Back metal grid etching method

Abstract

The invention provides a back metal grid etching method, which comprises the following steps of: providing a preset substrate, and transferring the preset substrate into a reaction chamber of an inductively coupled plasma etching machine; wherein the preset substrate comprises an organic film layer, a medium hard mask layer and a metal grid layer which are sequentially arranged from top to bottom; a dielectric hard mask layer etching step: introducing a first etching gas into the reaction chamber, and etching the dielectric hard mask layer by taking the organic film layer as a mask until a next film layer is exposed; an organic film layer removal step: introducing oxygen-containing gas into the reaction chamber, and etching to remove the organic film layer; and a metal grid layer etching step: introducing second etching gas into the reaction chamber, and etching the metal grid layer by taking the medium hard mask layer as a mask until a next film layer is exposed. The back metal grid etching process is optimized, the process steps are simplified, the product yield can be effectively improved, and the operation cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a back metal grid etching method. Background Art

[0002] With the advancement of technology, an increasing number of electronic devices (digital cameras, optical devices, and automotive chips) are beginning to utilize image sensors. Image sensors utilize the photoelectric conversion function of optoelectronic devices to convert the light image on a photosensitive surface into an electrical signal proportional to the light image. Current image sensors include charge-coupled device (CCD) image sensors and complementary metal-oxide-semiconductor (CMOS) image sensors. Compared to traditional CCD image sensors, CMOS image sensors offer advantages such as compact size, high integration, low power consumption, and low cost. They are used in mobile phones, computers, video cameras, and security surveillance systems.

[0003] Current CMOS image sensor products can be categorized as FSI (Front Side Illumination) and BSI (Back Side Illumination). FSI, like the basic CMOS process, begins with the front-end-of-line (FEOL) process, followed by the back-end-of-line (BEOL) process, before finally fabricating the optical module (color filter and microlens) on the surface. A major issue with FSI is that light must pass through a thick metal wiring layer before entering the silicon substrate, resulting in significant photon loss and impacting the ultimate quantum efficiency (QE). BSI was invented to address this issue. After completing the BEOL process, BSI flips the sensor wafer over and bonds it to another wafer. Starting from the back, the sensor wafer is thinned down to the required thickness for the device, and then the optical module is fabricated on the surface. In the BSI process, light can be directly incident on the silicon substrate from the back without passing through the metal wiring layer, so the quality of small pixels can be greatly improved.

[0004] The back metal grid etching process is one of the most core processes in the manufacture of BSI image sensors. Its function is to perform optical isolation, that is, to block light from entering the adjacent photodiode (PD). It plays a very important role in its electrical characteristics and yield. The film structure before the back metal grid etching is as follows: Figure 1Related backside metal grid etching technology typically includes a two-step dry etching process and a one-step stripping process. In the etching process, the hard mask of the backside metal grid is first etched in a capacitively coupled plasma etcher, then stripped in a stripping machine, and finally etched in an inductively coupled plasma etcher. This etching process requires the use of different equipment, has numerous etching steps, carries the risk of reduced yield, and also increases operating costs. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a back metal grid etching method, which can optimize the back metal grid etching process, simplify the process steps, effectively improve product yield, and reduce operating costs.

[0006] In order to achieve the above objectives, the technical solutions adopted in the embodiments of the present invention are as follows:

[0007] In a first aspect, an embodiment of the present invention provides a backside metal grid etching method, comprising:

[0008] Providing a preset substrate, and introducing the preset substrate into a reaction chamber of an inductively coupled plasma etcher; wherein the preset substrate comprises an organic film layer, a dielectric hard mask layer, and a metal grid layer arranged sequentially from top to bottom;

[0009] a dielectric hard mask layer etching step, introducing a first etching gas into the reaction chamber and etching the dielectric hard mask layer using the organic film layer as a mask until the next film layer is exposed; wherein the first etching gas comprises a fluorine-containing gas;

[0010] an organic film layer removal step, introducing an oxygen-containing gas into the reaction chamber to etch and remove the organic film layer;

[0011] In the metal grid layer etching step, a second etching gas is introduced into the reaction chamber, and the metal grid layer is etched using the dielectric hard mask layer as a mask until the next film layer is exposed; wherein the second etching gas includes a chlorine-containing gas.

[0012] Furthermore, an embodiment of the present invention provides a first possible implementation of the first aspect, wherein the second etching gas further includes a carbon-containing gas and a nitrogen-containing gas.

[0013] Furthermore, an embodiment of the present invention provides a second possible implementation of the first aspect, wherein the carbon-containing gas includes CH4, and the nitrogen-containing gas includes N2;

[0014] The flow ratio of the CH4 to the N2 is less than 2:1.

[0015] Furthermore, an embodiment of the present invention provides a third possible implementation of the first aspect, wherein the chlorine-containing gas in the second etching gas includes BCl3 and Cl2;

[0016] The flow ratio of the BCl3 to the Cl2 is less than 1:4.

[0017] Furthermore, an embodiment of the present invention provides a fourth possible implementation of the first aspect, wherein the predetermined substrate further includes a patterned photoresist layer and an organic anti-reflection layer arranged in sequence from top to bottom above the organic film layer;

[0018] Before the dielectric hard mask layer etching step, the back metal grid etching method further includes:

[0019] In the organic anti-reflection layer etching step, fluorine-containing gas is introduced into the reaction chamber, and the organic anti-reflection layer is etched using the photoresist layer as a mask until the organic film layer is exposed.

[0020] Furthermore, the embodiment of the present invention provides a fifth possible implementation of the first aspect, wherein the method further includes:

[0021] In the organic film layer etching step, oxygen-containing gas is introduced into the reaction chamber, and the organic film layer is etched using the photoresist layer as a mask until the dielectric hard mask layer is exposed.

[0022] Furthermore, an embodiment of the present invention provides a sixth possible implementation of the first aspect, wherein the predetermined substrate further includes an upper bonding metal barrier layer, and the upper bonding metal barrier layer is located between the dielectric hard mask layer and the metal grid layer;

[0023] Before the metal grid layer etching step, the back metal grid etching method further includes:

[0024] In the upper bonding metal barrier layer etching step, chlorine-containing gas is introduced into the reaction chamber, and the upper bonding metal barrier layer is etched using the dielectric hard mask layer as a mask until the metal grid layer is exposed.

[0025] Furthermore, an embodiment of the present invention provides a seventh possible implementation of the first aspect, wherein the predetermined substrate further includes a lower bonding metal barrier layer and an etch stop layer sequentially arranged below the metal grid layer;

[0026] After the metal grid layer etching step, the back metal grid etching method further includes:

[0027] In the lower bonding metal barrier layer etching step, chlorine-containing gas is introduced into the reaction chamber, and the lower bonding metal barrier layer is etched using the dielectric hard mask layer as a mask until the etch stop layer is exposed.

[0028] Furthermore, an embodiment of the present invention provides an eighth possible implementation of the first aspect, wherein, after the lower bonding metal barrier layer etching step, the back metal grid etching method further includes:

[0029] An oxygen-containing gas is introduced into the reaction chamber to etch and remove the residual polymer in the reaction chamber.

[0030] Furthermore, an embodiment of the present invention provides a ninth possible implementation of the first aspect, wherein, in each etching step, the chamber pressure of the reaction chamber is controlled to be less than 10 mT.

[0031] An embodiment of the present invention provides a back metal grid etching method, which includes: providing a preset substrate, and introducing the preset substrate into a reaction chamber of an inductively coupled plasma etcher; wherein the preset substrate includes an organic film layer, a dielectric hard mask layer, and a metal grid layer arranged in sequence from top to bottom; a dielectric hard mask layer etching step, wherein a first etching gas is introduced into the reaction chamber, and the dielectric hard mask layer is etched using the organic film layer as a mask until the next film layer is exposed; wherein the first etching gas includes a fluorine-containing gas; an organic film layer removal step, wherein an oxygen-containing gas is introduced into the reaction chamber, and the organic film layer is etched and removed; a metal grid layer etching step, wherein a second etching gas is introduced into the reaction chamber, and the metal grid layer is etched using the dielectric hard mask layer as a mask until the next film layer is exposed; wherein the second etching gas includes a chlorine-containing gas. The present invention transfers a preset substrate into the reaction chamber of an inductively coupled plasma etcher during back metal grid etching, thereby completing the etching of a dielectric hard mask layer and a metal grid layer as well as etching and removing of an organic film layer in the inductively coupled plasma etcher. There is no need to transfer the wafer between the etcher and the degumming machine, thereby optimizing the back metal grid etching process, simplifying the process steps, effectively improving product yield, and reducing operating costs.

[0032] Other features and advantages of the embodiments of the present invention will be described in the following description, or some features and advantages can be inferred or determined without doubt from the description, or can be learned by implementing the above-mentioned technologies of the embodiments of the present invention.

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 A flow chart of a back metal grid etching method provided by an embodiment of the present invention is shown;

[0036] Figure 2a A schematic diagram of a preset base membrane layer structure provided by an embodiment of the present invention is shown;

[0037] Figure 2b to Figure 2h A back metal grid etching flow chart provided by an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0039] At present, the related back metal grid etching method usually adopts a two-step dry etching and a one-step degumming process for the film layer structure on the back side of the substrate. The hard mask of the back metal grid is first etched in a capacitively coupled plasma etcher, and then the degumming is performed on a degumming machine. Finally, the back metal grid is etched in an inductively coupled plasma etcher. However, when etching the hard mask of the back metal grid in a capacitively coupled plasma etcher, there are problems such as lower plasma density and the inability to independently control the plasma density and energy, which can easily lead to deviations in the transfer accuracy; and it is necessary to transfer the wafer between chambers many times, and the process flow is complicated, which is prone to the risk of reduced yield and will increase the cost. In order to improve the above problems, an embodiment of the present invention provides a back metal grid etching method, and the embodiment of the present invention is described in detail below.

[0040] This embodiment provides a backside metal grid etching method, which is applied to semiconductor process equipment. Figure 1 The back metal grid etching method shown in the flowchart mainly includes the following steps:

[0041] Step S102, providing a predetermined substrate, and introducing the predetermined substrate into a reaction chamber of an inductively coupled plasma etcher;

[0042] See for example Figure 2aThe schematic diagram of the preset substrate film layer structure shown in FIG. 1 includes a patterned photoresist layer 201, an organic anti-reflective layer 202, an organic film layer 203, a dielectric hard mask layer 204, an upper bonding metal barrier layer 205, a metal grid layer 206, a lower bonding metal barrier layer 207, and an etch stop layer 208, which are arranged in sequence from top to bottom.

[0043] The above-mentioned preset substrate is introduced into the reaction chamber of an inductively coupled plasma (ICP) etcher, and the frequency of the upper and lower power supplies can be controlled to 13.56MHz. Due to the low plasma density of the capacitively coupled plasma etcher, incomplete debonding may occur. By introducing the preset substrate into the reaction chamber of the inductively coupled plasma etcher, the hard mask layer and the metal grid layer can be etched, and the debonding process can also be performed. The high plasma density of the inductively coupled plasma etcher can completely remove the photoresist layer, avoiding incomplete debonding. This allows the etching and debonding of the wafer to be completed in the same chamber, simplifying the process steps.

[0044] Step S104, a dielectric hard mask layer etching step, introducing a first etching gas into the reaction chamber, and etching the dielectric hard mask layer using the organic film layer as a mask until the next film layer is exposed;

[0045] The above-mentioned first etching gas includes a fluorine-containing gas, which may include CF4 and / or CHF3; the purpose of the dielectric hard mask layer is to serve as a mask layer for etching the metal grid. During the etching process, the reaction chamber pressure can be controlled to be 3-10mT, the upper electrode power can be controlled to be 400-700W, the lower electrode power can be controlled to be 80-160W, and the power application mode of the upper electrode and the lower electrode is continuous wave (CW); the upper electrode power current density distribution can be set to 0.4-0.6, and the process time is related to the thickness of the dielectric hard mask layer, such as 50-80s.

[0046] In one embodiment, 80-120 sccm CF4 and 20-40 sccm CHF3 can be introduced into the reaction chamber as the main etching gas, and 80-120 sccm He can be introduced as the dilution gas. The etching reaction is:

[0047] SiO2+4F→SiF4↑+O2↑

[0048] SiO2+2CF2→SiF4↑+2CO↑

[0049] Step S106, an organic film layer removal step, introducing an oxygen-containing gas into the reaction chamber to etch and remove the organic film layer;

[0050] The organic film layer is located on the upper layer of the dielectric hard mask layer. After the dielectric hard mask layer is etched using the organic film layer as a mask, the organic film layer is etched away. The main components of the organic film layer include carbon and oxygen. During the etching process, oxygen-containing gas is introduced into the reaction chamber, which can react with the carbon in the organic film layer to produce carbon monoxide and carbon dioxide.

[0051] In one embodiment, during the process of etching and removing the organic film layer, the chamber pressure is controlled to be 3-10 mT, the upper electrode power is controlled to be 500-800 W, and the lower electrode power is controlled to be 50-100 W. The power application mode of the upper and lower electrodes is continuous wave (CW). The upper electrode power current density distribution can be set to 0.4-0.6. The etching time is related to the thickness of the organic film layer and can be, for example, 30-50 seconds. In a specific embodiment, 100-300 sccm of O2 can be introduced into the reaction chamber as the main etching gas.

[0052] Step S108, a metal grid layer etching step, introducing a second etching gas into the reaction chamber, and etching the metal grid layer using the dielectric hard mask layer as a mask until the next film layer is exposed;

[0053] The second etching gas includes a chlorine-containing gas. The material of the metal grid layer is usually aluminum. By introducing the chlorine-containing gas into the reaction chamber, the chlorine-containing gas can react with the aluminum to etch the metal grid layer.

[0054] The metal grid layer is a key film layer for optimizing optical and electrical properties, used to enhance light guidance, reduce crosstalk, and improve electrical signal collection efficiency. During the etching process, the chamber pressure can be controlled at 8-10mT; the upper electrode power is controlled at 500-1000W, and the lower electrode power is controlled at 200-400W. The power application method for the upper and lower electrodes is continuous wave (CW), and the upper electrode power current density distribution can be set to 0.4-0.6. The etching time is related to the thickness of the metal grid layer and can be, for example, 20-30s.

[0055] The above-mentioned back metal grid etching method provided in this embodiment, by transferring a preset substrate into the reaction chamber of an inductively coupled plasma etcher during back metal grid etching, can complete the etching of the dielectric hard mask layer and the metal grid layer and the etching and removal of the organic film layer in the inductively coupled plasma etcher, without the need to transfer the wafer between the etcher and the debonding machine, thereby optimizing the back metal grid etching process, simplifying the process steps, effectively improving product yield, and reducing operating costs.

[0056] In one embodiment, the chlorine-containing gas in the second etching gas includes BCl3 and Cl2; the flow ratio of BCl3 to Cl2 is less than 1:4, and 40-50 sccm BCl3 and 200-300 sccm Cl2 can be introduced into the reaction chamber as the main etching gas. BCl3 and Cl2 are used as the main etching gas, and the generated plasma can react with Al, the main component of the electrode, to ultimately generate volatile AlCl3. The etching reaction is:

[0057] 2Al+6Cl2→2AlCl3↑

[0058] The flow ratio of BCl3 and Cl2 is a key parameter for improving the etching morphology of the metal grid layer. By controlling the flow ratio of BCl3 and Cl2 to be less than 1:4 during the etching process, it can be ensured that the etching gas contains a certain amount of B to bombard the side wall, thereby improving the side wall morphology.

[0059] In one implementation, the second etching gas provided in this embodiment further includes a carbon-containing gas and a nitrogen-containing gas.

[0060] During the etching process of the metal grid layer, by introducing carbon-containing gas into the chamber, carbon-based polymers can be generated and attached to the side walls of the dielectric hard mask layer, thereby protecting the side walls of the dielectric hard mask layer and preventing the lateral depression of the dielectric hard mask layer. However, the amount of carbon-containing gas is not necessarily better. Excessive accumulation of carbon-based polymers will not only cause the metal grid layer to be non-vertical after etching, but also increase the critical dimension load of the dense-sparse area, which is prone to cause defects. Since the amount of carbon-containing gas cannot be further increased, the metal grid layer is still prone to side wall depression after etching. Therefore, nitrogen-containing gas can also be added as an etching protection gas, thereby solving the problem of Al side wall depression of the metal grid layer.

[0061] In one embodiment, the carbon-containing gas provided in this embodiment includes CH 4 , and the nitrogen-containing gas includes N 2 ; the flow ratio of CH 4 to N 2 is less than 2:1.

[0062] During the etching process, 10-20 sccm of CH4 can be introduced into the reaction chamber as an etching shield gas. Under the action of the plasma, CH4 generates carbon-based polymers that adhere to the sidewalls of the dielectric hard mask layer. The amount of CH4 is not necessarily better. The more CH4, the more carbon-based polymers are produced. Excessive carbon-based polymer accumulation not only causes the Al film layer to be non-vertical after etching, but also increases the critical dimension load of the dense-sparse area, which is prone to defect problems. Since the amount of CH4 introduced cannot be further increased, the Al after etching still has the problem of sidewall concavity. 8-15 sccm of N2 can be introduced as an etching shield gas to form AlN chemical passivation, providing more stable protection and solving the Al sidewall concavity problem.

[0063] In one embodiment, the predetermined substrate further includes a patterned photoresist layer and an organic anti-reflection layer arranged sequentially from top to bottom above the organic film layer; before the dielectric hard mask layer etching step, the back metal grid etching method provided in this embodiment further includes:

[0064] In the organic anti-reflection layer etching step, fluorine-containing gas is introduced into the reaction chamber, and the organic anti-reflection layer is etched using the photoresist layer as a mask until the organic film layer is exposed.

[0065] The main components of the organic anti-reflection layer are C, N, and Si (14% to 40%). The main purpose is to reduce the anti-reflection function and increase the etching selectivity. In the process of etching the organic anti-reflection layer using the photoresist layer as a mask, the chamber pressure can be controlled to 10-15mT, the upper electrode power can be controlled to 500-700W, and the lower electrode power can be controlled to 50-100W. The power application mode of the upper and lower electrodes is continuous wave (CW). The upper electrode power current density distribution can be set to 0.4-0.6. The etching process time is related to the thickness of the organic anti-reflection layer, such as 30-50s. The reaction of introducing fluorine-containing gas into the reaction chamber to etch the organic anti-reflection layer is:

[0066] Si+4F→SiF4↑

[0067] In a specific embodiment, the fluorine-containing gas may include CF4 and CHF3. When etching the organic anti-reflective layer, 50-100 sccm of CF4 and 50-100 sccm of CHF3 may be introduced as the main etching gases. Adjusting the CF4 / CHF3 flow ratio is an important method for improving critical dimensions. The CF4 / CHF3 flow ratio may be greater than 1:2. 60-100 sccm of N2 gas may also be introduced as a dilution gas to remove byproducts generated during the etching process.

[0068] In one embodiment, the method provided in this embodiment further includes:

[0069] In the organic film layer etching step, oxygen-containing gas is introduced into the reaction chamber, and the organic film layer is etched using the photoresist layer as a mask until the dielectric hard mask layer is exposed.

[0070] The main components of the organic film layer are C and O. The sandwich structure composed of the photoresist layer, organic anti-reflection layer and organic film layer can solve the problem of inability to complete the accurate transmission of graphics when the photoresist thickness is insufficient, and can also reduce light scattering and standing wave effects. During the etching process, the chamber pressure can be controlled to 3-10mT, the upper electrode power can be controlled to 300-600W, and the lower electrode power can be controlled to 100-300W. The power application mode of the upper and lower electrodes is continuous wave (CW); the upper electrode power current density distribution can be set to 0.4-0.6. The etching process time is related to the thickness of the organic film layer, such as 50-80s. The etching reaction of oxygen-containing gas as the main etching gas is:

[0071] C+O2→CO2↑

[0072] 2C+O2→2CO↑

[0073] In a specific embodiment, 90-150 sccm of oxidizing gas O2 can be introduced into the reaction chamber as the main etching gas; 30-80 sccm of N2, HBr and Cl2 can be introduced into the reaction chamber as the passivation gas to adjust the angle of the organic film layer.

[0074] In one embodiment, the preset substrate further includes an upper bonding metal barrier layer, which is located between the dielectric hard mask layer and the metal grid layer. Before the metal grid layer etching step, the back metal grid etching method provided in this embodiment further includes:

[0075] In the upper bonding metal barrier layer etching step, chlorine-containing gas is introduced into the reaction chamber, and the upper bonding metal barrier layer is etched using the dielectric hard mask layer as a mask until the metal grid layer is exposed.

[0076] The purpose of the upper bonding metal barrier layer is to prevent aluminum diffusion and improve electromigration. During the etching process, the chamber pressure is controlled at 8-10mT, the upper electrode power is controlled at 500-1000W, and the lower electrode power is controlled at 200-400W. The power application mode of the upper and lower electrodes is continuous wave (CW), and the upper electrode power current density distribution can be set to 0.4-0.6; the process time is related to the film thickness of the upper bonding metal barrier layer, such as 5-10s. Chlorine-containing gas is used as the main etching gas, and the etching reaction is:

[0077] Ti3N4+6Cl2→3TiCl4↑+2N2↑

[0078] In one specific embodiment, the chlorine-containing gas introduced into the chamber may include BCl3 and Cl2, with the BCl3 to Cl2 flow ratio being less than 1:2. 40-60 sccm of BCl3 and 80-130 sccm of Cl2 may be introduced into the chamber as the main etching gas, while 50-100 sccm of Ar may be introduced as the auxiliary bombardment gas and dilution gas. By controlling the BCl3 to Cl2 flow ratio to less than 1:2, a smaller proportion of BCl3 may be introduced, thereby partially etching the metal grid layer and completely etching the upper bonding metal barrier layer, while simultaneously preventing the impact of the larger bombardment effect of B on the morphology transfer of the metal grid layer.

[0079] In one embodiment, the preset substrate further includes a lower bonding metal barrier layer and an etch stop layer sequentially arranged below the metal grid layer; after the metal grid layer etching step, the back metal grid etching method provided in this embodiment further includes:

[0080] In the lower bonding metal barrier layer etching step, chlorine-containing gas is introduced into the reaction chamber, and the lower bonding metal barrier layer is etched using the dielectric hard mask layer as a mask until the etch stop layer is reached.

[0081] The purpose of the lower bonding metal barrier layer is to block aluminum diffusion and improve electromigration. During the etching process, the chamber pressure is controlled at 5-7 mT, the upper electrode power is controlled at 500-700W, and the lower electrode power is controlled at 300-400W. The power application mode for the upper and lower electrodes is continuous wave (CW). The upper electrode power current density distribution can be set to 0.4-0.6. The process time is related to the film thickness of the lower bonding metal barrier layer and can be 20-30 seconds, for example.

[0082] In one specific embodiment, the chlorine-containing gas introduced into the chamber may include BCl3 and Cl2, with a BCl3 to Cl2 flow ratio greater than 4:1. 200-300 sccm BCl3 and 50-80 sccm Cl2 may be introduced into the chamber as the main etching gas, while 5-10 sccm CH4 and 5-8 sccm N2 may be introduced as etching shield gases. By controlling the BCl3 to Cl2 flow ratio to be greater than 4:1 and introducing a higher proportion of B, a greater bombardment effect can be achieved, partially etching the etch stop layer below the lower bonding metal barrier layer, ensuring accurate transfer of the etched topography of the lower bonding metal barrier layer.

[0083] In one embodiment, after the lower bonding metal barrier layer etching step, the back metal grid etching method provided in this embodiment further includes:

[0084] An oxygen-containing gas is introduced into the reaction chamber to etch and remove the residual polymer in the reaction chamber.

[0085] Since a large amount of passivation gas is used in the process of etching the metal grid layer Al, polymers are easily generated during the etching process. After etching, there are still polymer residues in some areas. If the polymers are not removed, the device performance will be affected, thereby affecting the product yield. The residual polymers are removed. During the etching process, the chamber pressure is controlled to 8-15mT, the upper electrode power is controlled to 1000-1500W, and the lower electrode power is controlled to 10-30W. The upper electrode power current density distribution can be set to 0.4-0.6; the etching and removal time of the polymer can be 30-50s. In a specific embodiment, 100-300sccm O2 and 30-80sccm N2 can be introduced as dilution gases. The dilution gas can also take away the by-products produced during the etching process.

[0086] In one embodiment, in each etching step provided in this embodiment, the chamber pressure of the reaction chamber is controlled to be less than 10 mT.

[0087] By controlling the chamber pressure of the reaction chamber to be less than 10mT in each etching step during the back metal grid etching process, the chamber is placed in a low-pressure environment, which can improve the etching uniformity, reduce the transfer deviation of the etching morphology, and enhance the transfer accuracy of the etching morphology.

[0088] The above-mentioned back metal grid etching method provided in this embodiment adopts a one-step etching method for the back metal grid (BMG), which can effectively improve product yield and reduce operating costs. During the aluminum etching process, by adopting a suitable CH4 and N2 gas ratio, not only can the side wall concave problem be solved, but also wafer defects can be reduced, thereby improving product yield.

[0089] Based on the above embodiment, this embodiment provides an example of applying the above back metal grid etching method to simplify the CMOS image sensor CIS back metal grid etching process and optimize the morphology, such as Figure 2a As shown, the preset substrate includes a patterned photoresist layer 201, an organic anti-reflection layer 202, an organic film layer 203, a dielectric hard mask layer 204, an upper bonding metal barrier layer 205, a metal grid layer 206, a lower bonding metal barrier layer 207 and an etch stop layer 208 arranged in sequence from top to bottom; see FIG. Figure 2b to Figure 2h The back metal grid etching process shown in the figure can be performed by referring to the following steps:

[0090] In step 1, an organic anti-reflection layer etching step, a fluorine-containing gas is introduced into the reaction chamber, and the organic anti-reflection layer 202 is etched using the patterned photoresist layer 201 as a mask until the organic film layer 203 is exposed.

[0091] The chamber pressure is controlled at 10-15 mT, the upper electrode power is controlled at 500-700 W, and the lower electrode power is controlled at 50-100 W. The power application mode for the upper and lower electrodes is continuous wave (CW). The upper electrode power current density distribution can be set to 0.4-0.6, and the etching process time is 30-50 seconds. When etching the organic anti-reflective layer 202, part of the photoresist layer 201 will be digested.

[0092] 50-100 sccm CF4 and 50-100 sccm CHF3 are introduced as the main etching gases. Adjusting the CF4 / CHF3 flow ratio is an important way to improve critical dimensions. The CF4 / CHF3 flow ratio can be greater than 1:2. 60-100 sccm N2 gas is introduced as a dilution gas to remove byproducts produced during the etching process.

[0093] In step 2, an organic film layer etching step, oxygen-containing gas is introduced into the reaction chamber, and the organic film layer 203 is etched using the photoresist layer 201 as a mask until the dielectric hard mask layer 204 is exposed.

[0094] When etching the organic film layer 203, the photoresist layer 201 is also removed. The sandwich structure composed of the photoresist layer, organic anti-reflection layer, and organic film layer can solve the problem of inability to accurately transfer the pattern when the photoresist thickness is insufficient, and can also reduce light scattering and standing wave effects. During the etching process, the chamber pressure can be controlled to 3-10mT, the upper electrode power can be controlled to 300-600W, and the lower electrode power can be controlled to 100-300W. The power application mode of the upper and lower electrodes is continuous wave (CW); the upper electrode power current density distribution can be set to 0.4-0.6, and the etching process time is 50-80s.

[0095] 90-150 sccm of oxidizing gas O2 is introduced into the reaction chamber as the main etching gas; 30-80 sccm of N2, HBr and Cl2 are introduced as passivation gases to adjust the angle of the organic film layer.

[0096] In step 3, the dielectric hard mask layer etching step, a first etching gas is introduced into the reaction chamber, and the dielectric hard mask layer 204 is etched using the organic film layer 203 as a mask until the upper bonding metal barrier layer 205 is exposed.

[0097] The dielectric hard mask layer (SION) serves as a mask for etching the metal grid. During the etching process, the reaction chamber pressure is controlled at 3-10mT, the upper electrode power is controlled at 400-700W, and the lower electrode power is controlled at 80-160W. The power application mode for the upper and lower electrodes is continuous wave (CW). The upper electrode power current density distribution can be set to 0.4-0.6, and the process time is 50-80s.

[0098] 80-120 sccm CF4 and 20-40 sccm CHF3 are introduced into the reaction chamber as main etching gases, and 80-120 sccm He is introduced as a dilution gas.

[0099] In step 4, the organic film layer removal step, oxygen-containing gas is introduced into the reaction chamber to etch and remove the organic film layer 203 .

[0100] During the etching process, the chamber pressure is controlled at 3-10 mT, the upper electrode power is controlled at 500-800 W, and the lower electrode power is controlled at 50-100 W. The power application mode of the upper and lower electrodes is continuous wave (CW). The upper electrode power current density distribution can be set to 0.4-0.6, and the etching time is 30-50 seconds. 100-300 sccm of O2 is introduced into the reaction chamber as the main etching gas.

[0101] In step 5, etching the upper bonding metal barrier layer, chlorine-containing gas is introduced into the reaction chamber, and the upper bonding metal barrier layer 205 is etched using the dielectric hard mask layer 204 as a mask until the metal grid layer 206 is exposed.

[0102] During the etching process, the chamber pressure is controlled to 8-10mT, the upper electrode power is controlled to 500-1000W, the lower electrode power is controlled to 200-400W, the power application mode of the upper and lower electrodes is continuous wave (CW), and the upper electrode power current density distribution can be set to 0.4-0.6; the process time can be 5-10s.

[0103] 40-60 sccm BCl3 and 80-130 sccm Cl2 are introduced into the chamber as main etching gases; 50-100 sccm Ar is introduced as auxiliary bombardment gas and dilution gas.

[0104] In step 6, a metal grid layer etching step, chlorine-containing gas is introduced into the reaction chamber, and the metal grid layer 206 is etched using the dielectric hard mask layer 204 as a mask until the lower bonding metal barrier layer 207 is exposed.

[0105] During the etching process, the chamber pressure is controlled at 8-10mT; the upper electrode power is controlled at 500-1000W, the lower electrode power is controlled at 200-400W, the power application mode of the upper and lower electrodes is continuous wave (CW), the upper electrode power current density distribution can be set to 0.4-0.6, and the etching time is 20-30s.

[0106] 40-50 sccm BCl3 and 200-300 sccm Cl2 are introduced into the reaction chamber as the main etching gas; 10-20 sccm CH4 is introduced as the etching protection gas, and 8-15 sccm N2 is introduced as the etching protection gas. The flow ratio of CH4 to N2 is less than 2:1.

[0107] In step 7, etching the lower bonding metal barrier layer, a chlorine-containing gas is introduced into the reaction chamber to etch the lower bonding metal barrier layer 206 using the dielectric hard mask layer 204 as a mask until the etch stop layer 208 is reached.

[0108] During the etching process, the chamber pressure is controlled at 5-7mT, the upper electrode power is controlled at 500-700W, the lower electrode power is controlled at 300-400W, and the power application mode of the upper and lower electrodes is continuous wave (CW); the upper electrode power current density distribution can be set to 0.4-0.6; the process time is 20-30s.

[0109] 200-300 sccm BCl3 and 50-80 sccm Cl2 are introduced into the chamber as main etching gases; 5-10 sccm CH4 and 5-8 sccm N2 are introduced as etching protection gases.

[0110] In step 8, a polymer removal step, oxygen-containing gas is introduced into the reaction chamber to etch away the residual polymer in the reaction chamber.

[0111] During the etching process, the chamber pressure is controlled at 8-15 mT, the upper electrode power is controlled at 1000-1500 W, the lower electrode power is controlled at 10-30 W, and the upper electrode power current density distribution can be set to 0.4-0.6. The polymer etching removal time can be 30-50 seconds. 100-300 sccm O2 and 30-80 sccm N2 are introduced as dilution gases, which also remove byproducts produced during the etching process.

[0112] An embodiment of the present invention provides an electronic device, which includes a processor and a memory. The memory stores a computer program that can be run on the processor. When the processor executes the computer program, the steps of the method provided in the above embodiment are implemented.

[0113] An embodiment of the present invention provides a computer-readable medium, wherein the computer-readable medium stores computer-executable instructions. When the computer-executable instructions are called and executed by a processor, the computer-executable instructions prompt the processor to implement the method described in the above embodiment.

[0114] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working process of the system described above can refer to the corresponding process in the aforementioned embodiment and will not be repeated here.

[0115] In addition, in the description of the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0116] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0117] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A back metal grid etching method, characterized in that: include: Providing a preset substrate, and introducing the preset substrate into a reaction chamber of an inductively coupled plasma etcher; wherein the preset substrate comprises an organic film layer, a dielectric hard mask layer, and a metal grid layer arranged sequentially from top to bottom; a dielectric hard mask layer etching step, introducing a first etching gas into the reaction chamber and etching the dielectric hard mask layer using the organic film layer as a mask until the next film layer is exposed; wherein the first etching gas comprises a fluorine-containing gas; an organic film layer removal step, introducing an oxygen-containing gas into the reaction chamber to etch and remove the organic film layer; In the metal grid layer etching step, a second etching gas is introduced into the reaction chamber, and the metal grid layer is etched using the dielectric hard mask layer as a mask until the next film layer is exposed; wherein the second etching gas includes a chlorine-containing gas.

2. The method according to claim 1, characterized in that The second etching gas further includes a carbon-containing gas and a nitrogen-containing gas.

3. The method according to claim 2, characterized in that The carbon-containing gas includes CH4, and the nitrogen-containing gas includes N2; The flow ratio of the CH4 to the N2 is less than 2:

1.

4. The method according to claim 1, wherein The chlorine-containing gas in the second etching gas includes BCl3 and Cl2; The flow ratio of the BCl3 to the Cl2 is less than 1:

4.

5. The method according to claim 1, wherein The preset substrate further includes a patterned photoresist layer and an organic anti-reflection layer arranged in sequence from top to bottom above the organic film layer; Before the dielectric hard mask layer etching step, the back metal grid etching method further includes: In the organic anti-reflection layer etching step, fluorine-containing gas is introduced into the reaction chamber, and the organic anti-reflection layer is etched using the photoresist layer as a mask until the organic film layer is exposed.

6. The method according to claim 5, characterized in that Also includes: In the organic film layer etching step, oxygen-containing gas is introduced into the reaction chamber, and the organic film layer is etched using the photoresist layer as a mask until the dielectric hard mask layer is exposed.

7. The method according to claim 1, characterized in that The preset substrate further includes an upper bonding metal barrier layer, wherein the upper bonding metal barrier layer is located between the dielectric hard mask layer and the metal grid layer; Before the metal grid layer etching step, the back metal grid etching method further includes: In the upper bonding metal barrier layer etching step, chlorine-containing gas is introduced into the reaction chamber, and the upper bonding metal barrier layer is etched using the dielectric hard mask layer as a mask until the metal grid layer is exposed.

8. The method according to claim 1, characterized in that The preset substrate further includes a lower bonding metal barrier layer and an etch stop layer arranged in sequence below the metal grid layer; After the metal grid layer etching step, the back metal grid etching method further includes: In the lower bonding metal barrier layer etching step, chlorine-containing gas is introduced into the reaction chamber, and the lower bonding metal barrier layer is etched using the dielectric hard mask layer as a mask until the etch stop layer is exposed.

9. The method according to claim 8, characterized in that After the lower bonding metal barrier layer etching step, the back metal grid etching method further includes: An oxygen-containing gas is introduced into the reaction chamber to etch and remove the residual polymer in the reaction chamber.

10. The method according to any one of claims 1 to 9, characterized in that In each etching step, the chamber pressure of the reaction chamber is controlled to be less than 10 mT.

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