Stress monitoring device and method of manufacturing the same

A stress monitoring device includes an anchor structure, a freestanding structure and a Vernier structure. The anchor structure is over a substrate. The freestanding structure is over the substrate, wherein the freestanding structure is connected to the anchor structure and includes a free end suspended from the substrate. The Vernier structure is over the substrate and adjacent to the free end of the freestanding structure, wherein the Vernier structure comprises scales configured to measure a displacement of the free end of the freestanding structure.

BACKGROUND

Stress issue is critical to integrated circuit fabrication. High film stress would cause wafer warpage, and even cause wafer crack during fabrication. Conventional film stress measuring methodology is only applicable for bulk materials, but cannot be used to measure local film stress change after post heat treatment or after the film is patterned.

DETAILED DESCRIPTION

As used herein, the term “anchor” or “anchor structure” refers to a structure that is substantially immobile with respect to a substrate. The anchor or anchor structure may be formed directly or indirectly on the substrate, or may be a part of the substrate.

As used herein, the term “freestanding structure” is a structure that is connected to the anchor at one or more ends, and suspended from the substrate at least during fabrication. In some embodiments, the freestanding structure may be temporarily movable with respect to the substrate. For example, the freestanding structure is a beam structure including a free end mobile with respect to a Vernier structure to detect stress deviation. In some embodiments, the freestanding structure is immobile with respect to the Vernier structure after stress deviation information is obtained. In some embodiments, the freestanding structure is immobile with respect to the Vernier structure when one or more overlying is formed the freestanding structure.

As used herein, the term “Vernier structure” is a structure that is substantially immobile with respect to a substrate. In some embodiments, the Vernier structure is configured as a reference to measure a displacement of the freestanding structure.

In one or more embodiments of the present disclosure, a monitoring device such as a stress monitoring device includes an anchor structure, a freestanding structure and a Vernier structure. The freestanding structure is connected to the anchor structure includes a free end over the substrate. The Vernier structure includes scales to measure a displacement of the free end of the freestanding structure. The free end of the freestanding structure can be driven by stress changes to move relative to the scales of the Vernier, and thus a local stress can be monitored. The stress monitoring device is integratable with fabrication of integrated circuits such as semiconductor devices, MEMS devices, electronic devices or the like. In some embodiments, the stress monitoring device is configured to detect a local stress of a patterned structural layer that forms the freestanding structure and other structures or devices during fabrication. The stress monitoring device is formed from the structural layer, and thus can monitor the stress of the structural layer in real-time. For example, after the structural layer is patterned, or thermally treated, the stress monitoring device is responsive to the stress change as well, and thus can monitor current stress. The stress monitoring device can be formed at any positions of the substrate. In some embodiments, the stress monitoring device can be formed in some or each chip of the substrate to collect stress distribution throughout the substrate, and the stress distribution data can be helpful to modify manufacturing parameters, to alleviate wafer warpage, to avoid peeling or cracking issues, or the like. In some embodiments, the freestanding structure may be covered by at least one overlying layer and constrained by the at least one overlying layer in successive operations after the stress data is obtained. In some embodiments, the freestanding structure includes a test beam, a slope beam and an indicator beam. The test beam is connected to the first anchor at one end. The slope beam is connected to the second anchor at one end, and connected to the test beam at the other end. The indicator beam is connected to the slope beam at one end, and the indicator beam includes the free end pointing at the scales of the Vernier structure and being movable relative to the scales of the Vernier structure. In some embodiments of the present disclosure, a method of manufacturing a stress monitoring device is also provided, as discussed below.

FIG. 1is a flow chart illustrating a method for manufacturing a stress monitoring device according to various aspects of one or more embodiments of the present disclosure. The method100begins with operation110in which a substrate is provided. The method proceeds with operation120in which an anchor structure, a freestanding structure and a Vernier structure are formed over the substrate. The freestanding structure is connected to the anchor structure and includes a free end over the substrate. The Vernier structure is adjacent to the free end of the freestanding structure. The Vernier structure comprises scales configured to measure a displacement of the free end of the freestanding structure.

The method100is merely an example, and is not intended to limit the present disclosure beyond what is explicitly recited in the claims. Additional operations can be provided before, during, and after the method100, and some operations described can be replaced, eliminated, or moved around for additional embodiments of the method.

FIG. 2A,FIG. 2B,FIG. 2C,FIG. 2D,FIG. 2E,FIG. 2F,FIG. 2GandFIG. 2Hare schematic views at one of various operations of manufacturing a stress monitoring device according to one or more embodiments of the present disclosure. As depicted inFIG. 2A, a substrate10is received. In some embodiments, the substrate10includes a semiconductor substrate. By way of example, the material of the substrate10may include elementary semiconductor such as silicon or germanium; a compound semiconductor such as silicon germanium, silicon carbide, gallium arsenic, gallium phosphide, indium phosphide or indium arsenide; or combinations thereof. In some embodiments, structures or devices such as electronic structures or devices, semiconductor structures or devices, MEMS structures or devices or other structures or devices may be formed on or in the substrate10.

In some embodiments, a buffer layer12is formed over the substrate10. In some embodiments, the buffer layer12includes, but is not limited to, a dielectric layer or an insulative layer. In some embodiments, the buffer layer12at least partially covers the substrate10, or structures or devices formed on or in the substrate10for protection. In some embodiments, a material of the buffer layer12includes silicon oxide, silicon nitride, silicon oxynitride or the like. In some embodiments, a thickness of the buffer layer12is equal to or larger than about 2000 angstroms, but not limited thereto.

As depicted inFIG. 2B, a sacrificial layer14is formed over the substrate10. The sacrificial layer14is configured as a temporary protection layer or release layer, and will be removed in part or in whole. In some embodiments, the material of the sacrificial layer14is different from the material of the buffer layer12such that the buffer layer12can be maintained when the sacrificial layer14is removed. In some embodiments, the material of the sacrificial layer14includes, but is not limited to, semiconductive material such as polycrystalline silicon or the like. In some embodiments, a thickness of the sacrificial layer14is equal to or larger than about 4000 angstroms e.g. 2 micrometers, but not limited thereto.

As depicted inFIG. 2C, in some embodiments, one or more dimples14H recessed from a surface14T of the sacrificial layer14can be formed. In some embodiments, the dimple(s)14H can be formed e.g., by photolithography and etching techniques, but not limited thereto. In some embodiments, the dimple14H is recessed from the surface14T of the sacrificial layer14, but not through the sacrificial layer14.

As depicted inFIG. 2D, the sacrificial layer14is patterned to form a first portion141, a second portion142and a third portion143. In some embodiments, the sacrificial layer14is patterned e.g., by photolithography and etching techniques, but not limited thereto. In some embodiments, the first portion141, the second portion142and the third portion143can be connected or separated. For example, the first portion141may be separated from the second portion142and the third portion143, but not limited thereto. In some embodiments, the one or more dimples14H are located in the second portion142after the sacrificial layer14is patterned. In some embodiments, the etch rate of the sacrificial layer14is higher than the etch rate of the buffer layer12, and thus the buffer layer12can be reserved during patterning the sacrificial layer14to protect the substrate10or the structures or devices formed in or on the substrate10from being damaged. In some embodiments, a ratio of the etch rate of the sacrificial layer14to the etch rate of the buffer layer12may be higher than about 10 with respect to an etchant, but not limited thereto.

As depicted inFIG. 2E, a structural layer16is formed over the first portion141, the second portion142and the third portion143of the patterned sacrificial layer14. The material of the structural layer16is different from the material of the sacrificial layer14such that the structural layer16can be maintained when removing the sacrificial layer14. The material of the structural layer16may include, but is not limited to, a dielectric material, a conductive material such as metal, an insulative material, or any other suitable material different from that of the sacrificial layer14. In some embodiments, the structural layer16is further formed in the one or more dimples14H of the sacrificial layer14. In some embodiments, the structural layer16is single-layered. In some embodiments, the structural layer16may be multi-layered.

As depicted inFIG. 2F, the structural layer16is patterned to form a Vernier structure22having scales22S (also shown inFIG. 3) protruding out from the first portion141of the sacrificial layer14. In some embodiments, the first portion141, the second portion142and the third portion143of the sacrificial layer14are enclosed by the structural layer16after the scales22S are formed. In some embodiments, the structural layer16is patterned e.g., by photolithography and etching techniques, but not limited thereto.

As depicted inFIG. 2G, the structural layer16is patterned again to form a freestanding structure24over the second portion142and to form an anchor structure26over the third portion143. In some embodiments, the freestanding structure24exposes a portion of the second portion142. In some embodiments, one or more edges of the second portion142are exposed. In some embodiments, the anchor structure26encloses the third portion143. In some embodiments, the structural layer16is patterned e.g., by photolithography and etching techniques, but not limited thereto. In some embodiments, the structural layer16may be patterned to form through openings24T to expose a portion of the second portion142of the sacrificial layer14. The shape, dimension and spacing of the through openings24T may be configured based on the dimension of the freestanding structure24or other considerations as exemplarily disclosed in some embodiments ofFIG. 4orFIG. 5, but not limited thereto.

As depicted inFIG. 2H, the second portion142of the sacrificial layer14exposed from the freestanding structure24is removed such that the freestanding structure24is suspended and free from the substrate10, while the Vernier structure22and the anchor structure26are supported by the first portion141and the third portion143of the sacrificial layer14, respectively. In some embodiments, the first portion141and the third portion143of the sacrificial layer14are enclosed by the structural layer16, and thus can be maintained when removing the second portion142. In some embodiments, the second portion142of the sacrificial layer14is removed by etching such as vapor etching, but not limited thereto. By way of example, the sacrificial layer14is removed by XeF2vapor etching. In some embodiments, an etch rate of the sacrificial layer14is higher than an etch rate of the structural layer16with respect to an etchant such that the structural layer16can be undamaged. By way of example, a ratio of the etch rate of the sacrificial layer14to the etch rate of the structural layer16may be higher than about 10 with respect to an etchant, but not limited thereto. In some embodiments, the structural layer16located in the one or more dimples14H of the sacrificial layer14forms one or more bumps24B after the second portion142of the sacrificial layer14is removed. The one or more bumps24B protrude out from the freestanding structure24toward the substrate10or the buffer layer12. In some embodiments, the one or more bumps24B are configured to prevent the freestanding structure24from sticking to the substrate10or to the buffer layer12after removing the sacrificial layer. In some embodiments, the through openings24T of the structural layer16help to remove the second portion142of the sacrificial layer14more thoroughly. Accordingly, a stress monitoring device1of some embodiments of the present disclosure is fabricated.

FIG. 3is a schematic top view of a stress monitoring device according to one or more embodiments of the present disclosure. Referring toFIG. 3andFIG. 2H, the stress monitoring device1includes an anchor structure26, a freestanding structure24and a Vernier structure22. The freestanding structure24is connected to the anchor structure26, and includes a free end24F suspended from the substrate10. The Vernier structure22is adjacent to the free end24F of the freestanding structure24, and the Vernier structure22includes scales22S configured to measure a displacement of the free end24F of the freestanding structure24. In some embodiments, the anchor structure26includes a first anchor261and a second anchor262over the substrate10. In some embodiments, the first anchor261and the second anchor262are separated from each other. In some embodiments, the freestanding structure24includes one or more beams. In some embodiments, the freestanding structure24includes a test beam241, a slope beam242and an indicator beam243. In some embodiments, the test beam241is connected to the first anchor261. For example, the test beam241is connected to the first anchor261and extending along a first direction D1. In some embodiments, the slope beam242is connected to the second anchor262and the test beam241. In some embodiments, the slope beam242is connected to the second anchor262at one end, extended along a second direction D2, and connected to the test beam241at the other end. In some embodiments, the second direction D2is substantially perpendicularly to the first direction D1, but not limited thereto. The indicator beam243is connected to the slope beam242. In some embodiments, the indicator beam243is connected to the slope beam242at one end, and extended along the first direction D1. In some embodiments, the indicator beam243includes the free end24F suspended from the substrate10. In some embodiments, the free end24F of the indicator beam243points at the scales22S of the Vernier structure22and can be movable in response to local stress along the second direction D2relative to the scales22S of the Vernier structure22. In some embodiments, the free end24F of the indicator beam243moves to the left in response to a tensile stress, and moves to the right in response to a compressive stress.

In some embodiments, a stress of the stress monitoring device1can be measured by an equation:
σ=⅔*(E/1−v)(Lsb/Lib*Ltb)*δ, where

σ denotes stress of the stress monitoring device;

E denotes modulus of elasticity a material of the freestanding structure;

v denotes Poisson ratio of the material of the freestanding structure;

Lsb denotes length of the slope beam;

Lib denotes length of the indicator beam;

Ltb denotes length of the test beam; and

δ denotes displacement of the free end measured by the Vernier structure.

In some embodiments, the stress monitoring device1is configured to detect a local stress of a patterned structural layer16that forms the freestanding structure24and other structures or devices during fabrication. The stress monitoring device1is formed from the structural layer16, and thus can monitor the stress of the structural layer16in real-time. For example, after the structural layer16is patterned, or thermally treated, the stress monitoring device1is responsive to the stress change as well and thus can real-time monitor stress changes. The stress monitoring device1can be formed at any positions of the substrate10. In some embodiments, the stress monitoring device1can be formed in some or each chip (cell) of the substrate10to collect stress distribution throughout the substrate10, and the stress distribution data can be helpful to modify manufacturing parameters, to alleviate wafer warpage, to avoid pealing or cracking issues, or the like. In some embodiments, two or more stress monitoring devices1may be oriented in different directions for monitoring stresses in different directions.

The stress monitoring device of the present disclosure is not limited to the above-mentioned embodiments, and may have other different embodiments. To simplify the description and for the convenience of comparison between each of the embodiments of the present disclosure, the identical components in each of the following embodiments are marked with identical numerals. For making it easier to compare the difference between the embodiments, the following description will detail the dissimilarities among different embodiments and the identical features will not be redundantly described.

FIG. 4is a schematic partial top view of a freestanding structure according to one or more embodiments of the present disclosure. Referring toFIG. 4andFIG. 2G,FIG. 2HandFIG. 3, the partial top view may illustrate any part of the freestanding structure24such as the test beam241, the slope beam242, the indicator beam243or a combination thereof. In some embodiments, the freestanding structure24includes through openings24T penetrating the structural layer16and exposing the second portion142of the sacrificial layer14. In some embodiments, the through openings24T are configured to help to remove the second portion142of the sacrificial layer14more thoroughly, as discussed previously. The shape, dimension and spacing of the through openings24T may be configured based on the dimension of the freestanding structure24or other considerations. In some embodiments, the length of a beam such as the test beam241is about 500 micrometers, but not limited thereto. In some embodiments, the shape and the dimension of the through openings24T may be substantially the same. In some embodiments, the through opening24T includes a slot shape, with a length of about 10 micrometers and a width of about 3 micrometers, but not limited thereto. In some embodiments, a spacing between two adjacent through openings24T in a length direction is about 5 micrometers, and a spacing between two adjacent through openings24T in a width direction is about 5.25 micrometers, but not limited thereto.

FIG. 5is a schematic partial top view of a freestanding structure according to one or more embodiments of the present disclosure. Referring toFIG. 5andFIG. 2G,FIG. 2HandFIG. 3, in some embodiments, the length of a beam such as the test beam241is about 750 micrometers or 1500 micrometers, but not limited thereto. The through openings24T may include different dimensions. In some embodiments, a portion of the through openings24T has smaller dimension, while another portion of the through openings24T has larger dimension. In some embodiments, a portion of the through openings24T adjacent to edge of the freestanding structure24includes a smaller slot shape, which a length of about 5 micrometers, and a width of about 3 micrometers. In some embodiments, another portion of the through openings24T adjacent to middle of the freestanding structure24includes a larger slot shape, which a length of about 10 micrometers, and a width of about 3 micrometers. In some embodiments, a spacing between two adjacent through openings24T in a length direction is about 5 micrometers, and a spacing between two adjacent through openings24T in a width direction is about 5.25 micrometers, but not limited thereto.

FIG. 6is a schematic partial top view of a freestanding structure according to one or more embodiments of the present disclosure. Referring toFIG. 6with reference toFIG. 2G,FIG. 2HandFIG. 3, a connection24C between different portions of the freestanding structure24may has a rounding corner. In some embodiments, at least one of a connection24C between the test beam241and the slope beam242has a rounding corner and a connection24C between the slope beam242and the indicator beam243has a rounding corner. In some embodiments, the rounding corner is configured to avoid local stress concentration, and alleviate cracking.

FIG. 7is a schematic cross-sectional view of a stress monitoring device according to one or more embodiments of the present disclosure. As shown inFIG. 7, different from the stress monitoring device1ofFIGS. 2-3, the stress monitoring device2of some embodiments further include at least one overlying layer30covering the freestanding structure24. In some embodiments, the at least one overlying layer30may further cover the anchor structure26and/or the Vernier structure26. In some embodiments, the at least one overlying layer30may partially or entirely constrain the freestanding structure24from moving. In some embodiments, the stress data during fabrication has been obtained, and thus the freestanding structure24can be covered and constrained by the at least one overlying layer30. In some embodiments, the at least one overlying layer30may cover a portion of the freestanding structure24. In some embodiments, the at least one overlying layer30may enclose the freestanding structure24. In some embodiments, the material of the at least one overlying layer30may include insulative material, conductive material, semiconductor material, or a combination thereof. In some embodiments, although the freestanding structure24may be constrained by the at least one overlying layer30from moving, the stress monitoring device2may have been used to detect stress during fabrication before the at least one overlying layer30is formed.

In some embodiments of the present disclosure, the stress monitoring device is configured to detect a local stress of a patterned structural layer. The stress monitoring device is formed from the structural layer, and thus can monitor the stress of the structural layer in real-time. For example, after the structural layer is patterned, thermally treated or undergone other treatment, the stress monitoring device is responsive to the stress change and thus can real-time monitor stress changes. The stress monitoring device can be formed at any positions of the substrate. In some embodiments, the stress monitoring device can be formed in some or each chip (cell) of the substrate to collect stress distribution throughout the substrate and the stress distribution data can be helpful to modify manufacturing parameters, to alleviate wafer warpage, to avoid peeling or cracking issues, or the like. In some embodiments, two or more stress monitoring devices may be oriented in different directions for monitoring stresses in different directions.

In one exemplary aspect, a stress monitoring device includes an anchor structure, a freestanding structure and a Vernier structure. The anchor structure is over a substrate. The freestanding structure is over the substrate, wherein the freestanding structure is connected to the anchor structure and includes a free end over the substrate. The Vernier structure is over the substrate and adjacent to the free end of the freestanding structure, wherein the Vernier structure comprises scales configured to measure a displacement of the free end of the freestanding structure.

In another aspect, a stress monitoring device includes a first anchor, a second anchor, a freestanding structure and a Vernier structure. The first anchor and the second anchor are over the substrate. The freestanding structure is over the substrate, wherein the freestanding structure includes a test beam, a slope beam and an indicator beam. The test beam is connected to the first anchor at one end. The slope beam is connected to the second anchor at one end, and connected to the test beam at the other end. The indicator beam is connected to the slope beam at one end, and extending along the first direction, wherein the indicator beam includes a free end suspended from the substrate. The Vernier structure is over the substrate, wherein the Vernier structure includes scales facing the free end of the indicator beam and configured to measure a displacement of the free end of the freestanding structure.

In yet another aspect, a method for manufacturing a stress monitoring device is provided. A substrate is provided. An anchor structure, a freestanding structure and a Vernier structure are formed over the substrate. The freestanding structure is connected to the anchor structure and includes a free end suspended from the substrate. The Vernier structure is adjacent to the free end of the freestanding structure. The Vernier structure includes scales configured to measure a displacement of the free end of the freestanding structure.