Overlay accuracy detection method and detection structure

Abstract

A method for detecting overlay accuracy and a detection structure thereof, wherein the method comprises: providing a substrate; forming a first film layer on the substrate, the first film layer having a plurality of groups of first test portions; forming a second film layer on the first film layer, the second film layer having a plurality of groups of second test portions, a group of first test portions and a corresponding group of second test portions forming a test group, and the design overlay deviation values of different test groups being different; detecting each test group by using a first optical signal, the first optical signal being converted into a second optical signal; and obtaining an actual overlay deviation value according to the design overlay deviation value of the test group corresponding to the second optical signal. In this detection process, objective physical characteristics are utilized, the influence of external factors is reduced, and the accuracy of overlay accuracy is improved. In addition, since optical detection has strong penetration, the detection can be performed after the second film layer is formed, effectively shortening the detection period.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a method and structure for detecting overlay accuracy. Background Technology

[0002] In semiconductor manufacturing, photolithography has evolved as a core technology across each generation. This process typically involves dozens of photolithography steps, and factors affecting errors include not only the resolution of the photolithography machine but also the accuracy of alignment. Ensuring the alignment accuracy of each photolithography step improves the alignment between the current layer and the preceding layer within a certain range, known as overlay (OVL). Since semiconductor integrated circuits are manufactured by stacking multiple layers, significant alignment deviations between the current and preceding layers can cause the fabricated device to malfunction. Therefore, the overlay accuracy in photolithography is crucial and must meet design requirements.

[0003] However, there are still many problems with the existing overlay accuracy detection technology. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a method and structure for detecting overlay accuracy, thereby improving the accuracy of overlay and shortening the detection cycle.

[0005] To address the aforementioned problems, the present invention provides a method for detecting overlay accuracy, comprising: providing a substrate; forming a first film layer on the substrate, the first film layer having a plurality of first test portions; forming a second film layer on the first film layer, the second film layer having a plurality of second test portions corresponding to the first test portions, a group of first test portions and a corresponding group of second test portions constituting a test group, different test groups having different designed overlay deviation values; using a first optical signal to detect each test group, and when the first test portion and the second test portion in a certain test group have projected overlap in the direction toward the substrate, the first optical signal is converted into a second optical signal; obtaining the test group corresponding to the conversion of the first optical signal into the second optical signal; and obtaining the actual overlay deviation value based on the designed overlay deviation value of the test group corresponding to the conversion of the first optical signal into the second optical signal.

[0006] Optionally, the first test section includes: a plurality of first test pieces arranged along a first direction; the second test section includes: a plurality of second test pieces arranged along the first direction; the plurality of first test pieces have a first projection pattern on the substrate, the plurality of second test pieces have a second projection pattern on the substrate, and the second projection pattern is located between corresponding adjacent first projection patterns.

[0007] Optionally, the first direction is defined as the positive direction, and a first spacing value between the second projected image and the adjacent first projected image is obtained along the first direction; the second direction is defined as the negative direction, and the second direction is opposite to the first direction, and a second spacing value between the second projected image and the adjacent first projected image is obtained along the second direction; the sum of the first spacing value and the second spacing value is divided by 2 as the design overlay deviation value.

[0008] Optionally, the first optical signal includes a linear optical signal.

[0009] Optionally, the second optical signal includes a nonlinear optical signal.

[0010] Optionally, the design overlay deviation values ​​between different test groups are increased in increments of 0.5 nm to 1 nm.

[0011] Optionally, the method for obtaining the actual overlay deviation value based on the design overlay deviation value of the test group corresponding to the second optical signal includes: adding the design overlay deviation value of the test group corresponding to the second optical signal and dividing by 2 to obtain the actual overlay deviation value.

[0012] Optionally, a plurality of the first test portions and a plurality of the second test portions are respectively formed on the dicing area of ​​the substrate.

[0013] Accordingly, the present invention also provides a detection structure for overlay accuracy, comprising: a substrate; a first film layer located on the substrate, the first film layer having a plurality of first test sections; a second film layer located on the first film layer, the second film layer having a plurality of second test sections corresponding to the first test sections respectively, a group of first test sections and a corresponding group of second test sections constituting a test group, and different test groups having different design overlay deviation values.

[0014] Optionally, the first test section includes: a plurality of first test pieces arranged along a first direction; the second test section includes: a plurality of second test pieces arranged along the first direction; the plurality of first test pieces have a first projection pattern on the substrate, the plurality of second test pieces have a second projection pattern on the substrate, and the second projection pattern is located between corresponding adjacent first projection patterns.

[0015] Optionally, the first direction is defined as the positive direction, and a first spacing value between the second projected image and the adjacent first projected image is obtained along the first direction; the second direction is defined as the negative direction, and the second direction is opposite to the first direction, and a second spacing value between the second projected image and the adjacent first projected image is obtained along the second direction; the sum of the first spacing value and the second spacing value is divided by 2 as the design overlay deviation value.

[0016] Optionally, the design overlay deviation values ​​between different test groups are increased in increments of 0.5 nm to 1 nm.

[0017] Optionally, a plurality of the first test sections and a plurality of the second test sections are respectively located on the dicing area of ​​the substrate.

[0018] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0019] In the overlay accuracy detection method of this invention, several test groups with different overlay deviation values ​​are designed. When the physical structure between the first and second test pieces in a certain test group shifts, resulting in projection overlap in the direction towards the substrate, the first optical signal used for detection is converted into the second optical signal. This detection process utilizes the objective physical characteristics between the first and second test pieces, reducing the influence of external factors such as device tilt and chemical mechanical polishing tilt, thus improving the accuracy of the overlay. Furthermore, because optical detection has strong penetrability, detection can be performed immediately after the formation of the second film layer, resulting in higher detection efficiency compared to electron microscopy and electrical detection, effectively shortening the detection cycle.

[0020] In the overlay accuracy detection structure of this invention, several test groups with different overlay deviation values ​​are designed. When the physical structure between the first and second test pieces in a certain test group shifts, resulting in projection overlap in the direction towards the substrate, the first optical signal used for detection is converted into a second optical signal. This detection process utilizes the objective physical characteristics between the first and second test pieces, reducing the influence of external factors such as device tilt and chemical mechanical polishing tilt, thus improving the accuracy of the overlay. Furthermore, because optical detection has strong penetrability, detection can be performed immediately after the second film layer is formed, resulting in higher detection efficiency compared to electron microscopy and electrical detection, effectively shortening the detection cycle. Attached Figure Description

[0021] Figure 1This is a flowchart of the method and structure for detecting overlay accuracy according to an embodiment of the present invention.

[0022] Figures 2 to 4 This is a schematic diagram of the steps in the overlay accuracy detection method in an embodiment of the present invention. Detailed Implementation

[0023] As described in the background section, there are still many problems with the existing overlay accuracy detection technology. These will be explained in detail below.

[0024] Current methods for detecting overlay accuracy typically include: measuring the distance between corresponding detection structures in the current layer and the previous layer, obtaining the corresponding offset optical signal, and then calculating the deviation value of the overlay accuracy based on the standard unit optical signal.

[0025] However, current processes can introduce several factors that affect the accuracy of overlay measurements, such as device tilt, chemical mechanical polishing (CMP) tilt, and grating imbalance. Taking the most complex example of device tilt, in some processes, the film thickness is significant, and the sidewalls of such thick films are typically tilted. When using measuring equipment to capture the boundary corresponding to the tilted sidewalls of the film, two problems arise: firstly, the boundary capture is uncertain, affecting the measurement results; secondly, the thick film may exhibit edge offset, meaning the measured distance value will also include errors caused by the film's own offset, thus reducing the accuracy of the obtained overlay precision.

[0026] Based on this, the present invention provides a method and structure for detecting overlay accuracy. By designing several test groups with different overlay deviation values, when the physical structure between the first and second test pieces in a certain test group shifts, resulting in projection overlap in the direction towards the substrate, the first optical signal used for detection will be converted into the second optical signal. This detection process utilizes the objective physical characteristics between the first and second test pieces, reducing the influence of external factors such as device tilt and chemical mechanical polishing tilt, thus improving the accuracy of overlay. Furthermore, because optical detection has strong penetrability, detection can be performed immediately after the formation of the second film layer, resulting in higher detection efficiency compared to electron microscopy and electrical detection, effectively shortening the detection cycle.

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] Figure 1This is a flowchart of the method for detecting overlay accuracy and its detection structure according to an embodiment of the present invention, including:

[0029] Step S101: Provide a substrate;

[0030] Step S102: A first film layer is formed on the substrate, and the first film layer has a plurality of first test sections.

[0031] Step S103: A second film layer is formed on the first film layer. The second film layer has a plurality of second test parts that correspond to the first test part respectively. A group of first test parts and a corresponding group of second test parts constitute a test group. Different test groups have different design overlay deviation values.

[0032] Step S104: Use a first optical signal to detect each test group, and when the first test part and the second test part in a certain test group have a projection overlap in the direction toward the substrate, the first optical signal is converted into a second optical signal.

[0033] Step S105: Obtain the test group corresponding to the transformation of the first optical signal into the second optical signal;

[0034] Step S106: Obtain the actual overlay deviation value based on the design overlay deviation value of the test group corresponding to the second optical signal.

[0035] The following describes in detail the steps of the method for detecting overlay accuracy and its detection structure, with reference to the accompanying drawings.

[0036] Figures 2 to 4 This is a schematic diagram of the steps of the overlay accuracy detection method and detection structure in an embodiment of the present invention.

[0037] Please refer to Figure 2 Substrate 100 is provided.

[0038] In this embodiment, the substrate 100 is made of silicon.

[0039] In other embodiments, the substrate material may also be germanium, silicon germanide, silicon carbide, gallium arsenide, or indium galliumide.

[0040] In this embodiment, the substrate 100 includes a device region I and a dicing region II, wherein the device region I is used to form a device structure with actual device functions, and the dicing region II is used to perform subsequent dicing processing to divide the wafer into several chips.

[0041] Please refer to Figure 3 , Figure 3This is a schematic diagram showing the first test section projected onto the substrate after omitting the substrate and magnifying it in the dicing area. A first film layer is formed on the substrate 100, and the first film layer has a plurality of sets of first test sections 101.

[0042] In this embodiment, the first test unit 101 includes: a plurality of first test pieces arranged along the first direction X1, and the plurality of first test pieces have a first projection pattern 101a on the substrate 100.

[0043] In this embodiment, a plurality of the first test portions 101 are respectively formed on the dicing region II of the substrate. Since the first test portions 101 are only used to detect the overlay accuracy and do not have actual device functions, by forming the first test portions 101 on the dicing region II, they can be removed by dicing after detection, thus avoiding occupying space in the device region I and reducing the integration density of the device structure.

[0044] Please refer to Figure 4 , Figure 4 and Figure 3 With the view direction consistent, a second film layer is formed on the first film layer. The second film layer has several sets of second test parts 102 corresponding to the first test part 101. A set of first test parts 101 and a corresponding set of second test parts 102 constitute a test group 103. Different test groups 103 have different design overlay deviation values ​​d. p .

[0045] It should be noted that in this embodiment, only two first test pieces are shown in the first test unit 101, and only one second test piece is shown in the second test unit 102.

[0046] In this embodiment, a plurality of second test sections 102 are respectively formed on the dicing region II of the substrate 100. Since the second test sections 102 are only used to detect overlay accuracy and do not have actual device functions, by forming the second test sections 102 on the dicing region II, they can be removed by dicing after detection, thus avoiding occupying space in the device region I and reducing the integration density of the device structure.

[0047] In this embodiment, the second test unit 102 includes: a plurality of second test pieces arranged along the first direction X1, the plurality of second test pieces having a second projection pattern 102a on the substrate 100, and the second projection pattern 102a being located between corresponding adjacent first projection patterns 101a.

[0048] In this embodiment, the first direction X1 is defined as the positive direction, and a first spacing value d1 between the second projected pattern 102a and the adjacent first projected pattern 101a is obtained along the first direction X1; the second direction X2 is defined as the negative direction, and the second direction X2 is opposite to the first direction X1, and a second spacing value d2 between the second projected pattern 102a and the adjacent first projected pattern 101a is obtained along the second direction X2; the sum of the first spacing value d1 and the second spacing value d2 divided by 2 is used as the design overlay deviation value d. p .

[0049] In one specific embodiment, when the absolute value of the first spacing d1 between the second projected pattern 102a and the adjacent first projected pattern 101a along the first direction X1 is 12 nanometers, it is denoted as 12 nanometers. Similarly, when the absolute value of the second spacing d2 between the second projected pattern 102a and the adjacent first projected pattern 101a along the second direction X2 is 12 nanometers, it is denoted as -12 nanometers. The corresponding design overlay deviation value d... p That is, (-12+12) / 2 = 0 nanometers.

[0050] In another specific embodiment, when the absolute value of the first spacing d1 between the second projected pattern 102a and the adjacent first projected pattern 101a along the first direction X1 is 14 nanometers, it is recorded as 14 nanometers. When the absolute value of the second spacing d2 between the second projected pattern 102a and the adjacent first projected pattern 101a along the second direction X2 is 10 nanometers, it is recorded as -10 nanometers. The corresponding design overlay deviation value d... p That is, (-10+14) / 2 = 2 nanometers.

[0051] In another specific embodiment, when the absolute value of the first spacing d1 between the second projected pattern 102a and the adjacent first projected pattern 101a along the first direction X1 is 8 nanometers, it is recorded as 8 nanometers. When the absolute value of the second spacing d2 between the second projected pattern 102a and the adjacent first projected pattern 101a along the second direction X2 is 16 nanometers, it is recorded as -16 nanometers. The corresponding design overlay deviation value d... p That is (-16+8) / 2 = -4 nanometers.

[0052] In this embodiment, the design overlay deviation value d between different test groups 103 p The increments are 0.5 nanometers to 1 nanometer.

[0053] It should be noted that the design overlay deviation value dp The smaller the increment step size, the higher the accuracy of the overlay, but the longer the detection time required; while the designed overlay deviation value d p The larger the increment step size, the lower the accuracy of the overlay, but the shorter the inspection time. In actual manufacturing processes, the step size can be adjusted according to the required overlay accuracy to achieve a balance between inspection accuracy and efficiency.

[0054] Please continue to refer to this. Figure 4 The first optical signal is used to detect each test group 103, and when the first test part 101 and the second test part 102 in a certain test group 103 have projection overlap in the direction toward the substrate 100, the first optical signal is converted into a second optical signal.

[0055] In this embodiment, the first optical signal is the optical signal used in Pupil Based Overlay (PBO) precision measurement technology.

[0056] In this embodiment, the first optical signal is a linear optical signal, and the second optical signal is a nonlinear optical signal. When the second test unit 102 projects onto the substrate 100, the corresponding physical and material structures undergo abrupt changes, causing abrupt changes in the optical response, which in turn causes the linear optical signal to abruptly transform into a nonlinear optical signal.

[0057] Please continue to refer to this. Figure 4 The test group 103 corresponding to the transformation from the first optical signal to the second optical signal is obtained, and the overlay deviation value d is determined according to the design of the test group 103 corresponding to the transformation from the first optical signal to the second optical signal. p Obtain the actual overlay deviation value d a .

[0058] In this embodiment, the design overlay deviation value d of the test group 103 corresponding to the converted second optical signal is used. p Obtain the actual overlay deviation value d a The method includes: converting the design overlay deviation value d of the test group 103 into the second optical signal. p Add the two numbers and divide by 2 to get the actual overlay deviation value d. a .

[0059] In one specific embodiment, when the design overlay deviation value d is detected... p The test group 103, corresponding to -4 nm and 4 nm, showed a change in optical signal, from which the actual overlay deviation value d can be calculated. aThe value is (-4+4) / 2 = 0 nanometers, meaning there was no overlay deviation.

[0060] In another specific embodiment, when the design overlay deviation value d is detected... p The test group 103, corresponding to -6 nm and 2 nm, showed a change in optical signal, from which the actual overlay deviation value d can be calculated. a The result is (-6+2) / 2 = -2 nanometers, which means that a 2-nanometer overlay deviation occurred in the second direction.

[0061] In yet another specific embodiment, when the design overlay deviation value d is detected... p The test group 103, corresponding to 8 nm and -4 nm, showed a change in optical signal, from which the actual overlay deviation value d can be calculated. a The value is (-4+8) / 2 = 2 nanometers, which means that a 2-nanometer overlay deviation occurred in the first direction.

[0062] In this embodiment, several sets of design overlay deviation values ​​d are designed. p In different test groups 103, when the physical structure between the first test piece and the second test piece in a certain test group 103 shifts, resulting in projection overlap in the direction toward the substrate 100, the first optical signal used for detection will be converted into the second optical signal. In this detection process, the objective physical characterization characteristics between the first test piece and the second test piece are utilized, reducing the influence caused by external factors such as device tilt and chemical mechanical polishing tilt, and improving the accuracy of overlay precision.

[0063] In addition, since optical detection has strong penetrability, it can be performed immediately after the second film layer is formed. Compared with electron microscopy scanning detection (which requires slicing) and electrical detection (which requires the fabrication of detection leads in the later process), it has higher detection efficiency and effectively shortens the detection cycle.

[0064] Accordingly, this embodiment of the invention also provides a detection structure for overlay accuracy; please refer to [further details]. Figure 4 The system includes: a substrate 100; a first film layer located on the substrate, the first film layer having a plurality of first test sections 101 therein; and a second film layer located on the first film layer, the second film layer having a plurality of second test sections 102 respectively corresponding to the first test sections 101. A group of first test sections 101 and a corresponding group of second test sections 102 constitute a test group 103. Different test groups 103 have different design overlay deviation values ​​d. p .

[0065] In this embodiment, several sets of design overlay deviation values ​​d are designed.p In different test groups 103, when the physical structure between the first test piece and the second test piece in a certain test group 103 shifts, resulting in projection overlap in the direction toward the substrate 100, the first optical signal used for detection will be converted into the second optical signal. In this detection process, the objective physical characterization characteristics between the first test piece and the second test piece are utilized, reducing the influence caused by external factors such as device tilt and chemical mechanical polishing tilt, and improving the accuracy of overlay precision.

[0066] In addition, since optical detection has strong penetrability, it can be performed immediately after the second film layer is formed. Compared with electron microscopy scanning detection (which requires slicing) and electrical detection (which requires the fabrication of detection leads in the later process), it has higher detection efficiency and effectively shortens the detection cycle.

[0067] In this embodiment, the first test unit 101 includes a plurality of first test pieces arranged along a first direction X1; the second test unit 102 includes a plurality of second test pieces arranged along the first direction X1; the plurality of first test pieces have a first projection pattern 101a on the substrate 100, and the plurality of second test pieces have a second projection pattern 102a on the substrate, and the second projection pattern 102a is located between corresponding adjacent first projection patterns 101a.

[0068] In this embodiment, the first direction X1 is defined as the positive direction, and a first spacing value d1 between the second projected pattern 102a and the adjacent first projected pattern 101a is obtained along the first direction X1; the second direction X2 is defined as the negative direction, and the second direction X2 is opposite to the first direction X1, and a second spacing value d2 between the second projected pattern 102a and the adjacent first projected pattern 101a is obtained along the second direction X2; the sum of the first spacing value d1 and the second spacing value d2 divided by 2 is used as the design overlay deviation value d. p .

[0069] In this embodiment, the design overlay deviation value d between different test groups 103 p The increments are 0.5 nanometers to 1 nanometer.

[0070] In this embodiment, a plurality of first test sections 101 and a plurality of second test sections 102 are respectively located on the dicing zone II of the substrate 100.

[0071] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for detecting overlay accuracy, characterized in that, include: Provide substrate; A first film layer is formed on the substrate, and the first film layer has a plurality of first test sections; A second film layer is formed on the first film layer. The second film layer has a plurality of groups of second test sections that are respectively corresponding to the first test section. A group of first test sections and a corresponding group of second test sections constitute a test group. Different test groups have different design overlay deviation values. A first optical signal is used to detect each test group, and when the first test part and the second test part in a certain test group have a projection overlap in the direction toward the substrate, the first optical signal is converted into a second optical signal. Obtain the test group corresponding to the transformation of the first optical signal into the second optical signal; The actual overlay deviation value is obtained based on the design overlay deviation value of the test group corresponding to the second optical signal. 2.The method of claim 1, wherein The first test section includes: a plurality of first test pieces arranged along a first direction; the second test section includes: a plurality of second test pieces arranged along the first direction; the plurality of first test pieces have a first projection pattern on the substrate, the plurality of second test pieces have a second projection pattern on the substrate, and the second projection pattern is located between corresponding adjacent first projection patterns.

3. The overlay accuracy detection method of claim 2, wherein, Define the first direction as the positive direction, and obtain the first spacing value between the second projected image and the adjacent first projected image along the first direction; The second direction is defined as the negative direction, which is opposite to the first direction. A second spacing value is obtained along the second direction between the second projected image and the adjacent first projected image. The sum of the first spacing value and the second spacing value is divided by 2 to obtain the design overlay deviation value.

4. The method of claim 1, wherein the overlay is a line overlay. The first optical signal includes: a linear optical signal.

5. The method of claim 1, wherein the overlay is a line overlay. The second optical signal includes: a nonlinear optical signal. 6.The method of claim 1, wherein The design overlay deviation values ​​between different test groups increase in increments of 0.5 nm to 1 nm.

7. The method for detecting overlay accuracy as described in claim 1, characterized in that, The method for obtaining the actual overlay deviation value based on the design overlay deviation value of the test group corresponding to the second optical signal includes: adding the design overlay deviation value of the test group corresponding to the second optical signal and dividing by 2 to obtain the actual overlay deviation value. 8.The method of claim 1, wherein A plurality of first test sections and a plurality of second test sections are respectively formed on the dicing area of ​​the substrate.

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