A process method for achieving high selectivity etching of titanium to silicon nitride

Abstract

The application provides a process method for realizing high-selectivity etching of titanium and silicon nitride, and belongs to the technical field of semiconductor manufacturing. The method comprises the following steps: providing a substrate with a silicon nitride layer and a titanium layer formed on the surface in sequence and having been patterned; and performing plasma dry etching on the substrate, wherein the process gas for dry etching comprises chlorine, boron trichloride and argon, and the flow ratio of chlorine, boron trichloride and argon is (2-4):(1-2):(5-8). The process realizes high etching selectivity between titanium and silicon nitride under single-step etching conditions, the etching morphology has a straight sidewall, and the loss of the underlying silicon nitride is small. Compared with the multi-step complex process of alternating passivation and etching in the prior art, the application can realize high selectivity only by single-step etching, significantly simplifies the process flow, improves the production efficiency, ensures high anisotropy of etching, and can be widely applied to the manufacturing process of semiconductor devices.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, and specifically relates to a process method for achieving high selectivity etching of titanium and silicon nitride. Background Technology

[0002] In semiconductor device manufacturing, etching is a crucial step in pattern transfer, requiring precise etching of the target material while maximizing the protection of the mask layer and underlying materials. Titanium (Ti), due to its excellent conductivity, adhesion, and corrosion resistance, is frequently used as a key structural material in semiconductor devices, such as metal interconnect layers and barrier layers. Silicon nitride (SiN), on the other hand, is widely used as an insulating layer, passivation layer, or etch stop layer. In etching scenarios involving both Ti and SiN, improving the etch selectivity of Ti relative to SiN—that is, achieving a Ti etching rate significantly higher than the SiN etching rate—is a critical technical challenge. Currently, commonly used Ti etching gases are mostly chlorine-containing gases (such as Cl2 and BCl3). However, single or conventionally proportioned chlorine-containing gas compositions often exhibit significant etching effects on SiN when etching Ti, leading to excessive wear of the SiN protective layer and consequently affecting the device's dimensional accuracy, electrical performance, and reliability.

[0003] Argon (Ar) is often introduced into etching gases to enhance plasma density and improve etching uniformity. However, the existing technology has not optimized the ratio of Ar to Cl2 and BCl3, and has failed to achieve an ideal balance between high Ti etching rate and low SiN etching rate.

[0004] Therefore, developing an etching gas composition and supporting process that can significantly improve the etching selectivity ratio of Ti to SiN is of great significance for improving the manufacturing quality and yield of semiconductor devices. Summary of the Invention

[0005] The present invention aims to solve the technical problems existing in the prior art and provide a process method for achieving high selectivity etching of titanium and silicon nitride.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A process method for achieving high selectivity etching of titanium and silicon nitride is provided, comprising the following steps: A substrate with a silicon nitride layer and a titanium layer sequentially formed on its surface and patterned is provided; The substrate is subjected to plasma dry etching, and the process gases for the dry etching include chlorine, boron trichloride and argon; and the flow rate ratio of chlorine, boron trichloride and argon is (2~4):(1~2):(5~8).

[0007] Furthermore, the bias power of the dry etching is 30~70W.

[0008] Furthermore, the source power of the dry etching is 600~1000W, preferably 700~900W.

[0009] Furthermore, the flow rate of chlorine is 20-40 sccm, the flow rate of boron trichloride is 10-20 sccm, and the flow rate of argon is 50-80 sccm.

[0010] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: The etching method of the present invention achieves a high etching selectivity between titanium and silicon nitride by optimizing the gas ratio and process parameters, thus solving the problem in the prior art that it is difficult to take into account the difference in etching rate between the two materials in the same etching step.

[0011] Compared to the complex multi-step process of existing technologies that requires alternating passivation and etching, this invention achieves high selectivity with only a single etching step, significantly simplifying the process and improving production efficiency. The provided etching method ensures high anisotropy of the etching, resulting in an etch profile with good perpendicularity.

[0012] The provided etching method has advantages such as simplified process, excellent etching morphology, and strong compatibility, and can be widely used in the manufacturing process of semiconductor devices. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the process flow for etching the Ti / SiN stacked structure according to the present invention.

[0015] Figure 2 This is a SEM cross-sectional view of the etched Ti / SiN stacked structure in Example 1.

[0016] Figure 3 This is a SEM cross-sectional view of the etched Ti / SiN stacked structure in Comparative Example 3. Detailed Implementation

[0017] A typical embodiment of the present invention provides a process method for achieving high selectivity etching of titanium and silicon nitride, comprising the following steps: A substrate with a silicon nitride layer and a titanium layer sequentially formed on its surface and patterned is provided; The substrate is subjected to plasma dry etching, and the process gases for the dry etching include chlorine, boron trichloride and argon; and the flow rate ratio of chlorine, boron trichloride and argon is (2~4):(1~2):(5~8).

[0018] The flow rate ratio of chlorine, boron trichloride and argon is (2~4):(1~2):(5~8), for example 2:1:4, 2:1:5, 3:1.5:6.5, 3:2:6, 4:2:5, etc.

[0019] In some preferred embodiments, the bias power of the dry etching is 30~70W.

[0020] In some preferred embodiments, the source power of the dry etching is 600~1000W, preferably 700~900W.

[0021] In some preferred embodiments, the flow rate of chlorine is 20-40 sccm, the flow rate of boron trichloride is 10-20 sccm, and the flow rate of argon is 50-80 sccm.

[0022] In some preferred embodiments, the pressure inside the reaction chamber during the dry etching process is 3~8mT; In some preferred embodiments, the temperature inside the reaction chamber during the dry etching process is 40~50℃.

[0023] In some preferred embodiments, the thickness of the silicon nitride layer is 200~400nm; the thickness of the titanium layer is 10~30nm.

[0024] In some preferred embodiments, the substrate of the substrate is silicon.

[0025] In some preferred embodiments, after the plasma dry etching, the substrate after dry etching is further subjected to wet resist removal.

[0026] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0027] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0028] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0029] Example 1 Etching process for Ti / SiN stacked structures, process flow diagram as follows: Figure 1 As shown, it includes: (1) Provide a semiconductor substrate, wherein the semiconductor substrate is a bare silicon wafer; (2) Deposit a film on a bare silicon wafer. First, deposit 300 nm silicon nitride, then deposit 20 nm titanium. Use a resistance meter to detect the thickness of the titanium film and a film thickness meter to measure the thickness of the silicon nitride film. (3) Then the substrate is coated with adhesive, exposed and developed to form a photolithographic pattern; (4) Place the developed substrate into the reaction chamber of the dry etching machine. First, evacuate the reaction chamber and control the temperature to 45°C. Then, introduce the reaction gas into the reaction chamber. Use a mixture of Cl2, BCl3, and Ar as the process gas for plasma dry etching. Control the working pressure of the reaction chamber to 5 mTorr. Turn on the upper coil RF source (TCP RF) and apply an RF power of about 800W to generate high-density plasma. At the same time, turn on the lower bias RF source (Bias RF) and apply a bias power of about 50W to apply ion bombardment energy to the substrate surface. Perform dry etching on the Ti layer. The flow rate of chlorine is 30 sccm, the flow rate of boron trichloride is 15 sccm, the flow rate of argon is 65 sccm, and the etching time is 30s. (5) The etched substrate is then subjected to wet adhesive removal; (6) Finally, the substrate was placed in CDSEM for observation, and the Ti etching morphology and SiN over-etching were observed by SEM.

[0030] The thicknesses of titanium and silicon nitride films were measured using a resistance meter and a film thickness meter, respectively. Based on the initial and final film thickness values, the etching rates of Ti and SiN were calculated to be 8:1.

[0031] SEM cross-sectional image of the etched Ti / SiN stack structure as shown below Figure 2 As shown, by Figure 2 It can be seen that the etched morphology is relatively straight, the underlying SIN loss is less, and the etching selectivity is relatively high.

[0032] Comparative Example 1 The only difference between this comparative example and Example 1 is that, in step (4), the deflection RF power is 100W.

[0033] The etching rates of Ti and SiN are shown in Table 1.

[0034] Testing revealed that the etched morphology was relatively straight, with significant SiN loss in the underlying layer, indicating a low etching selectivity.

[0035] Comparative Example 2 The only difference between this comparative example and Example 1 is that in step (4), the TCP RF power is 500W and the deflection RF power is 100W.

[0036] The etching rates of Ti and SiN are shown in Table 1.

[0037] Upon inspection, the etched morphology was found to be too oblique, failing to meet the requirements, and the underlying SiN loss was significant, indicating a low etching selectivity.

[0038] Comparative Example 3 The only difference between this comparative example and Example 1 is that in step (4), the TCP RF power is 500W, the deflection RF power is 100W, and the working pressure of the reaction chamber is 3mTorr.

[0039] The etching rates of Ti and SiN are shown in Table 1.

[0040] The SEM cross-sectional image of the etched Ti / SiN stacked structure is shown below. Figure 3 As shown, by Figure 3 It can be seen that the etch morphology is relatively oblique, the underlying SiN loss is relatively large, and the etching selectivity is relatively low.

[0041] Comparative Example 4 The only difference between this comparative example and Example 1 is that, in step (4), the deflection RF power is 15W.

[0042] The etching rates of Ti and SiN are shown in Table 1.

[0043] Testing revealed that the etched morphology was oblique, the physical bombardment was weak, there was lateral erosion on the sidewalls, the underlying SiN loss was significant, and the etching selectivity was relatively low.

[0044] Comparative Example 5 The only difference between this comparative example and Example 1 is that the composition of the reaction gas is different in step (4). Specifically, the flow rate of chlorine is 50 sccm, the flow rate of boron trichloride is 8 sccm, and the flow rate of argon is 65 sccm.

[0045] The etching rates of Ti and SiN are shown in Table 1.

[0046] Upon inspection, it was found that the etching exhibited an indentation (a localized internal cutting defect at the junction of the bottom of the sidewall and the bottom surface), indicating insufficient sidewall protection, a relatively straight sidewall angle, and low selectivity for photoresist.

[0047] Comparative Example 6 The only difference between this comparative example and Example 1 is that the composition of the reaction gas is different in step (4). Specifically, the flow rate of chlorine is 15 sccm, the flow rate of boron trichloride is 35 sccm, and the flow rate of argon is 40 sccm.

[0048] The etching rates of Ti and SiN are shown in Table 1.

[0049] Testing revealed that the sidewall angle after etching was too slanted, failing to meet requirements, resulting in significant SiN loss in the underlying layer and a relatively low etching selectivity.

[0050] Comparative Example 7 The only difference between this comparative example and Example 1 is that the composition of the reaction gas is different in step (4). Specifically, the flow rate of chlorine is 30 sccm, the flow rate of boron trichloride is 15 sccm, and the flow rate of argon is 30 sccm.

[0051] The etching rates of Ti and SiN are shown in Table 1.

[0052] Testing revealed that the sidewalls were relatively straight after etching, resulting in significant SiN loss in the underlying layer and a relatively low etching selectivity.

[0053] Comparative Example 8 The only difference between this comparative example and Example 1 is that the composition of the reaction gas is different in step (4). Specifically, the flow rate of chlorine is 30 sccm, the flow rate of boron trichloride is 15 sccm, and the flow rate of argon is 90 sccm.

[0054] The etching rates of Ti and SiN are shown in Table 1.

[0055] Testing revealed that the sidewalls were relatively straight after etching, indicating heavy physical bombardment, damage at the bottom, significant SiN loss in the underlying layer, and a relatively low etching selectivity.

[0056] Example 2 The etching process for Ti / SiN stacked structures includes: (1) Provide a semiconductor substrate, wherein the semiconductor substrate is a bare silicon wafer; (2) Deposit a film on a bare silicon wafer. First, deposit 300 nm silicon nitride, then deposit 20 nm titanium. Use a resistance meter to detect the thickness of the titanium film and a film thickness meter to measure the thickness of the silicon nitride film. (3) Then the substrate is coated with adhesive, exposed and developed to form a photolithographic pattern; (4) Place the developed substrate into the reaction chamber of the dry etching machine. First, evacuate the reaction chamber and control the temperature to 45°C. Then, introduce the reaction gas into the reaction chamber. Use a mixture of Cl2, BCl3, and Ar as the process gas for plasma dry etching. Control the working pressure of the reaction chamber to 3 mTorr. Turn on the upper coil RF source (TCP RF) and apply an RF power of about 600W to generate high-density plasma. At the same time, turn on the lower bias RF source (Bias RF) and apply a bias power of about 30W to apply ion bombardment energy to the substrate surface. Perform dry etching on the Ti layer. The flow rate of chlorine is 20 sccm, the flow rate of boron trichloride is 10 sccm, the flow rate of argon is 50 sccm, and the etching time is 30s. (5) The etched substrate is then subjected to wet adhesive removal; (6) Finally, the substrate was placed in CDSEM for observation, and the Ti etching morphology and SiN over-etching were observed by SEM.

[0057] The etching rates of Ti and SiN are shown in Table 1.

[0058] Testing revealed that the sidewalls were relatively straight after etching, resulting in less SiN loss in the underlying layer and high etching selectivity.

[0059] Example 3 The etching process for Ti / SiN stacked structures includes: (1) Provide a semiconductor substrate, wherein the semiconductor substrate is a bare silicon wafer; (2) Deposit a film on a bare silicon wafer. First, deposit 300 nm silicon nitride, then deposit 20 nm titanium. Use a resistance meter to detect the thickness of the titanium film and a film thickness meter to measure the thickness of the silicon nitride film. (3) Then the substrate is coated with adhesive, exposed and developed to form a photolithographic pattern; (4) Place the developed substrate into the reaction chamber of the dry etching machine. First, evacuate the reaction chamber and control the temperature to 45°C. Then, introduce the reaction gas into the reaction chamber. Use a mixture of Cl2, BCl3, and Ar as the process gas for plasma dry etching. Control the working pressure of the reaction chamber to 8 mTorr. Turn on the upper coil RF source (TCP RF) and apply an RF power of about 1000W to generate high-density plasma. At the same time, turn on the lower bias RF source (Bias RF) and apply a bias power of about 70W to apply ion bombardment energy to the substrate surface. Perform dry etching on the Ti layer. The flow rate of chlorine is 40 sccm, the flow rate of boron trichloride is 20 sccm, the flow rate of argon is 80 sccm, and the etching time is 30s. (5) The etched substrate is then subjected to wet adhesive removal; (6) Finally, the substrate was placed in CDSEM for observation, and the Ti etching morphology and SiN over-etching were observed by SEM.

[0060] The etching rates of Ti and SiN are shown in Table 1.

[0061] Testing revealed that the sidewalls were relatively straight after etching, with less loss of SiN in the underlying layer, indicating a higher etching selectivity.

[0062] Example 4 The etching process for Ti / SiN stacked structures includes: (1) Provide a semiconductor substrate, wherein the semiconductor substrate is a bare silicon wafer; (2) Deposit a film on a bare silicon wafer. First, deposit 300 nm silicon nitride, then deposit 20 nm titanium. Use a resistance meter to detect the thickness of the titanium film and a film thickness meter to measure the thickness of the silicon nitride film. (3) Then the substrate is coated with adhesive, exposed and developed to form a photolithographic pattern; (4) Place the developed substrate into the reaction chamber of the dry etching machine. First, evacuate the reaction chamber and control the temperature to 45°C. Then, introduce the reaction gas into the reaction chamber. Use a mixture of Cl2, BCl3, and Ar as the process gas for plasma dry etching. Control the working pressure of the reaction chamber to 5 mTorr. Turn on the upper coil RF source (TCP RF) and apply an RF power of about 800W to generate high-density plasma. At the same time, turn on the lower bias RF source (Bias RF) and apply a bias power of about 50W to apply ion bombardment energy to the substrate surface. Perform dry etching on the Ti layer. The flow rate of chlorine is 30 sccm, the flow rate of boron trichloride is 20 sccm, the flow rate of argon is 60 sccm, and the etching time is 30s. (5) The etched substrate is then subjected to wet adhesive removal; (6) Finally, the substrate was placed in CDSEM for observation, and the Ti etching morphology and SiN over-etching were observed by SEM.

[0063] The etching rates of Ti and SiN are shown in Table 1.

[0064] Testing revealed that the sidewalls were relatively straight after etching, with less loss of SiN in the underlying layer, indicating a higher etching selectivity.

[0065] Example 5 The etching process for Ti / SiN stacked structures includes: (1) Provide a semiconductor substrate, wherein the semiconductor substrate is a bare silicon wafer; (2) Deposit a film on a bare silicon wafer. First, deposit 300 nm silicon nitride, then deposit 20 nm titanium. Use a resistance meter to detect the thickness of the titanium film and a film thickness meter to measure the thickness of the silicon nitride film. (3) Then the substrate is coated with adhesive, exposed and developed to form a photolithographic pattern; (4) Place the developed substrate into the reaction chamber of the dry etching machine. First, evacuate the reaction chamber and control the temperature to 45°C. Then, introduce the reaction gas into the reaction chamber. Use a mixture of Cl2, BCl3, and Ar as the process gas for plasma dry etching. Control the working pressure of the reaction chamber to 5 mTorr. Turn on the upper coil RF source (TCP RF) and apply an RF power of about 800W to generate high-density plasma. At the same time, turn on the lower bias RF source (Bias RF) and apply a bias power of about 50W to apply ion bombardment energy to the substrate surface. Perform dry etching on the Ti layer. The flow rate of chlorine is 40 sccm, the flow rate of boron trichloride is 20 sccm, the flow rate of argon is 50 sccm, and the etching time is 30s. (5) The etched substrate is then subjected to wet adhesive removal; (6) Finally, the substrate was placed in CDSEM for observation, and the Ti etching morphology and SiN over-etching were observed by SEM.

[0066] The etching rates of Ti and SiN are shown in Table 1.

[0067] Testing revealed that the sidewalls were relatively straight after etching, with less loss of SiN in the underlying layer, indicating a higher etching selectivity.

[0068] Table 1 The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for achieving high selectivity etching of titanium and silicon nitride, characterized in that, The steps include the following: A substrate with a silicon nitride layer and a titanium layer sequentially formed on its surface and patterned is provided; The substrate is subjected to plasma dry etching, and the process gases for the dry etching include chlorine, boron trichloride and argon; and the flow rate ratio of chlorine, boron trichloride and argon is (2~4):(1~2):(5~8).

2. The process method for achieving high selectivity etching of titanium and silicon nitride as described in claim 1, characterized in that, The bias power for the dry etching process is 30~70W.

3. The process method for achieving high selectivity etching of titanium and silicon nitride as described in claim 2, characterized in that, The source power of the dry etching is 600~1000W, preferably 700~900W.

4. The process method for achieving high selectivity etching of titanium and silicon nitride as described in claim 1, characterized in that, The flow rate of chlorine gas is 20-40 sccm, the flow rate of boron trichloride is 10-20 sccm, and the flow rate of argon gas is 50-80 sccm.

5. The process method for achieving high selectivity etching of titanium and silicon nitride as described in claim 1, characterized in that, During the dry etching process, the pressure inside the reaction chamber is 3~8mT.

6. The process method for achieving high selectivity etching of titanium and silicon nitride as described in claim 1, characterized in that, During the dry etching process, the temperature inside the reaction chamber is 40~50℃.

7. The process method for achieving high selectivity etching of titanium and silicon nitride as described in claim 1, characterized in that, The thickness of the silicon nitride layer is 200~400nm; the thickness of the titanium layer is 10~30nm.

8. The process method for achieving high selectivity etching of titanium and silicon nitride as described in claim 1, characterized in that, The substrate of the substrate is silicon.

9. The process method for achieving high selectivity etching of titanium and silicon nitride as described in claim 1, characterized in that, After the plasma dry etching, the substrate is further subjected to wet resist removal.

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