Method and system for monitoring the extent of fluoride attack
By forming simulated patterns of different thicknesses and morphologies on the monitored wafer, optical measurement technology is used to evaluate fluorine attack in the WCVD process. This solves the problems of lag and misjudgment in existing monitoring methods and achieves early, highly sensitive quantitative evaluation and real-time monitoring.
Patent Information
- Application Number
- CN202610412467.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-31
- Publication Date
- 2026-07-07
AI Technical Summary
Existing methods for monitoring fluorine attack in WCVD processes suffer from problems such as lag and destructiveness, lack of specificity, low sensitivity, inability to quantify systematically, and susceptibility to misjudgment.
By forming simulated patterns of different morphologies and/or thicknesses on the monitored wafer, a rapid, non-destructive quantitative assessment is performed using optical measurement techniques. Initial and surface reflectance are obtained using reflectance measurement techniques, and the reflectance change rate ΔR% is calculated to assess the degree of fluorine attack.
It enables early, highly sensitive detection of fluorine attacks, provides real-time, non-destructive quantitative assessment, reduces monitoring costs, and improves production efficiency.
Smart Images
Figure CN122349332A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a method and system for monitoring the degree of fluorine attack. Background Technology
[0002] In advanced semiconductor device manufacturing, tungsten (W) chemical vapor deposition (CVD) is a key process for forming conductive plugs and interconnects. This process typically uses tungsten hexafluoride (WF6) and silane (SiH4) as precursors. In the process flow, a reducing gas, SiH4, is first introduced to form a thin tungsten nucleation layer (NUC) on the substrate surface, followed by the rapid deposition of the main tungsten layer using WF6. Currently, the industry primarily relies on the following methods to monitor and assess potential fluorine (F) attacks in WCVD processes:
[0003] 1. Electrical Testing Method: After the entire device or test structure is manufactured, damage caused by the process is indirectly inferred by measuring contact resistance, interconnect resistance, or the electrical characteristics of diodes / transistors. If electrical anomalies are found, the process may be traced back to the WCVD step, such as... Figure 1 The graph shown represents an electrical testing method. The horizontal axis represents the specific wafer number, the vertical axis represents the source-drain leakage current value, and the red horizontal line represents the upper limit of the source-drain leakage current value specification.
[0004] 2. Offline destructive physical analysis: Periodically extract production wafers or use monitor wafers, and perform cross-sectional observation of critical device structures (such as the bottom of contact holes) using scanning electron microscopy (SEM) or transmission electron microscopy (TEM) after the process. Figure 2 The electron microscope images shown directly examine whether there is physical damage such as corrosion or voids in the silicon substrate or underlying material caused by F attack.
[0005] 3. GPN Vapor Nucleation System: By designing the timing sequence of SiH4 and WF6, the presence of GPN vapor nucleation reactions is observed visually between the shower head (also called a gas distribution plate or gas equalization plate) and the heater. This monitors whether WF6 will prematurely reach the wafer surface, leading to ferrochemical attack. ALTUS (Atomic Layer Deposition) WCVD is completed in two steps:
[0006] 1) The reaction between SiH4 and WF6, i.e., nucleation:
[0007] 3SiH4 + 2WF6 → 2W + 3SiF4 + 6H2
[0008] 2SiH4 + WF6 → W + 3SiF3 + 3H2
[0009] 2) The reaction between H2 and WF6, i.e., Bulk Dep (rapid film formation):
[0010] 3H2+WF6→W+6HF
[0011] Among the conventional monitoring methods mentioned above, electrical testing and offline physical analysis are all post-event monitoring methods, which are characterized by lag and destructiveness; offline destructive physical analysis is not targeted, has low sensitivity, cannot be systematically quantified, is highly subjective, and is prone to misjudgment.
[0012] It should be noted that the information disclosed in the background section of this invention is intended only to enhance the understanding of the general background of this invention, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention
[0013] The purpose of this invention is to provide a method and system for monitoring the degree of fluorine attack, so as to solve the problems of conventional monitoring methods, such as lag and destructiveness, lack of specificity, low sensitivity and inability to quantify systematically, high subjectivity and easy misjudgment.
[0014] To address the aforementioned technical problems, this invention provides a method for monitoring the degree of fluorine attack, comprising:
[0015] Provide at least one monitoring wafer, on which several simulated patterns are formed to simulate the film layer distribution on the surface of the product wafer used to fabricate the device, wherein the thickness and / or morphology of the different simulated patterns are different;
[0016] Initial values for measuring the surface roughness of each of the simulated patterns are obtained using optical measurement techniques;
[0017] The tungsten deposition process to be monitored is performed using a fluorine-containing gas: nucleation layers of various thicknesses are formed on each of the simulated patterns, and a film deposition process is performed to prepare a tungsten layer on the monitored wafer;
[0018] Surface values are obtained using optical measurement techniques to measure the surface roughness of the tungsten layer on various simulated patterns, and the degree of fluorine attack is assessed based on the initial values and the surface values for each simulated pattern.
[0019] Preferably, forming the simulated pattern on the substrate surface of the monitoring wafer includes forming a barrier layer of several thicknesses on the substrate surface.
[0020] Preferably, the material of the barrier layer includes TiN, Ti, TaN, and Co.
[0021] Preferably, the barrier layer has a variety of thicknesses within the range of 2nm to 20nm.
[0022] Preferably, the nucleation layer has a variety of thicknesses within the range of 5nm to 50nm.
[0023] Preferably, forming several simulated patterns on the substrate surface of the monitoring wafer includes forming several simulated patterns with different aspect ratios on the substrate surface.
[0024] Preferably, the initial reflectance of each of the simulated patterns is obtained using reflectance measurement technology, and the surface reflectance of the tungsten layer on each of the simulated patterns is obtained using reflectance measurement technology, and the degree of fluorine attack is evaluated based on the initial reflectance and the surface reflectance of each of the simulated patterns.
[0025] Preferably, assessing the degree of fluoride attack based on the initial reflectance and the surface reflectance of each of the simulated patterns includes: denoting the initial reflectance on the current simulated pattern as R_before and the surface reflectance as R_after, and calculating the reflectance change rate ΔR% according to the following formula:
[0026] ΔR% = (R_after - R_before) / R_before × 100%
[0027] The reflectance change rate corresponding to different simulated patterns was analyzed, and the absolute value of the reflectance change rate was positively correlated with the degree of fluorine attack on the substrate.
[0028] Preferably, after obtaining the reflectivity change rate of different types of simulated patterns, the maximum value of the absolute value of the reflectivity change rate is obtained, and when the maximum value of the absolute value of the reflectivity change rate exceeds a preset threshold, an alarm is immediately triggered and the tungsten deposition process parameters are checked or adjusted.
[0029] Based on the same technical concept, the present invention also provides a monitoring system for the degree of fluorine attack, which uses the fluorine attack degree monitoring method described above for monitoring.
[0030] The present invention provides a method for monitoring the degree of fluorine attack, comprising: providing at least one monitoring wafer, forming a plurality of simulated patterns on a substrate of the monitoring wafer to simulate the film layer distribution on the surface of a product wafer used for fabricating devices, wherein the thickness and / or morphology of the different simulated patterns are different; using optical measurement technology to obtain initial values for measuring the surface roughness of each of the simulated patterns; performing a tungsten deposition process to be monitored using a fluorine-containing gas: forming nucleation layers of various thicknesses on each of the simulated patterns, performing a film deposition process to prepare a tungsten layer on the monitoring wafer; using optical measurement technology to obtain surface values for measuring the surface roughness of the tungsten layer on each of the simulated patterns, and evaluating the degree of fluorine attack based on the initial values and the surface values of each of the simulated patterns. By providing a monitoring wafer with a special structure, namely, forming simulated patterns of different morphologies and / or thicknesses on the monitoring wafer, the actual situation of the film layer distribution on the surface of a product wafer is simulated, such as the distribution of film layer thickness and pattern in different regions, and optical measurement technology is used to achieve rapid, non-destructive quantitative evaluation.
[0031] The fluorine attack monitoring system and the fluorine attack monitoring method provided by this invention belong to the same inventive concept. Therefore, the fluorine attack monitoring system provided by this invention has at least all the advantages of the fluorine attack monitoring method provided by this invention, which will not be repeated here. Attached Figure Description
[0032] Those skilled in the art will understand that the accompanying drawings are provided to better understand the invention and do not constitute any limitation on the scope of the invention. Wherein:
[0033] Figure 1 This is a chart of existing techniques for electrical testing of devices that have undergone WCVD.
[0034] Figure 2 These are electron microscope images of devices that have undergone WCVD using existing technology;
[0035] Figure 3 This is a flowchart of an embodiment of the present invention;
[0036] Figure 4 This is a schematic diagram of the structure for preparing the barrier layer according to an embodiment of the present invention;
[0037] Figure 5 This is a schematic diagram of a structure for measuring initial reflectivity according to an embodiment of the present invention;
[0038] Figure 6 This is a schematic diagram of the structure of the nucleation layer prepared according to an embodiment of the present invention;
[0039] Figure 7 This is a schematic diagram of the surface structure with and without fluorine attack according to an embodiment of the present invention;
[0040] Figure 8 This is a schematic diagram of a structure for measuring the first surface reflectivity of a tungsten layer under a barrier layer and a nucleation layer of a certain thickness combination, according to an embodiment of the present invention.
[0041] Figure 9 This is a schematic diagram of a structure for measuring the second surface reflectivity of a tungsten layer under a barrier layer and a nucleation layer with a different thickness combination, according to an embodiment of the present invention.
[0042] Figure 10 This is a data table showing the core indicators of the degree of fluorine attack in the barrier layer and nucleation layer under different thickness combinations of the present invention.
[0043] Figure 11 This is a chart that represents the core indicator of the degree of fluorine attack in this invention.
[0044] In the attached image:
[0045] 100, Monitoring wafer; 10, Substrate; 20, Oxide layer; 30, Barrier layer; 40, Nucleation layer; 50, Tungsten layer. Detailed Implementation
[0046] To make the objectives, advantages, and features of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to facilitate and clarify the explanation of the embodiments of this invention. Furthermore, the structures shown in the drawings are often part of the actual structures. In particular, different figures may emphasize different aspects and may sometimes use different scales.
[0047] As used in this invention, the singular forms “a,” “an,” and “the” include plural objects; the term “or” is generally used to mean “and / or”; the term “a number” is generally used to mean “at least one”; the term “at least two” is generally used to mean “two or more”; furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," and "third" may explicitly or implicitly include one or at least two of those features. The term "proximal" typically refers to the end closer to the operator, and the term "distal" typically refers to the end closer to the patient. "One end" and "the other end," as well as "proximal" and "distal," generally refer to two corresponding parts, including not only endpoints. The terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can be fixed connections, detachable connections, or integral connections; they can be mechanical connections or electrical connections; they can be direct connections or indirect connections through an intermediate medium; they can be internal connections between two elements or interactions between two elements. Furthermore, as used in this invention, the placement of one element on another element generally only indicates a connection, coupling, cooperation, or transmission relationship between the two elements, and the connection, coupling, cooperation, or transmission between the two elements can be direct or indirect through an intermediate element. It should not be construed as indicating or implying a spatial positional relationship between the two elements, i.e., one element can be located arbitrarily inside, outside, above, below, or to one side of another element, unless otherwise explicitly stated. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0048] Studies have found that commonly used electrical testing methods, offline destructive physical analysis, and GPN vapor nucleation systems have the following drawbacks in addressing potential F (fluorine) attack in WCVD processes:
[0049] 1. Lag and Destructive Nature: Both electrical testing and offline physical analysis are reactive monitoring methods, unable to provide real-time feedback during the process. By the time a problem is detected, a batch of products has often already been lost. Furthermore, physical analysis is destructive, and samples cannot be returned to the production line.
[0050] 2. Lack of specificity and low sensitivity: Reflectance measurements are performed using standard blank films or films with fixed thin films, whose film structures are not optimized for the sensitive characteristics of F attacks. The subtle changes in bottom roughness caused in the early stages of an F attack are unlikely to produce significant and distinguishable signals on the macroscopic, unoptimized surface reflectance, resulting in insufficient monitoring sensitivity and inability to provide early or moderate F attacks.
[0051] 3. Inability to quantify systematically: Existing methods are difficult to systematically establish a quantitative relationship between process parameters (such as WF6 / SiH4 ratio, flow rate, timing) and the severity of F attacks, which is not conducive to the rapid optimization and precise control of the process window.
[0052] 4. High degree of subjectivity and easy to misjudge: The GPN gas phase nucleation instrument requires visual inspection by human eyes, which poses a risk of misjudgment.
[0053] Based on this, the core idea of the present invention is to provide a monitoring wafer with a special structure, that is, to form simulated patterns of different morphologies and / or thicknesses on the monitoring wafer to simulate the actual situation of the film layer distribution on the surface of the product wafer, such as the distribution of film layer thickness and pattern in different regions, and to achieve rapid and non-destructive quantitative evaluation by using optical measurement technology.
[0054] For details, please refer to Figures 3-11 This is a schematic diagram of an embodiment of the present invention. Figure 3 As shown, a method for monitoring the degree of fluoride attack includes:
[0055] Step 1: Provide at least one monitoring wafer 100, and form several simulated patterns on the substrate 10 of the monitoring wafer 100 to simulate the film layer distribution on the surface of the product wafer used to fabricate the device. The thickness and / or morphology of the different simulated patterns are different.
[0056] First, a dedicated monitoring wafer 100 is prepared, and a simulated pattern is prepared on the substrate 10. The simulated pattern can be a film layer with the same thickness as the surface of the product wafer. By setting multiple thicknesses or combinations of thicknesses, the film deposition state of different areas on the surface of the product wafer can be simulated. Alternatively, it can be a pattern structure with the same thickness as the surface of the product wafer. By setting the aspect ratio of the pattern, the shape of the pattern can be changed, thereby simulating the state of trenches or patterns in different areas on the surface of the product wafer.
[0057] like Figure 4 As shown, forming a simulated pattern on the surface of the substrate 10 of the monitoring wafer 100 includes forming a barrier layer 30 of several thicknesses on the surface of the substrate 10. It is understood that an oxide layer 20, made of silicon oxide, is also distributed between the surface of the substrate 10 and the barrier layer 30. The material of the substrate 10 may include semiconductor materials, insulating materials, conductive materials, or any combination thereof; and the substrate 10 may be a single-layer structure or a multilayer structure. For example, the substrate 10 may be a semiconductor material such as Si, SiGe, SiGeC, SiC, GaAs, InAs, InP, and other III / V or II / VI compound semiconductors. The substrate 10 may also be a layered substrate such as Si / SiGe, Si / SiC, silicon-on-insulator (SOI), or silicon-germanium-on-insulator.
[0058] In one embodiment, a barrier layer 30 is prepared by physical vapor deposition (PVD), preferably a titanium nitride (TiN) film as the diffusion barrier layer 30. Crucially, instead of using a single thickness, we prepare a series or a matrix of monitoring wafers 100 with specific thickness combinations. Specifically, different regions are designed on the same monitoring wafer 100, or the thicknesses of the two key layers, the barrier layer 30 and the nucleation layer 40, are systematically varied across multiple monitoring wafers 100. Here, only the details of the barrier layer 30 are described; the details of the nucleation layer 40 are explained in step three.
[0059] like Figure 4 As shown, the thickness of the bottom barrier layer 30, i.e., the TiN layer, is denoted as d_TiN. The barrier layer 30 can be selected with various thicknesses ranging from 2nm to 20nm. The materials of the barrier layer 30 include TiN, Ti, TaN, and Co. Understandably, the material of the barrier layer 30 can be replaced with other bottom materials that may react with fluorine or be affected by fluorine diffusion in the WCVD process, such as Ti, TaN, and Co, to study the resistance of different barrier layer materials to fluorine attack.
[0060] In another implementation, in addition to systematically changing the thickness, patterned structures simulating different aspect ratios can be designed on the monitoring wafer 100 to directly measure the reflectivity or other optical properties after tungsten deposition within the pattern, thus more directly relating to the actual structure of the product.
[0061] Specifically, forming several simulated patterns on the substrate surface of the monitoring wafer 100 includes forming several simulated patterns with different aspect ratios on the substrate 10 surface. It can be understood that these simulated patterns can be trenches, i.e., trenches with different aspect ratios are first etched onto the substrate 10.
[0062] Step two: Use optical measurement techniques to obtain initial values for measuring the surface roughness of each of the simulated patterns.
[0063] For example, the optical measurement technique is a reflectance measurement technique, corresponding to obtaining initial reflectance and surface reflectance values, respectively. Specifically, the reflectance measurement technique is used to obtain the initial reflectance of each of the simulated patterns, and the reflectance of the tungsten layer 50 on each of the simulated patterns is also used to obtain the surface reflectance. The degree of fluorine attack is assessed based on the initial reflectance and the surface reflectance of each of the simulated patterns. For example... Figure 5 As shown, after the barrier layer 30 is formed, the initial reflectivity of the surface of each barrier layer 30 is measured.
[0064] In addition, reflectivity measurement technology can be replaced by other optical measurement techniques that are sensitive to surface / interface roughness, such as elliptic polarization or light scattering, to achieve monitoring by establishing a correlation model between the intensity of scattered light and the degree of fluorine attack.
[0065] Step 3: Perform the monitored tungsten deposition process using a fluorine-containing gas: On each of the simulated patterns, nucleation layers 40 of varying thicknesses are formed, such as... Figure 6 As shown, a film deposition process is performed to prepare a tungsten layer 50 on the monitoring wafer 100. Specifically, the nucleation layer 40 has various thicknesses ranging from 5 nm to 50 nm.
[0066] Multiple thicknesses of the bottom titanium nitride (d_TiN) are selected within a range of, for example, 2 nm to 20 nm, and multiple thicknesses of the tungsten nucleation layer 40 (d_NUC) are selected within a range of, for example, 5 nm to 50 nm. By using various thickness combinations of titanium nitride and nucleation layer 40, the actual conditions of the bottom materials of structures with different aspect ratios in real products are simulated. Even better, multiple combinations of each thickness can be set to avoid process errors.
[0067] After the nucleation layer 40 is prepared, the WCVD process is then performed: the prepared dedicated monitoring wafer 100 is fed into the WCVD reaction chamber together with the product wafer (or under simulated conditions). The tungsten deposition process to be monitored is then performed, which may be at risk of fluorine attack due to improper formulation settings (such as excessive WF6).
[0068] Step four: Use optical measurement techniques to obtain surface values that measure the surface roughness of the tungsten layer 50 on various simulated patterns, and assess the degree of fluorine attack based on the initial values and surface values for each simulated pattern. (See reference...) Figure 7 The schematic diagram of the surface structure with and without fluorine attack shows that...
[0069] The surface reflectance of the tungsten layer 50 on various simulated patterns is obtained using reflectance measurement techniques. The degree of fluorine attack is assessed based on the initial reflectance and the surface reflectance of each simulated pattern. (See reference...) Figure 8 As shown, the first surface reflectance R1_after and the second surface reflectance R2_after were measured for two combinations of film thicknesses.
[0070] Post-process reflectivity measurement includes: after the process is completed, using a film thickness measurement device (such as a reflectance spectrometer) to measure the surface reflectivity (R_after) of specific thickness combinations on the monitoring wafer 100. Simultaneously, the initial reflectivity (R_before) of the same region before the process is measured is used as a baseline. Next, data analysis and fluorine attack quantification are performed: assessing the fluorine attack level based on the initial reflectivity and surface reflectivity on each simulated pattern includes: designating the initial reflectivity on the current simulated pattern as R_before, and the surface reflectivity as R_after, and calculating the reflectivity change rate ΔR% according to the following formula:
[0071] ΔR% = (R_after - R_before) / R_before × 100%
[0072] The reflectance change rate corresponding to different simulated patterns was analyzed, and the absolute value of the reflectance change rate was positively correlated with the degree of fluorine attack on the substrate.
[0073] The rate of change in reflectance for each region before and after the process is calculated using the above formula to measure the degree of fluorine attack. It is understandable that fluorine attack causes roughening of the bottom interface of the WCVD film, and may even form porous or discontinuous structures. This increase in bottom roughness significantly scatters incident light, leading to a decrease in surface reflectance. (See reference...) Figure 7 The diagram illustrates this. Therefore, the larger the negative value of ΔR% (i.e., the greater the decrease in reflectivity), the more severe the F attack in that region.
[0074] Furthermore, the ΔR% corresponding to different (d_TiN, d_NUC) combinations can be analyzed. The film layer combination corresponding to the region most sensitive to fluorine attack (i.e., the region with the largest negative ΔR% and the highest absolute value) is the "weakest point" most susceptible to fluorine attack under this specific WCVD process condition. The absolute value of ΔR% in this region can be used as the core indicator for quantifying the degree of fluorine attack (FDI, F-attack Damage Index).
[0075] Specifically, after obtaining the reflectivity change rate of different simulated patterns, the maximum value of the absolute value of the reflectivity change rate is obtained, and when the maximum value of the absolute value of the reflectivity change rate exceeds a preset threshold, an alarm is immediately triggered and the tungsten deposition process parameters are checked or adjusted.
[0076] As an example, a monitoring and feedback mechanism based on FDI can be established: In mass production, the combination of (d_TiN, d_NUC) most sensitive to fluorine attack can be consistently used as the standard monitoring structure. This monitored wafer is periodically tested to measure its FDI value. By setting a control upper limit for FDI (e.g., -5%), real-time early warning can be achieved: when FDI exceeds the threshold, an alarm is immediately triggered, and WCVD process parameters are checked or adjusted, such as reducing WF6 flow rate and optimizing SiH4 and WF6 timing.
[0077] Based on the above process, experimental data for several combinations of TiN and nucleation layer 40 thickness are presented, such as... Figure 10 The table shown, and with Figure 10 The data corresponds to Figure 11 Among them, in Figure 10 The first column is the process stage, including TiN deposition (TiN Dep), tungsten nucleation (W_NUC), tungsten gas nucleation (W_GPN), and measurement results (Result); Figure 10 The second column presents various process conditions, including: 120 Å, 85 Å, and 50 Å TiN formed using SIP (Self-Ionizing Plasma); 70 Å, 50 Å, and 50 Å TiN formed using MOCVD (Metal Organic Chemical Vapor Deposition) without plasma treatment; nucleation layer (NUC) thicknesses of 200 Å and 400 Å; and conventional GPN conditions and simulated GPN degradation conditions (GPN+0.7s), as well as the reflectance variation rate (FDI). Figure 10 In the diagram, 1-18 represent monitoring areas on a wafer or individual monitoring wafers, and the checkmarks indicate that the corresponding process has been performed. Figure 10 Data and Figure 11 The chart shows that:
[0078] From the perspective of d_TiN, the increased thickness of TiN leads to higher sensitivity to FDI. TiN deposited by MOCVD is most sensitive to fluorine attack (F attack) without plasma treatment. From the perspective of d_NUC, appropriately reducing the thickness of W_NUC can increase the sensitivity of this technical solution to FDI. Under NUC 200Å conditions, the average FDI parameter is 1.04% lower than that under NUC 400Å conditions. From the perspective of fluorine attack (F attack) deterioration simulation, the average FDI data using this technical solution is 5.02% lower than that under BSL conditions. By combining product characteristics and selecting appropriate d_TiN and d_NUC, a statistical process control chart (SPC chart) can be established to monitor fluorine attack (F attack).
[0079] Based on the same technical concept, the present invention also provides a monitoring system for F attack level, which uses the F attack level monitoring method described above to monitor product wafers.
[0080] In one embodiment, a monitoring wafer, independent of the product wafer, is provided, and a WCVD process is performed on the monitoring wafer using a combination of bottom diffusion barrier layers (such as TiN) and / or tungsten nucleation layers (NUC) of varying thicknesses. The optical reflectivity of each test area on the monitoring wafer before and after the process is measured. The degree of fluorine attack is determined based on the change in reflectivity. The degree of fluorine attack is quantified by the rate of change in reflectivity (ΔR%), and the film layer combination corresponding to the test area with the largest negative ΔR% value is selected as the characterization of fluorine attack sensitivity under this WCVD process condition.
[0081] The method and system for monitoring the degree of fluorine attack provided by this invention proposes to combine and adjust the thickness of the bottom TiN (or similar barrier layer) and tungsten nucleation layer (NUC) on the monitoring wafer to find and define the material thickness combination most sensitive to fluorine attack in the WCVD process; establish a quantitative correspondence between the degree of fluorine attack (FDI) and the rate of change (ΔR%) of optical reflectivity in a specific film layer combination region, and use the decrease in reflectivity as a direct and quantifiable criterion for the occurrence of fluorine attack. The method and system for monitoring the degree of fluorine attack provided by this invention also have the following advantages:
[0082] 1. High sensitivity and early warning: By designing a TiN / NUC film combination that is sensitive to F attacks, the microscopic bottom interface damage is amplified into a macroscopic optical signal change that can be accurately measured, thus achieving high-sensitivity detection of early and slight F attacks.
[0083] 2. Real-time and non-destructive: Reflectivity measurement is fast (on the order of seconds) and can be performed immediately after the process, enabling near real-time process monitoring. Monitoring the wafer itself is not damaged, and data acquisition costs are low.
[0084] 3. High cost-effectiveness: It avoids frequent and expensive offline electron microscopy analysis, significantly reducing process development and monitoring costs and improving production efficiency.
[0085] It should be noted that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention shall still fall within the scope of protection of the present invention.
Claims
1. A method for monitoring the degree of fluoride attack, characterized in that, include: Provide at least one monitoring wafer, on which a plurality of simulated patterns are formed to simulate the film layer distribution on the surface of the product wafer used to fabricate the device, wherein the thickness and / or morphology of the different simulated patterns are different; Initial values for measuring the surface roughness of each of the simulated patterns are obtained using optical measurement techniques; The tungsten deposition process to be monitored is performed using a fluorine-containing gas: nucleation layers of various thicknesses are formed on each of the simulated patterns, and a film deposition process is performed to prepare a tungsten layer on the monitored wafer; Surface values are obtained using optical measurement techniques to measure the surface roughness of the tungsten layer on various simulated patterns, and the degree of fluorine attack is assessed based on the initial values and the surface values for each simulated pattern.
2. The method for monitoring the degree of fluoride attack according to claim 1, characterized in that, Forming a simulated pattern on the substrate surface of the monitoring wafer includes forming a barrier layer of several thicknesses on the substrate surface.
3. The method for monitoring the degree of fluoride attack according to claim 2, characterized in that, The barrier layer is made of materials including TiN, Ti, TaN, and Co.
4. The method for monitoring the degree of fluoride attack according to claim 2, characterized in that, The barrier layer has various thicknesses ranging from 2nm to 20nm.
5. The method for monitoring the degree of fluoride attack according to claim 1, characterized in that, The nucleation layer can be selected from various thicknesses within the range of 5nm to 50nm.
6. The method for monitoring the degree of fluoride attack according to claim 1, characterized in that, Forming several simulated patterns on the substrate surface of the monitoring wafer includes forming several simulated patterns with different aspect ratios on the substrate surface.
7. The method for monitoring the degree of fluoride attack according to claim 1, characterized in that, The initial reflectance of each of the simulated patterns is obtained using reflectance measurement techniques, and the surface reflectance of the tungsten layer on each of the simulated patterns is obtained using reflectance measurement techniques. The degree of fluorine attack is assessed based on the initial reflectance and the surface reflectance of each of the simulated patterns.
8. The method for monitoring the degree of fluoride attack according to claim 7, characterized in that, Assessing the degree of fluorine attack based on the initial reflectance and surface reflectance of each of the simulated patterns includes: denoting the initial reflectance on the current simulated pattern as R_before and the surface reflectance as R_after, and calculating the rate of change of reflectance ΔR% according to the following formula: ΔR% = (R_after - R_before) / R_before × 100% The reflectance change rate corresponding to different simulated patterns was analyzed, and the absolute value of the reflectance change rate was positively correlated with the degree of fluorine attack on the substrate.
9. The method for monitoring the degree of fluoride attack according to claim 8, characterized in that, After obtaining the reflectivity change rate of different types of simulated patterns, the maximum value of the absolute value of the reflectivity change rate is obtained, and when the maximum value of the absolute value of the reflectivity change rate exceeds a preset threshold, an alarm is immediately triggered and the tungsten deposition process parameters are checked or adjusted.
10. A monitoring system for the degree of fluorine attack, characterized in that, The monitoring of the degree of fluorine attack is performed using the monitoring method described in any one of claims 1-9.