A method for monitoring thin film processes

Abstract

This invention discloses a method for monitoring thin film processes, belonging to the field of semiconductor manufacturing. In this method, for thin films that require periodic growth and monitoring, the differences in different OVL marks are measured, and the target value is compared with the range of variation to determine whether it meets the requirements. This solves the problems of insufficient monitoring capabilities and difficulties in measuring the physicochemical properties of thin films with special properties and complex compositions.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of semiconductor process manufacturing, and in particular to a method for monitoring thin film processes. Background Technology

[0002] In relevant thin film process monitoring methods, monitoring is mainly carried out through equipment and process parameters, as well as the physical and chemical properties of the formed thin film for specific monitoring and analysis.

[0003] However, the properties of thin films are not sensitive to changes in equipment and process parameters. Furthermore, the examination of individual physical and chemical properties (thickness, refractive index, and reaction rate of certain chemical components) is not comprehensive. Moreover, for thin films with special properties and complex compositions, there are problems of insufficient monitoring capabilities and difficulties in measuring physicochemical properties. Summary of the Invention

[0004] This invention provides a method for monitoring thin film processes to avoid the problems of insufficient monitoring capabilities and difficulties in measuring the physicochemical properties of thin films with special properties and complex compositions. The technical solution is as follows:

[0005] This invention provides a method for monitoring thin film processes, the method comprising:

[0006] Thin film process monitoring is performed on the silicon wafer under test to obtain the OVL mark difference of different substrates. The silicon wafer under test corresponds to at least two sets of OVL mark substrates.

[0007] The difference between the obtained OVL mark and the target value is compared to determine the range of variation of the difference. The target value is obtained by monitoring the thin film process on the sample silicon wafer.

[0008] Based on the target value and the variable range, the OVL mark difference of the second film that needs to be monitored during periodic growth is monitored.

[0009] Optionally, the content of the thin film process monitoring operation includes:

[0010] The first step is to deposit a first thin film, and after the first photolithography and the first etching to remove the resist, at least two sets of OVL mark substrates are formed. The at least two sets of OVL mark substrates include an OVL mark substrate with the first thin film retained and an OVL mark substrate with the first thin film removed.

[0011] The second step involves depositing a second thin film, which, after a second photolithography and second etching process to remove the resist, forms part of the OVL mark pattern and serves as the alignment layer.

[0012] The third step involves forming another part of the OVL mark after the third photolithography process to remove the resist, which serves as an alignment layer.

[0013] The fourth step is to eliminate the OVL difference between the second and third photolithography processes using the OVL compensation method.

[0014] The fifth step is to measure the overlay accuracy of the OVL mark substrate after the fourth step, and use the difference as the target value.

[0015] Optionally, the content of the first step includes:

[0016] The first thin film is grown on at least two sets of substrates;

[0017] The substrate is subjected to the first photolithography and the first etching.

[0018] After completion, the first thin film is retained on at least one set of substrates, and the first thin film is removed from at least one set of substrates to obtain the at least two sets of OVL mark substrates.

[0019] Optionally, in the thin film process monitoring operation, the second thin film is grown using the OVL mark substrate formed in the first step; the difference between different OVL marks is measured through the second to fifth steps.

[0020] The step of monitoring the OVLmark difference of the second thin film that needs to be monitored periodically based on the target value and the variable range includes:

[0021] The OVL mark difference is compared with the target value and the variable range to determine whether the OVL mark difference is within the variable range.

[0022] Optionally, a biasing experiment can be performed on the equipment and process parameters for monitoring the growth of the second thin film to grow the second thin film, thereby obtaining silicon wafers under test within the permissible range of different equipment and process deviations.

[0023] Optionally, the first thin film is SiN, One of SiON and SiC.

[0024] Optionally, the first thin film is one of a compound thin film formed from O, C, N and Si.

[0025] Optionally, the second thin film is SiGe.

[0026] This invention provides a method for monitoring thin film processes. In this method, for thin films that need to be monitored during periodic growth, the differences of different OVL marks are measured, and the target value is compared with the range of variation to determine whether it meets the requirements. This solves the problems of insufficient monitoring capabilities and difficulty in measuring the physicochemical properties of thin films with special properties and complex compositions. Attached Figure Description

[0027] Figure 1 This is a flowchart of the thin film process monitoring method provided by the present invention;

[0028] Figure 2 yes Figure 1 The flowchart corresponding to the monitoring operation of the thin film process. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0030] In this article, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0031] In relevant thin film process monitoring methods, monitoring is mainly carried out through equipment and process parameters, as well as the physical and chemical properties of the formed thin film for specific monitoring and analysis.

[0032] However, thin film properties are not sensitive to changes in equipment and process parameters. Furthermore, the examination of individual physical and chemical properties (thickness, refractive index, and reaction rates of certain chemical components) is not comprehensive. Moreover, for thin films with special properties and complex compositions, there are problems with insufficient monitoring capabilities and difficulties in measuring physicochemical properties. Further analysis is needed to address these issues.

[0033] Regarding the aforementioned issues, the applicant also analyzed the differences in SiGeC characteristics on several different substrate surfaces. Among them, the films grown on single-crystal silicon surfaces are relatively smooth, while the films grown on silicon dioxide, silicon nitride, and amorphous silicon surfaces have different degrees of roughness and different optical properties, even exhibiting extreme differences in characteristics. This results in insufficient monitoring capabilities and difficulties in measuring the physicochemical properties of films with special properties and complex compositions.

[0034] Furthermore, the effects of variations in thin film growth process parameters or differences in composition on the same substrate were analyzed, revealing that the thin film properties are not sensitive to changes in equipment and process parameters. Therefore, based on the aforementioned technical problems to be solved, the applicant proposes a thin film process monitoring method.

[0035] Please refer to Figure 1 This document illustrates a flowchart of a thin-film process monitoring method according to an exemplary embodiment of the present invention. It includes the following process steps.

[0036] S1, perform thin film process monitoring operation on the silicon wafer under test to obtain the OVL mark difference of different substrates. The silicon wafer under test has at least two sets of OVL mark substrates.

[0037] In one possible implementation, a stretching experiment is performed on the equipment and process parameters for monitoring the growth of the second thin film to grow the second thin film, thereby obtaining a silicon wafer under test within the permissible range of different equipment and process deviations.

[0038] Thin film process monitoring is the operation process of obtaining the OVL mark difference of different substrates, which is further disclosed in the following embodiments.

[0039] S2, compare the obtained OVL mark difference with the target value to determine the range of variation of the difference. The target value is obtained by monitoring the thin film process of the sample silicon wafer.

[0040] The process of obtaining the target value through a sample silicon wafer is further disclosed in the following embodiments.

[0041] S3, based on the target value and the variable range, monitor the OVL mark difference of the second film that needs to be monitored during periodic growth.

[0042] In summary, the present invention discloses a method for monitoring thin film processes. In this method, for thin films that need to be monitored during periodic growth, the differences of different OVL marks are measured, and the target value is compared with the range of variation to determine whether it meets the requirements. This solves the problems of insufficient monitoring capabilities and difficulty in measuring the physicochemical properties of thin films with special properties and complex compositions.

[0043] Please refer to Figure 2 It shows Figure 1 The flowchart for monitoring the thin film process includes the following process steps.

[0044] The first step is to deposit a first thin film, and after the first photolithography and the first etching to remove the resist, at least two sets of OVL mark substrates are formed. The at least two sets of OVL mark substrates include an OVL mark substrate with the first thin film retained and an OVL mark substrate with the first thin film removed.

[0045] In one possible implementation, a first thin film is grown on at least two sets of substrates; the substrates are subjected to a first photolithography and a first etching; after completion, the first thin film is retained on at least one set of substrates, and the first thin film is removed from at least one set of substrates to obtain at least two sets of OVL mark substrates.

[0046] The first thin film is SiN, It is one of the following compound films formed from SiON, SiC, and other O, C, N, and Si, but is not limited thereto.

[0047] The second step involves depositing a second thin film, which, after a second photolithography and second etching process to remove the resist, forms part of the OVL mark pattern and serves as the alignment layer.

[0048] Optionally, the second thin film may be illustrated using SiGe, but this is not a limitation.

[0049] The third step involves forming another part of the OVL mark after the third photolithography process to remove the resist, which serves as an alignment layer.

[0050] The fourth step is to eliminate the OVL difference between the second and third photolithography processes using the OVL compensation method.

[0051] In one possible implementation, the systematic error between the second and third photolithography processes is eliminated by using the OVL compensation method, thereby obtaining the best OVL alignment effect.

[0052] The fifth step is to measure the overlay accuracy of the OVL mark substrate after the fourth step, and use the difference as the target value.

[0053] In one possible implementation, during the thin film process monitoring operation, a second thin film is grown using the OVL mark substrate formed in the first step; different OVL mark differences are measured through the second to fifth steps; the process of monitoring the OVL mark difference of the periodically grown second thin film according to the target value and the variable range includes: comparing the OVL mark difference with the target value and the variable range to determine whether the OVL mark difference is within the variable range.

[0054] In summary, the thin film process monitoring method provided in this invention addresses the problem of insufficient monitoring capabilities and difficulty in measuring physicochemical properties of thin films with special properties and complex compositions. This method involves designing different OVL mark substrates, resulting in different measurement results for different OVL marks after thin film growth. Using the difference between different OVL marks after standard thin film growth as the target value, a bias experiment is conducted on the equipment and process parameters for thin film growth. Within the permissible range of equipment and process deviations, the maximum and minimum differences between different OVL marks are obtained. For thin films requiring periodic growth monitoring, the differences between different OVL marks are measured, and the target value is compared with the variation range to determine whether the requirements are met. This solves the problems of insufficient monitoring capabilities and difficulty in measuring the physicochemical properties of thin films with special properties and complex compositions.

[0055] The above description is merely an optional embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for monitoring thin film processes, characterized in that, The method includes: Thin film process monitoring is performed on the silicon wafer under test to obtain the OVL mark difference of different substrates. The silicon wafer under test corresponds to at least two sets of OVL mark substrates. The difference between the obtained OVL mark and the target value is compared to determine the range of variation of the difference. The target value is obtained by monitoring the thin film process on the sample silicon wafer. Based on the target value and the variable range, the OVL mark difference of the second film that needs to be monitored during periodic growth is monitored.

2. The method as described in claim 1, characterized in that, The content of the thin film process monitoring operation includes: The first step is to deposit a first thin film, and after the first photolithography and the first etching to remove the resist, at least two sets of OVL mark substrates are formed. The at least two sets of OVL mark substrates include an OVL mark substrate with the first thin film retained and an OVL mark substrate with the first thin film removed. The second step involves depositing a second thin film, which, after a second photolithography and second etching process to remove the resist, forms part of the OVL mark pattern and serves as the alignment layer. The third step involves forming another part of the OVL mark after the third photolithography process to remove the resist, which serves as an alignment layer. The fourth step is to eliminate the OVL difference between the second and third photolithography processes using the OVL compensation method. The fifth step is to measure the overlay accuracy of the OVL mark substrate after the fourth step, and use the difference as the target value.

3. The method as described in claim 2, characterized in that, The first step includes: The first thin film is grown on at least two sets of substrates; The substrate is subjected to the first photolithography and the first etching. After completion, the first thin film is retained on at least one set of substrates, and the first thin film is removed from at least one set of substrates to obtain the at least two sets of OVL mark substrates.

4. The method as described in claim 2, characterized in that, In the thin film process monitoring operation, the second thin film is grown on the OVL mark substrate formed in the first step; the difference between different OVL marks is measured through the second to fifth steps. The monitoring of the OVL mark difference for the periodically grown second thin film based on the target value and the variable range includes: The OVL mark difference is compared with the target value and the variable range to determine whether the OVL mark difference is within the variable range.

5. The method as described in any one of claims 2 to 4, characterized in that, The second thin film was grown by performing a stretching experiment on the equipment and process parameters that need to be monitored to obtain silicon wafers under test within the permissible range of different equipment and process deviations.

6. The method as described in any one of claims 2 to 4, characterized in that, The first thin film is SiN, One of SiON and SiC.

7. The method as described in any one of claims 2 to 4, characterized in that, The first thin film is one of the compound thin films formed from O, C, N and Si.

8. The method according to any one of claims 2 to 4, characterized in that, The second thin film is SiGe.

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