Method for manufacturing DTI
During the DTI manufacturing process, after the opening is formed by dry etching, and anisotropic wet etching is used for repair, the problem of poor filling performance caused by poor DTI morphology is solved, and better isolation effect and device performance are achieved.
Patent Information
- Application Number
- CN202510214952.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-25
- Publication Date
- 2025-06-06
AI Technical Summary
When the etching is deep, the existing DTI manufacturing method easily forms a morphology with a wide middle and narrow upper and lower lower, resulting in a hole easily when filling silica, affecting the isolation effect and device performance.
After the DTI opening is formed by dry etching, anisotropic wet etching is used for repair. By etching the medicine liquid with a vertical direction with a rate smaller than the lateral etching rate, the top width of the opening is increased and the morphology is improved.
Improve the morphology of DTI, improve the filling performance, avoid the generation of voids, and thus improve the performance of devices such as CIS products.
Smart Images
Figure CN120109011A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing a semiconductor integrated circuit, and in particular to a method for manufacturing a deep trench isolation (DTI). Background Art
[0002] In order to improve the performance of CIS products and reduce the crosstalk between pixels in CIS products, many CIS products use DTI structures, and the DTI depth used in some CIS products reaches 2.0μm.
[0003] Due to the limitation of dry etching machine capacity, when etching deeper DTI, DTI will present a morphology that is wide in the middle and narrow at the top and bottom. When filling with silicon dioxide, voids will be generated, which will have an adverse effect on performance. Figure 1 As shown, it is a schematic diagram of the structure of the DTI opening formed by the existing DTI manufacturing method; the existing DTI manufacturing method is to use dry etching to etch a semiconductor substrate 101 such as a silicon substrate to obtain an opening 102. Due to the limitation of the dry etching machine capacity, when the depth of the opening 102 is deeper, a morphology that is wide in the middle and narrow at the top and bottom will appear. This morphology is not conducive to the subsequent filling of silicon dioxide in the opening 102 due to the narrow top width of the opening 102, and it is easy to form a cavity, which is not conducive to achieving a good isolation effect and will affect the performance of the device. Summary of the invention
[0004] The technical problem to be solved by the present invention is to provide a method for manufacturing DTI, which can improve the morphology of DTI, thereby improving the filling performance of DTI and improving the performance of products such as CIS products.
[0005] In order to solve the above technical problems, the present invention provides a method for manufacturing DTI comprising the following steps:
[0006] Dry etching is used to form an opening of the DTI in a selected area of the semiconductor substrate, wherein the opening has a shape of being wide in the middle and narrow at the top and bottom.
[0007] The opening is repaired by using anisotropic wet etching, wherein the wet etching uses a liquid having a characteristic that the vertical etching rate is smaller than the lateral etching rate, so that the top width of the opening is increased after the repair is completed.
[0008] A further improvement is that the semiconductor substrate comprises a silicon substrate.
[0009] A further improvement is that the vertical crystal orientation of the silicon substrate is <010> .
[0010] A further improvement is that the wet etching solution is an alkaline solution.
[0011] A further improvement is that the wet etching solution is TMAH or SC1 or a combination of TMAH and SC1.
[0012] A further improvement is that the repair process parameters include: concentration, time and temperature of the drug solution.
[0013] A further improvement is that the repair process parameters also include: etching times.
[0014] A further improvement is that the process parameters of the repair are predetermined through experiments to ensure that the top width of the opening is increased while reducing the impact on the middle width, so as to optimize the morphology of the opening.
[0015] A further improvement is that after the dry etching is completed, the depth of the opening is 1.5 microns to 2 microns.
[0016] Further improvements include:
[0017] An isolation material layer is filled in the opening to form the DTI, and the morphology of the opening ensures that no voids are generated during the process of filling the isolation material layer.
[0018] A further improvement is that the DTI is arranged between pixel units of the CIS.
[0019] After the dry etching forms an opening of the DTI that is wide in the middle and narrow at the top and bottom, the present invention further adds wet etching to repair the opening. The wet etching adopts anisotropy and a slower etching rate in the vertical direction, that is, a direction perpendicular to the surface of the semiconductor substrate. In this way, the top width of the DTI opening can be increased, so that the opening has a morphology of being wide at the top and narrow at the bottom, which is beneficial to the filling of the DTI. Therefore, the present invention can improve the morphology of the DTI, thereby improving the filling performance of the DTI and improving the performance of products such as CIS products. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:
[0021] Figure 1 is a schematic structural diagram of an opening of a DTI formed by an existing DTI manufacturing method;
[0022] Figure 2 is a flow chart of a method for manufacturing DTI according to an embodiment of the present invention;
[0023] Figure 3A-3B It is a schematic diagram of the device structure in each step of the manufacturing method of DTI in an embodiment of the present invention. DETAILED DESCRIPTION
[0024] like Figure 2 FIG. 1 is a flow chart of a method for manufacturing DTI according to an embodiment of the present invention; FIG. 3A to FIG. 3B FIG. 1 is a schematic diagram of the device structure in each step of the manufacturing method of DTI according to an embodiment of the present invention; the manufacturing method of DTI according to an embodiment of the present invention comprises the following steps:
[0025] Step S101: Figure 3A As shown, dry etching is used to form an opening 202 of the DTI in a selected area of the semiconductor substrate 201, and the opening 202 has a morphology of being wide in the middle and narrow at the top and bottom.
[0026] In the embodiment of the present invention, the semiconductor substrate 201 includes a silicon substrate.
[0027] The vertical direction of the silicon substrate, that is, the crystal direction perpendicular to the top surface of the silicon substrate is <010> .
[0028] In some embodiments, after the dry etching is completed, the depth of the opening 202 is 1.5 microns to 2 microns.
[0029] Step S102, repairing the opening 202 by anisotropic wet etching, wherein the wet etching is performed by using a liquid having a characteristic that the vertical etching rate is smaller than the lateral etching rate, so that the top width of the opening 202 after the repair is completed is increased, such as Figure 3A As shown, the area indicated by the dotted circle 203 is the effective area of the repair, and the width of the opening 202 in the area of the dotted circle 203 will be increased, while the width of the bottom of the dotted circle 203 will be basically unaffected. Figure 3B , which is a schematic structural diagram of the opening 202 ′ after the repair is completed. The repaired opening is marked with a mark 202 ′.
[0030] In the embodiment of the present invention, the wet etching solution is an alkaline solution.
[0031] In some embodiments, the wet etching solution is TMAH or SC1 or a combination of TMAH and SC1.
[0032] The final shape of the opening 202' can be adjusted by adjusting the repair process parameters. The repair process parameters include: the concentration, time and temperature of the drug solution.
[0033] The repair process parameters also include: etching times.
[0034] The repairing process parameters are predetermined through experiments to ensure that the top width of the opening 202 is increased while reducing the impact on the middle width, so as to optimize the final morphology of the opening 202 ′.
[0035] In the embodiment of the present invention, it also includes:
[0036] An isolation material layer is filled in the opening 202 to form the DTI. The morphology of the opening 202 ensures that no voids are generated during the process of filling the isolation material layer.
[0037] In some embodiments, the isolation material layer is a single dielectric layer such as a silicon dioxide layer, or a stacked structure of multiple dielectric layers made of different materials, or a stacked structure of a dielectric layer and polysilicon or amorphous silicon.
[0038] In some embodiments, the DTI is disposed between pixel units of the CIS.
[0039] After dry etching is performed to form the opening 202 of the DTI that is wide in the middle and narrow at the top and bottom, the embodiment of the present invention further adds wet etching to repair the opening 202. The wet etching adopts anisotropic etching with a slower etching rate in the vertical direction, i.e., perpendicular to the surface of the semiconductor substrate 201. In this way, the top width of the opening 202 of the DTI can be increased, so that the opening 202 has a morphology of being wide at the top and narrow at the bottom, which is beneficial to the filling of the DTI. Therefore, the embodiment of the present invention can improve the morphology of the DTI, thereby improving the filling performance of the DTI and improving the performance of products such as CIS products.
[0040] In the embodiment of the present invention, in order to improve the performance of CIS products, the DTI morphology is improved to avoid the situation where the top opening of the DTI is too small as much as possible. This is mainly achieved by using the anisotropy of single crystal silicon to widen the top opening of the DTI, and by controlling the etching rate, the DTI morphology is improved to improve the performance.
[0041] In the embodiment of the present invention, the DTI morphology is improved by using several steps of wet etching, and the anisotropy of silicon crystal (silicon in the vertical direction is 010 crystal phase, and the etching rate is slow) and the penetration mechanism of liquid in porous materials can be used to etch the narrowed opening of the top of the DTI, while minimizing the etching of the middle of the DTI. By controlling the etching time, the number of etchings and the concentration of the etching solution, the morphology of the DTI can be adjusted and excessive etching can be avoided.
[0042] The present invention has been described in detail above through specific embodiments, but these do not constitute limitations of the present invention. Without departing from the principle of the present invention, those skilled in the art may also make many variations and improvements, which should also be considered as the protection scope of the present invention.
Claims
1. A method for manufacturing DTI, characterized in that: The steps include: Using dry etching to form an opening of the DTI in a selected area of the semiconductor substrate, wherein the opening has a shape that is wide in the middle and narrow at the top and bottom; The opening is repaired by using anisotropic wet etching, wherein the wet etching uses a liquid having a characteristic that the vertical etching rate is smaller than the lateral etching rate, so that the top width of the opening is increased after the repair is completed.
2. The method for manufacturing DTI according to claim 1, wherein: The semiconductor substrate includes a silicon substrate.
3. The method for manufacturing DTI according to claim 2, wherein: The vertical crystal orientation of the silicon substrate is <010> .
4. The method for manufacturing DTI according to claim 3, wherein: The wet etching solution is alkaline solution.
5. The method for manufacturing DTI according to claim 4, wherein: The wet etching solution is TMAH or SC1 or a combination of TMAH and SC1.
6. The method for manufacturing DTI according to claim 4, wherein: The repair process parameters include: the concentration, time and temperature of the liquid medicine.
7. The method for manufacturing DTI according to claim 6, wherein: The repair process parameters also include: etching times.
8. The method for manufacturing DTI according to claim 6 or 7, characterized in that: The process parameters of the repair are predetermined through experiments to ensure that the top width of the opening is increased while reducing the impact on the middle width, so as to optimize the morphology of the opening.
9. The method for manufacturing DTI according to claim 1, wherein: After the dry etching is completed, the depth of the opening is 1.5 microns to 2 microns.
10. The method for manufacturing DTI according to claim 8, wherein: Also includes: An isolation material layer is filled in the opening to form the DTI, and the morphology of the opening ensures that no voids are generated during the process of filling the isolation material layer.
11. The method for manufacturing DTI according to claim 10, wherein: The DTI is arranged between pixel units of the CIS.