A method of measuring
By measuring the relationship between the silicon layer thickness and the reference plane position, the problem that existing technologies cannot measure the intermediate oxide layer of silicon structures on insulators has been solved, realizing non-destructive measurement of the oxide layer and improving the preparation yield and process monitoring accuracy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI PRECISION MEASUREMENT SEMICON TECH INC
- Filing Date
- 2023-08-25
- Publication Date
- 2026-06-16
AI Technical Summary
Existing measurement equipment cannot accurately measure the oxide layer in the middle of the silicon structure on the insulator, which makes it impossible to accurately analyze the oxide layer and affects the preparation yield.
By obtaining the positional relationship between the silicon layer thickness and the reference plane, and using a rangefinder and film thickness measuring instrument, the characteristic parameters of the oxide layer, such as thickness, morphology and stress, can be calculated, thus achieving non-destructive measurement of the oxide layer.
Precise measurement of oxide layer characteristics without damaging the silicon-on-insulator structure improves the yield of the fabrication process and provides accurate feedback on the fabrication process.
Smart Images
Figure CN117116794B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor manufacturing technology, and more particularly to a measurement method. Background Technology
[0002] Silicon on Insulator (SOI) structures consist of three layers: top, middle, and bottom. The top and bottom layers are silicon layers, and the middle layer is an oxide layer (typically SiO2). The fabrication process for Bond and Etch back SOI (BESOI) involves thermally oxidizing a SiO2 layer on a silicon (Si) substrate, then bonding another silicon wafer to the SiO2 surface, followed by grinding to the desired thickness and planarization. During fabrication, the oxide layer undergoes deformation due to external forces, generating stress. To improve the yield of SOI structures, it is necessary to measure and analyze the oxide layer.
[0003] However, because the intermediate oxide layer of the silicon-on-insulator structure is too thin, existing measurement equipment can only measure the upper and lower silicon layers, but cannot measure the intermediate oxide layer, making it difficult to achieve accurate analysis of the oxide layer.
[0004] Therefore, it is necessary to propose a measurement method to solve the above problems. Summary of the Invention
[0005] The purpose of this invention is to provide a measurement method to improve the problem that the intermediate oxide layer of the silicon-on-insulator structure cannot be measured due to its thinness.
[0006] In a first aspect, the present invention provides a measurement method for measuring characteristic parameters of an oxide layer in a silicon-on-insulator structure, the silicon-on-insulator structure comprising, from top to bottom, a first silicon layer, an oxide layer, and a second silicon layer. The measurement method includes: obtaining the thickness of the silicon layer, the silicon layer thickness including a first thickness and / or a second thickness, wherein the first thickness is the thickness of the first silicon layer and the second thickness is the thickness of the second silicon layer; determining a reference plane and its position, the reference plane and its position including the positions of the first reference plane and / or the positions of the second reference plane and the second reference plane; obtaining the positional relationship between the reference plane and the silicon-on-insulator structure, the positional relationship including the positional relationship between the first reference plane and the first silicon layer, and / or the positional relationship between the second reference plane and the second silicon layer; and obtaining the characteristic parameters of the oxide layer based on the silicon layer thickness, the position of the reference plane, and the positional relationship.
[0007] The beneficial effects of the measurement method provided by the present invention are as follows: The present invention uses a reference plane to obtain the positional relationship between the reference plane and the silicon-on-insulator structure. By combining the silicon layer thickness and the position of the reference plane, the characteristic parameters of the oxide layer can be calculated without damaging the silicon-on-insulator structure, so as to monitor the fabrication process of the silicon-on-insulator structure and thus improve the yield of the silicon-on-insulator structure.
[0008] In one possible embodiment, determining the reference plane and its position, and obtaining the reference distance between the first reference plane and the second reference plane, includes: using a calibration sample, using the position of the upper surface of the calibration sample as the first reference plane, and / or using the position of the lower surface of the calibration sample as the second reference plane, wherein the calibration sample is a sample with known thickness.
[0009] In one possible embodiment, obtaining the positional relationship between the reference plane and the silicon-on-insulator structure includes: using a distance measured by a distance measuring instrument between the upper surface of the calibration sample and the distance measuring instrument as a first calibration distance; using a distance measured by a distance measuring instrument between the upper surface of the first silicon layer and the distance measuring instrument as a first distance; and / or using a distance measured by a distance measuring instrument between the lower surface of the calibration sample and the distance measuring instrument as a second calibration distance; using a distance measured by a distance measuring instrument between the lower surface of the second silicon layer and the distance measuring instrument as a second distance; wherein the measurement points corresponding to the first calibration distance, the first distance, the second calibration distance, and the second distance are on the same vertical line; the first distance and the first thickness correspond to the same measurement point, and the second distance and the second thickness correspond to the same measurement point.
[0010] In one possible embodiment, the characteristic parameters of the oxide layer include the thickness of the oxide layer; wherein, obtaining the thickness of the oxide layer includes: obtaining the thickness of the silicon oxide structure on the insulator based on the position of the reference plane and the positional relationship; and obtaining the thickness of the oxide layer based on the first thickness, the second thickness, and the thickness of the silicon oxide structure on the insulator.
[0011] In one possible embodiment, the characteristic parameters of the oxide layer include the thickness of the oxide layer; wherein, obtaining the thickness of the oxide layer includes: obtaining a first spacing between the upper surface of the first silicon layer and the first reference plane based on the first calibration distance and the first distance; obtaining a second spacing between the lower surface of the second silicon layer and the second reference plane based on the second calibration distance and the second distance; and calculating the thickness of the oxide layer according to the position of the reference plane, the first thickness, the second thickness, the first spacing, and the second spacing.
[0012] In one possible embodiment, the characteristic parameters of the oxide layer include the morphology of the upper surface of the oxide layer and / or the morphology of the lower surface of the oxide layer; obtaining the morphology of the upper surface of the oxide layer includes: obtaining N first calibration distances, N first distances, and N first thicknesses at N measurement sites, where N is a positive integer greater than 1; obtaining the morphology of the upper surface of the oxide layer based on obtaining the N first calibration distances, N first distances, and N first thicknesses; obtaining the morphology of the lower surface of the oxide layer includes: obtaining N second calibration distances, N second distances, and N second thicknesses at N measurement sites, where N is a positive integer greater than 1; obtaining the morphology of the lower surface of the oxide layer based on obtaining the N second calibration distances, N second distances, and N second thicknesses.
[0013] In one possible embodiment, the characteristic parameters of the oxide layer include the stress change on the upper surface of the oxide layer; before the first silicon layer is formed on the upper surface of the oxide layer, N distances between the upper surface of the oxide layer and the rangefinder are measured at N measurement points as N third distances; based on the N third distances and the N first calibration distances, the morphology of the upper surface of the oxide layer is obtained as a first morphology; after the first silicon layer is formed on the upper surface of the oxide layer, the morphology of the upper surface of the oxide layer is obtained as a second morphology; based on the first morphology and the second morphology, the stress change on the upper surface of the oxide layer is obtained by a displacement-stress model.
[0014] In one possible embodiment, the characteristic parameters of the oxide layer include the stress change of the lower surface of the oxide layer; before the first silicon layer is formed on the upper surface of the oxide layer, the morphology of the lower surface of the oxide layer is a third morphology; after the first silicon layer is formed on the upper surface of the oxide layer, the morphology of the lower surface of the oxide layer is a fourth morphology; based on the third morphology and the fourth morphology, the stress change of the lower surface of the oxide layer before and after processing is obtained by a displacement-stress model.
[0015] In one possible embodiment, the first thickness and the second thickness are obtained based on a spectral reflectance film thickness gauge; the positional relationship is obtained by a rangefinder, which is at least one of a capacitive, laser interferometric, triangular displacement sensor or color laser coaxial displacement meter.
[0016] In one possible embodiment, the first thickness is obtained by a first spectral reflectance film thickness gauge, and the second thickness is obtained by a second spectral reflectance film thickness gauge; the positional relationship between the first reference plane and the first silicon layer is obtained by a first rangefinder, and the positional relationship between the second reference plane and the second silicon layer is obtained by a second rangefinder.
[0017] Compared to existing technologies that cannot measure oxide layers, this patent can measure at least one characteristic parameter among the thickness, morphology, and stress of oxide layers. This enables the monitoring of the silicon-on-insulator fabrication process through the measured characteristic parameters, thereby improving the fabrication yield. Attached Figure Description
[0018] Figure 1 This is a flowchart illustrating the measurement method of the present invention.
[0019] Figure 2 This is a state diagram showing the state of the first silicon layer before it is formed on the surface of the oxide layer and the measurements thereon.
[0020] Figure 3 This is a state diagram showing the state after the first silicon layer is formed on the upper surface of the oxide layer and the measurements thereon.
[0021] Symbol explanation: Silicon on Insulator structure 200; First silicon layer 210; Oxide layer 220; Second silicon layer 230;
[0022] Film thickness measuring instrument 300; rangefinder 400. Detailed Implementation
[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.
[0024] An embodiment of the present invention provides a measurement method for measuring characteristic parameters of the oxide layer 220 in a silicon-on-insulator structure 200. The silicon-on-insulator structure 200 includes, from top to bottom, a first silicon layer 210, an oxide layer 220, and a second silicon layer 230. Specifically, the oxide layer 220 can be SiO2. See [link to relevant documentation]. Figure 1 and Figure 3 The measurement method includes:
[0025] S101: Obtain the silicon layer thickness, which includes a first thickness and / or a second thickness, wherein the first thickness is the thickness of the first silicon layer 210 and the second thickness is the thickness of the second silicon layer 230.
[0026] S102: Determine the reference plane and the position of the reference plane, including the position of the first reference plane and the position of the second reference plane; and / or, the position of the second reference plane and the position of the second reference plane.
[0027] S103: Obtain the positional relationship between the reference plane and the silicon-on-insulator structure 200, including the positional relationship between the first reference plane and the first silicon layer, and / or the positional relationship between the second reference plane and the second silicon layer.
[0028] S104: Based on the silicon layer thickness, the position of the reference plane, and the positional relationship, the characteristic parameters of oxide layer 220 are obtained.
[0029] The measurement method of the present invention uses a reference plane as a reference to obtain the positional relationship between the reference plane and the silicon-on-insulator structure 200. Based on the silicon layer thickness, the position of the reference plane and the positional relationship, the characteristic parameters of the oxide layer 220 can be accurately calculated. The characteristic parameters include the thickness, morphology and stress change of the oxide layer 220, so as to monitor the fabrication process of the silicon-on-insulator structure 200, improve the yield of the silicon-on-insulator structure 200, and do not damage the thickness and morphology of each layer of the silicon-on-insulator structure 200.
[0030] In a preferred embodiment, determining the reference plane and its position includes: using a calibration sample, with the position of the upper surface of the calibration sample as a first reference plane, and / or, with the position of the lower surface of the calibration sample as a second reference plane, wherein the calibration sample is a sample with a known thickness. Specifically, the upper and lower surfaces of the calibration sample are planes, and the positional relationship between the reference plane and the silicon-on-insulator structure 200 is obtained based on the position of the upper surface of the first silicon layer 210, the position of the lower surface of the second silicon layer 230, and the positions of the upper and lower surfaces of the calibration sample. More specifically, the positional relationship between the reference plane and the silicon-on-insulator structure 200 is obtained based on the position of the upper surface of the first silicon layer 210 and the position of the upper surface of the calibration sample, and / or, the position of the lower surface of the second silicon layer 230 and the position of the lower surface of the calibration sample.
[0031] In one specific embodiment, such as Figure 3As shown, obtaining the positional relationship between the reference plane and the silicon-on-insulator structure 200 includes: using the distance between the upper surface of the calibration sample and the distance measuring instrument 400 as a first calibration distance, and using the distance between the upper surface of the first silicon layer 210 and the distance measuring instrument 400 as a first distance; and / or, using the distance between the lower surface of the calibration sample and the distance measuring instrument 400 as a second calibration distance, and using the distance between the lower surface of the second silicon layer 230 and the distance measuring instrument 400 as a second distance. The measurement points corresponding to the first calibration distance, the first distance, the second calibration distance, and the second distance are on the same vertical line. The first distance and the first thickness correspond to the same measurement point, and the second distance and the second thickness correspond to the same measurement point. In this embodiment, based on the distance measuring instrument 400, the distances between the distance measuring instrument 400 and the upper surface of the first silicon layer 210, the lower surface of the second silicon layer 230, and the upper and lower surfaces of the calibration sample are measured respectively, thereby obtaining the positional relationship between the reference plane and the silicon-on-insulator structure 200. In a preferred embodiment, such as Figure 3 As shown, the characteristic parameters of oxide layer 220 include the thickness of oxide layer 220. The thickness of oxide layer 220 is obtained by: determining the thickness of the silicon oxide structure on the insulator based on the position and positional relationship of the reference plane. For example... Figure 3 As shown, the thickness of the silicon oxide structure on the insulator is equal to the sum of the thickness D3 of the first silicon layer 210, the thickness T of the oxide layer 220, and the thickness D4 of the second silicon layer 230. Based on the positions of the first and second reference planes, the distance between the first and second reference planes is D0; from the positional relationship between the first reference plane and the first silicon layer 210, the distance between the first reference plane and the first silicon layer is D1; from the positional relationship between the second reference plane and the second silicon layer 230, the distance between the second reference plane and the second silicon layer is D2. Therefore, Figure 3 The thickness of the silicon oxide structure on the insulator shown is D0 - D1 - D2. Based on the first thickness, the second thickness, and the thickness of the silicon oxide structure on the insulator, the thickness T of the oxide layer 220 is obtained, T = (D0 - D1 - D2) - D3 - D4.
[0032] In another preferred embodiment, such as Figure 3 As shown, the characteristic parameters of oxide layer 220 include the thickness of oxide layer 220. The thickness of oxide layer 220 is obtained by: determining a first distance between the upper surface of the first silicon layer 210 and the first reference plane based on a first calibration distance and a first distance; and determining a second distance between the lower surface of the second silicon layer 230 and the second reference plane based on a second calibration distance and a second distance. The thickness of oxide layer 220 is calculated based on the position of the reference plane, the first thickness, the second thickness, the first distance, and the second distance.
[0033] This invention improves the convenience and reliability of measurement by setting a reference plane, eliminating the need to calibrate the position of the rangefinder. Furthermore, the distances between the first reference plane and the first silicon layer, and between the second reference plane and the second silicon layer, obtained through the reference plane and its position, are highly accurate. Based on this, the accuracy of the obtained oxide layer characteristic parameters is improved.
[0034] In one specific embodiment, such as Figure 3 As shown, obtaining the silicon layer thickness includes: measuring the silicon layer thickness using a film thickness measuring instrument 300.
[0035] The following section uses a dual-sided rangefinder and a dual-sided film thickness measuring instrument as examples to illustrate in detail the process of measuring the thickness of the silicon oxide layer on an insulator.
[0036] 1) such as Figure 3 As shown, the silicon-on-insulator structure 200 is placed between two film thickness gauges 300 with the two film thickness gauges 300 on the same vertical line. The thickness D3 of the first silicon layer 210 is measured based on the film thickness gauge 300 located above, and the thickness D4 of the second silicon layer 230 is measured based on the film thickness gauge 300 located below.
[0037] 2) Using a calibration sample, place the calibration sample between two rangefinders 400 and measure the first calibration distance from the upper rangefinder 400 to the upper surface of the calibration sample and the second calibration distance from the lower rangefinder 400 to the lower surface of the calibration sample. Combined with the thickness D0 of the calibration sample, the vertical positions of the upper and lower surfaces of the calibration sample can be determined. The vertical position of the upper surface of the calibration sample is used as the first reference plane, and the vertical position of the lower surface of the calibration sample is used as the second reference plane.
[0038] 3) Keeping the measurement points of the two rangefinders 400 unchanged, the silicon-on-insulator structure 200 is placed between the two rangefinders 400. The first distance from the upper rangefinder 400 to the upper surface of the first silicon layer 210 and the second distance from the lower rangefinder 400 to the lower surface of the second silicon layer 230 are measured. The vertical positions of the upper surface of the first silicon layer 210 and the lower surface of the second silicon layer 230 can be determined. The first gap D1 is obtained based on the first calibration distance and the first distance. The second gap D2 is obtained based on the second calibration distance and the second distance.
[0039] 4) The thickness of the oxide layer 220 at the measurement site was calculated to be T = D0 - (D1 + D2 + D3 + D4).
[0040] The above embodiments solve the technical problem that existing technologies cannot measure oxide layer thickness. Without damaging the silicon-on-insulator (SiO2) structure, they achieve the measurement of the oxide layer thickness in the fabricated SiO2 structure. Feedback can be provided to the SiO2 fabrication process based on the oxide layer thickness measurement results to improve the yield of the fabrication process. Furthermore, by applying the technical solution of the above embodiments and measuring the oxide layer thickness at multiple different locations on the SiO2 structure, the variation in the overall oxide layer thickness can be obtained, providing more accurate feedback to the SiO2 fabrication process.
[0041] It should be noted that the thickness and distance measurements on the same side are performed at the same measurement points. That is, the rangefinder 400 and the film thickness measuring instrument 300 located above perform measurements at the same measurement points, and the rangefinder 400 and the film thickness measuring instrument 300 located below perform measurements at the same measurement points. Furthermore, the measurement points corresponding to the first calibration distance, the first distance, the second calibration distance, and the second distance are on the same vertical line.
[0042] In a preferred embodiment, such as Figure 3 As shown, the characteristic parameters of oxide layer 220 include the morphology of the upper surface and / or the lower surface of oxide layer 220. The morphology of the upper surface of oxide layer 220 is obtained by: obtaining N first calibration distances, N first distances, and N first thicknesses at N measurement points, where N is a positive integer greater than 1. Based on the obtained N first calibration distances, N first distances, and N first thicknesses, the morphology of the upper surface of oxide layer 220 is obtained. The morphology of the lower surface of oxide layer 220 is obtained by: obtaining N second calibration distances, N second distances, and N second thicknesses at N measurement points, where N is a positive integer greater than 1. Based on the obtained N second calibration distances, N second distances, and N second thicknesses, the morphology of the lower surface of oxide layer 220 is obtained.
[0043] The process of measuring the surface morphology of the oxide layer on a silicon-on-insulator structure is described in detail below with reference to specific embodiments.
[0044] like Figure 3 As shown, at N measurement points, N first thicknesses D3 are measured using a film thickness measuring instrument 300, and N first calibration distances and N first distances are measured using a rangefinder 400. Based on the N first calibration distances and N first distances, N first spacings D1 are calculated to obtain the morphology of the upper surface of the first silicon layer 210. Based on the morphology of the upper surface of the first silicon layer 210 and the N first thicknesses D3, the morphology of the upper surface of the oxide layer 220 is obtained.
[0045] The morphology of the upper surface of the oxide layer 220 can be determined by (x i y i , z10 -D i1 -D i3 ) represents, where i represents the i-th measurement site, where i∈[1,N], z 10 D represents the value of the first reference plane on the z-axis. i1 D represents the first spacing of the i-th element. i3 This represents the i-th first thickness.
[0046] The process of measuring the lower surface morphology of the silicon oxide layer on an insulator is described in detail below with reference to specific embodiments.
[0047] like Figure 3 As shown, at N measurement points, N second thicknesses D4 are measured using a film thickness measuring instrument 300, and N second calibration distances and N second distances are measured using a rangefinder 400. Based on the N second calibration distances and N second distances, N second spacings D2 are calculated to obtain the morphology of the lower surface of the second silicon layer 230. Based on the morphology of the lower surface of the second silicon layer 230 and the N second thicknesses D4, the morphology of the lower surface of the oxide layer 220 is obtained.
[0048] The morphology of the lower surface of oxide layer 220 can be determined by (x i y i , z 20 +D i2 +D i4 ) represents, where i represents the i-th measurement site, i∈[1,N], z 20 D represents the value of the second reference plane on the z-axis. i2 D represents the i-th second spacing. i4 This represents the i-th second thickness. Furthermore, z... 10 -z 20 =D0.
[0049] In a preferred embodiment, the characteristic parameters of the oxide layer 220 include the stress change on the upper surface of the oxide layer 220 before and after processing, where "before processing" refers to before the formation of the first silicon layer 210 and before obtaining a complete silicon-on-insulator structure, and "after processing" refers to the formation of the first silicon layer 210 and obtaining a complete silicon-on-insulator structure 200; such as Figure 2 As shown, before the first silicon layer 210 is formed on the upper surface of the oxide layer 220, N distances between the upper surface of the oxide layer 220 and the rangefinder are measured at N measurement points and used as N third distances; based on the N third distances and the N first calibration distances, the morphology of the upper surface of the oxide layer 220 before processing is obtained. Figure 3As shown, after the first silicon layer 210 is formed on the upper surface of the oxide layer 220, the morphology of the upper surface of the oxide layer 220 obtained in the above embodiment is the morphology of the upper surface of the oxide layer 220 after processing. Based on the morphology of the upper surface of the oxide layer 220 before processing and the morphology of the upper surface of the oxide layer 220 after processing, the stress change of the upper surface of the oxide layer 220 before and after processing is obtained by displacement-stress model, that is, the stress change of the upper surface of the oxide layer 220 before and after forming the first silicon layer 210 is obtained.
[0050] In one specific embodiment, based on the morphology of the upper surface of the oxide layer 220 before processing and the morphology of the upper surface of the oxide layer 220 after processing, the stress change of the upper surface of the oxide layer 220 before and after processing is obtained by displacement-stress model, including: calculating the local average curvature of N upper surface points based on the position coordinates of N upper surface points before processing and the position coordinates of N upper surface points after processing; and calculating the stress of N upper surface points based on the local average curvature of N upper surface points by displacement-stress model, wherein the upper surface points correspond one-to-one with the measurement points, and the upper surface points and the corresponding measurement points are on the same vertical line.
[0051] In one specific embodiment, the local average curvature of the N upper surface points is calculated based on their pre-processing and post-processing position coordinates, including: obtaining the offset u of the N upper surface points in the x-axis direction, the offset v in the y-axis direction, and the offset w in the z-axis direction based on their pre-processing and post-processing position coordinates.
[0052] Specifically, the local average curvature of N measurement points on the upper surface is calculated using the following formula:
[0053]
[0054]
[0055] Where, ε x ε is the deformation per unit length of a point on the upper surface along the x-axis; y ε is the deformation per unit length of a point on the upper surface along the y-axis. z γ is the deformation per unit length of a point on the upper surface along the z-axis; xy γ is the deformation per unit length of a point on the upper surface in the xy plane; yz γ is the deformation per unit length of a point on the upper surface in the yz plane; zx This represents the deformation per unit length of the point on the upper surface in the zx plane.
[0056] In one specific embodiment, the stress calculation formula for the upper surface points is as follows:
[0057]
[0058]
[0059] Where σ is the stress at a point on the upper surface; σ x σ represents the stress at a point on the upper surface along the x-axis. y σ represents the stress at a point on the upper surface along the y-axis. z τ represents the stress at a point on the upper surface along the z-axis. xy τ represents the stress at a point on the upper surface in the xy plane. yz τ is the stress at a point on the upper surface in the yz plane; zx The stress at a point on the upper surface in the zx plane is E; the elastic modulus is μ; the Poisson's ratio is ε. x ε is the deformation per unit length of a point on the upper surface along the x-axis; y ε is the deformation per unit length of a point on the upper surface along the y-axis. z γ is the deformation per unit length of a point on the upper surface along the z-axis; xy γ is the deformation per unit length of a point on the upper surface in the xy plane; yz γ is the deformation per unit length of a point on the upper surface in the yz plane; zx This represents the deformation per unit length of a point on the upper surface in the zx plane. The equivalent stress at the upper surface point is denoted as .
[0060] In a preferred embodiment, the characteristic parameters of the oxide layer 220 include the stress change on the lower surface of the oxide layer 220 before and after processing, where "before processing" refers to before the formation of the first silicon layer 210 and before obtaining a complete silicon-on-insulator structure, and "after processing" refers to the formation of the first silicon layer 210 and obtaining a complete silicon-on-insulator structure 200; such as Figure 2 As shown, before the first silicon layer 210 is formed on the upper surface of the oxide layer 220, the morphology of the lower surface of the oxide layer 220 obtained in the above embodiment is the morphology of the lower surface of the oxide layer 220 before processing. Figure 3 As shown, after the first silicon layer 210 is formed on the upper surface of the oxide layer 220, the morphology of the lower surface of the oxide layer 220 obtained in the above embodiment is the morphology of the lower surface of the oxide layer 220 after processing. Based on the morphology of the lower surface of the oxide layer 220 before processing and the morphology of the lower surface of the oxide layer 220 after processing, the stress change of the lower surface of the oxide layer 220 before and after processing is obtained by displacement-stress model, that is, the stress change of the lower surface of the oxide layer 220 before and after forming the first silicon layer 210 is obtained.
[0061] In one specific embodiment, based on the morphology data of the lower surface of the oxide layer 220 before and after processing, and the morphology data of the lower surface of the oxide layer 220 after processing, stress change data of the lower surface of the oxide layer 220 before and after processing are obtained using a displacement-stress model. This includes: calculating the local average curvature of N lower surface points based on their pre-processing and post-processing position coordinates; and calculating the stress of N lower surface points based on their local average curvature using a displacement-stress model. The calculation methods for the local average curvature and stress of the lower surface points are the same as those for the upper surface points in the above embodiment, and will not be repeated here.
[0062] The following detailed description, using specific embodiments, illustrates the process of stress measurement on the upper and lower surfaces of the oxide layer of a silicon-on-insulator structure.
[0063] The first and second reference planes are obtained using calibration samples. For example, the first and second calibration distances are measured based on the dual-side rangefinder 400. The positions of the upper and lower surfaces of the calibration sample are used as the first and second reference planes, respectively. The distance d0 between the first and second reference planes is the thickness of the calibration sample.
[0064] like Figure 2 As shown, before the first silicon layer 210 is formed, during measurement at a measurement point, the thickness d3 of the second silicon layer 230 before processing is measured using a film thickness measuring instrument 300. The distance between the upper surface of the oxide layer 220 and the distance measuring instrument is measured using a dual-sided distance measuring instrument 400 as the third distance, and the distance between the lower surface of the second silicon layer 230 and the distance measuring instrument is measured as the second distance. Thickness and distance measurements on the same side are performed at the same measurement point. This measurement step is repeated to complete measurements at multiple measurement points. Based on the third distance and the first calibration distance, the distance d1 of the upper surface of the oxide layer 220 relative to the first reference plane is obtained. Based on the distances d1 from multiple measurement points, the morphology of the upper surface of the oxide layer 220 before processing is obtained. Based on the second distance to the lower surface of the second silicon layer 230, the thickness d3 of the second silicon layer 230 before processing, and the second calibration distance, the morphology of the lower surface of the oxide layer 220 before processing is obtained.
[0065] Before the first silicon layer 210 is formed, the value d2 is recorded as the positioning value of the outer surface of the SOI structure. Using this positioning value as a reference plane, after the first silicon layer 210 is formed, the position of the lower surface of the second silicon layer 230 of the SOI structure is adjusted to be consistent with that before the first silicon layer 210 is formed, that is, the distance d2 between the lower surface of the oxide layer 220 before processing and the second reference plane is equal to the distance D2 between the lower surface of the oxide layer 220 after processing and the second reference plane. Figure 2 The position of the lower surface of the second silicon layer 230 shown is the same as Figure 3 The lower surface of the second silicon layer 230 shown is in the same position.
[0066] like Figure 3 As shown, after the formation of the first silicon layer 210, a complete silicon-on-insulator structure is obtained. During measurement at a measurement point, the thickness D3 of the first silicon layer 210 and the thickness D4 of the processed second silicon layer 230 are measured using a film thickness gauge 300. The distance between the upper surface of the first silicon layer 210 and the distance gauge is measured using a dual-sided distance measuring instrument 400, serving as the first distance, and the distance between the lower surface of the second silicon layer 230 and the distance gauge is measured as the second distance. Thickness and distance measurements on the same side are performed at the same measurement point. This measurement process is repeated to complete measurements at multiple measurement points. Based on the first distance, the first calibration distance, and the thickness D3 of the first silicon layer 210, the morphology of the upper surface of the processed oxide layer 220 is obtained. Similarly, based on the second distance, the second calibration distance, and the thickness D4 of the processed second silicon layer 230, the morphology of the lower surface of the processed oxide layer 220 is obtained.
[0067] Based on the morphology of the upper surface of oxide layer 220 before and after processing, the morphological changes of the upper surface of oxide layer 220 are obtained. Based on the morphology of the lower surface of oxide layer 220 before and after processing, the morphological changes of the lower surface of oxide layer 220 are also obtained. Based on the morphological changes of the upper surface of oxide layer 220, the stress changes of the upper surface of oxide layer 220 before and after processing are obtained using a displacement-stress model. Based on the morphological changes of the lower surface of oxide layer 220, the stress changes of the lower surface of oxide layer 220 before and after processing are also obtained using a displacement-stress model. Therefore, the stress changes of oxide layer 220 during the fabrication process of silicon-on-insulator structure 200 can be obtained. Based on the feedback of the obtained stress changes, the fabrication process can be adjusted to improve the fabrication yield.
[0068] In the above embodiments, the film thickness measuring instrument 300 is a spectral reflectance type film thickness measuring instrument, and the positional relationship is obtained by the rangefinder 400. The rangefinder 400 can be at least one of capacitive, laser interferometric, triangular displacement sensor, or color laser coaxial displacement meter. Furthermore, the light emitted by the rangefinder 400 and the film thickness measuring instrument 300 can be a point light source. To improve measurement efficiency, it can also be a line light source or a surface light source. When using a line or surface light source, the corresponding optical elements and detectors need to be replaced simultaneously.
[0069] Furthermore, in the above embodiments, Figure 2 , 3 The schematic diagram shown does not constitute a limitation of this patent. Figure 3The first reference plane shown is located above the first silicon layer 210, and the second reference plane is located below the second silicon layer 230. This is only for the convenience of describing the technical solution of this patent. It is easily understood that this patent does not impose specific restrictions on the positional relationship between the first reference plane and the first silicon layer, or the positional relationship between the second reference plane and the second silicon layer. Accordingly, for Figure 3 The positional relationship between the first reference plane and the first silicon layer 210, and the positional relationship between the second reference plane and the second silicon layer 230, can be adaptively adjusted according to the formulas of each embodiment. The dual-sided rangefinder and dual-sided film thickness measuring instrument in the above embodiments are illustrative examples and do not constitute a limitation of this patent. It is easy to imagine that the rangefinder and film thickness measuring instrument can be set only on the same side to measure the morphology and stress of one surface of the oxide layer.
[0070] This invention provides a method for measuring the oxide layer of a silicon-on-insulator (SOI) structure. Without damaging the SOI structure, it utilizes a film thickness gauge and a rangefinder 400 to measure the thickness, morphology, and stress of the oxide layer 220. This maintains the integrity and original structure of the sample, and the rangefinder 400 does not require pre-calibration of its longitudinal relative position. More accurate, comprehensive, and reliable oxide layer 220 thickness data is obtained through multiple measurement points. Multi-point measurements and morphology mapping provide a comprehensive understanding of the morphological changes in the oxide layer 220, identifying potential problems and defects. Using a displacement-stress model, combined with data from morphology and thickness measurements, the stress changes in the oxide layer 220 are calculated. Stress measurement helps monitor stress changes in the oxide layer 220 during the SOI fabrication process, understand potential stress problems, optimize the fabrication process, and improve the yield of SOI structures.
[0071] Embodiments of the present invention also provide a measurement system for silicon-on-insulator oxide layers, such as... Figure 3 As shown, the measurement method in any of the above embodiments is applied to the measurement system to obtain the characteristic parameters of the oxide layer 220 in the silicon-on-insulator structure 200. The silicon-on-insulator structure 200 includes a first silicon layer 210, an oxide layer 220, and a second silicon layer 230 from top to bottom. The measurement system includes at least one film thickness measuring instrument 300 and at least one distance measuring instrument 400. The film thickness measuring instrument 300 is used to measure the thickness of the first silicon layer 210 and the thickness of the second silicon layer 230. The distance measuring instrument 400 is used to obtain the positional relationship between the first reference plane, the second reference plane, and the silicon-on-insulator structure 200.
[0072] In some possible embodiments, the film thickness measuring instrument 300 is a spectral reflectance film thickness measuring instrument, and the rangefinder 400 may be at least one of capacitive, laser interferometric, triangular displacement sensor or color laser coaxial displacement meter.
[0073] In other possible embodiments, the light emitted by the rangefinder 400 and the film thickness measuring instrument 300 can be a point light source, or a line light source or a surface light source, to improve measurement efficiency. When using a line or surface light source, the corresponding optical elements and detectors need to be replaced simultaneously.
[0074] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as defined in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.
Claims
1. A measurement method for measuring characteristic parameters of an oxide layer in a silicon-on-insulator structure, wherein the silicon-on-insulator structure comprises, from top to bottom, a first silicon layer, an oxide layer, and a second silicon layer, characterized in that, The measurement method includes: The thickness of the silicon layer is obtained, wherein the thickness of the silicon layer includes a first thickness and / or a second thickness, the first thickness being the thickness of the first silicon layer and the second thickness being the thickness of the second silicon layer; Determine the reference planes and their positions, including the positions of the first reference planes and / or the positions of the second reference planes; use a calibration sample, with the position of the upper surface of the calibration sample as the first reference plane, and / or the position of the lower surface of the calibration sample as the second reference plane; the calibration sample is a sample with known thickness; The positional relationship between the reference plane and the silicon-on-insulator structure is obtained, including the positional relationship between the first reference plane and the first silicon layer, and / or the positional relationship between the second reference plane and the second silicon layer; the distance between the upper surface of the calibration sample and the distance measuring instrument is measured by the distance measuring instrument as a first calibration distance, and the distance between the upper surface of the first silicon layer and the distance measuring instrument is measured by the distance measuring instrument as a first distance; and / or, the distance between the lower surface of the calibration sample and the distance measuring instrument is measured by the distance measuring instrument as a second calibration distance, and the distance between the lower surface of the second silicon layer and the distance measuring instrument is measured by the distance measuring instrument as a second distance; the measurement points corresponding to the first calibration distance, the first distance, the second calibration distance, and the second distance are on the same vertical line; the first distance and the first thickness correspond to the same measurement point, and the second distance and the second thickness correspond to the same measurement point; The characteristic parameters of the oxide layer are obtained based on the silicon layer thickness, the position of the reference plane, and the positional relationship.
2. The method according to claim 1, characterized in that, The characteristic parameters of the oxide layer include the thickness of the oxide layer; wherein, obtaining the thickness of the oxide layer includes: Based on the position of the reference plane and the positional relationship, the thickness of the silicon oxide structure on the insulator is obtained; The thickness of the oxide layer is obtained based on the first thickness, the second thickness, and the thickness of the silicon oxide structure on the insulator.
3. The method according to claim 1, characterized in that, The characteristic parameters of the oxide layer include the thickness of the oxide layer; wherein, obtaining the thickness of the oxide layer includes: Based on the first calibration distance and the first distance, the first spacing between the upper surface of the first silicon layer and the first reference surface is obtained; Based on the second calibration distance and the second distance, the second spacing between the lower surface of the second silicon layer and the second reference plane is obtained; The oxide layer thickness is calculated based on the position of the reference surface, the first thickness, the second thickness, the first spacing, and the second spacing.
4. The method according to claim 1, characterized in that, The characteristic parameters of the oxide layer include the morphology of the upper surface of the oxide layer and / or the morphology of the lower surface of the oxide layer; Obtaining the morphology of the upper surface of the oxide layer includes: obtaining N first calibration distances, N first distances, and N first thicknesses at N measurement sites, respectively, where N is a positive integer greater than 1; Based on obtaining N first calibration distances, N first distances, and N first thicknesses, the morphology of the upper surface of the oxide layer is obtained; Obtaining the morphology of the lower surface of the oxide layer includes: At N measurement points, N second calibration distances, N second distances, and N second thicknesses are obtained respectively, where N is a positive integer greater than 1; Based on obtaining N second calibration distances, N second distances, and N second thicknesses, the morphology of the lower surface of the oxide layer is obtained.
5. The method according to claim 4, characterized in that, The characteristic parameters of the oxide layer include the stress variation on the upper surface of the oxide layer; Before the first silicon layer is formed on the upper surface of the oxide layer, at N measurement points, N distances between the upper surface of the oxide layer and the rangefinder are measured by a rangefinder and used as N third distances; based on the N third distances and the N first calibration distances, the morphology of the upper surface of the oxide layer is obtained as the first morphology; After the first silicon layer is formed on the upper surface of the oxide layer, the morphology of the upper surface of the oxide layer is the second morphology. Based on the first morphology and the second morphology, the stress change on the upper surface of the oxide layer is obtained using a displacement-stress model.
6. The method according to claim 4, characterized in that, The characteristic parameters of the oxide layer include the stress variation on the lower surface of the oxide layer; Before the first silicon layer is formed on the upper surface of the oxide layer, the morphology of the lower surface of the oxide layer is the third morphology; after the first silicon layer is formed on the upper surface of the oxide layer, the morphology of the lower surface of the oxide layer is the fourth morphology. Based on the third and fourth morphologies, the stress variation on the lower surface of the oxide layer is obtained using a displacement-stress model.
7. The method according to claim 1, characterized in that, The first thickness and the second thickness are obtained using a spectral reflectance film thickness gauge; The positional relationship is obtained by a rangefinder, which is at least one of capacitive, laser interferometric, triangular displacement sensor or color laser coaxial displacement meter.
8. The method according to claim 1 or 7, characterized in that, The first thickness was obtained by a first spectral reflectance film thickness gauge, and the second thickness was obtained by a second spectral reflectance film thickness gauge; The positional relationship between the first reference plane and the first silicon layer is obtained by the first rangefinder, and the positional relationship between the second reference plane and the second silicon layer is obtained by the second rangefinder.