TW201916247A - Method of fabricating isolation structure - Google Patents

Abstract

A method of fabricating an isolation structure is provided. The method includes the following steps. A substrate having a trench is provided. A first insulation layer is formed on the substrate. The first insulation layer fills in the trench and covers the surface of the substrate. A shielding layer is formed on the first insulation layer. The shielding layer is located at the corresponding position over the trench. A second insulation layer is formed on the first insulation layer and the shielding layer. A first removal process is performed to remove the second insulation layer and a portion of the first insulation layer on the shielding layer with the shielding layer as a stop layer. A second removal process is performed to remove the shielding layer and a portion of the first insulation layer outside the trench.

Description

Method of manufacturing isolation structure

The present invention is directed to a method of making an isolation structure.

The shallow trench isolation (STI) structure has good isolation effect and small occupied area, and is commonly used as an isolation structure for isolating adjacent transistors in a semiconductor. However, in the process of the isolation structure, due to the influence of the loading effect, in the region with a large width, the problem of dishing is easily generated, so that the uniformity of the surface of the formed isolation structure is poor, thereby affecting Subsequent processes can even affect the reliability of components. Therefore, how to avoid the problem of dishing and increase the flatness of the isolation structure is one of the issues that current R&D personnel need to solve.

The present invention provides a method of fabricating an isolation structure such that the isolation structure formed has good flatness.

The present invention provides a method of fabricating an isolation structure that includes the following steps. A substrate is provided with a trench in the substrate. A first insulating layer is formed on the substrate. The first insulating layer is filled in the trench and covers the surface of the substrate. A shielding layer is formed on the first insulating layer. The shielding layer is located at a corresponding position above the trench. A second insulating layer is formed on the first insulating layer and the shielding layer. Taking the shielding layer as a stopping layer, a first removing process is performed to remove the second insulating layer and a portion of the first insulating layer located above the shielding layer. A second removal process is performed to remove the masking layer and the first insulating layer outside the trench.

In some embodiments of the invention, the forming of the trench comprises the following steps. A hard mask layer is formed on the substrate. The hard mask layer is patterned to form a patterned hard mask layer having an opening that exposes a portion of the substrate. A patterned hard mask layer is used as a mask to remove a portion of the exposed substrate to form a trench.

In some embodiments of the present invention, the second removal process uses the patterned hard mask layer as a stop layer, and the top surface of the first insulating layer after removal and the top of the patterned hard mask layer The face is flush.

In some embodiments of the invention, the hard mask layer comprises a single layer structure or a multilayer structure.

In some embodiments of the invention, the patterning mask layer is removed after the second removal process described above.

In some embodiments of the present invention, after forming the trench and before forming the first insulating layer, further comprising forming a liner on the surface of the trench and forming a protective layer on the surface of the liner.

In some embodiments of the invention, the protective layer comprises tantalum nitride, a buffer layer, an amorphous germanium, or a combination thereof.

In some embodiments of the invention, the first insulating layer has a recess. The groove is located at a corresponding position above the trench, wherein the shielding layer is formed in the groove.

In some embodiments of the invention, forming the masking layer includes forming a masking material layer on the first insulating layer, and patterning the masking material layer.

In some embodiments of the invention, the thickness of the second insulating layer is greater than or equal to the thickness of the first insulating layer.

In some embodiments of the invention, forming the first insulating layer and the second insulating layer includes performing a flowable chemical vapor deposition process and an annealing process.

In some embodiments of the invention, the removal rate of the first removal process is greater than the removal rate of the second removal process.

In some embodiments of the present invention, the first removal process and the second removal process include an abrasive polishing process, wherein the rotation speed of the first removal process is greater than the rotation speed of the second removal process.

Based on the above, in the process of the isolation structure of the present invention, a shielding layer is formed between the first insulating material and the second insulating material, and a two-stage removal process is utilized to form the isolation structure. The resulting isolation structure thus has a flat surface.

The above described features and advantages of the invention will be apparent from the following description.

Reference will now be made in detail to the exemplary embodiments embodiments In the following various embodiments, the same component symbols are used to denote the same components in the drawings and the description, and the materials, formation methods, and the like are not repeatedly mentioned for the sake of brevity. In addition, the drawings of the present invention are only schematic diagrams and are not drawn in accordance with actual scales.

1A-1G are schematic cross-sectional views showing a flow of a method of fabricating an isolation structure in accordance with some embodiments of the present invention.

Referring to Figure 1A, a substrate 10 is provided. The substrate 10 is, for example, a semiconductor substrate. The semiconductor substrate can be a doped germanium substrate or an undoped germanium substrate. The erbium-doped dopant may be a P-type dopant, an N-type dopant, or a combination thereof. In some embodiments, the substrate 10 is a bulk substrate, but the invention is not limited thereto. In other embodiments, the substrate 10 can also be a silicon-on-insulator (SOI) substrate.

A hard mask layer 13 is formed on the substrate 10. The hard mask layer 13 may be a single layer structure or a multilayer structure. The material of the hard mask layer 13 is an insulating material such as an oxide, a nitride, an oxynitride or a combination thereof. In some embodiments, the hard mask layer 13 comprises hafnium oxide, tantalum nitride, hafnium oxynitride or a combination thereof. The method of forming the hard mask layer 13 includes a chemical vapor deposition method, a thermal oxidation method, or a combination thereof.

In some embodiments, the hard mask layer 13 is a two-layer structure that includes a first material layer 11 and a second material layer 12. The materials and thicknesses of the first material layer 11 and the second material layer 12 may be the same or different. In some embodiments, the first material layer 11 is also referred to as a mat layer, the material of which includes yttrium oxide. The material of the second material layer 12 is tantalum nitride. In some embodiments, the thickness T1 of the second material layer 12 ranges from 50 angstroms to 1000 angstroms.

Referring to FIG. 1A, a patterned mask layer 14 is formed on the hard mask layer 13. The patterned mask layer 14 has a plurality of openings 14a that expose a portion of the hard mask layer 13. The width of each opening 14a may be the same or different. The patterned mask layer 14 is, for example, a patterned photoresist layer.

Referring to FIG. 1A and FIG. 1B, the patterned mask layer 14 is used as a mask to remove the hard mask layer 13 exposed by the opening 14a, for example, by etching to form a patterned hard mask layer 13a. The patterned hard mask layer 13a includes a patterned first material layer 11a and a patterned second material layer 12a. The patterned hard mask layer 13a has a plurality of openings 15 that expose a portion of the substrate 10. Next, with the patterned mask layer 14 and the patterned hard mask layer 13a as a mask, a portion of the substrate 10 exposed by the opening 15 is removed, for example, by etching to form a plurality of trenches 16 in the substrate 10. . The depth of the trench 16 ranges, for example, from 1000 angstroms to 3,000 angstroms. The width of the trench 16 is, for example, greater than 1 micron. The width of each trench 16 may be the same or different. Thereafter, the patterned mask layer 14 is removed. The way to remove is, for example, an ashing process.

Referring to FIG. 1C, a liner layer 17 and a protective layer 18 are selectively formed on the surface of the substrate 10. The liner 17 is filled into the trench 16 to cover the bottom surface and side walls of the trench 16. The material of the lining layer 17 is, for example, cerium oxide, and the method of forming it is, for example, a thermal oxidation method. The thermal oxidation method includes a wet thermal oxidation method. A protective layer 18 is then formed on the surface of the liner 17 and the sidewalls of the patterned hard mask layer 13a. The protective layer 18 is filled into the trench 16 and the opening 15 to cover the sidewall of the patterned hard mask layer 13a and the bottom surface and sidewall of the liner layer 17. The material of the protective layer 18 includes tantalum nitride, tantalum buffer layer, amorphous germanium or a combination thereof, but the invention is not limited thereto. The method of forming the protective layer 18 comprises first forming a protective material layer on the surface of the liner 17 and the patterned mask layer 13a by a suitable deposition method, such as chemical vapor deposition, followed by a planarization process, and the removal is located in the patterning. The protective material layer on the top surface of the mask layer 13a exposes the patterned mask layer 13a. In some embodiments, the top surface of the patterned mask layer 13a is substantially flush with the top surface of the protective layer 18. The top surface of the lining layer 17 is covered by the protective layer 18 and is substantially flush with the top surface of the substrate 10, but the invention is not limited thereto.

In other embodiments, the liner 17 covers the sidewalls and bottom surface of the trench 16 of the substrate 10 and extends to cover the sidewalls of the patterned mask layer 13a. That is, the liner 17 is located between the substrate 10 and the protective layer 18, and between the patterned mask layer 13a and the protective layer 18. In these embodiments, the method of forming the liner 17 includes a suitable deposition method such as atomic layer chemical vapor deposition. The method of forming the liner 17 includes forming a layer of a liner material prior to formation of the layer of protective material. A layer of lining material is filled into the trench 16 and the opening 15 to cover the surface of the substrate 10 and the patterned mask layer 13a, and then removed while removing the protective material layer on the top surface of the patterned mask layer 13a in the planarization process. A layer of lining material other than the top surface of the patterned mask layer 13a is exposed to expose the patterned mask layer 13a. In some embodiments, the top surface of the liner layer 17, the top surface of the protective layer 18, and the top surface of the patterned mask layer 13a are substantially flush.

Referring to FIG. 1C, a first insulating layer 19 is formed on the substrate 10. The material of the first insulating layer 19 is different from the material of the patterned mask layer 13a. In some embodiments, the first insulating layer 19 comprises hafnium oxide. The method of forming the first insulating layer 19 includes a suitable deposition method such as a chemical vapor deposition method, a flowable chemical vapor deposition (FCVD), or a combination thereof. In some embodiments, after the first insulating layer 19 is formed by FCVD, the first annealing process is further included. The temperature of the first annealing process ranges from 500 ° C to 1100 ° C. In some embodiments, the first insulating layer 19 has a thickness ranging from 1000 angstroms to 1500 angstroms.

The first insulating layer 19 is filled in the trench 16 and the opening 15 to cover the surface of the patterned mask layer 13a and the substrate 10. In some embodiments, the topography of the first insulating layer 19 is similar to the topography of the surface of the substrate 10 and the patterned hard mask layer 13a, that is, the first insulating layer 19 is formed by the substrate 10 and the patterned hard mask layer. 13a has a trench 16 and an opening 15 and has an uneven landform. Specifically, the first insulating layer 19 is formed in the trench 16 and the opening 15 and protrudes from the top surface of the substrate 10 and the patterned mask layer 13a, and has a groove at a corresponding position above the trench 16 and the opening 15. 20. The bottom surface of the recess 20 is higher than the top surface of the patterned mask layer 13a. The width of the groove 20 depends on the width of the trench 16. In some embodiments, the width of the groove 20 is substantially equal to or slightly less than the width of the trench 16.

Referring to FIG. 1C, a shielding layer 21 is formed on the first insulating layer 19. The shielding layer 21 is formed in the recess 20 to cover the bottom surface and a portion of the sidewall of the recess 20. That is, the shielding layer 21 is located at a corresponding position above the trench 16 of the substrate 10. The width of the shielding layer 21 is substantially equal to or slightly smaller than the width of the trench 16.

The material of the shielding layer 21 is different from the material of the first insulating layer 19. The material of the shielding layer 21 may be the same as or different from the material of the patterned hard mask layer 13a. In some embodiments, the material of the masking layer 21 comprises an insulating material such as tantalum nitride, hafnium oxynitride, niobium nitrite, tantalum boride (BNSIN), or a combination thereof. The thickness T2 of the shielding layer 21 ranges, for example, from 5 angstroms to 30 angstroms. The method of forming the shielding layer 21 includes first forming a masking material layer on the first insulating layer 19. In some embodiments, the layer of masking material is a layer of conformal masking material (ie, having a similar topography as the first insulating layer 19), the method of forming comprising a suitable deposition method, such as chemical vapor deposition or atomic Layer chemical vapor deposition. The masking material layer covers the surface of the first insulating layer 19. Thereafter, the masking material layer is patterned to remove the masking material layer that is outside the recess 20 of the first insulating layer 19 and partially covers the sidewalls of the recess 20. Patterning methods include lithography and etching.

In some embodiments, there is a portion of the first insulating layer 19 between the masking layer 21 and the patterned mask layer 13a. The distance S between the bottom surface of the shielding layer 21 and the top surface of the patterned mask layer 13a ranges, for example, from 100 angstroms to 500 angstroms.

Referring to FIG. 1D, a second insulating layer 22 is formed on the first insulating layer 19 and the shielding layer 21. The material of the second insulating layer 22 is different from the material of the shielding layer 21, but may be the same as or different from the material of the first insulating layer 19. In some embodiments, the material of the second insulating layer 22 includes hafnium oxide. The method of forming the second insulating layer 22 includes a suitable deposition method such as chemical vapor deposition or flowable chemical vapor deposition (FCVD). In some embodiments, after the second insulating layer 22 is formed by FCVD, the second annealing process is further included. The temperature of the second annealing process may be the same as or different from the temperature of the first annealing process. In some embodiments, the temperature of the second annealing process is lower than or equal to the temperature of the first annealing process. The temperature range of the second annealing process is, for example, 300 ° C to 500 ° C.

With continued reference to FIG. 1D, in some embodiments, the topography of the second insulating layer 22 is similar to that of the first insulating layer 19, and also has an uneven topography that also has grooves at corresponding locations above the recess 20. The thickness of the second insulating layer 22 is greater than or equal to the thickness of the first insulating layer 19. In some embodiments, the second insulating layer 22 has a thickness ranging from 1500 angstroms to 2000 angstroms. The second insulating layer 22 together with the first insulating layer 19 constitutes an insulating structural material layer 23. A shielding layer 21 is formed in the insulating structural material layer 23. In some embodiments, the thickness of the isolating structural material layer 23 ranges from 2,500 angstroms to 3,500 angstroms. In an exemplary embodiment, the thickness of the isolating structural material layer 23 is 3000 angstroms, wherein the first insulating layer 19 has a thickness of 1000 angstroms and the second insulating layer 22 has a thickness of 2000 angstroms.

Referring to FIG. 1D to FIG. 1E , with the shielding layer 21 as a stopping layer, a first removing process is performed to remove the second insulating layer 22 and a portion of the first insulating layer 19 above the shielding layer 21 to form a first insulation. Layer 19a (isolation structure material layer 23a). In some embodiments, the first removal process includes a planarization process, such as a polishing process. The grinding and polishing process includes a chemical mechanical polish (CMP) process. The polishing slurry used has a high polishing selectivity ratio between the insulating structural material layer 23 and the shielding layer 21 during the polishing and polishing process. In an exemplary embodiment, the spacer selection ratio of the spacer structure material layer 23 to the mask layer 21 is 28.

Referring to FIG. 1E, since the shielding layer 21 serves as a stopping layer in the first removing process, the first insulating layer 19 under the shielding layer 21 can be protected without being removed. That is to say, under the protection of the shielding layer 21, the first insulating layer 19 located in the trench 16 and the opening 15 does not cause a problem of dishing. In some embodiments, the top surface of the first insulating layer 19a is flush with the top surface of the shielding layer 21, but the invention is not limited thereto. In other embodiments, the top surface of the first insulating layer 19a between the shielding layers 21 is slightly lower than the top surface of the shielding layer 21.

Referring to FIG. 1E to FIG. 1F , the patterned mask layer 13 a is used as a stop layer, and a second removal process is performed to remove the shielding layer 21 and a portion of the first insulating layer 19 a located outside the trench 16 and the opening 15 . That is, the first insulating layer 19a located above the patterned mask layer 13a is removed, and the first insulating layer 19b (i.e., the isolating structural material layer 23b) is formed. The second removal process includes a planarization process, such as an abrasive polishing process. The grinding and polishing process includes a chemical mechanical polishing process.

The removal rate of the first removal process may be equal to or greater than the removal rate of the second removal process. In some embodiments, the removal rate of the first removal process is greater than the removal rate of the second removal process. In some embodiments in which the first removal process and the second removal process include an abrasive polishing process, the first removal process may be the same as or different from the slurry used in the second removal process. The rotation speed of the first removal process is greater than or equal to the rotation speed of the second removal process. Here, the rotational speed refers to the rotational speed of the polish head at the time of grinding and the rotational speed of the platen of the grinder. In some embodiments, the first removal process is a high speed grinding process with a rotational speed greater than 50 rpm/min; the second removal process is a low rotational speed grinding process with a rotational speed of less than 50 rpm/min. In some exemplary embodiments, the first removal process has a rotational speed ranging from 50 rpm/min to 130 rpm/min; and the second removal process has a rotational speed ranging from 20 rpm/min to 50 rpm/min.

Referring to FIG. 1F, the first insulating layer 19b (ie, the isolating structural material layer 23b) is located in the trench 16 of the substrate 10 and the opening 15 of the patterned mask layer 13a. In some embodiments, the top surface of the first insulating layer 19b (ie, the isolating structural material layer 23b) is substantially flush with the top surface of the patterned mask layer 13a.

Referring to FIG. 1F and FIG. 1G, the patterned mask layer 13a is removed, for example, by etching to expose the top surface of the substrate 10. Etching includes wet etching. The etchant used in the wet etching includes, for example, hot phosphoric acid, hydrofluoric acid, or a combination thereof. In some embodiments, during the removal of the patterned mask layer 13a, a portion of the first insulating layer 19b is also removed and a first insulating layer 19c is formed. The first insulating layer 19c is located between the substrates 10, that is, the isolation structure 23c is formed. The isolation structure 23c has a flat surface. In some embodiments, the top surface of the isolation structure 23c is substantially flush with the top surface of the substrate 10, but the invention is not limited thereto. In other embodiments, the top surface of the isolation structure 23c may also protrude from the top surface of the substrate 10.

In summary, in the embodiment of the present invention, the shielding layer is buried in the insulating material layer as the isolation structure, and the two-stage removal process is used to form the isolation structure. The shielding layer is located above the base trench, and can be used as a stopping layer during the first removal process to protect the underlying insulating material layer from being recessed by the insulating material layer above the trench. While performing the second removal process, the patterned mask layer on the substrate can serve as a stop layer to remove the mask layer and a small amount of the first insulating layer. This allows the formed isolation structure to have a flat surface.

Although the present invention has been disclosed above by way of example, it is not intended to limit the invention. The scope of the present invention is defined by the scope of the appended claims, unless otherwise claimed.

10‧‧‧Base

11‧‧‧First material layer

11a‧‧‧ patterned first material layer

12‧‧‧Second material layer

12a‧‧‧ patterned second material layer

13‧‧‧hard mask layer

13a‧‧‧ patterned hard mask layer

14‧‧‧ patterned mask layer

14a, 15‧‧‧ openings

16‧‧‧ditch

17‧‧‧ lining

18‧‧‧Protective layer

19, 19a, 19b, 19c‧‧‧ first insulation

20‧‧‧ Groove

21‧‧‧Shielding layer

22‧‧‧Second insulation

23, 23a, 23b‧‧‧ isolation structural material layer

23c‧‧‧Isolation structure

T1, T2‧‧‧ thickness

S‧‧‧ distance

1A-1G are schematic cross-sectional views showing a flow of a method of fabricating an isolation structure in accordance with some embodiments of the present invention.

Claims (13)

A method of fabricating an isolation structure, comprising: providing a substrate having a trench therein; forming a first insulating layer on the substrate, the first insulating layer filling in the trench and covering the substrate Forming a shielding layer on the first insulating layer, the shielding layer is located at a corresponding position above the trench; forming a second insulating layer on the first insulating layer and the shielding layer; Using a shielding layer as a stopping layer, performing a first removing process, removing a second insulating layer and a portion of the first insulating layer above the shielding layer; and performing a second removal process to remove the shielding layer And a portion of the first insulating layer located outside the trench. The method of manufacturing the isolation structure of claim 1, wherein the forming the trench comprises: forming a hard mask layer on the substrate; patterning the hard mask layer to form a pattern having an opening a hard mask layer, the opening exposes a portion of the substrate; and the patterned hard mask layer is used as a mask to remove a portion of the substrate exposed by the opening to form the trench. The method of manufacturing the isolation structure of claim 2, wherein the second removal process uses the patterned hard mask layer as a stop layer, and the first insulating layer after removal The top surface is flush with the top surface of the patterned hard mask layer. The method of manufacturing an isolation structure according to claim 2, wherein the hard mask layer comprises a single layer structure or a multilayer structure. The method of fabricating the isolation structure of claim 2, further comprising removing the patterned mask layer after the second removal process. The method of manufacturing the isolation structure of claim 2, wherein after forming the trench, and before forming the first insulating layer, further comprising forming a liner on a surface of the trench, and A protective layer is formed on the surface of the liner. The method of manufacturing an isolation structure according to claim 6, wherein the protective layer comprises tantalum nitride, a buffer layer, an amorphous germanium or a combination thereof. The method of manufacturing the isolation structure of claim 1, wherein the first insulating layer has a groove, and the groove is located at a corresponding position above the trench, wherein the shielding layer is formed on the In the groove. The method of fabricating the isolation structure of claim 8, wherein the forming the shielding layer comprises: forming a masking material layer on the first insulating layer; and patterning the masking material layer. The method of manufacturing the isolation structure of claim 1, wherein the thickness of the second insulating layer is greater than or equal to the thickness of the first insulating layer. The method of fabricating the isolation structure of claim 1, wherein the forming the first insulating layer and the second insulating layer comprises performing a flowable chemical vapor deposition process and an annealing process. The method of manufacturing the isolation structure of claim 1, wherein the removal rate of the first removal process is greater than the removal rate of the second removal process. The method of manufacturing the isolation structure of claim 12, wherein the first removal process and the second removal process comprise an abrasive polishing process, wherein a rotational speed of the first removal process is greater than The second removal process speed.