Metal connection hole and forming method thereof

Abstract

The present invention provides a metal connection hole and a method for forming the same. By adding a second etch-stop layer, also known as a buffer layer, between a second dielectric layer and a third dielectric layer, the second etch-stop layer acts as a barrier when etching the upper metal layer trench, preventing plasma over-etching of the second dielectric layer at right angles to the upper metal layer trench, thereby preventing the formation of an inclined metal connection hole morphology. Furthermore, the second etch-stop layer can define the depth of the upper metal layer trench, and thus the depth of the upper metal layer. Similarly, the second etch-stop layer can also define the depth of the metal connection hole, avoiding the need to rely on two unstable parameters, etching time and etching rate, to control the depth of the second trench and the depth of the metal connection hole.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a metal connection hole and a method for forming the same. Background Art

[0002] When the critical size of the chip falls below 90nm, the metal connections in the back end adopt copper wire technology. Since its copper wire structure is similar to the "Damask structure", the copper wire technology is also called the "Damask" technology. Figure 1 This is a SEM image of a metal connection hole in the prior art. In the copper wire process, the upper metal layer trench etching and the metal connection hole etching are completed by a one-step etching method. However, the existing one-step method will cause the top morphology of the metal connection hole 100 to be tilted, such as Figure 1 As shown, vertical connection holes cannot be formed. Summary of the Invention

[0003] The object of the present invention is to provide a metal connection hole and a method for forming the same, so as to solve the problem of the inclined top morphology of the metal connection hole.

[0004] To solve the above technical problems, the present invention provides a method for forming a metal connection hole, comprising:

[0005] Providing a substrate, on which a first dielectric layer and a lower metal layer located in the first dielectric layer are formed, and a first etch stop layer, a second dielectric layer, a second etch stop layer, and a third dielectric layer are sequentially formed on the lower metal layer and the first dielectric layer;

[0006] forming a first trench and a first through-hole, wherein the first trench penetrates the third dielectric layer and stops on the second etch-stop layer, the first through-hole penetrates the second etch-stop layer and the second dielectric layer and stops on the first etch-stop layer, and the first trench and the first through-hole are in communication;

[0007] The first groove is etched to form a second groove, and the first through hole is etched to form a second through hole at the same time, the second groove penetrates the third dielectric layer and the second etch stop layer, the second through hole penetrates the second dielectric layer and the first etch stop layer and exposes the lower metal layer, the second groove constitutes an upper metal layer groove, and the second through hole constitutes a metal connection hole.

[0008] Optionally, the thickness of the second etch stop layer is less than or equal to the thickness of the first etch stop layer.

[0009] Optionally, the first etch stop layer and the second etch stop layer are made of nitrogen-doped silicon carbide.

[0010] Optionally, the dielectric constants of the first etch stop layer and the second etch stop layer are 2.8 to 3.3.

[0011] Optionally, the first dielectric layer, the second dielectric layer and the third dielectric layer are made of black diamond.

[0012] Optionally, the step of forming the first trench and the first through hole includes:

[0013] forming a fourth dielectric layer, a patterned barrier layer, an anti-reflection layer and a patterned photoresist layer in sequence on the third dielectric layer;

[0014] Using the patterned photoresist layer as a mask, etching the anti-reflection layer and the fourth dielectric layer to form a first opening, wherein the first opening penetrates the anti-reflection layer and the fourth dielectric layer and exposes the third dielectric layer;

[0015] Using the patterned photoresist layer as a mask, continue etching the third dielectric layer and the second etch stop layer to form a second opening, where the second opening is an extension of the first opening in the third dielectric layer and the second etch stop layer;

[0016] removing the patterned photoresist layer and the anti-reflective layer to expose a third opening in the patterned barrier layer;

[0017] Using the patterned barrier layer as a mask, the fourth dielectric layer and the third dielectric layer are etched to form a first trench, and the second dielectric layer is etched to form a first through hole.

[0018] Optionally, the first through hole is an extension of the second opening in the second dielectric layer.

[0019] Optionally, the patterned barrier layer is made of titanium nitride.

[0020] Optionally, a plasma etching process is used to form the first trench, the first through hole, the second trench and the second through hole.

[0021] Based on the same inventive concept, the present invention further provides a metal connection hole, which is made by using any of the above-mentioned methods for forming the metal connection hole.

[0022] In the metal connection hole and its formation method provided by the present invention, a second etch-stop layer, also known as a buffer layer, is added between the second and third dielectric layers. When etching the upper metal layer trench, the second etch-stop layer's barrier effect prevents plasma over-etching of the second dielectric layer at right angles to the upper metal layer trench, thereby preventing the formation of an inclined metal connection hole morphology. Furthermore, the second etch-stop layer can define the depth of the upper metal layer trench, and thus the depth of the upper metal layer. Similarly, the second etch-stop layer can also define the depth of the metal connection hole, avoiding the need to rely on two unstable parameters, etching time and etching rate, to control the depth of the upper metal layer trench and the depth of the metal connection hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Those skilled in the art will appreciate that the drawings are provided for a better understanding of the present invention, but do not constitute any limitation on the scope of the present invention.

[0024] Figure 1 It is an SEM image of a metal connection hole in the prior art.

[0025] Figure 2 It is a flow chart of a method for forming a metal connection hole according to an embodiment of the present invention.

[0026] Figures 3 to 8 It is a structural schematic diagram of corresponding steps of a method for forming a metal connection hole according to an embodiment of the present invention.

[0027] In the accompanying drawings: 100-metal contact hole; 10-substrate; 11-first dielectric layer; 12-lower metal layer; 13-first etch stop layer; 14-second dielectric layer; 15-second etch stop layer; 16-third dielectric layer; 17-fourth dielectric layer; 18-patterned barrier layer; 19-antireflective layer; 20-patterned photoresist layer; 21-first opening; 22-second opening; 23-third opening; 24-first trench; 24a-second trench; 25-first through hole; 25a-second through hole. DETAILED DESCRIPTION

[0028] To make the objects, advantages, and features of the present invention more clearly apparent, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale. They are only used to conveniently and clearly assist in illustrating the purposes of the embodiments of the present invention. In addition, the structures shown in the drawings are often part of the actual structure. In particular, different drawings may need to illustrate different focuses and sometimes use different scales.

[0029] As used in the present invention, the singular forms "a", "an", and "the" include plural objects, the term "or" is generally used to include the meaning of "and / or", the term "several" is generally used to include the meaning of "at least one", and the term "at least two" is generally used to include the meaning of "two or more". In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features specified as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features. In addition, as used in the present invention, an element is provided on another element, which generally only indicates that there is a connection, coupling, cooperation or transmission relationship between the two elements, and the connection, coupling, cooperation or transmission between the two elements can be direct or indirect through an intermediate element, and should not be understood to indicate or imply the spatial position relationship between the two elements, that is, one element can be in any orientation such as inside, outside, above, below, or to the side of another element, unless the content clearly indicates otherwise. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] Figure 2 FIG. 1 is a flow chart of a method for forming a metal connection hole according to an embodiment of the present invention. Figure 2 As shown, this embodiment provides a method for forming a metal connection hole, comprising:

[0031] Step S10, providing a substrate, on which a first dielectric layer and a lower metal layer located in the first dielectric layer are formed, and a first etch stop layer, a second dielectric layer, a third etch stop layer, and a third dielectric layer are sequentially formed on the lower metal layer and the first dielectric layer;

[0032] Step S20, forming a first trench and a first through-hole, wherein the first trench penetrates the third dielectric layer and stops on the second etch-stop layer, the first through-hole penetrates the second etch-stop layer and the second dielectric layer and stops on the first etch-stop layer, and the first trench and the first through-hole are connected;

[0033] Step S30, etching the first groove to form a second groove, and at the same time etching the first through hole to form a second through hole, the second groove penetrates the third dielectric layer and the second etch stop layer, the second through hole penetrates the second dielectric layer and the first etch stop layer and exposes the lower metal layer, the second groove constitutes an upper metal layer groove, and the second through hole constitutes a metal connection hole.

[0034] Figures 3 to 81 is a schematic diagram of the corresponding steps of the method for forming a metal connection hole according to an embodiment of the present invention. Figures 3 to 8 The specific embodiments of the present invention are described in detail.

[0035] like Figure 3 As shown, a substrate 10 is provided. In some embodiments, the substrate 10 can be a semiconductor substrate made of any semiconductor material suitable for semiconductor devices (such as Si, SiC, SiGe, etc.). In other embodiments, the substrate 10 can also be various composite substrates such as silicon on insulator (SOI) and silicon germanium on insulator. Those skilled in the art will understand that the substrate 10 is not subject to any restrictions and can be selected according to actual applications. Various device components (not limited to semiconductor devices) can be formed in the substrate 10. The substrate 10 may also have other layers or components formed thereon, such as: gate structures, contact holes, dielectric layers, metal connections and through holes, etc.

[0036] Please continue to refer to Figure 3 A first dielectric layer 11 and a lower metal layer 12 located within the first dielectric layer 11 are formed on the substrate 10. A first etch stop layer 13, a second dielectric layer 14, a second etch stop layer 15, and a third dielectric layer 16 are sequentially formed on the lower metal layer 12 and the first dielectric layer 11. The first dielectric layer 11, the second dielectric layer 14, and the third dielectric layer 16 are made of the same material: SiCOH, also known as black diamond (BD). Black diamond is a loose oxide-like substance containing silicon, oxygen, carbon, and hydrogen, and has a low dielectric constant. The first dielectric layer 11, the second dielectric layer 14, and the third dielectric layer are formed using a chemical vapor deposition process. The lower metal layer 12 is made of, for example, copper and is formed using a physical vapor deposition process. The first etch-stop layer 13 and the second etch-stop layer 15 are made of the same material, such as nitrogen-doped silicon carbide (NDC). Nitrogen-doped silicon carbide (SiCN) has a high hardness and is suitable as an etch-stop layer material. The first etch-stop layer 13 and the second etch-stop layer 15 are formed using a chemical vapor deposition process. The dielectric constant K value of the first etch-stop layer 13 and the second etch-stop layer 15 is very low, such as in the range of 2.8-3.3, resulting in a very small capacitance effect between the metal layers.

[0037] Please continue to refer to Figure 3A fourth dielectric layer 17, a patterned barrier layer 18, an anti-reflection layer 19, and a patterned photoresist layer 20 are sequentially formed on the third dielectric layer 16; the material of the fourth dielectric layer 17 is, for example, an oxide layer, and TEOS (tetraethoxysilane) is used as a silicon source, and the fourth dielectric layer 17 is formed by LPCVD or PECVD. The material of the patterned barrier layer 18 is, for example, titanium nitride (TIN), and is formed by a chemical vapor deposition process. The anti-reflection layer 19 is located at the bottom of the patterned photoresist layer 20 and is used to reduce the reflection of light in the photolithography process. The opening of the patterned photoresist layer 20 corresponds to the underlying metal layer 12, that is, the opening of the patterned photoresist layer 20 exposes the corresponding anti-reflection layer 19 on the underlying metal layer 12.

[0038] like Figure 4 As shown, using the patterned photoresist layer 20 as a mask, the anti-reflection layer 19 and the fourth dielectric layer 17 are etched to form a first opening 21. The first opening 21 penetrates the anti-reflection layer 19 and the fourth dielectric layer 17 and exposes the third dielectric layer 16, corresponding to the underlying metal layer 12. The etching process adopts a dry etching process. The process in this step is also called a BT (break through) process, and its main function is to remove the surface oxide layer. In the BT process, the etching gas is, for example, CF4.

[0039] like Figure 5 As shown, using the patterned photoresist layer 20 as a mask, the third dielectric layer 16 and the second etch-stop layer 15 are further etched to form a second opening 22. The second opening 22 is an extension of the first opening 21 in the third dielectric layer 16 and the second etch-stop layer 15. The etching process employs a dry etching process, such as a plasma etching process. The process in this step is also known as a PV (partial via) process.

[0040] like Figure 6 As shown, the patterned photoresist layer 20 and the anti-reflective layer 19 are removed, exposing a third opening 23 in the patterned barrier layer 18; the width of the third opening 23 is greater than the width of the second opening 22. In practice, after the BT and PV processes, the patterned photoresist layer 20 is almost completely consumed. If the patterned photoresist layer 20 is not completely consumed, a photoresist removal process is required, typically using an ashing process or stripping method to remove the remaining patterned photoresist.

[0041] like Figure 7As shown, using the patterned barrier layer 18 as a mask, the fourth dielectric layer 17 and the third dielectric layer 16 are etched to form a first trench 24, and the second dielectric layer is etched to form a first through hole 25. The first through hole 25 is an extension of the second opening 22 in the second dielectric layer 14. The first trench 24 stops on the second etch stop layer 15, and the first through hole 25 also stops on the first etch stop layer 13. The second etch stop layer 15 is also a buffer layer used to buffer the formation of the upper metal layer trench. The etching process is a dry etching process, such as a plasma etching process. The process of this step is also a trench (TR) formation process. Because the patterned photoresist layer 20 is too thin to serve as a mask for etching the fourth dielectric layer 17, a patterned barrier layer 18 is added to etch the barrier layer of the fourth dielectric layer 17.

[0042] like Figure 8 As shown, the second etch-stop layer 15 and the first etch-stop layer 13 are etched using the patterned barrier layer 18 as a mask. Specifically, the first trench 24 is etched to form a second trench 24a. Simultaneously, the first through-hole 25 is etched to form a second through-hole 25a. The second trench 24a penetrates the third dielectric layer 16 and the second etch-stop layer 15. The second through-hole 25a penetrates the second dielectric layer 14 and the first etch-stop layer 13 and exposes the underlying metal layer 12. The second trench 24a constitutes an upper metal layer trench, and the second through-hole 25a constitutes a metal connection hole. The thickness of the second etch-stop layer 15 is less than or equal to the thickness of the first etch-stop layer 13, so that the second etch-stop layer 15 is completely etched to avoid any residue of the second etch-stop layer 15 in the second trench 24a, which would reduce the yield of the semiconductor device. The second etch-stop layer 15 provides a barrier to prevent plasma over-etching of the second dielectric layer 14 at right angles to the second trench 24a during etching of the second trench 24a, thereby preventing the formation of an inclined metal connection hole. Furthermore, the second etch-stop layer 15 defines the depth of the second trench 24a, and thus the depth of the upper metal layer. Similarly, the second etch-stop layer also defines the depth of the metal connection hole, avoiding the need to rely on two unstable parameters, etching time and etching rate, to control the depth of the second trench and the depth of the metal connection hole.

[0043] Please continue to refer to Figure 8 This embodiment further provides a metal connection hole, which is manufactured using the above-mentioned method for forming the metal connection hole, comprising:

[0044] A substrate 10 is provided, on which a first dielectric layer 11 and a lower metal layer 12 located in the first dielectric layer 11 are formed, and on the lower metal layer 12 and the first dielectric layer 11, a first etch stop layer 13, a second dielectric layer 14, a second etch stop layer 15, a third dielectric layer 16, a fourth dielectric layer 17 and a patterned barrier layer 18 are sequentially formed.

[0045] The upper metal layer trench, namely the second trench 24a, sequentially penetrates the patterned barrier layer 18, the fourth dielectric layer 17, the third dielectric layer 16 and the second etch stop layer 15; the upper metal layer trench is used to fill the upper metal layer.

[0046] The metal connection hole, ie, the second through hole 25 a, passes through the second dielectric layer 14 and the first etch stop layer 13 . The metal connection hole is used to fill a metal plug, which is used to connect an upper metal layer and a lower metal layer.

[0047] In summary, in the metal connection hole and its formation method provided by the embodiment of the present invention, by adding a second etch stop layer, i.e., a buffer layer, between the second dielectric layer and the third dielectric layer, when etching the upper metal layer groove, the blocking effect of the second etch stop layer is utilized to prevent the second dielectric layer at the right angle of the upper metal layer groove from being over-etched by the plasma, thereby avoiding the formation of an inclined metal connection hole morphology. At the same time, the second etch stop layer can define the depth of the upper metal layer groove, i.e., the depth of the upper metal layer. Similarly, the second etch stop layer can also define the depth of the metal connection hole, avoiding the use of two unstable parameters, etching time and etching rate, to control the depth of the upper metal layer groove and the depth of the metal connection hole. The thickness of the second etch stop layer is less than or equal to the thickness of the first etch stop layer, so that the second etch stop layer is completely etched to avoid the second etch stop layer remaining in the upper metal layer groove and reducing the yield of the semiconductor device.

[0048] Furthermore, it should be recognized that although the present invention has been disclosed above with reference to preferred embodiments, the above embodiments are not intended to limit the present invention. Any person skilled in the art can utilize the above disclosed technical content to make many possible changes and modifications to the technical solution of the present invention, or modify it into equivalent embodiments with equivalent variations, without departing from the scope of the technical solution of the present invention. Therefore, any simple modifications, equivalent variations, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solution of the present invention, shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for forming a metal connection hole, characterized in that: include: Providing a substrate, on which a first dielectric layer and a lower metal layer located in the first dielectric layer are formed, and a first etch stop layer, a second dielectric layer, a second etch stop layer, and a third dielectric layer are sequentially formed on the lower metal layer and the first dielectric layer; forming a first trench and a first through-hole, wherein the first trench penetrates the third dielectric layer and stops on the second etch-stop layer, the first through-hole penetrates the second etch-stop layer and the second dielectric layer and stops on the first etch-stop layer, and the first trench and the first through-hole are in communication; Etching the first trench to form a second trench, and simultaneously etching the first through-hole to form a second through-hole, wherein the second trench penetrates the third dielectric layer and the second etch-stop layer, the second through-hole penetrates the second dielectric layer and the first etch-stop layer and exposes the underlying metal layer, the second trench constitutes an upper metal layer trench, and the second through-hole constitutes a metal connection hole; The step of forming the first trench and the first through hole includes: forming a fourth dielectric layer, a patterned barrier layer, an anti-reflection layer and a patterned photoresist layer in sequence on the third dielectric layer; Using the patterned photoresist layer as a mask, etching the anti-reflection layer and the fourth dielectric layer to form a first opening, wherein the first opening penetrates the anti-reflection layer and the fourth dielectric layer and exposes the third dielectric layer; Using the patterned photoresist layer as a mask, continue etching the third dielectric layer and the second etch stop layer to form a second opening, where the second opening is an extension of the first opening in the third dielectric layer and the second etch stop layer; removing the patterned photoresist layer and the anti-reflective layer to expose a third opening in the patterned barrier layer; Using the patterned barrier layer as a mask, the fourth dielectric layer and the third dielectric layer are etched to form a first trench, and the second dielectric layer is etched to form a first through hole.

2. The method for forming a metal connection hole according to claim 1, wherein: The thickness of the second etch stop layer is less than or equal to the thickness of the first etch stop layer.

3. The method for forming a metal connection hole according to claim 1, wherein: The first etch stop layer and the second etch stop layer are made of nitrogen-doped silicon carbide.

4. The method for forming a metal connection hole according to claim 1, wherein: The dielectric constants of the first etch stop layer and the second etch stop layer are 2.8 to 3.

3.

5. The method for forming a metal connection hole according to claim 1, wherein: The first dielectric layer, the second dielectric layer and the third dielectric layer are made of black diamond.

6. The method for forming a metal connection hole according to claim 1, wherein: The first through hole is an extension of the second opening in the second dielectric layer.

7. The method for forming a metal connection hole according to claim 1, wherein: The material of the patterned barrier layer is titanium nitride.

8. The method for forming a metal connection hole according to claim 1, wherein: The first trench, the first through hole, the second trench and the second through hole are formed by a plasma etching process.

9. A metal connection hole, characterized in that: The metal connection hole is manufactured by the method for forming the metal connection hole according to any one of claims 1 to 8.

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