Gas, gas combination, etching method and device for plasma etching

Abstract

The present invention belongs to the field of plasma etching. Provided are a gas, a gas combination, an etching method, and a semiconductor device for plasma etching. One or more of a carbonyl halide, an aldehyde halide and a carboxyl halide provided as a process gas during an etching process is mainly used for excitation to form plasma, such that a layer to be etched is etched, thereby solving the problem of the top and the bottom being inconsistent caused by a relatively large difference between the bottom etching rate and the middle etching rate when etching is carried out to a certain degree during which holes or grooves having a high aspect ratio are formed, significantly improving the morphology of etching with a high aspect ratio, ensuring collimation, and improving the effectiveness of a semiconductor structure.

Description

Gas, gas combination, etching method and equipment for plasma etching Technical Field

[0001] The present invention relates to the field of plasma etching technology, and in particular to the field of plasma etching gas, gas combination, etching method and semiconductor equipment technology for etching objects with high aspect ratios. Background Art

[0002] Micromachining of semiconductor substrates is a well-known technology used to manufacture semiconductors, flat-panel displays, light-emitting diodes (LEDs), solar cells, and more. A key step in micromachining is the plasma treatment process, which takes place within a reaction chamber into which a process gas is introduced. An RF source is inductively and / or capacitively coupled to the chamber to excite the process gas, forming and maintaining a plasma.

[0003] As Moore's Law continues to catch up, different process technologies and semiconductor structures have been invented. Whether it is logic chips or memory chips, more and more high-aspect-ratio structures require plasma etching.

[0004] When the etching target is to form a high aspect ratio structure, it becomes increasingly difficult to continuously etch the bottom of the structure. Even if the etching reaches the predetermined depth, it is easy to produce morphological deviations. When the upper and lower dimensions of the high aspect ratio structure are not consistent, or defects such as bumps, bends, etc. occur in local areas, it will further affect the conductive performance of subsequent devices, and in severe cases, it will cause the device to fail. Disclosure of the invention

[0005] In order to solve the above technical problems, the present invention provides a plasma etching method, comprising the following steps:

[0006] Providing a substrate having a layer to be etched and a mask layer above the layer to be etched;

[0007] After the first type of gas and the second type of gas are introduced, they are excited to form plasma to etch the layer to be etched, thereby forming holes or grooves;

[0008] The first type of gas comprises one or more of fluorocarbons and hydrofluorocarbons;

[0009] The second type of gas includes one or more of carbonyl halides, aldehyde halides, and carboxyl halides.

[0010] Optionally, the carbonyl halide includes a functional group (CO)- and a combination of one or two of the functional groups F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-.

[0011] Optionally, the aldehyde halide includes a combination of a functional group (COH)- and one of the functional groups F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-.

[0012] Optionally, the carboxyl halide includes a combination of a functional group (COOH)- and one of the functional groups F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-.

[0013] Optionally, the second type of gas comprises COF2.

[0014] Optionally, the first type of gas includes one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5.

[0015] Optionally, the volume ratio of the first type of gas to the total gas is 30%-70%; the volume ratio of the second type of gas to the total gas is 1%-30%.

[0016] Optionally, the flow rate range of the first type of gas is: 10 sccm-300 sccm; the flow rate range of the second type of gas is: 5 sccm-200 sccm.

[0017] Optionally, when the first type of gas and the second type of gas are introduced, an auxiliary gas is also introduced, and the auxiliary gas includes one or more of O2, H2, NF3, HBr, WF6, and Ar.

[0018] Optionally, the volume ratio of the auxiliary gas to the total gas is 10%-30%.

[0019] Optionally, the flow rate range of the auxiliary gas is: 1 sccm-200 sccm.

[0020] Optionally, the layer to be etched includes SiO2, Si3N4, polysilicon, or an alternating stack of any two thereof.

[0021] Optionally, the aspect ratio of the hole or groove is greater than 40.

[0022] Optionally, when exciting the plasma, the frequency range of the radio frequency is: 13 MHz-200 MHz; the power range is: 1000W-30000W.

[0023] Optionally, when etching the layer to be etched, the temperature range of the substrate is: -50°C~100°C.

[0024] Optionally, when etching the layer to be etched, the gas pressure range is: 15mT-40mT.

[0025] Furthermore, the present invention also provides a gas combination for plasma etching, comprising:

[0026] Category 1 gases include one or more of fluorocarbons and hydrofluorocarbons;

[0027] The second type of gas comprises one or more of carbonyl halides, aldehyde halides, and carboxyl halides;

[0028] The auxiliary gas includes one or more of O2, H2, NF3, HBr, WF6, and Ar.

[0029] Optionally, the carbonyl halide comprises a functional group (CO)- and a functional group F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I- in combination with one or two thereof; the aldehyde halide comprises a functional group (COH)- and a functional group F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I- in combination with one thereof; the carboxyl halide comprises a functional group (COOH)- and a functional group F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, A combination of one of CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-.

[0030] Optionally, the first type of gas includes one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5.

[0031] Furthermore, the present invention also provides a plasma etching method, comprising the following steps:

[0032] Providing an etching object having a hole or groove structure thereon;

[0033] A process gas containing COF2 is provided and excited into plasma, and the holes or grooves are further etched by applying biased radio frequency.

[0034] Optionally, when the COF2 is excited into plasma, COF2 can decompose into COF+ groups and F-. The COF+ groups reach the bottom of the hole or groove under the action of the biased radio frequency and chemically react with the etching object at the bottom of the hole or groove to generate volatile products.

[0035] Optionally, the lateral etching amount of the COF+ group at the bottom of the hole or groove is greater than the lateral etching amount at the middle of the hole or groove.

[0036] Optionally, the etching object includes SiO2, Si3N4, polysilicon or an alternating stack of any two thereof.

[0037] Optionally, the frequency range of the bias radio frequency is: 150kHz-4MHz; the power range is: 500W-10kW.

[0038] Optionally, the following steps are also included:

[0039] Providing a substrate having a layer to be etched and a mask layer above the layer to be etched, wherein the layer to be etched is composed of SiO2, Si3N4 or an alternating stack of the two;

[0040] A process gas containing one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5 is provided and excited into plasma to form the holes or grooves on the substrate.

[0041] Optionally, the temperature range of the etching object is: -30°C~60°C.

[0042] Optionally, the aspect ratio of the hole or groove is greater than 20.

[0043] Furthermore, the present invention also provides a gas for plasma etching, which includes COF2. The COF2 can be decomposed into COF+ groups and F- in a plasma state. The COF+ groups can etch the dielectric material or semiconductor material at the bottom of the hole or groove under the action of biased radio frequency.

[0044] Optionally, the frequency range of the bias radio frequency is: 150kHz-400kHz; the power range is: 500W-10kW.

[0045] Optionally, the aspect ratio of the hole or groove is greater than 20.

[0046] Optionally, the dielectric material includes SiO2 or Si3N4; and the semiconductor material includes polysilicon.

[0047] Furthermore, the present invention also provides a semiconductor device, comprising:

[0048] A reaction chamber, wherein a reaction space is formed inside the reaction chamber for performing a plasma etching process;

[0049] An air inlet structure, used for introducing process gas into the reaction space;

[0050] A base, used for supporting the substrate;

[0051] a first gas source connected to the gas inlet structure, wherein the first gas source comprises one or more of fluorocarbons and hydrofluorocarbons;

[0052] a second gas source connected to the gas inlet structure, wherein the second gas source comprises one or more of carbonyl halides, aldehyde halides, and carboxyl halides;

[0053] A processor controls the first gas source and the second gas source to introduce reaction gas into the reaction space to perform a plasma etching process.

[0054] Optionally, a radio frequency source is further included, which is electrically connected to the base through a matcher.

[0055] Optionally, a cooling circulation system communicated with the base maintains the base at -80°C to 0°C during the etching process.

[0056] Optionally, an auxiliary gas source is further included, connected to the air inlet structure, and the auxiliary gas source includes one or more of O2, H2, NF3, HBr, WF6, and Ar.

[0057] At least one of the above technical solutions has the following advantages or beneficial effects: The present invention provides a gas for plasma etching and a gas combination containing the gas, specifically one or more of a carbonyl halide, an aldehyde halide, and a carboxyl halide. During high-aspect-ratio etching, the gas has a lower bond energy and is more likely to break on one side to form positively charged radicals, which are accelerated to the bottom of the high-aspect-ratio structure. Thereby, the gas contacts the material at the bottom and reacts with it to produce volatile substances, thereby removing the material at the bottom. This facilitates deepening the depth of the hole or trench, and also facilitates lateral etching at the bottom, reducing the difference in critical dimensions between the middle and bottom of the high-aspect-ratio structure. The present invention also provides a semiconductor device and an etching method for plasma etching, comprising a reaction chamber to provide a reaction space, wherein two gases, including one or more of a carbonyl halide, an aldehyde halide, and a carboxyl halide, and one or more of a fluorocarbon and a hydrofluorocarbon, enter the reaction space through a gas inlet structure, causing a processor to generate plasma and control charged particles or active radicals to etch a substrate supported on a susceptor. The purpose of improving the alignment of high aspect ratio structures on the substrate is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0059] FIG1 is a schematic diagram showing chemical structure changes of an etching gas when it is excited into plasma according to an embodiment of the present invention;

[0060] FIG2 is a schematic diagram showing chemical structure changes when an etching gas contacts an etching object according to an embodiment of the present invention;

[0061] FIG3 shows a schematic diagram of the chemical structures of four embodiments of the present invention;

[0062] FIG4 is a schematic diagram showing three common etching defects in the prior art;

[0063] FIG5 shows a schematic diagram showing the principle of improving etching profiles using the gas of the present invention;

[0064] FIG6 is a schematic diagram showing an etching method of the present invention;

[0065] FIG. 7 is a schematic diagram showing a semiconductor device for plasma etching according to the present invention. Best Mode for Carrying Out the Invention

[0066] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0067] In the field of plasma etching, with the increasing demand for etching high-aspect ratio structures, especially in the 3D-NAND field, various etching defects have emerged when using conventional gases or combinations of gases. These defects primarily occur in areas of the etched high-aspect ratio structures that do not meet expectations for CD (critical dimension) performance. This leads to performance degradation or even failure in subsequent chip units formed after filling the high-aspect ratio structures with other materials. To ensure that the etched high-aspect ratio structures meet expectations, the industry has explored numerous methods. However, a plasma etching process involves multiple gases, each of which plays different or overlapping roles. These gases influence each other, and the effects of other parameters such as RF, pressure, and temperature are coupled. Adjusting one parameter can affect others. Whether adjusting the gas type, flow rate, or other parameter values, there are countless possible combinations. Changing one variable can potentially lead to slight improvements in one area but introduce new problems in others. Even for a specific gas type, changing other parameters can lead to different effects throughout the process. Due to the massive results of various combinations, simple enumeration experiments without theoretical guidance cannot meet the urgent requirements of reality for high aspect ratio etching.

[0068] As shown in Figure 1, a schematic diagram of the chemical structure change when the etching gas is excited into plasma is provided, which exemplifies the principle diagram of the function of the second type of gas of the present invention. Taking COF2 as an example, due to the presence of the carbon-oxygen double bond, the bond energy of the chemical bond between carbon and fluorine is relatively small. When the COF2 gas is excited to form a plasma under a certain power of radio frequency energy, the single bond between carbon and fluorine is more easily broken, and according to the currently coupled radio frequency energy, the carbon-fluorine single bond on one side is broken while the carbon-fluorine single bond on the other side is retained, generating positively charged groups containing carbon, oxygen and fluorine and negatively charged fluoride ions, and the positively charged groups are more likely to move in a certain direction under the action of a directional biased radio frequency electric field, which provides conditions for the positively charged groups to reach the bottom along the high aspect ratio structure through the setting of the biased radio frequency.

[0069] As shown in Figure 2, a schematic diagram of the chemical structure changes when the etching gas of an embodiment of the present invention contacts the etching object, when the positively charged group reaches the bottom of the high aspect ratio structure, it will chemically react with the material to be etched. Specifically, another carbon-fluorine single bond of COF+ is broken to release fluoride ions, which react with the material to be etched to generate volatile substances and be discharged, thereby achieving the purpose of continuously etching the high aspect ratio structure.

[0070] In some other embodiments, the etching gas is not limited to COF2, and other compound gases having carbon-oxygen double bonds that can reduce group bond energy and halogen elements that can etch the medium can achieve the same technical effect. Specifically, they can be carbonyl halides, aldehyde halides, and carboxyl halides. The carbonyl group has two low-energy single bonds, so both single bonds can combine with one of the following functional groups: F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-; the aldehyde group and carboxyl group have only one low-energy single bond, so they can combine with one of the following functional groups: F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-. As shown in FIG. 3 , in some embodiments, the etching gases that may be selected include etching gas A: COF 2 ; etching gas B: CF 3 CHO; etching gas C: CO(CF 3 ) 2 ; and etching gas D: CF 3 COOH.

[0071] As shown in Figure 4, there are three common etching defects in the prior art. The substrate used as the etching object usually includes a substrate 1, an etched layer 2 to be etched, and a mask layer 3 with a pattern on the etched layer 2. When the thickness of the etched layer 2 to be etched increases, the aspect ratio of the target structure to be etched, such as a hole or a groove, increases, and some typical defects will appear. Taking the hole as an example, the curved hole 4 has a side wall with an arc curve in the middle because the etching degree in the middle is greater than that in other parts, which destroys the vertical alignment of the ideal hole; the inclined hole 5 has a wedge shape with a wide top and a narrow bottom because the amount of etching material that can reach the bottom is far less than that of the upper and middle parts, which also destroys the vertical alignment of the ideal hole; the short hole 6 has a wedge shape with a wide top and a narrow bottom because the etching material cannot reach the bottom and can only continue to etch in the horizontal direction, which makes it unable to reach the aspect ratio of the ideal hole. In the ideal hole situation, the etching material can continuously etch the material to be etched downward along the size of the mask 3, with only a small amount of lateral etching occurring, ultimately obtaining a high aspect ratio hole that is consistent from top to bottom. The above defects are all caused by the inability of the etching material to etch vertically at a predetermined speed or degree.

[0072] FIG5 shows a schematic diagram of the etching morphology improvement principle achieved by using the gas of the present invention. The substrate to be etched includes a substrate 1, which in some embodiments can be made of Si. The layer to be etched located above the substrate 1 can be a dielectric material or a semiconductor material, or a stack of multiple materials, or a doped mixture, such as a single layer of SiO2, Si3N4 or polycrystalline silicon, as well as an alternating stack of SiO2 and Si3N4, or an alternating stack of SiO2 and polycrystalline silicon. In some embodiments, the layer to be etched includes an alternating stack of SiO2 layers 201 and Si3N4 layers 202. Under the action of the downward electric field E formed by the biased RF, most of the positively charged COF+ groups move downward along the hole 7 to the bottom 220 and then undergo the following reaction:

[0073] COF+ + SiO2→→ SiF4 +CO2

[0074] COF+ + Si3N4→→ SiF4 + CO2 +FCN

[0075] Under the conditions of the reaction space, SiF4, CO2 and FCN are all gases that can be extracted from hole 7, so as to continuously etch hole 7 to form a structure of hole 7 with a high aspect ratio. Because COF+ has good directionality controlled by the electric field, when the mask layer constrains the etching size, most of the COF+ passing through the opening of hole 7 will continue to move downward and will not be consumed on the side wall of the middle part 210 of hole 7, but will reach the bottom 220, and the excess material to be etched compared to the size of the mask layer will be etched away by COF+. Because the middle part 210 is at a shallower position in the hole 7, the etching groups are easier to reach, so the size of the middle part 210 is closer to the size defined by the mask, while the bottom 220 is at a deeper position in the hole 7, and it is difficult for conventional etching gases to reach it through free diffusion, resulting in insufficient etching of the material of the bottom 220, that is, the size of the bottom 220 will be much smaller than the size defined by the mask. Most of the COF+ groups decomposed from the COF2 gas used in the present invention can be pushed toward the bottom 220 by the electric field force, and the COF+ groups can easily release another F ion when contacting the material of the bottom 220. The F ion reacts with the material of the bottom 220 to etch, thereby expanding the lateral opening of the bottom, and no lateral etching occurs in the middle part 210. Therefore, the lateral etching degree of COF+ at the bottom 220 will be greater than that of the middle part 220, avoiding the curved hole 4 and the inclined hole 5 in Figure 4.

[0076] In some embodiments, the gas combination for plasma etching includes one or more of carbonyl halides, aldehyde halides, and carboxyl halides as the second type of gas, and also includes one or more of fluorocarbons and hydrofluorocarbons as the first type of gas. The ratio of the first type of gas to the second type of gas can be adjusted to obtain a suitable etching result. Specifically, the first type of gas can include one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5. In other embodiments, the gas combination can also include one or more of O2, H2, NF3, HBr, WF6, and Ar as auxiliary gases.

[0077] The present invention also provides a plasma etching method, as shown in FIG6 , which specifically includes:

[0078] Step 601: Provide a substrate. The substrate has a layer to be etched, which may be SiO2, Si3N4, or a combination of the two. A mask layer to constrain the etching results is provided on the layer to be etched. The mask layer may be a material with a high etching selectivity relative to the layer to be etched, such as amorphous carbon. In some embodiments, the layer to be etched may have shallow holes or grooves etched in a previous step, or may be an unprocessed layer.

[0079] Step 602: introduce a process gas. The process gas includes a second type of gas, such as one or more of a carbonyl halide, an aldehyde halide, and a carboxyl halide. In some embodiments, the second type of gas may be COF2, COCl2, COBr2, COI2, (CF3)-CO-H, (CF3)CO-F, (CF3)-CO-Cl, (CF3)-CO-OH, (CF3)-CO-(CF3), or (CF3)-CO-O-CO-(CF3). The second type of gas is used to etch the layer to be etched until a hole or groove with a predetermined aspect ratio is formed. The flow rate of the second type of gas ranges from 10 sccm to 200 sccm.

[0080] Depending on the target to be etched, the process gas may also include a first type of gas, such as one or more fluorocarbons or hydrofluorocarbons. In some embodiments, the first type of gas may include CF4, CHF3, CH2F2, C2HF5, C3HF5, or a combination thereof. The first type of gas can etch the target layer and protect the sidewalls of high aspect ratio holes or trenches. The flow rate of the first type of gas ranges from 10 sccm to 300 sccm.

[0081] In other embodiments, the process gas may also include auxiliary gases, such as O2 and NF3 to prevent excessive polymer deposition and clogging on the top of the holes or trenches; H2 to improve the selectivity between the mask and the layer to be etched; and HBr and WF6 to enhance hole or trench sidewall protection and prevent sidewall bowing. The auxiliary gas flow rate range is 1 sccm-200 sccm.

[0082] In some embodiments, the volume ratio of the first type of gas to the total gas volume is 30%-70%, and the volume ratio of the second type of gas to the total gas volume is 1%-30%. The volume ratio of the auxiliary gas to the total gas volume is 10%-30%. The first type of gas accounts for the majority of the total volume and plays the primary role in etching. The second type of gas modifies the high aspect ratio structures with defects etched by the first type of gas, resulting in a CD that is as consistent as possible in the vertical direction.

[0083] In step 603, the radio frequency is connected to excite the process gas into a plasma. By selecting an appropriate radio frequency, the concentration of charged particles or active groups in the plasma can be controlled, thereby adjusting the etching rate. In order to achieve the desired etching results under the gas combination conditions of the present invention, the frequency range of the radio frequency used to generate the plasma is: 13MHz-200MHz; the power range is: 1000w-30000w. The radio frequency used to generate the plasma must ensure that the gas can be ionized, but it must not output too high a power that would pose a risk to the process reaction.

[0084] Step 604, etching the layer to be etched on the substrate. In this step, bias RF energy is loaded into the plasma in the reaction space. The bias RF can provide a directional electric field, so that the charged particles that can etch the layer to be etched enter the inside of the hole or groove, maintain a suitable etching rate, and keep the upper and lower CDs of the hole or groove consistent. The frequency range of the bias RF used is 150kHz-4MHz; the power range is: 1kW-10kW. Finally, a hole or groove with a high aspect ratio structure is formed in the layer to be etched, and the aspect ratio range is greater than 20. In some embodiments, the aspect ratio range is greater than 40. The frequency of the bias RF must ensure that the COF+ group can reach the bottom.

[0085] To maintain the plasma and expel reaction byproducts, the reaction space must be continuously evacuated to maintain a certain pressure, ranging from 15mT to 40mT. To ensure that the polymer generated during the process protects the sidewalls of the holes or trenches from lateral overetching while preventing excessive accumulation that could clog the etching channels, the substrate temperature must be controlled between -50°C and 100°C. In some embodiments, the substrate temperature is between 0°C and 10°C.

[0086] In some embodiments, the first type of gas and the second type of gas can be used to etch an etching object with a complete layer to be etched until a hole or groove with a high aspect ratio that meets the target is formed; in other embodiments, the etching of the layer to be etched can be divided into two stages. In the first stage, shallow holes or grooves are etched through preliminary treatment. For example, the first type of gas is used in combination with some types of auxiliary gases. Since the first type of gas has a higher proportion of fluorine content, a higher etching rate can be guaranteed. At this time, since the depth of the hole or groove in the layer to be etched is small, the etching gas can easily reach the bottom of the hole or groove, and the problem shown in Figure 4 will not occur. In the second stage, a gas combination containing the second type of gas is used to continue etching the shallow hole or groove until a hole or groove with a high aspect ratio that meets the target is formed, which ensures both a higher etching rate and a good etching morphology.

[0087] The following lists the parameters and etching results of some embodiments under the condition of a susceptor temperature of -60°C, taking the overlapping layer to be etched of SiO2 and Si3N4 as the etching object.

[0088] Comparative Example 1

[0089]

[0090] Taking the above situation as an example, when CF4 is selected as the first type of gas and H2, NF3, HBr and Ar as the auxiliary gases, when etching to a depth-to-width ratio of about 40, the CD difference between the middle and the bottom reaches 45nm, which obviously does not meet the final result requirements.

[0091] Example 1

[0092]

[0093] With other conditions unchanged relative to "Comparative Example 1", 10 sccm of COF2 was added as the second type of gas. It can be seen that even when the aspect ratio increased to about 50, the CD difference between the middle and bottom was improved and reduced to about 40nm.

[0094] Example 2

[0095]

[0096] With other conditions unchanged relative to Example 1, the COF2 flow rate is further increased to 30 sccm. It can be seen that even when the aspect ratio continues to increase, the CD difference between the middle and bottom continues to improve to 30 nm.

[0097] Example 3

[0098]

[0099] With other conditions unchanged relative to Example 1, the COF2 flow rate is further increased to 70 sccm. It can be seen that with the aspect ratio remaining basically unchanged, the CD difference between the middle and bottom portions continues to improve to 20 nm.

[0100] Example 4

[0101]

[0102] With other conditions remaining unchanged relative to Example 1, the COF2 flow rate is further increased to 100 sccm. It can be seen that with the aspect ratio remaining basically unchanged, the CD difference between the middle and bottom is further improved to about 15 nm. However, the yield ratio has been significantly reduced relative to the increased COF2 amount.

[0103] Through comparative experiments, a small amount of COF2 can improve the morphology of high aspect ratio structures. When the flow rate of COF2 is controlled within the range of 20sccm-70sccm, or the volume ratio is within the range of 1%-30%, the improvement effect can maximize the benefits relative to the dosage.

[0104] The present invention relates to etching gases and their combinations, etching methods, and etching equipment, which contain one or more of carbonyl halides, aldehyde halides, and carboxyl halides as reactive gases. Such gases have a double bond combining carbon (C) and oxygen (O). Due to the presence of the O atom on the double bond, the other two halogen-containing groups or halogen atoms bound to the C are more likely to break away from the constraints of the C. When a certain amount of radio frequency energy is applied, one of the halogen-containing groups or halogen atoms first breaks away, turning the gas atom into a positively charged group. The positively charged group is more easily accelerated by the radio frequency electric field toward the bottom of a high-aspect-ratio structure, and reacts with the material to be etched at the bottom to achieve removal of the bottom material. The lateral etching of the bottom by the group simultaneously achieves consistency in the upper and lower characteristic dimensions (CD) of the high-aspect-ratio structure.

[0105] The second type of gas in the present invention primarily comprises halogen gases containing carbon-oxygen double bonds. Unlike this type of gas used as an oxidizing gas, the present invention innovatively discovered that this gas can easily separate one of the fluoride ions into a charged COF+ during plasma dissociation. When a biased RF power source is applied to the substrate to be etched, the charged COF+ group, under the action of the biased RF electric field, can reach the bottom of the etched hole or trench and, upon contact with the material at the bottom 220, release another fluoride ion to participate in the etching reaction. This significantly increases the CD at the bottom of the hole or trench, reduces the difference between the CD at the bottom and the CD at the middle, and improves the verticality of the sidewalls of the etched hole or trench. This is particularly true for etched structures with high aspect ratios, where the CD at the bottom opening gradually decreases beyond a certain depth. The gas disclosed in the present invention has an unexpected effect.

[0106] The present invention further discloses a semiconductor device 100 for plasma etching, which specifically includes a reaction chamber 10 as shown in FIG7 , wherein a reaction space is formed inside the reaction chamber for performing a plasma etching process;

[0107] An air inlet structure 30 is used to introduce process gas into the reaction space; a base 101 is used to carry a substrate 103. The base 101 includes an electrostatic chuck 102, which can clamp the substrate 103 by electrostatic attraction. An edge ring 20 is provided around the base 101, which can expand the range of the lower electrode to make the etching of the substrate 103 more uniform. A confinement ring 108 is also provided between the edge ring 20 and the side wall of the reaction chamber 10. An exhaust pump is provided below the confinement ring 108 to extract excess gas and reaction by-products in the reaction space. The confinement ring 108 can prevent plasma from entering the exhaust space below during the exhaust process, causing discharge and other structural damage. A grounding ring 109 is connected to the bottom of the confinement ring 108 to realize a complete radio frequency circuit inside the reaction chamber 10.

[0108] A first gas source 31 is connected to the gas intake structure 30, and the first gas source 31 contains one or more of fluorocarbons and hydrofluorocarbons; a second gas source 32 is connected to the gas intake structure 30, and the second gas source 32 contains one or more of carbonyl halides, aldehyde halides, and carboxyl halides; and an auxiliary gas source 33 is also included, which is connected to the gas intake structure 30, and the auxiliary gas source contains one or more of O2, H2, NF3, HBr, and WF6.

[0109] The processor 40 controls the first gas source 31 , the second gas source 32 and the auxiliary gas source 33 through electronic circuits and corresponding valves, flow controllers, etc. to introduce reaction gases into the reaction space to perform a plasma etching process.

[0110] It also includes a radio frequency source, which is electrically connected to the base 101 through a matcher, and specifically may include a high-frequency radio frequency power supply 51 for generating plasma, which is electrically connected to the base 101 through a high-frequency radio frequency match 52; and a bias radio frequency power supply 53 for controlling the movement direction of charged groups, which is electrically connected to the base 101 through a bias radio frequency match 54.

[0111] In order to control the temperature of the substrate 103, a cooling circulation system 104 connected to the base 101, such as a cooling circulation pipeline with a cooling fluid, can also set parameters through the controller 40 so that the temperature of the base 101 can be maintained at -80℃-0℃ during the etching process.

[0112] The plasma etching method disclosed in the present invention is not limited to being applied to the plasma processing apparatus of the above embodiment, but can also be applied to other plasma processing apparatuses, which will not be described in detail here.

[0113] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A plasma etching method, characterized in that: The steps include: Providing a substrate having a layer to be etched and a mask layer above the layer to be etched; After the first type of gas and the second type of gas are introduced, they are excited to form plasma to etch the layer to be etched to form holes or grooves; The first type of gas includes one or more of fluorocarbons and hydrofluorocarbons; The second type of gas includes one or more of carbonyl halides, aldehyde halides, and carboxyl halides.

2. The plasma etching method according to claim 1, characterized in that: The carbonyl halide includes a functional group (CO)- and a combination of one or two of the functional groups F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-.

3. The plasma etching method according to claim 1, characterized in that: The aldehyde halide includes a combination of a functional group (COH)- and one of the functional groups F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-.

4. The plasma etching method according to claim 1, characterized in that: The carboxyl halide includes a combination of a functional group (COOH)- and one of the functional groups F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-.

5. The plasma etching method according to claim 1, characterized in that: The second type of gas includes COF 2。 6. The plasma etching method according to claim 5, characterized in that: The first type of gas includes one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5.

7. The plasma etching method according to claim 6, characterized in that: The volume ratio of the first type of gas to the total gas is 30%-70%; the volume ratio of the second type of gas to the total gas is 1%-30%.

8. The plasma etching method according to claim 6, characterized in that: The flow rate range of the first type of gas is: 10sccm-300sccm; the flow rate range of the second type of gas is: 5sccm-200sccm.

9. The plasma etching method according to claim 1, characterized in that: When the first and second gases are introduced, an auxiliary gas is also introduced, and the auxiliary gas includes one or more of O2, H2, NF3, HBr, WF6, and Ar.

10. The plasma etching method according to claim 9, characterized in that: The volume ratio of the auxiliary gas to the total gas is 10%-30%.

11. The plasma etching method according to claim 9, characterized in that: The flow rate range of the auxiliary gas is: 1 sccm-200 sccm.

12. The plasma etching method according to claim 1, characterized in that: The layer to be etched includes SiO2, Si3N4, polysilicon or an alternating stack of any two thereof.

13. The plasma etching method according to claim 1, wherein: The aspect ratio of the hole or the groove is greater than 40.

14. The plasma etching method according to claim 1, characterized in that: When the plasma is excited, the frequency range of the radio frequency is: 13MHz-200 MHz; the power range is: 1000W-30000W.

15. The plasma etching method according to claim 1, wherein: When etching the layer to be etched, the temperature range of the substrate is: -50°C~100°C.

16. The plasma etching method according to claim 1, wherein: When etching the layer to be etched, the gas pressure range is: 15mT-40mT.

17. A gas combination for plasma etching, characterized in that: include: Category I gases include one or more of fluorocarbons and hydrofluorocarbons; The second type of gas includes one or more of carbonyl halides, aldehyde halides, and carboxyl halides; The auxiliary gas includes one or more of O2, H2, NF3, HBr, WF6, and Ar.

18. The gas combination according to claim 17, characterized in that The carbonyl halide comprises a functional group (CO)- and a functional group F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I- in combination with one or two thereof; the aldehyde halide comprises a functional group (COH)- and a functional group F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I- in combination with one thereof; the carboxyl halide comprises a functional group (COOH)- and a functional group F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I- in combination with one thereof; A combination of one of CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-.

19. The gas combination according to claim 17, characterized in that The first type of gas includes one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5.

20. A plasma etching method, characterized in that: The steps include: Providing an etching object having a hole or groove structure thereon; A process gas containing COF2 is provided and excited into plasma, and the hole or the groove is further etched by applying biased radio frequency.

21. The etching method according to claim 20, characterized in that: When the COF2 is excited into plasma, COF2 can be decomposed into COF+ groups and F-. The COF+ groups reach the bottom of the hole or groove under the action of the biased radio frequency and chemically react with the etching object at the bottom of the hole or groove to generate volatile products.

22. The etching method according to claim 21, characterized in that: The lateral etching amount of the COF+ group at the bottom of the hole or trench is greater than the lateral etching amount of the COF+ group at the middle of the hole or trench.

23. The etching method according to claim 20, characterized in that: The etching object includes SiO2, Si3N4, polysilicon or an alternating stack of any two thereof.

24. The etching method according to claim 20, characterized in that: The frequency range of the bias radio frequency is: 150kHz-4MHz; the power range is: 500W-10kW.

25. The etching method according to claim 20, characterized in that: The following steps are also included: Providing a substrate having a layer to be etched and a mask layer above the layer to be etched, wherein the layer to be etched is composed of SiO2, Si3N4 or an alternating stack of the two; A process gas containing one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5 is provided and excited into plasma to form the holes or grooves on the substrate.

26. The etching method according to claim 20, characterized in that: The temperature range of the etching object is: -30°C ~ 60°C.

27. The etching method according to claim 20, characterized in that: The aspect ratio of the hole or the groove is greater than 20.

28. A gas for plasma etching, characterized in that: The gas includes COF2, which can be decomposed into COF+ radicals and F- in a plasma state, and the COF+ radicals can etch the dielectric material or semiconductor material at the bottom of the hole or groove under the action of biased radio frequency.

29. The gas according to claim 28, characterized in that The frequency range of the bias radio frequency is: 150kHz-400kHz; the power range is: 500W-10kW.

30. The gas according to claim 28, characterized in that The aspect ratio of the hole or the groove is greater than 20.

31. The gas according to claim 28, characterized in that The dielectric material includes SiO2 or Si3N4; the semiconductor material includes polysilicon.

32. A semiconductor device, characterized in that: include: A reaction chamber, wherein a reaction space is formed inside the reaction chamber for performing a plasma etching process; An air inlet structure, used for introducing process gas into the reaction space; A base, used for carrying a substrate; A first gas source connected to the gas inlet structure, wherein the first gas source comprises one or more of fluorocarbons and hydrofluorocarbons; a second gas source connected to the gas inlet structure, wherein the second gas source comprises one or more of carbonyl halides, aldehyde halides, and carboxyl halides; A processor controls the first gas source and the second gas source to introduce reaction gas into the reaction space to perform a plasma etching process.

33. The semiconductor device according to claim 20, wherein: The invention also comprises a radio frequency source which is electrically connected to the base through a matching device.

34. The semiconductor device according to claim 20, wherein: A cooling circulation system connected to the base maintains the base at -80°C to 0°C during the etching process.

35. The semiconductor device according to claim 20, wherein: It also includes an auxiliary gas source connected to the air intake structure, and the auxiliary gas source includes one or more of O2, H2, NF3, HBr, WF6, and Ar.

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