An image sensor and a method for improving yield of an image sensor
By employing a cleaning method that combines etching and baking heat treatment with reduction treatment during the image sensor manufacturing process, the problem of oxygen contamination between metal wires and conductive plugs was solved, improving the cleanliness and electrical performance of the contact interface and increasing the device yield.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GEKKO SEMICON (SHANGHAI) CO LTD
- Filing Date
- 2026-04-27
- Publication Date
- 2026-07-14
Smart Images
Figure CN122396077A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of image sensor technology, and in particular to an image sensor and a method for improving the yield of the image sensor. Background Technology
[0002] As image sensor pixel sizes continue to shrink and integration levels increase, the complexity of their metal interconnect processes is also increasing. Metal interconnect processes typically require the formation of vias (conductive plugs) and metal interconnect lines (e.g., M1, M2, M3, etc.) to achieve electrical connections between nodes. A typical process involves: first, forming conductive plugs within a first dielectric layer on a substrate; then forming a second dielectric layer and a barrier layer on top of this layer; and finally etching trenches (for subsequent metal line filling). The bottom of these trenches exposes the underlying conductive plugs, thus forming an electrical connection channel from the upper metal line to the lower conductive plug.
[0003] In image sensor manufacturing, the quality of the contact interface between the metal wire and the conductive plug is a critical factor affecting device yield. High contact resistance or abnormal structures at this interface are common causes of circuit performance degradation and even chip failure. For example, a specific failure mode, Bin141 (low signal amplitude of the Mobile Industry Processor Interface), was found in image sensors during actual production. Low signal amplitude in the Mobile Industry Processor Interface (MIPI) leads to reduced signal-to-noise ratio, increased power consumption, and consequently, yield loss. Previous analysis confirmed that the MIPI signal amplitude is related to the resistance-capacitance (RC) performance of the contact chain (CT Chain), and the abnormal RC performance of the CT Chain is caused by oxygen contamination at the interface between the metal wire and the conductive plug.
[0004] Extensive research revealed that the oxygen element primarily originates from the interlayer dielectric layer (ILD HARP). Specifically, the ILD HARP material is relatively porous, easily forming microscopic voids during deposition. These voids may contain residual water vapor or other oxygen-containing impurities. During subsequent high-temperature processes, the oxygen from these impurities diffuses upwards and abnormally accumulates at the contact interface between the metal wire and the conductive plug, causing a low MIPI signal amplitude. To address this, various technical methods have been explored to mitigate the oxygen contamination defect, such as: (1) By optimizing the HARP process parameters, the packing density of ILD HARP is increased to reduce micropores, thereby reducing the possibility of residual water vapor or other oxygen-containing impurities.
[0005] (2) By introducing oxygen and inert gas to treat the water vapor, the residual oxygen-containing impurities are converted into oxides (e.g., SiO2) through chemical reaction to repair the micro-pores.
[0006] (3) By adding an additional barrier layer (e.g., a SiN layer or a SiON layer) to physically block the impurities below from continuing to diffuse upward, oxygen contamination at the contact interface between the metal wire and the conductive plug is avoided.
[0007] However, even after the aforementioned technical improvements, practical experience has shown that the circuit performance (e.g., MIPI signal amplitude) of the produced image sensors still fails to meet requirements, resulting in limited improvement in device yield. Therefore, new solutions are needed to further address the oxygen contamination problem at the contact interface between the metal wire and the conductive plug.
[0008] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art. Summary of the Invention
[0009] The purpose of this invention is to provide a method for fabricating an image sensor. Without introducing additional particulate contamination or damaging the device, the polymer residue on the surface of the conductive plug exposed at the bottom of the trench is specifically cleaned after etching to form the trench and before depositing the metal layer in the trench. This significantly improves the cleanliness of the conductive plug surface and prevents it from affecting the interface contact quality of the subsequent metal layer.
[0010] To achieve the above objectives, the present invention provides a method for improving the yield of image sensors, comprising the following steps: A semiconductor structure is provided, the semiconductor structure including a substrate and conductive plugs and trenches formed thereon, wherein the bottom of the trench exposes the conductive plugs, and the trench is used to deposit a metal layer; Prior to depositing the metal layer, a cleaning step is performed on the surface of the conductive plug, the cleaning step comprising etching and / or baking heat treatment: The etching process includes introducing oxygen-containing gas and using plasma etching to remove polymer residues from the surface of the conductive plug; The baking heat treatment includes introducing heat treatment gas and baking the surface of the semiconductor structure to remove polymer residues from the surface of the conductive plug through a chemical oxidation reaction.
[0011] Optionally, in the etching process, the oxygen-containing gas includes at least one of O2, CO, CO2, and SO2.
[0012] Optionally, the etching process parameters include at least: the gas flow rate of the oxygen-containing gas is 500 sccm to 700 sccm; the process temperature is 50℃ to 70℃; and the chamber pressure is 100 mTorr to 200 mTorr.
[0013] Optionally, the etching process time is 20s to 40s.
[0014] Optionally, in the baking heat treatment, the oxygen-containing gas includes O2 and a carrier gas, and the carrier gas includes at least one of nitrogen or an inert gas.
[0015] Optionally, the process parameters of the baking heat treatment include at least: the gas flow rate of O2 is 10000 sccm~12000 sccm; the gas flow rate of the carrier gas is 1000 sccm~1200 sccm; the process temperature is 230℃~320℃; and the chamber pressure is 800 mTorr~1000 mTorr.
[0016] Optionally, the baking heat treatment process time is 30s to 50s.
[0017] Optionally, when the cleaning step includes the etching process and the baking heat treatment, the etching process, the baking heat treatment, and the formation of the trench are performed in the same process chamber.
[0018] Optionally, a semiconductor structure is provided, specifically including: A semiconductor substrate is provided, a first dielectric layer is formed on the semiconductor substrate, and a conductive plug is formed within the first dielectric layer; A barrier layer and a second dielectric layer are formed on the first dielectric layer, and the second dielectric layer and the barrier layer are etched to form the trench, exposing the surface of the conductive plug.
[0019] Optionally, after performing the etching process and / or baking heat treatment, and before depositing the metal layer, a cleaning process is further included, the cleaning process comprising: Reduction treatment: A reducing gas is introduced to remove oxide impurities from the surface of the conductive plug through a chemical reduction reaction; Optionally, after performing the reduction process and before depositing the metal layer, the process further includes: A barrier layer and a seed layer are deposited on the sidewall of the trench.
[0020] Optionally, the reduction process includes: introducing H2 into the chamber where the conductive plug is located, so that H2 reacts with the oxide on the surface of the conductive plug, wherein the H2 flow rate is 150 sccm to 300 sccm, the introduction time is 20 s to 40 s, and the processing temperature is 20 ℃ to 30 ℃.
[0021] Accordingly, the present invention also provides an image sensor manufactured using the above-described method for improving the yield of image sensors.
[0022] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: This invention effectively removes stubborn polymer residues on the surface of conductive plugs that cause interface degradation through etching and / or baking heat treatment. On the one hand, it not only allows the polymer, as a source of contamination, to be specifically decomposed and removed, eliminating its direct physical coverage and insulating barrier effect on the conductive plugs, thereby improving the high contact resistance problem at the interface; on the other hand, it exposes oxide impurities that may be covered or coated by the polymer, thus facilitating the subsequent reduction process to thoroughly remove oxide impurities, thereby significantly reducing the contact resistance at the interface and improving the electrical performance and yield of the image sensor. Specifically, the etching process utilizes oxygen-containing plasma for chemical etching, which effectively decomposes and removes polymer residues; the baking heat treatment removes polymer residues through a high-temperature oxidation reaction between the heat treatment gas and the polymer. Both methods achieve gentle and thorough polymer cleaning, avoiding damage to the device structure or process chamber or the introduction of particulate contamination during the cleaning process.
[0023] Furthermore, after the targeted removal of polymer residues through the etching and / or baking heat treatment, a reduction treatment can be used to remove oxide residues originally covered / coated by the polymer or oxide impurities that may be newly generated during the cleaning process. This invention utilizes an ordered composite cleaning strategy—first targeting the removal of polymers through the etching and / or baking heat treatment, and then targeting the removal of exposed oxide impurities through the reduction treatment—to achieve thorough cleaning of the exposed surfaces of conductive plugs, significantly improving the cleanliness of the contact interface and thus mitigating the problem of increased contact resistance caused by interface contamination. Attached Figure Description
[0024] Figure 1 The image shows a comparison of energy-dispersive X-ray diffraction analysis of different samples; where a represents a sample whose electrical contact performance meets the process requirements, and b represents a sample whose electrical contact performance does not meet the process requirements.
[0025] Figure 2 for Figure 1 Energy dispersive X-ray spectra of contaminants at the interface between the metal wire and the conductive plug in sample b.
[0026] Figure 3 This is a scanning electron microscope (SEM) image of fragment defects caused by physical bombardment cleaning of a sample; where a represents a surface defect image; b represents a SEM image of one defect location in the surface defect image; and c represents a SEM image of another defect location in the surface defect image.
[0027] Figure 4 This invention provides a process flow diagram for a method to improve the yield of an image sensor.
[0028] Figures 5-12 This is a schematic diagram of a partial state of the device in a fabrication method according to an embodiment of the present invention. Detailed Implementation
[0029] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the image sensor proposed in this invention and the method for improving the yield of the image sensor. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of this invention. Please refer to the drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.
[0030] The “oxygen-active particles” mentioned in this article include, but are not limited to, atomic oxygen, oxygen free radicals, charged oxygen ions, and excited oxygen molecules.
[0031] As described in the background section, in the manufacturing of image sensors, the quality of the contact interface between the metal wire and the conductive plug is a key factor affecting device yield. Previous research and analysis have confirmed that one of the key reasons for significant yield loss is oxygen contamination at the interface between the metal wire and the conductive plug. For example, Figure 1 Figure a shows a device whose electrical contact performance meets process requirements; no obvious oxygen distribution is observed at the contact interface between the metal wire and the conductive plug. Figure 1 Figure b shows a device whose electrical contact performance does not meet the process requirements, and obvious oxygen distribution is visible at its contact interface (the defective part D circled in white).
[0032] The inventors' team previously attempted a chemical reduction treatment before depositing the metal layer. This involved introducing H2 into the process chamber, hoping that the H2 would reduce oxygen-containing impurities on the conductive plug surface, thereby removing contaminants. However, in actual production, it was found that even after this treatment, a large number of devices still failed to meet process requirements for electrical contact performance. Energy Dispersive X-ray Spectroscopy (EDS) analysis was performed on the devices obtained using this method, revealing that devices with electrical contact performance meeting process requirements (e.g., [example device name missing]) Figure 1 In (as shown in a), no obvious oxygen distribution was observed at the contact interface between the metal wire and the conductive plug; while devices whose electrical contact performance does not meet the process requirements (e.g., [example]) Figure 1 As shown in Figure b), a clear distribution of oxygen is still visible at the contact interface (the defective part D circled in white). This indicates that chemical reduction treatment with H2 cannot effectively solve the oxygen contamination problem at this contact interface.
[0033] Further specific compositional analysis of the oxygen-containing impurities present at the contact interface yielded the following results: Figure 2 As shown in the image, the characteristic X-ray peaks of C, O, and F elements were clearly detected, indicating the presence of significant organic polymer (e.g., fluorocarbon polymers or carbon-oxygen fluoropolymers) residue at the contact interface. These organic polymers likely originated from the previous etching process. Since etching to form trenches requires a patterned photoresist layer as a mask, and this photoresist layer undergoes partial reaction under the etching gas, generating non-volatile fluorocarbon polymers or carbon-oxygen fluoropolymers, these adhere to the bottom of the trench, forming a dense capping layer. This hinders sufficient contact between H2 and the oxide impurities beneath the fluorocarbon polymer, preventing the chemical reduction reaction from proceeding completely.
[0034] Furthermore, the inability to thoroughly clean oxide impurities caused by polymer overlay is exacerbated in more advanced interconnect layers. Specifically, in the second metal layer (M2), third metal layer (M3), and subsequent processes, the required photoresist layer is thicker than that in the first metal layer (M1) process to achieve smaller dimensions or higher aspect ratios. This results in an increase in the formation of organic polymers during etching, leading to a thicker overlay layer at the bottom of the trench, which significantly increases the risk of failure in the chemical reduction process.
[0035] Based on the above analysis, interfacial contaminants are actually a composite structure with organic polymers as the surface layer and oxides as the bottom layer. Existing chemical reduction methods can only remove exposed oxides, but cannot effectively break down the polymer barrier on the surface, let alone remove the oxides covered by the polymer. Therefore, to achieve thorough cleaning of the interface, it is necessary to first remove the organic polymers covering the surface, fully exposing the underlying oxide impurities, and then remove oxygen through a reduction reaction.
[0036] To address this, a physical bombardment method was attempted for cleaning, specifically involving inert gas sputtering (e.g., Ar sputtering) to break down the surface polymer barrier. While this method effectively removes most organic polymer residues, in practice, it was found that intense physical bombardment causes the stripped polymer or dielectric material to splatter as slice defects. These micron-sized fragments can not only fall back onto the device surface but also splash onto the instrument surface, depositing inside the chamber and causing contamination. Ultimately, this leads to numerous uncontrollable defects 301 in the fabricated device. Figure 3 As shown in a. Further magnified observation of the defect location using a scanning electron microscope reveals clearly fragmented residues, such as... Figure 3 As shown in b and c.
[0037] Therefore, cleaning processes should meet the following requirements: efficient removal, avoidance of physical debris generation, and clean and controllable process. Since physical bombardment inherently suffers from debris problems due to its mechanism, a shift towards chemical reaction-based cleaning pathways is necessary.
[0038] To address the aforementioned issues, this invention, at the critical process point between trench etching to expose the conductive plug and metal layer deposition, abandons the physical bombardment method that easily generates debris. Instead, it employs chemical reaction-based etching and / or baking heat treatment as cleaning steps. These two methods cause the polymer to decompose into gaseous products through chemical reactions, thereby achieving complete removal of the organic polymer without generating solid debris. Furthermore, a reduction treatment can be combined to remove exposed oxides, achieving comprehensive interface cleaning while avoiding physical damage, ultimately improving interface quality and product yield.
[0039] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.
[0040] like Figure 4 As shown, the present invention provides a method for improving the yield of image sensors, comprising the following steps: Step 1, providing a semiconductor structure, the semiconductor structure including a substrate and conductive plugs and trenches formed thereon, wherein the bottom of the trench exposes the conductive plugs, and the trench is used to deposit a metal layer.
[0041] Step 2, prior to depositing the metal layer, performs a cleaning step on the surface of the conductive plug, the cleaning step comprising etching and / or baking heat treatment: The etching process includes introducing oxygen-containing gas and using plasma etching to remove polymer residues from the surface of the conductive plug; The baking heat treatment includes introducing heat treatment gas and baking the surface of the semiconductor structure to remove polymer residues from the surface of the conductive plug through a chemical oxidation reaction.
[0042] The following combination Figures 5-12 This invention specifically describes a fabrication method for improving the yield of an image sensor in an embodiment (used in the first metal layer M1 process). It should be noted that the fabrication method described in this invention is not only applicable to the first metal layer (M1) process, but also to the second metal layer (M2), third metal layer (M3), and higher metal interconnect processes, addressing the more severe polymer residue problems caused by thicker photoresist and longer etching times. For subsequent metal interconnect processes, the cleaning step in the fabrication method of this invention also has the effect of thoroughly removing contaminants from the surface of the exposed conductive plugs at the bottom of the trench.
[0043] Example Step S1, providing a semiconductor structure, specifically including: like Figure 5 As shown, a semiconductor substrate 10 is provided, a first dielectric layer 20 is formed on the semiconductor substrate 10, and a conductive plug 21 is formed in the first dielectric layer 20. Figure 5 A partial cross-section of a semiconductor structure including two conductive plugs 21 is shown. Devices, such as photodiodes and transistors (not shown), are fabricated on the semiconductor substrate 10. The conductive plugs 21 are formed by etching contact holes in the first dielectric layer 20 and then filling the contact holes with a conductive material; the conductive material includes at least one of Cu, W, Mo, or Co. The first dielectric layer 20 is an in-line dielectric layer (ILD HARP) and may be an oxide layer formed by a HARP process. In this embodiment, the first dielectric layer 20 is used to fill the gap between the transistor gates; in other embodiments (e.g., for M2 and M3 processes), the first dielectric layer 20 is used to achieve insulation between the lower and upper metal lines.
[0044] like Figure 6 As shown, a barrier layer 30 and a second dielectric layer 40 are formed on the first dielectric layer 20. The barrier layer 30 can be made of nitrogen-doped silicon carbide (NDC) to block the diffusion of metal elements. The second dielectric layer 40 can be made of a material with a low dielectric constant (Low K) value, such as SiCOH, F-SiO2, ULK, etc., to reduce the parasitic capacitance between metal lines.
[0045] like Figures 7-8As shown, after a hard mask layer 50 and a patterned photoresist layer 60 are sequentially formed on the surface of the second dielectric layer 40, the pattern of the photoresist layer 60 is transferred to the hard mask layer 50 through an etching process, and the remaining photoresist layer 60 is removed. In this embodiment, the hard mask layer 50 is made of titanium nitride. During the etching and pattern transfer process, the etching gas (usually containing fluorocarbon gases, such as C4F6 and C4F8) reacts not only with the hard mask layer 50 but also with the organic matter in the photoresist layer 60, resulting in complex chemical reactions. As analyzed above, this process generates non-volatile etching byproducts, mainly polymers containing carbon, fluorine, and oxygen elements. Some of these byproducts are discharged with the process gas, but some are deposited and adhered to the top surface and sidewalls of the patterned hard mask layer 50 and the exposed top surface of the second dielectric layer 40.
[0046] Subsequently, as Figure 9 As shown, using a patterned hard mask layer 50 as a mask, the second dielectric layer 40 and the barrier layer 30 beneath it are etched to form a trench 70 that ultimately exposes the conductive plug 21. During this etching process, etching byproducts (polymer residues 901) previously attached to the vicinity of the top opening or sidewalls of the trench may be partially loosened, peeled off, and redeposited due to continuous plasma bombardment or chemical action, eventually settling and adhering to the bottom of the etched trench, i.e., the exposed surface of the conductive plug 21. These polymer residues 901 constitute an interfacial contaminant barrier that must be removed before subsequent metal deposition. If not removed, they will severely affect the electrical contact performance between the subsequently deposited metal layer and the conductive plug 21.
[0047] Step S2: Perform a cleaning step on the surface of the conductive plug.
[0048] Polymers are difficult to react with reducing gases (e.g., H2), making it difficult to effectively remove contaminants from the surface of the conductive plug 21 using a single reduction treatment. Physical bombardment methods, on the other hand, introduce new problems with contaminating the wafer and the equipment. Therefore, to effectively remove polymer residues generated by the previous etching process, this invention proposes a cleaning step based on a chemical reaction mechanism, including etching and / or baking heat treatment, to convert polymer residues into volatile gaseous products without generating solid debris.
[0049] As an example, the polymer residue can be removed by etching. Specifically, this is achieved by introducing oxygen-containing gas into a process chamber and exciting plasma, utilizing the generated oxygen-active particles (e.g., O₂). +O*) reacts with carbon, fluorine, and oxygen components in the polymer to generate volatile substances such as CO, CO2, and fluorides, thereby achieving selective chemical removal. The oxygen-containing gas includes at least one of O2, CO, CO2, and SO2; in this embodiment, O2 is used. The etching process parameters include at least: a gas flow rate of 500 sccm to 700 sccm; a process temperature of 50°C to 70°C; and a chamber pressure of 100 mTorr to 200 mTorr. In some embodiments, the etching time is controlled to be 20 to 40 seconds to ensure sufficient chemical reaction time so that the oxygen-active particles can fully react with the polymer residue 901 attached to the surface of the conductive plug 21. If the processing time is too short, the cleaning may not be thorough. In particular, for processes such as M2 / M3, more serious polymer residues may form. The residual polymers will still act as a barrier to hinder the subsequent treatment of oxides, causing the cleaning process to fail. If the processing time is too long, the surface of the conductive plug 21 may also be slightly etched by oxygen active particles, resulting in the loss of the key dimensions and morphology of the conductive plug 21.
[0050] As another example, a baking heat treatment can be used to remove the polymer residue. Specifically, by introducing a heat treatment gas and heating the surface of the semiconductor structure, the carbon-carbon bonds and carbon-oxygen bonds in the polymer are oxidized into gaseous products such as CO and CO2 under high temperature and oxygen conditions, while the fluorine element in the polymer is removed or volatilized in the form of small molecule fluorocarbons (e.g., CF4) during this process. The heat treatment gas contains O2 and a carrier gas; the carrier gas contains at least one of nitrogen or an inert gas (e.g., argon) to stabilize the chamber pressure of the process chamber. The process parameters of the baking heat treatment include at least: an O2 gas flow rate of 10000 sccm to 12000 sccm; a carrier gas flow rate of 1000 sccm to 1200 sccm; a process temperature of 230°C to 320°C; and a chamber pressure of 800 mTorr to 1000 mTorr. In some embodiments, the baking heat treatment time is controlled to be 30s to 50s to provide sufficient time for thermal oxidation reaction, thoroughly remove the polymer, and prevent excessive oxidation of the surface of the conductive plug 21.
[0051] As another example, in applications with significant polymer residue or complex structures (e.g., in M2 and M3 processes), etching and baking heat treatment can be combined as cleaning steps to achieve a more thorough cleaning effect. For instance, etching can be performed first to quickly remove most of the surface polymer using its high etching rate, followed by baking heat treatment, which utilizes its gentler and more uniform thermal oxidation properties to remove any trace polymer residues that may remain after etching.
[0052] The etching process, the baking heat treatment, and the formation of the trench 70 can be performed in the same process chamber to achieve in-situ cleaning. By continuously completing the etching process and cleaning steps within the same process chamber, device transport and atmospheric exposure time are avoided, thereby improving the cleaning effect of the cleaning steps.
[0053] In some embodiments, after performing the etching process and / or baking heat treatment, and before depositing the metal layer, the following is further included: Step S3, perform a cleaning process, the cleaning process includes a reduction treatment, the reduction treatment includes introducing a reducing gas to remove oxide impurities from the surface of the conductive plug through a chemical reduction reaction.
[0054] After the etching and / or baking heat treatment in step S2, the polymer residue 901 on the surface of the conductive plug 21 can be effectively removed. However, under the polymer and after the polymer is removed, oxides (not shown in the figure) that were originally coated or covered by the polymer may still exist on the surface of the conductive plug 21, or newly generated oxides (not shown in the figure) due to exposure to a trace oxygen environment during the cleaning step. Step S3 addresses these oxide impurities by introducing H2 into the chamber containing the conductive plug 21, causing the H2 to react with the oxides on the surface of the conductive plug 21 to generate volatile water vapor, thus completely removing them. The process parameters for the reduction treatment include at least: an H2 flow rate of 150 sccm to 300 sccm, an introduction time of 20 s to 40 s, and a treatment temperature of 20°C to 30°C.
[0055] Through the orderly combination of the above steps S2 and S3, the contaminants (polymers and oxides) on the surface of the conductive plug 21 are thoroughly removed, thereby providing a clean interface for the subsequent deposition of the metal layer.
[0056] In some embodiments, the cleaning process further includes a degassing process, which removes moisture (water vapor) from the surface of the device by heating.
[0057] In some embodiments, after performing the reduction process and before depositing the metal layer, the following steps are further included: Step S4: Deposit a barrier layer and a seed layer on the sidewall of the trench 70.
[0058] like Figure 10 As shown, a barrier layer 80 is deposited on the sidewall of the trench 70 to prevent the diffusion and migration of the subsequently filled conductive metal elements, thus avoiding leakage current. In this embodiment, the barrier layer 80 is made of carbon nitride. After forming the barrier layer 80, a seed layer (e.g., tantalum metal, not shown in the figure) is conformally deposited into the trench 70 to facilitate defect-free filling of the subsequent conductive metal material.
[0059] Then, as Figures 11-12 As shown, a conductive metal material is deposited inside the trench 70 to fill the trench 70 and form a metal layer 90. The top plane of the semiconductor structure is treated by chemical mechanical polishing or dry etching to remove the residual metal layer 90 and barrier layer 80 on the top plane of the trench 70 until the second dielectric layer 40 is exposed, so that the top plane of the metal layer 90 filled in the trench 70 is flush with the top plane of the second dielectric layer 40.
[0060] In summary, this invention thoroughly removes stubborn polymer residues from the surface of conductive plugs through etching and / or baking heat treatment, exposing the covered / encapsulated oxides. Subsequently, a reduction process is used to precisely remove the oxides, forming a composite cleaning strategy of "removing polymers first, then eliminating oxides." This approach achieves gentle and thorough interface cleaning without damaging the device or chamber, thereby reducing contact resistance and significantly improving the electrical performance and product yield of image sensors.
[0061] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0062] In the description of this invention, it should be understood that the terms "center," "height," "thickness," "upper," "lower," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.
[0063] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0064] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0065] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.
Claims
1. A method for improving the yield of an image sensor, characterized in that, Includes the following steps: A semiconductor structure is provided, the semiconductor structure including a substrate and conductive plugs and trenches formed thereon, wherein the bottom of the trench exposes the conductive plugs, and the trench is used to deposit a metal layer; Prior to depositing the metal layer, a cleaning step is performed on the surface of the conductive plug, the cleaning step comprising etching and / or baking heat treatment: The etching process includes introducing oxygen-containing gas and using plasma etching to remove polymer residues from the surface of the conductive plug; The baking heat treatment includes introducing heat treatment gas and baking the surface of the semiconductor structure to remove polymer residues from the surface of the conductive plug through a chemical oxidation reaction.
2. The preparation method according to claim 1, characterized in that, In the etching process, the oxygen-containing gas includes at least one of O2, CO, CO2, and SO2.
3. The preparation method according to claim 1, characterized in that, The etching process parameters include at least the following: the gas flow rate of the oxygen-containing gas is 500 sccm to 700 sccm; the process temperature is 50℃ to 70℃; and the chamber pressure is 100 mTorr to 200 mTorr.
4. The preparation method according to claim 1, characterized in that, The etching process takes 20s to 40s.
5. The preparation method according to claim 1, characterized in that, In the baking heat treatment, the heat treatment gas includes O2 and a carrier gas, and the carrier gas includes at least one of nitrogen or an inert gas.
6. The preparation method according to claim 5, wherein the process parameters of the baking heat treatment include at least: the gas flow rate of O2 is 10000 sccm~12000 sccm; the gas flow rate of the carrier gas is 1000 sccm~1200 sccm; the process temperature is 230℃~320℃; and the chamber pressure is 800 mTorr~1000 mTorr.
7. The preparation method according to claim 1, characterized in that, The baking heat treatment process takes 30s to 50s.
8. The preparation method according to claim 1, characterized in that, When the cleaning step includes the etching process and the baking heat treatment, the etching process, the baking heat treatment, and the formation of the trench are performed in the same process chamber.
9. The preparation method according to claim 1, characterized in that, A semiconductor structure is provided, specifically including: A semiconductor substrate is provided, a first dielectric layer is formed on the semiconductor substrate, and a conductive plug is formed within the first dielectric layer; A barrier layer and a second dielectric layer are formed on the first dielectric layer, and the second dielectric layer and the barrier layer are etched to form the trench, exposing the surface of the conductive plug.
10. The preparation method according to claim 1, characterized in that, After the etching process and / or baking heat treatment, and before the deposited metal layer, a cleaning process is further included, the cleaning process comprising: Reduction treatment: A reducing gas is introduced to remove oxide impurities from the surface of the conductive plug through a chemical reduction reaction.
11. The preparation method according to claim 10, characterized in that, After performing the reduction process and before depositing the metal layer, the process further includes: A barrier layer and a seed layer are deposited on the sidewall of the trench.
12. The preparation method according to claim 10, characterized in that, The reduction process includes: introducing H2 into the chamber where the conductive plug is located, so that H2 reacts with the oxide on the surface of the conductive plug, the H2 flow rate is 150 sccm to 300 sccm, the introduction time is 20 s to 40 s, and the processing temperature is 20 ℃ to 30 ℃.
13. An image sensor, characterized in that, It is manufactured using the method for improving the yield of image sensors as described in any one of claims 1 to 12.