CN112397382B - Method for processing polycrystalline silicon thin film - Google Patents

Abstract

The invention relates to a method for processing a polysilicon film and a method for manufacturing a thin film transistor. The method for processing the polysilicon film includes: depositing an inorganic film on the surface of the polysilicon film, and using etching particles to keep the inorganic film away from the polysilicon Etching the surface of one side of the film can reduce the surface roughness of the polysilicon film and prevent the etching particles from causing damage to the polysilicon film, thereby reducing the leakage current of the thin film transistor using the polysilicon film as the active layer. When the thin film transistor is applied to a display device, the display effect of the display device can be effectively improved.

Description

A kind of processing method of polysilicon thin film

technical field

The invention relates to the display field, in particular to a method for processing a polysilicon film and a method for manufacturing a thin film transistor.

Background technique

The display device includes an array substrate on which a thin film transistor is arranged, and the thin film transistor includes a gate, a gate insulating layer, an active layer, a source and a drain. Due to the high electron mobility of polysilicon, at present, the material of the active layer of the thin film transistor is mainly polysilicon, so that the thin film transistor has a faster response speed.

In the prior art, the polycrystalline silicon thin film is mainly prepared by ELA (Excimer Laser Anneal, excimer laser annealing) technology, that is, an amorphous silicon thin film is first formed on the substrate, and then the amorphous silicon thin film is subjected to laser annealing treatment to make the amorphous silicon thin film The silicon film is transformed into a polysilicon film. However, the leakage current of the thin film transistor obtained in this way increases, which ultimately affects the display effect of the display device.

Contents of the invention

The purpose of the present invention is to provide a method for processing polysilicon thin films, which can effectively reduce the leakage current of thin film transistors.

In order to achieve the above purpose, the present invention provides a method for processing polysilicon thin films, which adopts the following technical solutions.

An embodiment of the present invention provides a method for processing a polysilicon film, comprising: depositing an inorganic film layer on the surface of the polysilicon film, and using etching particles to etch the surface of the inorganic film layer away from the polysilicon film to remove the The inorganic film layer.

According to an aspect of an embodiment of the present invention, the step of using etching particles to etch the surface of the inorganic film layer away from the polysilicon film comprises: passing inert gas and/or trifluorine into the dissociation device Nitrogen gas, dissociating the inert gas and/or the nitrogen trifluoride gas to form plasma; using the plasma to etch the surface of the inorganic film layer away from the polysilicon film.

According to an aspect of the embodiment of the present invention, the inert gas is argon; preferably, the flow rate of the argon gas is 15000 sccm-25000 sccm, and/or the flow rate of the nitrogen trifluoride gas is 20000 sccm-25000 sccm; preferably Specifically, the feeding times of the argon gas and the nitrogen trifluoride gas are both 2s˜12s.

According to an aspect of the embodiments of the present invention, the etching temperature is 230°C-430°C; preferably, the etching time is 2s-12s.

According to an aspect of an embodiment of the present invention, the step of using etching particles to etch the surface of the inorganic film layer away from the polysilicon film further includes: measuring the thickness of the polysilicon film before depositing the inorganic film layer. The maximum surface roughness, the maximum surface roughness includes the maximum height characteristic parameter a and the maximum distance characteristic parameter b corresponding to the maximum height; measure the average surface roughness of the polysilicon film surface before depositing the inorganic film layer The average height characteristic parameter c; measure the polysilicon grain size d of the polysilicon film; the trajectory of the etching particles and the angle of the surface of the inorganic film layer away from the polysilicon film side are θ and satisfy the following relationship: arctan (c/d)≤θ≤arctan(a/b).

According to an aspect of the embodiments of the present invention, after the etching, the surface of the inorganic film layer is cleaned once with a hydrofluoric acid solution.

According to an aspect of the embodiments of the present invention, after the primary cleaning, the surface of the inorganic film layer is cleaned a second time with pure water.

According to an aspect of the embodiments of the present invention, the thickness of the inorganic film layer is 10-80 nm.

According to an aspect of the embodiments of the present invention, the material of the inorganic film layer is at least one of silicon oxide and silicon nitride.

Further, the present invention also provides a method for manufacturing a thin film transistor, and the method for manufacturing a thin film transistor includes:

A substrate is provided; a gate, a gate insulating layer, an active layer, a source and a drain are formed on the substrate; wherein, the step of forming the active layer on the substrate includes: forming an amorphous Silicon film; using laser annealing technology to convert the amorphous silicon film into a polysilicon film; using the polysilicon film processing method described above to process the polysilicon film; patterning the processed polysilicon film to form a polysilicon film comprising the The pattern of the active layer described above.

Because in the processing method of the polysilicon thin film provided by the present invention, use etching particles to etch the polysilicon thin film after using the inorganic film layer to cover the polysilicon thin film layer, can reduce the surface roughness of the polysilicon thin film and can avoid the etching particle The polysilicon film causes damage, so that the leakage current of the thin film transistor using the polysilicon film as an active layer can be reduced, and the display effect of the display device can be effectively improved when the thin film transistor is applied to a display device.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings, wherein the same or similar reference numerals represent the same or similar features, appended Figures are not drawn to scale.

1 shows a schematic diagram of a polysilicon film processing method provided according to an embodiment of the present invention;

Fig. 2 shows a flowchart of a method for processing a polysilicon thin film according to an embodiment of the present invention.

Detailed ways

The characteristics and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only configured to explain the present invention, not to limit the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by showing examples of the present invention.

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is a relationship between these entities or operations. any such actual relationship or order exists between them. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or apparatus. Without further limitations, an element defined by the statement "comprising..." does not exclude the presence of additional same elements in the process, method, article or device comprising said element.

It should be understood that when describing the structure of a component, when a layer or a region is referred to as being "on" or "over" another layer or another region, it may mean being directly on another layer or another region, or Other layers or regions are also included between it and another layer or another region. And, if the part is turned over, the layer, one region, will be "below" or "beneath" the other layer, another region.

The inventors of the present application have found that when using ELA technology to prepare polysilicon films, the nucleation centers solidify first and the grain boundaries solidify last during the process of transforming amorphous silicon films into polysilicon films, and the density of molten silicon and solid silicon There are differences, so that the formed polysilicon film has protruding grain boundaries, resulting in a high surface roughness of the formed polysilicon film. The inventors further found that the higher the surface roughness of the polysilicon film, the greater the leakage current of the thin film transistor using the polysilicon film as the active layer, wherein the leakage current increases by two orders of magnitude when the surface roughness is doubled. Therefore, when the polysilicon thin film prepared by GLA technology is used as the active layer of the thin film transistor, the leakage current of the thin film transistor is large, and the display effect of the display device is not good. However, in the prior art, when the surface roughness of the polysilicon film is reduced by particle etching, the polysilicon grains are easily damaged, thereby affecting the performance of the transistor made of the polysilicon film.

In order to solve the above problems, an embodiment of the present invention provides a method for processing a polysilicon thin film. The embodiments will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic diagram of a polysilicon film processing process provided by an embodiment of the present invention. As shown in FIG. 1 , an embodiment of the present invention provides a method for processing a polysilicon thin film. The method includes: depositing an inorganic film layer 2 on the surface of a polysilicon thin film 1 . Without any treatment, the surface of the crystalline silicon film 1 has protruding grain boundaries, resulting in a relatively high surface roughness of the polysilicon film 1. After the inorganic film layer 2 is deposited on the surface of the polysilicon film 1, the inorganic film layer 2 corresponds to The raised portion of the polysilicon surface has a smaller thickness. After the inorganic film layer 2 is deposited on the surface of the polysilicon film 1, the surface of the inorganic film layer 2 away from the polysilicon film 1 is etched by etching particles to remove the inorganic film layer 2. The etching particles first etch away the inorganic film layer 2. The thin part corresponds to the raised part on the surface of the polysilicon film 2, etch the particles and then etch the protrusions on the surface of the polysilicon film 1, and as the etching progresses, the protrusions on the surface of the polysilicon film and the inorganic film layer 2 are etched away , so as to reduce the surface roughness of the polysilicon film 1, and at the same time due to the presence of the inorganic film layer 2, the etching particles first etch the inorganic film layer 2 and cannot directly contact the polysilicon film 1, thus avoiding damage to the polysilicon crystal by the etching particles.

Specifically, the material of the inorganic film layer 2 can be at least one of silicon oxide and silicon nitride. When depositing inorganic materials on the surface of the polysilicon film 1, the bonding force between silicon oxide and/or silicon nitride and the polysilicon film 1 is relatively high. , and the sealing performance is good, and the etching particles are not easy to penetrate the silicon oxide film layer and/or the silicon nitride film layer during etching, so that the polysilicon crystal grains can be prevented from being damaged by the etching particles.

Optionally, the thickness of the inorganic film layer 2 is 10nm-80nm. The size of polysilicon grains is often between hundreds of nanometers and several microns, so the size of the protrusions on the surface of polysilicon film 1 is often at the nanometer level or micron level, so when the thickness of the inorganic film layer 2 is 10nm-80nm, its thickness It will not exceed the height of the protrusion on the surface of the polysilicon film 1. After the deposition of the inorganic film layer 2, the protrusion on the surface of the polysilicon film 1 is higher than the thickness of the inorganic film layer 2. When the etching particles are etched, the inorganic film layer 2 can be etched first. The protrusions on the surface are then etched on the protrusions on the surface of the polysilicon film layer 1, and finally the protrusions on the surface of the inorganic film layer 2 and the polysilicon film 1 are etched completely, thereby reducing the surface roughness of the polysilicon film 2 and saving the cost of etching. time.

Accompanying drawing 2 is the flow chart of the embodiment of the present invention processing polysilicon thin film, and step specifically comprises:

Step S201: Depositing an inorganic film layer on the surface of the polysilicon film. Optionally, an inorganic film layer 2 with a thickness of 10nm-80nm is deposited on the surface of the polysilicon film 1 by chemical vapor deposition, and the material of the inorganic film layer can be silicon oxide and/or silicon nitride.

Step S202: Inert gas and/or nitrogen trifluoride gas is introduced into the dissociation device. In some embodiments of the present application, an inert gas may be introduced into the dissociation device separately, and the inert gas may be the more commonly used argon gas, so as to reduce the cost of the processing method of the polysilicon film 1, wherein the argon The larger the flow rate of the gas, the greater the etching rate of the polysilicon film 1. In the embodiment of the present invention, after comprehensively considering the etching rate and etching uniformity, the flow rate of argon gas is preferably 15000 sccm-25000 sccm, and the ventilation time is 2s-2s. 12s; in some other embodiments of the present application, nitrogen trifluoride gas can also be passed into the dissociation equipment separately, wherein, the flow rate of the nitrogen trifluoride gas passed into is larger, the etching of polysilicon film 1 The greater the speed, after comprehensively considering the etching speed and etching uniformity, the flow rate of nitrogen trifluoride gas is preferably 20000sccm-25000sccm, and the ventilation time is 2s-12s; in other embodiments of the present application, it can be used in Pass inert gas and nitrogen trifluoride into the dissociation equipment at the same time, the inert gas can be argon, preferably the flow rate of argon is 15000sccm～25000sccm, the aeration time is 2s～12s, the flow rate of nitrogen trifluoride gas is 20000sccm～25000sccm , ventilation time is 2s ~ 12s. Optionally, the dissociation device may be a chemical vapor deposition device or an electromagnetic resonant cavity, which can be selected according to actual conditions.

Step S203: dissociate the inert gas and/or nitrogen trifluoride gas to form plasma. Optionally, the temperature for dissociating the inert gas and/or nitrogen trifluoride gas is between 230°C and 430°C. Wherein when the inert gas is argon, it dissociates to form argon plasma, and uses argon plasma to bombard the above-mentioned polysilicon film, and smashes the protrusions on the surface of the above-mentioned inorganic film layer 2 and polysilicon film 1 by physical bombardment, thereby reducing the The surface roughness of polysilicon thin film 1; When using nitrogen trifluoride gas as the gas during dissociation, can dissociate and form fluorine plasma, when using fluorine plasma to carry out bombardment to above-mentioned polysilicon thin film, fluorine plasma can and inorganic film A chemical reaction occurs in the layer 2 to expose the protrusions on the surface of the polysilicon film, and at the same time, the fluorine plasma can etch the protrusions on the surface of the polysilicon film 1, thereby reducing the surface roughness of the polysilicon film 1 . Preferably, when the gas to be dissociated includes argon and nitrogen trifluoride gas at the same time, fluorine plasma and argon plasma can be generated simultaneously, and the etching effect on the protrusions on the surface of the inorganic film layer 2 and the polysilicon film is better.

Step S204: using plasma to etch the surface of the inorganic film layer away from the polysilicon film. Optionally, when using plasma to etch the inorganic film layer, the etching temperature is 230°C-430°C, and the etching time is 2s-12s. Under the premise of ensuring the degree of etching, avoid excessive etching The polysilicon thin film 1 is damaged.

Specifically, before depositing the inorganic film layer 2, the maximum surface roughness, the average surface roughness and the polysilicon grain size d of the polysilicon film 1 are measured. Surface roughness refers to the small spacing and the unevenness of small peaks and valleys on the processed surface, which includes three evaluation parameters of height characteristic parameters, spacing characteristic parameters and shape characteristic parameters. The measured maximum surface roughness includes a maximum height characteristic parameter a, a maximum spacing characteristic parameter b corresponding to the maximum height, and an average height characteristic parameter c of the average surface roughness. When using plasma etching, the angle between the trajectory of the etching particles in the plasma and the surface of the inorganic film layer 2 is θ (the acute angle included angle formed between the trajectory of the etching particles in the plasma and the surface of the inorganic film layer 2 ), and satisfy arctan(c/d)≤θ≤arctan(a/b), so as to prevent the etching particles from bombarding the part where there is no protrusion on the surface of the inorganic film layer 2, and avoid the flat part of the inorganic film layer 2 from being engraved first etch to expose the surface of the polysilicon film 1 prematurely, preventing the polysilicon film 1 from being damaged by etching particles.

Further, after the etching is finished, the surface of the polysilicon film 1 on which the inorganic film layer 2 is deposited is cleaned once with a hydrofluoric acid solution to remove the remaining inorganic film layer 2 after etching to obtain a flat polysilicon film 1 .

Furthermore, after the hydrofluoric acid solution is used to clean the polycrystalline silicon film 1 once, the surface of the polysilicon film 1 on which the inorganic film layer 2 is deposited is cleaned with pure water to remove residual hydrofluoric acid and residues.

In addition, an embodiment of the present invention also provides a method for manufacturing a thin film transistor. The method for manufacturing a thin film transistor includes: providing a substrate; forming a gate, a gate insulating layer, an active layer, a source, and a drain on the substrate; step. Wherein, the step of forming the active layer on the substrate includes: forming an amorphous silicon film on the substrate; using laser annealing technology to convert the amorphous silicon film into a polysilicon film; using the above-mentioned polysilicon film processing technology to process the polysilicon film and patterning the processed polysilicon film to form a pattern including an active layer. The substrate can be a glass substrate or a conformable substrate.

Exemplarily, when fabricating a bottom-gate thin film transistor, the steps of forming a gate, a gate insulating layer, an active layer, a source, and a drain on a substrate specifically include: first, forming a gate metal layer on a substrate, and after The patterning process forms a pattern including the gate; then, a gate insulating layer is formed on the substrate; then, an active layer is formed on the substrate; finally, a source-drain metal layer is formed on the substrate, and the patterning process is used to form a gate insulating layer including the source and drain. Extreme graphics.

It should be noted that when fabricating a bottom-gate TFT, the steps of forming a gate, a gate insulating layer, an active layer, a source, and a drain on a substrate are not limited thereto, and are not limited in this embodiment of the present invention. In addition, when making a top-gate thin film transistor, those skilled in the art can refer to the above-mentioned content and carry out the specific implementation of the steps of forming a gate, a gate insulating layer, an active layer, a source electrode and a drain electrode on a substrate, and in combination with actual needs. selection, which will not be repeated here.

In the thin film transistor manufacturing method provided in the embodiment of the present invention, in the process of forming the active layer, the polysilicon film is treated as above, which reduces the surface roughness of the polysilicon film and avoids damage to the polysilicon film at the same time, That is, the surface roughness of the active layer is reduced, damage to the active layer is avoided, and the leakage current of the thin film transistor is reduced, so that when the thin film transistor is applied to a display device, the display effect of the display device can be effectively improved .

According to the embodiments of the present invention described above, these embodiments do not describe all details in detail, nor do they limit the invention to only the specific embodiments described. Obviously many modifications and variations are possible in light of the above description. This description selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and its modification on the basis of the present invention. The invention is to be limited only by the claims, along with their full scope and equivalents.

Claims (7)

1. A processing method for a polysilicon film, characterized in that, comprising: Depositing an inorganic film layer on the surface of the polysilicon film, the thickness of the inorganic film layer is 10 nm to 80 nm, and will not exceed the height of the protrusions on the surface of the polysilicon film; using etching particles to etch the surface of the inorganic film layer away from the polysilicon film to remove the inorganic film layer; The step of using etching particles to etch the surface of the inorganic film layer away from the polysilicon film comprises: Measuring the maximum surface roughness of the surface of the polysilicon thin film before depositing the inorganic film layer, the maximum surface roughness includes a maximum height characteristic parameter a and a maximum spacing characteristic parameter b corresponding to the maximum height; Measuring the average height characteristic parameter c of the average surface roughness of the surface of the polysilicon film before depositing the inorganic film layer, and the polysilicon grain size d of the polysilicon film; The angle between the trajectory of the etching particles and the surface of the inorganic film layer away from the polysilicon film is θ and satisfies the following relationship: arctan(c/d)≤θ≤arctan(a/b); Pass inert gas and nitrogen trifluoride gas into the dissociation equipment, dissociate the inert gas and the nitrogen trifluoride gas to form plasma, and the inert gas is argon; The plasma is used to etch the surface of the inorganic film layer away from the polysilicon film. 2. The method for processing polysilicon thin films according to claim 1, wherein the flow rate of the argon gas is 15000-25000 sccm, and the flow rate of the nitrogen trifluoride gas is 20000-25000 sccm; The feeding times of the argon gas and the nitrogen trifluoride gas are both 2s˜12s. 3. The method for processing a polysilicon thin film according to claim 1 or 2, wherein the etching temperature is 230° C. to 430° C.; The etching time is 2s˜12s. 4. the processing method of polysilicon thin film according to claim 1 is characterized in that, after described etching finishes, use hydrofluoric acid solution to carry out one side surface that described polysilicon thin film is deposited with described inorganic film layer cleaning. 5 . The method for processing a polysilicon thin film according to claim 4 , characterized in that, after the primary cleaning, the surface of the polysilicon thin film on which the inorganic film layer is deposited is subjected to a second cleaning with pure water. 6 . 6 . The method for processing a polysilicon thin film according to claim 1 , wherein the material of the inorganic film layer is at least one of silicon oxide and silicon nitride. 7. A method for manufacturing a thin film transistor, comprising: providing a substrate; forming a gate, a gate insulating layer, an active layer, a source and a drain on the substrate; Wherein, the step of forming the active layer on the substrate comprises: forming an amorphous silicon thin film on the substrate; Using laser annealing technology to convert the amorphous silicon film into a polysilicon film; processing the polysilicon film by using the polysilicon film processing method according to any one of claims 1 to 6; Patterning the processed polysilicon film to form a pattern including the active layer.

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