Method for manufacturing through hole

Abstract

The present invention discloses a method for manufacturing a through hole, comprising: step 1, forming a current interlayer film on the surface of the bottom metal line and the bottom interlayer film of the semiconductor substrate. Step 2, defining the formation area of ​​the through hole. Step 3, using dry etching to perform main etching on the current interlayer film to form the opening of the through hole, and the setting of the selectivity ratio of the etching gas of the main etching will also cause difficult-to-remove by-products to be generated on the surface of the stop layer during the main etching process. Step 4, using dry etching to perform flattening etching to remove the by-products on the surface of the stop layer, and the process gas for the flattening etching uses oxygen plus argon, oxygen and by-products undergo a chemical reaction to decompose the by-products, and argon physically bombards the by-products to peel off the by-products. Step 5, filling the metal layer to form a through hole. The present invention can eliminate the gap between the filling metal of the through hole and the bottom metal line, thereby reducing the resistance of the through hole and improving the performance of the device.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a semiconductor integrated circuit, in particular to a method for manufacturing a through hole. Background Art

[0002] In the 8-inch wafer hole etching process, most of the filling materials are W; however, some special products require better conductivity, so the filling material will be changed from W to Al, which has better conductivity.

[0003] Although Al has better conductivity, it is found in actual applications that Al filling results in higher resistance.

[0004] Through failure mode analysis, it was found that after the hole etching was completed, stress would be generated between the stop layer composed of Ti layer and TiN layer ((Ti / TiN)) and Al, resulting in gaps between Al and titanium / titanium nitride during filling, poor contact in some areas, which in turn made the capacitance and resistance larger.

[0005] For hole etching, in order to ensure the selectivity of the stop layer and ensure sufficient over-etching window, a highly selective etching gas C is selected. 4 F 8 , in C 4 F 8 The etching process produces byproducts that are difficult to remove, and C 4 F 8 When etching TiN, charges are easily accumulated, and the charges will adsorb by-products produced during etching. If the by-products cannot be effectively removed, it is more likely to cause gaps between TiN and Al.

[0006] like Figure 1 , which is a SEM photo of a through hole formed by the existing through hole manufacturing method; a Ti layer and a TiN layer 102 are formed on the top surface of the bottom metal connection 101. It can be seen that the top surface of the TiN layer 102 is uneven, which will cause a gap between the through hole 103 formed by Al filling and the TiN layer 102, resulting in poor contact effect, and finally increasing the resistance of the device. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for manufacturing a through hole, which can eliminate the gap between the filling metal of the through hole and the underlying metal line, thereby reducing the resistance of the through hole and improving the performance of the device.

[0008] In order to solve the above technical problems, the present invention provides a method for manufacturing a through hole, comprising the following steps:

[0009] Step 1: providing a semiconductor substrate on which bottom metal lines formed by patterning a bottom metal layer are formed, and a bottom interlayer film is spaced between the bottom metal lines; forming a current interlayer film on the surface of the bottom metal lines and the bottom interlayer film.

[0010] Step 2: defining a through hole formation area, wherein the through hole formation area is located directly above the selected area of ​​the bottom metal line.

[0011] Step three, adopt dry etching to perform main etching on the current layer of interlayer film to form the opening of the through hole, the main etching uses the surface layer of the bottom metal wire as the stop layer, the selectivity ratio of the etching gas of the main etching is required to ensure the selection of the etching of the stop layer and to ensure the formation of an over-etching window that meets the requirements, so that after the opening of the through hole is formed, the current layer of interlayer film on the surface of the stop layer in the opening of the through hole is completely removed; the setting of the selectivity ratio of the etching gas of the main etching will also cause difficult-to-remove by-products to be produced on the surface of the stop layer during the main etching process.

[0012] Step 4: Use dry etching to perform planarization etching to remove the by-products on the surface of the stop layer and thereby make the bottom surface of the opening of the through hole flat. The process gas for the planarization etching uses oxygen and argon. The oxygen and the by-products chemically react to decompose the by-products, and the argon physically bombards the by-products to peel off the by-products.

[0013] Step five: filling a metal layer in the opening of the through hole to form the through hole.

[0014] A further improvement is that a Ti layer and a TiN layer are formed on the surface of the bottom metal layer, and the stop layer is the TiN layer.

[0015] A further improvement is that the current interlayer film is an oxide layer.

[0016] A further improvement is that the current interlayer film is a BPSG oxide layer.

[0017] A further improvement is that in step 3, the etching gas for the main etching is C 4 F 8 , so that the selection ratio of the etching gas for the main etching meets the requirements.

[0018] A further improvement is that in step 3, the by-product includes C 2 F 5 + .

[0019] A further improvement is that in step 4, the chemical reaction equation of the oxygen and the by-product is:

[0020] C 2 F 5 + +O 2 -->CF 2 + +COF 3 + ;

[0021] CF 2 + and COF 3 + They are all easily removable substances.

[0022] A further improvement is that in step five, the metal layer filled in the opening of the through hole is an Al layer, and after the bottom surface of the opening of the through hole is flattened, the Al layer and the TiN layer at the bottom form a seamless contact to reduce the contact resistance of the through hole.

[0023] A further improvement is that the semiconductor substrate comprises a silicon substrate.

[0024] A further improvement is that the bottom metal layer is an Al layer and the bottom interlayer film is an oxide layer.

[0025] A further improvement is that the wafer of the semiconductor substrate is larger than 8 inches.

[0026] A further improvement is that in step 4, the process conditions of the planarization etching include:

[0027] RF is 200W~1600W;

[0028] The oxygen flow rate is 5 sccm to 30 sccm;

[0029] The argon gas flow rate is 100 sccm to 900 sccm.

[0030] A further improvement is that the photoresist pattern formed by the photolithography process in step 2 defines the formation area of ​​the through hole.

[0031] A further improvement is that after step 4 is completed and before step 5 is performed, a step of removing the photoresist pattern is also included.

[0032] A further improvement is that in step three, the by-product also includes a polymer, and in step four, the polymer is removed by physical bombardment of the argon gas.

[0033] The present invention adds a planarization etch in a targeted manner after the main etching of the through hole opening, and utilizes the chemical reaction of oxygen and the physical bombardment of argon in the planarization etching to planarize the bottom surface of the through hole opening, so that after the metal layer is filled in the through hole opening, a good contact without gaps can be formed between the bottom surface of the through hole and the underlying metal line, thereby reducing the resistance of the through hole and improving the performance of the device.

[0034] The present invention is particularly suitable for the process of switching the filling metal layer of the through hole from tungsten to aluminum. Although the filling ability of aluminum is not as strong as that of tungsten, after planarization etching, it can still maintain good filling of Al, and combined with the better conductivity of Al, it can finally reduce the overall resistance of the through hole and improve the performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0036] Figure 1 is a SEM photograph of a through hole formed by an existing through hole manufacturing method;

[0037] Figure 2 is a flow chart of a method for manufacturing a through hole according to an embodiment of the present invention;

[0038] Figure 3A-Figure 3F Schematic diagram of the device structure in each step of the method for manufacturing a through hole according to an embodiment of the present invention;

[0039] Figure 4 is a SEM photograph of a through hole formed by the method for manufacturing a through hole according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] like Figure 2 As shown, it is a flow chart of a method for manufacturing a through hole 207 according to an embodiment of the present invention; FIG. 3A to FIG. 3F , which is a schematic diagram of the device structure in each step of the method for manufacturing the through hole 207 according to an embodiment of the present invention; the method for manufacturing the through hole 207 according to an embodiment of the present invention comprises the following steps:

[0041] Step 1: Figure 3A As shown, a semiconductor substrate 201 is provided, on which a bottom metal line 203 formed by patterning a bottom metal layer is formed, and a bottom interlayer film 202 is spaced between the bottom metal lines 203; a current interlayer film 204 is formed on the surface of the bottom metal line 203 and the bottom interlayer film 202.

[0042] In the embodiment of the present invention, the semiconductor substrate 201 includes a silicon substrate.

[0043] The bottom metal layer 103 is an Al layer, and the bottom interlayer film 202 is an oxide layer.

[0044] The semiconductor substrate 201 has a wafer size of more than 8 inches.

[0045] The current interlayer film 204 is an oxide layer. Preferably, the current interlayer film 204 is a BPSG oxide layer.

[0046] A Ti layer and a TiN layer are formed on the surface of the underlying metal layer.

[0047] Step 2: Figure 3B As shown, a formation region of a through hole 207 is defined, and the formation region of the through hole 207 is located directly above a selected region of the underlying metal line 203 .

[0048] In the embodiment of the present invention, the photoresist 205 pattern formed by the photolithography process defines the formation area of ​​the through hole 207.

[0049] Step 3: Figure 3C As shown, dry etching is used to perform main etching on the current layer of interlayer film 204 to form the opening of the through hole 207. The main etching uses the surface layer of the underlying metal line 203 as a stop layer. The selectivity ratio of the etching gas of the main etching is required to ensure the selection of the etching of the stop layer and to ensure the formation of an over-etching window that meets the requirements, so that after the opening of the through hole 207 is formed, the current layer of interlayer film 204 on the surface of the stop layer in the opening of the through hole 207 is completely removed; the setting of the selectivity ratio of the etching gas of the main etching will also cause difficult-to-remove by-products 206 to be produced on the surface of the stop layer during the main etching process.

[0050] In the embodiment of the present invention, the etching gas used in the main etching is C 4 F 8 , so that the selection ratio of the etching gas for the main etching meets the requirements.

[0051] The byproduct 206 includes C 2 F 5 + .

[0052] The by-product 206 also includes polymers.

[0053] The stop layer is the TiN layer.

[0054] Step 4: Figure 3DAs shown, dry etching is used for planarization etching to remove the byproduct 206 on the surface of the stop layer and thereby make the bottom surface of the opening of the through hole 207 flat. The process gas for the planarization etching uses oxygen and argon. The oxygen and the byproduct 206 chemically react to decompose the byproduct 206, and the argon physically bombards the byproduct 206 to peel off the byproduct 206.

[0055] In the embodiment of the present invention, the chemical reaction equation of the oxygen and the byproduct 206 is:

[0056] C 2 F 5 + +O 2 -->CF 2 + +COF 3 + ;

[0057] CF 2 + and COF 3 + They are all easily removable substances.

[0058] The process conditions of the planarization etching include:

[0059] RF is 200W~1600W;

[0060] The oxygen flow rate is 5 sccm to 30 sccm;

[0061] The argon gas flow rate is 100 sccm to 900 sccm.

[0062] The polymer is removed by physical bombardment of the argon gas.

[0063] like Figure 3E As shown, the photoresist 205 pattern is removed.

[0064] Step 5: Figure 3F As shown, a metal layer is filled in the opening of the through hole 207 to form the through hole 207 .

[0065] In the embodiment of the present invention, the metal layer filled in the opening of the through hole 207 is an Al layer. After the bottom surface of the opening of the through hole 207 is flattened, the Al layer and the TiN layer at the bottom form a seamless contact to reduce the contact resistance of the through hole 207.

[0066] The embodiment of the present invention adds a planarization etch in a targeted manner after the main etch of the opening of the through hole 207, and utilizes the chemical reaction of oxygen and the physical bombardment of argon in the planarization etch to planarize the bottom surface of the opening of the through hole 207, so that after the metal layer is filled in the opening of the through hole 207, a good contact without gaps can be formed between the bottom surface of the through hole 207 and the underlying metal line 203, thereby reducing the resistance of the through hole 207 and improving the performance of the device.

[0067] The embodiment of the present invention is particularly suitable for the process of switching the filling metal layer of the through hole 207 from tungsten to aluminum. Although the filling ability of aluminum is not as strong as that of tungsten, after planarization etching, it can still maintain good filling of Al, and combined with the better conductive performance of Al, it can finally reduce the overall resistance of the through hole 207 and improve the performance of the device.

[0068] like Figure 4 , which is a SEM photograph of a through hole formed by the through hole manufacturing method of an embodiment of the present invention; a Ti layer and a TiN layer 203a are formed on the top surface of the bottom metal connection 203. It can be seen that the top surface of the TiN layer 203a is flat, which will prevent a gap from being generated between the through hole 207 formed by Al filling and the TiN layer 203a, thereby forming a good contact, and finally reducing the resistance of the device.

[0069] The present invention has been described in detail above through specific embodiments, but these do not constitute limitations of the present invention. Without departing from the principle of the present invention, those skilled in the art may also make many variations and improvements, which should also be considered as the protection scope of the present invention.

Claims

1. A method for manufacturing a through hole, It is characterized in that The steps include: Step 1, providing a semiconductor substrate, on which a bottom metal line formed by patterning a bottom metal layer is formed, and a bottom interlayer film is spaced between the bottom metal lines; forming a current interlayer film on the surface of the bottom metal line and the bottom interlayer film; A Ti layer and a TiN layer are formed on the surface of the bottom metal layer; Step 2, defining a formation area of ​​a through hole, wherein the formation area of ​​the through hole is located directly above the selected area of ​​the bottom metal line; Step 3: dry etching is used to perform main etching on the current interlayer film to form the opening of the through hole, the main etching uses the surface layer of the bottom metal line as a stop layer, and the stop layer is the TiN layer; the selectivity of the etching gas of the main etching is required to ensure the selection of the etching of the stop layer and to ensure the formation of an over-etching window that meets the requirements, so that after the opening of the through hole is formed, the current interlayer film on the surface of the stop layer in the opening of the through hole is completely removed; the setting of the selectivity of the etching gas of the main etching will also cause by-products that are difficult to remove to be generated on the surface of the stop layer during the main etching process; The etching gas for the main etching is C 4 F 8 , so that the selection ratio of the etching gas of the main etching meets the requirements; The by-products include C 2 F 5 + Step 4: performing planarization etching by dry etching to remove the byproducts on the surface of the stop layer and thereby make the bottom surface of the opening of the through hole flat, wherein the process gas for the planarization etching is oxygen plus argon, wherein the oxygen and the byproducts chemically react to decompose the byproducts, and the argon physically bombards the byproducts to peel off the byproducts; The chemical reaction equation of the oxygen and the by-product is: C 2 F 5 + +O 2 -->CF 2 + +COF 3 + ; CF 2 + and COF 3 + All are easily removable substances; Step 5: Filling a metal layer in the opening of the through hole to form the through hole; The metal layer filled in the opening of the through hole is an Al layer. After the bottom surface of the opening of the through hole is flattened, the Al layer and the TiN layer at the bottom form a seamless contact to reduce the contact resistance of the through hole.

2. The method for manufacturing a through hole according to claim 1, Features: The current interlayer film is an oxide layer.

3. The method for manufacturing a through hole according to claim 2, Features: The current interlayer film is a BPSG oxide layer.

4. The method for manufacturing a through hole according to claim 1, Features: The semiconductor substrate includes a silicon substrate.

5. The method for manufacturing a through hole according to claim 1, Features: The bottom metal layer is an Al layer, and the bottom interlayer film is an oxide layer.

6. The method for manufacturing a through hole according to claim 1, Features: The semiconductor substrate wafer is larger than 8 inches.

7. The method for manufacturing a through hole according to claim 1 or 1, Features: In step 4, the process conditions of the planarization etching include: RF is 200W~1600W; The oxygen flow rate is 5 sccm to 30 sccm; The argon gas flow rate is 100 sccm to 900 sccm.

8. The method for manufacturing a through hole according to claim 1, Features: In step 2, the photoresist pattern formed by the photolithography process defines the formation area of ​​the through hole.

9. The method for manufacturing a through hole according to claim 8, Features: After step 4 is completed and before step 5 is performed, the step of removing the photoresist pattern is also included.

10. The method for manufacturing a through hole according to claim 8, Features: In step three, the by-products also include polymers, and in step four, the polymers are removed by physical bombardment of the argon gas.

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