Preparation method of image sensor and image sensor
By adopting mask, light resistance Tri-layer structural technology and etching process in the preparation of image sensors, forming high-depth and width-width-ratio ion injection molds, and introducing protective layers in the removal process of covering the mold, solving existing technology, solving existing technology It is difficult to achieve the problem of thick light carvings and high -resolution, which improves the performance of ion injection depth and image sensor, and at the same time protects the base layer of the bottom of the mold groove.
Patent Information
- Application Number
- CN202411311986.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-19
- Publication Date
- 2025-01-24
AI Technical Summary
The prior art is difficult to achieve thick photoresist and high resolution simultaneously in the ion implantation process with high aspect ratio, resulting in a long mask peeling and removal process time, and the etchant is prone to enter the mask groove, destroying the ion implantation zone and devices. Functional layer.
Adopt masses and light-resistant Tri-Layer structural technology combined with etching process. Through specific mask materials and thickness selection, the high-depth and width comparison of ions is injected into the mask, and the protective layer is introduced in the removal process of the mask and removal process to protect the mask The base layer of the bottom of the mold groove.
A high aspect ratio ion implantation mask is realized, which improves the ion implantation depth and the pixel full well capacity, transistor transmission performance and isolation performance of the image sensor, while protecting the substrate functional layer at the bottom of the mask trench.
Smart Images
Figure CN119364883A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for preparing an image sensor. Background Art
[0002] CMOS image sensors (CIS) are currently widely used in the field of image acquisition. As the pixel size decreases, the resolution requirements for photolithography increase accordingly. At the same time, in order to maintain or improve the full well capacity of the image sensor pixel, the transistor transfer performance and the isolation performance, the ion implantation depth of the pixel also needs to be further improved. Therefore, higher requirements are put forward for high aspect ratio masks. At present, in the process of ion implantation, the specific mask aspect ratio is required to be greater than 10 or even greater than 20. However, under the current photolithography process, as the resolution increases, the focus depth decreases, and it is difficult to achieve thick photoresist and high resolution at the same time. The above requirements have exceeded the limits of traditional photoresist. Therefore, under this high aspect ratio process requirement, a multi-layer hard mask technology with a relatively large etching selection is generally used, such as dielectric materials such as silicon oxide or silicon nitride. However, in the subsequent mask stripping, the thicker mask layer stripping and removal process takes a long time, and the stripping etchant has enough time to enter the mask groove and destroy the ion implantation area and the device functional layer in the groove.
[0003] The above and other prior art in the semiconductor processing art demonstrates that it would be beneficial to develop a high aspect ratio ion implantation mask and a technique for removing the high aspect ratio mask without damaging device functional layers in the mask trench features. Summary of the invention
[0004] Based on the above-described problem, the present invention proposes a method for preparing an image sensor.
[0005] On the one hand, the method for preparing an image sensor proposed in the present invention includes: step S1 of forming a mask layer having a groove on a substrate; step S2 of backfilling the groove with a protective layer; and step S3 of removing the mask layer and the protective layer, wherein the protective layer is used to protect the substrate at the bottom of the groove from damage when removing the mask layer.
[0006] Optionally, an ion implantation process is further included between step S1 and step S2.
[0007] Optionally, the mask layer further includes: a first mask layer and a second mask layer formed from bottom to top.
[0008] Optionally, in step S3, firstly, fluorine-based gas is used to etch and remove the second mask layer and a top portion of the protective layer, and then non-fluorine-based gas is used to etch and remove the first mask layer and the remaining protective layer.
[0009] Optionally, the material of the first mask layer is a carbon-based material, the material of the second mask layer is an inorganic dielectric, and the material of the protective layer is selected from a material with strong fluidity; the material of the first mask layer is selected from BARC, PR, SOC or APF, the material of the second mask layer is selected from LTO, SiARC or DARC, and the protective layer is selected from BARC, PR or SOC; the thickness of the first mask layer is 500-50000Å, the thickness of the second mask layer is 10-1000Å, and the thickness of the protective layer is 500-10000Å.
[0010] Optionally, the mask layer further includes: a photoresist, and / or an anti-reflection layer, wherein the anti-reflection layer is BARC or TARC, and the mask layer with the grooves is obtained by photolithography and etching processes.
[0011] Optionally, the aspect ratio of the groove is greater than 10.
[0012] In a second aspect, the present invention proposes another method for preparing an image sensor proposed by the present invention, comprising: step S1: forming a groove on a mask layer located on a substrate, the mask layer comprising at least a first mask layer and a second mask layer from bottom to top, and retaining a predetermined thickness of the first mask layer at the bottom of the groove; step S2: removing the second mask layer; step S3: etching the first mask layer at the bottom of the groove to expose the substrate surface in the groove; step S4: removing the remaining first mask layer.
[0013] Optionally, an ion implantation process is further included between step S3 and step S4.
[0014] Optionally, in the step S2, the second mask layer is removed by etching using a fluorine-based gas; Optionally, in the steps S3 and S4, non-fluorine-based gas is used to etch or remove the first mask layer.
[0015] Optionally, the material selection and thickness selection of the first mask layer and the second mask layer are the same as the above materials.
[0016] Optionally, in step S3, the etching is blanket etching, and the aspect ratio of the trench finally formed in this step is greater than 10.
[0017] Optionally, in step S1, the mask layer further includes: a photoresist, and / or an anti-reflection layer, wherein the anti-reflection layer is BARC or TARC, and the grooves are formed by photolithography and etching processes.
[0018] In addition, the present invention also proposes an image sensor prepared by the above method.
[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) On the one hand, by adopting the mask and photoresist layer Tri-Layer structure technology combined with the etching process, a high aspect ratio ion implantation mask is achieved through the selection of specific mask materials and thickness. The critical dimension (CD) of the ion implantation area is reduced, and the implantation depth is greatly increased, further improving the full well capacity of the image sensor pixel, the transistor transmission performance, and the isolation performance.
[0020] (2) On the other hand, in the mask stripping process, a protective layer is introduced into the mask pattern grooves to protect the substrate functional layer at the bottom of the mask grooves from being damaged.
[0021] (3) In addition, a specific sequence is used to form a patterned mask groove and to strip off and remove the mask layer. In a mask layer stripping and removal process, another mask is used to protect the substrate at the bottom of the groove, which can further protect the substrate functional layer at the bottom of the mask groove from damage. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings of the present invention constitute a part of this specification and are used to further understand the present invention. The drawings illustrate embodiments of the present invention and together with the description are used to explain the principle of the present invention.
[0023] Figure 1 This is a flow chart of preparing the ion implantation region of the image sensor according to Example 1 of the present invention.
[0024] Figure 2A , 2B 2C, 2D, 2E, and 2F are cross-sectional schematic diagrams of the image sensor preparation process according to Example 1.
[0025] Figure 3 This is a flow chart of preparing the ion implantation region of the image sensor according to Embodiment 2 of the present invention.
[0026] Figure 4A , 4B 4C, 4D, 4E, and 4F are cross-sectional schematic diagrams of the image sensor preparation process according to Example 2. DETAILED DESCRIPTION
[0027] The following detailed descriptions are all illustrative and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.
[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. Example
[0029] Figure 1 This is a flow chart of preparing the ion implantation region of the image sensor according to Example 1 of the present invention. Figure 2A , 2B 2C, 2D, 2E, and 2F are cross-sectional schematic diagrams of the image sensor preparation process according to Example 1.
[0030] The method for preparing the image sensor comprises the following steps: Step S1: forming a mask layer having grooves on a substrate; Step S2: backfilling the trench with a protective layer; Step S3: removing the mask layer and the protective layer.
[0031] In a preferred embodiment, the specific preparation process is as follows Figure 1 The following combination Figures 2A-2F A method for manufacturing the image sensor of this embodiment will be described.
[0032] Referring to 2A , processes 110 , 120 , and 130 are performed to provide a substrate 101 , sequentially form a first mask layer 103 and a second mask layer 104 on the substrate, and then form a patterned photoresist layer 105 on the second mask layer 104 .
[0033] The substrate 101 is a silicon substrate, and may also be a germanium substrate, a silicon germanium substrate, SOI (Silicon On Insulator) or GOI (Germanium On Insulator), etc., and certain doping particles may be injected into the semiconductor substrate according to design requirements to change electrical parameters. The substrate 101 may further include a photodiode formation region, and an oxide layer 102 may be provided on the substrate surface to reduce the tunneling effect of ion implantation. In a specific embodiment, a 60Å oxide layer, such as silicon oxide, is deposited on the substrate surface. The oxide layer may be obtained by direct deposition or by thinning after the previous process. The first mask layer 103 is usually made of a material that can be stripped by oxygen plasma dry etching, such as BARC, PR, SOC, APF, etc. The oxygen plasma dry etching stripping process causes less damage to the substrate, and the deposition thickness is generally between 500Å and 50,000Å. In a specific embodiment, taking BARC as an example, the deposition thickness is 10,000Å. The first mask layer can be deposited by a simple spin coating method. The second mask layer 104 is usually made of a material with a high etching selectivity to the first mask layer 103. Common second mask layer materials such as LTO, SiARC, DARC, etc. generally have a thickness between 10Å and 1000Å. In a specific embodiment, taking LTO as an example, the deposition thickness is 100Å. The second mask layer can be deposited by low-temperature CVD. The etching selectivity of the first mask layer and the second mask layer is preferably 20:1, so that a mask with a high aspect ratio can be obtained. Conventional photolithography, exposure, and development can be used to obtain a corresponding patterned photoresist layer 105. An anti-reflection layer can be further included between the photoresist layer 105 and the second mask layer 104. The anti-reflection layer is BARC or TARC, such as 800Å anti-reflection BARC and 2000Å photoresist layer PR. The critical dimension (CD) of the photoresist layer pattern is generally between 0.05μm and 0.4μm. In a specific embodiment, the CD is 0.1μm.
[0034] refer to Figure 2B , perform process 140, use the photoresist layer 105 as a mask, etch the second mask layer 104 and the first mask layer 103 in sequence, until the upper surface of the substrate is exposed, and form a mask layer with a groove 106. Preferably, dry etching is used. Since the first mask layer 103 has a high etching selectivity to the second mask layer 104, when the first mask layer 103 is fully opened, the second mask layer 104 is still retained, forming a high aspect ratio ion implantation mask.
[0035] refer to Figure 2C , executing process 150, using the first mask layer and the second mask layer as masks, performing an ion implantation process to form an ion implantation region 107. The ion implantation is a global / blanket ion implantation.
[0036] refer to Figure 2D , perform process 160, and backfill the trench 106 with the protective layer 108. The protective layer 108 is preferably a material with strong fluidity, which can be prepared by spin coating, such as BARC, PR, SOC, etc., and its deposition thickness h is generally between 500-10000Å, preferably 2000Å.
[0037] refer to Figure 2E , 2F , perform processes 170 and 180 to remove the second mask layer 104 and the top portion of the protective layer 108, preferably using a global / blanket dry etching method, and the etching gas is a fluorine-containing gas. Then, preferably, a non-fluorine gas such as oxygen is used for dry stripping to remove the first mask layer 103 and the remaining protective layer 108, and the attached Figure 2F Device.
[0038] The method of this embodiment prepares a high aspect ratio mask, reduces the critical dimension (CD) of the ion implantation area, and greatly increases the implantation depth. At the same time, the introduction of a protective layer during the removal process of the high aspect ratio mask can effectively prevent the substrate functional layer in the mask groove from being exposed to the mask etchant atmosphere, thereby protecting the substrate functional layer from the influence of the mask stripping and removal process. Example
[0039] Figure 3 This is a flow chart of preparing the ion implantation region of the image sensor according to Embodiment 2 of the present invention. Figure 4A , 4B 4C, 4D, 4E, and 4F are cross-sectional schematic diagrams of the image sensor preparation process according to Example 2.
[0040] The method for preparing the image sensor comprises the following steps: Step S1: forming a groove on a mask layer located on a substrate, wherein the mask layer comprises at least a first mask layer and a second mask layer from bottom to top, and a predetermined thickness of the first mask layer is retained at the bottom of the groove; Step S2: removing the second mask layer; Step S3: etching the first mask layer at the bottom of the trench to expose the surface of the substrate in the trench; Step S4: removing the remaining first mask layer.
[0041] In a preferred embodiment, the specific preparation process is as follows Figure 3 The following combination Figures 4A-4F A method for manufacturing the image sensor of this embodiment will be described.
[0042] Reference Figure 4A, perform processes 310, 320, and 330, provide a substrate 201, sequentially form a first mask layer 203 and a second mask layer 204 on the substrate, and then form a patterned photoresist layer 205 on the second mask layer 204. The above process and materials are exactly the same as those in Example 1, and will not be described in detail here.
[0043] Reference Figure 4B , execute process 340, use the photoresist layer 205 as a mask, etch the second mask layer 204 and the first mask layer 203 in sequence, and form a groove 206. The first mask layer with a predetermined thickness d is retained at the bottom of the groove 206. The predetermined thickness d is 500Å~50000Å, and is 1000Å in a specific embodiment. The etching method preferably adopts dry etching. Since the first mask layer 203 has a high etching selectivity to the second mask layer 204, a high aspect ratio groove is formed after this process.
[0044] Reference Figure 4C , execute process 350, in the same etching equipment as process 340, change the etching atmosphere, use fluorine-based gas to completely etch the second mask layer 204, at this time, a certain thickness of the first mask layer 203 is still retained at the bottom of the groove. Figure 4D , executing process 360, switching the etching atmosphere again, such as oxygen, and using a global / blanket dry etching method to etch the first mask layer 203 until the substrate 201 at the bottom of the trench is exposed.
[0045] Reference Figure 4E , perform process 370 to perform ion implantation. Then perform process 380, preferably using oxygen etching to remove the first mask layer 203, to obtain the attached Figure 4F Device.
[0046] The method of this embodiment prepares a mask with a high aspect ratio, reduces the critical dimension (CD) of the ion implantation area, and greatly increases the implantation depth. At the same time, in the mask layer stripping and removal process of this embodiment, since the second mask layer generally contains silicon, it is easy to damage the silicon substrate at the bottom of the trench when the second mask layer is stripped and removed. Therefore, retaining the first mask layer of a predetermined thickness at the bottom of the trench can protect the substrate functional layer at the bottom of the trench from being affected by the second mask stripping and removal process.
[0047] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of the present invention. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and corrections to the present invention. Such modifications, improvements and corrections are suggested in the present invention, so such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of the present invention.
[0048] It should be understood that the embodiments described in the present invention are only used to illustrate the principles of the embodiments of the present invention. Other variations may also fall within the scope of the present invention. Therefore, as examples and not limitations, alternative configurations of the embodiments of the present invention may be considered consistent with the teachings of the present invention. Accordingly, the embodiments of the present invention are not limited to the embodiments explicitly introduced and described in the present invention.
Claims
1. A method for preparing an image sensor, characterized in that: include: Step S1: forming a mask layer having grooves on a substrate; Step S2: backfilling the groove with a protective layer; Step S3: removing the mask layer and the protective layer, wherein the protective layer is used to protect the surface of the substrate at the bottom of the groove from being damaged when removing the mask layer.
2. The method for preparing an image sensor according to claim 1, characterized in that: An ion implantation process is also included between step S1 and step S2.
3. The method for preparing an image sensor according to claim 1, characterized in that: The mask layer further includes: a first mask layer and a second mask layer formed from bottom to top; in the step S3, the second mask layer and a top portion of the protective layer are first removed, and then the first mask layer and the remaining protective layer are removed.
4. The method for preparing an image sensor according to claim 3, characterized in that: In the step S3, the second mask layer and the top portion of the protective layer are firstly removed by etching with a fluorine-based gas, and then the first mask layer and the remaining protective layer are removed by etching with a non-fluorine-based gas.
5. The method for preparing an image sensor according to claim 4, characterized in that: The material of the first mask layer is a carbon-based material, the material of the second mask layer is an inorganic dielectric, and the material of the protective layer is selected from materials with strong fluidity.
6. The method for preparing an image sensor according to claim 5, characterized in that: The material of the first mask layer is selected from BARC, PR, SOC or APF, the material of the second mask layer is selected from LTO, SiARC or DARC, and the protection layer is selected from BARC, PR or SOC.
7. The method for preparing an image sensor according to claim 6, characterized in that: The thickness of the first mask layer is 500-50000Å, the thickness of the second mask layer is 10-1000Å, and the thickness of the protective layer is 500-10000Å.
8. The method for preparing an image sensor according to claim 1, characterized in that: The mask layer further includes: a photoresist and / or an anti-reflection layer, wherein the anti-reflection layer is a BARC or a TARC.
9. The method for preparing an image sensor according to claim 8, characterized in that: The mask layer with the grooves is obtained by photolithography and etching processes.
10. The method for preparing an image sensor according to claim 1, characterized in that: The aspect ratio of the trench is greater than 10.
11. A method for preparing an image sensor, characterized in that: include: Step S1: forming a groove on a mask layer located on a substrate, wherein the mask layer includes at least a first mask layer and a second mask layer from bottom to top, and a predetermined thickness of the first mask layer is retained at the bottom of the groove; Step S2: removing the second mask layer; Step S3: etching the first mask layer at the bottom of the trench to expose the surface of the substrate in the trench; Step S4: removing the remaining first mask layer.
12. The method for preparing an image sensor according to claim 11, characterized in that: An ion implantation process is also included between step S3 and step S4.
13. The method for preparing an image sensor according to claim 11, characterized in that: In the step S2, the second mask layer is removed by etching using a fluorine-based gas.
14. The method for preparing an image sensor according to claim 13, characterized in that: In the steps S3 and S4, non-fluorine-based gas is used to etch or remove the first mask layer.
15. The method for preparing an image sensor according to claim 14, characterized in that: The material of the first mask layer is a carbon-based material, and the material of the second mask layer is an inorganic dielectric.
16. The method for preparing an image sensor according to claim 15, characterized in that: The material of the first mask layer is selected from BARC, PR, SOC or APF, and the material of the second mask layer is selected from LTO, SiARC or DARC.
17. The method for preparing an image sensor according to claim 16, characterized in that: The thickness of the first mask layer is 500-50000Å, the thickness of the second mask layer is 10-1000Å, and the predetermined thickness is 500-5000Å.
18. The method for preparing an image sensor according to claim 11, characterized in that: In the step S3, the etching is blanket etching, and the aspect ratio of the trench finally formed in this step is greater than 10.
19. The method for preparing an image sensor according to claim 11, characterized in that: In step S1, the mask layer further includes: a photoresist, and / or an anti-reflection layer, wherein the anti-reflection layer is BARC or TARC.
20. The method for preparing an image sensor according to claim 19, characterized in that: In step S1 , a groove is formed by using photolithography and etching processes.
21. An image sensor obtained by the preparation method according to any one of claims 1 to 20.