Method for improving overlay precision offset process limitation and application
By adjusting the etching results and process parameters of the organic underlying structure layer, the damage to the titanium nitride layer and the nitrogen-free anti-reflective coating is reduced, and the problem of through-hole circuit breaking in semiconductor manufacturing is solved and the correctness of circuit connection is improved.
Patent Information
- Application Number
- CN202411575183.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-06
- Publication Date
- 2025-03-11
AI Technical Summary
During semiconductor manufacturing, the offset of the cross-cutting accuracy of multi-layer pattern alignment leads to the problem of through-hole circuit breaking during through-hole etching, affecting the accuracy of circuit connection.
By adjusting the etching results of the organic underlying structural layer, the etching process parameters are adjusted to reduce damage to the titanium nitride layer and the nitrogen-free anti-reflective coating by the etching gas, thereby reducing the generation of titanium fluorocarbon by-products.
It improves the problem of through-hole circuit breaking in the through-hole etching process, reduces the residue of by-products at the bottom of the through-hole, and ensures the correctness of circuit connections.
Smart Images
Figure CN119601466A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of semiconductor integrated circuits, and in particular relates to a method for improving overlay accuracy offset process limitations and an application thereof. Background Art
[0002] In the semiconductor manufacturing process, multi-layer patterns need to be precisely aligned. Overlay (OVL) refers to the position accuracy of one layer of pattern relative to another layer of pattern during the multi-layer lithography process. Higher OVL accuracy can ensure the correct connection between layers in the circuit, thereby ensuring the function and performance of the chip. In the more advanced 1x nm wire layer V0 through-hole etching process, it is easily affected by the OVL (M1 to V0) shift offset, causing V0 open circuit problems during the V0 etching process, such as Figure 1 As shown, V0 is normal in the 12nm process, but V0 is short-circuited in the 14nm and 16nm processes.
[0003] Affected by the OVL offset, the dry etching gas in the V0 etching process is likely to damage the TiN layer and the nitrogen-free anti-reflective coating (NFDARC), and generate titanium fluoride carbon (TiCF x ) byproduct. TiCF x Byproducts are very likely to remain and accumulate at the bottom of the V0 through-hole, causing the V0 through-hole etching to be hindered, resulting in insufficient V0 etching (under etching) and causing the circuit to be unable to connect correctly. Summary of the invention
[0004] In view of all or part of the deficiencies of the prior art described above, the object of the present invention is to provide a method and application for improving the overlay accuracy offset process limitation, by adjusting the etching result (ODL profile) of the organic dielectric layer (ODL) layer, reducing the damage to the NFDARC layer and the TiN layer, thereby improving the through-hole disconnection problem in the through-hole etching process and improving the overlay accuracy offset process limitation.
[0005] In order to achieve the above-mentioned invention object, the present invention provides the following technical solutions:
[0006] The present invention provides a method for improving the overlay accuracy offset process limitation, comprising the following steps:
[0007] Step 1: forming a titanium nitride layer, a first nitrogen-free anti-reflection coating and an organic underlying structure layer in sequence on the substrate structure, wherein the material of the organic underlying structure layer fills the grooves formed by the titanium nitride layer and the first nitrogen-free anti-reflection coating;
[0008] Step 2: performing a dry etching process on the organic bottom structure layer to the top of the first nitrogen-free anti-reflection coating;
[0009] Step three, performing a secondary dry etching on the organic bottom structure layer to the bottom of the groove; by adjusting the etching process parameters, the etching gas will not damage the titanium nitride layer and the first nitrogen-free anti-reflective coating on the side wall of the groove.
[0010] The present invention adjusts the etching result of the organic bottom structure layer, including the shape and geometric features after etching, by adjusting the etching process parameters of the organic bottom structure layer, so that the etching gas will not damage the titanium nitride layer and the nitrogen-free anti-reflection coating on the side wall of the groove, thereby reducing the titanium carbon fluoride (TiCF x ) byproducts, so as to prevent the byproducts from being deposited at the bottom of the through hole during subsequent etching of the through hole structure, thereby preventing the etching from being blocked, thereby improving the through hole disconnection problem in the through hole etching process. The titanium nitride layer is a metal hard mask layer.
[0011] In step two, the etching gas used for the primary dry etching is carbon dioxide and nitrogen with a flow ratio of 1-2:1; in step three, the etching gas used for the secondary dry etching is nitrogen and hydrogen with a flow ratio of 1-4:1. More preferably, the flow ratio of carbon dioxide and nitrogen in the primary dry etching is 1-1.8:1, and the flow ratio of nitrogen and hydrogen in the secondary dry etching is 1-2.5:1. By controlling the flow ratio of the etching gas, a suitable etching bow index can be provided to adjust the shape and geometry of the etching, thereby preventing the etching gas from damaging the titanium nitride layer and the nitrogen-free anti-reflective coating on the sidewalls of the groove when etching the organic underlying structure layer, thereby generating by-products and affecting subsequent etching.
[0012] In step 2, the etching gas used for the first dry etching is carbon dioxide and nitrogen in a flow ratio of 1:1; in step 3, the etching gas used for the second dry etching is nitrogen and hydrogen in a flow ratio of 1:1; the flow ratio of the etching gas used for the first dry etching to the etching gas used for the second dry etching is 2:1.
[0013] In step 2 and step 3, the conditions of the primary dry etching and the secondary dry etching are: high frequency RF power 700W, low frequency RF power 0W, and pressure 15mT.
[0014] A second nitrogen-free anti-reflection coating is formed between the substrate structure and the titanium nitride layer, and a low dielectric constant layer is formed between the second nitrogen-free anti-reflection coating and the substrate structure. The low dielectric constant layer is a SICOH film, and its material is a SICOH oxide dielectric with a high porosity.
[0015] The invention also includes a step 4 of continuing dry etching to form a hole structure in the second nitrogen-free anti-reflection coating and the low dielectric constant layer, including two steps of etching: the first step of etching is to use C x F y As the etching gas, CO or CO 2 As etching gas.
[0016] A silicon-based hard mask intermediate layer structure is also formed on the organic underlying structure layer; and the method further includes step five of performing an ashing process to remove the organic underlying structure layer and the silicon-based hard mask intermediate layer structure.
[0017] The method further comprises forming a photoresist layer on the silicon-based hard mask intermediate layer structure, transferring a pattern to the silicon-based hard mask intermediate layer structure through the photoresist layer, and etching the silicon-based hard mask intermediate layer structure using C x F y As etching gas.
[0018] The substrate structure comprises a TEOS layer, an NDC layer and a device layer which are sequentially located on a side of the low dielectric constant layer away from the second nitrogen-free anti-reflection coating, and the device layer is located below the trench.
[0019] The invention also provides a method for improving overlay accuracy offset process limitation and its application in a through hole etching process.
[0020] Compared with the prior art, the present invention has at least the following beneficial effects:
[0021] The present invention adjusts the etching result of the organic bottom structure layer, including the shape and geometric features after etching, by adjusting the etching process parameters of the organic bottom structure layer, so that the etching gas will not damage the titanium nitride layer and the nitrogen-free anti-reflection coating on the side wall of the groove, thereby reducing the titanium carbon fluoride (TiCF x ) by-products are prevented from being deposited at the bottom of the through-hole during subsequent etching, such as etching of the through-hole structure, thereby improving the through-hole disconnection problem in the through-hole etching process. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0023] Figure 1 It is the impact of OVL alignment offset on V0 through-holes in the V0 through-hole etching process of different-sized wire layers.
[0024] Figure 2 It is a flow chart of a method for improving overlay accuracy offset process limitation according to embodiment 1 of the present invention.
[0025] Figure 3 It is an etching structure used in the integrated circuit through-hole etching process adopted in the embodiment 1 of the present invention.
[0026] Figure 4 It is a schematic diagram of the etching process of steps S2-S5 of Example 1.
[0027] Figure 5 This is a schematic diagram of the etching process of steps S2-S5 of comparative example 1.
[0028] Figure 6 This is an EDS analysis diagram of the etching results of steps S3-S5 of Example 1, a corresponds to the result of step S3, b corresponds to the result of S4, c corresponds to the result of S5, and the circled part is a schematic diagram of the residual by-products.
[0029] Figure 7 This is a schematic diagram of the by-products remaining at the through-hole opening after the step S5 treatment in comparative example 1.
[0030] Figure 8 It is a schematic diagram of dry etching the organic bottom structure layer in steps S2 and S3 of the present invention.
[0031] Fig. 9 It is the influence of the flow ratio of the etching gas in steps S2 and S3 of the present invention on the bow index (a trend diagram obtained from an actual spilling experiment).
[0032] Figure numerals: 1-device layer; 2-NDC layer; 3-TEOS layer; 4-low dielectric constant layer; 5-second nitrogen-free anti-reflective coating; 6-titanium nitride layer; 7-first nitrogen-free anti-reflective coating; 8-organic underlying structure layer; 9-silicon-based hard mask intermediate layer structure; 10-photoresist layer; 11-groove; 12-through hole. DETAILED DESCRIPTION
[0033] The technical solutions in the specific embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0034] It should be noted that, in order to describe the technical solution more specifically, the steps described in the following embodiments do not strictly correspond to the steps described in the summary of the invention. The following embodiments take the V0 through hole etching process as an example, and the present invention is not limited thereto.
[0035] Example 1
[0036] This embodiment provides a method for improving the overlay accuracy offset process limitation. Figure 2 , including the following steps:
[0037] S1. Provide an etching structure for integrated circuit through-hole etching process (V0 through-hole has not yet been formed, the specific structure can be referred to Figure 3 ),include:
[0038] The substrate structure includes, from bottom to top, a substrate, a device layer 1 located in the substrate, an NDC layer 2 located on the device layer 1, and a TEOS layer 3 located on the NDC layer 2. The TEOS layer 3 includes, in sequence, a low dielectric constant layer 4, a patterned second nitrogen-free anti-reflection coating 5, a patterned titanium nitride layer 6, and a patterned first nitrogen-free anti-reflection coating 7. The low dielectric constant layer 4 is a SICOH film. The patterning refers to forming a groove 11 in the upper half of the second nitrogen-free anti-reflection coating 5, the titanium nitride layer 6, and the first nitrogen-free anti-reflection coating 7. The groove 11 is used for subsequent through-hole etching, and the device layer 1 is located below the groove 11.
[0039] The present invention also includes an organic underlying structure layer 8 formed on the first nitrogen-free anti-reflection coating 7, a silicon-based hard mask intermediate layer structure 9 formed on the organic underlying structure layer 8, and a photoresist layer 10 formed on the silicon-based hard mask intermediate layer structure 9. The material of the organic underlying structure layer 8 fills the groove 11 formed by the second nitrogen-free anti-reflection coating 5, the titanium nitride layer 6 and the first nitrogen-free anti-reflection coating 7. A photolithography pattern is formed on the photoresist layer 10, and the photoresist layer 10 transfers the pattern to the silicon-based hard mask intermediate layer structure 9. The etching of the silicon-based hard mask intermediate layer structure 9 adopts C x F y As etching gas.
[0040] S2, using the patterned silicon-based hard mask intermediate layer structure 9 as a mask, dry-etching the organic bottom structure layer 8 once, etching to the top of the first nitrogen-free anti-reflective coating 7; the etching gas used for the dry etching is carbon dioxide and nitrogen with a flow ratio of 1:1; the conditions of the dry etching are: high-frequency RF power 700W, low-frequency RF power 0W, pressure 15mT. Step S2 corresponds to ODL step 1, and its etching results can be referred to Figure 4 a in.
[0041] S3, perform secondary dry etching on the organic bottom structure layer 8, etching to the bottom of the groove 11; the etching gas used in the secondary dry etching is nitrogen and hydrogen with a flow ratio of 1:1, and the flow ratio of the etching gas used in the primary dry etching in step S2 to the etching gas used in the secondary dry etching in step S3 is 2:1; the conditions of the secondary dry etching are: high-frequency RF power 700W, low-frequency RF power 0W, pressure 15mT. Step S3 corresponds to ODL step2, and its etching results can be referred to Figure 4 b in the figure. By adjusting the etching process parameters, the etching gas will not damage the titanium nitride layer 6 and the first nitrogen-free anti-reflection coating 7 and the second nitrogen-free anti-reflection coating 5 on the sidewall of the groove 11 .
[0042] S4, continue to perform dry etching to form a hole structure in the second nitrogen-free anti-reflection coating 5 and the low dielectric constant layer 4, including two steps of etching: the first step of etching is to use C x F y As the etching gas, the trench 11 is dry-etched, and a small amount of by-products are produced. The etching results can be referred to Figure 4 c in the second step. The second step uses CO or CO 2 As the etching gas, the second nitrogen-free anti-reflective coating 5 and the low dielectric constant layer 4 are continuously dry-etched to form a hole structure, and a small amount of byproducts produced by the first step of etching fall to the bottom of the through hole 12, while no byproducts remain on the sidewalls of the through hole 12 and the groove 11. The etching results can be referred to Figure 4 In d.
[0043] S5, perform ashing treatment to remove the organic bottom structure layer 8 and the silicon-based hard mask intermediate layer structure 9. The bottom of the through hole 12 is not completely covered by the byproducts, and there are no residual byproducts on the sidewalls of the through hole 12 and the trench 11. The etching results can be referred to Figure 4 The e in.
[0044] Example 2
[0045] The difference from Example 1 is that in step S3, the etching gas used for the secondary dry etching is nitrogen and hydrogen with a flow ratio of 2:1. The bottom of the through hole 12 is not completely covered by the by-products (but compared with Example 1, the by-products may increase slightly), and there are no residual by-products on the sidewalls of the through hole 12 and the groove 11.
[0046] Comparative Example 1
[0047] The difference from Example 1 is that in step S3, the etching gas used for the secondary dry etching is nitrogen and hydrogen with a flow ratio of 6:1. Figure 5 , Figure 5In the figure, a indicates the etching result of step S2, b indicates the etching result of step S3, c indicates the etching result of the first etching in step S4, d indicates the etching result of the second etching in step S4, and e indicates the etching result of step S5.
[0048] Comparative Example 2
[0049] The difference from Example 1 is that in step S2, the etching gas used for the primary dry etching is carbon dioxide and nitrogen with a flow ratio of 3:1; in step S3, the etching gas used for the secondary dry etching is nitrogen and hydrogen with a flow ratio of 4:1.
[0050] Take Example 1 and Comparative Example 1 as examples, see Figure 4 and Figure 5 , we can know that:
[0051] After the step S3 of comparative example 1, the titanium nitride layer 6, the first nitrogen-free anti-reflection coating 7, and the second nitrogen-free anti-reflection coating 5 are damaged, and byproducts (combined with Figure 6 a), after the first etching step S4, more by-products are generated on the sidewall of the trench 11, and after the second etching step S4, a large amount of by-products fall into the bottom of the through hole 12, and a lot of by-products remain on the sidewall of the trench 11 (combined with Figure 6 b), after step S5, the byproducts obviously remain on the sidewalls of the through hole 12, resulting in a narrow opening window of the through hole 12 (combined with Figure 6 c and Figure 7 ), and a large amount of by-products remain at the bottom of the through hole 12, which makes it difficult to further etch the through hole 12. The etching is blocked, resulting in insufficient etching and a through hole break.
[0052] In Example 1, no by-products are generated in steps S2 and S3, i.e., the ODL etching stage, and only a small amount of by-products are generated after step S4. The small amount of by-products will not cause the opening of the through hole 12 to be narrowed, and will not significantly affect the subsequent further etching of the through hole, and can improve the through hole disconnection problem in the through hole etching process.
[0053] The present invention also screens and optimizes the etching process parameters in step S2 and step S3, especially the flow ratio of the etching gas. Figure 8 , Figure 8a represents a dry etching of the organic bottom structure layer 8, and b represents a second dry etching of the organic bottom structure layer 8, wherein the double-headed arrows A and B represent the etching range, wherein the ratio of B to A represents the Bowing index of the etched through hole. By adjusting the flow ratio of the etching gas and controlling the Bowing index within a suitable range, the etching range can be effectively controlled, thereby adjusting the ODL profile and reducing damage to the titanium nitride layer 6 and the first nitrogen-free anti-reflection coating 7 and the second nitrogen-free anti-reflection coating 5. Combined with Fig. 9 , Fig. 9 a in the figure is the relationship between the flow ratio of carbon dioxide and nitrogen and the bow index in step S2 (positive correlation), and b is the relationship between the flow ratio of nitrogen and hydrogen and the bow index in step S3 (positive correlation). It can be seen that increasing the flow ratio of nitrogen and hydrogen will lead to a larger bow index, making it easier for the secondary dry etching to damage the titanium nitride layer 6 and the first nitrogen-free anti-reflection coating 7 and the second nitrogen-free anti-reflection coating 5, thereby generating a large amount of by-products and causing through-hole disconnection. The present invention obtains the optimal parameter range under the maximum allowable sidewall tilt or bending by screening the flow ratio, that is, when the flow ratio of carbon dioxide and nitrogen is controlled at 1-2:1, and the flow ratio of nitrogen and hydrogen is controlled at 1-4:1. A further better effect is when the flow ratio of carbon dioxide and nitrogen is controlled at 1-1.8:1, and the flow ratio of nitrogen and hydrogen is controlled at 1-2.5:1. The best effect is when the flow ratio of the primary etching gas to the secondary etching gas is 2:1, the flow ratio of carbon dioxide to nitrogen is 1:1, and the flow ratio of nitrogen to hydrogen is 1:1. If the ratio of nitrogen to hydrogen is further reduced, the groove shape will be inconvenient for the subsequent formation of through holes. The main mechanism is that nitrogen and hydrogen react with carbon bonds in organic compounds (such as -COOH, -CaNb, or -CxHy groups) to form hydrocarbon polymers, thereby producing effective lateral protection capabilities. The more hydrocarbon polymers are generated, the more obvious the protection mechanism is.
[0054] The present invention provides a method for improving the process limitation of overlay accuracy offset and its application in a through-hole etching process. In the above embodiment, it is specifically applied to the V0 through-hole etching process, that is, the through-hole 12 in the embodiment is a V0 through-hole, and by adjusting the etching process parameters of the organic underlying structure layer 8, under the condition of selecting a suitable etching gas, the etching process and etching result of the organic underlying structure layer 8 are effectively controlled, and the damage to the NFDARC layer and the TiN layer is reduced to improve the V0 open problem. The present invention is mainly used in dry etching processes, and the etching gas optimization is used to improve the photolithography overlay process limitation, improve the process limitation problem of overlay offset, and reduce the risk of blind windows.
[0055] The above embodiments are only used to help understand the method and core idea of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.
Claims
1. A method for improving overlay accuracy offset process limitation, characterized in that: The following steps are involved: Step 1: forming a titanium nitride layer (6), a first nitrogen-free anti-reflection coating (7) and an organic underlying structure layer (8) in sequence on a substrate structure, wherein the material of the organic underlying structure layer (8) fills the groove (11) formed by the titanium nitride layer (6) and the first nitrogen-free anti-reflection coating (7); Step 2: performing a dry etching process on the organic bottom structure layer (8) to the top of the first nitrogen-free anti-reflection coating (7); Step three, performing a secondary dry etching on the organic bottom structure layer (8) to the bottom of the groove (11); by adjusting the etching process parameters, the etching gas will not cause damage to the titanium nitride layer (6) and the first nitrogen-free anti-reflective coating (7) on the side wall of the groove (11).
2. The method for improving overlay accuracy offset process limitation according to claim 1, characterized in that: In step 2, the etching gas used for the primary dry etching is carbon dioxide and nitrogen with a flow ratio of 1-2:1; in step 3, the etching gas used for the secondary dry etching is nitrogen and hydrogen with a flow ratio of 1-4:
1.
3. The method for improving overlay accuracy offset process limitation according to claim 2, characterized in that: In step 2, the etching gas used for the first dry etching is carbon dioxide and nitrogen in a flow ratio of 1:1; in step 3, the etching gas used for the second dry etching is nitrogen and hydrogen in a flow ratio of 1:1; the flow ratio of the etching gas used for the first dry etching to the etching gas used for the second dry etching is 2:
1.
4. The method for improving overlay accuracy offset process limitation according to claim 1, characterized in that: In step 2 and step 3, the conditions of the primary dry etching and the secondary dry etching are: high frequency RF power 700W, low frequency RF power 0W, and pressure 15mT.
5. The method for improving overlay accuracy offset process limitation according to claim 1, characterized in that: A second nitrogen-free anti-reflection coating (5) is also formed between the substrate structure and the titanium nitride layer (6), and a low dielectric constant layer (4) is also formed between the second nitrogen-free anti-reflection coating (5) and the substrate structure, wherein the low dielectric constant layer (4) is a SICOH film.
6. The method for improving overlay accuracy offset process limitation according to claim 5, characterized in that: The method further comprises step 4, wherein dry etching is continued to form a hole structure in the second nitrogen-free anti-reflection coating (5) and the low dielectric constant layer (4), comprising two steps of etching: the first step of etching is to use C x F y As the etching gas, the second step etching uses CO or CO2 as the etching gas.
7. The method for improving overlay accuracy offset process limitation according to claim 1, characterized in that: A silicon-based hard mask intermediate layer structure (9) is also formed on the organic underlying structure layer (8); and the method further includes a step five of performing an ashing process to remove the organic underlying structure layer (8) and the silicon-based hard mask intermediate layer structure (9).
8. The method for improving overlay accuracy offset process limitation according to claim 1, characterized in that: The method further comprises a photoresist layer (10) formed on the silicon-based hard mask intermediate layer structure (9), wherein a pattern is transferred to the silicon-based hard mask intermediate layer structure (9) through the photoresist layer (10), and the etching of the silicon-based hard mask intermediate layer structure (9) is performed by C x F y As etching gas.
9. The method for improving overlay accuracy offset process limitation according to claim 5, characterized in that: The substrate structure comprises a TEOS layer (3), an NDC layer (2) and a device layer (1) which are sequentially located on a side of the low dielectric constant layer (4) away from the second nitrogen-free anti-reflective coating (5), and the device layer (1) is located below the groove (11).
10. Application of the method for improving overlay accuracy offset process limitation as described in any one of claims 1 to 9 in a through-hole etching process.