Method and device for improving plasma etching first sheet effect

Abstract

The embodiment of the invention provides a method and a device for improving a plasma etching first-piece effect. The method comprises the following steps: carrying out etching operation on a first wafer to an Mth wafer in a first batch of wafers, carrying out cleaning operation on an etching chamber, and carrying out etching operation on an (M + 1) th wafer to an Nth wafer; obtaining a first etching size of a middle etching position of the Mth wafer, a second etching size of an edge etching position of the Mth wafer, a third etching size of a middle etching position of the Lth wafer and a fourth etching size of the edge etching position of the Lth wafer; m + 1 < = L < = N; obtaining a first size difference based on the first etching size and the third etching size; obtaining a second size difference based on the second etching size and the fourth etching size; obtaining a first relation model and a second relation model; determining a first gas adjustment amount based on the first size difference, a first relation model and a second relation model; and determining a second gas adjustment amount based on the second size difference, the first relation model and the second relation model.

Description

Technical Field

[0001] The present disclosure relates to the technical field of integrated circuit manufacturing, and in particular to a method and a device for improving the first-chip effect of plasma etching. Background Art

[0002] As the critical dimensions of integrated circuits continue to shrink, the requirements for the integration of electronic devices are also increasing. To this end, the wafer manufacturing process has introduced a plasma etching process with high etching accuracy and easy-to-control etching morphology. The plasma etching process may include: passing the etching gas into a vacuum chamber, connecting an RF power supply to the chamber, and the etching gas generates plasma under the action of the RF power supply. The ions, atomic groups, etc. in the plasma act on the surface of the wafer to achieve the etching effect. Among them, during the etching process, continuously accumulated by-products will be generated in the chamber; usually, in order to ensure that the by-products do not cause defects in subsequent batches of wafers, the chamber is cleaned after a period of etching to restore the chamber environment to normal.

[0003] However, in some etching processes, since the etching process produces a lot of byproducts and these byproducts have a great impact on the chamber environment, a relatively strong cleaning procedure is required, and this strong cleaning procedure often leads to the problem of over-cleaning of the chamber. After over-cleaning, the chamber environment changes significantly, making the critical dimension of the first etched wafer (also understood as the etching dimension) much larger than the target dimension. This defect is called the first wafer effect. This not only affects the yield of the product, but also increases the production cost and time cost. Summary of the invention

[0004] In view of this, in order to solve one or more of the existing technical problems, the embodiments of the present disclosure propose a method and a device for improving the first-wafer effect of plasma etching. On the one hand, the method for improving the first-wafer effect of plasma etching proposed in the present disclosure includes: performing an etching operation on the 1st to Mth wafers in the first batch of wafers, cleaning the etching chamber where the first batch of wafers are located, and performing the etching operation on the M+1th to Nth wafers in the first batch of wafers; obtaining a first etching size of the middle etching position of the Mth wafer and a second etching size of the edge etching position, as well as a third etching size of the middle etching position of the Lth wafer and a fourth etching size of the edge etching position; M+1≤L≤N; obtaining a first size based on the first etching size and the third etching size The invention relates to a method for obtaining a first gas adjustment amount based on the first size difference, the first relationship model and the second relationship model of the etching size of the middle etching position of the etched wafer and the intermediate gas usage and the edge gas usage, and a second relationship model between the etching size of the edge etching position and the intermediate gas usage and the edge gas usage; the intermediate gas usage is the amount of etching gas used when etching the middle etching position of the etched wafer, and the edge gas usage is the amount of etching gas used when etching the edge etching position of the etched wafer; based on the first size difference and the first relationship model and the second relationship model, a first gas adjustment amount is determined; and based on the second size difference and the first relationship model and the second relationship model, a second gas adjustment amount is determined.

[0005] In some embodiments, the method also includes: obtaining the first gas usage and the second gas usage when etching the Mth wafer in the second batch of wafers; the first gas usage is the amount of etching gas used when etching the middle etching position of the Mth wafer in the second batch of wafers, and the second gas usage is the amount of etching gas used when etching the edge etching position of the Mth wafer in the second batch of wafers; based on the first gas usage and the first gas adjustment amount, determining the amount of etching gas used for the middle etching position of the Lth wafer in the second batch of wafers when the etching operation is performed on the Lth wafer in the second batch of wafers; and based on the second gas usage and the second gas adjustment amount, determining the amount of etching gas used for the edge etching position of the Lth wafer in the second batch of wafers when the etching operation is performed on the Lth wafer in the second batch of wafers.

[0006] In some embodiments, the amount of etching gas used for etching the middle etching position of the Lth wafer in the second batch of wafers is the sum of the first gas usage and the first gas adjustment amount; the amount of etching gas used for etching the edge etching position of the Lth wafer in the second batch of wafers is the sum of the second gas usage and the second gas adjustment amount.

[0007] In some embodiments, the method also includes: determining whether the values ​​of the first size difference and the second size difference are less than a preset value; wherein, when the values ​​of the first size difference and the second size difference are less than the preset value, determining that when etching the Lth to last wafers in the second batch of wafers, the amount of etching gas used is the same as the amount of etching gas used to etch the Mth wafer in the second batch of wafers.

[0008] In some embodiments, the first relationship model is: Yc=AXc+BXe+C; the second relationship model is: Ye=DXc+EXe+F; wherein, Yc is the etching size of the middle etching position of the etched wafer; Ye is the etching size of the edge etching position of the etched wafer; Xc is the intermediate gas usage; Xe is the edge gas usage; A, B, D and E are coefficient constants corresponding to the etching system where the etching chamber is located; C and F are constants.

[0009] In some embodiments, the method also includes: obtaining a first relationship based on the first relationship model: ΔYc=AΔXc+BΔXe; and obtaining a second relationship based on the second relationship model: ΔYe=DΔXc+EΔXe; wherein ΔYc is the etching size difference of the middle etching position of the two etched wafers; ΔYe is the etching size difference of the edge etching position of the two etched wafers, ΔXc is the difference in the amount of etching gas used when etching the middle etching position of the two wafers, and ΔXe is the difference in the amount of etching gas used when etching the edge etching position of the two wafers; based on the first size difference, the second size difference, the first relationship and the second relationship, the first gas adjustment amount and the second gas adjustment amount are calculated.

[0010] In some embodiments, the method also includes: etching the middle etching position and the edge etching position of the sample wafer using the sample gas in the etching chamber, and obtaining a first experimental etching size and a second experimental etching size, respectively; obtaining the amount of etching gas used in the sample gas when etching the middle etching position of the sample wafer, and the amount of etching gas used when etching the edge etching position of the sample wafer, to obtain the first experimental gas usage and the second experimental gas usage; based on the first experimental gas usage, the second experimental gas usage, the first experimental etching size and the second experimental etching size, as well as the first relationship model and the second relationship model, calculate the coefficient constants A, B, D and E, and constants C and F.

[0011] In some embodiments, the first size difference is obtained based on the first etching size and the third etching size; and the second size difference is obtained based on the second etching size and the fourth etching size, including: obtaining the first etching size corresponding to the middle etching position of the Mth wafer in multiple batches of wafers and the second etching size corresponding to the edge etching position; and obtaining the third etching size of the middle etching position and the fourth etching size of the edge etching position of the Lth wafer in multiple batches of wafers; performing difference calculation and averaging of multiple first etching sizes and multiple third etching sizes to obtain the first size difference; performing difference calculation and averaging of multiple second etching sizes and multiple fourth etching sizes to obtain the second size difference.

[0012] In some embodiments, the etching gas used in the etching operation includes one of oxygen, carbon tetrafluoride (CF4) and octafluorocyclobutane (C4F8).

[0013] The disclosed embodiment proposes a device for improving the first-wafer effect of plasma etching, and the system includes: a reaction unit, configured to: perform an etching operation on the 1st to Mth wafers in the first batch of wafers, perform a cleaning operation on the etching chamber where the first batch of wafers are located, and perform the etching operation on the M+1th to Nth wafers in the first batch of wafers; an acquisition unit, configured to: obtain a first etching size of the middle etching position of the Mth wafer and a second etching size of the edge etching position, as well as a third etching size of the middle etching position of the Lth wafer and a fourth etching size of the edge etching position; M+1≤L≤N; a calculation unit, configured to: obtain a first size difference based on the first etching size and the third etching size; and, based on the second etching size and the fourth etching size, obtain a first size difference. The second size difference is obtained by measuring the size of the middle etching position of the etched wafer; the acquisition unit is also configured to: obtain a first relationship model between the etching size of the middle etching position of the etched wafer and the intermediate gas usage and the edge gas usage, and a second relationship model between the etching size of the edge etching position and the intermediate gas usage and the edge gas usage; the intermediate gas usage is the amount of etching gas used when etching the middle etching position of the etched wafer, and the edge gas usage is the amount of etching gas used when etching the edge etching position of the etched wafer; the determination unit is configured to: determine the first gas adjustment amount based on the first size difference and the first relationship model and the second relationship model; and determine the second gas adjustment amount based on the second size difference and the first relationship model and the second relationship model.

[0014] In the disclosed embodiment, the 1st to Mth wafers in the first batch of wafers are first etched, and then a cleaning operation is performed, and then the M+1th to Nth wafers in the first batch of wafers are etched. Next, by obtaining the first etching size of the middle etching position and the second etching size of the edge etching position of the Mth etched wafer before the cleaning operation, and obtaining the third etching size of the middle etching position and the fourth etching size of the edge etching position of the Lth etched wafer after the cleaning operation, and comparing the first etching size with the third etching size to obtain a first size difference, and comparing the second etching size with the fourth etching size to obtain a second size difference, the etching size difference between the Mth etched wafer before the cleaning operation and the Lth etched wafer after the cleaning operation is determined; and then by obtaining a corresponding relationship model between the etching size and the etching gas dosage , and determine the adjustment amount of the etching gas (the first gas adjustment amount and the second gas adjustment amount) based on the etching size difference (the first size difference and the second size difference); in this way, during the etching of the second batch of wafers, when etching the wafers after the cleaning operation, by adjusting the amount of etching gas, the etching size of the middle etching position and the edge etching position of the etched wafer after the cleaning operation is controlled, thereby effectively improving the first-piece effect in plasma etching, thereby reducing the influence of over-cleaning on the plasma etching process, improving etching accuracy and stability, and improving the uniformity of the etching positions in the etched wafers, while reducing production costs and defective product rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of a reaction chamber in a plasma etching device provided in an embodiment of the present disclosure;

[0016] Figure 2 A flow chart of a method for improving the first-chip effect of plasma etching provided by an embodiment of the present disclosure;

[0017] Figure 3 A schematic top view of a wafer on an XY plane provided by an embodiment of the present disclosure;

[0018] Figure 4 A schematic diagram of adjusting the amount of etching gas for a second batch of wafers provided in an embodiment of the present disclosure;

[0019] Figure 5 A schematic diagram of a device for improving the first-chip effect of plasma etching provided by an embodiment of the present disclosure.

[0020] In the above drawings (which are not necessarily drawn to scale), similar reference numerals may describe similar components in different views. Similar reference numerals with different letter suffixes may represent different examples of similar components. The accompanying drawings generally illustrate various embodiments discussed herein by way of example and not limitation. DETAILED DESCRIPTION

[0021] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the specific embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0022] In the following description, a large number of specific details are given to provide a more thorough understanding of the present disclosure. However, it is obvious to those skilled in the art that the present disclosure can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present disclosure, some technical features known in the art are not described; that is, all features of actual embodiments are not described here, and well-known functions and structures are not described in detail.

[0023] In the drawings, the sizes of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0024] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present disclosure necessarily has the first element, component, region, layer or part.

[0025] Spatially relative terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used here for convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is turned over, then the elements or features described as "under other elements" or "under it" or "under it" will be oriented as "on" other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0026] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present disclosure. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0027] In order to enable a more detailed understanding of the features and technical contents of the embodiments of the present disclosure, the implementation of the embodiments of the present disclosure is described in detail below in conjunction with the accompanying drawings. The attached drawings are for reference only and are not used to limit the embodiments of the present disclosure.

[0028] Plasma etching has been widely used in the manufacturing process of electronic devices; Figure 1 , Figure 1 A schematic diagram of a reaction chamber in a plasma etching device provided in an embodiment of the present disclosure; wherein, the etching process of the wafer in the reaction chamber includes: placing the wafer to be etched in the reaction chamber, introducing etching gas into the reaction chamber, the etching gas decomposes under the action of the electric field and generates plasma, the plasma bombards the surface of the wafer to be etched to form an etching site, or the reactive elements (free radicals and reactive atoms) generated by the plasma react with the substances on the surface of the wafer to be etched to form an etching site.

[0029] Byproducts are generated during the etching process, and the content of the byproducts affects the etching environment in the reaction chamber; for example, when the byproduct concentration in the reaction chamber is within the preset concentration range, the etching rate remains within the preset range, and the etching size of the etched wafer is within the preset size range; however, when the byproduct concentration in the reaction chamber is higher than the preset concentration range, the plasma does not fully etch the wafer surface, the etching size becomes smaller, and the etching effect is affected. Based on this, after a certain period of etching, the reaction chamber is cleaned, that is, the byproducts are discharged through the reaction chamber outlet to restore the byproduct concentration in the reaction chamber to the preset concentration range, thereby ensuring that the etching size is within the preset size range.

[0030] However, in some etching processes, since the etching process produces a large number of by-products and these by-products have a greater impact on the reaction chamber environment, a relatively strong cleaning procedure is required to perform the cleaning operation. This strong cleaning operation causes the reaction chamber to be over-cleaned, making the reaction chamber too clean. As a result, when etching subsequent batches of wafers, the etching rate increases, which in turn causes the etching size of the first wafer etched after the strong cleaning operation or even more wafers to become larger, affecting the uniformity and reliability of electronic devices.

[0031] Based on this, in order to solve one or more of the above problems, the present disclosure provides a method for improving the first-sheet effect of plasma etching, referring to Figure 2 , Figure 2 A schematic flow chart of a method for improving the first-chip effect of plasma etching provided in an embodiment of the present disclosure, wherein the method comprises the following steps:

[0032] Step S201: performing etching operations on the 1st to Mth wafers in the first batch of wafers, performing cleaning operations on the etching chamber where the first batch of wafers are located, and performing etching operations on the M+1th to Nth wafers in the first batch of wafers.

[0033] Step S202: obtaining a first etching size of a middle etching position and a second etching size of an edge etching position of the Mth wafer, and a third etching size of a middle etching position and a fourth etching size of an edge etching position of the Lth wafer; M+1≤L≤N.

[0034] Step S203: obtaining a first size difference based on the first etching size and the third etching size; and obtaining a second size difference based on the second etching size and the fourth etching size.

[0035] Step S204: Obtain a first relationship model between the etching size of the middle etching position of the etched wafer and the intermediate gas usage and the edge gas usage, and a second relationship model between the etching size of the edge etching position and the intermediate gas usage and the edge gas usage; the intermediate gas usage is the amount of etching gas used when etching the middle etching position of the etched wafer, and the edge gas usage is the amount of etching gas used when etching the edge etching position of the etched wafer.

[0036] Step S205: determining the first gas adjustment amount based on the first size difference and the first relationship model and the second relationship model; and determining the second gas adjustment amount based on the second size difference and the first relationship model and the second relationship model.

[0037] It should be understood that Figure 2 The steps shown in the operation are not exclusive, and other steps may be performed before, after or between any steps in the operation shown; Figure 2 The steps shown in the figure can be adjusted in sequence according to actual needs.

[0038] It should be noted that before executing step S201, the method further includes: providing a first batch of wafers. Here, the first batch of wafers may include multiple wafers, the number of the multiple wafers is greater than N, and the size specifications of the multiple wafers are the same. For example, referring to Figure 3 The wafers are all circular, and their radius R is 150 millimeters (mm).

[0039] The method further includes: defining etching positions in the wafer. The etching positions can be understood as the areas in the wafer that are etched, and the etching positions can include grooves, through holes, etc. of various shapes. Here, the etching positions can be evenly distributed on the wafer. In order to more precisely determine the exact relationship between the etching positions and the gas adjustment amount, the etching positions in different areas of the wafer are divided in the present disclosure, such as middle etching positions and edge etching positions.

[0040] Exemplary, reference Figure 3 , Figure 3 FIG. 3 shows a top view of a wafer on an XY plane; wherein the wafer 300 can be divided into a middle region S1 and an edge region S2, and the edge region S2 surrounds the middle region S1. Figure 3 As shown, the middle area S1 is a circular area formed with the wafer center O as the origin and the first distance R1 as the radius; except for the middle area S1 in the wafer 300, the remaining annular area is the edge area S2, and the width of the edge area S2 is the second distance R2; here, the radius R of the wafer is the sum of the first distance R1 and the second distance R2. Among them, the etching position located in the middle area S1 is the middle etching position; the etching position located in the edge area S2 is the edge etching position.

[0041] In some embodiments, step S201 is performed, and the method further includes: placing the first batch of wafers into a reaction chamber, and performing an etching operation on the first to Mth wafers in the first batch of wafers to form an intermediate etching position and an edge etching position in each etched wafer. The intermediate etching position and the edge etching position of each wafer can be formed in the same etching process. Here, the etching operation may include plasma etching. The first to Mth wafers can be M wafers selected arbitrarily from the first batch of wafers, or they can be M wafers determined according to the arrangement of the wafers.

[0042] In some embodiments, the method further includes: after etching the M wafers in the first batch of wafers, performing a cleaning operation on the reaction chamber. The cleaning operation can discharge byproducts in the reaction chamber.

[0043] In some embodiments, a cleaning gas may be introduced through an air intake unit, and the cleaning gas and byproducts may be discharged from the reaction chamber through an exhaust unit under a low vacuum pressure environment to complete the cleaning operation. A process gas may also be introduced through an air intake unit, and after the process gas reacts with the byproducts, the reactants may be discharged from the reaction chamber through an exhaust unit to complete the cleaning operation. The cleaning operation may also be completed through other adapted units and cleaning processes, which are not limited in this disclosure.

[0044] In some embodiments, the method further includes: after completing the cleaning operation, performing an etching operation on the M+1th to Nth wafers in the first batch of wafers. The etching parameters for the etching operation on the M+1th to Nth wafers are the same as the etching parameters for the etching operation on the 1st to Mth wafers. Here, the M+1th to Nth wafers are not repeated with the 1st to Mth wafers described in the above embodiments.

[0045] Execute step S202 to obtain the first etching size and the second etching size of the Mth wafer in the first batch of wafers, and obtain the third etching size and the fourth etching size of the Lth wafer in the first batch of wafers, where M+1≤L≤N.

[0046] It should be noted that the Mth wafer is the last wafer to be etched before the cleaning operation is performed. The Lth wafer is any wafer from the M+1th to the Nth wafer after the cleaning operation is performed, wherein when L=M+1, the Lth wafer is the first wafer to be etched after the cleaning operation is performed. In some embodiments, the middle etching position and the edge etching position of the Mth wafer and the Lth wafer can be measured by a measuring unit to obtain a first etching size, a second etching size, a third etching size, and a fourth etching size.

[0047] Execute step S203, calculate the difference between the first etching size and the third etching size to obtain the first size difference; calculate the difference between the second etching size and the fourth etching size to obtain the second size difference. It should be understood that the first size difference is the difference between the etching size of the middle etching position of the last etched wafer before the cleaning operation and the etching size of the middle etching position of any etched wafer after the cleaning operation, and the second size difference is the difference between the etching size of the edge etching position of the last etched wafer before the cleaning operation and the etching size of the edge etching position of any etched wafer after the cleaning operation. Among them, when L=M+1, the above size difference is the difference between the etching size of the last etched wafer before the cleaning operation and the etching size of the first etched wafer after the cleaning operation.

[0048] In order to make the obtained first size difference and second size difference more consistent with the actual etching situation, a method of averaging multiple measurements can be used to obtain them; specifically: provide multiple groups of first batch wafers, perform the operations in step S201 and step S202 on the multiple groups of first batch wafers, and then measure the middle etching position and edge etching position of the Mth wafer and the Lth wafer in each group of the first batch wafers of the multiple groups of first batch wafers to obtain the first etching size of the middle etching position of the Mth wafer in the multiple batches of wafers and the second etching size of the edge etching position; and obtain the third etching size of the middle etching position and the fourth etching size of the edge etching position of the Lth wafer in the multiple batches of wafers; then, calculate the difference of multiple first etching sizes and multiple third etching sizes and average them to obtain the first size difference; calculate the difference of multiple second etching sizes and multiple fourth etching sizes and average them to obtain the second size difference.

[0049] Exemplarily, the first etching size of the middle etching position of the Mth wafer in each of the first batch of 5 groups of wafers is obtained, which are 20, 21, 19, 19, and 26 respectively. The third etching size of the middle etching position of the Lth wafer in each of the first batch of 5 groups of wafers is obtained, which are 25, 26, 20, 24, and 22 respectively. By performing difference calculations on the 5 first etching sizes and the 5 third etching sizes respectively, 5 first size differences are obtained, which are 5, 5, 1, 5, and 4 respectively. Then, the 5 first size differences are averaged to obtain the averaged first size difference, which is 4.

[0050] In this way, the problem of inaccurate test data caused by measurement errors of etching dimensions or accidental and random errors in etching operations can be avoided, thereby improving the reliability of test data. In addition, the method of using multiple measurements to find the average value can avoid the situation where the etching dimension value taken deviates far from the true value due to fluctuations in wafer film layers, structures, etc., further improving the authenticity of the measurement.

[0051] Execute step S204 to obtain a first relationship model and a second relationship model, wherein the first relationship model is a relative relationship between the etching size of the middle etching position of the etched wafer and the intermediate gas dosage and the edge gas dosage, and the second relationship model is a relative relationship between the etching size of the edge etching position of the etched wafer and the intermediate gas dosage and the edge gas dosage.

[0052] In the embodiment of the present disclosure, the first relationship model is: Yc=AXc+BXe+C. Formula ①

[0053] The second relationship model is: Ye = DXc + EXe + F. Formula ②

[0054] Among them, Yc is the etching size of the middle etching position of the etched wafer; Ye is the etching size of the edge etching position of the etched wafer; Xc is the intermediate gas usage, that is, the amount of etching gas used when etching the middle etching position of the etched wafer; Xe is the edge gas usage, that is, the amount of etching gas used when etching the edge etching position of the etched wafer; A, B, D and E are coefficient constants corresponding to the etching system where the etching chamber is located; C and F are constants.

[0055] In some embodiments, a first relationship formula is obtained based on a first relationship model: ΔYc=AΔXc+BΔXe; and a second relationship formula is obtained based on a second relationship model: ΔYe=DΔXc+EΔXe; wherein ΔYc is the etching size difference of the middle etching position of the two etched wafers; ΔYe is the etching size difference of the edge etching position of the two etched wafers, ΔXc is the difference in the amount of etching gas used when etching the middle etching position of the two wafers, and ΔXe is the difference in the amount of etching gas used when etching the edge etching position of the two wafers.

[0056] For example, when etching the Mth wafer, the first relationship model is: Yc M =AXc M +BXe M +C, the second relational model is Ye M =DXc M +EXe M +F, when etching the Lth wafer, the first relationship model is: Yc L =AXc L +BXe L +C, the second relational model is Ye L =DXc L +EXe L +F, based on the first relationship model of the Mth wafer and the first relationship model of the Lth wafer, the first relationship is obtained: Yc M -Yc L =(AXc M +BXe M+C)-(AXc L +BXe L +C), which is ΔYc M-L =AΔXc M-L +BΔXe M-L Similarly, the second relationship is: ΔYe M-L =DΔXc M-L +EΔXe M-L .

[0057] Step S205 is executed, that is, when the first size difference and the second size difference have been determined in step S203, the first relational expression and the second relational expression in step S204 are used to obtain the difference in etching gas amount between the Mth wafer in the first batch of wafers and the Lth wafer in the first batch of wafers, that is, the etching gas adjustment amount. Among them, the etching gas adjustment amount corresponding to the middle etching position is the first gas adjustment amount, and the etching gas adjustment amount corresponding to the edge etching position is the second gas adjustment amount.

[0058] In this way, during the etching process of the next batch of wafers, when there is an over-cleaning problem in the etching chamber, the etching gas dosage of the etched wafers after the cleaning operation can be adjusted so that the etching size of the etched wafers after the cleaning operation is the same, consistent or uniform as the etching size of the etched wafers before the cleaning operation.

[0059] It should be noted that the middle etching position and the edge etching position of the same etched wafer are etched at the same time, that is, the etching gas used to etch the middle etching position and the etching gas used to etch the edge etching position are introduced into the etching chamber at the same time. It can also be seen from the above formulas ① and ② that the etching size Yc of the middle etching position of the etched wafer is related to the intermediate gas amount Xc of the etching gas used when etching the middle etching position, and the edge gas amount Xe of the etching gas used when etching the edge etching position; similarly, the etching size Ye of the edge etching position of the etched wafer is related to the intermediate gas amount Xc of the etching gas used when etching the middle etching position, and the edge gas amount Xe of the etching gas used when etching the edge etching position.

[0060] In the embodiment of the present disclosure, an exemplary description is given of how to determine the values ​​of A, B, C, D, E and F in the first relationship model (Formula ①) and the second relationship model (Formula ②).

[0061] In some embodiments, the method specifically includes: etching the middle etching position and the edge etching position of the sample wafer using a sample gas in an etching chamber, and obtaining a first experimental etching size and a second experimental etching size, respectively; obtaining the amount of etching gas used in the sample gas when etching the middle etching position of the sample wafer, and the amount of etching gas used when etching the edge etching position of the sample wafer, to obtain the first experimental gas usage and the second experimental gas usage; based on the first experimental gas usage, the second experimental gas usage, the first experimental middle etching size and the second experimental etching size, as well as the first relationship model and the second relationship model, calculate the coefficient constants A, B, D and E, and the constants C and F.

[0062] Exemplarily, S sample wafers and S groups of etching gases are provided to perform S etchings; each group of etching gases includes an intermediate etching gas and an edge etching gas, and a group of etching gases is used to obtain an intermediate etching position and an edge etching position on the corresponding sample wafer. In other words, S wafers can be etched by S groups of etching gases to obtain S groups of intermediate etching sizes and S groups of edge etching sizes.

[0063] Here, the amount of the intermediate etching gas of group S is Xc1, Xc2, Xc3, ... XcS, and the amount of the edge etching gas of group S is Xe1, Xe2, Xe3, ... XeS. The intermediate etching sizes of group S are Yc1, Yc2, Yc3, ... YcS. The edge etching sizes of group S are Ye1, Ye2, Ye3, ... YeS.

[0064] Next, the amount of etching gas in the middle of group S (i.e. Xc1, Xc2, Xc3, ...XcS), the amount of etching gas at the edge of group S (i.e. Xe1, Xe2, Xe3, ...XeS), the middle etching size of group S (i.e. Yc1, Yc2, Yc3, ...YcS) and the edge etching size of group S (i.e. Ye1, Ye2, Ye3, ...YeS) are respectively substituted into the first relationship model and the second relationship model (i.e. Formula ① and Formula ②), and then, the values ​​of A, B, C, D, E and F can be calculated by the least squares method.

[0065] Exemplarily, taking the first relationship model (Formula ①) as an example, according to the definition of the least squares method, the residual sum of squares Q is:

[0066]

[0067] Wherein, Yi is the etching size of the middle etching position measured during the i-th etching process, and Yci is the middle etching size calculated by substituting the amount of the middle etching gas and the amount of the edge etching gas used in the i-th etching process into the first relationship model (Formula ①). Here, i and S are both integers, and i is less than or equal to S.

[0068] Next, we calculate the partial derivatives of A, B, and C in formula ①:

[0069]

[0070] Wherein, Xci is the amount of the intermediate etching gas used in the i-th etching process, and Xei is the amount of the edge etching gas used in the i-th etching process.

[0071] Then, set the partial derivative to 0 and obtain formula ③.

[0072]

[0073] The residual ε i =Yi-(AXci+BXei+C), based on this, we get formula ④.

[0074]

[0075] Next, we introduce the matrix, let ε = (ε1, ε2, ε3, ...ε S ) T , Y=(Y1,Y2,Y3,...Y S ) T ,

[0076]

[0077] Among them, formula ④ can be expressed as a matrix ε T X=0, and e=Y-XZ, according to these two equations:

[0078] Z=(X T X) -1 X T Y.

[0079] In this way, the coefficient constants A, B and C in the first relationship model (Formula ①) can be obtained. Similarly, the coefficient constants D, E and F in the second relationship model (Formula ②) can be obtained. In other words, by etching, measuring and calculating the formula on the sample wafer, the values ​​of A, B, C, D, E and F can be obtained.

[0080] Based on this, the above method can be used to calculate the difference between the etching gas dosage of the Lth wafer in the first batch of wafers after the cleaning operation and the etching gas dosage of the last etched wafer in the first batch of wafers (i.e., the Mth wafer in the first batch of wafers) before the cleaning operation, i.e., the first gas adjustment amount and the second gas adjustment amount. It should be understood that M+1≤L≤N, i.e., L can include one or more values, wherein when L corresponds to multiple values, the first gas adjustment amount and the second gas adjustment amount also correspond to multiple groups. In other words, the above method can be used to obtain the first gas adjustment amount and the second gas adjustment amount corresponding to each wafer in the M+1 to Nth wafers in the first batch of wafers.

[0081] Exemplary, reference Figure 4 Through the above calculation, the number of wafers from the M+1th to the Nth wafers in the first batch after the cleaning operation (such as Figure 4 The gas amounts that need to be adjusted for the middle etching positions and edge etching positions of the 1st, 2nd, ... gth etched wafers (shown in the figure) are g first gas adjustment amounts, respectively: ΔXc1, ΔXc2, ...ΔXcg; the g second gas adjustment amounts, respectively: ΔXe1, ΔXe2, ...ΔXeg; that is, the corresponding g groups of first gas adjustment amounts and second gas adjustment amounts (ΔXc1, ΔXe1), (ΔXc2, ΔXe2) ... (ΔXcg, ΔXeg).

[0082] In some embodiments, the method also includes: determining whether the values ​​of the first size difference and the second size difference are less than preset values; wherein, when the values ​​of the first size difference and the second size difference are both less than the preset values, determining that the first gas adjustment amount and the second gas adjustment amount corresponding to the Lth wafer in the first batch of wafers are both 0 or are negligible.

[0083] It should be understood that when the values ​​of the first size difference and the second size difference are both less than the preset value, it indicates that the difference between the etching size of the last wafer before the cleaning operation in the first batch of wafers and the etching size of the Nth wafer after the cleaning operation is small, and the difference is within the preset range, and the impact on the performance of the semiconductor device can be ignored. Based on this, when etching the second batch of wafers, in order to prevent the influence of the cleaning operation on the etching size, the etching gas consumption of the last etched wafer before the cleaning operation in the second batch of wafers and the gas adjustment amount of the corresponding wafer after the cleaning operation in the first batch of wafers in the above embodiment can be obtained to determine the etching gas consumption of the corresponding wafer to be etched after the cleaning operation in the second batch of wafers, thereby improving the change of the etching size and reducing the influence of excessive cleaning on the etching size.

[0084] Here, the number of the first batch of wafers is the same as that of the second batch of wafers, and the etching operation can be performed on multiple wafers in the second batch of wafers according to step S201, and the etching procedures and etching parameters of the two are the same. In other words, the etching process of the second batch of wafers can specifically include: etching the 1st to Mth wafers in the second batch of wafers, then cleaning the etching chamber where the second batch of wafers are located, and then continuing to etch the M+1th to Nth wafers in the second batch of wafers.

[0085] In some embodiments, the method further includes: obtaining the first gas usage and the second gas usage when etching the Mth wafer in the second batch of wafers; the first gas usage is the amount of etching gas used when etching the middle etching position of the Mth wafer in the second batch of wafers, and the second gas usage is the amount of etching gas used when etching the edge etching position of the Mth wafer in the second batch of wafers. Here, the Mth wafer in the second batch of wafers is the last etched wafer before the cleaning operation is performed in the second batch of wafers. The first gas usage and the second gas usage are the etching gas usage corresponding to the last etched wafer before the cleaning operation is performed in the second batch of wafers.

[0086] Based on the first gas usage and the first gas adjustment amount, the amount of etching gas used at the middle etching position of the Lth wafer in the second batch of wafers when the etching operation is performed on the Lth wafer in the second batch of wafers is determined; and based on the second gas usage and the second gas adjustment amount, the amount of etching gas used at the edge etching position of the Lth wafer in the second batch of wafers when the etching operation is performed on the Lth wafer in the second batch of wafers is determined.

[0087] The amount of etching gas used in etching the middle etching position of the Lth wafer in the second batch of wafers is the sum of the first gas amount and the first gas adjustment amount; the amount of etching gas used in etching the edge etching position of the Lth wafer in the second batch of wafers is the sum of the second gas amount and the second gas adjustment amount. Here, M+1≤L≤N.

[0088] That is to say, the etching gas dosage of the Lth wafer in the second batch of wafers is the sum of the etching gas dosage of the Mth wafer in the second batch of wafers and the etching gas adjustment amount corresponding to the Lth wafer in the first batch of wafers obtained in the above-mentioned embodiment. In this way, the etching gas dosage of the etched wafer after over-cleaning can be adjusted according to the actual environment in the reaction chamber, so that the etching size of the etched wafer after over-cleaning is consistent with the etching size of the etched wafer before the cleaning operation; improve the consistency and uniformity of the wafer etching size.

[0089] It should be noted that, in the aforementioned embodiment, when the first gas adjustment amount and the second gas adjustment amount corresponding to the Lth wafer in the first batch of wafers are determined to be 0 or both negligible, when etching the Lth wafer in the second batch of wafers, the etching gas will no longer be adjusted, that is, when etching the Lth to the last wafer in the second batch of wafers, the amount of etching gas used is the same as the amount of etching gas used when etching the Mth wafer in the second batch of wafers. For example, refer to Figure 4 When etching the second batch of wafers, there is no need to adjust the etching gas dosage from the g-th wafer after the cleaning operation to the last wafer being etched, that is, the etching gas dosage remains the same as that of the M-th wafer being etched in the second batch of wafers.

[0090] In some embodiments, the etching gas may be a single gas, such as one of oxygen (O2), carbon tetrafluoride (CF4) and octafluorocyclobutane (C4F8). Figure 4 According to different etching gases, the etching gas adjustment amount corresponding to the first etched wafer to the g-1th etched wafer can be gradually reduced or gradually increased.

[0091] Based on this, in the embodiments of the present disclosure, the first-wafer effect in plasma etching can be effectively improved, the impact of excessive cleaning on the plasma etching process can be reduced, the etching accuracy and stability can be improved, the uniformity of the etching positions in the etched wafer can be improved, and at the same time the production cost and defective product rate can be reduced.

[0092] Based on the above method for improving the first-chip effect of plasma etching, the embodiment of the present disclosure also provides a device for improving the first-chip effect of plasma etching, wherein, with reference to Figure 5 , the device 500 comprises:

[0093] The reaction unit 501 is configured to: perform etching operations on the 1st to Mth wafers in the first batch of wafers, perform cleaning operations on the etching chamber where the first batch of wafers are located, and perform etching operations on the M+1th to Nth wafers in the first batch of wafers.

[0094] The acquisition unit 502 is configured to: acquire the first etching size of the middle etching position and the second etching size of the edge etching position of the Mth wafer in the first batch of wafers, and the third etching size of the middle etching position and the fourth etching size of the edge etching position of the Lth wafer in the first batch of wafers; M+1≤L≤N.

[0095] The calculation unit 503 is configured to: obtain a first size difference based on the first etching size and the third etching size; and obtain a second size difference based on the second etching size and the fourth etching size.

[0096] The acquisition unit 502 is also configured to: acquire a first relationship model between the etching size of the middle etching position of the etched wafer and the intermediate gas usage, the edge gas usage, and a second relationship model between the etching size of the edge etching position and the intermediate gas usage, the edge gas usage; the intermediate gas usage is the amount of etching gas used when etching the middle etching position of the etched wafer, and the edge gas usage is the amount of etching gas used when etching the edge etching position of the etched wafer.

[0097] The determination unit 504 is configured to: determine the first gas adjustment amount based on the first size difference and the first relationship model and the second relationship model; and determine the second gas adjustment amount based on the second size difference and the first relationship model and the second relationship model.

[0098] In some embodiments, the acquisition unit 502 is further configured to: obtain the first gas usage and the second gas usage when etching the Mth wafer in the second batch of wafers; the first gas usage is the amount of etching gas used when etching the middle etching position of the Mth wafer in the second batch of wafers, and the second gas usage is the amount of etching gas used when etching the edge etching position of the Mth wafer in the second batch of wafers.

[0099] The determination unit 504 is also configured to: determine, based on the first gas usage and the first gas adjustment amount, the amount of etching gas used to etch the middle etching position of the Lth wafer in the second batch of wafers when performing an etching operation on the Lth wafer in the second batch of wafers; and determine, based on the second gas usage and the second gas adjustment amount, the amount of etching gas used to etch the edge etching position of the Lth wafer in the second batch of wafers when performing an etching operation on the Lth wafer in the second batch of wafers.

[0100] In some embodiments, the device also includes: a judgment unit, configured to: judge whether the values ​​of the first size difference and the second size difference are less than a preset value; wherein, when the values ​​of the first size difference and the second size difference are both less than the preset value, it is determined that when etching the Lth to last wafers in the second batch of wafers, the amount of etching gas used is the same as the amount of etching gas used to etch the Mth wafer in the second batch of wafers.

[0101] In some embodiments, the reaction unit 501 is further configured to: etch the middle etching position and the edge etching position of the sample wafer using the sample gas in the etching chamber, and obtain a first experimental etching size and a second experimental etching size respectively.

[0102] The acquisition unit 502 is also configured to: acquire the amount of etching gas used in the sample gas when etching the middle etching position of the sample wafer, and the amount of etching gas used when etching the edge etching position of the sample wafer, so as to obtain the first experimental gas usage and the second experimental gas usage.

[0103] The calculation unit 503 is also configured to calculate coefficient constants A, B, D and E, and constants C and F based on the first experimental gas dosage, the second experimental gas dosage, the first experimental etching size and the second experimental etching size, and the first relationship model and the second relationship model.

[0104] In some embodiments, the acquisition unit 502 is specifically configured to: acquire a first etching size of a middle etching position of multiple M-th wafers and a second etching size of an edge etching position; and acquire a third etching size of a middle etching position of multiple L-th wafers and a fourth etching size of an edge etching position.

[0105] The calculation unit 503 is specifically configured to: calculate the difference between the multiple first etching dimensions and the multiple third etching dimensions and average them to obtain a first dimension difference; calculate the difference between the multiple second etching dimensions and the multiple fourth etching dimensions and average them to obtain a second dimension difference.

[0106] It should be noted that: "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. In addition, the technical solutions recorded in the embodiments of the present disclosure can be combined arbitrarily without conflict.

[0107] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the protection scope of the present disclosure.

Claims

1. A method for improving the first-chip effect of plasma etching, characterized in that: The method comprises: Performing an etching operation on the 1st to Mth wafers in the first batch of wafers, performing a cleaning operation on the etching chamber where the first batch of wafers are located, and performing the etching operation on the M+1th to Nth wafers in the first batch of wafers; Obtaining a first etching size of a middle etching position of the Mth wafer and a second etching size of an edge etching position, as well as a third etching size of a middle etching position of the Lth wafer and a fourth etching size of an edge etching position; M+1≤L≤N; Obtaining a first size difference based on the first etching size and the third etching size; and obtaining a second size difference based on the second etching size and the fourth etching size; Obtaining a first relationship model between the etching size of the middle etching position of the etched wafer and the intermediate gas usage and the edge gas usage, and a second relationship model between the etching size of the edge etching position and the intermediate gas usage and the edge gas usage; the intermediate gas usage is the amount of etching gas used when etching the middle etching position of the etched wafer, and the edge gas usage is the amount of etching gas used when etching the edge etching position of the etched wafer; A first gas adjustment amount is determined based on the first size difference and the first relationship model and the second relationship model; and a second gas adjustment amount is determined based on the second size difference and the first relationship model and the second relationship model.

2. The method according to claim 1, characterized in that The method further comprises: Obtaining the first gas usage and the second gas usage when etching the Mth wafer in the second batch of wafers; the first gas usage is the amount of etching gas used when etching the middle etching position of the Mth wafer in the second batch of wafers, and the second gas usage is the amount of etching gas used when etching the edge etching position of the Mth wafer in the second batch of wafers; Determining, based on the first gas usage amount and the first gas adjustment amount, an amount of etching gas used at a middle etching position of the Lth wafer in the second batch of wafers when performing the etching operation on the Lth wafer in the second batch of wafers; and Based on the second gas usage and the second gas adjustment amount, the amount of etching gas used at the edge etching position of the Lth wafer in the second batch of wafers when performing an etching operation on the Lth wafer in the second batch of wafers is determined.

3. The method according to claim 2, characterized in that The amount of etching gas used in etching the middle etching position of the Lth wafer in the second batch of wafers is the sum of the first gas usage and the first gas adjustment amount; The amount of etching gas used to etch the edge etching position of the Lth wafer in the second batch of wafers is the sum of the second gas usage and the second gas adjustment amount.

4. The method according to claim 3, characterized in that The method further comprises: Determine whether the first size difference and the second size difference are less than a preset value; Among them, when the values ​​of the first size difference and the second size difference are both smaller than the preset value, it is determined that the amount of etching gas used when etching the Lth to last wafer in the second batch of wafers is the same as the amount of etching gas used when etching the Mth wafer in the second batch of wafers.

5. The method according to claim 1, characterized in that: The first relationship model is: Yc=AXc+BXe+C; the second relationship model is: Ye=DXc+EXe+F; Among them, Yc is the etching size of the middle etching position of the etched wafer; Ye is the etching size of the edge etching position of the etched wafer; Xc is the amount of the intermediate gas; Xe is the amount of the edge gas; A, B, D and E are coefficient constants corresponding to the etching system where the etching chamber is located; C and F are constants.

6. The method according to claim 5, characterized in that The method further comprises: Based on the first relationship model, a first relationship is obtained: ΔYc=AΔXc+BΔXe; and based on the second relationship model, a second relationship is obtained: ΔYe=DΔXc+EΔXe; wherein ΔYc is the etching size difference of the middle etching position of the two etched wafers; ΔYe is the etching size difference of the edge etching position of the two etched wafers, ΔXc is the difference in the amount of etching gas used when etching the middle etching position of the two wafers, and ΔXe is the difference in the amount of etching gas used when etching the edge etching position of the two wafers; The first gas adjustment amount and the second gas adjustment amount are calculated based on the first size difference, the second size difference, the first relationship, and the second relationship.

7. The method according to claim 5, characterized in that The method further comprises: Etching a middle etching position and an edge etching position of a sample wafer in the etching chamber using the sample gas, and obtaining a first experimental etching size and a second experimental etching size respectively; Obtaining the amount of etching gas used in the sample gas when etching the middle etching position of the sample wafer and the amount of etching gas used when etching the edge etching position of the sample wafer to obtain the first experimental gas usage and the second experimental gas usage; Based on the first experimental gas dosage, the second experimental gas dosage, the first experimental etching size, the second experimental etching size, and the first relationship model and the second relationship model, coefficient constants A, B, D and E, and constants C and F are calculated.

8. The method according to claim 1, characterized in that: The first size difference is obtained based on the first etching size and the third etching size; And, obtaining a second size difference based on the second etching size and the fourth etching size, comprising: Obtaining a first etching size corresponding to a middle etching position of an M-th wafer in a plurality of wafer batches and a second etching size corresponding to an edge etching position; and obtaining a third etching size of a middle etching position of an L-th wafer in a plurality of wafer batches and a fourth etching size of an edge etching position; Calculating the difference between a plurality of the first etching dimensions and a plurality of the third etching dimensions and averaging the difference to obtain the first dimension difference; Differences of the plurality of second etching dimensions and the plurality of fourth etching dimensions are calculated and averaged to obtain the second dimension difference.

9. The method according to claim 1, characterized in that: The etching gas used in the etching operation includes one of oxygen, carbon tetrafluoride and octafluorocyclobutane.

10. A device for improving the first-chip effect of plasma etching, characterized in that: The device comprises: A reaction unit is configured to: perform an etching operation on the 1st to Mth wafers in the first batch of wafers, perform a cleaning operation on the etching chamber where the first batch of wafers are located, and perform the etching operation on the M+1th to Nth wafers in the first batch of wafers; An acquisition unit is configured to: acquire a first etching size of a middle etching position and a second etching size of an edge etching position of the Mth wafer, and a third etching size of a middle etching position and a fourth etching size of an edge etching position of the Lth wafer; M+1≤L≤N; A calculation unit configured to: obtain a first size difference based on the first etching size and the third etching size; and obtain a second size difference based on the second etching size and the fourth etching size; The acquisition unit is further configured to: acquire a first relationship model between the etching size of the middle etching position of the etched wafer and the intermediate gas usage and the edge gas usage, and a second relationship model between the etching size of the edge etching position and the intermediate gas usage and the edge gas usage; the intermediate gas usage is the amount of etching gas used when etching the middle etching position of the etched wafer, and the edge gas usage is the amount of etching gas used when etching the edge etching position of the etched wafer; The determination unit is configured to: determine a first gas adjustment amount based on the first size difference and the first relationship model and the second relationship model; and determine a second gas adjustment amount based on the second size difference and the first relationship model and the second relationship model.

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