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

Abstract

The invention provides a gas for plasma etching, a gas combination, an etching method and semiconductor equipment, which belong to the field of plasma etching, and are mainly characterized in that one or more of carbonyl halide, aldehyde halide and carboxyl halide are provided as process gases in the etching process to excite and form plasma, and the plasma is used as a plasma source. According to the method, the to-be-etched layer is etched, so that the problem of upper and lower inconsistency caused by large difference between the bottom etching rate and the middle etching rate when a high-aspect-ratio hole or groove is formed by etching to a certain degree is solved, the morphology of high-aspect-ratio etching is remarkably improved, the collimation is ensured, and the effectiveness of the semiconductor structure is improved.

Description

Technical Field

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

[0002] Micromachining of semiconductor substrates is a well-known technology that can be used to manufacture, for example, semiconductors, flat panel displays, light emitting diodes (LEDs), solar cells, etc. An important step in micromachining manufacturing is a plasma treatment process step, which is performed inside a reaction chamber into which a process gas is input. A radio frequency source is inductively and / or capacitively coupled to the reaction chamber to excite the process gas to form and maintain a plasma.

[0003] As the pursuit of Moore's Law continues, different process technologies and semiconductor structures have been invented. Whether it is a logic chip or a memory chip, more and more high aspect ratio structures need to be etched using plasma technology.

[0004] When the etching target is to form a high aspect ratio structure, it becomes increasingly difficult to continue etching the bottom of the structure. Even if etching reaches the predetermined depth, morphological deviations are likely to occur. 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, the conductive properties of subsequent devices will be further affected, and in severe cases, the device will fail. Summary 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 to form holes or grooves;

[0008] The first type of gas includes 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 functional group F-, Cl-, Br-, I-, CF 3 -,CHF 2 -,CH 2 F-,CCl 3 -,CHCl 2 -,CH2 Cl-,CBr 3 -,CHBr 2 -,CH 2 Br-,CI 3 -,CHI 2 -,CH 2 I-One or a combination of two.

[0011] Optionally, the aldehyde halide includes a functional group (COH)- and a functional group F-, Cl-, Br-, I-, CF 3 -,CHF 2 -,CH 2 F-,CCl 3 -,CHCl 2 -,CH 2 Cl-,CBr 3 -,CHBr 2 -,CH 2 Br-,CI 3 -,CHI 2 -,CH 2 I-A combination of one of the following.

[0012] Optionally, the carboxyl halide includes a functional group (COOH)- and a functional group F-, Cl-, Br-, I-, CF 3 -,CHF 2 -,CH 2 F-,CCl 3 -,CHCl 2 -,CH 2 Cl-,CBr 3 -,CHBr 2 -,CH 2 Br-,CI 3 -,CHI 2 -,CH 2 I-A combination of one of the following.

[0013] Optionally, the second type of gas comprises COF 2 .

[0014] Optionally, the first type of gas comprises CF 4 , CHF 3 , CH 2 F 2 , C 2 HF 5 , C 3 HF 5 One or more of .

[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 comprises O 2 , H 2 NF 3 , HBr, WF 6 , Ar or more.

[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 SiO 2 、Si 3 N 4 , polysilicon or alternating stacks of any two.

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

[0022] Optionally, when exciting the plasma, the frequency range of the radio frequency is: 13MHz-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 to 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 I gases include one or more of fluorocarbons and hydrofluorocarbons;

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

[0028] Auxiliary gas, including O 2 , H 2 NF 3 , HBr, WF6 , Ar or more.

[0029] Optionally, the carbonyl halide includes a functional group (CO)- and a functional group F-, Cl-, Br-, I-, CF 3 -,CHF 2 -,CH 2 F-,CCl 3 -,CHCl 2 -,CH 2 Cl-,CBr 3 -,CHBr 2 -,CH 2 Br-,CI 3 -,CHI 2 -,CH 2 I- or a combination of two thereof; the aldehyde halide includes a functional group (COH)- and a functional group F-, Cl-, Br-, I-, CF 3 -,CHF 2 -,CH 2 F-,CCl 3 -,CHCl 2 -,CH 2 Cl-,CBr 3 -,CHBr 2 -,CH 2 Br-,CI 3 -,CHI 2 -,CH 2 I-; the carboxyl halide includes a functional group (COOH)- and a functional group F-, Cl-, Br-, I-, CF 3 -,CHF 2 -,CH 2 F-,CCl 3 -,CHCl 2 -,CH 2 Cl-,CBr 3 -,CHBr 2 -,CH 2 Br-,CI 3 -,CHI 2 -,CH 2 I-A combination of one of the following.

[0030] Optionally, the first type of gas comprises CF 4 , CHF 3 , CH 2 F 2 , C 2 HF 5 , C 3 HF 5One or more of .

[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] Provide COF 2 The process gas is excited into plasma, and the holes or grooves are further etched by applying biased radio frequency.

[0034] Optionally, the COF 2 When excited into plasma, COF 2 It 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.

[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 of the COF+ group at the middle of the hole or groove.

[0036] Optionally, the etching object includes SiO 2 、Si 3 N 4 , 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 method further includes the following steps:

[0039] A substrate is provided, on which a layer to be etched and a mask layer above the layer to be etched are provided, wherein the layer to be etched is composed of SiO 2 、Si 3 N 4 or an alternating stack of the two;

[0040] Provides CF 4 , CHF 3 , CH 2 F 2 , C 2 HF 5 , C 3 HF 5 One or more process gases are added 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 to 60°C.

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

[0043] Furthermore, the present invention also provides a gas for plasma etching, the gas comprising COF 2 , the COF 2 It 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 trench 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 the groove is greater than 20.

[0046] Optionally, the dielectric material comprises SiO 2 or Si 3 N 4 ; The semiconductor material includes polycrystalline silicon.

[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 carrying a 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 also included, which is electrically connected to the base through a matcher.

[0055] Optionally, a cooling circulation system connected to 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 intake structure, and the auxiliary gas source contains O 2 , H 2 NF3 , HBr, WF 6 , Ar or more.

[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, a gas combination containing the gas, specifically one or more of carbonyl halides, aldehyde halides, and carboxyl halides. In high aspect ratio etching, the gas has a lower bond energy and is more likely to break one side to form a positively charged group, and is accelerated to the bottom of the high aspect ratio structure, and then contacts the material at the bottom to produce an etching reaction to generate volatile substances, thereby removing the material at the bottom, which is beneficial to deepening the depth of the hole or groove, and at the same time, it is also beneficial to lateral etching at the bottom, reducing the difference in the critical dimensions of 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, including a reaction chamber to provide a reaction space, two types of gases including one or more of carbonyl halides, aldehyde halides, and carboxyl halides, and one or more of fluorocarbons and hydrofluorocarbons enter the reaction space through an inlet structure, so that the processor runs to generate plasma and controls the charged particles or active groups to etch the substrate carried on the base. 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0059] Figure 1 A schematic diagram showing the chemical structure change when the etching gas is excited into plasma according to an embodiment of the present invention;

[0060] Figure 2 A schematic diagram showing chemical structure changes when an etching gas contacts an etching object according to an embodiment of the present invention;

[0061] Figure 3 Schematic diagrams showing the chemical structures of four embodiments of the present invention;

[0062] Figure 4 Schematic diagrams showing three common etching defects in the prior art;

[0063] Figure 5 The schematic diagram of etching morphology improvement achieved by using the gas of the present invention is shown;

[0064] Figure 6A schematic diagram of the etching method of the present invention is shown;

[0065] Figure 7 A schematic diagram of a semiconductor device for plasma etching according to the present invention is shown. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0067] In the field of plasma etching, as the demand for etching high aspect ratio structures becomes stronger and stronger, especially in the field of 3D-NAND, various etching defects have occurred when conventional gases or combinations are used for etching, mainly concentrated in the CD (critical dimension) of the etched high aspect ratio structure in each area does not meet expectations, which has brought many performance degradations or failures to the chip units formed after filling other materials in the high aspect ratio structure. In order to make the etched high aspect ratio structure meet expectations, the industry has explored many methods, but a plasma etching process involves multiple gases, each gas plays a different or overlapping role, multiple gases affect each other, and the effects of other parameters such as radio frequency, air pressure and temperature are coupled to each other. Adjusting one item will affect other items. Whether it is adjusting the type of gas, flow rate, or adjusting the value of other parameters, there are countless combinations, and it is very likely to change a variable. Although there is a slight improvement in one aspect, it introduces new problems in other aspects. Even for a certain type of gas, when changing other parameters, it will make this type of gas play a different role in the entire process. Due to the massive results of various combinations, the simple enumeration experiments without theoretical guidance cannot meet the urgent requirements of reality for high aspect ratio etching.

[0068] like Figure 1 Schematic diagram of chemical structure change when etching gas is excited into plasma, which is an exemplary diagram of the principle of the second type of gas of the present invention, with COF 2 For example, due to the presence of carbon-oxygen double bonds, the bond energy between carbon and fluorine is small. 2When the gas is excited to form plasma under RF energy of a certain power, the single bond between carbon and fluorine is more likely to break, and according to the currently coupled RF 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 RF 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 biased RF.

[0069] like Figure 2 The schematic diagram of the chemical structure change when the etching gas of an embodiment of the present invention contacts the etching object is shown. 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 fluorine ions, which react with the material to be etched to generate volatile substances for discharge, thereby achieving the purpose of continuous etching of the high aspect ratio structure.

[0070] In some other embodiments, the etching gas is not limited to COF 2 The same technical effect can be achieved for other compound gases with carbon-oxygen double bonds that can reduce the group bond energy and halogen elements that can etch the medium. Specifically, they can be carbonyl halides, aldehyde halides, and carboxyl halides. The carbonyl group has two low-energy single bonds, so the two single bonds can combine with one of the following functional groups: F-, Cl-, Br-, I-, CF 3 -,CHF 2 -,CH 2 F-,CCl 3 -,CHCl 2 -,CH 2 Cl-,CBr 3 -,CHBr 2 -,CH 2 Br-,CI 3 -,CHI 2 -,CH 2 I-; 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 2 F-,CCl 3 -,CHCl 2 -,CH 2 Cl-,CBr 3 -,CHBr 2 -,CH 2 Br-,CI 3 -,CHI 2 -,CH 2 I-. like Figure 3As shown, in some embodiments, the etching gas that can be selected is etching gas A: COF 2 ; Etching gas B: CF 3 CHO; Etching gas C: CO(CF 3 )2; Etching gas D: CF 3 COOH.

[0071] like Figure 4 The figure shows a schematic diagram of three common etching defects in the prior art. Usually, the substrate to be etched 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, so that the aspect ratio of the target structure to be etched, such as a hole or a groove, increases, some typical defects will appear. Taking the hole as an example, the curved hole 4 has a curved side wall 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 is that the amount of etching material that can reach the bottom is far less than that in the upper and middle parts, resulting in a wedge shape that is wide at the top and narrow at the bottom, which also destroys the vertical alignment of the ideal hole; the short hole 6 is that the etching material cannot reach the bottom and can only continue to etch in the horizontal direction, resulting in the inability to reach the aspect ratio of the ideal hole. The ideal hole situation is that 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, and finally a high aspect ratio hole that is consistent from top to bottom is obtained. The above defects are all caused by the inability of the etching material to etch vertically at a predetermined speed or degree target.

[0072] like Figure 5 The schematic diagram of the etching morphology improvement achieved by using the gas of the present invention is shown. The substrate to be etched includes a substrate 1, which can be made of Si in some embodiments. 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 mixture with doping, such as a single layer of SiO 2 、Si 3 N 4 or polysilicon, and SiO 2 and Si 3 N 4 Alternating stacking of SiO 2 and polysilicon, and optionally in some embodiments, the layer to be etched includes SiO 2 Layer 201, Si 3 N 4 The layers 202 are alternately stacked. Under the action of the downward electric field E formed by the biased radio frequency, 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 + +SiO 2→SiF 4 +CO 2

[0074] COF + +Si 3 N 4 →SiF 4 +CO 2 +FCN

[0075] Under the conditions of the reaction space, SiF 4 , CO 2 Both COF+ and FCN are gases that can be drawn out of hole 7, so as to continuously etch hole 7 to form a structure of hole 7 with a high aspect ratio. Since COF+ has good directionality controlled by the electric field, when the mask layer constrains the etching size, most of the COF+ that passes 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+. Since the middle part 210 is at a shallower position in 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 hole 7, and it is difficult for conventional etching gases to reach it through free diffusion, resulting in insufficient etching of the material at the bottom 220, that is, the size of the bottom 220 will be much smaller than the size defined by the mask. The COF+ used in the present invention 2 Most of the COF+ groups decomposed by the gas can be pushed to the bottom 220 by the electric field force, and the COF+ groups are likely to release another F ion when contacting the material of the bottom 220. The F ion reacts with the material of the bottom 220 to expand the lateral opening of the bottom, and no lateral etching occurs in the middle 210. Therefore, the lateral etching degree of COF+ in the bottom 220 is greater than that in the middle 220, avoiding the occurrence of Figure 4 The curved hole 4 and the inclined hole 5 are provided in the embodiment of the present invention.

[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 CF 4 , CHF 3 , CH 2 F 2 , C 2 HF 5 , C 3 HF 5 In some other embodiments, the gas combination may also include O2 , H 2 NF 3 , HBr, WF 6 , Ar or one or more of them are used as auxiliary gases.

[0077] The present invention also provides a plasma etching method, such as Figure 6 As shown, specifically including:

[0078] Step 601, providing a substrate. The substrate has a layer to be etched as an etching object, which can be SiO 2 、Si 3 N 4 Or the overlap of the two, the mask layer on the layer to be etched that constrains the etching result can 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 can have shallow holes or shallow grooves that have been etched by the previous step, or it can be a layer that has not been processed completely.

[0079] Step 602: introducing 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 a COF 2 , COCl 2 , COBr 2 , COI 2 , (CF 3 )-CO-H,(CF 3 )CO-F,(CF 3 )-CO-Cl,(CF 3 )-CO-OH,(CF 3 )-CO-(CF 3 ),(CF 3 )-CO-O-CO-(CF 3 ). The second type of gas is used to etch the layer to be etched until a hole or groove with a predetermined depth-to-width ratio is formed. The flow rate range of the second type of gas is: 10 sccm-200 sccm.

[0080] According to the selection of the etching object, the process gas may also include a first type of gas, such as one or more of fluorocarbons and hydrofluorocarbons. In some embodiments, the first type of gas may be CF 4 , CHF 3 , CH 2 F 2 , C 2 HF 5 , C 3 HF 5or a combination thereof. The first type of gas can play a role in etching the layer to be etched and protecting the sidewalls of the holes or grooves with high aspect ratios. The flow rate range of the first type of gas is: 10sccm-300sccm.

[0081] In other embodiments, the process gas may further include an auxiliary gas, such as an oxygen atomizer, to prevent excessive polymer deposition on the top of the hole or groove from clogging. 2 and NF 3 ; Improve the selectivity of the mask and the layer to be etched H 2 , strengthen the protection of the hole or groove side wall to prevent the side wall bending of HBr, WF 6 The flow rate range of the auxiliary gas is: 1sccm-200sccm.

[0082] In some embodiments, 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%. The volume ratio of the auxiliary gas to the total gas is 10%-30%. The first type of gas accounts for the majority of the total and plays a major role in etching. The second type of gas modifies the defective high aspect ratio structure after etching by the first type of gas, so that it has a CD that is as consistent as possible in the vertical direction.

[0083] Step 603, connect the radio frequency to excite the process gas into plasma. By selecting the 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 predetermined etching result under the gas combination conditions of the present invention, the frequency range of the radio frequency for generating plasma is: 13MHz-200MHz; the power range is: 1000w-30000w. The radio frequency for generating plasma needs to ensure that the gas can be ionized, but it cannot output too high a power to bring danger 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] In order to maintain the plasma and discharge the reaction byproducts in time, the reaction space needs to be continuously evacuated to maintain a certain pressure, which is in the range of 15mT-40mT. In order to ensure that the polymer generated during the process can protect the sidewalls of the holes or grooves from lateral over-etching and not accumulate too much to block the etching channel, the temperature of the substrate needs to be controlled at -50℃~100℃. In some embodiments, the temperature of the substrate is 0℃~10℃.

[0086] In some embodiments, the first type of gas and the second type of gas can be used to etch the 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, a shallow hole or groove is 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 hole or groove of the layer to be etched is small in depth, the etching gas can easily reach the bottom of the hole or groove, and no hole or groove will occur. Figure 4 In order to solve the problem shown in the figure, 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, thereby ensuring both a higher etching rate and a good etching morphology.

[0087] The following is SiO 2 、Si 3 N 4 The overlapping layer to be etched is the etching object, and the parameters and etching results of some embodiments are listed under the condition of a base temperature of -60°C.

[0088] Comparative Example 1

[0089]

[0090] Taking the above situation as an example, when the first type of gas is selected as CF 4 , the auxiliary gas is H 2 NF 3 Under the conditions of , 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 final result requirements.

[0091] Embodiment 1

[0092]

[0093] Compared with the "Comparative Example 1", the COF was increased by 10sccm while other conditions remained unchanged. 2As for the second type of gas, it can be seen that even when the aspect ratio increases to about 50, the CD difference between the middle and bottom is improved and reduced to about 40nm.

[0094] Embodiment 2

[0095]

[0096] Under the condition that other conditions remain unchanged relative to "Example 1", continue to increase COF 2 When the flow rate is 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 30nm.

[0097] Embodiment 3

[0098]

[0099] Under the condition that other conditions remain unchanged relative to "Example 1", continue to increase COF 2 When the flow rate is increased to 70sccm, it can be seen that the CD difference between the middle and bottom continues to improve to 20nm while the aspect ratio remains basically unchanged.

[0100] Embodiment 4

[0101]

[0102]

[0103] Under the condition that other conditions remain unchanged relative to "Example 1", continue to increase COF 2 When the flow rate is increased to 100 sccm, it can be seen that the CD difference between the middle and bottom is further improved to about 15nm while the aspect ratio remains basically unchanged. However, compared with the increased COF 2 The amount of revenue has been significantly reduced.

[0104] Through comparative tests, a small amount of COF 2 The improvement of the high aspect ratio structure morphology can be achieved, and when COF 2 When the flow rate is controlled within the range of 20sccm-70sccm, or the volume ratio is within the range of 1%-30%, the improvement effect can achieve maximum benefits relative to the dosage.

[0105] The present invention relates to an etching gas and a combination thereof, an etching method and an etching device, which contain one or more of carbonyl halides, aldehyde halides and carboxyl halides as reaction gases. The gas has 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 combined with C are more likely to break away from the bond of C. When a certain radio frequency energy is applied, one of the halogen-containing groups or halogen atoms is first separated to make the gas atom become a positively charged group. The positively charged group is more likely to be accelerated by the radio frequency electric field to the bottom of a high aspect ratio structure, and reacts with the material to be etched at the bottom to achieve the removal of the bottom material. The lateral etching of the bottom by the group simultaneously achieves the consistency of the upper and lower characteristic dimensions (CD) of the high aspect ratio structure.

[0106] The second type of gas of the present invention mainly includes halogen gas containing carbon-oxygen double bonds. Different from the use of this gas as an oxidizing gas, the present invention innovatively finds that this gas can easily separate one of the fluorine ions into charged COF+ during plasma dissociation. When a biased RF power supply is applied to the substrate to be etched, the charged COF+ group can reach the bottom of the etched hole or groove under the action of the biased RF electric field, and release another fluorine ion to participate in the etching reaction when it contacts the material at the bottom 220. The bottom CD of the hole or groove is greatly improved, the difference between the bottom CD and the middle CD is reduced, and the sidewall verticality of the etched hole or groove is improved. Especially for etching structures with a high aspect ratio, there is currently a problem that the bottom opening CD gradually decreases beyond a certain depth. The gas disclosed in the present invention has an unexpected effect.

[0107] The present invention also discloses a semiconductor device 100 for plasma etching, such as Figure 7 Specifically shown is a reaction chamber 10, in which a reaction space is formed for performing a plasma etching process; an air inlet structure 30, for introducing process gas into the reaction space; a base 101, for carrying a substrate 103, the base 101 includes an electrostatic chuck 102, which can clamp the substrate 103 by electrostatic suction, and an edge ring 20 is arranged around the base 101, which can expand the range of the lower electrode to make the etching of the substrate 103 more uniform, and a confinement ring 108 is also arranged between the edge ring 20 and the side wall of the reaction chamber 10, and an exhaust pump is arranged below the confinement ring 108 to extract the excess gas and reaction by-products in the reaction space, and the confinement ring 108 can prevent the plasma from entering the exhaust space below during the exhaust process to cause discharge and other phenomena causing structural damage, and a grounding ring 109 is connected to the confinement ring 108 below to realize a complete RF loop inside the reaction chamber 10;

[0108] A first gas source 31 is connected to the air 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 air 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 air 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 in the above-mentioned embodiment, but can also be applied to other plasma processing apparatuses, which will not be described in detail here.

[0113] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited 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 comprises COF2.

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, characterized in that: When etching the layer to be etched, the temperature range of the substrate is: -50°C to 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- or a combination of two thereof; the aldehyde halide comprises a functional group (COH)- and a functional group F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3- , a combination of one of CHCl2-, CH2Cl-, CBr3-, CHBr2-, CH2Br-, CI3-, CHI2-, CH2I-; the carboxyl halide includes a combination of a functional group (COOH)- and a functional group F-, Cl-, Br-, I-, CF3-, CHF2-, CH2F-, CCl3-, 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 to 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 communicated with 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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