Plasma enhanced atomic layer etching method

Abstract

The invention discloses a plasma enhanced atomic layer etching method, relates to the technical field of atomic layer etching, and is used for ensuring that the roughness of an etched surface is relatively low while rapid etching is ensured, so that the etching precision and the yield are improved. The plasma enhanced atomic layer etching method comprises the following steps: firstly, introducing plasma of a modified precursor into an etching chamber in which a to-be-etched object is placed, so as to perform adsorption modification on the surface of the to-be-etched object, and forming a modified layer on the surface of the to-be-etched object. The vacuum degree in the etching chamber is background vacuum, and the temperature is preset temperature. And next, argon plasma is introduced into the etching chamber to remove the modified layer. And then, repeating the operation until the actual removal thickness of the to-be-etched object is equal to the target thickness.

Description

Technical Field

[0001] The invention relates to the technical field of atomic layer etching, and in particular to a plasma enhanced atomic layer etching method. Background Art

[0002] Pattern transfer technology refers to the process of selectively removing materials not masked by the resist film by chemical and / or physical means, thereby obtaining a pattern that is completely consistent with the resist film. It is widely used in the integrated circuit manufacturing process.

[0003] However, existing etching technologies cannot ensure fast etching while maintaining low surface roughness, which is not conducive to improving etching accuracy and yield. Summary of the invention

[0004] The object of the present invention is to provide a plasma enhanced atomic layer etching method for ensuring rapid etching while ensuring low roughness of the etched surface, thereby improving etching accuracy and yield.

[0005] In order to achieve the above-mentioned object, the present invention provides a plasma enhanced atomic layer etching method, which comprises: first, introducing plasma of a modified precursor into an etching chamber in which an object to be etched is placed, so as to adsorb and modify the surface of the object to be etched, and form a modified layer on the surface of the object to be etched. The vacuum degree in the etching chamber is a background vacuum and the temperature is a preset temperature. Next, argon plasma is introduced into the etching chamber to remove the modified layer. Then, the above operation is repeated until the actual removal thickness of the object to be etched is equal to the target thickness.

[0006] When the above technical solution is adopted, since the gas activity can be significantly increased after the gas is ionized by radio frequency, the plasma of the modified precursor is introduced into the etching chamber where the object to be etched is placed, so that the plasma of the modified precursor can react quickly with the object to be etched, thereby improving the adsorption modification efficiency; at the same time, etching can be performed at a lower temperature, thereby solving the problem of increasing the etching temperature to improve the etching efficiency in the prior art, resulting in the object to be etched being adversely affected by the high temperature, thereby improving the etching yield.

[0007] In addition, the plasma enhanced atomic layer etching method provided by the present invention realizes the self-limiting chemical modification step of the top atomic layer of the object to be etched and the step of etching to remove the chemically modified area through the plasma adsorption modification of the modified precursor and the cyclic etching process of argon plasma bombardment in an orderly alternating operation mode, and realizes the etching of a single atomic layer, and each step is self-limiting, so that good surface roughness and steepness can be maintained during the etching process, effectively reducing the degree of surface damage to the remaining part of the object to be etched after etching, and at the same time having high selectivity, which can improve the etching accuracy. It has great potential for etching thin films in some high-precision semiconductor devices, and has good application prospects in integrated circuit fields such as FinFET, GAA, 3D NAND, etc., which is conducive to promoting the semiconductor device structure to move towards smaller critical dimensions.

[0008] As a possible implementation scheme, the material of the object to be etched includes silicon and / or silicon dioxide.

[0009] As a possible implementation solution,

[0010] In the case where the material of the object to be etched includes silicon, the modified precursor includes at least one of CF4, SF6, CHF3, HBr, C4F8 and Cl2; and / or,

[0011] In the case where the material of the object to be etched includes silicon dioxide, the modified precursor includes at least one of CF4, CHF3 and C4F8.

[0012] As a possible implementation scheme, the gas flow rate of the plasma of the modified precursor is greater than or equal to 1 sccm and less than or equal to 10 sccm.

[0013] As a possible implementation scheme, the plasma of the modified precursor is introduced for a time greater than or equal to 5 s and less than or equal to 10 s.

[0014] As a possible implementation scheme, the plasma of the modified precursor is generated by inductively coupled plasma, and the upper radio frequency power is greater than or equal to 70W and less than or equal to 200W.

[0015] As a possible implementation scheme, the gas flow rate of the argon plasma is greater than or equal to 10 sccm and less than or equal to 50 sccm.

[0016] As a possible implementation scheme, the argon plasma is introduced for a time greater than or equal to 5 seconds and less than or equal to 30 seconds.

[0017] As a possible implementation scheme, the argon plasma is generated by inductively coupled plasma, and the upper RF power is greater than or equal to 70W and less than or equal to 200W, and the lower RF power is greater than or equal to 5W and less than or equal to 20W.

[0018] As a possible implementation scheme, the sample stage on which the object to be etched is placed in the etching chamber is cooled to -10°C to 15°C by a coolant, and the pressure in the etching chamber is greater than or equal to 1×10 -3 Torr, and less than or equal to 1×10 -2 Torr.

[0019] As a possible implementation scheme, after introducing the plasma of the modified precursor into the etching chamber where the object to be etched is placed, and before introducing the argon plasma into the etching chamber, the plasma enhanced atomic layer etching method further includes: introducing a purge gas into the etching chamber. And / or,

[0020] After introducing argon plasma into the etching chamber and before introducing plasma of a modified precursor into the etching chamber where the object to be etched is placed, the plasma enhanced atomic layer etching method further includes: introducing a purge gas into the etching chamber.

[0021] As a possible implementation scheme, the purge gas is argon, the gas flow rate of the purge gas is greater than or equal to 10 sccm and less than or equal to 100 sccm, and the introduction time of the purge gas is greater than or equal to 10 s and greater than or equal to 60 s. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0023] Figure 1 A flow chart of a plasma enhanced atomic layer etching method provided by an embodiment of the present invention;

[0024] Figure 2 The AFM step morphology of Example 1 provided in the embodiment of the present invention;

[0025] Figure 3 The AFM channel morphology of Example 1 provided in the embodiment of the present invention;

[0026] Figure 4 The SEM cross-sectional morphology of Example 2 provided in the embodiment of the present invention;

[0027] Figure 5 The AFM channel morphology of Example 2 provided in the embodiment of the present invention;

[0028] Figure 6 The AFM step morphology of Example 3 provided in the embodiment of the present invention;

[0029] Figure 7 The AFM channel morphology of Example 3 provided in the embodiments of the present invention. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0031] Various structural schematic diagrams according to embodiments of the present disclosure are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may further design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0032] In the context of the present disclosure, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intermediate layer / element between them. In addition, if a layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "under" the other layer / element. In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0034] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] Pattern transfer technology refers to the process of selectively removing materials not masked by the resist film by chemical and / or physical means, thereby obtaining a pattern that is completely consistent with the resist film. In the integrated circuit manufacturing process, the required pattern is copied on the resist film by mask registration, exposure and development of the object to be etched, or the pattern is directly drawn on the resist film with an electron beam, and then the pattern is accurately transferred to the dielectric film (such as silicon oxide, silicon nitride, polysilicon) or metal film (such as aluminum and its alloys) under the resist film to produce the required thin layer pattern.

[0036] In addition, etching technology is mainly divided into dry etching and wet etching. Among them, the dry etching method mainly uses reactive gas and plasma for etching, and is mainly used for micro-nano scale etching; while the wet etching method mainly uses chemical reagents and etched materials to chemically react for etching, and is generally only used in larger sizes. In addition, high-quality pattern transfer technology is essential for manufacturing today's advanced microelectronic devices. As key processes are reduced to levels below 10nm and new devices use ultra-thin 2D materials, the demand for atomic-scale fidelity and higher etching accuracy is also growing. In order to achieve rapid etching, the existing plasma etching must expose the surface of the object to be etched to chemical radicals and be bombarded by high-energy positive ions to form volatile compounds. The ion energy commonly used in the inductively coupled plasma method is ten times higher than the chemical bond strength of the solid, resulting in increased surface roughness after etching. At the same time, as the size of devices gradually decreases, more and more high-precision etching methods are needed; but the existing etching technology cannot ensure low roughness while ensuring rapid etching. Furthermore, the processing temperature of the existing etching technology is relatively high, which can easily damage the object to be etched.

[0037] In order to solve the above technical problems, an embodiment of the present invention provides a plasma enhanced atomic layer etching method. Among them, in the plasma enhanced atomic layer etching method provided by the embodiment of the present invention, the plasma of the modified precursor is introduced into the etching chamber where the object to be etched is placed to improve the adsorption modification efficiency. At the same time, etching can be performed at a lower temperature to prevent high-temperature etching from damaging the object to be etched, thereby improving the etching yield. In addition, the plasma enhanced atomic layer etching method provided by the embodiment of the present invention realizes the self-limiting chemical modification step of the top atomic layer of the object to be etched and the step of etching to remove the chemically modified area through the orderly alternating operation mode of the plasma adsorption modification of the modified precursor and the cyclic etching process of argon plasma bombardment, which can improve the etching accuracy.

[0038] Specifically, if Figure 1 As shown, an embodiment of the present invention provides a plasma enhanced atomic layer etching method. The plasma enhanced atomic layer etching method comprises the following steps:

[0039] First, a plasma of a modified precursor is introduced into an etching chamber where an object to be etched is placed, so as to adsorb and modify the surface of the object to be etched and form a modified layer on the surface of the object to be etched. The vacuum degree in the etching chamber is a background vacuum and the temperature is a preset temperature.

[0040] In actual application, the object to be etched may be a substrate in any semiconductor device. The material of the substrate may be determined according to the actual application scenario and is not specifically limited here.

[0041] Exemplarily, the material of the object to be etched may include silicon and / or silicon dioxide. For example, the object to be etched may be a substrate whose material is only silicon; or, the object to be etched may be a base whose material is only silicon dioxide; or, the object to be etched may be a silicon-on-insulator substrate whose material includes silicon and silicon dioxide, or a silicon substrate with a silicon dioxide dielectric film layer formed thereon.

[0042] Secondly, the embodiment of the present invention does not specifically limit the lateral range and depth of the etching area of ​​the etching object. It can be that the entire top layer of the object to be etched is etched, that is, the lateral profile of the etching area coincides with the top profile of the object to be etched; it can also be that the partial top area of ​​the object to be etched is etched, and the lateral profile of the etching area is located within the top profile of the object to be etched. In this case, a resist film is also formed on the top of the object to be etched, and the area exposed by the resist film is the etching area.

[0043] In addition, in the actual application process, before the plasma of the modified precursor is introduced into the etching chamber where the object to be etched is placed, the etching chamber is evacuated to a background vacuum. At this time, the pressure of the etching chamber can be determined according to the material of the object to be etched and actual needs, as long as it can be applied to the plasma enhanced atomic layer etching method provided in the embodiment of the present invention.

[0044] For example, the pressure in the etching chamber may be greater than or equal to 1×10 -3 Torr, and less than or equal to 1×10 - 1 Torr. For example, the pressure in the etching chamber can be 1×10 -3 Torr, 3×10 -3 Torr, 4×10 -3 Torr, 5×10 - 3 Torr, 6×10 -3 Torr or 1×10 -1 Torr et al. In this case, the pressure in the etching chamber affects the plasma concentration of the modified precursor subsequently introduced into the etching chamber. Based on this, the pressure in the etching chamber is within the above range, which can prevent the concentration of the plasma of the modified precursor subsequently introduced into the etching chamber from being low due to the low pressure in the etching chamber, thereby ensuring a higher adsorption modification efficiency. At the same time, it can also prevent the low pressure in the etching chamber from being unfavorable for the RF source to be started. In addition, it can also prevent the high pressure in the etching chamber from affecting the surface flatness and uniformity of the etching area of ​​the object to be etched after adsorption modification, thereby ensuring that the surface roughness of the etching area of ​​the object to be etched after etching is low, thereby improving the etching accuracy; there is no need to maintain a high chamber pressure, thereby reducing the difficulty of etching.

[0045] As for adjusting the temperature in the etching chamber to a specific range of preset temperatures before introducing the plasma of the modified precursor into the etching chamber where the object to be etched is placed, it can be determined according to the material of the object to be etched and actual needs, and is not specifically limited here.

[0046] For the above-mentioned modified precursor, the type of the modified precursor, the ionization method of the modified precursor, and the gas flow rate and introduction time of the plasma of the modified precursor can be determined according to the material of the object to be etched and actual needs.

[0047] Exemplarily, the modified precursor may include at least one of CF4, SF6, CHF3, HBr, C4F8 and Cl2. For example, when the material of the etching area of ​​the object to be etched is silicon, the modified precursor may be at least one of CF4, SF6, CHF3, HBr, C4F8 and Cl2. When the material of the etching area of ​​the object to be etched is silicon dioxide, the modified precursor may be at least one of CF4, CHF3 and C4F8.

[0048] For example, the plasma of the modified precursor may be generated by inductively coupled plasma or capacitively coupled plasma, wherein the plasma of the modified precursor generated by the inductively coupled plasma has a higher ionization rate than that by the capacitively coupled plasma, and is more conducive to improving the adsorption modification efficiency.

[0049] Among them, the working parameters of the plasma for generating the modified precursor can be determined according to the ionization method and the actual application scenario, and are not specifically limited here. For example, in the case of generating the plasma of the modified precursor by inductively coupled plasma, the upper RF power can be greater than or equal to 70W and less than or equal to 200W. For example: the upper RF power can be 70W, 100W, 130W, 160W or 200W, etc. Specifically, the upper RF power is within the above range, which can prevent the low ionization rate due to the small upper RF power, and ensure a higher adsorption modification efficiency; it can also prevent the above-mentioned RF power from affecting the surface flatness of the etched area after adsorption modification, reduce the roughness of the surface of the etched area after adsorption modification, and improve the etching accuracy.

[0050] Exemplarily, the gas flow rate of the plasma of the modified precursor may be greater than or equal to 1 sccm and less than or equal to 10 sccm. For example, the gas flow rate of the plasma of the modified precursor may be 1 sccm, 2 sccm, 4 sccm, 6 sccm, 8 sccm or 10 sccm, etc. In this case, the gas flow rate of the plasma of the modified precursor is within the above range, which can prevent the plasma density of the modified precursor from being small and unstable ignition due to the small gas flow rate of the plasma of the modified precursor; it can also prevent the chamber pressure from increasing due to the large gas flow rate of the plasma of the modified precursor, thereby preventing the ion flux density from decreasing, thereby ensuring a higher adsorption modification efficiency.

[0051] Exemplarily, the plasma of the modified precursor may be introduced for a time greater than or equal to 5s and less than or equal to 10s. For example, the plasma of the modified precursor may be introduced for a time of 5s, 6s, 7s, 8s, 9s or 10s, etc. In the above case, the plasma of the modified precursor is introduced within the above range, which can prevent the RF ignition from being unstable due to the short plasma of the modified precursor and the surface of the etching area of ​​the object to be etched from not being fully reacted during this operation. While improving the etching efficiency, it can ensure that each part of the etching area can fully react in each cycle operation and the reaction depth is roughly the same, thereby improving the etching accuracy. In addition, it can also prevent the plasma of the modified precursor from being introduced for a long time, which may lead to a large amount of consumables used, which is beneficial to controlling the etching cost.

[0052] As a possible implementation scheme, after introducing the plasma of the modified precursor into the etching chamber where the object to be etched is placed, and before introducing the argon plasma into the etching chamber, the above-mentioned plasma enhanced atomic layer etching method may also include the step of introducing a purge gas into the etching chamber. In this case, the excess plasma of the modified precursor in the etching chamber may be purged out of the etching chamber to ensure that the proportion of the plasma of the modified precursor in one alternating reaction meets the requirements of the preset scheme, thereby improving the etching accuracy. At the same time, after the first alternation, the excess reaction by-products in the etching chamber may be purged out of the etching chamber to prevent the reaction by-products from affecting the etching accuracy.

[0053] Specifically, the type, time, and gas flow rate of the purge gas introduced into the etching chamber can be determined according to the actual application scenario and are not specifically limited here.

[0054] Exemplarily, the purge gas may be a protective gas such as nitrogen, helium, and argon.

[0055] Exemplarily, the gas flow rate of the purge gas may be greater than or equal to 10 sccm and less than or equal to 100 sccm, and the purge gas introduction time may be greater than or equal to 10 s and greater than or equal to 60 s. For example, the gas flow rate of the purge gas may be 10 sccm, 30 sccm, 50 sccm, 70 sccm, 90 sccm or 100 sccm, and the purge gas introduction time may be 10 s, 20 s, 30 s, 40 s, 50 s or 60 s, etc.

[0056] Next, argon plasma is introduced into the etching chamber to remove the modified layer.

[0057] In the actual application process, after the modified layer is formed, it is necessary to introduce argon plasma into the etching chamber, and under the physical bombardment of the argon plasma, the modified layer is removed to achieve the etching of a single atomic layer in this cycle. In this case, the generation method, gas flow rate, and introduction time of argon plasma can be determined according to the requirements for the etching rate in the actual application scenario, as long as they can be applied to the plasma-enhanced atomic layer etching method provided in the embodiment of the present invention.

[0058] For example, the argon plasma may be generated by inductively coupled plasma or capacitively coupled plasma, wherein the argon plasma generated by the inductively coupled plasma has a higher ionization rate than the capacitively coupled plasma, and is more conducive to improving the etching efficiency.

[0059] Among them, the working parameters for generating argon plasma can be determined according to the ionization method and the actual application scenario, and are not specifically limited here. Exemplarily, when the argon plasma is generated by inductively coupled plasma, the upper RF power is greater than or equal to 70W and less than or equal to 200W, and the lower RF power is greater than or equal to 5W and less than or equal to 20W. For example: when the argon plasma is generated by inductively coupled plasma, the upper RF power can be 70W, 100W, 130W, 160W, 190W or 200W, etc., and the lower RF power can be 5W, 10W, 15W or 20W, etc. In this case, the upper RF power is within the above range, which can prevent the low ionization rate due to the small upper RF power and ensure a higher etching rate; it can also prevent excessive etching after removing the modified layer due to the large RF power; and it will increase the temperature inside the etching chamber and reduce the impact of high temperature on the object to be etched. As for the lower RF power, when the lower RF power is within the above range, it can prevent the etching rate from being reduced due to the lower RF power and improve the etching efficiency; it can also prevent the abnormal resist film pattern and the strong argon plasma bombardment caused by the higher lower RF power, thereby ensuring higher etching accuracy and reducing the surface roughness of the etching area, preventing the object to be etched from being over-etched and improving the etching yield.

[0060] Exemplarily, the gas flow rate of the argon plasma may be greater than or equal to 10 sccm and less than or equal to 50 sccm. For example, the gas flow rate of the argon plasma may be 10 sccm, 20 sccm, 30 sccm, 40 sccm or 50 sccm. In this case, the gas flow rate of the argon plasma is within the above range, which can prevent the argon plasma density from being low due to the low gas flow rate of the argon plasma, and can also prevent the chamber pressure from being increased due to the high gas flow rate of the argon plasma, thereby preventing the ion flux density from being decreased, thereby ensuring a higher etching efficiency.

[0061] Exemplarily, the introduction time of the argon plasma can be greater than or equal to 5s and less than or equal to 30s. For example, the introduction time of the argon plasma can be 5s, 10s, 15s, 20s, 25s or 30s, etc. In the above case, the introduction time of the argon plasma is within the above range, which can prevent the modified layer on the surface of the etched area of ​​the object to be etched from being not completely removed during the operation due to the short introduction time of the argon plasma, and can also ensure that all parts of the etched area can fully contact and react with the plasma of the modified precursor in the next cycle operation, thereby improving the etching efficiency. In addition, it can also prevent the introduction time of the argon plasma from being long and affecting the surface flatness of the etched area, which is conducive to reducing the surface roughness of the etched area after etching.

[0062] Then, the above operation is repeated until the actual removal thickness of the object to be etched is equal to the target thickness.

[0063] In actual application, the number of repetitions of the above operation can be determined according to the single removal thickness of the object to be etched after each cycle and the size relationship between the target thickness, which is not specifically limited here.

[0064] As a possible implementation scheme, after introducing argon plasma into the etching chamber, and before introducing the plasma of the modified precursor into the etching chamber where the object to be etched is placed in the next cycle operation, the above-mentioned plasma enhanced atomic layer etching method also includes: introducing a purge gas into the etching chamber. In this case, the excess argon plasma in the etching chamber can be purged out of the etching chamber to ensure that the proportion of argon plasma in an alternating reaction meets the requirements of the preset scheme and ensure that the surface of the etched area has a lower surface roughness. At the same time, after the first alternation, the excess reaction by-products in the etching chamber can be purged out of the etching chamber to prevent the reaction by-products from affecting the etching accuracy.

[0065] Specifically, the type, time and gas flow rate of the purge gas mentioned above can be found in the previous text and will not be described in detail here.

[0066] As a possible implementation scheme, during the etching process, the sample stage on which the object to be etched is placed in the etching chamber is cooled by a coolant to further reduce the influence of temperature on the object to be etched and improve the yield. Specifically, the temperature at which the sample stage is cooled by the coolant can be determined according to actual needs, as long as it can be applied to the plasma enhanced atomic layer etching method provided in the embodiment of the present invention.

[0067] Exemplarily, the sample stage with the object to be etched placed in the etching chamber is cooled to -10°C to 15°C by the coolant. For example, the sample stage with the object to be etched placed in the etching chamber is cooled to -10°C, -5°C, 0°C, 5°C, 10°C or 15°C by the coolant.

[0068] It can be seen from the above manufacturing process that since the gas activity can be significantly increased after being ionized by radio frequency, the plasma of the modified precursor is introduced into the etching chamber where the object to be etched is placed, so that the plasma of the modified precursor and the object to be etched are adsorbed in an orderly manner, and multi-layer modification will not occur due to high temperature; at the same time, etching can be carried out at a lower temperature, thereby solving the problem in the prior art that the etching temperature is increased to improve the etching efficiency, resulting in the object to be etched being adversely affected by the high temperature, thereby improving the etching yield.

[0069] In addition, the plasma enhanced atomic layer etching method provided by the embodiment of the present invention realizes the self-limiting chemical modification step of the top atomic layer of the object to be etched and the step of etching to remove the chemically modified area through the orderly alternating operation mode of the plasma adsorption modification of the modified precursor and the cyclic etching process of argon plasma bombardment, and realizes the etching of a single atomic layer, and each step is self-limiting, so that during the etching process, a good surface roughness and steepness can be maintained, and the degree of surface damage to the remaining part of the object to be etched after etching is effectively reduced, and at the same time, it has high selectivity and can improve the etching accuracy. It has great potential for the etching of thin films in some high-precision semiconductor devices, and has good application prospects in the fields of integrated circuits such as FinFET, GAA, 3D NAND, etc., which is conducive to promoting the semiconductor device structure to move towards smaller critical dimensions.

[0070] The present invention also provides the following specific embodiments to further illustrate the plasma enhanced atomic layer etching method of the present invention. The specific operation steps are as follows:

[0071] Embodiment 1:

[0072] Step 1: Place the silicon wafer in the etching chamber and use a molecular pump to evacuate the etching chamber to the required background vacuum of 5×10 -3 Torr, and the temperature in the etching chamber was controlled to be maintained at 10°C.

[0073] Step 2: After the etching chamber environment is stable, introduce SF6 with a gas flow rate of 5sccm and Ar with a gas flow rate of 50sccm, and the introduction time is 5s. In addition, the introduced gas is ionized by inductively coupled plasma, and its upper injection power is 90W. Then, Ar gas is introduced into the etching chamber for 30s. Next, Ar plasma is introduced into the etching chamber for 10s. Ionization is performed by inductively coupled plasma, with an upper RF power of 90W and a lower RF power of 7W to remove the modified layer. Then, Ar gas is introduced into the etching chamber for 30s.

[0074] Step 3: Repeat 10 cycles to end the etching process.

[0075] like Figure 2 and Figure 3 As shown, the AFM measurement results show that the step height is 21.94 nm, the etching rate is 2.19 nm / cycle, the root roughness after the etching process is Rq=0.709 nm, and the average roughness Ra=0.460 nm.

[0076] Embodiment 2:

[0077] Step 1: Place the silicon wafer in the etching chamber and use a molecular pump to evacuate the etching chamber to the required background vacuum of 5×10 -3 Torr, and the temperature in the etching chamber was controlled to be maintained at 10°C.

[0078] Step 2: After the etching chamber environment is stable, introduce CHF3 with a gas flow rate of 5sccm and Ar with a gas flow rate of 50sccm, and the introduction time is 5s. In addition, the introduced gas is ionized by inductively coupled plasma, and the upper injection power is 150W. Then, Ar gas is introduced into the etching chamber for 10s. Next, Ar plasma is introduced into the etching chamber for 10s. Ionization is performed by inductively coupled plasma, with an upper RF power of 150W and a lower RF power of 7W to remove the modified layer. Then, Ar gas is introduced into the etching chamber for 30s.

[0079] Step 3: Repeat 60 cycles to end the etching process.

[0080] like Figure 4 and Figure 5 As shown, from the SEM measurement results, it can be seen that the step height after etching is 122.8nm, and the calculated etching rate is 2.03nm / cycle; from the AFM measurement results, the root roughness Rq after the etching process is 0.957nm, and the average roughness Ra is 0.749nm.

[0081] Embodiment 3:

[0082] Step 1: Place the silicon wafer in the etching chamber and use a molecular pump to evacuate the etching chamber to the required background vacuum of 5×10 -3 Torr, heat the sample stage with the silicon wafer and keep the sample stage temperature at 50°C.

[0083] Step 2: After the etching chamber environment is stable, introduce Cl2 with a gas flow rate of 5sccm and Ar with a gas flow rate of 50sccm, and the introduction time is 5s. In addition, the introduced gas is ionized by inductively coupled plasma, and its upper injection power is 50W. Then, Ar gas is introduced into the etching chamber for 30s. Next, 10sAr plasma is introduced into the etching chamber. Ionization is performed by inductively coupled plasma, with an upper RF power of 200W and a lower RF power of 7W to remove the modified layer. Then, Ar gas is introduced into the etching chamber for 30s.

[0084] Step 3: Repeat 11 cycles to end the etching process.

[0085] like Figure 6 and Figure 7 As shown, from the AFM measurement results, it can be seen that the step height after etching is 24.34nm, and the etching rate can be calculated to be 2.21nm / cycle. The root roughness after the etching process is Rq=0.416nm, and the average roughness Ra=0.317nm.

[0086] In the above description, the technical details of the patterning and etching of each layer are not described in detail. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. of desired shapes. In addition, in order to form the same structure, those skilled in the art can also design methods that are not completely the same as the methods described above. In addition, although the various embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage.

[0087] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, a person skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A plasma enhanced atomic layer etching method, characterized in that: include: Introducing plasma of a modified precursor into an etching chamber where an object to be etched is placed, so as to adsorb and modify the surface of the object to be etched and form a modified layer on the surface of the object to be etched; the vacuum degree in the etching chamber is a background vacuum and the temperature is a preset temperature; Introducing argon plasma into the etching chamber to remove the modified layer; The above operation is repeated until the actual removal thickness of the object to be etched is equal to the target thickness.

2. The plasma enhanced atomic layer etching method according to claim 1, characterized in that: The material of the object to be etched includes silicon and / or silicon dioxide.

3. The plasma enhanced atomic layer etching method according to claim 2, characterized in that: In the case where the material of the object to be etched includes silicon, the modified precursor includes at least one of CF4, SF6, CHF3, HBr, C4F8 and Cl2; and / or, In the case where the material of the object to be etched includes silicon dioxide, the modified precursor includes at least one of CF4, CHF3 and C4F8.

4. The plasma enhanced atomic layer etching method according to claim 1, characterized in that: The gas flow rate of the plasma of the modified precursor is greater than or equal to 1 sccm and less than or equal to 10 sccm; and / or, The plasma of the modified precursor is introduced for a time greater than or equal to 5 seconds and less than or equal to 10 seconds.

5. The plasma enhanced atomic layer etching method according to claim 1, characterized in that: The plasma of the modified precursor is generated by inductively coupled plasma, and the upper radio frequency power is greater than or equal to 70W and less than or equal to 200W.

6. The plasma enhanced atomic layer etching method according to claim 1, characterized in that: The gas flow rate of the argon plasma is greater than or equal to 10 sccm and less than or equal to 50 sccm; and / or, The argon plasma is introduced for a time greater than or equal to 5 seconds and less than or equal to 30 seconds.

7. The plasma enhanced atomic layer etching method according to claim 1, characterized in that: The argon plasma is generated by inductively coupled plasma, and the upper radio frequency power is greater than or equal to 70W and less than or equal to 200W, and the lower radio frequency power is greater than or equal to 5W and less than or equal to 20W.

8. The plasma enhanced atomic layer etching method according to claim 1, characterized in that: The sample stage in the etching chamber where the object to be etched is placed is cooled to -10°C to 15°C by a coolant, and the pressure in the etching chamber is greater than or equal to 1×10 -3 Torr, and less than or equal to 1×10 -2 Torr.

9. The plasma enhanced atomic layer etching method according to any one of claims 1 to 8, characterized in that: After introducing the plasma of the modified precursor into the etching chamber where the object to be etched is placed, and before introducing the argon plasma into the etching chamber, the plasma enhanced atomic layer etching method further comprises: introducing a purge gas into the etching chamber; and / or, After introducing argon plasma into the etching chamber and before introducing plasma of a modified precursor into the etching chamber where the object to be etched is placed, the plasma enhanced atomic layer etching method further includes: introducing a purge gas into the etching chamber.

10. The plasma enhanced atomic layer etching method according to claim 9, characterized in that: The purge gas is argon gas, the gas flow rate of the purge gas is greater than or equal to 10 sccm and less than or equal to 100 sccm, and the introduction time of the purge gas is greater than or equal to 10 s and greater than or equal to 60 s.

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