted trapezoid, that is, the cross-sectional area of ​​the second shallow trench 140 gradually increases from the bottom of the second shallow trench 140 to the notch of the second shallow trench 140.

[0065] It should be noted that if the depth of the second shallow trench 140 is too small, the thickness of the second isolation layer 150a formed subsequently will be too small, making it difficult to provide sufficient compressive stress. Therefore, the depth of the second shallow trench 140 is between one twentieth and one half of the depth of the first shallow trench 110, preferably between one twentieth and one tenth, so that the second isolation layer 150a formed subsequently in the second shallow trench 140 can provide sufficient compressive stress.

[0066] Next, refer to Figure 1 , step S3 is performed to form a second isolation layer 150a. The second isolation layer 150a fills the second shallow trench 140 and is used to provide compressive stress. The compressive stress provided by the second isolation layer 150a can balance and alleviate the tensile stress generated by the first isolation layer 120a, thereby offsetting the tensile stress generated by the first isolation layer 120a on the substrate 100. This can adjust the tensile stress of the shallow trench isolation structure on the substrate 100, improve the OSE effect, and enhance the performance and yield of the device.

[0067] In this embodiment, the method for forming the second isolation layer 150a includes the following steps 1 to 4:

[0068] Step 1: If Figure 10 As shown, a second isolation material layer 150 is formed by a plasma-enhanced atomic layer deposition process (PEALD). The second isolation material layer 150 fills the second shallow trench 140 and extends to cover the top surface of the first isolation layer 120a and the top surface of the hard mask layer 102.

[0069] In this embodiment, the material of the second isolation material layer 150 includes silicon nitride. During the formation of the second isolation material layer 150, the plasma-enhanced atomic layer deposition process uses process gases including diiodosilane (SiH2I2), nitrogen (N2), and hydrogen (H2). The diiodosilane flow rate is 0.01 ml to 0.05 ml, the nitrogen flow rate is 5 slpm to 20 slpm, and the hydrogen flow rate is 2 sccm to 10 sccm. The process temperature is 350°C to 550°C, for example, 350°C, 400°C, 500°C, or 550°C. The pressure is 10 Torr to 30 Torr, and the power is 500 W to 1200 W. Thus, the second isolation material layer 150 forms a compressive stress film, thereby providing compressive stress to balance and alleviate the tensile stress generated by the first isolation layer 120a.

[0070] Step 2: If Figure 11 As shown, the second isolation material layer 150 is planarized to the top surface of the hard mask layer 102 to expose the top surface of the first isolation layer 120a. The second isolation material layer 150 can be planarized using a chemical mechanical polishing process to make the top surface of the second isolation material layer 150 flush with the top surface of the hard mask layer 102.

[0071] Step 3: If Figure 12As shown, the exposed first isolation layer 120a is etched so that the top surface of the first isolation layer 120a is lower than the top surface of the hard mask layer 102. Before etching the exposed first isolation layer 120a, the thickness of the second isolation material layer 150 to be removed in the subsequent wet etching process (i.e., in step 4) can be calculated based on the etch rate ratio of the hard mask layer 102 and the second isolation material layer 150, thereby obtaining a predetermined etching thickness a. Then, the first isolation layer 120a is etched based on the predetermined etching thickness a so that the etched thickness of the first isolation layer 120a is equal to the thickness of the second isolation material layer 150 to be removed in the subsequent wet etching process, thereby ensuring that the top surface of the first isolation layer 120a after etching is flush with the top surface of the subsequently formed second isolation layer 150a.

[0072] In this embodiment, after etching the exposed first isolation layer 120a, the top surface of the first isolation layer 120a is lower than the top surface of the hard mask layer 102 and higher than the top surface of the pad oxide layer 101 to avoid the occurrence of side groove defects between the second shallow trench 140 and the substrate 100.

[0073] In this embodiment, the exposed first isolation layer 120a can be etched using a wet etching process, and the etching solution used in the wet etching process can be hydrofluoric acid. In other embodiments, the exposed first isolation layer 120a can be etched using a dry etching process, including but not limited to a SiCONi etching process (silicon-based composite material etching process) or a chemical gas etching (Certas) process, to avoid damaging the adjacent second isolation material layer 150. The predetermined etching thickness a of the first isolation layer 120a can be 50 angstroms to 600 angstroms. Furthermore, after etching the first isolation layer 120a, a portion of the sidewalls of the second isolation material layer 150 is also exposed, i.e., a groove is formed between the hard mask layer 102 and the second isolation material layer 150, which facilitates the subsequent etching of the second isolation material layer 150 and the removal of the hard mask layer 102.

[0074] Step 4: If Figure 1 As shown, the hard mask layer 102 and a portion of the second isolation material layer 150 are removed to form the second isolation layer 150a. The top surface of the second isolation layer 150a is flush with the top surface of the first isolation layer 120a. Because the second isolation layer 150a has compressive stress, it can balance and relieve the tensile stress generated by the first isolation layer 120a, thereby offsetting the tensile stress generated by the first isolation layer 120a on the substrate 100. This can regulate the tensile stress of the shallow trench isolation structure on the substrate 100, improve the OSE effect, and enhance the performance and yield of the device.

[0075] Specifically, a wet etching process can be used to remove the hard mask layer 102 and a portion of the second isolation material layer 150. The etching solution used can be hot phosphoric acid. During the etching process of the hard mask layer 102 and the second isolation material layer 150, a high etching selectivity is achieved between the second isolation material layer 150 and the first isolation layer 120a, and between the hard mask layer 102 and the first isolation layer 120a. This can reduce or avoid etching damage to the first isolation layer 120a, thereby improving the isolation performance of the shallow trench isolation structure. Furthermore, during the etching process, the etching solution can enter the groove between the hard mask layer 102 and the second isolation material layer 150, causing lateral and vertical etching of the hard mask layer 102, which is conducive to completely removing the hard mask layer 102 and avoiding any residue of the hard mask layer 102.

[0076] Moreover, during the process of etching the hard mask layer 102, the second isolation material layer 150 can also be thinned to a certain extent to reduce the thickness of the second isolation material layer 150 above the top surface of the substrate 100. At the same time, the top surface of the second isolation layer 150a formed after etching can be flush with the top surface of the first isolation layer 120a, which is beneficial to the deposition of subsequent film layers.

[0077] Since the second isolation material layer 150 is formed using a plasma-enhanced atomic layer deposition process, and the hard mask layer 102 is formed using a furnace process, the density and pressure of the second isolation material layer 150 and the hard mask layer 102 are different, and the density of the second isolation material layer 150 is greater than that of the hard mask layer 102. Therefore, when the hard mask layer 102 and the second isolation material layer 150 are etched using a wet etching process, the etching rate of the second isolation material layer 150 is lower than the etching rate of the hard mask layer 102. The etching rate ratio of the second isolation material layer 150 to the hard mask layer 102 can be, for example, 1:1.2:1:2. Therefore, after removing the hard mask layer 102, the top surface of the second isolation material layer 150 is higher than the top surface of the pad oxide layer 101, so that the top surface of the finally formed second isolation layer 150a is higher than the pad oxide layer 101.

[0078] refer to Figure 12 Combined with Figure 1As shown, when the exposed first isolation layer 120a is etched in the aforementioned step 3, the thickness of the first isolation layer 120a removed, i.e., the predetermined etching thickness a, is the same as the thickness of the second isolation material layer 150 removed in the wet etching process (step 4). As a result, the top surface of the ultimately formed second isolation layer 150a is flush with the top surface of the first isolation layer 120a. It should be noted that, in the wet etching process (step 4), the second isolation material layer 150 has a high etching selectivity with the first isolation layer 120a, which can reduce or avoid etching damage to the first isolation layer 120a. Therefore, the first isolation layer 120a is hardly etched during the wet etching process, and the flushness of the top surface of the ultimately formed second isolation layer 150a with the top surface of the first isolation layer 120a is not affected.

[0079] Afterwards, if Figure 13 As shown, ion implantation may be performed on the substrate 100 on both sides of the shallow trench isolation structure to form an active region 160 .

[0080] In summary, it can be seen that in the shallow trench isolation structure and the formation method thereof provided by the embodiment of the present invention, the shallow trench isolation structure includes a first isolation layer formed in a first shallow trench, the first isolation layer has a second shallow trench, and the stress of the first isolation layer on the substrate is tensile stress; the second isolation layer fills the second shallow trench, and the second isolation layer is used to provide compressive stress to balance and relieve the tensile stress generated by the first isolation layer, thereby offsetting the tensile stress generated by the first isolation layer on the substrate, thereby achieving the adjustment of the tensile stress of the shallow trench isolation structure on the substrate, improving the OSE effect, and improving the performance and yield of the device.

[0081] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A shallow trench isolation structure, characterized in that: include: A first isolation layer is formed in a first shallow trench of a substrate, wherein the first isolation layer has a second shallow trench, and the stress exerted by the first isolation layer on the substrate is tensile stress; The second isolation layer fills the second shallow trench, and the second isolation layer is used to provide compressive stress.

2. The shallow trench isolation structure according to claim 1, wherein: The material of the first isolation layer includes silicon oxide, and the material of the second isolation layer includes silicon nitride.

3. The shallow trench isolation structure according to claim 1, wherein: The first isolation layer covers the sidewalls and the bottom of the first shallow trench, and the top surface of the first isolation layer is flush with the top surface of the second isolation layer.

4. A method for forming a shallow trench isolation structure, characterized in that ,include: Providing a substrate having a first shallow trench therein; forming a first isolation layer, wherein the first isolation layer is formed in the first shallow trench, the first isolation layer has a second shallow trench, and the stress exerted by the first isolation layer on the substrate is tensile stress; as well as, A second isolation layer is formed, where the second isolation layer fills the second shallow trench and is used to provide compressive stress.

5. The method for forming a shallow trench isolation structure according to claim 4, wherein: The material of the first isolation layer includes silicon oxide; the material of the second isolation layer includes silicon nitride.

6. The method for forming a shallow trench isolation structure according to claim 4, wherein: The method of forming the first shallow trench in the substrate includes: forming a pad oxide layer and a hard mask layer in sequence on the substrate, wherein the pad oxide layer covers the substrate; and The hard mask layer, the pad oxide layer and the substrate are sequentially etched to form the first shallow trench.

7. The method for forming a shallow trench isolation structure according to claim 6, wherein: The method of forming the first isolation layer includes: forming a first isolation material layer by using a high aspect ratio process or a flowable chemical vapor deposition process, wherein the first isolation material layer fills the first shallow trench and extends to cover the hard mask layer; planarizing the first isolation material layer to a top surface of the hard mask layer; The first isolation material layer is etched back to form the first isolation layer and the second shallow trench.

8. The method for forming a shallow trench isolation structure according to claim 7, wherein: The method of etching back the first isolation material layer includes: forming a patterned protection layer on the first isolation material layer, wherein the patterned protection layer has an opening, the opening exposing a portion of the first isolation material layer, and the width of the opening is smaller than the width of the first shallow trench; Using the patterned protective layer as a mask, a dry etching process is used to etch back the first isolation material layer to form the first isolation layer and the second shallow trench, wherein the first isolation layer covers the sidewalls and bottom of the first shallow trench, and the depth of the second shallow trench is one twentieth to one half of the depth of the first shallow trench; and The patterned protective layer is removed.

9. The method for forming a shallow trench isolation structure according to claim 6, wherein: The method of forming the second isolation layer includes: forming a second isolation material layer, wherein the second isolation material layer fills the second shallow trench and extends to cover a top surface of the first isolation layer and a top surface of the hard mask layer; planarizing the second isolation material layer to the top surface of the hard mask layer to expose the top surface of the first isolation layer; etching the exposed first isolation layer so that a top surface of the first isolation layer is lower than a top surface of the hard mask layer; and The hard mask layer and a portion of the second isolation material layer are removed to form the second isolation layer, wherein a top surface of the second isolation layer is flush with a top surface of the first isolation layer.

10. The method for forming a shallow trench isolation structure according to claim 9, wherein: The second isolation material layer is formed by a plasma enhanced atomic layer deposition process with a process temperature of 350° C. to 550° C., a pressure of 10 Torr to 30 Torr, and a power of 500W to 1200W.

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