Method for wafer surface treatment

Abstract

The present application provides a wafer surface treatment method, which comprises: introducing a reaction gas and a catalytic gas into a reaction chamber respectively, and controlling the partial pressure and temperature of at least one of the reaction gas and the catalytic gas, so that an etching reaction occurs at a specified density on the surface of a wafer to be treated; and performing a heat treatment on the wafer, so that the solid product generated by the etching reaction sublimates and is discharged from the reaction chamber with the gas flow. The wafer surface treatment method provided by the present application does not use plasma etching technology and does not require a mask plate, thereby avoiding damage to the wafer surface caused by plasma bombardment, and also enabling the etching process precision to be not limited by the size of the mask plate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor processing, in particular to a wafer surface processing method. BACKGROUND

[0002] When materials enter the nanometer scale, new properties are presented due to size effect, thus attracting more and more attention. With the development of semiconductor technology, the feature size is getting smaller and smaller, and integrated circuits have entered the nanometer era. At present, the formation of nanostructure in integrated circuits mainly relies on plasma etching. Under the restriction of photoresist or mask, nanostructure preparation can be carried out through anisotropic etching to meet the needs of different technology nodes. However, as the device geometry size becomes smaller and smaller, the device performance becomes more and more sensitive to the plasma damage of the material surface. In addition, the use of templates increases the process complexity. Therefore, it is necessary to provide an etching process to realize the preparation of nanostructure without the restriction of templates.

[0003] In the prior art, plasma dry etching and non-plasma gaseous dry etching are mainly used. Since the plasma dry etching uses plasma etching, it is inevitable that the surface will have a certain ion implantation, which will cause electrical damage to the nano device. The non-plasma gaseous dry etching is isotropic etching, which does not have directionality, so in order to obtain the desired wafer surface, a mask is still needed for etching. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art, and provide a wafer surface processing method without using plasma etching technology and without using a mask.

[0005] To achieve the above-mentioned purpose, the present application provides a wafer surface processing method, which comprises the following steps:

[0006] Respective reaction gas and catalytic gas are introduced into the reaction chamber, and the partial pressure and temperature of at least one of the reaction gas and the catalytic gas are regulated to make the etching reaction occur at the surface of the wafer to be processed with a specified density;

[0007] The wafer is subjected to heat treatment, so that the solid product generated by the etching reaction sublimates and is discharged from the reaction chamber with the gas flow.

[0008] Optionally, the introduction of the reaction gas and the catalytic gas into the reaction chamber comprises:

[0009] The reaction gas is introduced into the reaction chamber, and under the first process condition, the reaction gas is adsorbed on the surface of the wafer to be processed with a specified density;

[0010] The catalytic gas is introduced into the reaction chamber, and under the second process conditions, the catalytic gas catalyzes the reaction gas to perform an etching reaction with the surface to be treated.

[0011] Optionally, the first process conditions include:

[0012] The partial pressure of the reactant gas is greater than 0 Torr and less than or equal to 5 Torr, and the process temperature is greater than or equal to 90°C and less than or equal to 130°C.

[0013] Optionally, the first process conditions include:

[0014] The partial pressure of the reactant gas is greater than or equal to 0.2 Torr and less than or equal to 2 Torr, and the process temperature is greater than or equal to 100°C and less than or equal to 120°C.

[0015] Optionally, the first process conditions further include:

[0016] The intake flow rate is greater than 0 sccm and less than 400 sccm, and the process time is greater than or equal to 0.2s and less than or equal to 10s.

[0017] Optionally, the second process conditions are the same as the first process conditions.

[0018] Optionally, the reactant gas includes at least one of hydrogen fluoride, fluorine gas, and xenon fluoride gas.

[0019] Optionally, the catalytic gas includes at least one of ammonia, methanol, and water vapor.

[0020] Optionally, the heat treatment of the wafer includes:

[0021] A protective gas is introduced into the reaction chamber;

[0022] The wafer is heated to sublimate the solid products adhering to the surface of the wafer.

[0023] Turn on the vacuum device to extract the gas from the reaction chamber.

[0024] Optionally, the protective gas is nitrogen or an inert gas.

[0025] Beneficial effects of the embodiments of the present invention:

[0026] The wafer surface treatment method provided in this invention regulates the partial pressure and temperature of at least one of the reactant gas and catalytic gas to induce an etching reaction between the reactant gas molecules and the wafer surface material under the catalysis of the catalytic gas molecules. This etching reaction occurs at a specified density on the wafer surface to be treated, enabling wafer surface treatment without plasma etching technology or a mask, thus avoiding surface damage caused by plasma bombardment. Since each etching reaction involves a chemical reaction between individual (or clustered) gas molecules and the wafer surface to be treated, this wafer surface treatment method can achieve molecular-level etching, creating molecular-level pores on the wafer surface without being limited by mask size. Furthermore, the solid products generated by the etching reaction can be removed by heating the wafer to sublimate them, ensuring the cleanliness of the wafer surface. Attached Figure Description

[0027] Figure 1 This is a flowchart of the wafer surface treatment method provided in Embodiment 1 of the present invention;

[0028] Figure 2 This is a flowchart of step S1 in the wafer surface treatment method provided in Embodiment 1 of the present invention;

[0029] Figure 3 A simplified schematic diagram showing various adsorption scenarios of gas molecules on a wafer surface;

[0030] Figure 4 The image shows the etched morphology of a wafer surface processed using the wafer surface treatment method provided in Embodiment 1 of this invention.

[0031] Figure 5 This is a flowchart of step S2 in the wafer surface treatment method provided in Embodiment 1 of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solution of the present invention, the wafer surface treatment method provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0033] Example 1

[0034] Please refer to Figure 1 This embodiment provides a wafer surface treatment method, which specifically includes the following steps:

[0035] Step S1: Introduce the reaction gas and the catalytic gas into the reaction chamber respectively, and adjust the partial pressure and temperature of at least one of the reaction gas and the catalytic gas so that the etching reaction occurs at a specified density on the surface of the wafer to be processed.

[0036] Specifically, in step S1 above, "the etching reaction occurs at a specified density on the surface of the wafer to be processed" means that: the reactive gas molecules react with the wafer material under the catalysis of the catalytic gas molecules, and there is a certain distance between each (or each cluster) of gas molecules, so that there is also a corresponding distance between the multiple etching reactions occurring at multiple (or multiple clusters) of gas molecules, thereby etching multiple holes on the surface of the wafer to be processed; and since the size of the wafer material atoms participating in the aforementioned etching reaction is at the nanometer scale, such as Figure 4 Taking the silicon dioxide wafer shown as an example, the silicon atoms involved in the etching reaction are silicon atoms, and the diameter of silicon atoms is about 0.117 nm. Therefore, by causing gas molecules (clusters) that are a certain distance apart to undergo an etching reaction with the material on the surface of the wafer to be processed, nanopores of nanoscale size can be formed on the surface of the wafer to be processed.

[0037] Furthermore, the aforementioned "regulating the partial pressure and temperature of at least one of the reactant gas and catalytic gas" includes three regulation methods: regulating only the partial pressure and temperature of the reactant gas, regulating only the partial pressure and temperature of the catalytic gas, or regulating both the partial pressure and temperature of the reactant gas and the catalytic gas. The regulation step and the etching reaction can be performed separately, i.e., the reactant gas and catalytic gas are introduced sequentially, and at least one gas is regulated. Alternatively, the regulation step and the etching reaction can be performed simultaneously, i.e., the reactant gas and catalytic gas are introduced simultaneously, and at least one gas is regulated.

[0038] Step S2: Heat-treat the wafer so that the solid products generated by the etching reaction sublimate and are discharged from the reaction chamber with the gas flow.

[0039] Specifically, in step S2 above, the gas extraction device of the reaction chamber can be turned on during the sublimation of the solid product or after all the solid product has been sublimated into gas, so that the gas inside the reaction chamber can be extracted to the outside of the reaction chamber.

[0040] The wafer surface treatment method provided in this embodiment can control the partial pressure and temperature of at least one of the reactant gas and catalytic gas to cause an etching reaction between the reactant gas molecules and the wafer surface material under the catalysis of the catalytic gas molecules. This etching reaction occurs at a specified density on the surface of the wafer to be treated. Finally, the wafer is heat-treated to cause the solid products generated by the aforementioned catalytic reaction to sublimate and be discharged from the exhaust port of the reaction chamber. Therefore, the wafer surface treatment method provided in this embodiment can perform wafer surface treatment without using plasma etching technology or a mask, thereby avoiding wafer surface damage caused by plasma bombardment. Furthermore, it can greatly improve the precision of the etching process, achieving the formation of nanopores on the wafer surface.

[0041] In some embodiments, the aforementioned step S1 specifically includes the following steps:

[0042] Step S11: Introduce the reaction gas into the reaction chamber, and under the first process conditions, allow the reaction gas to be adsorbed onto the surface of the wafer to be treated at a specified density.

[0043] In step S11, "adsorption" refers to the process where reactant gas molecules collide with the wafer surface and generate intermolecular forces with the wafer surface material molecules, thus remaining on the wafer surface. Therefore, the adsorption in step S11 is a physical change, not a chemical change. Furthermore, the reaction chamber can be, for example, a rigid chamber with an inlet and an outlet, to facilitate the adjustment of the internal pressure of the chamber by introducing and discharging gas.

[0044] Step S12: Introduce catalytic gas into the reaction chamber, and under the second process conditions, allow the catalytic gas to catalyze the reaction gas and the surface to be treated to undergo an etching reaction.

[0045] Specifically, in step S12, when the catalytic gas or reactive gas diffuses to the wafer surface, the etching reaction will proceed spontaneously under the catalysis of the catalytic gas, so that the material atoms on the wafer surface are replaced and form solid products with the reactive gas, thereby completing the etching. Moreover, since the reactive gas molecules participating in the aforementioned etching reaction are adsorbed on the wafer surface, and the catalytic gas molecules diffuse from the gas inlet of the reaction chamber to the wafer surface, the difference between the momentum of the reactive gas molecules in the direction perpendicular to the wafer surface and the momentum in the direction parallel to the wafer surface is 0. Therefore, the aforementioned etching reaction is isotropic etching, that is, the etching reaction exhibits the same etching rate on different crystallographic planes.

[0046] Figure 3The diagram illustrates various adsorption states of gas molecules on the wafer surface, specifically including: A. “Sufficient adsorption” state, B. “Under-adsorption” state, and C. “Severely under-adsorption” state. The "sufficient adsorption" state refers to a state where the density of gas molecules adsorbed on the wafer surface is extremely high, allowing the etching reaction to occur across the entire wafer surface, resulting in almost no change in the surface roughness after etching. The "severely under-adsorption" state refers to a state where the number and density of gas molecules adsorbed on the wafer surface are extremely low, allowing the etching reaction to occur only at each (or cluster of) gas molecules adsorbed on the wafer surface. Because the number and density of gas molecules are extremely low, the surface roughness of the wafer will not change significantly after etching in this state. The "under-adsorption" state refers to a state where the density of gas molecules adsorbed on the wafer surface is a preset molecular density, which is between the density of gas molecules adsorbed on the wafer surface in the "sufficient adsorption" and "severely under-adsorption" states, allowing the etching reaction to occur only at each (or cluster of) gas molecules adsorbed on the wafer surface, thereby forming multiple pores distributed on the wafer surface. Specifically, the "adsorption" state is the "under-adsorption" state described in step S11 above, where the reaction gas is adsorbed at a specified density on the surface of the wafer to be processed.

[0047] To ensure that the density and number of nanopores meet design and production requirements, the density and number of reactive gas molecules adsorbed on the wafer surface can be adjusted by regulating the process conditions in steps S11 and S12. Specifically, in some embodiments, the first process conditions include: a partial pressure of the reactive gas greater than 0 Torr and less than or equal to 5 Torr; and a process temperature greater than or equal to 90°C and less than or equal to 130°C. Preferably, the first process conditions include: a partial pressure of the reactive gas greater than or equal to 0.2 Torr and less than or equal to 2 Torr; and a process temperature greater than or equal to 100°C and less than or equal to 120°C.

[0048] The aforementioned "partial pressure" refers to the pressure exerted by a component in a gas mixture when it occupies the same volume of the mixture at the same temperature. According to the kinetic theory of gases, gas pressure is generated by the frequent collisions of numerous molecules with the container walls. Therefore, by adjusting the partial pressure of the gas, the probability of gas molecules colliding with the wafer can be adjusted, thereby regulating the number and density of gas molecules adsorbed on the wafer surface. It is easy to understand that the higher the partial pressure, the greater the number and density of gas molecules adsorbed on the wafer surface. Therefore, the number and density of gas molecules adsorbed on the wafer surface can be controlled by adjusting the partial pressure of the reactant gases. Similarly, according to the kinetic theory of gases, the average kinetic energy of molecules is proportional to thermodynamic temperature. Therefore, it is easy to understand that the higher the temperature inside the reaction chamber, the easier it is for gas molecules already adsorbed on the wafer surface to detach, thus reducing the number and density of gas molecules adsorbed on the wafer surface. Therefore, by adjusting the partial pressure and temperature of the gas inside the reaction chamber, the number and density of gas molecules adsorbed on the wafer surface can be adjusted to obtain the desired gas molecule adsorption state.

[0049] In addition, in order to ensure that the number of nanopores meets the actual production needs, the number of gas molecules adsorbed on the wafer surface can be adjusted by adjusting the air intake flow rate and the duration of step S11, i.e., the adsorption duration. Specifically, in some embodiments, the first process conditions mentioned above also include: the air intake flow rate is greater than 0 sccm and less than 400 sccm; the process time is greater than or equal to 0.2 s and less than or equal to 10 s.

[0050] Furthermore, to ensure that the size of each nanopore meets actual production needs, the etching depth can be adjusted by regulating the duration of step S12, i.e., the etching duration. It should be noted that since the aforementioned etching reaction is isotropic, the "etching depth" refers to both the amount of etching perpendicular to the wafer surface and the amount of etching parallel to the wafer surface. Therefore, the longer the preset etching duration, the larger the diameter and depth of each nanopore; however, the etching reaction process should not be too long to avoid excessive etching depth or the inability to perform subsequent heat treatment steps in a timely manner after the etching reaction, thus avoiding wasted process time. Specifically, in some embodiments, the second process conditions are the same as the first process conditions, for example: the partial pressure of the catalytic gas is greater than 0 Torr and less than or equal to 5 Torr; the process temperature is greater than or equal to 90°C and less than or equal to 130°C; preferably, the partial pressure of the catalytic gas is greater than or equal to 0.2 Torr and less than or equal to 2 Torr; the process temperature is greater than or equal to 100°C and less than or equal to 120°C; the inlet flow rate of the catalytic gas is greater than 0 sccm and less than 400 sccm; and the duration of step S12 is greater than or equal to 0.2 s and less than or equal to 10 s.

[0051] It should be noted that since the etching reaction requires the participation of a catalytic gas to occur, in step S11, whether the reactive gas or the catalytic gas is introduced into the reaction chamber, the gas molecules will only be adsorbed onto the surface of the wafer, and no chemical reaction will occur. Therefore, when performing steps S11 and S12, the reactive gas can be introduced first, followed by the catalytic gas, or vice versa.

[0052] In some embodiments, such as Figure 5 As shown, the above-mentioned heat treatment step for the wafer, namely step S2, specifically includes the following steps:

[0053] Step S21: Introduce protective gas into the reaction chamber;

[0054] In some embodiments, the protective gas is nitrogen or an inert gas to prevent chemical reactions with the wafer or other gases while regulating the internal pressure of the reaction chamber;

[0055] Step S22: Heat the wafer to sublimate the solid products adhering to the wafer surface;

[0056] Step S23: Turn on the vacuum device to extract the gas from the reaction chamber.

[0057] The wafer surface treatment method provided in this embodiment utilizes the adsorption properties of reactive gas molecules and catalytic gas molecules on the wafer surface. By introducing reactive and catalytic gases into the reaction chamber, the reactive and catalytic gas molecules are adsorbed onto the wafer surface. Under the catalysis of the catalytic gas molecules, an etching reaction occurs between the reactive gas molecules and the wafer surface material. This allows for wafer surface treatment without using plasma etching technology or a mask, thus avoiding surface damage caused by plasma bombardment and ensuring that the etching process precision is not limited by mask size. Furthermore, the solid products generated during the etching reaction can be removed by heating the wafer to sublimate them, thereby ensuring the cleanliness of the wafer surface.

[0058] Example 2

[0059] Based on the wafer surface treatment method provided in Example 1, this example provides a process for forming nanopores on the wafer surface, wherein the wafer material is silicon dioxide (SiO2), the etching gas is hydrogen fluoride gas (HF), and the catalyst gas is ammonia gas (NH3). The corresponding chemical reaction formula for the etching reaction is as follows:

[0060]

[0061] As can be seen from the above formula, fluoride ions (F -The silicon atoms in the solid silicon dioxide were replaced, forming silicon tetrafluoride (SiF4) gas, which completed the etching of the silicon dioxide wafer surface.

[0062] However, since fluorine in hydrogen fluoride gas does not exist in ionic form, no chemical reaction occurs when hydrogen fluoride gas molecules are adsorbed onto the surface of a silicon dioxide wafer. When ammonia gas comes into contact with the hydrogen fluoride on the wafer surface, it provides a certain number of electrons, causing the fluorine in the hydrogen fluoride gas to undergo a displacement reaction with the silicon dioxide after gaining electrons. Specifically, the above etching reaction can be decomposed into the following two reaction processes:

[0063] HF+NH3+SiO2→(NH4)2SiF6+H2O;

[0064]

[0065] It can be seen that ammonia, as a catalyst for the above etching reaction, was not consumed; and the solid product ammonium hexafluorosilicate ((NH4)2SiF6) sublimated into gas after heating, and could be extracted by the gas extraction device of the reaction chamber.

[0066] Specifically, the above process includes the following steps:

[0067] S01. Turn on the heat source to maintain the internal temperature of the reaction chamber at the first process temperature; in some embodiments, the value of the first process temperature is greater than or equal to 90°C and less than or equal to 130°C; preferably, the value of the first process temperature is greater than or equal to 110°C and less than or equal to 120°C.

[0068] S02. Hydrogen fluoride gas is introduced into the reaction chamber until the partial pressure of the hydrogen fluoride gas in the reaction chamber reaches the first partial pressure; in some embodiments, the value of the first partial pressure is greater than 0 Torr and less than or equal to 5 Torr.

[0069] S03. Maintain a preset adsorption time to allow hydrogen fluoride gas to be adsorbed on the surface of the wafer; in some embodiments, the preset adsorption time is, for example, greater than or equal to 0.2s and less than or equal to 10s.

[0070] S04. Adjust the internal temperature of the reaction chamber to the second process temperature; in some embodiments, the value of the second process temperature is greater than or equal to 90°C and less than or equal to 130°C.

[0071] S05. Ammonia gas is introduced into the reaction chamber until the partial pressure of ammonia gas in the reaction chamber reaches the second partial pressure; in some embodiments, the value of the second partial pressure is greater than 0 Torr and less than or equal to 5 Torr.

[0072] S06. Maintain a preset etching time to allow ammonia gas to be adsorbed on the wafer surface and catalyze the etching reaction between hydrogen fluoride gas and the wafer; in some embodiments, the preset etching time is greater than or equal to 0.2s and less than or equal to 10s.

[0073] S07. Introduce nitrogen gas into the reaction chamber;

[0074] S08. Heat the wafer to sublimate the ammonium hexafluorosilicate adhering to the wafer surface;

[0075] S09. Turn on the vacuum device to extract the gas from the reaction chamber; process ends.

[0076] It should be noted that the wafer surface treatment method provided in Example 1 can be applied not only to silicon dioxide wafers, but also to silicon wafers or silicon nitride wafers; correspondingly, the reaction gas can also be fluorine gas (F2), xenon fluoride gas (XeF2), or a mixture of both, and the catalytic gas can also be methanol gas, water vapor, or a mixture of both. Specifically, the gas partial pressure and gas temperature can be adjusted accordingly based on the gas type.

[0077] The process for forming nanopores on the wafer surface provided in this embodiment adjusts the density and number of reactant gas molecules adsorbed on the wafer surface by regulating the partial pressure and temperature of the reactant gas, thereby enabling the fabrication of nanopore structures on the silicon dioxide wafer surface.

[0078] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A wafer surface treatment method, characterized in that, Includes the following steps: A reactive gas and a catalytic gas are introduced into a reaction chamber, and the partial pressure and temperature of at least one of the reactive gas and the catalytic gas are controlled to cause the etching reaction to occur at a specified density on the surface of the wafer to be processed; including: The reaction gas is introduced into the reaction chamber. Under the first process conditions, the reaction gas is adsorbed at a specified density on the surface to be treated of the wafer, so that the reaction gas on the surface to be treated reaches a sub-adsorption state, wherein the reaction gas is adsorbed on the surface to be treated in the form of gaseous molecules under the action of intermolecular forces. The catalytic gas is introduced into the reaction chamber, and under the second process conditions, the catalytic gas catalyzes the reaction gas to perform an etching reaction with the surface to be treated. The wafer is heat-treated so that the solid products generated by the etching reaction sublimate and are discharged from the reaction chamber with the gas flow.

2. The wafer surface treatment method according to claim 1, characterized in that, The first process conditions include: The partial pressure of the reactant gas is greater than 0 Torr and less than or equal to 5 Torr, and the process temperature is greater than or equal to 90°C and less than or equal to 130°C.

3. The wafer surface treatment method according to claim 2, characterized in that, The first process conditions include: The partial pressure of the reactant gas is greater than or equal to 0.2 Torr and less than or equal to 2 Torr, and the process temperature is greater than or equal to 100°C and less than or equal to 120°C.

4. The wafer surface treatment method according to claim 2 or 3, characterized in that, The first process conditions also include: The intake air flow rate is greater than 0 sccm and less than 400 sccm, and the process time is greater than or equal to 0.2s and less than or equal to 10s.

5. The wafer surface treatment method according to claim 1, characterized in that, The second process conditions are the same as the first process conditions.

6. The wafer surface treatment method according to claim 1, characterized in that, The reactant gas includes at least one of hydrogen fluoride, fluorine, and xenon fluoride.

7. The wafer surface treatment method according to claim 1, characterized in that, The catalytic gas includes at least one of ammonia, methanol, and water vapor.

8. The wafer surface treatment method according to claim 1, characterized in that, The heat treatment of the wafer includes: A protective gas is introduced into the reaction chamber; The wafer is heated to sublimate the solid products adhering to the surface of the wafer. Turn on the vacuum device to extract the gas from the reaction chamber.

9. The wafer surface treatment method according to claim 8, characterized in that, The protective gas is nitrogen or an inert gas.

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