ICP etching method for ultra-thin metal layer and its application

Abstract

The present invention belongs to the field of device processing and manufacturing. The present invention provides an ICP etching method for an ultra-thin metal layer and its application. The ICP etching method comprises first performing a first ICP etching to remove at least the ultra-thin metal layer outside the groove to form a removal area, then depositing a polymer layer in the removal area by ICP to protect the removal area, then performing a second ICP etching to remove the ultra-thin metal layer inside the groove, and finally removing the remaining polymer layer by ICP cleaning; the present invention adds a deposition step of a polymer layer, so that the polymer plays a protective effect outside the groove, so that the difference in etching rate between the metal outside and inside the groove is compensated, and the problem of poor etching rate uniformity caused by different depths is improved. The solution can be used on traditional ICP equipment, can bypass the use restrictions of ALE technology, has low requirements for equipment configuration, effectively saves costs and improves etching rate.

Description

Technical Field

[0001] The invention belongs to the technical field of device processing and manufacturing, and relates to an ICP etching method for an ultra-thin metal layer and application thereof. Background Art

[0002] With the rapid development of microelectronics technology, the integration of electronic devices is getting higher and higher, and the corresponding microstructure size is also shrinking. This trend requires the manufacturing process to have higher precision and reliability to ensure the continuous improvement of device performance. Among many manufacturing processes, etching technology is one of the key steps to achieve fine pattern transfer. It not only affects the dimensional accuracy of the device, but also directly affects the electrical performance and reliability of the device. Therefore, how to accurately control the amount of material removed at the nanoscale has become an important issue in the field of microelectronics manufacturing.

[0003] In the manufacture of modern microelectronic devices, wafer etching technology mainly involves transferring mask patterns to the underlying material to form the required functional structure. In particular, for the etching of ultra-thin metal layers, the etching process is required to accurately control the etching position, depth and morphology, especially to ensure that the etched metal layer has a uniform thickness and does not damage the underlying material.

[0004] Traditional etching techniques mainly include dry etching and wet etching. Among them, dry etching techniques such as inductively coupled plasma etching (ICP) are widely used in the manufacture of microelectronic devices. However, ICP etching technology has some limitations. For example, since the high-energy particles used in the ICP etching process will damage the surface of the material, especially when etching the top of the groove, the etching rate is often uneven, resulting in the metal layer at the top of the groove being etched in advance, while the material at the bottom of the groove is not completely removed, which can easily cause unnecessary etching damage to the underlying material exposed in the over-etched area, affecting the performance of the device.

[0005] In order to overcome the limitations of traditional etching technology at the nanoscale, atomic layer etching (ALE) technology came into being. ALE technology uses a unique cyclic etching mechanism that can accurately control the material removal process at the atomic layer level, thereby achieving high-quality etching of ultra-thin metal layers. The core of ALE technology lies in its cyclic etching process based on gas delivery and ion bombardment, which specifically includes four steps. Step 1 is the delivery of etching gas. The etching gas is transported into the reaction chamber and adsorbed on the etched material after plasma dissociation and reacts with it. By selecting the appropriate gas and delivery amount, this step can be stopped after the gas adsorbs only one layer of molecules; Step 2 is to remove the remaining delivery gas in the chamber; Step 3 is to bombard the etching material with low-energy ions to remove the surface layer that has reacted. This step requires appropriate ion energy so that the energy of the ions can remove the chemically modified surface layer, but is not enough to sputter and etch the underlying material; Step 4 is to remove the reaction products in the chamber to prepare for the next cycle.

[0006] Although ALE technology can be used to remove ultra-thin layers and has the advantages of high selectivity and good uniformity, it also faces some challenges in practical applications. First, the equipment required to implement ALE technology is usually expensive and has high maintenance costs. This is mainly because the ALE process has extremely high requirements on the precision of the equipment, requiring a precise gas control system, plasma source, and ion bombardment device. Secondly, since ALE technology can only remove one layer of molecules per cycle, its etching rate is relatively slow. For large-scale production, this may lead to low production efficiency, thus affecting economic benefits.

[0007] From the above, it can be seen that in view of the problems existing in traditional etching technology and ALE technology, developing an etching solution that can reduce costs and increase etching rate has become an urgent problem to be solved. Summary of the invention

[0008] In view of the problems existing in the prior art, the purpose of the present invention is to provide an ICP etching method for an ultra-thin metal layer and its application, wherein the ICP etching method comprises first performing a first ICP etching to remove at least the ultra-thin metal layer outside the groove to form a removal area, then depositing a polymer layer in the removal area to protect the substrate, then performing a first ICP etching to remove the ultra-thin metal layer inside the groove, and finally removing the remaining polymer layer by ICP cleaning; the present invention adds a deposition step of a polymer layer, so that the polymer plays a protective effect outside the groove, so that the difference in etching rate between the metal outside and inside the groove is compensated, and the problem of poor etching rate uniformity caused by different depths is improved. This solution can be used on traditional ICP equipment, can bypass the use restrictions of ALE technology, has low requirements for equipment configuration, effectively saves costs and improves etching rate.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides an ICP etching method for an ultra-thin metal layer, comprising:

[0011] Providing a substrate having a groove, wherein the outside and inside of the groove are covered with an ultra-thin metal layer;

[0012] Performing a first ICP etching to remove the ultra-thin metal layer outside the groove, and at the same time subjecting the ultra-thin metal layer inside the groove to etching to form a removal area at least covering the outside of the groove;

[0013] Performing ICP deposition to form a polymer layer at least covering the removal area;

[0014] Performing a second ICP etching to remove the remaining ultra-thin metal layer inside the groove, while keeping the polymer layer in the removal area not completely etched, so as to protect the substrate outside the groove covered by the polymer layer from being etched;

[0015] ICP cleaning was performed to remove the remaining polymer layer.

[0016] In the present invention, the ultra-thin metal layer outside the groove refers to the ultra-thin metal layer covering the top surfaces of the ridges on both sides of the groove or the platforms on both sides (hereinafter referred to as the groove top), and the ultra-thin metal layer inside the groove refers to the ultra-thin metal layer covering the bottom and inner sidewall inside the groove.

[0017] The present invention adds a deposition step of a polymer layer so that the polymer plays a protective role outside the groove, so that the difference in etching rate between the metal outside and inside the groove is compensated, and the problem of poor etching rate uniformity caused by different depths is improved. That is, the present invention implements groove external etching, polymer deposition, groove internal etching and polymer cleaning through the first ICP etching, the ICP deposition, the second ICP etching and the ICP cleaning, so that the ultra-thin metal layer from the outside to the inside of the groove is completely removed, and due to the protective effect of the polymer layer, the entire etching process causes little damage to the underlying material of the ultra-thin metal layer or the substrate itself, and this method can be used on traditional ICP etching equipment. The method belongs to dry etching using ICP technology, which can bypass the use restrictions of ALE technology, has low requirements for equipment configuration, effectively saves costs and improves etching rate.

[0018] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0019] As a preferred technical solution of the present invention, during the processes of the first ICP etching, the ICP deposition, the second ICP etching and the ICP cleaning, only source power RF is used, and bias power RF is not used.

[0020] In conventional ICP (Inductively Coupled Plasma) etching methods and devices, two main radio frequencies are usually included, which act together on the ICP etching system through specific configuration and control methods to achieve an efficient and accurate etching process. One is the inductively coupled plasma source power radio frequency (i.e., source power). The power supply of this radio frequency is mainly connected to the spiral coil outside the ICP chamber. By generating a high-frequency alternating current signal, a high-frequency alternating magnetic field is formed around the spiral coil, and then a high-frequency electric field is induced in the chamber to excite the etching gas to form plasma. The radio frequency generated by this power supply can be regarded as the "source" of plasma generation, so the present invention is referred to as "source power radio frequency". The second is the bias power radio frequency (i.e., bias power). The power supply of this radio frequency is connected to the electrode at the bottom of the ICP chamber (i.e., "bias electrode" or "lower electrode"), which provides radio frequency energy to the electrode, so that the ions in the plasma obtain sufficient energy to bombard and etch the surface of the substrate placed on the electrode. This radio frequency is mainly used to control the energy and etching rate of the ions.

[0021] In the present invention, since only the transmitter radio frequency is used, the ions in the plasma have weak bombardment on the etched material and the etching rate is extremely slow, so the amount of material etching can be accurately controlled. Since no bias power radio frequency is used, the directionality of the ions is poor, which intensifies the collision between particles and between particles and the side walls in the groove. The ions lose more energy when reaching the deep part of the groove, so the etching rate at the top of the groove is faster than the etching rate at the bottom of the groove. That is, in the first ICP etching process of the present invention using only source power RF, during the etching of the ultra-thin metal layer outside the groove, the ultra-thin metal layer inside the groove is also etched, but the portion closer to the groove opening is more strongly etched, and as the depth increases, the portion closer to the bottom of the groove is less etched. Therefore, possible situations include: after the ultra-thin metal layer outside the groove is etched cleanly, a portion of the ultra-thin metal layer covering the inner side wall near the groove opening inside the groove is also etched and completely removed, which together with the etched area outside the groove forms the removal area, and another portion of the groove inside near the bottom still has the ultra-thin metal layer that has not been completely removed and leaves an ultra-thin metal residual layer, and then after a polymer layer is applied to the removal area for protection, the ultra-thin metal residual layer can be removed in a subsequent second ICP etching. Another possible situation includes that after the ultra-thin metal layer outside the groove is etched clean, the ultra-thin metal layer inside the groove is etched and only partially etched, and there is no completely removed area. Therefore, the removal area formed at this time only includes the area that has been etched outside the groove. Therefore, the present invention defines the removal area as "at least covering the outside of the groove."

[0022] Preferably, during the first ICP etching, the ICP deposition, the second ICP etching and the ICP cleaning, the flow direction of the working gas (including the etching gas, deposition gas, cleaning gas and auxiliary gas described below) flows from directly above the substrate to both sides of the substrate.

[0023] Preferably, the substrate is held on an electrostatic chuck (ESC).

[0024] As a preferred technical solution of the present invention, the material of the layer in the substrate that is in contact with the ultra-thin metal layer includes SiO2.

[0025] Preferably, the substrate comprises a wafer.

[0026] Preferably, the thickness of the ultra-thin metal layer is 2-3 nm, for example, 2 nm, 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm, 2.5 nm, 2.6 nm, 2.7 nm, 2.8 nm, 2.9 nm or 3 nm.

[0027] As a preferred technical solution of the present invention, during the processes of the first ICP etching, the ICP deposition, the second ICP etching and the ICP cleaning, the operating temperature of the substrate is maintained at 100-170°C.

[0028] Preferably, before performing the first ICP etching, the substrate is preheated to reach the working temperature, and the preheating time is 60 to 120 seconds, for example, 60 seconds, 70 seconds, 80 seconds, 90 seconds, 100 seconds, 110 seconds or 120 seconds, etc., preferably 90 seconds.

[0029] In the present invention, the purpose of preheating is to transfer the heat of the ESC evenly to the surface of the substrate (such as a wafer), so that the substrate and the surface of the ESC are at the same temperature before starting the subsequent process.

[0030] As a preferred technical solution of the present invention, the etching gas of the first ICP etching includes Cl2 and / or BCl3.

[0031] Preferably, the etching gas of the first ICP etching includes Cl2 and BCl3, wherein the flow rate of Cl2 is 50~90sccm, for example, 50sccm, 55sccm, 60sccm, 65sccm, 70sccm, 75sccm, 80sccm, 85sccm or 90sccm, and the flow rate of BCl3 is 100~200sccm, for example, 100sccm, 110sccm, 120sccm, 130sccm, 140sccm, 150sccm, 160sccm, 170sccm, 180sccm, 190sccm or 200sccm, etc.

[0032] Preferably, the auxiliary gas for the first ICP etching includes Ar, and the flow rate of Ar is 0~100sccm, for example, 0sccm (i.e., no auxiliary gas is used), 10sccm, 20sccm, 30sccm, 40sccm, 50sccm, 60sccm, 70sccm, 80sccm, 90sccm or 100sccm, etc.

[0033] Preferably, the pressure in the chamber of the first ICP etching is 30-40 mtorr, for example, 30 mtorr, 32 mtorr, 34 mtorr, 36 mtorr, 38 mtorr or 40 mtorr.

[0034] Preferably, the RF power of the generator of the first ICP etching is 1200~1700W, for example, 1200W, 1250W, 1300W, 1350W, 1400W, 1450W, 1500W, 1550W, 1600W, 1650W or 1700W, and the power of the bias power RF is 0W (i.e., the bias power RF is not used).

[0035] Preferably, the first ICP etching time is 14 to 21 s, for example, 14 s, 15 s, 16 s, 17 s, 18 s, 19 s, 20 s or 21 s.

[0036] In the present invention, the time of the first ICP etching and the second ICP etching should be reasonably selected and adjusted according to the thickness of the ultra-thin metal layer to be removed. Specifically, the end time of the first ICP etching is determined according to the thickness of the ultra-thin metal layer outside the groove.

[0037] As a preferred technical solution of the present invention, the deposition gas of the ICP deposition includes CH4, and the flow rate of the deposition gas is 15~30sccm, for example, 15sccm, 18sccm, 20sccm, 22sccm, 24sccm, 26sccm, 28sccm or 30sccm, etc.

[0038] In the present invention, CH4 is preferably used as the deposition gas because the molecular weight of CH4 itself and the polymer generated by CH4 are both small and easy to diffuse. Therefore, CH4 can be used to evenly cover the entire wafer with CH polymer to form the polymer layer, and the thickness of the CH polymer outside the groove is significantly greater than the thickness of the CH polymer at the bottom of the groove, so that in the subsequent etching step, the CH polymer can well protect the outside of the groove and will not hinder the etching of the inside of the groove.

[0039] Preferably, the auxiliary gas for the ICP deposition includes Ar, and the flow rate of the auxiliary gas is 70-100 sccm, for example, 70 sccm, 75 sccm, 80 sccm, 85 sccm, 90 sccm, 95 sccm or 100 sccm.

[0040] Preferably, the power of the source power RF of the ICP deposition is 700~1000W, for example, 700W, 750W, 800W, 850W, 900W, 950W or 1000W, etc., for example, the power of the bias power RF is 0W (that is, the bias power RF is not used).

[0041] Preferably, the pressure in the ICP deposition chamber is 6-10 mtorr, for example, 6 mtorr, 6.5 mtorr, 7 mtorr, 7.5 mtorr, 8 mtorr, 8.5 mtorr, 9 mtorr, 9.5 mtorr or 10 mtorr.

[0042] Preferably, the ICP deposition time is 5 to 10 s, for example, 5 s, 5.5 s, 6 s, 6.5 s, 7 s, 7.5 s, 8 s, 8.5 s, 9 s, 9.5 s or 10 s.

[0043] As a preferred technical solution of the present invention, the thickness of the polymer layer outside the groove is 3~7nm, for example, 3nm, 3.3nm, 3.5nm, 3.8nm, 4nm, 4.3nm, 4.5nm, 4.8nm, 5nm, 5.2nm, 5.5nm, 5.8nm, 6nm, 6.2nm, 6.5nm, 6.8nm or 7nm, etc.

[0044] In the present invention, when the ICP deposition described in the present invention only uses source power to deposit on the removal area outside the groove, the removal area inside the groove is also affected by the deposition, but the farther away from the groove opening, the weaker the deposition effect. As the depth increases, the polymer layer deposited on the side wall closer to the bottom of the inner groove is thinner. It may also happen that part of the inner side wall is not covered with the polymer layer. In other words, the thickness of the polymer layer deposited by ICP conforms to the etching degree of the first ICP etching. The places with a large etching degree (such as the outside of the groove) can form a thicker polymer layer for protection so as not to be completely etched in the second ICP etching, while the places with a small etching degree (such as the inner side wall and bottom near the bottom of the inner groove) form a thinner polymer layer so that after being etched in the second ICP etching, the ultra-thin metal residual layer can continue to be etched, thereby achieving both etching buffering and complete etching without damage.

[0045] As a preferred technical solution of the present invention, the etching gas of the second ICP etching includes Cl2 and / or BCl3.

[0046] In the present invention, the second ICP etching is used to etch the ultra-thin metal layer at the bottom of the groove (because the outside of the groove is protected by the polymer layer). Since the gas input contains Ar and BCl3, the plasma generated by Ar and BCl3 contains some ions with larger molecular weight, which have a strong bombardment effect on the material and will etch away a polymer layer formed by CH polymer of a certain thickness. Therefore, it is necessary to ensure that the deposited polymer layer, especially the area outside the groove is thick enough and is not completely etched in the second ICP etching. The time of the second ICP etching is determined by the thickness of the remaining ultra-thin metal layer at the bottom of the groove.

[0047] Preferably, the etching gas of the second ICP etching includes Cl2 and BCl3, wherein the flow rate of Cl2 is 50~90sccm, for example, 50sccm, 55sccm, 60sccm, 65sccm, 70sccm, 75sccm, 80sccm, 85sccm or 90sccm, and the flow rate of BCl3 is 100~200sccm, for example, 100sccm, 110sccm, 120sccm, 130sccm, 140sccm, 150sccm, 160sccm, 170sccm, 180sccm, 190sccm or 200sccm, etc.

[0048] Preferably, the auxiliary gas for the second ICP etching includes Ar, and the flow rate of Ar is 0~100sccm, for example, 0sccm (i.e., no auxiliary gas is used), 10sccm, 20sccm, 30sccm, 40sccm, 50sccm, 60sccm, 70sccm, 80sccm, 90sccm or 100sccm, etc.

[0049] Preferably, the pressure in the chamber of the second ICP etching is 30-40 mtorr, for example, 30 mtorr, 32 mtorr, 34 mtorr, 36 mtorr, 38 mtorr or 40 mtorr.

[0050] In the present invention, the slightly lower strong pressure of 30-40 mtorr in the middle chamber of the second ICP etching can make the etching products deep in the groove volatilize more quickly, thereby increasing the etching rate at the bottom of the groove.

[0051] Preferably, the power of the source power RF of the second ICP etching is 1200~1700W, for example, 1200W, 1250W, 1300W, 1350W, 1400W, 1450W, 1500W, 1550W, 1600W, 1650W or 1700W, and the power of the bias power RF is 0W (that is, the bias power RF is not used).

[0052] Preferably, the second ICP etching time is 14-21 s, for example, 14 s, 15 s, 16 s, 17 s, 18 s, 19 s, 20 s or 21 s.

[0053] As a preferred technical solution of the present invention, the cleaning gas for ICP cleaning includes O2, and the flow rate of the cleaning gas is 200~300sccm, for example, 200sccm, 210sccm, 220sccm, 230sccm, 240sccm, 250sccm, 260sccm, 270sccm, 280sccm, 290sccm or 300sccm, etc.

[0054] Preferably, the auxiliary gas for ICP cleaning includes N2, and the flow rate of the auxiliary gas is 20-50 sccm, for example, 20 sccm, 25 sccm, 30 sccm, 35 sccm, 40 sccm, 45 sccm or 50 sccm.

[0055] In the present invention, N2 is preferably added to the ICP cleaning to prevent the O radicals in the O2 plasma from recombining, thereby promoting the removal efficiency of the polymer layer formed by the CH polymer by the O2 plasma.

[0056] Preferably, the source power RF power of the ICP cleaning is 800~1200W, for example, 800W, 850W, 900W, 950W, 1000W, 1050W, 1100W, 1150W or 1200W, and the bias power RF power is 0W (i.e., bias power RF is not used).

[0057] Preferably, the pressure in the chamber of the ICP cleaning is 10-15 mtorr, for example, 10 mtorr, 10.5 mtorr, 11 mtorr, 11.5 mtorr, 12 mtorr, 12.5 mtorr, 13 mtorr, 13.5 mtorr, 14 mtorr, 14.5 mtorr or 15 mtorr, etc.

[0058] Preferably, the ICP cleaning time is monitored by OES to obtain the end point.

[0059] In the present invention, the ICP cleaning time is based on when the polymer layer is completely removed, and the OES can be used to capture the end point.

[0060] In a second aspect, the present invention provides a wafer, wherein the wafer is processed according to the ICP etching method of the ultra-thin metal layer described in the first aspect.

[0061] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0062] The ICP etching method for the ultra-thin metal layer of the present invention adds a deposition step of a polymer layer so that the polymer plays a protective role outside the groove, so that the difference in etching rate between the metal outside and inside the groove is compensated, and the problem of poor etching rate uniformity caused by different depths is improved, so that the ultra-thin metal layer from the outside to the inside of the groove is completely removed, and due to the protective effect of the polymer layer, the entire etching process causes little damage to the underlying material of the ultra-thin metal layer or the substrate itself, and this method can be used on traditional ICP etching equipment. The method belongs to dry etching using ICP technology, which can bypass the use restrictions of ALE technology, has low requirements on equipment configuration, effectively saves costs and improves etching rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 is a schematic diagram of step (1) in the ICP etching method for an ultra-thin metal layer of Example 1;

[0064] Figure 2 is a schematic diagram of step (2) in the ICP etching method for an ultra-thin metal layer of Example 1;

[0065] Figure 3 is a schematic diagram of step (3) in the ICP etching method for an ultra-thin metal layer of Example 1;

[0066] Figure 4 is a schematic diagram of step (4) in the ICP etching method for an ultra-thin metal layer of Example 1;

[0067] Figure 5 is a schematic diagram of step (5) in the ICP etching method for an ultra-thin metal layer of Example 1;

[0068] In the figure, 1-substrate, 2-groove, 3-ultra-thin metal layer, 4-polymer layer. DETAILED DESCRIPTION

[0069] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0070] It should be clear to those skilled in the art that the embodiments are only intended to help understand the present invention and should not be considered as specific limitations of the present invention.

[0071] Example 1

[0072] This embodiment provides an ICP etching method for an ultra-thin metal layer. Figures 1 to 5 As shown, including:

[0073] (1) A substrate 1 having a groove 2 is provided. The substrate 1 is a wafer having a diameter of 300 mm. The outside of the groove 2 and the inside of the groove 2 are covered with a SiO2 layer. The thickness of the SiO2 layer is 5 nm. The SiO2 layer is covered with an ultra-thin metal layer 3 having a thickness of 2 nm, such as Figure 1 As shown;

[0074] The wafer is transferred into the chamber of the inductively coupled plasma etcher, and the ESC is heated to the operating temperature of 150°C. The ESC temperature is then kept constant, and the wafer and the ESC surface are kept at the same temperature before the next step is started.

[0075] (2) Perform the first ICP etching: introduce etching gas and auxiliary gas, control the Cl2 flow rate to 70sccm, the BCl3 flow rate to 170sccm, and the Ar flow rate to 70sccm, adjust the pendulum opening to control the pressure in the chamber to 35mtorr, set the source power RF power to 1300w, and the bias power RF power to 0w, and etch for 14s to remove the ultra-thin metal layer 3 outside the groove 2. At the same time, the ultra-thin metal layer 3 inside the groove 2 is etched, so that the side wall area inside the groove 2 close to the opening of the groove 2 is also removed, forming a removal area, such as Figure 2 As shown;

[0076] (3) Perform ICP deposition: introduce deposition gas and auxiliary gas, control the CH4 flow rate to 24ccm, the Ar flow rate to 70sccm, the source power RF power to 950w, the bias power RF power to 0w, adjust the pendulum opening to make the chamber pressure 7mtorr, deposit for 8s, generate CH polymer in the removal area to form a polymer layer 4, and the thickness of the polymer layer 4 outside the groove 2 is significantly greater than the thickness of the polymer layer 4 at the bottom of the groove 2, and the thickness of the polymer layer outside the groove is 5nm, as shown in FIG. Figure 3 As shown;

[0077] (4) Perform a second ICP etching, introduce etching gas and auxiliary gas, control the Cl2 flow rate to 70sccm, BCl3 flow rate to 170sccm, Ar flow rate to 70sccm, adjust the pendulum opening to control the pressure in the chamber to 30mtorr, the source power RF power is 1300w, the bias power RF power is 0w, remove the ultra-thin metal layer 3 at the bottom of the groove 2, use OES to capture the etching endpoint to keep the polymer layer 4 in the removal area from being completely etched, so that the exposed SiO2 layer in the removal area is not etched, as shown in FIG. Figure 4 As shown;

[0078] (5) Perform ICP cleaning: introduce cleaning gas and auxiliary gas, control the flow rate of O2 to 300sccm, adjust the pendulum opening to control the pressure in the chamber at 15mtorr, set the source power RF power to 1000w, and the bias power RF power to 0w. Use OES to capture the endpoint and remove the residual polymer layer 4, such as Figure 5 shown.

[0079] Example 2

[0080] This embodiment provides an ICP etching method for an ultra-thin metal layer, comprising:

[0081] (1) Providing a substrate having a groove, the substrate being a wafer, the size of the wafer being a diameter of 203 mm, and the outside and inside of the groove being covered with a SiO2 layer, the thickness of the SiO2 layer being 5 nm, and the SiO2 layer being covered with a 3 nm thick ultra-thin metal layer; the ultra-thin metal layer being an aluminum oxide (Al2O3) layer;

[0082] The wafer is transferred into the chamber of the inductively coupled plasma etcher, and the ESC is heated to the operating temperature of 170°C. The ESC temperature is then kept constant, and the wafer and the ESC surface are kept at the same temperature before the next step is started.

[0083] (2) Perform the first ICP etching: introduce etching gas and auxiliary gas, control the Cl2 flow rate to 50sccm, the BCl3 flow rate to 150sccm, the Ar flow rate to 50sccm, adjust the pendulum opening to control the pressure in the chamber to 30mtorr, set the source power RF power to 1200w, and the bias power RF power to 0w. Etch for 20s to remove the ultra-thin metal layer outside the groove. At the same time, the ultra-thin metal layer inside the groove is etched, so that the side wall area inside the groove close to the groove opening is also removed to form a removal area;

[0084] (3) Perform ICP deposition: introduce deposition gas and auxiliary gas, control the CH4 flow rate to 17ccm, the Ar flow rate to 85sccm, the source power RF power to 780w, the bias power RF power to 0w, adjust the pendulum opening to make the chamber pressure 8.5mtorr, deposit for 9s, generate CH polymer in the removal area to form a polymer layer, the thickness of the polymer layer outside the groove is 5nm, and the thickness of the polymer layer outside the groove is significantly greater than the thickness of the polymer layer at the bottom of the groove;

[0085] (4) Perform a second ICP etching, introduce etching gas and auxiliary gas, control the Cl2 flow rate to 50sccm, the BCl3 flow rate to 150sccm, the Ar flow rate to 50sccm, adjust the pendulum opening to control the pressure in the chamber to 30mtorr, the source power RF power to 1200w, the bias power RF power to 0w, remove the ultra-thin metal layer at the bottom of the groove, use OES to capture the etching endpoint to keep the polymer layer in the removal area from being completely etched, so that the exposed SiO2 layer in the removal area is not etched;

[0086] (5) Perform ICP cleaning: introduce cleaning gas and auxiliary gas, control the O2 flow rate to 200sccm, adjust the pendulum opening to control the pressure in the chamber at 13mtorr, set the source power RF power to 1200w, set the bias power RF power to 0w, use OES to capture the endpoint and remove the residual polymer layer.

[0087] Example 3

[0088] This embodiment provides an ICP etching method for an ultra-thin metal layer, comprising:

[0089] (1) Providing a substrate having a groove, the substrate being a wafer, the size of the wafer being 300 mm in diameter, and the outside and inside of the groove being covered with a SiO2 layer, the thickness of the SiO2 layer being 5 nm, and the SiO2 layer being covered with a 2.5 nm thick ultra-thin metal layer; the ultra-thin metal layer being a gallium arsenide (GaAs) layer;

[0090] The wafer is transferred into the chamber of the inductively coupled plasma etcher, and the ESC is heated to the operating temperature of 130°C. The ESC temperature is then kept constant, and the wafer and the ESC surface are kept at the same temperature before the next step is started.

[0091] (2) Perform the first ICP etching: introduce etching gas and auxiliary gas, control the Cl2 flow rate to 55sccm, the BCl3 flow rate to 200sccm, the Ar flow rate to 30sccm, adjust the pendulum opening to control the pressure in the chamber to 40mtorr, set the source power RF power to 1700w, and the bias power RF power to 0w. Etch for 19s to remove the ultra-thin metal layer outside the groove. At the same time, the ultra-thin metal layer inside the groove is etched, so that the side wall area inside the groove close to the groove opening is also removed to form a removal area;

[0092] (3) Perform ICP deposition: introduce deposition gas and auxiliary gas, control the CH4 flow rate to 30ccm, the Ar flow rate to 100sccm, the source power RF power to 1000w, the bias power RF power to 0w, adjust the pendulum opening to make the chamber pressure 10mtorr, deposit for 10s, generate CH polymer in the removal area to form a polymer layer, the thickness of the polymer layer outside the groove is 6nm, and the thickness of the polymer layer outside the groove is significantly greater than the thickness of the polymer layer at the bottom of the groove;

[0093] (4) Perform a second ICP etching, introduce etching gas and auxiliary gas, control the Cl2 flow rate to 90sccm, the BCl3 flow rate to 200sccm, the Ar flow rate to 80sccm, adjust the pendulum opening to control the pressure in the chamber to 36mtorr, the source power RF power to 1500w, the bias power RF power to 0w, remove the ultra-thin metal layer at the bottom of the groove, use OES to capture the etching endpoint to keep the polymer layer in the removal area from being completely etched, so that the exposed SiO2 layer in the removal area is not etched;

[0094] (5) Perform ICP cleaning: introduce cleaning gas and auxiliary gas, control the flow rate of O2 to 280sccm, control the flow rate of N2 to 25sccm, adjust the pendulum opening to control the pressure in the chamber at 15mtorr, set the source power RF power to 900w, set the bias power RF power to 0w, use OES to capture the endpoint and remove the residual polymer layer.

[0095] Example 4

[0096] This embodiment provides an ICP etching method for an ultra-thin metal layer. In the ICP etching method, in step (2), the time of the first ICP etching is adjusted from 14 seconds to 7 seconds. Except for the above, other conditions are exactly the same as those in Example 1.

[0097] Example 5

[0098] This embodiment provides an ICP etching method for an ultra-thin metal layer. In the ICP etching method, in step (2), the time of the first ICP etching is adjusted from 14 s to 21 s. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0099] Example 6

[0100] This embodiment provides an ICP etching method for an ultra-thin metal layer. In the ICP etching method, in step (3), the ICP deposition time is adjusted from 8 s to 4 s, and the thickness of the polymer layer outside the groove is 3 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0101] Example 7

[0102] This embodiment provides an ICP etching method for an ultra-thin metal layer. In the ICP etching method, in step (3), the ICP deposition time is adjusted from 8 s to 16 s, and the thickness of the polymer layer outside the groove is 9 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0103] Example 8

[0104] This embodiment provides an ICP etching method for an ultra-thin metal layer. In the ICP etching method, in step (4), the time of the second ICP etching is adjusted from using OES to determine the etching endpoint to 20 seconds. Except for the above, other conditions are exactly the same as those in Example 1.

[0105] Example 9

[0106] This embodiment provides an ICP etching method for an ultra-thin metal layer. In the ICP etching method, in step (4), the time of the second ICP etching is adjusted from using OES to determine the etching endpoint to 30 seconds. Except for the above, other conditions are exactly the same as those in Example 1.

[0107] Comparative Example 1

[0108] This comparative example provides an ICP etching method for an ultra-thin metal layer, wherein the ICP etching method does not deposit a protective layer such as a polymer layer, and only uses source power radio frequency for etching. The ICP etching method comprises:

[0109] S1. A substrate having a groove is provided, wherein the substrate is a wafer having a size of 300 mm in diameter, and the outer portion and the inner portion of the groove are covered with a SiO2 layer, the thickness of the SiO2 layer is 5 nm, and the SiO2 layer is covered with a 2 nm thick ultra-thin metal layer;

[0110] The wafer is transferred into the chamber of the inductively coupled plasma etcher, and the ESC is heated to the operating temperature of 150°C. The ESC temperature is then kept constant, and the wafer and the ESC surface are kept at the same temperature before the next step is started.

[0111] S2. Perform ICP etching: introduce etching gas and auxiliary gas, control the Cl2 flow rate to 70sccm, BCl3 flow rate to 170sccm, Ar flow rate to 70sccm, adjust the pendulum opening to control the pressure in the chamber at 35mtorr, set the source power RF power to 1300w, and the bias power RF power to 0w, use OES to capture the etching end point until all the ultra-thin metal layers in the groove are removed.

[0112] Comparative Example 2

[0113] This comparative example provides an ICP etching method for an ultra-thin metal layer, wherein the ICP etching method does not deposit a protective layer such as a polymer layer, and uses source power radio frequency and bias power radio frequency for etching, and the ICP etching method comprises:

[0114] S1. A substrate having a groove is provided, wherein the substrate is a wafer having a diameter of 300 mm, and the outer and inner portions of the groove are covered with a SiO2 layer, and the SiO2 layer is covered with an ultra-thin metal layer having a thickness of 2 nm;

[0115] The wafer is transferred into the chamber of the inductively coupled plasma etcher, and the ESC is heated to the operating temperature of 150°C. The ESC temperature is then kept constant, and the wafer and the ESC surface are kept at the same temperature before the next step is started.

[0116] S2. Perform ICP etching: introduce etching gas and auxiliary gas, control the Cl2 flow rate to 70sccm, BCl3 flow rate to 170sccm, Ar flow rate to 70sccm, adjust the pendulum opening to control the pressure in the chamber at 35mtorr, set the source power RF power to 1300w, and the bias power RF power to 20w, use OES to capture the etching end point until all the ultra-thin metal layers in the groove are removed.

[0117] Characterization and Testing:

[0118] The wafers processed in the embodiment and the comparative example were inspected and sent to FIB-TEM for photographing to observe the etching conditions:

[0119] Compared with Example 1, the metal layer outside the groove in Example 4 was not etched cleanly, and there was metal residue on the top of the groove, indicating that the short first ICP etching time could not completely remove the metal outside the groove;

[0120] Compared with Example 1, the metal layer outside the groove in Example 5 is completely etched, but the SiO2 layer under the ultra-thin metal layer outside the groove is consumed more, indicating that the excessively long first ICP etching time will cause the SiO2 layer below to be consumed after the ultra-thin metal layer outside the groove is etched away;

[0121] Compared with Example 1, the polymer layer deposited in Example 6 is not thick enough to protect the SiO2 layer outside the trench during the second ICP etching and is consumed;

[0122] Compared with Example 1, the deposited polymer layer in Example 7 is too thick and covers the middle and bottom of the groove, resulting in that the ultra-thin metal layer at the middle and bottom of the groove cannot be etched during the second ICP etching process;

[0123] Compared with Example 1, in Example 8, the ultra-thin metal layer at the bottom of the groove is completely etched and the SiO2 layer at the bottom of the groove is lost, indicating that too long a second ICP etching time will damage the SiO2 layer at the bottom of the groove.

[0124] Compared with Example 1, the ultra-thin metal layer at the bottom of the groove in Example 9 is completely etched away, and compared with Example 8, the SiO2 layer inside the groove is more consumed.

[0125] The images taken for Example 1, Comparative Example 1 and Comparative Example 2 were imported into the TEM measurement software for measurement, and the thickness of each film layer before and after etching was measured, as shown in Table 1:

[0126]

[0127] It can be seen from Table 1 that in Comparative Example 1, in the absence of the step of depositing the polymer layer by ICP, after the ultra-thin metal inside the groove is etched clean, the SiO2 film layer outside the groove will be etched, with a loss of 4nm. In Comparative Example 2, in the absence of the ICP deposited polymer layer, and when the biased radio frequency is turned on, after the metal inside the groove is etched clean, the SiO2 film layer outside the groove is severely lost, almost completely lost, and the substrate is also over-etched. The etching-deposition-etching process in the ICP etching method in Example 1 of the present invention causes the least damage to the SiO2 film layer compared to the one-step etching, and can completely remove the ultra-thin metal layer while almost not damaging the underlying SiO2, thereby improving the problem of poor etching rate uniformity caused by different depths.

[0128] From the above, it can be seen that the ICP etching method of the ultra-thin metal layer of the present invention adds a deposition step of a polymer layer, so that the polymer plays a protective effect on the outside of the groove, so that the difference in etching rate between the metal outside and inside the groove is compensated, and the problem of poor etching rate uniformity caused by different depths is improved, so that the ultra-thin metal layer from the outside to the inside of the groove is completely removed, and due to the protective effect of the polymer layer, the entire etching process causes little damage to the underlying material of the ultra-thin metal layer or the substrate itself, and this method can be used on traditional ICP etching equipment. The method belongs to dry etching using ICP technology, which can bypass the use restrictions of ALE technology, has low requirements on equipment configuration, effectively saves costs and improves etching rate.

[0129] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0130] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0131] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. An ICP etching method for an ultra-thin metal layer, characterized in that: include: Providing a substrate having a groove, wherein the outside and inside of the groove are covered with an ultra-thin metal layer; the thickness of the ultra-thin metal layer is 2-3 nm; Performing a first ICP etching to remove the ultra-thin metal layer outside the groove, and at the same time subjecting the ultra-thin metal layer inside the groove to etching to form a removal area at least covering the outside of the groove; The etching gas of the first ICP etching includes Cl2 and / or BCl3; wherein the flow rate of Cl2 is 50-90 sccm, and the flow rate of BCl3 is 100-200 sccm; the auxiliary gas of the first ICP etching includes Ar, and the flow rate of Ar is 0-100 sccm; the pressure in the chamber of the first ICP etching is 30-40 mtorr; the RF power of the generator of the first ICP etching is 1200-1700 W, and the power of the bias power RF is 0 W; the time of the first ICP etching is 14-21 s; Performing ICP deposition to form a polymer layer at least covering the removal area; Performing a second ICP etching to remove the remaining ultra-thin metal layer inside the groove, while keeping the polymer layer in the removal area not completely etched, so as to protect the substrate outside the groove covered by the polymer layer from being etched; ICP cleaning was performed to remove the remaining polymer layer.

2. The ICP etching method of the ultra-thin metal layer according to claim 1, characterized in that: During the first ICP etching, the ICP deposition, the second ICP etching and the ICP cleaning, only source power RF is used, and bias power RF is not used.

3. The ICP etching method of the ultra-thin metal layer according to claim 1, characterized in that: The material of the layer in the substrate that contacts the ultra-thin metal layer includes SiO2; The substrate includes a wafer.

4. The ICP etching method of the ultra-thin metal layer according to claim 1, characterized in that: During the first ICP etching, the ICP deposition, the second ICP etching and the ICP cleaning, the operating temperature of the substrate is maintained at 100-170° C.

5. The ICP etching method of the ultra-thin metal layer according to claim 1, characterized in that: The deposition gas of the ICP deposition includes CH4, and the flow rate of the deposition gas is 15-30 sccm; The auxiliary gas for the ICP deposition includes Ar, and the flow rate of the auxiliary gas is 70-100 sccm; The source power radio frequency of the ICP deposition is 700-1000W, and the bias power radio frequency is 0W; The pressure in the ICP deposition chamber is 6-10 mtorr; The ICP deposition time is 5 to 10 seconds.

6. The ICP etching method of the ultra-thin metal layer according to claim 1, characterized in that: The thickness of the polymer layer outside the groove is 3-7 nm.

7. The ICP etching method of the ultra-thin metal layer according to claim 1, characterized in that: The etching gas of the second ICP etching includes Cl2 and / or BCl3; wherein the flow rate of Cl2 is 50-90 sccm, and the flow rate of BCl3 is 100-200 sccm; The auxiliary gas for the second ICP etching includes Ar, and the flow rate of Ar is 0-100 sccm; The pressure in the chamber of the second ICP etching is 30-40 mtorr; The power of the source power radio frequency of the second ICP etching is 1200-1700W, and the power of the bias power radio frequency is 0W; The second ICP etching time is 14-21 s.

8. The ICP etching method of the ultra-thin metal layer according to claim 1, characterized in that: The cleaning gas for the ICP cleaning includes O2, and the flow rate of the cleaning gas is 200-300 sccm; The auxiliary gas for ICP cleaning includes N2, and the flow rate of the auxiliary gas is 20-50 sccm; The source power RF power of the ICP cleaning is 800-1200W, and the bias power RF power is 0W; The pressure in the ICP cleaning chamber is 10-15 mtorr; The time of the ICP cleaning was monitored by OES to obtain the end point.

9. A wafer, characterized in that: The wafer is processed according to the ICP etching method for the ultra-thin metal layer according to any one of claims 1-8.

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