Method for removing metal polymer formed in metal interconnection process

Abstract

The invention provides a method for removing a metal polymer formed in a metal interconnection process, and the method comprises the steps: providing a semiconductor structure which comprises a first metal layer, an NDC layer, a USG layer, a DARC layer and a photoresist layer; etching the DARC layer, the USG layer and a part of thickness of the NDC layer along the opening of the photoresist layer to form a filling groove; etching the residual thickness of the NDC layer at the bottom of the filling groove until the first metal layer is exposed, and etching the photoresist layer, the DARC layer and the USG layer at the same time to enlarge the width of the filling groove, at the moment, forming a metal polymer on the side wall of the photoresist layer; removing the photoresist layer by adopting high-frequency source power of 500W-1500W, F-containing strong oxidizing gas and high-flow CO2 gas, and at the moment, scattering the metal polymer; the scattered metal polymer is rapidly extracted and removed; and washing the semiconductor structure after the photoresist layer is removed. According to the invention, the problem of high product defects caused by metal polymers formed in the existing metal interconnection process is solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and particularly to a method for removing metal polymers formed in a metal interconnect process. Background Art

[0002] The traditional copper (Cu) interconnect process solution is as follows: Via-metal is used for connection (metal1-via1-metal2), and the interconnection of copper in the back-end process is achieved through vias between metals (metal) (as Figure 1 shown); while the improved copper interconnect process solution is: cancel the via between metal and metal, and directly connect metal-metal to achieve the interconnection of copper in the back-end process (as Figure 2 shown).

[0003] In the traditional via-metal interconnect process, due to the small light transmittance of the via (<10%), during the etching process, the exposed copper area of metal1 is relatively small, and the diffusion of copper in the chamber is less. In the improved metal-metal interconnect process, the light transmittance of the metal is larger (>30%). During the etching process, the exposed copper area of metal1 is larger, and along with the physical bombardment during the etching process, the diffusion of copper in the chamber increases significantly, and it combines with the polymers generated during the etching process to form metal polymers, and the generated metal polymers will accumulate on the sidewalls (as Figure 3 shown). And the metal polymers are difficult to remove, resulting in high product defects and poor etching stability. Summary of the Invention

[0004] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for removing metal polymers formed in a metal interconnect process, which is used to solve the problem of high product defects caused by the formation of metal polymers in the existing metal interconnect process.

[0005] To achieve the above purpose and other related purposes, the present invention provides a method for removing metal polymers formed in a metal interconnect process, the method comprising:

[0006] Providing a semiconductor structure, which includes a first metal layer, an NDC layer formed on the surface of the first metal layer, a USG layer formed on the surface of the NDC layer, a DARC layer formed on the surface of the USG layer, and a photoresist layer formed on the surface of the DARC layer and patterned to form an opening;

[0007] Etching the DARC layer, the USG layer, and a part of the thickness of the NDC layer along the opening of the photoresist layer to form a filling trench;

[0008] Etch the remaining thickness of the NDC layer at the bottom of the filled trench until the first metal layer is exposed, and at the same time etch the photoresist layer, the DARC layer, and the USG layer on both sides of it to widen the width of the filled trench. At this time, there is a metal polymer formed by bombarding the first metal layer at the sidewall of the photoresist layer;

[0009] Use a high-frequency source power of 500W to 1500W, a strong oxidizing gas containing F, and a large flow rate of CO 2 gas to remove the photoresist layer. At this time, the metal polymer is broken up;

[0010] Quickly evacuate the broken-up metal polymer;

[0011] Rinse the semiconductor structure after removing the photoresist layer.

[0012] Optionally, the strong oxidizing gas containing F includes CF4.

[0013] Optionally, the flow rate of the strong oxidizing gas containing F is less than 200 sccm.

[0014] Optionally, when removing the photoresist, the flow rate of CO 2 used is 1000 sccm to 2000 sccm.

[0015] Optionally, when evacuating the broken-up metal polymer, the chamber pressure is 0 mT to 50 mT.

[0016] Optionally, use CO 2 gas to rinse the semiconductor structure.

[0017] Optionally, the method further includes a step of filling a second metal layer in the filled trench.

[0018] Optionally, the material of the second metal layer is the same as that of the first metal layer.

[0019] Optionally, the materials of both the first metal layer and the second metal layer are copper.

[0020] As described above, the method for removing the metal polymer formed in the metal interconnect process of the present invention first widens the width of the filled trench, then removes the photoresist, and uses a pure source power of 500W to 1500W, CF4, and CO 2 to remove the photoresist, and uses CO 2 to rinse after removal. Through the above method, the metal polymer formed by the combination of copper and the polymer generated during the etching process can be effectively removed. Description of the Drawings

[0021] Figure 1 Shown is a schematic cross-sectional structure diagram of an existing metal-via-metal interconnect structure.

[0022] Figure 2 Shown is a schematic cross-sectional structure diagram of an existing metal-metal interconnect structure.

[0023] Figure 3 Shown as forming Figure 2 A schematic cross-sectional structure diagram of an interconnect structure with a metal polymer formed during the process of forming the structure shown.

[0024] Figures 4 to 8 Shown is a schematic cross-sectional structure diagram of the process of removing the metal polymer formed in the metal interconnect process of the present invention.

[0025] Figure 9 Shown is a flowchart of the method for removing the metal polymer formed in the metal interconnect process of the present invention. Detailed implementation manners

[0026] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0027] Please refer to Figures 1 to 9 . It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Although only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components during actual implementation, the actual morphology, quantity, and ratio of each component during implementation can be arbitrarily changed, and the component layout morphology may also be more complex.

[0028] As Figure 9 shown, this embodiment provides a method for removing the metal polymer formed in the metal interconnect process. The method includes:

[0029] Providing a semiconductor structure, which includes a first metal layer, an NDC layer formed on the surface of the first metal layer, a USG layer formed on the surface of the NDC layer, a DARC layer formed on the surface of the USG layer, and a photoresist layer PR formed on the surface of the DARC layer and patterned to form an opening;

[0030] Etching the DARC layer, the USG layer, and a part of the thickness of the NDC layer along the opening of the photoresist layer PR to form a filling trench;

[0031] Etch the remaining thickness of the NDC layer at the bottom of the filled trench until the first metal layer is exposed, and at the same time, etch the photoresist layer PR, the DARC layer, and the USG layer on both sides thereof to widen the width of the filled trench. At this time, there is a metal polymer formed by bombarding the first metal layer at the sidewall of the photoresist layer PR;

[0032] Use a pure source power of 500W - 1500W, a fluorine-containing strongly oxidizing gas, and a large flow rate of CO 2 gas to remove the photoresist layer PR. At this time, the metal polymer is broken up;

[0033] Quickly evacuate the broken-up metal polymer;

[0034] Rinse the semiconductor structure after removing the photoresist layer PR.

[0035] In this embodiment, the width of the filled trench is first widened and then the photoresist layer PR is removed. Moreover, when removing the photoresist layer PR, a pure source power of 500W - 1500W is used, which can ensure the lateral etching of the photoresist layer PR, accelerate the removal of the photoresist layer PR, and at the same time ensure that the damage to the first metal layer caused by plasma is weakened.

[0036] Specifically, the material of the first metal layer is copper.

[0037] Specifically, the fluorine-containing strongly oxidizing gas includes CF4.

[0038] In this embodiment, CF4 gas is used in combination with a large flow rate of CO 2 . On the one hand, the dissociated F ions and O ions combine to form a stronger oxidant, which can quickly attack the carbon chains in the photoresist and form volatile fluorocarbons (such as C2F6) with carbon atoms, accelerating the complete removal of the photoresist layer PR; on the other hand, CF4 gas can also enhance the physical bombardment effect and break up the polymers containing C / metal polymers.

[0039] More specifically, the flow rate of the fluorine-containing strongly oxidizing gas is less than 200 sccm.

[0040] Specifically, when removing the photoresist, the flow rate of CO 2 used is 1000 sccm - 2000 sccm.

[0041] Specifically, when evacuating the broken-up metal polymer, the chamber pressure is 0 mT - 50 mT.

[0042] Specifically, CO 2 gas is used to rinse the semiconductor structure.

[0043] In this embodiment, CO 2 is used for rinsing. On the one hand, the dissociated O ions can remove the residual polymers. On the other hand, the dissociated CO ions achieve surface treatment of the first metal layer located at the bottom of the filled trench after etching.

[0044] Specifically, the method further includes the step of filling a second metal layer in the filled trench.

[0045] More specifically, the material of the second metal layer is the same as that of the first metal layer.

[0046] As an example, the material of the second metal layer is copper.

[0047] In summary, the method for removing metal polymers formed in the metal interconnect process of the present invention first expands the width of the filled trench, then removes the photoresist, and uses a pure source power of 500W to 1500W, CF4 and CO 2 to remove the photoresist, and uses CO 2 for rinsing after removal. Through the above method, the metal polymers formed by the combination of copper and the polymers generated during the etching process can be effectively removed. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0048] The above embodiments merely illustrate the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for removing metal polymers formed in a metal interconnection process, characterized in that: The method comprises: A semiconductor structure is provided, comprising a first metal layer, an NDC layer formed on a surface of the first metal layer, a USG layer formed on a surface of the NDC layer, a DARC layer formed on a surface of the USG layer, and a photoresist layer formed on a surface of the DARC layer and patterned to form an opening; Etching the DARC layer, the USG layer and a partial thickness of the NDC layer along the opening of the photoresist layer to form a filled trench; Etching the remaining thickness of the NDC layer at the bottom of the filled trench until the first metal layer is exposed, and simultaneously etching the photoresist layer, the DARC layer, and the USG layer on both sides thereof to expand the width of the filled trench, at which point metal polymers are formed at the sidewalls of the photoresist layer due to bombardment of the first metal layer; The photoresist layer is removed by using a high-frequency source power of 500W to 1500W, a strong oxidizing gas containing F and a large flow of CO2 gas, at which time the metal polymer is broken up; Rapidly extracting the dispersed metal polymer; The semiconductor structure is rinsed after the photoresist layer is removed.

2. The method for removing metal polymers formed in a metal interconnection process according to claim 1, characterized in that: The F-containing strong oxidizing gas includes CF4.

3. The method for removing metal polymers formed in a metal interconnection process according to claim 2, characterized in that: The flow rate of the F-containing strong oxidizing gas is less than 200 sccm.

4. The method for removing metal polymers formed in a metal interconnection process according to claim 1, characterized in that: When removing the photoresist, the flow rate of CO2 used includes 1000 sccm to 2000 sccm.

5. The method for removing metal polymers formed in a metal interconnection process according to claim 1, characterized in that: When the dispersed metal polymer is extracted, the air pressure in the chamber is 0 mT to 50 mT.

6. The method for removing metal polymers formed in a metal interconnection process according to claim 1, characterized in that: The semiconductor structure is flushed with CO2 gas.

7. The method for removing metal polymers formed in a metal interconnection process according to claim 1, characterized in that: The method further comprises the step of filling a second metal layer in the filling trench.

8. The method for removing metal polymers formed in a metal interconnection process according to claim 1, characterized in that: The material of the second metal layer is the same as that of the first metal layer. 9 . The method for removing metal polymers formed in a metal interconnection process according to claim 8 , wherein the first metal layer and the second metal layer are both made of copper.

Images