Gases, gas combinations, etching methods, and semiconductor equipment for plasma etching.

Abstract

This invention provides a gas, gas combination, etching method, and semiconductor equipment for plasma etching, belonging to the field of plasma etching. It mainly utilizes one or more of carbonyl halides, aldehyde halides, and carboxyl halides as process gases during the etching process to excite the formation of plasma, which is then used to etch the layer to be etched. This solves the problem of inconsistency between the bottom and middle etching rates when high aspect ratio holes or trenches are formed to a certain extent during etching, significantly improving the morphology of high aspect ratio etching, ensuring collimation, and enhancing the effectiveness of semiconductor structures.

Description

Technical Field

[0001] This invention relates to the field of plasma etching technology, and more particularly to the field of plasma etching gas, gas combination, etching method and semiconductor equipment technology for etching objects with high aspect ratio. Prior Technology

[0002] Microfabrication of semiconductor substrates is a well-known technique used to manufacture, for example, semiconductors, flat panel displays, light-emitting diodes (LEDs), and solar cells. A crucial step in microfabrication is the plasma processing step, which takes place inside a reaction chamber where process gases are introduced. An radio frequency (RF) source, coupled to the reaction chamber by inductors and / or capacitors, excites the process gases to form and maintain the plasma.

[0003] As the pursuit of Moore's Law progressed, various process technologies and semiconductor structures were invented. Whether it's logic chips or memory chips, an increasing number of high aspect ratio structures require etching using plasma technology.

[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 predetermined depth is etched, it is easy to produce morphological deviations. When the upper and lower dimensions of the high aspect ratio structure are not consistent, or when defects such as unevenness or bending occur in local areas, it will further affect the conductivity of subsequent devices, and in severe cases, it will cause the devices to fail. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a plasma etching method, comprising the following steps: A substrate is provided, having a layer to be etched and a masking layer above the layer to be etched; After introducing a first type of gas and a second type of gas, plasma etching is excited to form the layer to be etched, creating holes or trenches. 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.

[0006] Optionally, the carbonyl halide includes a functional group (CO)- and a combination of one or two of the functional groups F-, Cl-, Br-, I-, CF 3-, CHF 2-, CH 2F-, CCl 3-, CHCl 2-, CH 2Cl-, CBr 3-, CHBr 2-, CH 2Br-, CI 3-, CHI 2-, and CH 2I-.

[0007] Optionally, the aldehyde halide comprises a combination of a functional group (COH)- and a functional group selected from F-, Cl-, Br-, I-, CF 3-, CHF 2-, CH 2F-, CCl 3-, CHCl 2-, CH 2Cl-, CBr 3-, CHBr 2-, CH 2Br-, CI 3-, CHI 2-, and CH 2I-.

[0008] Optionally, the carboxyl halide comprises a combination of the functional group (COOH)- and one of the functional groups F-, Cl-, Br-, I-, CF 3-, CHF 2-, CH 2F-, CCl 3-, CHCl 2-, CH 2Cl-, CBr 3-, CHBr 2-, CH 2Br-, CI 3-, CHI 2-, and CH 2I-.

[0009] Optionally, the second type of gas includes COF2.

[0010] Optionally, the first type of gas includes one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5.

[0011] Optionally, the volume of the first type of gas accounts for 30% to 70% of the total gas volume; the volume of the second type of gas accounts for 1% to 30% of the total gas volume.

[0012] Optionally, the flow rate range of the first type of gas is 10 sccm to 300 sccm; and the flow rate range of the second type of gas is 5 sccm to 200 sccm.

[0013] Optionally, when introducing the first type of gas and the second type of gas, an auxiliary gas is also introduced, the auxiliary gas comprising one or more of O2, H2, NF3, HBr, WF6, and Ar.

[0014] Optionally, the volume ratio of the auxiliary gas to the total gas volume is 10% to 30%.

[0015] Optionally, the flow rate of the auxiliary gas is in the range of 1 sccm to 200 sccm.

[0016] Optionally, the layer to be etched includes SiO2, Si3N4, polycrystalline silicon, or any two of them stacked alternately.

[0017] Optionally, the aspect ratio of the hole or groove is greater than 40.

[0018] Optionally, when the plasma is excited, the frequency range of the radio frequency is 13MHz to 200MHz, and the power range is 1000W to 30000W.

[0019] Optionally, when etching the layer to be etched, the temperature range of the substrate is -50℃ to 100℃.

[0020] Optionally, when etching the layer to be etched, the gas pressure range is 15mT~40mT.

[0021] Furthermore, the present invention also provides a gas combination for plasma etching, comprising: Class I gases include one or more of fluorocarbons and hydrofluorocarbons; The second category of gases 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.

[0022] Optionally, the carbonyl halide includes a functional group (CO)- and a combination of one or more of the functional groups F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, and CH2I-; the aldehyde halide includes a functional group (COH)- and a combination of the functional groups F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, and CH2I-. A combination of one of the following: 2I-; the carboxyl halide includes a combination of the functional group (COOH)- and the functional groups F-, Cl-, Br-, I-, CF 3-, CHF 2-, CH 2F-, CCl 3-, CHCl 2-, CH 2Cl-, CBr 3-, CHBr 2-, CH 2Br-, CI 3-, CHI 2-, CH 2I-.

[0023] Optionally, the first type of gas includes one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5.

[0024] Furthermore, the present invention also provides a plasma etching method, comprising the following steps: Provide an etched object having a structure with holes or grooves; A process gas containing COF2 is provided and excited into a plasma, through which the holes or trenches are etched by applying a bias radio frequency.

[0025] Optionally, when the COF2 is excited into plasma, the COF2 can decompose into COF+ groups and F-. The COF+ groups reach the bottom of the hole or trench under the action of the bias radio frequency and react chemically with the etched object at the bottom of the hole or trench to generate volatile products.

[0026] Optionally, the COF+ group is etched laterally at the bottom of the hole or groove by a greater amount than it is etched laterally in the middle of the hole or groove.

[0027] Optionally, the etched object includes SiO2, Si3N4, polycrystalline silicon, or an alternating stack of any two thereof.

[0028] Optionally, the frequency range of the bias radio frequency is 150kHz to 4MHz; the power range is 500W to 10kW.

[0029] Optionally, the following steps may also be included: A substrate is provided having a layer to be etched and a masking layer above the layer to be etched, wherein the layer to be etched is composed of SiO2, Si3N4, or an alternating stack of both; A process gas comprising one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5 is provided and excited into a plasma to form the holes or grooves on the substrate.

[0030] Optionally, the temperature range of the etched object is -30℃ to 60℃.

[0031] Optionally, the aspect ratio of the hole or groove is greater than 20.

[0032] Furthermore, the present invention also provides a gas for plasma etching, the gas comprising COF2, wherein the COF2 can decompose into COF+ groups and F- in the plasma state, and the COF+ groups can etch the dielectric or semiconductor material at the bottom of the hole or trench under bias radio frequency action.

[0033] Optionally, the frequency range of the bias radio frequency is 150kHz to 400kHz; the power range is 500W to 10kW.

[0034] Optionally, the aspect ratio of the hole or groove is greater than 20.

[0035] Optionally, the dielectric material includes SiO2 or Si3N4; the semiconductor material includes polycrystalline silicon.

[0036] Furthermore, the present invention also provides a semiconductor device, comprising: The reaction chamber, which forms a reaction space inside, is used to perform the plasma etching process; An air intake structure is used to introduce process gas into the reaction space; The base is used to support the substrate; A first gas source is connected to the air intake structure, and the first gas source contains one or more of fluorocarbons and hydrofluorocarbons. A second gas source is connected to the air intake structure, and the second gas source contains one or more of carbonyl halides, aldehyde halides, and carboxyl halides; The processor controls the first and second gas sources to introduce reactive gases into the reaction space to perform a plasma etching process.

[0037] Optionally, it also includes an RF source, which is electrically connected to the base via a matching unit.

[0038] Optionally, a cooling circulation system connected to the base is provided to maintain the base at -80°C to 0°C during the etching process.

[0039] Optionally, it also includes an auxiliary gas source connected to the intake structure, the auxiliary gas source comprising one or more of O2, H2, NF3, HBr, WF6, and Ar.

[0040] At least one of the above technical solutions has the following advantages or beneficial effects: This invention provides a gas for plasma etching, and a gas combination containing the gas, specifically one or more of carbonyl halides, aldehyde halides, and carboxyl halides. During high aspect ratio etching, this gas has a lower bond energy, making it easier to break one side and form positively charged groups, which are then accelerated to the bottom of the high aspect ratio structure. This allows it to contact the bottom material and undergo an etching reaction to generate volatile substances, achieving material removal from the bottom. This is beneficial for increasing the depth of holes or trenches, and also for lateral etching at the bottom, reducing the difference in critical dimensions between the middle and bottom of the high aspect ratio structure. This invention also provides a semiconductor device and an etching method for plasma etching, including a reaction chamber to provide a reaction space. Two types of gases, one containing carbonyl halides, aldehyde halides, and carboxyl halides, and one or more containing fluorocarbons and hydrofluorocarbons, enter the reaction space through an inlet structure, causing the processor to generate plasma and control charged particles or active groups to etch the substrate carried on the substrate. The goal is to improve the collimation of high aspect ratio structures on the substrate. Simple Explanation of the Diagram

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without making any progress. Figure 1 shows a schematic diagram of the chemical structure change when the etching gas is excited into plasma according to an embodiment of the present invention; Figure 2 shows a schematic diagram of the chemical structure change when the etching gas comes into contact with the etched object according to an embodiment of the present invention; Figure 3 shows schematic diagrams of the chemical structures of four embodiments of the present invention; Figure 4 illustrates three common etching defects found in prior art. Figure 5 illustrates the principle of improved etching morphology achieved using the gas of the present invention; Figure 6 shows a schematic diagram of the etching method of the present invention; Figure 7 shows a schematic diagram of the semiconductor device for plasma etching according to the present invention. Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making progressive efforts are within the scope of protection of the present invention.

[0043] In the field of plasma etching, the demand for high aspect ratio structures is increasing, especially in the 3D-NAND field. However, when using conventional gases or combinations for etching, various etching defects have emerged. These defects primarily stem from the fact that the critical dimension (CD) of the etched high aspect ratio structures does not meet expectations in various regions. This leads to performance degradation or failures in the wafer cells 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 many methods. However, a single plasma etching process involves multiple gases, each playing a different or overlapping role. These gases influence each other, and the effects of other parameters such as radio frequency, gas pressure, and temperature are also coupled. Adjusting one parameter can affect others. Whether adjusting the type or flow rate of the gas, or adjusting the values ​​of other parameters, there are countless combinations. It is very likely that changing one variable, while making a slight improvement in one aspect, introduces new problems in others. Even for a particular type of gas, changing other parameters can cause that gas to play a different role throughout the process. The sheer volume of results from various combinations meant that simply listing experiments without theoretical guidance could not meet the urgent real-world requirements for high aspect ratio etching.

[0044] Figure 1 illustrates the chemical structure changes when the etching gas is excited into plasma, demonstrating the principle of the second type of gas in this invention. Taking COF2 as an example, due to the presence of carbon-oxygen double bonds, the bond energy of the chemical bond between carbon and fluorine is relatively small. When COF2 gas is excited to form plasma under a certain power of radio frequency energy, the single bond between carbon and fluorine is more likely to break. Depending on the current coupled radio frequency energy, the carbon-fluorine single bond on one side breaks while the carbon-fluorine single bond on the other side remains, generating positively charged groups containing carbon, oxygen, and fluorine, and negatively charged fluoride ions. The positively charged groups are more likely to move in a certain direction under the action of a directional bias radio frequency electric field, which provides the conditions for the positively charged groups to reach the bottom along the high aspect ratio structure through the setting of the bias radio frequency.

[0045] Figure 2 shows a schematic diagram of the chemical structure change when the etching gas comes into contact with the etched object according to an embodiment of the present invention. When the positively charged group reaches the bottom of the high aspect ratio structure, it will react chemically with the material to be etched. Specifically, another carbon-fluorine single bond of COF+ breaks, releasing fluorine ions, which react with the material to be etched to generate volatile substances that are discharged, thereby achieving the purpose of continuously etching the high aspect ratio structure.

[0046] In some other embodiments, the etching gas is not limited to COF2; other compound gases containing 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, these can be carbonyl halides, aldehyde halides, and carboxyl halides. The carbonyl group has two low-energy single bonds, so both bonds can combine with one of the following functional groups: F-, Cl-, Br-, I-, CF 3-, CHF 2-, CH 2F-, CCl 3-, CHCl 2-, CH 2Cl-, CBr 3-, CHBr 2-, CH 2Br-, CI 3-, CHI 2-, CH 2I-. The aldehyde and carboxyl groups have only one low-energy single bond, so they can combine with one of the following functional groups: F-, Cl-, Br-, I-, CF 3-, CHF 2-, CH 2F-, CCl 3-, CHCl 2-, CH 2Cl-, CBr 3-, CHBr 2-, CH 2Br-, CI 3-, CHI 2-, CH 2I-. As shown in Figure 3, in some embodiments, the etching gas can be selected as follows: Etching gas A: COF2; Etching gas B: CF3CHO; Etching gas C: CO(CF3)2; Etching gas D: CF3COOH.

[0047] Figure 4 illustrates three common etching defects in prior art. The substrate typically used for etching includes a substrate 1, an etchable layer 2, and a patterned masking layer 3 on the etchable layer 2. When the thickness of the etchable layer 2 increases, increasing the aspect ratio of the target structure to be etched, such as a hole or groove, some typical defects will occur. Taking a hole as an example, a curved hole 4 has a curved sidewall in the middle because the etching degree in the middle part is greater than that in other parts, which destroys the vertical alignment of the ideal hole. An angled hole 5 has far less etchable material reaching the bottom than in the upper and middle parts, resulting in a wedge shape that is wider at the top and narrower at the bottom, which also destroys the vertical alignment of the ideal hole. A short hole 6 has etchable material that cannot reach the bottom and can only continue etching horizontally, which makes it impossible to achieve the ideal aspect ratio of the hole. Ideally, the etchant can continuously etch downwards along the dimensions of the mask layer 3, with only a small amount of lateral etching, ultimately resulting in a high aspect ratio hole with consistent depth and width. The above defects are caused by the etchant failing to etch longitudinally at a predetermined speed or degree.

[0048] Figure 5 shows a schematic diagram of the etching morphology improvement achieved 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, a semiconductor material, a stack of multiple materials, or a doped mixture, such as a single layer of SiO2, Si3N4, or polycrystalline silicon, as well as alternating stacks of SiO2 and Si3N4, or alternating stacks of SiO2 and polycrystalline silicon. Optionally, in some embodiments, the layer to be etched includes an alternating stack of SiO2 layer 201 and Si3N4 layer 202. Under the action of the downward electric field E formed by the bias radio frequency, most of the positively charged COF+ groups move downward along the hole 7 to the bottom 220 and undergo the following reaction: COF+ + SiO2 → SiF4+ CO2 COF+ + Si 3N 4 → SiF 4+ CO 2+ FCN Under the conditions of the reaction space, SiF4, CO2 and FCN are all gases that can be drawn out from the hole 7, achieving continuous etching of the hole 7 to form a structure with a high aspect ratio. Because COF+ has good directionality controlled by the electric field, when the masking layer constrains the etching size, most of the COF+ passing through the opening of the hole 7 will continue to travel downwards and will not be consumed on the side wall of the middle 210 of the hole 7, but will reach the bottom 220. Moreover, the excess material to be etched compared with the size of the masking layer will be etched away by COF+. Because the middle part 210 is located at a shallower position in the hole 7, the groups that perform the etching function are more easily reached. Therefore, the size of the middle part 210 is closer to the size defined by the mask. On the other hand, the bottom part 220 is located at a deeper position in the hole 7, and conventional etching gas has difficulty reaching it through free diffusion. This results in insufficient etching of the material in the bottom part 220, which means that the size of the bottom part 220 is much smaller than the size defined by the mask. Most of the COF+ groups decomposed from the COF2 gas used in this invention can be pushed towards the bottom part 220 by the electric field force. When the COF+ groups come into contact with the material in the bottom part 220, they easily release another F ion. This F ion reacts with the material in the bottom part 220 to enlarge the lateral opening at the bottom, instead of lateral etching in the middle part 210. Therefore, the degree of lateral etching of COF+ in the bottom part 220 is greater than that in the middle part 210, avoiding the appearance of the curved hole 4 and the oblique hole 5 in Figure 4.

[0049] In some embodiments, the gas composition for plasma etching includes one or more of carbonyl halides, aldehyde halides, and carboxyl halides as a second type of gas, and one or more of fluorocarbons and hydrofluorocarbons as a first type of gas. The ratio of the first type of gas to the second type of gas can be adjusted to obtain suitable etching results. Specifically, the first type of gas may include one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5. In other embodiments, the gas composition may also include one or more of O2, H2, NF3, HBr, WF6, and Ar as auxiliary gases.

[0050] The present invention also provides a plasma etching method, as shown in Figure 6, which specifically includes:

[0051] Step 601: Provide a substrate. The substrate has a layer to be etched, which can be SiO2, Si3N4, or a combination of both. A masking layer constrains the etching result on the layer to be etched, which can be amorphous carbon or other materials with a high etch selectivity relative to the layer to be etched. In some embodiments, the layer to be etched may have shallow holes or shallow trenches already etched in the previous step, or it may be an incompletely processed layer.

[0052] Step 602: Introduce a process gas. This process gas includes a second type of gas, such as one or more of carbonyl halides, aldehyde halides, and carboxyl halides. 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 layer to be etched is etched using the second type of gas until holes or trenches with a predetermined aspect ratio are formed. The flow rate of the second type of gas ranges from 10 sccm to 200 sccm.

[0053] Depending on the object being etched, the process gas may also include a first-class gas, such as one or more of fluorocarbons and hydrofluorocarbons. In some embodiments, the first-class gas may be CF4, CHF3, CH2F2, C2HF5, C3HF5, or a combination thereof. The first-class gas can serve to etch the layer to be etched and protect the sidewalls of high aspect ratio holes or trenches. The flow rate range of the first-class gas is 10 sccm to 300 sccm.

[0054] In other embodiments, the process gas may also include auxiliary gases, such as O2 and NF3 to prevent excessive polymer deposition and clogging at the top of the holes or trenches; H2 to improve the selectivity of the mask and the layer to be etched; and HBr and WF6 to strengthen the protection of the hole or trench sidewalls and prevent sidewall bending. The flow rate of the auxiliary gas is in the range of 1 sccm to 200 sccm.

[0055] In some embodiments, the volume ratio of the first type of gas to the total gas volume is 30% to 70%; the volume ratio of the second type of gas to the total gas volume is 1% to 30%; and the volume ratio of the auxiliary gas to the total gas volume is 10% to 30%. The first type of gas, which constitutes the majority of the total volume, plays a major etching role, while the second type of gas modifies the high aspect ratio structure with defects etched by the first type of gas, making it have a CD (cutoff diameter) as consistent as possible in the vertical direction.

[0056] Step 603 involves using radio frequency (RF) to excite the process gas into plasma. By selecting a suitable RF, the concentration of charged particles or active groups in the plasma can be controlled, thereby adjusting the etching rate. To achieve the desired etching result under the gas combination conditions of this invention, the RF frequency range for plasma generation is 13MHz to 200MHz, and the power range is 1000W to 30000W. The RF for plasma generation must ensure that the gas can be ionized, but it must not output excessive power that could endanger the process reaction.

[0057] Step 604: Etching the layer to be etched on the substrate. In this step, bias radio frequency (RF) energy is applied to the plasma in the reaction space. The RF provides a directional electric field, allowing charged particles capable of etching the layer to enter the interior of the hole or trench, maintaining a suitable etching rate, and ensuring that the upper and lower CD (cutoff direction) of the hole or trench remains consistent. The frequency range of the bias RF used is 150 kHz to 4 MHz; the power range is 1 kW to 10 kW. Ultimately, a hole or trench with a high aspect ratio is formed in the layer to be etched, with an aspect ratio greater than 20, and in some embodiments, a range greater than 40. The frequency of the bias RF must ensure that the COF+ groups can reach the bottom.

[0058] To maintain the plasma and ensure timely removal of reaction byproducts, continuous evacuation of the reaction space is required to maintain a certain gas pressure, ranging from 15 mT to 40 mT. Furthermore, to ensure that the polymer generated during the process protects the sidewalls of the holes or trenches from lateral over-etching while preventing excessive accumulation that could clog the etching channels, the substrate temperature needs to be controlled between -50°C and 100°C. In some embodiments, the substrate temperature is maintained between 0°C and 10°C.

[0059] In some embodiments, etching can be performed on an object with a complete etchable layer using a first type of gas and a second type of gas until a hole or trench with a high aspect ratio that meets the target is formed. In other embodiments, the etchable layer can be etched in two stages. In the first stage, shallow holes or trenches are etched through preliminary treatment, for example, by using a first type of gas 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 ensured. At this time, since the depth of the holes or trenches in the etchable layer is small, the etching gas can easily reach the bottom of the holes or trenches, and the problem shown in Figure 4 will not occur. In the second stage, a gas combination containing a second type of gas is used to continue etching the shallow holes or trenches until a hole or trench with a high aspect ratio that meets the target is formed, which ensures both a high etching rate and a good etched morphology.

[0060] The following describes the etching parameters and etching results of some examples using an overlapping layer of SiO2 and Si3N4 as the etching target, under a substrate temperature of -60℃.

[0061] Comparative Example 1 Gas types Flow rate (sccm) air pressure Aspect Ratio Central CD (nm) Bottom CD (nm) H 2 100 30 40±2 105±5 50±5 CF 4 150 NF 3 10 HBr 25 Ar 50

[0062] Taking the above situation as an example, under the condition that the first type of gas is CF4 and the auxiliary gases are H2, NF3, HBr and Ar, when the etching depth-to-width ratio is about 40, the CD difference between the middle and the bottom reaches 45nm, which obviously does not meet the requirements of the final result.

[0063] Example 1 Gas types Flow rate (sccm) air pressure Aspect Ratio Central CD (nm) Bottom CD (nm) H 2 100 30 50±2 100±5 60±5 CF 4 150 COF 2 10 NF 3 10 HBr 25 Ar 50

[0064] With other conditions remaining unchanged compared to "Comparative Example 1", an additional 10 sccm of COF2 was added as the second type of gas. It can be seen that even when the aspect ratio is increased to about 50, the CD difference between the middle and bottom is improved and reduced to about 40 nm.

[0065] Example 2 Gas types Flow rate (sccm) air pressure Aspect Ratio Central CD (nm) Bottom CD (nm) H 2 100 30 54±2 100±5 70±5 CF 4 150 COF 2 30 NF 3 10 HBr 25 Ar 50

[0066] With other conditions remaining unchanged relative to "Example 1", the flow rate of COF 2 was further increased to 30 sccm. It can be seen that even as the aspect ratio continued to increase, the CD difference between the middle and bottom continued to improve to 30 nm.

[0067] Example 3 Gas types Flow rate (sccm) air pressure Aspect Ratio Central CD (nm) Bottom CD (nm) H 2 100 30 55±2 100±5 80±5 CF 4 150 COF 2 70 NF 3 10 HBr 25 Ar 50

[0068] With other conditions remaining unchanged compared to "Example 1", the flow rate of COF 2 was further increased to 70 sccm. It can be seen that with the aspect ratio basically unchanged, the CD difference between the middle and bottom was further improved to 20 nm.

[0069] Example 4 Gas types Flow rate (sccm) air pressure Aspect Ratio Central CD (nm) Bottom CD (nm) H 2 100 30 55±2 100±5 85±5 CF 4 150 COF 2 100 NF 3 10 HBr 25 Ar 50

[0070] With other conditions remaining unchanged compared to "Example 1", the flow rate of COF 2 was further increased to 100 sccm. It can be seen that, with the aspect ratio basically unchanged, although the CD difference between the middle and bottom was further improved to about 15 nm, the benefit ratio was significantly reduced relative to the increased amount of COF 2.

[0071] Through comparative experiments, a small amount of COF2 can improve the morphology of structures with high aspect ratios. When the flow rate of COF2 is controlled at 20 sccm to 70 sccm, or the volume ratio is in the range of 1% to 30%, the improvement effect can maximize the benefit relative to the amount used.

[0072] The etching gases and combinations thereof, etching methods, and etching equipment involved in this invention include one or more of carbonyl halides, aldehyde halides, and carboxyl halides as reactant gases. These gases have a double bond combining carbon (C) and oxygen (O). Due to the presence of the O atom on this double bond, the other two halogen-containing groups or halogen atoms bonded to C are more easily released from the bond of C. When a certain radio frequency energy is applied, one of the halogen-containing groups or halogen atoms is released first, making the gas atoms into positively charged groups. The positively charged groups are more easily accelerated by the radio frequency electric field to the bottom of the high aspect ratio structure and react with the material to be etched at the bottom, thereby removing the bottom material. The lateral etching of the bottom by this group simultaneously achieves the consistency of the upper and lower feature dimensions (CD) of the high aspect ratio structure.

[0073] The second type of gas in this invention mainly includes halogen gases containing carbon-oxygen double bonds. Unlike the use of these gases as oxidizing gases, this invention innovatively discovers that this gas can easily separate one of the fluoride ions into a charged COF+ ion during plasma dissociation. When a biased radio frequency power supply is applied to the substrate to be etched, the charged COF+ group can reach the bottom of the etched hole or trench under the action of the biased radio frequency electric field, and release another fluoride ion upon contact with the bottom 220 material to participate in the etching reaction. This significantly improves the bottom CD of the hole or trench, reduces the difference between the bottom CD and the middle CD, and improves the verticality of the sidewalls of the etched hole or trench. Especially for etched structures with a high depth-to-width ratio, there is currently a problem where the bottom opening CD gradually decreases beyond a certain depth; the gas disclosed in this invention has unexpected effects.

[0074] The present invention also discloses a semiconductor device 100 for plasma etching, as shown in FIG7, specifically including a reaction chamber 10, which forms a reaction space inside for performing the plasma etching process; An air intake structure 30 is used to introduce process gas into the reaction space; a base 101 is used to support the substrate 103. The base 101 includes an electrostatic chuck 102, which can hold the substrate 103 by electrostatic attraction. An edge ring 20 is provided around the base 101, which can extend the range of the lower electrode and make the etching of the substrate 103 more uniform. A constraint ring 108 is also provided between the edge ring 20 and the side wall of the reaction chamber 10. A vacuum pump is provided below the constraint ring 108 to extract excess gas and reaction by-products in the reaction space. The constraint ring 108 can prevent plasma from entering the lower vacuum space and causing discharge and other phenomena that could damage the structure during the vacuuming process. A grounding ring 109 is connected to the bottom of the constraint ring 108 to realize a complete radio frequency circuit inside the reaction chamber 10. A first gas source 31 is connected to the 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 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, connected to the intake structure 30, and the auxiliary gas source contains one or more of O2, H2, NF3, HBr, and WF6.

[0075] The processor 40 controls the first gas source 31, the second gas source 32 and the auxiliary gas source 33 to introduce reactive gas into the reaction space to perform plasma etching process through electronic circuits and corresponding valves, flow controllers, etc.

[0076] It also includes an RF source, which is electrically connected to the base 101 through a matching unit. Specifically, it may include a high-frequency RF power supply 51 for generating plasma, which is electrically connected to the base 101 through a high-frequency RF matching unit 52; and a bias RF power supply 53 for controlling the direction of movement of charged groups, which is electrically connected to the base 101 through a bias RF matching unit 54.

[0077] In order to control the temperature of the substrate 103, the cooling circulation system 104 connected to the base 101, such as a cooling circulation pipeline with cooling fluid, can also have its parameters set by the controller 40 so that the temperature of the base 101 can be maintained at -80°C to 0°C during the etching process.

[0078] The plasma etching method disclosed in this invention is not limited to the plasma processing apparatus of the above embodiments, but can also be applied to other plasma processing apparatuses, which will not be elaborated here.

[0079] Although the present invention has been described in detail through the foregoing preferred embodiments, it should be understood that the foregoing description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the foregoing. Therefore, the scope of protection of the present invention should be defined by the appended claims.

[0080] 1: Substrate 10: Reaction Chamber 100: Semiconductor Equipment 101: Base 102: Electrostatic clamp 103: Substrate 104: Cooling Circulation System 108: Constraint Ring 109: Grounding ring 2: Layer to be etched 20: Edge ring 201: SiO2 layer 202: Si3N4 layer 210: Central 220: Bottom 3: Masking layer 30: Intake Structure 31: Primary Gas Source 32: Second gas source 33: Auxiliary gas source 4: Bend 40: Processor 5: Inclined hole 51: High-frequency radio frequency power supply 52: High-frequency radio frequency matching 53: Bias RF Power Supply 54: Bias RF Matching 6: Short hole 601, 602, 603, 604: Steps 7: Hole A, B, C, D: Etching gases E: Electric field

Claims

1. A plasma etching method, comprising the following steps: providing a substrate having a layer to be etched and a masking layer above the layer to be etched; introducing a first type of gas and a second type of gas to excite and form plasma etching of the layer to be etched, forming holes or trenches, wherein the aspect ratio of the holes or trenches is greater than 20; the first type of gas comprises one or more of fluorocarbons and hydrofluorocarbons; the second type of gas comprises one or more of carbonyl halides, aldehyde halides, and carboxyl halides, wherein the second type of gas, upon excitation, generates positively charged groups containing halogen groups or halogen atoms, wherein the positively charged groups, under the action of a biased radio frequency electric field, can reach the bottom of the holes or trenches, thereby removing the bottom material.

2. The plasma etching method as claimed in claim 1, wherein the carbonyl halide comprises one or a combination of two of the functional groups (CO)- and the functional groups F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, and CH2I-.

3. The plasma etching method as claimed in claim 1, wherein the aldehyde halide comprises a combination of a functional group (COH)- and a functional group of one of the following: F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-.

4. The plasma etching method as claimed in claim 1, wherein the carboxyl halide comprises a combination of a functional group (COOH)- and a functional group of one of the following: F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-.

5. The plasma etching method as claimed in claim 1, wherein the second type of gas comprises COF2.

6. The plasma etching method as claimed in claim 5, wherein the first type of gas comprises one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5.

7. The plasma etching method as claimed in claim 6, wherein the volume ratio of the first type of gas to the total gas volume is 30% to 70%; and the volume ratio of the second type of gas to the total gas volume is 1% to 30%.

8. The plasma etching method as claimed in claim 6, wherein the flow rate of the first type of gas is in the range of 10 sccm to 300 sccm; and the flow rate of the second type of gas is in the range of 5 sccm to 200 sccm.

9. The plasma etching method as claimed in claim 1, wherein an auxiliary gas is also introduced when the first type of gas and the second type of gas are introduced, the auxiliary gas comprising one or more of O2, H2, NF3, HBr, WF6, and Ar.

10. The plasma etching method as claimed in claim 9, wherein the volume ratio of the auxiliary gas to the total gas volume is 10% to 30%.

11. The plasma etching method as claimed in claim 9, wherein the flow rate of the auxiliary gas is in the range of 1 sccm to 200 sccm.

12. The plasma etching method as claimed in claim 1, wherein the layer to be etched comprises SiO2, Si3N4, polycrystalline silicon, or an alternating stack of any two of them.

13. The plasma etching method as claimed in claim 1, wherein the aspect ratio of the hole or trench is greater than 40.

14. The plasma etching method as claimed in claim 1, wherein when the plasma is excited, the frequency range of the radio frequency is 13 MHz to 200 MHz, and the power range is 1000 W to 30000 W.

15. The plasma etching method as claimed in claim 1, wherein the temperature range of the substrate during etching of the layer to be etched is -50°C to 100°C.

16. The plasma etching method as claimed in claim 1, wherein the gas pressure range during etching of the layer to be etched is 15mT to 40mT.

17. A gas combination for plasma etching, comprising: The first type of gas includes one or more of fluorocarbons and hydrofluorocarbons, wherein the first type of gas is one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5; the second type of gas includes one or more of carbonyl halides, aldehyde halides, and carboxyl halides, wherein the second type of gas can decompose in the plasma state into positively charged groups containing halogen groups or halogen atoms; the auxiliary gas includes one or more of O2, H2, NF3, HBr, WF6, and Ar.

18. The gas combination as described in claim 16, wherein, The carbonyl halide comprises a combination of one or two of the functional groups (CO)- and F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, and CH2I-; the aldehyde halide comprises a functional group (COH)- and F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, and CCl3-. The combination of one of CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, and CH2I-; the carboxyl halide includes a combination of the functional group (COOH)- and the functional groups F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, and CH2I-.

19. A plasma etching method, wherein, The process includes the following steps: providing an etchable object having a structure with holes or grooves; providing a process gas containing COF2 and exciting it into plasma, and continuing to etch the holes or grooves by applying a bias radio frequency.

20. The etching method of claim 19, wherein when the COF2 is excited into the plasma, the COF2 can decompose into COF+ groups and F-, the COF+ groups reaching the bottom of the hole or trench under the action of the bias radio frequency and chemically reacting with the etched object at the bottom of the hole or trench to generate volatile products.

21. The etching method of claim 20, wherein the COF+ group is etched laterally at the bottom of the hole or groove by a greater amount than it is etched laterally in the middle of the hole or groove.

22. The etching method as claimed in claim 19, wherein the etched object comprises SiO2, Si3N4, polycrystalline silicon, or an alternating stack of any two thereof.

23. The etching method as described in claim 19, wherein the frequency range of the bias radio frequency is 150 kHz to 4 MHz; and the power range is 500 W to 10 kW.

24. The etching method of claim 19, further comprising the steps of: providing a substrate having a layer to be etched and a masking layer above the layer to be etched, the layer to be etched being composed of alternating stacks of SiO2, Si3N4, or both; providing a process gas comprising one or more of CF4, CHF3, CH2F2, C2HF5, and C3HF5, and exciting it into the plasma to form the hole or trench on the substrate.

25. The etching method as described in claim 19, wherein the temperature range of the etched object is -30°C to 60°C.

26. The etching method as described in claim 19, wherein the aspect ratio of the hole or trench is greater than 20.

27. A gas for plasma etching, the gas comprising COF2, the COF2 being decomposed in a plasma state into COF+ groups and F-, the COF+ groups being capable of etching dielectric or semiconductor materials at the bottom of holes or trenches under biased radio frequency action.

28. The gas as claimed in claim 27, wherein the frequency range of the bias radio frequency is 150 kHz to 400 kHz; and the power range is 500 W to 10 kW.

29. The gas as claimed in claim 27, wherein the aspect ratio of the hole or groove is greater than 20.

30. The gas as claimed in claim 27, wherein the dielectric material comprises SiO2 or Si3N4; and the semiconductor material comprises polycrystalline silicon.

31. A semiconductor device, comprising: The reaction chamber forms a reaction space inside for performing plasma etching processes; An air intake structure is used to introduce process gas into the reaction space; A base for supporting a substrate; a first gas source connected to the gas inlet structure, the first gas source comprising one or more of fluorocarbons and hydrofluorocarbons; a second gas source connected to the gas inlet structure, the second gas source comprising one or more of carbonyl halides, aldehyde halides, and carboxyl halides, the second gas source being capable of decomposing in a plasma state into positively charged groups containing halogen groups or halogen atoms; and a processor that controls the first and second gas sources to introduce reactive gases into the reaction space to execute the plasma etching process.

32. The semiconductor device as claimed in claim 31 further includes a radio frequency source electrically connected to the base via a matching unit.

33. The semiconductor device of claim 31, wherein a cooling circulation system in communication with the substrate maintains the substrate at -80°C to 0°C during the etching process.

34. The semiconductor device of claim 31 further includes an auxiliary gas source connected to the gas inlet structure, the auxiliary gas source comprising one or more of O2, H2, NF3, HBr, WF6, and Ar.

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