Etching parameter monitoring method and etching parameter monitoring equipment

Abstract

The invention provides an etching parameter monitoring method and etching parameter monitoring equipment, and the method comprises the steps: detecting the size of an opening of a to-be-etched opening region, and judging whether the size of the opening of the to-be-etched opening region is smaller than or equal to a preset size threshold value or not; if yes, forming a target opening area with a preset shape at an idle position within a laser detection range of etching parameter monitoring equipment on the wafer based on the opening size of the opening area to be etched; wherein the opening size of the target opening area is greater than the minimum opening size; in the etching process of the to-be-etched opening area and the target opening area, laser signals are emitted to the target opening area, and the etching depth of the target opening area is detected based on the laser signals reflected by the target opening area; and determining the etching depth of the to-be-etched opening region based on the opening size of the target opening region, the opening size of the to-be-etched opening region and the etching depth of the target opening region. According to the invention, the detection error of the etching depth is reduced, and the accuracy of the etching depth detection of the opening region is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method and device for monitoring etching parameters. Background Technology

[0002] Optical modules and optical chips have become hot topics in the semiconductor industry. Optical chips differ from conventional electronic chips in their process specifications. Optical chips place greater emphasis on indicators that significantly impact optical paths and interference, such as surface roughness and film thickness. Dry etching requires specialized processing and monitoring equipment for optical chips. While some etching equipment is equipped with optical emission spectroscopy (OES) as an etching endpoint detection system, OES-equipped etching equipment can only monitor the etching of materials with a cutoff layer and cannot monitor the etching depth of the film in real time. In optical chip-related fields, such as the 300 nm etching of LiNbO3 (LN) and the fixed-depth etching of thin films integrating InP and GaAs lasers, endpoint monitoring is ineffective. Related etching depth monitoring technologies typically use lasers to detect etching depth. However, laser etching depth detection requires a high aperture size in the opening region. When the opening size is small, an effective reflected light path cannot be formed, leading to a large detection error and reducing the accuracy of etching depth detection in the opening region. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide an etching parameter monitoring method and an etching parameter monitoring device, which reduces the detection error of etching depth and improves the accuracy of etching depth detection in the opening area.

[0004] To achieve the above objectives, the technical solutions adopted in the embodiments of the present invention are as follows: In a first aspect, embodiments of the present invention provide an etching parameter monitoring method, applied to an etching parameter monitoring device, the etching parameter monitoring method comprising: The opening size of the area to be etched is detected, and it is determined whether the opening size of the area to be etched is less than or equal to a preset size threshold; wherein, the preset size threshold is the minimum opening size in which the laser emitted by the etching parameter monitoring device can form an effective reflected light path in the opening area; If so, a target opening area of ​​a preset shape is formed in an empty position within the laser detection range of the etching parameter monitoring device on the wafer, based on the opening size of the opening area to be etched; wherein, the opening size of the target opening area is larger than the minimum opening size; During the etching process of the opening area to be etched and the target opening area, a laser signal is emitted toward the target opening area, and the etching depth of the target opening area is detected based on the laser signal reflected by the target opening area; The etching depth of the opening area to be etched is determined based on the opening size of the target opening area, the opening size of the opening area to be etched, and the etching depth of the target opening area.

[0005] Furthermore, this embodiment of the invention provides a first possible implementation of the first aspect, wherein the laser of the etching parameter monitoring device is located directly above the center of the wafer, and the step of forming a target opening region of a preset shape based on the opening size of the opening region to be etched within an empty position of the laser detection range of the etching parameter monitoring device on the wafer includes: Based on the opening size of the opening area to be etched, a target opening area of ​​the preset shape with an enlarged opening size is formed in an empty position within a preset size range at the center of the wafer.

[0006] Furthermore, this embodiment of the invention provides a second possible implementation of the first aspect, wherein the step of forming a target opening region of the preset shape with an enlarged opening size at an empty position within a preset size range at the center of the wafer, based on the opening size of the opening region to be etched, includes: When the opening size of the opening area to be etched is greater than the first preset size and less than or equal to the preset size threshold, the target opening area with the opening size of the first size is formed in the idle position; When the opening size of the area to be etched is greater than the second preset size but less than or equal to the first preset size, the target opening area with the second size is formed in the idle position; wherein, the second size is less than or equal to the first size; When the opening size of the area to be etched is less than or equal to the second preset size, the target opening area with the third size is formed in the idle position.

[0007] Furthermore, this embodiment of the invention provides a third possible implementation of the first aspect, wherein the step of determining the etching depth of the opening region to be etched based on the opening size of the target opening region, the opening size of the opening region to be etched, and the etching depth of the target opening region includes: The ratio between the etching depth of the opening area to be etched and the etching depth of the target opening area is determined based on the opening size of the opening area to be etched and the opening size of the opening area to be etched. The etching depth of the opening region to be etched is calculated based on the product of the etching depth of the target opening region and the proportional relationship.

[0008] Furthermore, this embodiment of the invention provides a fourth possible implementation of the first aspect, wherein the step of determining the ratio between the etching depth of the opening region to be etched and the etching depth of the target opening region based on the opening size of the opening region to be etched and the opening size of the opening region to be etched includes: When the opening size of the area to be etched is greater than a first preset size and less than or equal to the preset size threshold, the proportional relationship is determined to be a first value; wherein, the target opening area of ​​the preset shape includes a corner opening area; When the opening size of the opening area to be etched is greater than the second preset size and less than or equal to the first preset size, the proportional relationship is calculated based on the ratio of the opening size of the target opening area to the opening size of the opening area to be etched. When the opening size of the area to be etched is less than or equal to the second preset size, the proportional relationship is determined to be the second value.

[0009] Furthermore, this embodiment of the invention provides a fifth possible implementation of the first aspect, wherein the step of detecting the etching depth of the target opening region based on the laser signal reflected from the target opening region includes: The laser signal reflected from the target opening region is converted into an electrical signal, the number of waveforms in the electrical signal is counted, and the thin film refractive index of the film layer where the target opening region is located is obtained. The etching depth of the target opening region is determined based on the number of waveforms and the refractive index of the thin film.

[0010] Furthermore, this embodiment of the invention provides a sixth possible implementation of the first aspect, which further includes: When the opening size of the etchable opening area is greater than the preset size threshold, and the etchable opening area is not within the laser detection range, a target opening area of ​​the preset shape with the same opening size as the etchable opening area is formed at an empty position within the laser detection range of the etching parameter monitoring device on the wafer.

[0011] Furthermore, the present invention provides a seventh possible implementation of the first aspect, which further includes: The laser signal reflected from the target opening region is obtained, and a pre-fitted functional relationship between the signal intensity and the surface roughness is obtained. The signal intensity of the laser signal reflected from the target opening region is periodically input into the functional relationship to obtain the surface roughness of the target opening region.

[0012] Furthermore, the present invention provides an eighth possible implementation of the first aspect, wherein the target opening area of ​​the preset shape includes an opening area with any one of the shapes of L-shape, cross shape and circle.

[0013] Secondly, embodiments of the present invention also provide an etching parameter monitoring device, comprising: a signal acquisition module and a controller; the signal acquisition module is communicatively connected to the controller; the signal acquisition module includes a CCD camera and a laser; the laser is used to emit laser signals to the wafer; The CCD camera is used to acquire wafer images and collect laser signals reflected by the wafer; The controller includes a processor and a storage device; the storage device stores a computer program that, when executed by the processor, performs the method as described in any of the first aspects.

[0014] This invention provides an etching parameter monitoring method and an etching parameter monitoring device. The etching parameter monitoring method includes: detecting the opening size of an opening region to be etched; determining whether the opening size of the opening region to be etched is less than or equal to a preset size threshold; wherein the preset size threshold is the minimum opening size at which a laser emitted by the etching parameter monitoring device can form an effective reflected light path in the opening region; if so, forming a target opening region of a preset shape at an empty position within the laser detection range of the etching parameter monitoring device on the wafer based on the opening size of the opening region to be etched; wherein the opening size of the target opening region is greater than the minimum opening size; during the etching process of the opening region to be etched and the target opening region, emitting a laser signal to the target opening region; detecting the etching depth of the target opening region based on the laser signal reflected by the target opening region; and determining the etching depth of the opening region to be etched based on the opening size of the target opening region, the opening size of the opening region to be etched, and the etching depth of the target opening region. This invention increases the size and shape of the target opening region by adding a target opening region that meets the size and shape requirements in an empty position within the laser detection range on the wafer when the opening size of the opening region to be etched is small. The etching depth of the opening region to be etched is determined based on the detection depth of the target opening region that can accurately detect the etching depth. This expands the opening size of the opening region that needs to detect the etching depth, realizes the monitoring of etching depth under different opening sizes, reduces the detection error of etching depth, and improves the accuracy of etching depth detection of the opening region.

[0015] Other features and advantages of the embodiments of the present invention will be set forth in the following description, or some features and advantages may be inferred from the description or determined without doubt, or may be learned by practicing the techniques described above in the embodiments of the present invention.

[0016] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 A flowchart of an etching parameter monitoring method provided by an embodiment of the present invention is shown; Figure 2 This illustration shows a graphic example of a target opening area design provided by an embodiment of the present invention; Figure 3 An example waveform diagram of a reflected signal provided by an embodiment of the present invention is shown; Figure 4 This diagram illustrates the structure of an etching parameter monitoring device provided in an embodiment of the present invention. Figure 5 This invention provides a flowchart for monitoring etching depth according to an embodiment of the invention. Figure 6 This diagram illustrates a dimension-induced depth loading effect and a topographic loading effect provided by an embodiment of the present invention. Figure 7 This diagram illustrates a design schematic of a feature opening region in the center region of a wafer, provided by an embodiment of the present invention. Figure 8a This diagram illustrates the difference in etching morphology caused by the opening size, as provided in an embodiment of the present invention. Figure 8b This diagram illustrates a difference in etching morphology caused by another opening size, as provided in an embodiment of the present invention. Figure 9 A flowchart of a surface roughness monitoring process provided by an embodiment of the present invention is shown. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0020] Currently, relevant etching depth monitoring technologies typically include interferometry endpoint detection (IEP) and laser endpoint detection (LEP). However, IEP detection uses a large spot size, capable of simultaneously covering patterns of various sizes. Differences in etching depth caused by critical dimension loading (CD loading) can interfere with the IEP signal, hindering effective monitoring. Furthermore, IEP has specific requirements for aperture ratio, and its light source coherence is inferior to lasers, while also being weaker and susceptible to glow discharge after ignition, making etching error calibration difficult. Therefore, accurately detecting etching depth during the etching process of optical chips has become a pressing issue.

[0021] To address the aforementioned issues, this invention provides a method and device for monitoring etching parameters. The following provides a detailed description of the embodiments of this invention.

[0022] This embodiment provides a method for monitoring etching parameters, which can be applied to etching parameter monitoring equipment. (See [link]). Figure 1 The flowchart shown illustrates the etching parameter monitoring method, which mainly includes the following steps: Step S102: Detect the opening size of the area to be etched, and determine whether the opening size of the area to be etched is less than or equal to a preset size threshold. Based on the detection of the opening size of the opening area to be etched using a microscope or scanning electron microscope, the aforementioned preset size threshold is the minimum opening size in which the laser emitted by the etching parameter monitoring device can form an effective reflected light path in the opening area. This preset size threshold may be, for example, 2 μm.

[0023] Step S104: If yes, a target opening area of ​​a preset shape is formed in the idle position within the laser detection range of the etching parameter monitoring device on the wafer, based on the opening size of the opening area to be etched. When the opening size of the area to be etched is smaller than the minimum opening size (i.e., the preset size threshold), the laser will not be able to form an effective reflected light path due to diffraction problems, resulting in low accuracy of etching depth detection in the area to be etched. It is necessary to design a feature opening area within the laser detection range of the etching parameter monitoring equipment on the wafer based on the opening size of the area to be etched, that is, to form a target opening area of ​​a preset shape in the idle position within the laser detection range.

[0024] The unoccupied areas within the laser detection range mentioned above refer to the non-chip regions (i.e., the blank spaces between chips) within the laser irradiation range on the wafer. The laser detection range can be a circle on the wafer with a radius of 5 mm to 1 cm centered on the laser irradiation center.

[0025] In one embodiment, the laser irradiation range is within a radius of 1 cm centered on the wafer center. This range satisfies the movement range of the laser spot by the optical moving platform of the etching parameter monitoring device, and a target opening area of ​​a preset shape is formed in the blank space between chips within a radius of 1 cm centered on the wafer center.

[0026] In one embodiment, the target opening area with the aforementioned preset shape includes an opening area having any one of the shapes of L-shape, cross shape, and circle, see example... Figure 2 The example graphic design of the target opening area shown above can be an L-shaped, cross-shaped, or circular graphic with a set shape.

[0027] If the feature openings at the wafer center are designed with conventional patterns such as rectangles and circles, multiple etching verifications are required when there are etching load effects caused by various sizes. This results in poor compatibility, low fault tolerance, and increased impact on the etching of footings and subtrenches when there are large size differences, necessitating optimization of the etching formula. However, since the loading effect includes macroscopic loading, density loading, and dimensional loading, dimensional loading is difficult to address by optimizing the etching formula. Designing the feature openings with conventional patterns makes it difficult to solve the problem of monitoring etching depth at different sizes.

[0028] By designing a specially shaped opening area within the laser irradiation range, overall compatibility can be improved. By adding a target opening area within the laser irradiation range, the laser spot can be accurately irradiated onto the monitoring location (i.e., the location of the target opening area).

[0029] Step S106: During the etching process of the opening area to be etched and the target opening area, a laser signal is emitted towards the target opening area, and the etching depth of the target opening area is detected based on the laser signal reflected from the target opening area. The aforementioned etching parameter monitoring equipment includes a laser, which is used to emit laser signals to the target opening area on the wafer. After the etching process of the opening area to be etched and the target opening area begins, the laser signals reflected by the target opening area are collected, and the etching depth and surface roughness of the target opening area are detected based on the laser signals reflected by the target opening area.

[0030] Since the target opening area is located within the detection range of the laser, and can be positioned directly opposite the laser spot, the laser spot can remain stationary or be controlled to move within the laser detection range during the etching process of the opening area to be etched and the target opening area.

[0031] Step S108: Determine the etching depth of the opening area to be etched based on the opening size of the target opening area, the opening size of the opening area to be etched, and the etching depth of the target opening area.

[0032] When the opening size of the area to be etched is different, different proportions of etching depth will be formed in the target opening area. By performing corresponding proportional calculations based on the etching depth of the target opening area, the etching depth of the area to be etched can be calculated. During the etching process of the area to be etched and the target opening area, the etching depth of the target opening area is periodically detected and the etching depth of the area to be etched is calculated, realizing the monitoring of the etching depth of the area to be etched. It can be applied to the etching depth monitoring of opening areas with various opening sizes and shapes, and can effectively reduce the opening limitations of etched products.

[0033] The etching parameter monitoring method provided in this embodiment increases the opening size of the area to be etched by adding a target opening area that meets the size and shape requirements in the empty position of the laser detection range on the wafer when the opening size of the opening area to be etched is small. The etching depth of the opening area to be etched is determined according to the detection depth of the target opening area that can accurately detect the etching depth. This expands the opening size of the opening area that needs to detect the etching depth, realizes the monitoring of etching depth under different opening sizes, reduces the detection error of etching depth, and improves the accuracy of etching depth detection of the opening area.

[0034] In one embodiment, the laser of the etching parameter monitoring device is located directly above the center of the wafer. This embodiment provides a specific implementation method for forming a target opening region of a preset shape based on the opening size of the opening region to be etched within the idle position of the laser detection range of the etching parameter monitoring device on the wafer: Based on the opening size of the opening area to be etched, a target opening area with a pre-defined shape is formed in an empty space within a pre-defined size range at the center of the wafer.

[0035] When the opening size of the area to be etched is less than or equal to a preset size threshold, the laser cannot form an effective reflection loop due to diffraction issues. To obtain an effective laser reflection signal, a target opening area with an enlarged opening size is formed in an empty position within the laser detection range. The opening size of the target opening area is greater than the preset size threshold, which can form an effective reflection loop, thereby allowing for accurate monitoring of the etching depth of the target opening area. The opening size of the target opening area is related to the opening size of the area to be etched.

[0036] In one specific implementation, when the opening size of the opening area to be etched (usually the minimum size of the opening area to be etched) is greater than a first preset size and less than or equal to a preset size threshold, a target opening area with the opening size of the first size is formed in the idle position; The value range of the first preset size can be 1.2-1.7 μm, preferably 1.5 μm. When the opening size of the area to be etched is between the first preset size and the preset size threshold, the size loading effect is small, and a target opening area of ​​a preset shape is formed within 1 cm of the wafer center. The opening size of the target opening area is the first size, and the value range of the first size can be 2 μm-10 μm, so that the etching depth of the target opening area can be accurately detected.

[0037] When the opening size of the area to be etched (usually the minimum size of the area to be etched) is greater than the second preset size and less than or equal to the first preset size, a target opening area with the second size is formed in the idle position; wherein, the second size is less than or equal to the first size; The value range of the second preset size can be 500-900 nm, preferably 700 nm. When the opening size of the area to be etched is between the second preset size and the first preset size, the loading effect brought about by this size changes approximately linearly in the range of 700-2500 nm, forming a target opening area with the second size within 1 cm of the wafer center. The value range of the second size is 2 μm - 3 μm.

[0038] When the opening size of the area to be etched is less than or equal to the second preset size, a target opening area with the third size is formed in the idle position.

[0039] When the minimum size of the etchable opening region does not exceed the second preset size, the loading effect changes approximately exponentially, and other variations may also exist. A target opening region with a third size is formed within 1 cm of the wafer center to meet laser emission requirements. This also allows for the fabrication of small-sized patterns and avoids errors caused by etching issues such as footing and subtrenching. The value of the aforementioned third size ranges from 2 μm to 4 μm.

[0040] When the minimum size of the opening region to be etched is less than 80 nm, other process problems may easily occur, and the etching depth cannot be monitored using LEP.

[0041] In one embodiment, this embodiment provides a specific implementation method for determining the etching depth of the opening region to be etched based on the opening size of the target opening region, the opening size of the opening region to be etched, and the etching depth of the target opening region: The ratio between the etching depth of the opening to be etched and the etching depth of the target opening area is determined based on the opening size of the opening area to be etched. The etching depth of the opening region to be etched is calculated by multiplying the etching depth of the target opening region with the proportional relationship.

[0042] The etching depth of the opening region to be etched is positively correlated with the etching depth of the target opening region; the greater the detected etching depth of the target opening region, the greater the etching depth of the opening region to be etched. The ratio between the etching depth of the opening region to be etched and the etching depth of the target opening region is related to the opening size of the opening region to be etched.

[0043] In one specific implementation, when the opening size of the opening area to be etched is greater than a first preset size and less than or equal to a preset size threshold, the proportional relationship is determined to be a first value; wherein, the target opening area of ​​the preset shape includes a corner opening area; When the opening size of the area to be etched is greater than a first preset size but less than or equal to a preset size threshold, a target opening area with a corner is formed within 1 cm of the wafer center. At this point, the size loading effect error is small, less than 5%. The etching depth of the area to be etched is close to the etching depth of the target opening area. The aforementioned first value can be close to 1, meaning the detected etching depth of the target opening area can be used as the etching depth of the area to be etched. D = D 0, D 0 represents the etching depth of the target opening region.

[0044] When the opening size of the area to be etched is greater than the second preset size and less than or equal to the first preset size, the proportional relationship is calculated based on the ratio of the opening size of the target opening area to the opening size of the area to be etched. When the opening size of the area to be etched is greater than the second preset size and less than or equal to the first preset size, the load effect caused by the size changes approximately linearly. The ratio of the etching depth of the area to be etched to the etching depth of the target opening area is the ratio of the opening size of the target opening area to the opening size of the area to be etched. By monitoring the etching depth of the area to be etched proportionally, the monitoring error can be less than 5%.

[0045] The etching depth of the opening area to be etched D = D 0 L 2 / L 1, D 0 represents the etching depth of the target opening region. L 2 represents the opening size of the target opening area. L1 represents the opening size of the area to be etched.

[0046] When the opening size of the area to be etched is less than or equal to the second preset size, the proportional relationship is determined to be the second value.

[0047] When the opening size of the area to be etched is less than or equal to the second preset size, the loading effect is approximately exponential. It is necessary to use a standard process formula to perform a pre-etching experiment on a wafer with the same minimum opening size as the area to be etched and the target opening area to obtain the ratio of the etching depth of the area to be etched to the etching depth of the target opening area (i.e. the second value mentioned above), and obtain the proportional relationship between the etching depth of the area to be etched and the etching depth of the target opening area.

[0048] In one embodiment, this embodiment provides a specific implementation method for detecting the etching depth of a target opening region based on laser signals reflected from the target opening region: The laser signal reflected from the target opening region is converted into an electrical signal, the number of waveforms in the electrical signal is counted, and the refractive index of the film layer where the target opening region is located is obtained. The etching depth of the target opening region is determined based on the number of waveforms and the refractive index of the thin film.

[0049] The aforementioned etching parameter monitoring equipment includes a CCD camera (charge coupled device, also known as a CCD image sensor) and a controller (such as an industrial control computer LEP). The CCD camera collects the laser signal and imaging signal reflected from the target opening area, converts the laser signal reflected from the upper and lower surfaces of the thin film in the target opening area into electrical signals, and sends the electrical signal and imaging signal to the controller, so that the controller can calculate the etching depth of the target opening area based on the laser signal reflected from the target opening area.

[0050] Since the distance between the upper and lower surfaces of the film in the opening region decreases continuously with etching, the reduction in film thickness is the etching depth. D Etching depth D With the refractive index of the thin film n and laser wavelength λ There is a correlation, see as follows Figure 3 The example waveform of the reflected signal shown is statistically analyzed. Figure 3 The number of waveforms shown F (A waveform is defined between adjacent peaks or troughs). Based on the interference conditions of light, the intensity of coherent light changes periodically, from which the etching depth can be derived. D = λ / 2 n For etching the same material using the same equipment, the laser wavelength and refractive index can be assumed to be fixed values, while the etching depth and number of waveforms can be set as fixed values. The depth of etching in the target opening area can be calculated by monitoring the number of waveforms.

[0051] In one embodiment, the etching parameter monitoring method provided in this embodiment further includes: When the opening size of the area to be etched is larger than a preset size threshold and the area to be etched is not within the laser detection range, a target opening area of ​​the same preset shape and the same opening size as the area to be etched is formed in an empty position within the laser detection range of the etching parameter monitoring device on the wafer.

[0052] When the opening size of the area to be etched is larger than the preset size threshold, and the area to be etched is within the laser detection range (such as within 1 cm centered on the wafer center), the laser spot is controlled to move to the area to be etched to monitor the etching depth.

[0053] When the opening size of the area to be etched is larger than the preset size threshold and the area to be etched is not within the laser detection range, a target opening area is designed in the same way as the area to be etched within the laser detection range (such as within 1 cm centered on the wafer center). In order to improve the accuracy of the etching depth detection of the area to be etched, the opening size of the target opening area can be the same as the opening size of the area to be etched. By monitoring the etching depth of the target opening area, the etching depth of the area to be etched can be obtained.

[0054] In one embodiment, the etching parameter monitoring method provided in this embodiment further includes: The laser signal reflected from the target opening area is obtained, and the pre-fitted functional relationship between the signal intensity and the surface roughness is obtained. The signal intensity in the laser signal reflected from the target opening area is periodically input into the functional relationship to obtain the surface roughness of the target opening area.

[0055] Before detecting surface roughness, an etching process experiment needs to be performed in advance to obtain the signal intensity waveform of the laser signal reflected from the target opening area and the corresponding surface roughness data. Based on the signal intensity value in the signal intensity waveform of the laser signal reflected from the target opening area and the corresponding surface roughness dataset, the functional relationship between signal intensity and surface roughness is obtained. The signal intensity value in the intensity waveform obtained above can be the signal intensity at each peak or the signal intensity at each trough.

[0056] During the etching process of the target opening area and the opening area to be etched, the signal intensity at each peak or trough of the laser signal reflected from the target opening area is input into the functional relationship between signal intensity and surface roughness to obtain the surface roughness signal detected in each cycle.

[0057] In one embodiment, the detected roughness signal is also related to the detected film material. If the film material is LN, GaAs, or InP, the surface roughness is output based on the lowest or highest signal intensity of the collected laser signal. If the film material is a general-purpose film, the roughness signal is first output based on the lowest signal intensity of the collected laser signal. If the intensity of the roughness signal is lower than the algorithm's set value, the judgment is made based on the signal fluctuation over a short period of time, i.e., the signal-to-noise ratio. By selecting 3-10 fluctuation values, the roughness display signal is output.

[0058] The etching parameter monitoring method provided in this embodiment can monitor etching depth and surface roughness in real time during the etching process by emitting a laser to the wafer and collecting the laser signal reflected from the added target opening area. This can improve the process development progress of optical chips and monitor the stability of mass production processes. By designing a target opening area within the laser detection range, the etching parameter monitoring equipment can detect etching depth without controlling the movement of the laser device during the etching process, which can improve the stability of etching depth detection and simultaneously monitor etching depth and surface roughness.

[0059] Corresponding to the etching parameter monitoring method provided in the above embodiments, this invention provides an etching parameter monitoring device, which includes a signal acquisition module and a controller; the signal acquisition module is communicatively connected to the controller; the signal acquisition module includes a CCD camera and a laser; the laser is used to emit laser signals to the wafer; CCD cameras are used to acquire images of wafers and collect laser signals reflected from wafers; The controller includes a processor and a storage device; the storage device stores a computer program, which executes the etching parameter monitoring method provided in the above embodiments when run by the processor.

[0060] In one embodiment, the etching parameter monitoring device can be positioned above the etching reaction chamber, and the controller can include an industrial computer and a display, as shown in the example below. Figure 4The schematic diagram of the etching parameter monitoring device shown in this embodiment includes an alloy base 41, an optical motion platform 42, an LEP signal acquisition module 43, a signal cable 44, an LEP industrial control computer 45, and a display 46. The LEP signal acquisition module 43 is connected to the LEP industrial control computer 45 and the display 46 through the signal cable 44. The alloy base 41 is located on the top plate above the reaction chamber 47. The reaction chamber 47 can be based on an inductively coupled plasma (ICP) etching machine or a capacitively coupled plasma (CCP) etching machine. The radio frequency coil in the reaction chamber 47 can be a three-dimensional coil or a planar coil. The top plate of the reaction chamber 47 is provided with a light-transmitting hole, which can be circular or rectangular. A light-transmitting sheet with good light transmission is installed on the light-transmitting hole. The light-transmitting sheet can be made of a sapphire single crystal wafer with good light transmission. The light-transmitting hole with the light-transmitting sheet forms a skylight inside the top plate of the reaction chamber 47. The light-transmitting skylight is a detachable consumable part. When the deposited by-products affect the light transmission performance of the light-transmitting sheet, causing the laser signal to decrease by ≥10%, a new light-transmitting sheet must be replaced immediately.

[0061] The thickness of the alloy base 41 installed on the top plate above the reaction chamber 47 can be 1-5 cm. The material of the alloy base 41 can be metal alloys such as steel and aluminum. The alloy base 41 is a buffer fixing layer that can be detachably installed on the top plate above the reaction chamber 47. For example, it can be fixed to the top plate of the chamber with 4-8 screws to reduce the vibration caused by the use of the equipment.

[0062] The aforementioned optical motion platform 42 can be an automatic control platform capable of moving along the X and Y directions. The LEP signal acquisition module 43, mounted on the optical motion platform 42, enables movement control of the LEP signal acquisition module 43. The size and weight of the LEP signal acquisition module 43 meet the requirements of a module height ≤ 20 cm and a weight ≤ 2 kg. By setting these height and weight requirements, the need to lower the center of gravity can be met. The LEP signal acquisition module 43 internally integrates a CCD camera, a laser, and an LED illumination source. The CCD camera is used for imaging and collecting reflected laser signals, converting them into electrical signals. The laser is an active light source with good coherence, low interference from background light sources such as glow discharge and illumination, and small monitoring errors. After the equipment is installed, the laser is normally on, emitting red and infrared light with wavelengths ≥ 600 nm and a laser power ≤ 2 mW to meet laser safety standards. The LED illumination source is a switchable and adjustable brightness cold light source, avoiding heating effects and improving image clarity.

[0063] The LEP signal acquisition module 43 is equipped with a signal cable 44 at its bottom. The total weight of the signal cable 44 must be less than 500g. The signal cable 44 must be installed at the bottom of the LEP signal acquisition module 43 and fixed to the bottom platform to lower the overall center of gravity of the LEP signal acquisition module 43 and prevent the LEP signal acquisition module 43 from shaking when moving horizontally. This can effectively prevent the laser beam path from tilting when moving the spot position.

[0064] The signal cable 44 installed at the bottom of the LEP signal acquisition module 43 connects to the LEP industrial computer 45. The LEP industrial computer 45 can be a general-purpose computer system, equipped with common accessories such as a monitor, mouse, and keyboard. The industrial computer has an internal signal processing system that displays the electrical signals converted by the CCD and the imaging signals collected by the camera on the monitor. It achieves visualized movement of the laser spot through an optical motion platform and monitors the etching depth of the opening area in real time by collecting the electrical signals fed back from the CCD camera.

[0065] Based on the foregoing embodiments, this embodiment provides an example of applying the aforementioned etching parameter monitoring method, see, for example... Figure 5 The etching depth monitoring flowchart shown below can be followed as follows: Step 1: Use a microscope or scanning electron microscope (SEM) to detect the opening size of the opening area to be etched. When the minimum size of the pattern of the opening area to be etched is greater than 2 μm, and the opening area to be etched is located in the central region (within a circle with a radius of 1 cm centered on the wafer center), the opening area to be etched is regarded as the feature opening area (i.e. the target opening area). Control the laser spot to move to the feature opening area to realize the LEP monitoring of the etching depth. If the area to be etched is not in the center of the wafer, an L-shaped feature opening area is designed in the center of the wafer, and the laser spot is controlled to move to the feature opening area to achieve LEP monitoring of the etching depth. Step 2: When the minimum size of the pattern of the opening area to be etched is ≤2 μm, the laser cannot form an effective reflected light path due to diffraction and other problems, which reduces the feasibility of monitoring the etching depth. It is necessary to design the feature opening area on the mask in the free area of ​​the wafer center region according to the size of the opening area. When the type of etched wafer is complex and the surface patterns vary significantly, see, for example... Figure 6 The diagram illustrates the depth loading effect and morphology loading effect caused by size. The etching depth varies significantly for patterns of different sizes. Furthermore, LEP (Loop Electron Precipitation) cannot directly monitor the etching of openings smaller than 2 μm. Therefore, please refer to... Figure 7 The schematic diagram shown illustrates the design of the feature opening area in the center region of the wafer. A design such as... is required in the center region of the wafer. Figure 7The featured opening region shown is designed to be located within a radius of 5 mm to 1 cm centered on the wafer center, satisfying the movement range of the laser spot by the optical motion platform. The opening shape can be rectangular or circular. A special opening region is also designed to improve overall compatibility. This feature opening region design enables the laser spot to be accurately moved to the monitoring position. (See example...) Figure 8a and Figure 8b The diagram shows the difference in etching morphology caused by the opening size. Different opening sizes in the opening area will result in different proportions of etching depth. By calculating the corresponding proportions, the actual monitored etching depth can be obtained. By designing a feature opening area in the center region of the wafer, the opening limitation of the etched product can be effectively reduced. At the same time, wafers of various shapes and sizes can be used to monitor the etching depth in this system.

[0066] Step 3: When the minimum size of the patterned opening area (i.e. the opening size of the opening area to be etched) is in the range of 1.5 μm-2.0 μm, the error of the size loading effect is <5%. An L-shaped feature opening area is formed on the mask of the free area with a radius of 1 cm centered on the wafer center. The opening size of the L-shaped feature opening area can be enlarged to 2 μm-10 μm by imitating the opening area. The laser spot is controlled to move to the feature opening area to realize the monitoring of the etching depth by LEP. Step 4: When the minimum size of the patterned opening region (i.e., the opening size of the opening region to be etched) is in the range of 700 nm-1500 nm, the loading effect caused by the size changes approximately linearly in the range of 700-2500 nm. The minimum size of the feature opening region... L 2. The design depth is 2.5 μm. Proportional depth monitoring is performed, and the monitoring error is <5%. Therefore, the etching depth of the opening region to be etched is determined. D =Etching depth of the feature opening region D 0 L 2 / L 1, L 1 represents the opening size of the area to be etched, and the laser spot is controlled to move to the feature opening area to achieve LEP monitoring of the etching depth; Step 5: When the minimum size of the patterned opening region (i.e., the opening size of the opening region to be etched) is in the range of 80 nm-700 nm, the loading effect is approximately exponential, and other variations may also exist. For testing, an L-shaped feature opening region with a linewidth of 2-4 μm needs to be pre-etched at the center of the sample. This satisfies the laser emission requirements and is compatible with the etching morphology of small-sized patterns, avoiding errors caused by etching issues such as base plates or trenches. At this point, a standard pre-etching formula is required to obtain the etching depth of the opening region to be etched. d 1. Etching depth of the feature opening region d The ratio of 2 αThe etching depth of the opening area to be etched D =Etching depth of the feature opening region D 0 / α .

[0067] When the minimum size of the etched opening region is less than 80 nm, other process issues exist, making it impossible to monitor the etching depth using LEP.

[0068] The aforementioned L-shaped feature opening area is mainly divided into a long side, a corner, and a short side (upper and lower parts). The top part of the long side of the L-shape can be used to monitor the etching depth changes caused by the subtrench. That is, the long strip of the L-shape is used to monitor the etching depth of the trench morphology proportionally. Figure 8a As shown, the edge of the pattern is best monitored using the long side of the L-shaped opening; the corner of the L-shape is used to monitor the etching depth of the opening with footing. The intersection of the short and long sides forms the superimposed morphology of the footing, as shown... Figure 8b As shown, the middle area of ​​the long side of the L-shaped feature can normally monitor the etching depth of openings without special morphology. The L-shaped feature opening area is the simplest and most compatible feature opening area. The design of the L-shaped feature opening area should meet the following points: the height of L (i.e., the length of the long side) should be in the range of 50-300 μm, which makes it easy to find the pattern under the lens and move the laser spot to the opening area; the length of the short side should be in the range of 10-40 μm, which can form an equivalent etching footing phenomenon, and the effect will not be insignificant due to the short side being too short, making it easier to monitor a more realistic etching depth; the opening width (i.e., the opening size) of the L pattern should be ≥2 μm and ≤10 μm to meet the laser reflection requirements.

[0069] Based on the above-mentioned LEP etching depth monitoring method, real-time monitoring of etching depth can be achieved. The collected laser signals reflected from the opening region are then processed to form a scheme for real-time roughness monitoring. If signal monitoring is not performed according to the above scheme, the resulting roughness signal may have significant errors due to the etching morphology.

[0070] Corresponding to the etching depth monitoring process provided in the above embodiments, this embodiment provides a roughness monitoring example, see below. Figure 9 The surface roughness monitoring flowchart shown below illustrates the main steps of this method: Step (1): Before the process begins, edit the formula and select film materials such as LN, GaAs, InP or general film layers according to the optical chip material. General film layers are multi-layer structures or other material film layers. The process monitoring formula is based on the film material to monitor the roughness of the film layer.

[0071] Step (2): After etching begins, the LEP monitoring system automatically runs. If the film material is LN, GaAs, or InP, the surface roughness is monitored based on the laser signal reflected from the collected opening area. The surface roughness is output based on the lowest signal intensity of the collected laser signal. This roughness is only used as a display signal and does not output other signals to interfere with the process. If the film material is a general-purpose film, the roughness signal is first output based on the lowest signal intensity of the collected laser signal. If the intensity of the roughness signal is lower than the algorithm's set value, the judgment is made based on the signal fluctuation within a short period of time, i.e., the signal-to-noise ratio. By selecting 3-10 fluctuation values, the roughness display signal is output. The roughness result output by the LEP system display is updated every 2-5 seconds, which can avoid fluctuations caused by system errors and improve stability. After the deep monitoring outputs the etching endpoint, the final roughness result displayed is the result 1-5 seconds before the process stops, which can reduce vibration errors caused when etching stops.

[0072] This invention provides a computer-readable medium storing computer-executable instructions. When these computer-executable instructions are invoked and executed by a processor, they cause the processor to implement the methods described in the above embodiments.

[0073] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process of the system described above can be referred to the corresponding process in the foregoing embodiments, and will not be repeated here.

[0074] Furthermore, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0075] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0076] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0077] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for monitoring etching parameters, characterized in that, The etching parameter monitoring method is applied to an etching parameter monitoring device, and the etching parameter monitoring method comprises the following steps: Detecting an opening size of a to-be-etched opening region, and determining whether the opening size of the to-be-etched opening region is less than or equal to a preset size threshold; wherein the preset size threshold is a minimum opening size at which effective reflected light paths can be formed in the opening region by laser emitted by the etching parameter monitoring device; If yes, forming a target opening region of a preset shape at a free position of the etching parameter monitoring device on the wafer within a laser detection range of the etching parameter monitoring device based on the opening size of the to-be-etched opening region; wherein the opening size of the target opening region is greater than the minimum opening size; During etching of the to-be-etched opening region and the target opening region, emitting a laser signal to the target opening region, and detecting an etching depth of the target opening region based on the laser signal reflected by the target opening region; Determining the etching depth of the to-be-etched opening region based on the opening size of the target opening region, the opening size of the to-be-etched opening region, and the etching depth of the target opening region.

2. The method of claim 1, wherein, The laser of the etching parameter monitoring device is located directly above the center of the wafer, and the step of forming the target opening region of the preset shape at the free position of the etching parameter monitoring device on the wafer within the laser detection range of the etching parameter monitoring device based on the opening size of the to-be-etched opening region comprises the following steps: Forming the target opening region of the preset shape with an enlarged opening size at the free position of the wafer within a preset size range of the center of the wafer according to the opening size of the to-be-etched opening region.

3. The method of claim 2, wherein, The step of forming the target opening region of the preset shape with an enlarged opening size at the free position of the wafer within a preset size range of the center of the wafer according to the opening size of the to-be-etched opening region comprises the following steps: When the opening size of the to-be-etched opening region is greater than a first preset size and less than or equal to the preset size threshold, forming the target opening region with a first size of the opening size at the free position; When the opening size of the to-be-etched opening region is greater than a second preset size and less than or equal to the first preset size, forming the target opening region with a second size of the opening size at the free position; wherein the second size is less than or equal to the first size; When the opening size of the to-be-etched opening region is less than or equal to the second preset size, forming the target opening region with a third size of the opening size at the free position.

4. The method of claim 1, wherein, The step of determining the etching depth of the to-be-etched opening region based on the opening size of the target opening region, the opening size of the to-be-etched opening region, and the etching depth of the target opening region comprises the following steps: Determining a proportional relationship between the etching depth of the to-be-etched opening region and the etching depth of the target opening region based on the opening size of the to-be-etched opening region and the opening size of the to-be-etched opening region; Calculating the etching depth of the to-be-etched opening region based on the product of the etching depth of the target opening region and the proportional relationship.

5. The method of claim 4, wherein, The step of determining the proportional relationship between the etching depth of the to-be-etched opening region and the etching depth of the target opening region based on the opening size of the to-be-etched opening region and the opening size of the to-be-etched opening region comprises the following steps: When the opening size of the to-be-etched opening region is greater than a first preset size and less than or equal to the preset size threshold, the proportion relationship is determined as a first value; wherein the target opening region of the preset shape includes a corner-shaped opening region; When the opening size of the to-be-etched opening region is greater than a second preset size and less than or equal to the first preset size, the proportion relationship is calculated based on the ratio of the opening size of the target opening region to the opening size of the to-be-etched opening region; When the opening size of the to-be-etched opening region is less than or equal to the second preset size, the proportion relationship is determined as a second value.

6. The method of claim 1, wherein, The step of detecting the etching depth of the target opening region based on the laser signal reflected by the target opening region comprises: Converting the laser signal reflected by the target opening region into an electrical signal, counting the number of waveforms in the electrical signal, and obtaining the thin film refractive index of the film layer where the target opening region is located; Determining the etching depth of the target opening region based on the number of waveforms and the thin film refractive index.

7. The method of claim 1, wherein, Further comprising: When the opening size of the to-be-etched opening region is greater than the preset size threshold, and the to-be-etched opening region is not within the laser detection range, forming a target opening region of the preset shape with the same opening size as the to-be-etched opening region at an idle position within the laser detection range of the etching parameter monitoring device on the wafer.

8. The method of claim 1, wherein, Further comprising: Obtaining the laser signal reflected by the target opening region, obtaining a function relationship between signal intensity and surface roughness obtained by pre-fitting, inputting the signal intensity in the laser signal reflected by the target opening region into the function relationship periodically, and obtaining the surface roughness of the target opening region.

9. The method according to any one of claims 1 to 8, characterized in that, The target opening region of the preset shape includes an opening region with any one of L-shaped, cross-shaped and circular shapes.

10. An etching parameter monitoring apparatus, comprising: Comprise: A signal acquisition module and a controller; The signal acquisition module is in communication connection with the controller; the signal acquisition module comprises a CCD camera and a laser; the laser is used to emit a laser signal to a wafer; The CCD camera is used to collect wafer images and collect laser signals reflected by the wafer; The controller comprises a processor and a storage device; the storage device stores a computer program, and the computer program performs the method of any one of claims 1 to 9 when executed by the processor.

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