Patent Description:
The present disclosure relates to the field of semiconductor production technology, and more particularly, to a method for processing a semiconductor structure.

With the rapid development of the semiconductor industry in recent years, high-aspect-ratio (HAR) nanostructures have been widely used in various fields. As nanometer devices are increasingly pursued in technology, the feature size of chips continues to shrink in a production process, and the entire semiconductor production technology is still developing towards further miniaturization of critical dimensions.

After patterns such as trenches are etched in semiconductor structures such as a Dynamic Random Access Memory (DRAM), steps of wet cleaning and drying are generally required to remove the byproduct generated in the etching process or the residual polymers generated after the etching process. However, in the processes of the wet cleaning and the drying, a capillary action may cause the collapse or deformation of the patterns. The smaller the sizes of the trenches formed by etching are, the greater the tension of the fluid likely appearing in the semiconductor structure is. There are three factors generally causing the collapse of the patterns: Laplace pressure; adhesive force; and electrostatic force, Van der Waals' force, and hydrogen-bond interaction. In an advanced DRAM production process, the collapse of the patterns may seriously affect the yield and productivity rate of the chips, and increasingly becomes a key factor in determining the success or failure of the DRAM production process. Particularly, a HAR Shallow Trench Isolation (STI) structure has more severe collapse or deformation of the patterns due to the capillary action in the wet cleaning. Therefore, it is of vital importance to eliminate or reduce the risk of the collapse of the pattern in the production of semiconductor devices such as the DARM.

However, in the more advanced DRAM production process, with the size of the structure becoming smaller and requirement for HAR, a great challenge is posed to the stability of the liquid environment during cleaning. Therefore, the surface effect of the cleaning liquid becomes a major factor affecting production quality. In some embodiments, the wet cleaning may cause the collapse of the patterns due to the capillary action on the pattern structures. The occurrence of the collapse of the patterns may be reduced by means of surface finishing of the HAR structure. However, this treatment method may lead to other negative effects, such as the super-hydrophobic effect of the HAR structure. This super-hydrophobic effect may prevent the aqueous solution from penetrating into the structure, resulting in a decrease in the effect of wet cleaning. In addition, taking the STI production as an example, a surface finishing agent is added after the wet cleaning before the drying process, which can effectively prevent the occurrence of pattern collapse. However, the surface finishing agent may remain at the bottom of the STI structure, which may cause abnormalities of the semiconductor devices.

D1 (<CIT>) discloses a surface treatment method for a semiconductor device having capacitor patterns, comprising: providing a substrate where a plurality of projected capacitor patterns are formed in a mold insulation layer; removing the mold insulation layer by using a wet etch solution; rinsing the substrate from which the mold insulation layer is removed with deionized water; treating the substrate with an SC-<NUM> (NHOH+HO+OH) solution; rinsing the treated substrate with deionized water; forming a hydrophobic coating layer on a surface of each of plurality of the projected capacitor patterns; rinsing the substrate where the hydrophobic coating layer is formed with deionized water; and drying the substrate, wherein the hydrophobic coating layer is formed using a coating agent that includes phosphate having more than one hydrocarbon group, phosphonate having more than one hydrocarbon group, or a mixture thereof.

D2 (<CIT>) discloses a chemical solution for forming a water-repellent protective film on a wafer, which is a chemical solution containing a water-repellent-protective-film-forming agent for forming the water-repellent protective film, at the time of cleaning the wafer which has a finely uneven pattern at its surface and contains at least at a part of a surface of a recessed portion of the uneven pattern at least one kind of matter selected from the group consisting of titanium, titanium nitride, tungsten, aluminum, copper, tin, tantalum nitride, ruthenium and silicon, at least on the surface of the recessed portion, the chemical solution being characterized in that the water-repellent-protective-film-forming agent is a water-insoluble surfactant.

D3 (<CIT>) discloses a method of processing a wafer used in fabricating semiconductor devices, said method comprising: forming high aspect ratio features in a silicon based layer on the wafer; making sidewalls of the features more hydrophobic; performing wet processing of the wafer; and subsequently drying the wafer.

D4 (<CIT>) discloses a method for forming a semiconductor device, comprising: forming a silicon-hydrogen (Si-H) terminated surface on a silicon structure that includes patterned features by exposing the silicon structure to a hydrogen fluoride (HF) containing solution; removing the HF containing solution via a deionized (DI) water rinse; forming a solvent on the Si-H terminated surface on the silicon structure; and performing a surface modification via hydrosilylation by exposing the Si-H terminated surface to an alkene and/or an alkyne.

D5 (<CIT>) discloses a substrate processing method comprising: a liquid processing process of supplying a processing liquid to a substrate having a surface on which a pattern having a plurality of convex portions is formed; a drying process of removing the processing liquid existing on the surface of the substrate to dry the substrate; and a separating process of separating a sticking portion between adjacent ones of the convex portions after the drying process.

D6 (<CIT>) discloses an improved pre-gate cleaning technique that results in a smoother wafer surface.

D7 (<CIT>) discloses a method for processing an inner wall surface of a micro vacancy.

D8 (<CIT>) discloses a method of treating a semiconductor substrate.

D9 (<CIT>) discloses a method for preparing active regions.

Therefore, it is a technical problem to be solved urgently at present how to reduce the occurrence of pattern collapse or deformation in the wet cleaning process of the semiconductor structures to improve the performance of the semiconductor structures and increase the yield of the semiconductor devices.

The present disclosure provides a method for processing a semiconductor structure. This method is used for solving the problem of pattern collapse or deformation prone to occur in a cleaning process of the semiconductor structure, to improve the performance of the semiconductor structure and increase the yield of the semiconductor devices.

To solve the above problem, the present disclosure provides a method for processing a semiconductor structure, and the invention is set out in the appended set of claims. By using the method for processing a semiconductor structure provided by the present disclosure, a transition layer configured to reduce the capillary force exerted by a fluid on the etched structures is formed on the inner walls of the etched structures such that the probability of collapse or deformation of the etched structures is reduced in the subsequent process of drying the etched structures. Furthermore, the transition layer covering the inner walls of the etched structures is removed after being dried, so the attraction force between the patterns of the etched structures is broken such that the etched structures deformed in the previous drying process is restored to its original state, thereby further reducing the probability of collapse or deformation of the etched structures, improving the performance of the semiconductor structure, and increasing the productivity and the yield of the semiconductor devices.

A specific embodiment of a method for processing a semiconductor structure provided by the present disclosure is described in detail below with reference to the accompanying drawings.

This specific embodiment provides a method for processing a semiconductor structure. <FIG> is a flowchart of the method for processing a semiconductor structure according to this specific embodiment of the present disclosure. <FIG> are schematic diagrams showing major technologies during processing a semiconductor structure according to this specific embodiment of the present disclosure. <FIG> are schematic sectional views of a processing chambers during processing a semiconductor structure according to this specific embodiment of the present disclosure. As shown in <FIG>, -<FIG>, and <FIG>, the method for processing a semiconductor structure provided by this specific embodiment includes following steps.

Step S11, providing a semiconductor structure, wherein the semiconductor structure comprises a substrate <NUM> and a plurality of etched structures <NUM> arranged on the surface area of the substrate <NUM>, as shown in <FIG>.

In this specific embodiment, the etched structures <NUM> may be any structures formed on the substrate <NUM> by means of a dry etching process. In some embodiments, the etched structures are trenches, and the number of the trenches arranged on the surface area of the substrate is more than one.

The ratio of the depth H of the trench to the minimum width W of the trench is greater than <NUM>.

In some embodiments, the trenches are arranged in parallel on the surface area of the substrate <NUM>.

The width D of the pattern line between two adjacent trenches is less than <NUM>.

In some embodiments, the etched structures <NUM> may be trenches such as shallow trench isolation (STI) extending from the surface of the substrate <NUM> into the substrate <NUM> along the direction (i.e., the Y-axis direction in <FIG>) perpendicular to the substrate <NUM>. In semiconductor production processes, trenches with higher aspect ratio (HAR) are more likely to collapse or deform during the cleaning process. The method for processing a semiconductor structure provided in this embodiment is more effective in preventing the collapse or deformation of the trenches with higher aspect ratio during the cleaning process. <FIG> shows five trenches arranged in parallel on the surface area of the substrate <NUM> (i.e., the X-axis direction in <FIG>). In practical use, the specific number of the trenches may be determined by the person skilled in the art according to actual needs. The aspect ratios of the plurality of trenches may be same or different. The term "a plurality of" in this specific embodiment means two or more.

In some embodiments, the step of providing a semiconductor structure includes:.

In some embodiments, cleaning the semiconductor structure comprises the following specific steps:.

In some embodiments, processing the semiconductor structure by means of the plasma ashing process comprises the following specific steps:
performing the ashing process on the surface of the semiconductor structure by means of plasmonized oxygen to remove the polymer residues generated after the trenches are formed by the etching.

In some embodiments, performing the ashing process on the surface of the semiconductor structure by means of the plasmonized oxygen comprises the following specific step:
simultaneously introducing the plasmonized oxygen and a mixed gas composed of hydrogen and nitrogen, wherein the ratio of the flow of the oxygen to the flow of the mixed gas is <NUM>:<NUM>. The volume ratio of the hydrogen in the mixed gas composed of the hydrogen and the nitrogen is <NUM>%.

In some embodiments, the surface of the substrate <NUM> has a mask layer, such as a first mask layer <NUM> covering the surface of the substrate <NUM> and a second mask layer <NUM> covering the surface of the first mask layer <NUM> in <FIG>. The mask layer has a mask pattern. After the substrate <NUM> is etched by dry etching process or other etching processes along the mask pattern in the mask layer to form the trenches, some polymers (i.e., the polymer residues) may remain inside the trenches. Some by-products and pollutants may also be generated by the etching reaction between the etchant and the substrate <NUM>. To avoid causing adverse effects on subsequent processes, in this specific embodiment, after etching the trenches, the polymer residues are first removed by the plasma ashing process, and then the by-products and the pollutants are removed by wet cleaning process, to make sure the inside of the trenches and the surface of the substrate clear. The material of the first mask layer <NUM> may be silicon oxide, and the material of the second mask layer <NUM> may be silicon nitride.

In the plasma ashing process, the flow rate of the oxygen is <NUM>,<NUM>/min-<NUM>,<NUM>/min, the flow rate of the mixed gas composed of the hydrogen and the nitrogen (the volume ratio of the hydrogen is <NUM>%) is <NUM>/min~<NUM>,<NUM>/min, the temperature is <NUM>~<NUM>, the duration is <NUM>~<NUM>, the pressure in the processing chamber is of <NUM> mtorr~<NUM>,<NUM> mtorr, and the radio frequency (RF) power is of <NUM>,<NUM> W~<NUM>,<NUM> W. In wet cleaning process, the cleaning agent may be diluted HF (DHF), wherein the volume ratio of the HF (<NUM>% HF liquid) to the deionized water is <NUM>: (<NUM>~<NUM>), the duration is <NUM>~<NUM>, the temperature is <NUM>~<NUM>, and the rotation speed of the support platform is 100rpm~<NUM>,000rpm.

For example, after the trenches are etched, the substrate <NUM> with the trenches is placed onto the support platform <NUM> in the processing chamber <NUM> as shown in <FIG>. In the plasma ashing process, a spray head <NUM> sprays the plasmonized oxygen to the substrate <NUM> at a flow rate of <NUM>,<NUM>/min, and simultaneously sprays the plasmonized mixed gas (the mixed gas is composed of the hydrogen and the nitrogen, and the volume ratio of the hydrogen is <NUM>%) to the substrate at the flow rate of <NUM>,<NUM>/min, the temperature in the processing chamber <NUM> is maintained at <NUM>, the pressure is <NUM>,200mtorr, the RF power is <NUM>,400W, and the duration is <NUM>. After the plasma ashing process is completed, in wet cleaning process, the DHF (<NUM>:<NUM>) is used as the cleaning agent, as shown in <FIG>. The cleaning agent is sprayed onto the surface of the substrate <NUM> through the spray head <NUM>, meanwhile the support platform <NUM> rotates at the speed of <NUM>,<NUM> rpm, the temperature is room temperature, and the duration is <NUM>.

Step S12, forming a transition layer <NUM>, the transition layer <NUM> at least covering the inner walls of the etched structures <NUM>, where the transition layer <NUM> is configured to reduce a capillary force exerted by a fluid on the etched structures <NUM>, and to serve as a sacrificial layer configured to repair a collapsed structure, as shown in <FIG>.

According to the invention, forming a transition layer <NUM>, the transition layer <NUM> at least covering the inner walls of the etched structures <NUM> comprises the following specific step:
oxidizing the semiconductor structure to form an oxide layer, the oxide layer at least covering the inner walls of the trenches, wherein the oxide layer is the transition layer <NUM>.

In some embodiments, oxidizing the semiconductor structure comprises the following specific step:
processing the semiconductor structure by means of an oxidizing liquid, wherein the oxidizing liquid at least fills up the trenches, as shown in <FIG>.

The oxidizing liquid is an ozone deionized aqueous solution (DIO<NUM>) or a mixed solution (i.e., APM solution) composed of ammonia water and hydrogen peroxide solution.

In some embodiments, processing the semiconductor structure by means of the oxidizing liquid comprises the following step:
spraying the oxidizing liquid to the surface of the semiconductor structure being spinning to rinse the semiconductor structure.

In some embodiments, the oxide layer has a thickness of 2Å to 12Å.

In some embodiments, after the semiconductor structure is cleaned, as shown in <FIG>, the ozone deionized aqueous solution or the APM solution may be sprayed to the substrate <NUM> through the spray head <NUM>, while the support platform keeps spinning. For example, when the oxidizing liquid is the ozone deionized aqueous solution, the flow rate of O<NUM> mixed into the deionized water is <NUM>/min~<NUM>/min, the flow rate of the ozone deionized aqueous solution is <NUM>/min~<NUM>/min, the process temperature is <NUM>~<NUM>, the process duration is <NUM>~<NUM>,<NUM>, the rotation speed of the support platform is 100rpm~<NUM>,200rpm, and the thickness of the oxide layer formed is 2Å~12Å. When the oxidizing liquid is the APM solution, the volume ratio of NH<NUM>OH, H<NUM>O<NUM> and H<NUM>O in the APM solution is NH<NUM>OH:H<NUM>O<NUM>:H<NUM>O=<NUM>:(<NUM>~<NUM>):(<NUM>-<NUM>)(as an example: NH<NUM>OH:H<NUM>O<NUM>:H<NUM>O=<NUM>:<NUM>:<NUM>), the temperature is <NUM>~<NUM>, the duration is <NUM>~<NUM>, the process conditions such as the flow rate of the APM solution and the rotation speed of the support platform may be the same as those needed when the ozone deionized aqueous solution is used as an oxidizing solution. The oxide layer formed has 2Å~12Å of a thickness. The person skilled in the art may adjust the thickness of the generated transition layer <NUM> by adjusting the process conditions.

When the material of the substrate <NUM> is silicon, the material of the transition layer <NUM> is silicon dioxide. Due to the transition layer <NUM> formed in the semiconductor structure, the transition layer <NUM> can be prevented from serving as the interface layer between the silicon and the fluid in the subsequent semiconductor rinsing process, such that the resistance of the trenches to the tension of the fluid can be enhanced, i.e., the capillary force exerted by the fluid on the trenches can be reduced. In this way, the pattern structures such as the trenches may be protected. Additionally, the transition layer <NUM> (such as the oxide layer) may also change the hydrophobicity of the semiconductor structure, thereby reducing the Van der Waals' force exerted by the silicon surface on the particulates, such that it is more advantageous to removing the particulates inside the etched structures such as the trenches.

Step S13, drying the semiconductor structure, as shown in <FIG>.

In some embodiments, drying the semiconductor structure comprises the following specific step:
processing the semiconductor structure by means of isopropanol at a preset temperature to remove the moisture on the surface area of the semiconductor structure.

In some embodiments, as shown in <FIG>, hot isopropanol (Hot-IPA) is used as a drying fluid. In one aspect, the Hot-IPA can remove the moisture on the surface area of the semiconductor structure, and in another aspect, it can also help to further reduce the surface tension. The drying fluid is sprayed onto the surface of the semiconductor structure through the spray head <NUM>, and at the same time, the nitrogen is introduced, as the purge gas, into the processing chamber to purge the isopropanol away through the exhaust port of the processing chamber. In this way, the semiconductor structure is dried. The flow rate of the isopropanol is <NUM>/min~<NUM>/min, the temperature is <NUM>~<NUM>, the duration is <NUM>~<NUM>, and the rotation speed of the support platform is <NUM> rpm~<NUM>,<NUM> rpm. The temperature is preset at <NUM>~<NUM>, for example <NUM>.

Step S14, removing the transition layer <NUM>, as shown in <FIG>.

In the drying process, due to the effect of the surface energy of the membrane layer on the surface of the wafer, electrostatic friction may be released and/or the attraction between molecules may be applied, and the top of the etched structure is more fragile than the bottom thereof, so the etched structures is prone to tilt at the top due to the aforementioned forces, as shown in the dashed box in <FIG>. However, within the elastic limit, after the transition layer <NUM> is removed, the attraction between the etched structures is broken, and the etched patterns may bounce off thanks to restoring force to restore to its original state, as shown in <FIG>.

According to the invention, removing the transition layer <NUM> comprises the following specific step:
removing the transition layer <NUM> by means of a mixed gas composed of hydrogen fluoride (<NUM>% HF gaseous) and ammonia gas as the etching gas.

In some embodiments, the substrate <NUM> and the transition layer <NUM> removed by the etching by means of the mixed gas composed of the hydrogen fluoride and the ammonia gas as the etching gas have a total thickness of <NUM> to <NUM>.

According to the invention, the ratio of the flow of the hydrogen fluoride to the flow of the ammonia gas is (<NUM>~<NUM>):<NUM>.

In some embodiments, as shown in <FIG>, HF and NH<NUM> are simultaneously introduced into the processing chamber, and the transition layer <NUM> is removed by means of a vapor etching method. Taking as an example where the material of the transition layer <NUM> is silicon dioxide, the chemical reaction occurring in the process of etching the silicon dioxide by HF and NH<NUM> is as shown in <FIG>. In the process of removing the transition layer, the exhaust gas produced in the reaction process is drawn away in time through the exhaust port at the bottom of the processing chamber, as shown by the arrows in <FIG>. According to the invention, in the process of etching the transition layer <NUM>, a ratio of the flow of HF to the flow of NH<NUM> is (<NUM>~<NUM>):<NUM>. The flow rate of HF and the NH<NUM> is <NUM> sccm~<NUM> sccm (for example, 25sccm), the temperature is <NUM>~<NUM> (for example, <NUM>) , and the duration is <NUM>~<NUM>, the pressure in the processing chamber is <NUM> mtorr~<NUM>,<NUM> mtorr and the temperature of the support platform is <NUM>~<NUM> (for example, <NUM>). In this step, the transition layer <NUM> is over-etched to fully remove the transition layer, such that the etched structures deformed in the drying process by using the isopropanol can be restored to the greatest extent. The thickness of the transition layer <NUM> etched away may be <NUM> to <NUM>. In the process of removing the transition layer <NUM> in this step, the process of alternately and cyclically introducing NH<NUM>/HF and N<NUM> may also be adopted. For example, HF and NH<NUM> are introduced in the first stage, N<NUM> is introduced in the second stage, HF and NH<NUM> are introduced in the third stage, N<NUM> is introduced in the fourth stage. , and so on alternately.

In some embodiments, after removing the transition layer <NUM>, the method further comprises the following step:
purging the semiconductor structure by means of a gas, as shown in <FIG> and <FIG>.

In some embodiments, after the process of etching the transition layer <NUM> is completed, in one aspect, a heater <NUM> inside the support platform is used to heat the substrate <NUM> to evaporate the products generated in the etching reaction. In another aspect, the nitrogen is introduced into the processing chamber and the processing chamber is continuously evacuated, such that the residues generated after the etching reaction are discharged from the processing chamber in time. Finally, the processing chamber is further purged by means of the nitrogen, as shown in <FIG>, until the support platform stops spinning, and the entire wet cleaning process is completed, as shown in <FIG>. In the process of gas purging the semiconductor structure by means of the gas, the flow rate of the nitrogen is 200sccm~<NUM>,000scem (for example, <NUM>,000sccm). The temperature of the wet cleaning is <NUM>~<NUM> (for example, <NUM>), the duration is <NUM>~<NUM>(for example, <NUM>), the pressure of the processing chamber is <NUM> mtorr~<NUM>,<NUM> mtorr (for example, <NUM>,000mtorr).

By using the method for processing a semiconductor structure provided in this embodiment, when the depth H of the trench is <NUM> or <NUM>, the probability of occurrence of collapse or deformation of the pattern after the cleaning process is less than <NUM>%.

<FIG> show a method for processing a semiconductor structure where an etched structures is formed by a mask layer. In other specific embodiments, during processing, the surface of the substrate <NUM> may also have no mask layer. <FIG> are schematic diagrams showing major technologies during processing another semiconductor structure according to embodiments of the present disclosure. That is, <FIG> illustrate schematic diagrams of processing the semiconductor structure having no mask layer on the surface of the substrate. The processing steps and the process conditions during the implementation of each of the processing steps may be the same as the conditions as shown in <FIG> and <FIG>.

Claim 1:
A method for processing a semiconductor structure comprising:
providing a semiconductor structure, the semiconductor structure comprising a substrate (<NUM>) and a plurality of etched structures (<NUM>) arranged on a surface area of the substrate (<NUM>) (S11);
forming a transition layer (<NUM>), the transition layer (<NUM>) at least covering inner walls of the plurality of etched structures (<NUM>), the transition layer (<NUM>) being configured to reduce a capillary force exerted by a fluid on the etched structures (<NUM>) and to serve as a sacrificial layer configured to repair a collapsed structure (S12);
wherein the forming a transition layer (<NUM>), the transition layer (<NUM>) at least covering inner walls of the plurality of etched structures (<NUM>) comprises:
oxidizing the semiconductor structure to form an oxide layer, the oxide layer at least covering inner walls of the trenches, the oxide layer being the transition layer (<NUM>);
drying the semiconductor structure (S13); and
removing the transition layer (<NUM>), after drying the semiconductor structure (S14);
wherein the removing the transition layer (<NUM>) comprises:
removing the transition layer (<NUM>) by means of a mixed gas comprising hydrogen fluoride and ammonia gas as etching gas;
wherein flow ratio of the hydrogen fluoride to the ammonia gas is (<NUM>~<NUM>):<NUM>; flow rate of the hydrogen fluoride and the ammonia gas is <NUM> sccm~<NUM> sccm, temperature is <NUM>~<NUM>, and duration is <NUM>~<NUM>, pressure in a processing chamber is <NUM> mtorr~<NUM>,<NUM> mtorr, and temperature of a support platform is <NUM>~<NUM>.