TW201503237A - Method for improving uniformity of polycrystalline germanium layer - Google Patents

Abstract

The invention provides a method for improving the uniformity of a polycrystalline germanium layer, comprising: forming an amorphous germanium layer on a substrate; performing a dry surface treatment on the amorphous germanium layer to form a first germanium oxide layer; and removing the surface of the amorphous germanium layer a first ruthenium oxide layer; a second ruthenium oxide layer formed on the surface of the amorphous ruthenium layer; and an amorphous ruthenium layer formed into a polysilicon ruthenium gate layer by crystallization treatment. According to the method of the invention, the dry surface treatment of the amorphous germanium layer avoids the problem of wet treatment of residual ozone water, and at the same time plays the role of cleaning, oxidation and avoiding the damage of the lower layer, and can effectively improve the polycrystalline germanium layer after the crystallization treatment. Uniformity of grain size. In addition, the method of the invention is advantageous for improving production efficiency and productivity, and is safer to operate and more convenient to maintain.

Description

Method for improving uniformity of polycrystalline germanium layer

The present invention relates to a method of forming a polycrystalline germanium layer, and more particularly to a method of increasing the uniformity of a polycrystalline germanium layer.

Compared with amorphous germanium thin film transistors, polycrystalline germanium thin film transistors have higher electron mobility, faster reaction time and higher resolution, and have been widely used in display devices as switching elements of the driving circuit. The method for fabricating a polycrystalline germanium film transistor is generally a low temperature polysilicon method (LTPS) in which an amorphous germanium layer is usually formed by chemical vapor deposition (CVD), and the amorphous germanium layer is crystallized. At present, excimer laser annealing (ELA) technology is generally used for crystallization. The amorphous germanium layer is irradiated by 308 nm laser and melted to form an amorphous germanium liquid. When the amorphous germanium liquid is cooled, the amorphous germanium liquid gradually crystallizes according to the attached crystal nucleus. The polycrystalline germanium layer is formed.

Before the crystallization of ELA, it is usually necessary to pre-crystallize the amorphous germanium to form a polycrystalline germanium layer with a large and uniform grain size, so that the finally obtained polycrystalline germanium thin film transistor has a lower threshold voltage and a larger electron. Migration rate. ELA crystal pretreatment is generally formed on the amorphous layer The surface oxide layer is energy-buffered by the oxide layer to obtain a larger grain size. As shown in FIG. 1, the current surface oxide layer preparation method is usually subjected to ozone water treatment-hydrofluoric acid treatment-ozone water treatment to finally form the surface oxide layer 4. The amorphous germanium layer 20 prepared by CVD film formation is oxidized in a natural environment to form a surface natural oxide layer 1, which has poor uniformity and compactness, and the first step of ozone water treatment aims to further oxidize nature. Oxide layer 1, which is compensated for a more uniform oxide layer 3 to facilitate uniformity of subsequent hydrofluoric acid treatment while removing surface deposits 2. Since the oxide layer 3 contains a poor quality natural oxide layer, it needs to be removed by a second step of hydrofluoric acid treatment. Then, a uniform quality oxide layer 4 of excellent quality is formed on the surface of the amorphous germanium layer 20 by the third step of ozone water treatment.

However, the first step of ozone water oxidation treatment is wet treatment, and there is a problem of residual ozone water. As shown in Fig. 1, when the second step of hydrofluoric acid treatment is performed, the oxide layer in the residual portion is removed by hydrofluoric acid. The exposed lower amorphous germanium layer 20 is again oxidized by residual ozone water, and then removed by hydrofluoric acid, resulting in a change in the thickness of the amorphous germanium layer 20, and the thickness uniformity of the amorphous germanium layer 20 is deteriorated. The grain size uniformity of the polycrystalline germanium 30 after the crystallization treatment is affected. With the continuous development of the display industry, the size of glass substrates is increasing, and the above-mentioned residual problem is more likely to be caused by ozone water treatment of large-area amorphous enamel boards. The uniformity of the grain size of the polysilicon layer 30 will greatly affect the uniformity of the threshold voltage and current characteristics of the finally obtained polycrystalline germanium film transistor.

Therefore, there is a need for a method for improving the uniformity of the polycrystalline germanium layer, which solves the residual problem of the above wet processing, and cleans and oxidizes the surface of the amorphous germanium. When the underlying amorphous germanium is damaged, the grain size uniformity of the polycrystalline germanium layer after the crystallization treatment can be improved, thereby improving the electrical properties of the polycrystalline germanium thin film transistor.

Accordingly, the present invention provides a method of improving the uniformity of a polysilicon layer, the method comprising the steps of: forming an amorphous germanium layer on a substrate; performing a dry surface treatment on the amorphous germanium layer to form a first tantalum oxide layer; The surface of the germanium layer is removed from the first tantalum oxide layer; a second tantalum oxide layer is formed on the surface of the amorphous germanium layer; and the amorphous germanium layer is formed into a polycrystalline germanium layer by crystallization treatment.

In one embodiment of the method of the invention, the dry surface treatment is carried out using an extreme ultraviolet cleaning device or an atmospheric piezoelectric slurry cleaning device.

In another embodiment of the method of the invention, the dry surface treatment is carried out for 10 to 40 seconds.

In another embodiment of the method of the present invention, the dry surface treatment further comprises removing surface deposits.

In another embodiment of the method of the invention, wherein the surface attachment comprises an organic contaminant.

In another embodiment of the method of the invention, the step of removing the first ruthenium oxide layer is carried out using a hydrofluoric acid solution.

In another embodiment of the method of the present invention, the hydrofluoric acid solution The mass concentration is 0.5% to 2%.

In another embodiment of the method of the present invention, the step of removing the first ruthenium oxide layer is carried out for 20 to 40 seconds.

In another embodiment of the method of the invention, the step of forming the second ruthenium oxide layer is carried out using ozone water.

In another embodiment of the method of the invention, the concentration of the ozone water is from 15 to 30 ppm.

In another embodiment of the method of the present invention, the step of forming the second hafnium oxide layer is carried out for 20 to 40 seconds.

In another embodiment of the method of the invention, the crystallization treatment is a quasi-molecular laser crystallization treatment.

In another embodiment of the method of the present invention, the polycrystalline germanium layer has a grain size of 2700 Å to 4300 Å.

According to the method of the invention, the dry surface treatment is carried out by using an extreme ultraviolet cleaning device or an atmospheric piezoelectric slurry cleaning device, and the extreme ultraviolet cleaning and the atmospheric piezoelectric cleaning are both gaseous oxidation mechanisms, using gaseous ozone, active oxygen atoms or oxygen plasma for amorphous Oxidation of the surface of the ruthenium layer compensates the natural oxide layer to a uniform oxide layer and thoroughly removes surface deposits, especially organic matter, without residual problems, and at the same time acts to clean, oxidize and avoid damage to the underlying layer, thereby effectively improving crystallization. The uniformity of the grain size of the polycrystalline germanium layer after the treatment.

Furthermore, according to the current method, the ozone water treatment-hydrofluoric acid treatment-ozone water treatment needs to be sequentially performed in the same chamber, and the latter step must be performed after the completion of the previous step, which is a tandem process, and the method of the present invention Extremely purple Both external cleaning and atmospheric plasma cleaning are performed in separate chambers, which can be synchronized with subsequent processing as a parallel process. Thus, in the case where the excimer laser annealing treatment technology is perfected day by day, the production efficiency and the productivity are further improved by overcoming the bottleneck in the pretreatment process.

In addition, ozone water is a strong oxidizing solution, which is extremely oxidative and corrosive, posing a certain threat to the health and safety of operators. In contrast, the ultra-violet cleaning device and the atmospheric piezoelectric slurry cleaning device used in the method of the present invention operate more. Safe and easy to maintain.

1‧‧‧ natural oxide layer

2‧‧‧Surface attachments

3‧‧‧First ruthenium oxide layer

4‧‧‧Second ruthenium oxide layer

10‧‧‧Substrate

20‧‧‧Amorphous layer

30‧‧‧Polysilicon layer

1 is a schematic flow chart showing the steps of a prior art polycrystalline germanium layer forming method; and FIG. 2 is a schematic flow chart showing the steps of the method of the present invention.

The technical solution of the present invention will be further described below according to specific embodiments. The scope of the present invention is not limited to the following embodiments, and the examples are given for illustrative purposes only and are not intended to limit the invention in any way.

The present invention provides a method for improving the uniformity of a polysilicon layer. As shown in FIG. 2, the method includes the steps of: forming an amorphous germanium layer 20 on a substrate 10; and performing dry surface treatment on the amorphous germanium layer 20 to compensate The natural oxide layer 1 forms the first ruthenium oxide layer 3 and removes the surface attachment 2; the first ruthenium oxide layer 3 is removed from the surface of the amorphous ruthenium layer 20; and the second ruthenium oxide layer 4 is formed on the surface of the amorphous ruthenium layer 20. And crystallization treatment to make the amorphous The germanium layer 20 forms a polysilicon gate layer.

Since the natural oxide layer 1 is formed in an island shape and unevenly formed on the surface of the amorphous germanium layer 20, if it is directly removed by etching with a hydrofluoric acid solution, etching of the surface of the amorphous germanium layer 20 is uneven. Therefore, according to the method of the present invention, first, an extreme ultraviolet cleaning device or an atmospheric piezoelectric slurry device is used instead of ozone water, and the first dry surface treatment is performed, and the natural oxide layer 1 is compensated for a relatively uniform oxide layer by a gaseous oxidation mechanism while avoiding The residual problem of the solution existing in the ozone water wet process is favorable to form the amorphous germanium layer 20 having a uniform thickness, thereby improving the uniformity of the grain size of the crystallized polycrystalline germanium layer 30.

In one embodiment of the method of the present invention, the first dry surface treatment is performed using an extreme ultraviolet cleaning device, which is an extreme ultraviolet cleaning lamp (EUV lamp), which is used to air in an atmospheric environment. The surface of the amorphous germanium layer 20 is irradiated with a surface treatment for the medium, and the surface treatment is preferably carried out for 20 seconds to compensate the natural oxide layer 1 to form a relatively uniform first tantalum oxide layer 3, and to remove the surface deposit 2. The working mechanism of the extreme ultraviolet cleaning lamp will be specifically described below. The ultra-violet cleaning lamp emits ultraviolet light with a wavelength of 172 nm. The oxygen molecules in the air absorb ozone and oxygen after absorbing 172 nm wavelength ultraviolet light. The ozone is unstable and further decomposes into active oxygen atoms and oxygen, thereby utilizing the strong active oxygen atoms. Oxidation compensates the natural oxide layer 1 on the surface of the amorphous germanium layer 20 as a uniform oxide layer. In addition, the 172nm ultraviolet light emitted by the extreme ultraviolet cleaning lamp has a high energy, which is higher than the binding energy of most organic substances. Most hydrocarbons have strong absorption of 172nm ultraviolet light, and absorb high-energy ultraviolet light. The solution is an ion, a free atom, an excited molecule, a neutron, etc., that is, a photosensitizing effect. At the same time, the strong oxidizing active oxygen atom generated by the decomposition of ozone can cut off the carbon-hydrogen bond of the organic matter to form a volatile gas such as water and carbon dioxide, which escapes from the surface of the irradiated amorphous germanium layer 20, thereby completely eliminating surface contamination thereof. Things. Compared with ozone water treatment, the extreme ultraviolet cleaning treatment can more thoroughly remove surface deposits 2, especially organic substances, to achieve atomic cleanliness of the surface, and effectively reduce defects caused by surface residual impurities entering the polycrystalline germanium layer 30.

In another embodiment of the method of the present invention, the first step of dry surface treatment is performed using an atmospheric piezoelectric slurry cleaning device, which is an atmospheric piezoelectric slurry cleaning machine. Preferably, the atmospheric piezoelectric slurry cleaning machine is used. The surface of the wafer layer 20 is subjected to a surface treatment for 20 seconds to compensate the natural oxide layer 1 to form a relatively uniform first yttria layer 3, and to remove the surface deposits 2. The working principle of the atmospheric piezoelectric slurry cleaning machine will be specifically described below. In an atmospheric piezoelectric plasma cleaner, an accelerating electron is generated by applying a voltage, and an electron reacts with a gas molecule such as oxygen to generate an oxygen atom and ozone, a reactive oxygen atom having a strong oxidizing property, and a natural oxide layer on the surface of the amorphous germanium layer 20 by ozone. The compensation is a uniform first yttria layer 3. In addition, ultraviolet light is generated at the same time in the atmospheric piezoelectric slurry treatment, and combined with the above chemical reaction, has a good surface cleaning effect, and the principle of removing organic substances is similar to the above-mentioned extreme ultraviolet cleaning lamp.

According to the present invention, after the surface of the amorphous germanium layer 20 is surface-treated to form a relatively uniform first tantalum oxide layer 3, the first tantalum oxide layer 3 containing the native oxide layer 1 is removed from the surface of the amorphous germanium layer 20. . In one embodiment of the method of the present invention, the first oxidation is removed using a hydrofluoric acid solution 矽 layer 3. The mass concentration of the hydrofluoric acid solution is preferably 0.5% to 2%. If the concentration is too high and the etching rate is too fast, the amorphous germanium layer 20 is excessively corroded. If the concentration is too small and the etching rate is too slow, the first germanium oxide cannot be effectively removed. Layer 3. The step of removing the first hafnium oxide layer 3 is preferably carried out for 20 to 40 seconds. Similarly, if the time is too long, the amorphous germanium layer 20 is excessively corroded, and if the time is too short, the first hafnium oxide layer 3 cannot be effectively removed.

After the first hafnium oxide layer 3 is removed, wet etching can be performed to form a second hafnium oxide layer 4 having a uniform thickness and excellent film quality on the surface of the amorphous hafnium layer 20. In one embodiment of the method of the present invention, the surface of the amorphous germanium layer 20 is washed with ozone water to form a second hafnium oxide layer 4 having a good thickness uniformity. The concentration of the ozone water is preferably 15 to 30 ppm, the concentration is too high, the oxidation rate is too large, and it is difficult to control the uniformity of the second ruthenium oxide layer 4. The concentration is too low, and the oxidation rate is too small, which is disadvantageous for forming a uniform second ruthenium oxide layer. 4. The step of forming the second hafnium oxide layer 4 is preferably carried out for 20 to 40 seconds to form a good thickness uniformity, and if the time is too short, the second hafnium oxide layer 4 cannot be sufficiently formed.

As described above, since the first ruthenium oxide layer 3 is formed by dry surface treatment, there is no problem that the wet oxidization treatment solution remains, and thus the amorphous ruthenium layer 20 formed by removing the first ruthenium oxide layer 3 by hydrofluoric acid etching has Good thickness uniformity and small thickness change rate improve the grain size uniformity of the subsequently formed second hafnium oxide layer 4 and the polycrystalline germanium layer 30 formed by the subsequent crystallization treatment.

The amorphous germanium layer 20 can be crystallized to form the polycrystalline germanium layer 30 by various crystallization methods. According to the method of the present invention, an amorphous germanium layer 20 coated with a hafnium oxide layer is preferably irradiated with a pulsed laser using an excimer laser annealing (ELA) method. When it is melted and the amorphous cerium liquid is cooled, the amorphous cerium liquid gradually crystallizes depending on the crystal nucleus to form the polycrystalline germanium layer 30.

The uniformity of the grain size of the polycrystalline germanium layer can be evaluated by measuring the change in grain size. Usually, the sample points are selected on the prepared polycrystalline germanium panel, and then the samples are lobed, and the grain size is evaluated by a scanning electron microscope. According to the method of the present invention, the grain size change of the obtained polycrystalline germanium layer can be controlled. In the range of 2700 Å to 4300 Å, the grain size of the polycrystalline germanium layer obtained by conventional ozone water treatment-hydrofluoric acid treatment-ozone water treatment generally varies from 2000 Å to 5000 Å, thereby showing that the polycrystalline germanium according to the method of the present invention The grain size uniformity of the layer is significantly improved.

Unless otherwise defined, the terms used in the present invention are intended to be understood by those skilled in the art. The invention will now be further described in detail by way of examples.

Example Example 1

First, an amorphous germanium layer having a thickness of 450 Å was formed on the glass substrate by chemical vapor deposition. Then, an EUV ultraviolet cleaning lamp (HP-V type, manufactured by UHSIO, Japan) was used to irradiate the surface of the amorphous ruthenium layer with air as a medium for 20 seconds to form a first ruthenium oxide layer having a thickness of 20 Å. Then, the surface was washed with a hydrofluoric acid solution having a mass concentration of 1% by a rotary spray method for 30 seconds to remove the first ruthenium oxide layer. The surface of the amorphous germanium layer was then treated with a concentration of 25 ppm of ozone water using a rotary spray method for 30 seconds to form a 20 Å second ruthenium oxide layer. Finally, using an excimer laser annealing equipment (KORONATM LTP G4.5, manufactured by AP Systems) at room temperature and atmospheric pressure, the amorphous germanium layer is thundered with an energy of 300 to 500 mJ/cm ² and a scanning pitch of 5 to 30 μm. The annealing crystallization treatment forms a polycrystalline germanium layer.

The grain size uniformity of the obtained polycrystalline germanium layer was evaluated by scanning electron microscopy. The results showed that the grain size varied from 2700 Å to 4300 Å.

Example 2

First, an amorphous germanium layer having a thickness of 450 Å was formed on the glass substrate by chemical vapor deposition. Then, an amorphous piezoelectric layer cleaning machine (Model SD1024, manufactured by E-Square, Japan) was used to surface-treat the amorphous tantalum layer for 20 seconds to form a first tantalum oxide layer having a thickness of 20 Å. Then, the surface was washed with a hydrofluoric acid solution having a mass concentration of 1% by a rotary spray method for 30 seconds to remove the first ruthenium oxide layer. The surface of the amorphous germanium layer was then treated with a concentration of 25 ppm of ozone water using a rotary spray method for 30 seconds to form a 20 Å second ruthenium oxide layer. Finally, using an excimer laser annealing equipment (KORONATM LTP G4.5, manufactured by AP Systems) at room temperature and atmospheric pressure, the amorphous germanium layer is thundered with an energy of 300 to 500 mJ/cm ² and a scanning pitch of 5 to 30 μm. The annealing crystallization treatment forms a polycrystalline germanium layer.

The grain size uniformity of the obtained polycrystalline germanium layer was measured by a scanning electron microscope, and the grain size was varied from 2700 Å to 4300 Å.

Comparative example 1

First, an amorphous germanium layer having a thickness of 450 Å was formed on the glass substrate by chemical vapor deposition. The surface of the amorphous tantalum layer was treated with ozone water having a concentration of 25 ppm by a rotary spray method for 20 seconds to form a first tantalum oxide layer having a thickness of 20 Å. Then, the surface was washed with a hydrofluoric acid solution having a mass concentration of 1% by a rotary spray method for 30 seconds to remove the first ruthenium oxide layer. The surface of the amorphous germanium layer was then treated with a concentration of 25 ppm of ozone water using a rotary spray method for 30 seconds to form a 20 Å second ruthenium oxide layer. Finally, using an excimer laser annealing equipment (KORONATM LTP G4.5, manufactured by AP Systems) at room temperature and atmospheric pressure, the amorphous germanium layer is thundered with an energy of 300 to 500 mJ/cm ² and a scanning pitch of 5 to 30 μm. The annealing crystallization treatment forms a polycrystalline germanium layer.

The grain size uniformity of the obtained polycrystalline germanium layer was measured by a scanning electron microscope. The results showed that the grain size varied from 2000 Å to 5000 Å.

As shown in the measurement results of the above Examples 1, 2 and Comparative Example 1, the ozone water was replaced by an EUV ultraviolet cleaning lamp or an atmospheric piezoelectric slurry cleaning machine, that is, the gaseous dry treatment was used instead of the solution wet treatment, and the first surface treatment was performed. Forming the first ruthenium oxide layer, the grain size change of the finally obtained crystallization polysilicon layer is significantly reduced, and the grain size uniformity is remarkably improved, thereby facilitating the uniform threshold voltage of the finally obtained polycrystalline ruthenium film transistor. And current characteristics.

It should be understood by those skilled in the art that the presently described embodiments are merely exemplary, and that various alternatives, modifications and improvements are possible within the scope of the invention. Thus, the present invention is not limited to the above embodiments, but is limited only by the claims.

1‧‧‧ natural oxide layer

2‧‧‧Surface attachments

3‧‧‧First ruthenium oxide layer

4‧‧‧Second ruthenium oxide layer

10‧‧‧Substrate

20‧‧‧Amorphous layer

30‧‧‧Polysilicon layer

Claims (13)

A method for improving uniformity of a polycrystalline germanium layer, comprising the steps of: forming an amorphous germanium layer on a substrate; performing dry surface treatment on the amorphous germanium layer to form a first tantalum oxide layer; removing the amorphous germanium layer from the surface a first ruthenium oxide layer; a second ruthenium oxide layer formed on the surface of the amorphous ruthenium layer; and the amorphous ruthenium layer is formed into a polycrystalline ruthenium layer by crystallization treatment. The method of claim 1, wherein the dry surface treatment step is performed using an extreme ultraviolet cleaning device or an atmospheric piezoelectric slurry cleaning device. The method of claim 2, wherein the dry surface treatment is performed for 10 to 40 seconds. The method of claim 1, wherein the dry surface treatment further comprises removing surface deposits. The method of claim 4, wherein the surface attachment comprises an organic contaminant. The method of claim 1, wherein the step of removing the first ruthenium oxide layer is performed using a hydrofluoric acid solution. The method of claim 6, wherein the hydrofluoric acid solution has a mass concentration of 0.5% to 2%. The method of claim 1, wherein the step of removing the first ruthenium oxide layer is performed for 20 to 40 seconds. The method of claim 1, wherein the step of forming the second ruthenium oxide layer is performed using ozone water. The method of claim 9, wherein the concentration of the ozone water is 15 to 30 ppm. The method of claim 1, wherein the step of forming the second hafnium oxide layer is performed for 20 to 40 seconds. The method of claim 1, wherein the crystallization treatment is a quasi-molecular laser crystallization treatment. The method of any one of claims 1 to 12, wherein the polycrystalline germanium layer has a grain size of 2700 Å to 4300 Å.