Method for measuring etching selection ratio

Abstract

The invention provides a method for measuring an etching selection ratio, which comprises the following steps of: providing a substrate, and sequentially forming a second material layer and a first material layer with set thickness on the substrate; etching the first material layer, and collecting the intensity value etching time of a spectral signal of an etching reactant or product; secondary etching is carried out on the second material layer, and the intensity value of a spectral signal of an etching reactant or product is collected to obtain etching time; and calculating the etching selection ratio of the first material layer to the second material layer according to the thickness and the etching time of the first material layer and the thickness and the etching time of the second material layer. According to the method, the etching rate of the film layer is accurately obtained by setting the thickness of the material layer and measuring the etching time, so that the etching selection ratio can be accurately and quickly obtained, the measurement accuracy of the etching selection ratio is improved, the measurement time and the reset time of measurement equipment are reduced, the utilization rate of the measurement equipment is further improved, and the measurement efficiency is improved. And meanwhile, the use of measurement wafers is reduced, and the cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a method for measuring an etching selectivity ratio. Background Art

[0002] In semiconductor manufacturing, the sidewall spacer process is a critical process. Sidewall spacers typically consist of a stacked structure of silicon nitride and silicon oxide. The etch selectivity ratio between silicon nitride and silicon oxide is a key parameter in dry etching sidewall spacers. A change in this etch selectivity can impact product yield. For example, a low etch selectivity can easily lead to over-etching, which can cause device failure. Therefore, being able to accurately and quickly measure this etch selectivity is crucial.

[0003] The current method for measuring the etching selectivity is to measure the thickness of the silicon nitride and silicon oxide films before etching, then perform etching, and then measure the thickness of the silicon nitride and silicon oxide films after etching. The etching rate is calculated based on the etched film layer and the time in the etching recipe. However, this method is susceptible to film measurement errors. For example, films such as silicon nitride and silicon oxide are easily affected by the measurement waiting time and the environment. The film thickness is often not accurate enough, resulting in the inability to accurately measure the etching selectivity. In addition, the etching rates of silicon nitride and silicon oxide need to be measured separately, and the measurement time is relatively long, which affects the process equipment and measurement utilization rate, affecting production capacity. At the same time, separate measurement also increases the cost of using the measurement wafer. Summary of the Invention

[0004] The object of the present invention is to provide a method for measuring an etching selectivity ratio, which can accurately and quickly measure the etching selectivity ratio, thereby improving the utilization rate of the measuring equipment, while reducing the use of measuring wafers and saving costs.

[0005] To solve the above technical problems, the present invention provides a method for measuring etching selectivity, comprising the following steps:

[0006] Providing a substrate, and sequentially forming a second material layer and a first material layer of a predetermined thickness on the substrate;

[0007] Performing a first etching on the first material layer until the second material layer is exposed, collecting intensity values ​​of spectral signals of etching reactants or products, and determining the start and end times of etching based on changes in the intensity values, thereby obtaining an etching time for the first material layer;

[0008] Performing a second etching on the second material layer until the substrate is exposed, collecting intensity values ​​of spectral signals of etching reactants or products, and determining the start and end times of etching based on changes in the intensity values, thereby obtaining an etching time for the second material layer; and

[0009] The etching selectivity ratio between the first material layer and the second material layer is calculated according to the thickness and etching time of the first material layer and the thickness and etching time of the second material layer.

[0010] Optionally, a third material layer is further formed between the substrate and the second material layer to serve as an etch stop layer for the second material layer, and the second etching exposes the third material layer.

[0011] Optionally, the first material layer includes a silicon nitride layer, the second material layer includes a silicon oxide layer, and the third material layer includes a silicon nitride layer.

[0012] Optionally, during the first etching, the intensity value of the spectrum signal of the etching product CN is collected.

[0013] Optionally, during the second etching, the intensity value of the spectrum signal of the etching product CO is collected.

[0014] Optionally, the intensity value of the spectral signal of the product includes a rising phase, a stable phase and a falling phase, wherein the moment of transition from the rising phase to the stable phase is taken as the starting moment of etching, and the moment of transition from the stable phase to the falling phase is taken as the ending moment of etching.

[0015] Optionally, an etching endpoint detection device is used to collect the intensity value of the spectral signal of the etching reactant or product.

[0016] Optionally, both the first etching and the second etching are dry etching.

[0017] Optionally, the etching conditions of the first etching and the second etching are the same.

[0018] Optionally, the method of calculating the etching selectivity ratio of the first material layer to the second material layer according to the thickness and etching time of the first material layer and the thickness and etching time of the second material layer includes:

[0019] Obtaining an etching rate of the first material layer according to the thickness of the first material layer and the etching time of the first material layer;

[0020] Obtaining an etching rate of the second material layer according to the thickness of the second material layer and the etching time of the second material layer; and

[0021] An etching selectivity ratio between the first material layer and the second material layer is obtained according to the etching rate of the first material layer and the etching rate of the second material layer.

[0022] To sum up, in the method for measuring the etching selectivity provided by the present invention, a second material layer and a first material layer of a set thickness are first formed on a substrate, and then the first material layer is etched for the first time to expose the second material layer, and the intensity value of the spectral signal of the etching reactant or product is collected, and the start and end times of etching are determined according to the change in the intensity value, thereby obtaining the etching time of the first material layer, and then the second material layer is etched for a second time to expose the substrate, and the intensity value of the spectral signal of the etching reactant or product is collected, and the start and end times of etching are determined according to the change in the intensity value, thereby obtaining the etching time of the second material layer, and then the etching selectivity of the first material layer and the second material layer is calculated according to the thickness and etching time of the first material layer and the thickness and etching time of the second material layer. The present invention forms different material layers of set thickness on a substrate in sequence, etches the different material layers in sequence, calculates the etching time of the different material layers by collecting the intensity values ​​of the spectral signals of the etching reactants or products of the different material layers, and accurately obtains the etching rate of the film layer by setting the thickness of the material layer and measuring the etching time, so as to accurately and quickly obtain the etching selectivity, improve the measurement accuracy of the etching selectivity, reduce the measurement time and the restart time of the measuring equipment, thereby improving the utilization rate of the measuring equipment, and reducing the use of measurement wafers, saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of a method for measuring etching selectivity provided by one embodiment of the present invention.

[0024] Figure 2 1 is a schematic structural diagram of a substrate before etching provided by one embodiment of the present invention.

[0025] Figure 3 Schematic diagram of a characteristic curve showing the variation of the intensity value of the spectral signal of CN with time, provided by one embodiment of the present invention.

[0026] Figure 4 Schematic diagram of a characteristic curve showing the intensity value of a CO spectral signal changing with time, provided by one embodiment of the present invention.

[0027] Description of reference numerals:

[0028] 10 - substrate; 11 - first material layer; 12 - second material layer; 13 - third material layer. DETAILED DESCRIPTION

[0029] To make the objects, advantages, and features of the present invention more clearly apparent, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale. They are only used to conveniently and clearly assist in illustrating the purposes of the embodiments of the present invention. In addition, the structures shown in the drawings are often part of the actual structure. In particular, different drawings may need to illustrate different focuses and sometimes use different scales.

[0030] As used in the present invention, the singular forms "a", "an" and "the" include plural objects, unless the content clearly indicates otherwise. As used in the present invention, the term "or" is generally used in a sense including "and / or", unless the content clearly indicates otherwise. As used in the present invention, the term "several" is generally used in a sense including "at least one", unless the content clearly indicates otherwise. As used in the present invention, the term "at least two" is generally used in a sense including "two or more", unless the content clearly indicates otherwise. In addition, the terms "first", "second" and "third" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" and "third" may explicitly or implicitly include one or at least two of the features, unless the content clearly indicates otherwise.

[0031] Figure 1 FIG. 1 is a flow chart of a method for measuring etching selectivity according to an embodiment of the present invention. Figure 1 As shown, the method for measuring the etching selectivity includes the following steps:

[0032] S1: providing a substrate, and sequentially forming a second material layer and a first material layer of a predetermined thickness on the substrate;

[0033] S2: performing a first etching on the first material layer until the second material layer is exposed, collecting the intensity value of the spectral signal of the etching reactant or product, and determining the start and end times of the etching based on the change in the intensity value, thereby obtaining the etching time of the first material layer;

[0034] S3: etching the second material layer for a second time until the substrate is exposed, collecting the intensity value of the spectral signal of the etching reactant or product, and determining the start and end times of the etching according to the change of the intensity value, thereby obtaining the etching time of the second material layer; and

[0035] S4: Calculating an etching selectivity ratio between the first material layer and the second material layer according to the thickness and etching time of the first material layer and the thickness and etching time of the second material layer.

[0036] Figure 2 FIG. 1 is a schematic diagram of the structure of the substrate before etching provided by an embodiment of the present invention. Figure 1 and Figure 2 The method for measuring the etching selectivity provided by the embodiment of the present invention is described in detail.

[0037] In step S1, please refer to Figure 2 As shown, a substrate 10 is provided, and a second material layer 12 and a first material layer 11 with a set thickness are sequentially formed on the substrate 10 .

[0038] In this embodiment, the substrate 10 may be made of silicon, germanium, silicon germanium, silicon carbide, gallium arsenide, or indium gallium, or may be silicon-on-insulator (SOI) or germanium-on-insulator (GOI). Alternatively, the substrate 10 may be made of other materials, such as III-V compounds such as gallium arsenide. The substrate 10 can be reused as a measurement wafer.

[0039] A second material layer 12 and a first material layer 11 of a predetermined thickness are sequentially formed on the substrate 10. In this embodiment, the etching selectivity ratio of the second material layer 12 to the first material layer 11 is measured. The materials of the first material layer 11 and the second material layer 12 can be any materials for which the etching selectivity ratio needs to be measured.

[0040] Before forming the second material layer 12 on the substrate 10, a third material layer 13 may be formed on the substrate 10. The third material layer 13 may serve as an etch-stop layer for the second material layer 12, while the second material layer 12 serves as an etch-stop layer for the first material layer 11. In one embodiment of the present invention, the material of the third material layer 13 may be the same as that of the first material layer 11.

[0041] In one embodiment of the present invention, the second material layer 12 is a silicon oxide layer, and the first material layer 11 and the third material layer 13 are silicon nitride layers. A silicon nitride layer, a silicon oxide layer, and a silicon nitride layer are sequentially formed on the substrate 10 to a predetermined thickness, and an etching selectivity ratio between the silicon nitride layer and the silicon oxide layer can be subsequently obtained.

[0042] For example, the thickness of the first material layer 11 is set to THK1, and the thickness of the second material layer 12 is set to THK2. The specific thicknesses can be determined according to actual needs. The third material layer 13 is used as an etch stop layer, and its thickness can be less than the thicknesses of the first material layer 11 and the second material layer 12. It can also be determined according to actual conditions.

[0043] In step S2, the first material layer 11 is etched for the first time until the second material layer 12 is exposed, and the intensity value of the spectral signal of the etching reactant or product is collected. The start and end times of the etching are determined according to the change in the intensity value, thereby obtaining the etching time of the first material layer 11.

[0044] In this embodiment, a dry etching process is used to perform a first etching on the first material layer 11 , and the second material layer 12 serves as an etching stop layer.

[0045] During the etching process, an etching endpoint detection device is used to collect the intensity value of the spectral signal of the etching reactant or product in real time, and the start and end times of the etching are determined according to the change of the intensity value, thereby obtaining the etching time of the first material layer 11.

[0046] In one embodiment of the present invention, the material of the first material layer 11 is silicon nitride (Si3N4), the etching gas used is CF4, the reaction chemical formula is Si3N4(s)+CF4(g)→SiF4(g)+CN(g), where s represents solid, g represents gas, and the etching products are SiF4 and CN. In this embodiment, the intensity value of the spectral signal of the etching product CN is collected.

[0047] Figure 3 This is a schematic diagram of a characteristic curve of the intensity value of the spectral signal of CN provided by an embodiment of the present invention as a function of time. Figure 3 As shown, the intensity value of the spectral signal of CN includes a rising stage D1, a stable stage D2 and a falling stage D3, wherein the moment of transition from the rising stage D1 to the stable stage D2 is taken as the starting moment t1 of etching, and the moment of transition from the stable stage D2 to the falling stage D3 is taken as the ending moment t2 of etching, thereby obtaining the etching time △T1=t2-t1 of the first material layer 11.

[0048] In step S3, the second material layer 12 is etched for the second time until the substrate 10 is exposed (in this embodiment, specifically, the third material layer 13 is exposed), and the intensity value of the spectral signal of the etching reactant or product is collected. The start and end times of the etching are determined according to the change in the intensity value, thereby obtaining the etching time of the second material layer 12.

[0049] In this embodiment, a dry etching process is used to perform a second etching on the second material layer 12, and the third material layer 13 serves as an etching stop layer. The etching process conditions of the second etching are the same as those of the first etching.

[0050] During the etching process, an etching endpoint detection device is used to collect the intensity value of the spectral signal of the etching reactant or product in real time, and the start and end times of the etching are determined according to the change of the intensity value, thereby obtaining the etching time of the second material layer 12.

[0051] In one embodiment of the present invention, the material of the second material layer 12 is silicon oxide (SiO2), the etching gas used is CF4, the reaction chemical formula is SiO2(s)+CF4(g)→SiF4(g)+CO(g), where s represents solid, g represents gas, and the etching products are SiF4 and CO. In this embodiment, the intensity value of the spectral signal of the etching product CO is collected.

[0052] Figure 4 This is a schematic diagram of a characteristic curve of the intensity value of the CO spectral signal changing with time provided by an embodiment of the present invention. Please refer to Figure 4 As shown, the intensity value of the spectral signal of CO includes a rising stage D1, a stable stage D2 and a falling stage D3, wherein the moment when the rising stage D1 turns to the stable stage D2 is taken as the starting moment t1 of etching, and the moment when the stable stage D2 turns to the falling stage D3 is taken as the ending moment t2 of etching, thereby obtaining the etching time ΔT2=t2-t1 of the second material layer 12.

[0053] In step S4 , the etching selectivity ratio of the first material layer 11 to the second material layer 12 is calculated based on the thickness and etching time of the first material layer 11 and the thickness and etching time of the second material layer 12 .

[0054] Specifically, the etching rate of the first material layer 11 is obtained according to the thickness of the first material layer 11 and the etching time of the first material layer 11. The thickness of the first material layer 11 is THK1, the etching time of the first material layer 11 is ΔT1, and the etching rate of the first material layer 11 is v1=THK1 / ΔT1.

[0055] The etching rate of the second material layer 12 is obtained according to the thickness of the second material layer 12 and the etching time of the second material layer 12. The thickness of the second material layer 12 is THK2, the etching time of the second material layer 12 is ΔT2, and the etching rate of the second material layer 12 is v2=THK2 / ΔT2.

[0056] The etching selectivity ratio of the first material layer 11 to the second material layer 12 is obtained according to the etching rates of the first material layer 11 and the second material layer 12. The etching rate of the first material layer 11 is v1, the etching rate of the second material layer 12 is v2, and the etching selectivity ratio of the first material layer 11 to the second material layer 12 is v1 / v2.

[0057] In this embodiment, the thickness of the first material layer 11 and the second material layer 12 is a pre-set thickness. According to the set thickness, the second material layer 12 and the first material layer 11 are formed on the substrate 10 respectively, and then the second material layer 12 and the first material layer 11 are etched in sequence. During the etching process, the intensity value of the spectral signal of the etching reactant or product is collected, and the start time and the end time of the etching are determined according to the change of the intensity value, thereby obtaining the etching time. This method can obtain a relatively accurate etching time. The film thickness is fixed and the etching time is relatively accurate, so the etching rate can be accurately obtained, thereby obtaining a relatively accurate etching selectivity. At the same time, since the second material layer 12 and the first material layer 11 are formed in sequence and etched in sequence, there is no need to form the material layers separately and measure them separately as in the prior art, and only the etching time needs to be measured, which can greatly reduce the required measurement time. Therefore, by adopting the etching selectivity measurement method described in the present invention, the etching selectivity can be obtained accurately and quickly, thereby improving the accuracy of the etching selectivity measurement, reducing the measurement time and the recovery time of the measuring equipment, thereby improving the utilization rate of the measuring equipment, and reducing the use of measuring wafers, saving costs.

[0058] In one embodiment of the present invention, after sequentially forming a second material layer and a first material layer of a predetermined thickness on the substrate, a second material layer and a first material layer may be further formed on the first material layer, i.e., a stacked structure of the second material layer and the first material layer is formed on the substrate. The stacked structure may include two, three, or more second material layers and first material layers, and all first material layers and second material layers in the stacked structure have the same thickness. Subsequently, etching is performed from the topmost first material layer to finally expose the substrate. After obtaining the etching time for each layer using the same method as described above, the average etching time for the first material layer and the average etching time for the second material layer can be obtained, thereby obtaining a relatively accurate etching selectivity.

[0059] To sum up, in the method for measuring the etching selectivity provided by the present invention, a second material layer and a first material layer of a set thickness are first formed on a substrate, and then the first material layer is etched for the first time to expose the second material layer, and the intensity value of the spectral signal of the etching reactant or product is collected, and the start and end times of etching are determined according to the change in the intensity value, thereby obtaining the etching time of the first material layer, and then the second material layer is etched for a second time to expose the substrate, and the intensity value of the spectral signal of the etching reactant or product is collected, and the start and end times of etching are determined according to the change in the intensity value, thereby obtaining the etching time of the second material layer, and then the etching selectivity of the first material layer and the second material layer is calculated according to the thickness and etching time of the first material layer and the thickness and etching time of the second material layer. The present invention forms different material layers of set thickness on a substrate in sequence, etches the different material layers in sequence, calculates the etching time of the different material layers by collecting the intensity values ​​of the spectral signals of the etching reactants or products of the different material layers, and accurately obtains the etching rate of the film layer by setting the thickness of the material layer and measuring the etching time, so as to accurately and quickly obtain the etching selectivity, improve the measurement accuracy of the etching selectivity, reduce the measurement time and the restart time of the measuring equipment, thereby improving the utilization rate of the measuring equipment, and reducing the use of measurement wafers, saving costs.

[0060] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for measuring etching selectivity, characterized in that: The following steps are involved: Providing a substrate, and sequentially forming a second material layer and a first material layer of a predetermined thickness on the substrate; Performing a first etching on the first material layer until the second material layer is exposed, collecting intensity values ​​of spectral signals of etching reactants or products, and determining the start and end times of etching based on changes in the intensity values, thereby obtaining an etching time for the first material layer; Performing a second etching on the second material layer until the substrate is exposed, collecting intensity values ​​of spectral signals of etching reactants or products, and determining the start and end times of etching based on changes in the intensity values, thereby obtaining an etching time for the second material layer; as well as The etching selectivity ratio between the first material layer and the second material layer is calculated according to the thickness and etching time of the first material layer and the thickness and etching time of the second material layer.

2. The method for measuring etching selectivity according to claim 1, wherein: A third material layer is further formed between the substrate and the second material layer to serve as an etching stop layer for the second material layer. The second etching exposes the third material layer.

3. The method for measuring etching selectivity according to claim 2, wherein: The first material layer includes a silicon nitride layer, the second material layer includes a silicon oxide layer, and the third material layer includes a silicon nitride layer.

4. The method for measuring etching selectivity according to claim 3, wherein: During the first etching, the intensity value of the spectrum signal of the etching product CN is collected.

5. The method for measuring etching selectivity according to claim 3, wherein: During the second etching, the intensity value of the spectrum signal of the etching product CO is collected.

6. The method for measuring etching selectivity according to claim 4 or 5, characterized in that: The intensity value of the spectral signal of the product includes a rising stage, a stable stage and a falling stage, wherein the moment from the rising stage to the stable stage is regarded as the starting moment of etching, and the moment from the stable stage to the falling stage is regarded as the ending moment of etching.

7. The method for measuring the etching selectivity according to any one of claims 1 to 5, characterized in that: An etching endpoint detection device is used to collect the intensity value of the spectrum signal of the etching reactant or product.

8. The method for measuring the etching selectivity according to any one of claims 1 to 5, characterized in that: The first etching and the second etching are both dry etching.

9. The method for measuring the etching selectivity according to any one of claims 1 to 5, characterized in that: The etching conditions of the first etching and the second etching are the same.

10. The method for measuring etching selectivity according to any one of claims 1 to 5, characterized in that: The method for calculating the etching selectivity ratio between the first material layer and the second material layer according to the thickness and etching time of the first material layer and the thickness and etching time of the second material layer includes: Obtaining an etching rate of the first material layer according to the thickness of the first material layer and the etching time of the first material layer; Obtaining an etching rate of the second material layer according to the thickness of the second material layer and the etching time of the second material layer; and An etching selectivity ratio between the first material layer and the second material layer is obtained according to the etching rate of the first material layer and the etching rate of the second material layer.

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