Method for forming etching hole

Abstract

The invention provides a method for forming an etching hole, and the method comprises the steps: providing a wafer which comprises a substrate and a to-be-etched film layer located on the surface of the substrate; removing a part of the to-be-etched film layer by adopting a preset etching process, and forming an etching hole in the substrate; in the process of forming the etching hole, collecting optical information of the bottom of the etching hole in real time by using a CCD (Charge Coupled Device) camera; calculating the real-time depth of the etching hole based on the optical information; and comparing the real-time depth of the etching hole with a preset depth, and adjusting etching process parameters according to a comparison result so as to execute etching compensation on the etching hole. By introducing a mode of real-time optical acquisition-etching hole real-time depth calculation-etching process parameter dynamic adjustment in the etching process, high-precision and real-time monitoring and compensation can be performed on the etching hole depth, and device performance degradation or structure damage caused by insufficient etching hole depth or too deep etching hole is avoided. Therefore, the consistency and the stability of the etching hole depth are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a method for forming an etching hole. BACKGROUND

[0002] The etching process is one of the core links of chip manufacturing, which transfers the circuit pattern on the mask to the silicon wafer through chemical or physical methods, thereby forming key components such as transistors and interconnection structures. In this process, the accurate control of etching depth is crucial. If the depth is insufficient, it may cause the transistor channel to be too short to cause leakage; if the depth is too deep, it may damage the underlying material, causing circuit short circuit or signal delay.

[0003] However, the traditional etching process has many challenges in depth control. First, material heterogeneity interference is obvious. Generally, the materials to be etched include silicon, silicon dioxide, metal compounds, etc., and the etching rate of different materials can differ by several times, making it difficult for traditional processes to adapt to such changes. Second, device dynamic fluctuations also pose difficulties for depth control. Finally, the temperature, gas flow, and RF power of the plasma etching machine are easily affected by the environment, resulting in etching depth deviations in the same batch of silicon wafers. In addition, multi-step coordination difficulty is also a problem. Complex chips require dozens of etching steps, and the depth error of each step may accumulate, ultimately affecting the overall structure accuracy.

[0004] As chip manufacturing continues to move towards smaller nanometer scales, such as 3nm, 2nm, and other advanced processes, the requirement for etching hole depth control has reached an unprecedented level. Traditional etching processes are difficult to meet the needs of modern high-precision, high-integration chip manufacturing. Therefore, the existing technology has defects and needs to be improved and developed. SUMMARY

[0005] The purpose of the present application is to provide a method for forming an etching hole to solve the problems raised in the background art.

[0006] To achieve the above purpose, the present application provides the following technical solutions:

[0007] A method for forming an etching hole, comprising:

[0008] providing a wafer, the wafer comprising a substrate and a to-be-etched film layer on the surface of the substrate;

[0009] using a preset etching process to remove part of the to-be-etched film layer to form an etching hole on the substrate;

[0010] During the formation of the etching hole, a CCD camera is used to collect optical information of the bottom of the etching hole in real time;

[0011] Based on the optical information, the real-time depth of the etching hole is calculated;

[0012] The real-time depth of the etched hole is compared with the preset depth, and the etching process parameters are adjusted according to the comparison results to perform etching compensation on the etched hole.

[0013] Specifically, the real-time depth of the etched hole is compared with a preset depth, and the process parameters of the etching process are adjusted according to the comparison result to perform etching compensation on the etched hole.

[0014] Calculate the ratio of the real-time depth of the etched hole to the preset depth;

[0015] When the ratio is less than or equal to 0.95, adjust the etching process parameters to perform positive etching compensation on the etched holes;

[0016] When the ratio is greater than or equal to 1.05, adjust the etching process parameters to perform negative etching compensation on the etched holes;

[0017] When the ratio is greater than 0.95 and less than 1.05, the etching compensation for the etched holes is suspended, and the preset process parameters are applied to the etched holes.

[0018] The etching process parameters include etching RF power and etching gas flow rate. The single adjustment range of etching RF power shall not exceed ±5% of the preset RF power, and the single adjustment range of etching gas flow rate shall not exceed ±10% of the preset gas flow rate.

[0019] Specifically, the optical information at the bottom of the etched hole is acquired in real time using a CCD camera, including:

[0020] Provides a light source and emits light;

[0021] The light rays are reflected by the mirror and focused by the first lens, forming perpendicular light rays that enter the etched hole.

[0022] Vertical light rays are incident on the bottom of the etched hole and reflected by it. Then, they are transmitted to the CCD camera through the second lens so that the CCD camera can collect optical information about the bottom of the etched hole.

[0023] This includes, after providing a light source and using the light source to generate light, the following:

[0024] Light is filtered using an adjustable filter array;

[0025] The adjustable filter group is configured to selectively transmit light of a preset wavelength, which matches the emission wavelength of the etching products generated during the etching process.

[0026] The etching product includes SiF4, and the preset wavelength includes 777nm; or the etching product includes CO, and the preset wavelength includes 483nm.

[0027] Before using a CCD camera to acquire optical information from the bottom of the etched hole in real time, the process also includes aligning and adjusting the etched hole, specifically including:

[0028] Obtain alignment marks on the wafer, including notches located at the edge of the wafer and / or photolithographic marks located on the surface of the wafer;

[0029] Machine vision positioning algorithms are used to identify and locate alignment marks, and a coordinate system for the wafer is established.

[0030] The coordinates of the center of the hole to be etched in the XY plane on the upper surface of the wafer (x0, y0) and the center of the second lens in the XY plane (x1, y1) are calculated based on the wafer coordinate system.

[0031] Calculate the planar distance D between the center of the etched hole and the center of the second lens, where ;

[0032] When the planar distance D is greater than the preset deviation threshold, the relative position of the etched hole and the second lens is adjusted so that the adjusted planar distance D is less than or equal to the preset deviation threshold.

[0033] The optical information includes the average light intensity of the light reflected from the bottom of the etched hole. Based on the optical information of the etched hole, the depth of the etched hole is calculated, specifically including:

[0034] The average light intensity I of the reflected light from the bottom of the etched hole is acquired using a CCD camera, and the depth Z of the etched hole is calculated. ;

[0035] in, R is the average reflected light intensity of the wafer surface before the etching hole is formed, R is the Fresnel reflectivity of the interface between the bottom material of the etching hole and the air, and α is the effective absorption coefficient of the bottom material of the etching hole for light incident on the bottom of the etching hole.

[0036] The wafer is divided into multiple regions, and each region is equipped with an independently controlled etching process parameter control unit. When etching compensation is performed on the etched holes, the corresponding etching process parameter control unit is called according to the region where the etched holes are located to perform the etching compensation.

[0037] Among them, the diameter of the etched hole is greater than 5 μm, and / or the surface roughness Ra of the etched hole wall is ≤15 nm.

[0038] The beneficial effects of the above-mentioned technical solution of the present invention are as follows:

[0039] By introducing a method of "real-time optical acquisition - real-time depth calculation of etching holes - dynamic adjustment of etching process parameters" during the etching process, the depth of the etching holes can be monitored and compensated with high precision in real time. This avoids device performance degradation or structural damage caused by insufficient or excessive etching hole depth, thereby improving the consistency and stability of the etching hole depth and reducing the depth deviation between wafers in the same batch and between etching holes within a wafer. It is especially suitable for advanced process chip manufacturing and other scenarios with stringent etching precision requirements. Attached Figure Description

[0040] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding parts, wherein:

[0041] Figure 1 A schematic flowchart of a method for forming etched holes provided in an embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram of a process for performing etching compensation on etched holes, provided by an embodiment of the present invention;

[0043] Figure 3 This is a schematic diagram of a process for collecting optical information at the bottom of an etched hole, provided by an embodiment of the present invention.

[0044] Figure 4 An optical schematic diagram for collecting optical information at the bottom of an etched hole, provided as an embodiment of the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Those skilled in the art should understand that the embodiments described below are only some, not all, of the embodiments disclosed. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0046] To address some problems existing in the etching process of the prior art, embodiments of the present invention provide a method for forming etched holes.

[0047] like Figure 1 The diagram shown is a flowchart illustrating a method for forming etched holes according to an embodiment of the present invention. The specific process is as follows:

[0048] S1 provides a wafer, the wafer including a substrate and a film layer to be etched on the surface of the substrate;

[0049] S2, a preset etching process is used to remove part of the film layer to be etched, forming an etching hole on the substrate;

[0050] S3, During the process of forming the etched hole, the optical information at the bottom of the etched hole is collected in real time using a CCD camera;

[0051] S4, based on optical information, calculates the real-time depth of the etched hole;

[0052] S5 compares the real-time depth of the etched hole with the preset depth, and adjusts the etching process parameters according to the comparison result to perform etching compensation on the etched hole.

[0053] It should be noted that the wafer size is not particularly limited in this embodiment of the invention. The method of this embodiment can be applied to wafers of different sizes, such as 6-inch, 8-inch, or 12-inch wafers. In this embodiment, the wafer substrate can be selected from semiconductors or wide-bandgap materials such as single-crystal silicon (Si), silicon germanium (SiGe), silicon carbide (SiC), and gallium nitride (GaN), among which single-crystal silicon is the most commonly used substrate and is suitable for the manufacture of large-scale integrated circuits such as logic chips and memory devices.

[0054] In this embodiment of the invention, the material of the film to be etched can be selected according to the device structure and functional requirements. For example, when the film to be etched is a dielectric layer, its material can be silicon dioxide (SiO2), silicon nitride (Si3N4), or silicon oxynitride (SiON), which are commonly used as isolation layers, gate dielectric layers, etc. When the film to be etched is a metal or metal compound layer, its material can be aluminum (Al), copper (Cu), tungsten (W), titanium (Ti), tantalum (Ta), titanium nitride (TiN), tantalum nitride (TaN), etc., which are mainly used as metal interconnect layers, contact holes, through-holes (TSVs), etc. When the film to be etched is a semiconductor layer, its material can be polycrystalline silicon (Poly-Si) or amorphous silicon (a-Si), which are mostly used as gate electrodes, resistor structures, etc. In addition, the film to be etched can also be an organic polymer material (such as photoresist) as a temporary mask or sacrificial layer.

[0055] The etching process used in this embodiment of the invention can be dry etching. Dry etching refers to an etching method that combines physical bombardment and chemical reaction of the material surface using plasma or high-energy particle beams in a vacuum environment. Its core principle is as follows: A specific etching gas (such as fluorine-containing gas SF6, chlorine-containing gas Cl2, oxygen-containing gas O2, etc.) is introduced into the etching chamber. Under the action of a radio frequency electric field, the etching gas is excited to form a plasma containing active ions and free radicals. These active particles react chemically with the surface of the film to be etched, generating volatile etching products (such as SiF4, CO, etc.). Simultaneously, the high-energy ions in the plasma physically bombard the film surface, assisting in the removal of reaction products and unreacted film material, ultimately forming the desired etched holes on the substrate. Dry etching has significant advantages such as high etching rate, good etching selectivity (different etching rates for different materials), strong anisotropy (directional etching along the vertical direction), and high fidelity for fine patterns. Based on these characteristics, dry etching is widely used in the key pattern transfer process in semiconductor device manufacturing, especially suitable for advanced processes where high requirements are placed on the depth accuracy, sidewall contour flatness, and dimensional consistency of etched holes. It can effectively meet the process requirements of this invention for precise preparation and real-time compensation of etched holes.

[0056] In this embodiment of the invention, a CCD camera is used to acquire optical information from the bottom of the etched hole in real time. An integrated optical detection system allows for non-contact, high-speed, and high-precision acquisition of optical signals from the bottom of the etched hole. The core component of this system is the CCD camera (Charge-Coupled Device). A CCD camera is a solid-state imaging device that operates on the principle of photoelectric conversion and charge transfer. Its photosensitive surface consists of a large number of closely arranged photosensitive pixel units. When light signals illuminate the pixel units, photon energy is absorbed and electrons are excited, forming charge packets proportional to the light intensity. Subsequently, driven by a timing control circuit, these charge packets are transferred row by row or column by column along a shift register and read out, ultimately converting into digital electrical signals to quantize and image the light signal. In this embodiment of the invention, the CCD camera is not used to directly capture a two-dimensional image of the etched hole. Instead, it is focused on the bottom of the etched hole through a specific optical design to acquire reflected optical signals (such as the average reflected light intensity and light intensity gradient) from the bottom of the etched hole, ultimately achieving online detection of the hole depth.

[0057] It should be noted that online hole depth detection methods can also include inductive micrometer detection, capacitive grating detection, ultrasonic detection, laser frequency comb 3D contour detection, etc. The specific principles will not be elaborated here.

[0058] The method for forming etched holes provided in this invention introduces a closed-loop control mechanism of "real-time optical acquisition - real-time etched hole depth calculation - dynamic adjustment of etch process parameters" during the etching process. This mechanism enables high-precision, real-time monitoring and compensation of the etched hole depth, avoiding device performance degradation or structural damage caused by insufficient or excessive etched hole depth. It also improves the consistency and stability of the etched hole depth, reduces depth deviation between wafers in the same batch and between etched holes within a wafer, and is particularly suitable for advanced process chip manufacturing scenarios with stringent etching precision requirements.

[0059] like Figure 2 The diagram shown is a schematic flowchart of an embodiment of the present invention for performing etching compensation on etched holes. Specifically, step S5 involves comparing the real-time depth of the etched hole with a preset depth and adjusting the process parameters of the etching process based on the comparison result to perform etching compensation on the etched hole.

[0060] S501, calculate the ratio of the real-time depth of the etched hole to the preset depth;

[0061] S502, when the ratio is less than or equal to 0.95, adjust the etching process parameters to perform positive etching compensation on the etched holes;

[0062] S503, when the ratio is greater than or equal to 1.05, adjust the etching process parameters to perform negative etching compensation on the etched holes;

[0063] S504: When the ratio is greater than 0.95 and less than 1.05, etch compensation for the etched holes is suspended, and preset process parameters are applied to the etched holes.

[0064] The etching process parameters include etching RF power and etching gas flow rate. The single adjustment range of etching RF power shall not exceed ±5% of the preset RF power, and the single adjustment range of etching gas flow rate shall not exceed ±10% of the preset gas flow rate.

[0065] It should be noted that the preset depth in the embodiments of the present invention is not a fixed value, but is dynamically related to the formation stage of the etched hole. As the etching process continues, the etching progress at different time points is different, and the preset depth, which serves as a depth reference standard, will also be adjusted accordingly to ensure accurate matching with the expected progress of the current etching stage.

[0066] For example, if the total time to form a complete etched hole using a preset etching process is 10 minutes (i.e. 600 seconds), in order to achieve phased depth reference, the total etching time of 10 minutes can be evenly divided into 1000 time segments, with each segment having a time interval of 600 milliseconds; for each etching stage corresponding to a time segment, the etched hole depth that should be reached in that stage is pre-marked and recorded as Z0 (preset depth of the initial etching stage), Z1 (preset depth corresponding to the first time segment), and so on, up to Z1000 (preset depth of the final etching completion stage).

[0067] During the etching process, if the calculated ratio of the real-time etching depth to the preset depth at the current stage is ≤0.95, it indicates that the etching depth is lagging behind the expected progress at this stage. In this case, etching positive compensation needs to be performed, which can be achieved by adjusting the etching process parameters. For example, increasing the current etching RF power and etching gas flow rate can increase the etching rate, thereby reducing the difference between the real-time etching depth and the preset depth until the ratio returns to above 0.95, effectively ensuring that the final etching depth meets the target.

[0068] In this embodiment of the invention, to address the issue of insufficient current etching depth during the etching process, positive etching compensation can be performed to rapidly increase the current etching rate when the etching depth lags behind. This effectively prevents the depth deviation from accumulating as the etching process progresses, thereby ensuring that each etching stage strictly follows the preset schedule. This method is particularly suitable for applications where the film layer to be etched has high hardness and the etching rate is prone to decay (e.g., etching of silicon dioxide dielectric layers), effectively guaranteeing that the final etching depth meets the target.

[0069] During the etching process, when the calculated ratio of the real-time etching depth to the preset depth of the current stage is ≥1.05, it indicates that the etching depth has exceeded the expected range for this stage. If etching continues according to the original preset process parameters, it is easy to cause the subsequent etching depth to be too deep, damaging the substrate or other underlying structures. At this time, etching negative compensation needs to be performed, which can be achieved by adjusting the etching process parameters. For example, reducing the current etching RF power and etching gas flow rate will reduce the etching rate, thereby reducing the difference between the real-time etching depth and the preset depth until the ratio returns to less than 1.05, preventing the depth of subsequent etching holes from exceeding the limit further.

[0070] In this embodiment of the invention, when the current etching depth exceeds the limit during the etching process, negative etching compensation can be performed to reduce the current etching rate in a timely manner when the etching depth is ahead of schedule. This effectively prevents the depth deviation from continuing to expand as the etching process progresses, thereby ensuring that each etching stage can proceed in accordance with the preset schedule. This method is particularly suitable for application scenarios where there are sensitive underlying structures (such as metal interconnect layers or substrate interfaces) below the film to be etched, and where excessive etching is prone to damage (such as etching dielectric vias above metal interconnect layers), thus improving the safety and reliability of the etching process.

[0071] During the etching process, when the calculated ratio of the real-time etching depth to the preset depth of the current stage is greater than 0.95 and less than 1.05, it indicates that the etching depth is within the acceptable deviation range for this stage. If the etching process parameters are adjusted at this time, it may introduce new depth deviations due to parameter fluctuations or cause the etching rate to be unstable. Therefore, there is no need to activate the compensation mechanism. Instead, the etching compensation for the etching holes is paused, and the preset process parameters are continued to be applied to the etching holes (for example, keeping the current etching RF power, etching gas flow rate, gas ratio, and chamber pressure unchanged) to maintain a stable etching rate and plasma environment.

[0072] In this embodiment of the invention, when the current etch hole depth is within the acceptable deviation range for that stage during the etching process, by pausing the etching compensation process and maintaining the preset process parameters, unnecessary parameter adjustments can be avoided when the deviation is controllable. This effectively reduces etching rate oscillations and the introduction of new deviations caused by parameter fluctuations, thereby ensuring that the etching process is stable and controllable and that the depth deviation at each stage remains within an acceptable range. This method is particularly suitable for applications requiring high etch hole depth accuracy and where the etching process is sensitive to process stability (such as microstructure etching of MEMS devices and contact hole etching in advanced processes). It helps improve the consistency and yield of etch hole depth while reducing equipment wear and production costs.

[0073] It should be noted that the determination of whether to perform etching compensation based on the ratio of the real-time etching depth to the preset depth in this embodiment of the invention, as well as the specific thresholds for classifying the compensation type (i.e., 0.95 and 1.05), are not fixed and unadjustable values. Instead, they can be flexibly set according to factors such as actual etching process requirements, the characteristics of the film material to be etched, and the accuracy requirements of the etching holes. For example, if higher accuracy is required for the etching hole depth (e.g., the depth error needs to be controlled within ±3%), the compensation trigger threshold of the ratio can be adjusted to 0.97 (triggering positive compensation) and 1.03 (triggering negative compensation). Correspondingly, the ratio range for pausing compensation is 0.97-1.03. If the material to be etched is a material with high hardness and a slow etching rate, to avoid process fluctuations caused by frequent compensation, the compensation trigger threshold of the ratio can also be relaxed to 0.9 (triggering positive compensation) and 1.1 (triggering negative compensation). Correspondingly, the ratio range for pausing compensation is 0.9-1.1. Similarly, if it is necessary to reduce the range of the compensation pause interval, the interval span of 0.95-1.05 can be narrowed, or other reasonable ratios can be set according to the specific needs of the scenario.

[0074] Specifically, S3 involves using a CCD camera to collect optical information from the bottom of the etched hole in real time during the formation of the etched hole, including:

[0075] Provides a light source and emits light;

[0076] After being reflected by the mirror, the light is focused by the first lens to form a vertical light ray that is incident perpendicularly into the etched hole;

[0077] Vertical light rays are incident on the bottom of the etched hole and reflected by it. Then, they are transmitted to the CCD camera through the second lens so that the CCD camera can collect optical information about the bottom of the etched hole.

[0078] This includes, after providing a light source and using the light source to generate light, the following:

[0079] Light is filtered using an adjustable filter array;

[0080] The adjustable filter group is configured to selectively transmit light of a preset wavelength, which matches the emission wavelength of the etching products generated during the etching process.

[0081] like Figure 3 The diagram shown is a schematic flowchart illustrating a process for acquiring optical information from the bottom of an etched hole, according to an embodiment of the present invention. Figure 4 The diagram shown is an optical principle diagram for acquiring optical information at the bottom of an etched hole according to an embodiment of the present invention. For example, an optical information at the bottom of the etched hole is acquired in real time using a CCD camera, as detailed below:

[0082] S301 provides a light source and emits light. For example, the light source can be a highly stable monochromatic laser (such as a semiconductor laser with a wavelength adaptable to subsequent filtering requirements) or a broadband continuous light source (such as a xenon lamp with a monochromator). The intensity fluctuation of its output light must be controlled within ±2% to avoid deviations in reflected light intensity detection due to light source instability. For instance, in a silicon-based material etching scenario, a light source with an output power of 5-10mW can be selected to ensure that the light can penetrate the observation window of the etching chamber without damaging the film to be etched due to excessive power.

[0083] S302, the light is filtered by an adjustable filter group. After the light source generates light, the wavelength can be selected by the adjustable filter group. For example, the adjustable filter group can consist of 2-4 narrowband filters with different center wavelengths (wavelength range 400-800nm), and the wavelength switching is achieved by an electronically controlled switching module to ensure that only the preset wavelength light that matches the emission wavelength of the etched product is transmitted.

[0084] In S303, light is reflected by a mirror and focused by a first lens, forming a perpendicular ray that enters the etched hole. After filtering and reflection, the light then enters the first lens (an achromatic cemented doublet lens, with a focal length designed based on the distance between the observation window of the etching chamber and the etched hole, such as 20-50mm). The main function of the first lens is to calibrate the diverging incident light into parallel light, ultimately ensuring it is perpendicularly incident on the bottom of the etched hole. Optical simulation and actual adjustments can be used to ensure that the deviation between the incident angle of the light and the axis of the etched hole does not exceed ±0.5°, preventing the reflected light path from shifting due to tilted incidence and affecting subsequent signal acquisition.

[0085] S304, perpendicular light rays are incident on the bottom of the etched aperture and reflected, then transmitted to the CCD camera via the second lens to acquire optical information from the bottom of the etched aperture. The light rays incident perpendicularly to the bottom of the etched aperture, after reflection, are transmitted to the CCD camera via the second lens (an achromatic lens with parameters matched to the first lens, used to focus the parallel reflected light onto the photosensitive surface of the CCD camera). For example, the CCD camera can be an industrial-grade camera with a pixel resolution of 2048×2048 and a frame rate of 100-1000fps, whose photosensitive surface is precisely aligned with the focal point of the second lens to ensure complete imaging of the reflected light signal.

[0086] The optical information includes the average light intensity of the light reflected from the bottom of the etched hole. Based on the optical information of the etched hole, the depth of the etched hole is calculated, specifically including:

[0087] The average light intensity I of the reflected light from the bottom of the etched hole is acquired using a CCD camera, and the depth Z of the etched hole is calculated. ;

[0088] in, R is the average reflected light intensity of the wafer surface before the etching hole is formed, R is the Fresnel reflectivity of the interface between the bottom material of the etching hole and the air, and α is the effective absorption coefficient of the bottom material of the etching hole for light incident on the bottom of the etching hole.

[0089] Specifically, the collected optical information can be the average light intensity I of the light reflected from the bottom of the etched hole. That is, the CCD camera calculates the arithmetic mean of the light intensity values ​​of the imaging area of ​​the reflected light from the bottom of the etched hole (selecting the effective area of ​​200×200 pixels in the center to avoid the influence of edge distortion) to obtain the average light intensity I, which serves as the core parameter for subsequent depth calculation.

[0090] In this embodiment of the invention, the depth of the etched hole is calculated based on the optical information of the etched hole, specifically including:

[0091] First, on the wafer surface (before the film to be etched is etched), a CCD camera is used to collect the reflected light signal, and the light intensity is averaged in the area corresponding to the location of the subsequent etching hole to obtain the reference light intensity / incident light intensity before etching. . Multiple data collections (e.g., 10 times) are required, and the average value should be taken to eliminate random errors caused by slight fluctuations in the light source or environmental noise.

[0092] Secondly, during the etching process, the CCD camera continuously images the reflected light from the bottom of the etched aperture at a high frame rate (e.g., 100-1000 fps). To ensure data accuracy and stability, the image algorithm automatically selects the central portion of the reflected light imaging area at the bottom of the etched aperture as the effective calculation area, such as a 200×200 pixel square or a circular area with a diameter of approximately 200 pixels. The purpose of selecting the central area is to avoid reflection interference caused by oblique light incidence at the aperture edge and edge distortion of the optical system, thereby extracting the reflected light signal that best represents the true state of the aperture bottom. Subsequently, the light intensity values ​​of all pixels within this effective area are arithmetically averaged to obtain the real-time average light intensity I.

[0093] According to Beer-Lambert's law, when parallel monochromatic light passes perpendicularly through a uniform non-scattering medium, the intensity I of the emitted light decreases exponentially with the optical path (aperture depth) Z. Therefore, a perpendicular reflection-absorption model is established:

[0094] From this, the formula for depth Z can be derived:

[0095] depth

[0096] The meanings and methods of obtaining the parameters in the formula are as follows:

[0097] I0 (Reference Light Intensity / Incident Light Intensity): As mentioned above, this is the average reflected light intensity of the wafer surface before the etched holes are formed.

[0098] R (Fresnel reflectivity): This is a physical constant related to the material at the bottom of the etched hole and the wavelength of the incident light. It represents the proportion of light reflected when incident from air (or vacuum) onto the surface of the material at the bottom of the hole. For example, for light with a wavelength of 777 nm, the Fresnel reflectivity R at the silicon (Si)-air interface is approximately 0.35, and R at the silicon dioxide (SiO2)-air interface is approximately 0.15. This value can be determined in advance during the process preparation stage by consulting a materials optics handbook or using specialized equipment such as an ellipsometer.

[0099] α (Effective Absorption Coefficient): Also related to the bottom material and the incident light wavelength, it represents the degree to which energy is absorbed after light travels a unit distance in the bottom material (unit: ). For example, the effective absorption coefficient α of light with a wavelength of 777 nm in silicon is approximately 1200. In silicon dioxide, α is approximately 80. This parameter needs to be precisely calibrated during the process development stage by preparing a series of standard samples of known thickness and measuring their reflected light intensity, then using a formula to deduce the result or by measuring with specialized instruments.

[0100] In actual calculations, the average light intensity I collected in real time is combined with the pre-stored... Substitute these parameters into the above formula, and the real-time depth Z of the etched hole can be obtained through rapid calculation (usually completed in milliseconds).

[0101] In this embodiment of the invention, a vertical reflection-absorption model is established based on Beer-Lambert's law, enabling high-precision calculation of the etched hole depth. Simultaneously, the model's core parameters (such as...) It is only related to the material to be etched and the wavelength of the incident light, eliminating the need to redesign the optical system for different etching scenarios. Simply adjusting parameters according to material properties is sufficient to adapt to various etching requirements, such as silicon-based and carbon-containing films, significantly reducing process debugging complexity and greatly improving operational convenience. Furthermore, the entire optical information acquisition process, upon which depth calculation relies, is non-contact, avoiding the physical damage that contact detection might cause to the etched hole structure.

[0102] Before using a CCD camera to acquire optical information from the bottom of the etched hole in real time, the process also includes aligning and adjusting the etched hole, specifically including:

[0103] Obtain alignment marks on the wafer, including notches located at the edge of the wafer and / or photolithographic marks located on the surface of the wafer;

[0104] Machine vision positioning algorithms are used to identify and locate alignment marks, and a coordinate system for the wafer is established.

[0105] The coordinates of the center of the hole to be etched in the XY plane on the upper surface of the wafer (x0, y0) and the center of the second lens in the XY plane (x1, y1) are calculated based on the wafer coordinate system.

[0106] Calculate the planar distance D between the center of the etched hole and the center of the second lens, where ;

[0107] When the planar distance D is greater than the preset deviation threshold, the relative position of the etched hole and the second lens is adjusted so that the adjusted planar distance D is less than or equal to the preset deviation threshold.

[0108] Specifically, by using wafer alignment marks (such as edge notches or surface lithography marks) and combining them with machine vision positioning algorithms, the second lens (high-precision focusing lens) can be precisely aligned with the hole to be etched. The machine vision algorithm can control the recognition error of the lithography marks within ±0.5um. With the adjustment accuracy of the precision displacement module, the alignment deviation between the center of the second lens and the center of the etched hole is ≤2um (the preset deviation threshold is set to 2um). This ensures that the lens field of view (usually 50-100μm in diameter) can completely cover the etched hole area, avoiding the mixing of reflected light from the etched hole wall into the acquisition signal due to alignment deviation, or the fact that part of the bottom area of ​​the etched hole exceeds the lens field of view, which would affect the accuracy of subsequent average light intensity acquisition.

[0109] The etching product includes SiF4, and the preset wavelength includes 777nm; or the etching product includes CO, and the preset wavelength includes 483nm.

[0110] For example, the design of an adjustable filter array needs to balance the wavelength coverage range with precise adaptation to the etching products. Its wavelength adjustment range can be set to 400-800nm, which can cover the characteristic emission wavelengths of common products during the etching process. When the film to be etched is silicon, a fluorine-containing etching gas (such as SF6) is used for etching. The etching product silicon tetrafluoride (SiF4) generated by the reaction of silicon and SF6 will generate characteristic fluorescence with a center wavelength of 777nm in the plasma environment of the etching chamber. At this time, the adjustable filter array automatically switches to the filter with a center wavelength of 777nm. When the film to be etched is carbon-containing material (such as photoresist), oxygen is used as the etching gas. The etching product carbon monoxide (CO) generated by the reaction of photoresist and oxygen has a characteristic emission wavelength of 483nm in the plasma environment. The filter array then switches to the filter with a center wavelength of 483nm accordingly.

[0111] It can effectively filter out irrelevant stray light such as etched product light and plasma background light, significantly enhance the recognition of etch hole depth detection signals, and lay the foundation for the accuracy of subsequent optical information acquisition.

[0112] The wafer is divided into multiple regions, and each region is equipped with an independently controlled etching process parameter control unit. When etching compensation is performed on the etched holes, the corresponding etching process parameter control unit is called according to the region where the etched holes are located to perform the etching compensation.

[0113] To achieve precise etching compensation for etched vias, this invention employs independent wafer partition control. For example, the wafer to be etched can be divided into 100-200 independently controllable regions, each with an area of ​​5mm × 5mm. Each region is equipped with an independent etching process parameter control unit, specifically including a partitioned RF power control unit that can independently adjust the RF power of the corresponding region, and a local gas flow regulating valve that equips each region with an independent gas nozzle and can precisely adjust the local etching gas flow rate. When compensation is required for a specific etched via, its location is first determined, and then the control unit corresponding to that region is invoked. By fine-tuning the output of the partitioned RF power control unit and controlling the nozzle flow rate through the local gas flow regulating valve, precise compensation for a single etched via in the partition is ultimately achieved, preventing overall parameter adjustments from affecting the etching status of other regions.

[0114] Among them, the diameter of the etched hole is greater than 5 μm, and / or the surface roughness Ra of the etched hole wall is ≤15 nm.

[0115] During the etching process, when light strikes the bottom of the etched hole, if the hole diameter is too small, light diffraction can easily occur. This means the light will deviate from its straight-line propagation path and diffract around to the hole wall or outside the hole. Consequently, the light actually reflected back to the CCD camera does not originate entirely from the effective reflection area at the bottom of the hole, leading to distortion of the average light intensity I (e.g., a lower intensity value or excessive fluctuation). This problem can be effectively avoided when the etched hole diameter is greater than 5 μm. When the hole diameter exceeds 5 μm, light propagation within the hole is predominantly linear, and the diffraction effect is negligible. This ensures that the average reflected light intensity I accurately reflects the light reflection state at the bottom of the hole, providing an accurate foundation of light intensity data for subsequent depth calculations.

[0116] The surface roughness of the etched aperture wall directly affects the light reflection characteristics: if the aperture wall roughness Ra > 15 nm, the light incident on the aperture wall will experience additional scattering attenuation. Some light will be scattered in a non-preset direction due to the irregular protrusions and depressions of the rough surface, and will not be able to return to the CCD camera along the original light path. This results in the average value of the collected reflected light intensity I being lower than the light intensity value of an ideal smooth surface, causing deviations in the depth calculation results. By setting the aperture wall roughness Ra ≤ 15 nm, this additional scattering attenuation can be significantly reduced, making the reflection of light in the aperture mainly specular reflection, thus preserving the effective reflected light signal to the maximum extent.

[0117] In summary, by setting the diameter of the etched hole to be greater than 5 μm and the surface roughness Ra of the etched hole wall to be less than 15 nm, the accuracy of the average reflected light intensity I is ensured from both diffraction and scattering dimensions, laying a data foundation for the accurate calculation of the etched hole depth in the future.

[0118] In this embodiment of the invention, by introducing a method of "real-time optical acquisition - real-time depth calculation of etching holes - dynamic adjustment of etching process parameters" during the etching process, the depth of the etching holes can be monitored and compensated with high precision and in real time. This avoids device performance degradation or structural damage caused by insufficient or excessive etching hole depth, thereby improving the consistency and stability of the etching hole depth and reducing the depth deviation between wafers in the same batch and between etching holes within a wafer. This method is particularly suitable for advanced process chip manufacturing and other scenarios with stringent etching precision requirements.

[0119] The above-described preferred embodiments of the present invention are provided as examples, but it will be apparent to those skilled in the art that such embodiments are provided merely by way of example. Many modifications, alterations, and alternatives will occur to those skilled in the art without departing from the spirit and intent of the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in the practice of the invention. The appended claims are intended to define the scope of protection of the invention and therefore cover the modular compositions, equivalents, or alternatives within the scope of these claims.

Claims

1. A method for forming etched holes, characterized in that, include: A wafer is provided, the wafer including a substrate and a film layer to be etched located on the surface of the substrate; A portion of the film layer to be etched is removed using a preset etching process to form etch holes on the substrate; During the formation of the etched hole, an optical information of the bottom of the etched hole is acquired in real time using a CCD camera; Based on the optical information, the real-time depth of the etched hole is calculated; The real-time depth of the etched hole is compared with the preset depth, and the etching process parameters are adjusted according to the comparison result to perform etching compensation on the etched hole.

2. The method for forming etched holes as described in claim 1, characterized in that, The real-time depth of the etched hole is compared with a preset depth, and the process parameters of the etching process are adjusted according to the comparison result to perform etching compensation on the etched hole, specifically including: Calculate the ratio of the real-time depth of the etched hole to the preset depth; When the ratio is less than or equal to 0.95, the etching process parameters are adjusted to perform positive etching compensation on the etched hole; When the ratio is greater than or equal to 1.05, the etching process parameters are adjusted to perform negative etching compensation on the etched hole; When the ratio is greater than 0.95 and less than 1.05, the etching compensation for the etched hole is suspended, and the preset process parameters are applied to the etched hole.

3. The method for forming etched holes as described in claim 2, characterized in that, The etching process parameters include etching RF power and etching gas flow rate, wherein the single adjustment range of the etching RF power does not exceed ±5% of the preset RF power, and the single adjustment range of the etching gas flow rate does not exceed ±10% of the preset gas flow rate.

4. The method for forming etched holes as described in claim 1, characterized in that, The method of using a CCD camera to acquire optical information of the bottom of the etched hole in real time specifically includes: Provides a light source and emits light; The light is reflected by a mirror and focused by a first lens to form a vertical light beam that enters the etched hole. The vertical light rays are incident on the bottom of the etched hole and reflected by it, then transmitted through the second lens to the CCD camera, so that the CCD camera can collect the optical information of the bottom of the etched hole.

5. The method for forming etched holes as described in claim 4, characterized in that, After providing the light source and generating light using the light source, the method further includes: The light is filtered by an adjustable filter array; The adjustable filter group is configured to selectively transmit light of a preset wavelength, which matches the emission wavelength of the etching product generated during the etching process.

6. The method for forming etched holes as described in claim 5, characterized in that, The etching product includes SiF4, and the preset wavelength includes 777nm; or the etching product includes CO, and the preset wavelength includes 483nm.

7. The method for forming etched holes as described in claim 4, characterized in that, Before acquiring the optical information of the bottom of the etched hole in real time using a CCD camera, the method further includes aligning and adjusting the etched hole, specifically including: Obtain alignment marks on the wafer, the alignment marks including notches located at the edge of the wafer and / or photolithographic marks located on the surface of the wafer; The alignment marks are identified and located using a machine vision positioning algorithm to establish the coordinate system of the wafer; The center coordinates (x0, y0) of the hole to be etched in the XY plane on the upper surface of the wafer and the center coordinates (x1, y1) of the second lens in the XY plane are calculated based on the coordinate system of the wafer. Calculate the planar distance D between the center of the etched hole and the center of the second lens, where ; When the planar distance D is greater than a preset deviation threshold, the relative position of the etched hole and the second lens is adjusted so that the adjusted planar distance D is less than or equal to the preset deviation threshold.

8. The method for forming etched holes as described in claim 1, characterized in that, The optical information includes the average light intensity of the light reflected from the bottom of the etched hole. The calculation of the depth of the etched hole based on this optical information specifically includes: The average light intensity I of the reflected light from the bottom of the etched hole is acquired using a CCD camera, and the depth Z of the etched hole is calculated. ; in, R is the average reflected light intensity of the wafer surface before the etching hole is formed, R is the Fresnel reflectivity of the interface between the bottom material of the etching hole and the air, and α is the effective absorption coefficient of the bottom material of the etching hole for light incident on the bottom of the etching hole.

9. The method for forming etched holes as described in claim 1, characterized in that, The wafer is divided into multiple regions, and each region is equipped with an independently controlled etching process parameter control unit. When etching compensation is performed on the etching holes, the corresponding etching process parameter control unit is called according to the region where the etching holes are located to perform etching compensation.

10. The method for forming etched holes as described in claim 1, characterized in that, The diameter of the etched hole is greater than 5 μm, and / or the surface roughness Ra of the etched hole wall is ≤15 nm.

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