Plasma processing method for oxide semiconductor channel film

Abstract

The invention provides a plasma processing method of an oxide semiconductor channel film, which comprises the following steps: preparing an amorphous oxide semiconductor channel film on a substrate to obtain an amorphous oxide semiconductor sample containing the channel film; putting the sample into a reaction cavity of plasma equipment, and vacuumizing the reaction cavity; introducing reaction gas and auxiliary gas into the vacuumized reaction cavity; adjusting the input power and the gas partial pressure of the plasma equipment for the first time so as to excite reaction gas to build up luminance in the reaction cavity to generate plasmas; and in a preset first time threshold value, the input power and the gas partial pressure of the plasma equipment are adjusted for the second time so as to change the density and the energy of the plasma, and the plasma processing of the amorphous oxide semiconductor channel film is realized in the reaction cavity. According to the method, oxygen exchange between the oxygen plasma and the oxygen-containing amorphous oxide semiconductor thin film is utilized, the hydrogen concentration in the channel is reduced, and the quality of the amorphous oxide semiconductor channel is improved.

Description

Technical Field

[0001] The present invention relates to the field of plasma and semiconductor technology, and in particular to a plasma processing method for an oxide semiconductor channel film. Background Art

[0002] Amorphous oxide semiconductors (AOS), such as amorphous indium gallium zinc oxide (a-IGZO), have important applications in the field of thin film transistors (TFTs) due to their excellent electron mobility and low process temperature. However, at present, the introduction of impurity hydrogen in the preparation process of AOS thin films is inevitable, which has multiple effects on device performance. Low concentrations of hydrogen atoms can passivate interface defects, reduce subthreshold swing, and improve TFT characteristics. However, as the hydrogen concentration increases, it affects the negative bias stability of thin film transistors, resulting in threshold voltage drift and increased subthreshold swing.

[0003] To solve these problems, different post-treatment methods such as room temperature hydrogen plasma treatment and high temperature H2 annealing are used in the prior art. These treatment methods use hydrogen as doping to increase carrier concentration and improve device performance, but they cause device reliability issues, especially high temperature stability (>400°C). Therefore, reducing the hydrogen concentration in the AOS film as much as possible is an effective way to improve the long-term reliability of the device. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the above-mentioned deficiencies, the main purpose of the present invention is to provide a plasma treatment method for an oxide semiconductor channel film, which utilizes the oxygen exchange phenomenon between oxygen plasma and oxygen-containing amorphous oxide semiconductor film to achieve the outward diffusion of hydrogen atoms, reduce the hydrogen concentration in the channel, and improve the quality of the amorphous oxide semiconductor channel.

[0006] (II) Technical solution

[0007] In order to achieve the above-mentioned purpose, the present invention provides a plasma treatment method for an oxide semiconductor channel film, comprising: preparing an amorphous oxide semiconductor channel film on a substrate to obtain an amorphous oxide semiconductor sample containing the channel film; placing the amorphous oxide semiconductor sample containing the channel film into a reaction chamber of a plasma device, and evacuating the reaction chamber; introducing a reaction gas and an auxiliary gas into the evacuated reaction chamber; adjusting the input power and gas partial pressure of the plasma device for the first time to excite the reaction gas to ignite and generate plasma in the reaction chamber; and adjusting the input power and gas partial pressure of the plasma device for the second time within a preset first time threshold to change the density and energy of the plasma, thereby realizing plasma treatment of the amorphous oxide semiconductor channel film in the reaction chamber.

[0008] In the above scheme, the reaction gas is oxygen, and the auxiliary gas is one or more of nitrogen and inert gas.

[0009] In the above scheme, the input power and gas partial pressure of the plasma device are adjusted for the first time to excite the reaction gas to generate plasma in the reaction chamber, including: by adjusting the input power and oxygen partial pressure of the plasma device for the first time, exciting oxygen to generate oxygen plasma.

[0010] In the above scheme, the input power and gas partial pressure of the plasma device are adjusted for a second time to change the density and energy of the plasma, and plasma treatment of the amorphous oxide semiconductor channel film is achieved in the reaction chamber, including: by adjusting the input power and oxygen partial pressure of the plasma device for a second time, the density and energy of the oxygen plasma are changed to obtain an oxygen-containing plasma environment; based on the oxygen-containing plasma environment, oxygen is exchanged between the oxygen plasma and the oxygen-containing amorphous oxide semiconductor film to achieve plasma treatment of the amorphous oxide semiconductor channel film.

[0011] In the above scheme, plasma is generated by excitation, and the excitation methods include microwave excitation plasma, inductively coupled excitation plasma, cyclotron resonance excitation plasma and radio frequency excitation plasma.

[0012] In the above scheme, the density and energy of the oxygen plasma are changed by adjusting the input power and oxygen partial pressure of the plasma equipment for the second time to obtain an oxygen-containing plasma environment, including: changing the density of the oxygen plasma and the ratio of oxygen exchange by adjusting the oxygen partial pressure.

[0013] In the above scheme, oxygen is excited to generate oxygen plasma, wherein the excited species of the oxygen plasma include molecules, atoms and ions.

[0014] In the above solution, an amorphous oxide semiconductor channel film is prepared on a substrate by deposition or sputtering.

[0015] In the above scheme, the substrate is a material that does not react with the oxide semiconductor, and the substrate material includes silicon, silicon carbide, silicon on an insulating substrate, glass and sapphire.

[0016] In the above solution, the material of the amorphous oxide semiconductor film includes indium gallium zinc oxide, indium oxide, indium gallium oxide, zinc oxide and indium tin oxide.

[0017] (III) Beneficial effects

[0018] The technical solution of the embodiment of the present invention has at least the following beneficial effects:

[0019] (1) Plasma treatment is used. Based on the oxygen exchange phenomenon between oxygen plasma and oxygen-containing amorphous oxide semiconductor films, the amorphous oxide semiconductor channel can be regarded as a dynamic exchange network, which is conducive to the diffusion of hydrogen atoms out of the channel and reduces channel hydrogen defects.

[0020] (2) The use of oxygen-containing plasma for treatment is different from the traditional idea of ​​using thermal energy to achieve atomic diffusion, and avoids the damage to the channel caused by high temperature.

[0021] (3) Oxygen-containing plasma is used for treatment. No exogenous atoms are introduced into the oxide semiconductor channel, thus avoiding the introduction of new defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart of a plasma treatment method for an oxide semiconductor channel film according to an embodiment of the present invention is shown;

[0023] Figure 2 Schematically illustrates an embodiment of the present invention using 18 O plasma treatment process diagram of oxide semiconductor channel film;

[0024] Figure 3 Schematically shows an embodiment of the present invention 18 The change of oxygen intensity in the channel film represented by secondary ion mass spectrometry before and after O plasma treatment;

[0025] Figure 4 Schematically shows an embodiment of the present invention 18 Changes in hydrogen intensity in the channel film as measured by secondary ion mass spectrometry before and after O plasma treatment;

[0026] Figure 5 A schematic diagram of the structure of an IGZO bottom-gate TFT device according to an embodiment of the present invention is shown;

[0027] Figure 6 A diagram schematically shows a change in threshold voltage stability of an oxide semiconductor device after oxygen plasma treatment according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0029] Figure 1 A flow chart of a plasma treatment method for an oxide semiconductor channel film according to an embodiment of the present invention is shown.

[0030] like Figure 1As shown, the plasma treatment method for the oxide semiconductor channel film specifically includes operations S1 to S5.

[0031] In operation S1, an amorphous oxide semiconductor channel film is formed on a substrate to obtain an amorphous oxide semiconductor sample including the channel film.

[0032] In an embodiment of the present invention, an amorphous oxide semiconductor channel thin film may be prepared on a substrate by deposition or sputtering to obtain an amorphous oxide semiconductor sample including a channel thin film.

[0033] Exemplarily, the substrate is a material that does not react with the oxide semiconductor, for example, the substrate material may be silicon, silicon carbide, silicon on an insulating substrate, glass, sapphire, and the like.

[0034] For example, the material of the amorphous oxide semiconductor film may be indium gallium zinc oxide, indium oxide, indium gallium oxide, zinc oxide, indium tin oxide, and the like.

[0035] In operation S2, the amorphous oxide semiconductor sample including the channel film is placed in a reaction chamber of a plasma device, and the reaction chamber is evacuated.

[0036] In operation S3, reaction gas and auxiliary gas are introduced into the vacuumized reaction chamber.

[0037] Specifically, after the above operation S1 is completed, the generated amorphous oxide semiconductor channel film is placed in a reaction chamber, and the reaction chamber is evacuated, and then the reaction gas and the auxiliary gas are introduced into the reaction chamber.

[0038] Exemplarily, the reaction gas is oxygen, and the auxiliary gas is one or more of nitrogen and an inert gas.

[0039] In operation S4, the input power and gas partial pressure of the plasma device are adjusted for the first time to excite the reaction gas in the reaction chamber to generate plasma.

[0040] Specifically, the ignition process is completed by first adjusting the input power and oxygen partial pressure of the plasma device to excite oxygen to generate oxygen plasma. Plasma is generated by excitation, and the excitation method includes, for example, microwave excitation plasma, inductively coupled excitation plasma, cyclotron resonance excitation plasma, and radio frequency excitation plasma.

[0041] It should be noted that the oxygen plasma is generated by exciting oxygen ignition, wherein the excited species of the oxygen plasma include molecules, atoms and ions, etc., which can all achieve the reduction of the channel hydrogen concentration.

[0042] Through the embodiments of the present invention, oxygen-containing plasma is used for treatment, which is different from the traditional idea of ​​using thermal energy to achieve atomic diffusion, and avoids high temperature damage to the channel. For the oxide semiconductor channel, oxygen-containing plasma is used for treatment, and no exogenous atoms are introduced, thereby avoiding the introduction of new defects.

[0043] In operation S5, within the preset first time threshold, the input power and gas partial pressure of the plasma device are adjusted for the second time to change the density and energy of the plasma, so as to implement plasma processing of the amorphous oxide semiconductor channel film in the reaction chamber.

[0044] In an embodiment of the present invention, the plasma treatment of the amorphous oxide semiconductor channel film is performed by adjusting the parameter variables such as the input power of the plasma equipment, the gas partial pressure and the preset treatment time threshold.

[0045] Specifically, within a preset first time threshold, such as 3 minutes, 12 minutes, etc., the input power and gas partial pressure of the plasma device are adjusted for a second time to change the density and energy of the plasma, thereby realizing plasma post-treatment of the amorphous oxide semiconductor channel film, including: changing the density and energy of the oxygen plasma by adjusting the input power and oxygen partial pressure of the plasma device for a second time to obtain an oxygen-containing plasma environment; based on the oxygen-containing plasma environment, oxygen is exchanged between the oxygen plasma and the oxygen-containing amorphous oxide semiconductor film to realize plasma treatment of the amorphous oxide semiconductor channel film.

[0046] In an embodiment of the present invention, the density of oxygen plasma and the ratio of oxygen exchange are changed by adjusting the oxygen partial pressure.

[0047] Through the embodiments of the present invention, plasma processing is adopted. Based on the oxygen exchange phenomenon between oxygen plasma and oxygen-containing amorphous oxide semiconductor film, the amorphous oxide semiconductor channel film can be regarded as a dynamic exchange network, which is beneficial for the diffusion of hydrogen atoms out of the channel and reduces channel hydrogen defects.

[0048] Based on the above-mentioned plasma treatment method for oxide semiconductor channel film, the present invention proposes an embodiment. In this embodiment, the high energy of atoms in the oxygen plasma environment is used to achieve dynamic atomic exchange, thereby reducing the hydrogen content in the AOS film. The problems of traditional heat treatment diffusion and the introduction of doped atoms to passivate hydrogen defects are solved, and a new method for improving the quality of oxide semiconductor channel film is provided in terms of process.

[0049] For example, first, an indium gallium zinc oxide (IGZO) film is prepared by sputtering for 40 minutes on the surface of a silicon oxide (SiO2 / Si) sample on a silicon substrate. IGZO is usually used as a channel material to obtain a channel film of the IGZO / SiO2 / Si sample. The IGZO / SiO2 / Si sample containing the channel film is placed in a microwave plasma oxidation chamber, and the chamber is evacuated to a vacuum of <10 -4 Pa range; isotopic oxygen is introduced into the cavity after vacuuming 18 O2, gas pressure is 1kPa, after the ventilation is stopped, the microwave input power of the microwave plasma generator is adjusted to 600W for the first time, at this time, the microwave excites the isotope oxygen to glow, forming 18 O plasma.

[0050] Furthermore, the microwave input power and reaction gas pressure of the microwave plasma generator are adjusted for the second time, thereby changing 18 The energy and density of O plasma. 18 The IGZO / SiO2 / Si sample was post-treated with O plasma for 12 minutes. After the treatment, the microwave input power was turned off and the introduction of isotopic oxygen was stopped.

[0051] Furthermore, secondary ion mass spectrometry characterization was performed on the IGZO / SiO2 / Si samples that had been and had not been post-treated with microwave plasma. That is, in order to verify whether the amorphous oxide semiconductor film after plasma treatment in the above embodiment has achieved oxygen exchange, a specific description is given below.

[0052] This embodiment adopts 18 O2 isotope replacement routine 16 Take O2 as an example. Figure 2 As shown, Figure 2 Schematically illustrates an embodiment of the present invention using 18 O plasma treatment process diagram of oxide semiconductor channel film. Oxidation of silicon (Si 16 The surface of O2 / Si samples was prepared by sputtering InGaZnO (IGZ 16 O) film, and then IGZ 16 O / Si 16 The O2 / Si sample was placed in a microwave plasma oxidation chamber and the chamber was evacuated to a vacuum of <10 -4 Pa range, isotopic oxygen is introduced into the chamber after vacuuming 18 O2, gas pressure is 1kPa, after the ventilation is stopped, the microwave input power of the microwave plasma generator is adjusted to 600W for the first time, at this time, the microwave excites the isotope oxygen to glow, forming 18O plasma. Further, the microwave input power and reaction gas pressure of the microwave plasma generator are adjusted for the second time to change 18 The energy and density of O plasma. 18 O plasma on IGZ 16 O / Si 16 The O2 / Si sample was post-treated for 12 minutes to obtain IGZ 16，18 O / Si 16 O2 / Si, after the end, turn off the microwave input power and stop introducing isotope oxygen.

[0053] Figure 3 Schematically shows an embodiment of the present invention 18 Secondary ion mass spectrometry showing the change in oxygen intensity in the channel film before and after O plasma treatment.

[0054] like Figure 3 As shown, without microwave plasma treatment, the IGZO film 18 The intensity of O is almost 0, while 16 O intensity distribution is uniform, and it can be seen that there is almost no 18 O, all by 16 O composition; after microwave plasma treatment, the upper surface area of ​​IGZO film 18 O strength increased significantly, 16 O strength is significantly reduced. Figure 3 As shown, oxygen exchange occurred in the IGZO film from the upper surface to the lower interface during microwave plasma treatment.

[0055] Figure 4 Schematically shows an embodiment of the present invention 18 Changes in hydrogen intensity in the channel film represented by secondary ion mass spectrometry before and after O plasma treatment.

[0056] like Figure 4 As shown in the figure, the hydrogen intensity changes after microwave plasma post-treatment. It can be seen that the intensity of both OH ions and H ions in the IGZO film is reduced after plasma treatment, which also proves that plasma treatment is conducive to the outward diffusion of hydrogen atoms and reduces the hydrogen concentration in the channel. It should be noted that in this embodiment, the temperature during microwave plasma post-treatment is <300°C, which is much lower than the temperature required for high-temperature annealing.

[0057] Based on the above-mentioned plasma processing method for an oxide semiconductor channel film, the present invention provides another embodiment.

[0058] For example, first, an indium gallium zinc oxide (IGZO) film is prepared by sputtering for 40 minutes on the surface of a silicon oxide (SiO2 / Si) sample on a silicon substrate. IGZO is usually used as a channel material to obtain a channel film of the IGZO / SiO2 / Si sample. The IGZO / SiO2 / Si sample containing the channel film is placed in a microwave plasma oxidation chamber, and the chamber is evacuated to a vacuum of <10 -4 Pa range; oxygen is introduced into the vacuum chamber at a pressure of 1 kPa. After the ventilation is stopped, the microwave input power of the microwave plasma generator is adjusted to 600 W for the first time. At this time, microwaves excite the isotope oxygen to glow and form oxygen plasma.

[0059] Furthermore, the microwave input power and reaction gas pressure of the microwave plasma generator were adjusted for the second time, thereby changing the energy and density of the oxygen plasma. The IGZO / SiO2 / Si sample was post-treated with oxygen plasma for 3 minutes, after which the microwave input power was turned off and the oxygen was stopped.

[0060] In an embodiment of the present invention, positive bias and negative bias threshold stability tests were conducted on IGZO / SiO2 / Si samples that had been and had not been post-treated with microwave plasma, and indium tin oxide (ITO) electrodes were sputtered simultaneously.

[0061] Figure 5 The structure of an IGZO bottom-gate TFT device according to an embodiment of the present invention is schematically shown. Figure 6 A diagram schematically shows a change in threshold voltage stability of an oxide semiconductor device after oxygen plasma treatment according to an embodiment of the present invention.

[0062] like Figure 5 As shown in the figure, indium tin oxide (ITO) electrodes were sputtered on IGZO / SiO2 / Si samples that had been and had not been post-treated with microwave plasma to obtain bottom-gate TFT devices. Positive bias and negative bias threshold stability tests were carried out on the bottom-gate TFT devices that had been post-treated with microwave plasma and the bottom-gate TFT devices that had not been post-treated with microwave plasma.

[0063] like Figure 6 As shown, the threshold voltage offset of the bottom-gate TFT device after microwave plasma treatment is significantly reduced, which shows that microwave plasma treatment reduces the hydrogen concentration in the channel and improves the quality of the amorphous oxide semiconductor channel.

[0064] Through the embodiments of the present invention, the oxygen exchange phenomenon between oxygen plasma and oxygen-containing amorphous oxide semiconductor film is utilized to promote the diffusion of hydrogen atoms out of the channel and reduce channel hydrogen defects. In addition, the embodiments of the present invention break through the conventional method of removing hydrogen atoms, avoid new defects caused by high temperature and the introduction of exogenous atoms, and meet the "low temperature" requirements of the industry.

[0065] It will be appreciated by those skilled in the art that, although the present invention has been shown and described with reference to specific exemplary embodiments of the present invention, it will be appreciated by those skilled in the art that, without departing from the spirit and scope of the present invention as defined by the appended claims and their equivalents, various changes in form and detail may be made to the present invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined not only by the appended claims, but also by the equivalents of the appended claims.

[0066] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A plasma treatment method for an oxide semiconductor channel film, characterized in that: The method comprises: preparing an amorphous oxide semiconductor channel film on a substrate to obtain an amorphous oxide semiconductor sample containing the channel film; Placing the amorphous oxide semiconductor sample containing the channel film into a reaction chamber of a plasma device, and performing a vacuum treatment on the reaction chamber; Introducing reaction gas and auxiliary gas into the vacuumized reaction chamber; The input power and gas partial pressure of the plasma device are adjusted for the first time to excite the reaction gas in the reaction chamber to generate plasma; Within a preset first time threshold, the input power and gas partial pressure of the plasma device are adjusted for a second time to change the density and energy of the plasma, thereby achieving plasma processing of the amorphous oxide semiconductor channel film in the reaction chamber.

2. The plasma treatment method for an oxide semiconductor channel film according to claim 1, characterized in that: The reaction gas is oxygen, and the auxiliary gas is one or more of nitrogen and inert gas.

3. The plasma treatment method for an oxide semiconductor channel film according to claim 1 or 2, characterized in that: The first step of adjusting the input power and gas partial pressure of the plasma device to excite the reaction gas in the reaction chamber to generate plasma includes: By first adjusting the input power and oxygen partial pressure of the plasma device, oxygen is excited to generate oxygen plasma.

4. The plasma treatment method for an oxide semiconductor channel film according to claim 3, characterized in that: The second step of adjusting the input power and gas partial pressure of the plasma device to change the density and energy of the plasma and realizing the plasma treatment of the amorphous oxide semiconductor channel film in the reaction chamber includes: By adjusting the input power and oxygen partial pressure of the plasma equipment for a second time, the density and energy of the oxygen plasma are changed to obtain an oxygen-containing plasma environment; Based on the oxygen-containing plasma environment, the plasma treatment of the amorphous oxide semiconductor channel film is achieved by oxygen exchange between the oxygen plasma and the oxygen-containing amorphous oxide semiconductor film.

5. The plasma treatment method for an oxide semiconductor channel film according to claim 1, characterized in that: The plasma is generated by excitation, and the excitation methods include microwave excitation plasma, inductively coupled excitation plasma, cyclotron resonance excitation plasma and radio frequency excitation plasma.

6. The plasma treatment method for an oxide semiconductor channel film according to claim 4, characterized in that: The method comprises: adjusting the input power and oxygen partial pressure of the plasma device for the second time to change the density and energy of the oxygen plasma to obtain an oxygen-containing plasma environment, including: The density of the oxygen plasma and the ratio of the oxygen exchange are changed by adjusting the oxygen partial pressure.

7. The plasma treatment method for an oxide semiconductor channel film according to claim 3, characterized in that: The excited oxygen ignition generates oxygen plasma, wherein the excited species of the oxygen plasma include molecules, atoms and ions.

8. The plasma treatment method for an oxide semiconductor channel film according to claim 1, characterized in that: The amorphous oxide semiconductor channel film is prepared on the substrate by deposition or sputtering.

9. The plasma treatment method for an oxide semiconductor channel thin film according to claim 1 or 8, characterized in that: The substrate is a material that does not react with oxide semiconductors, and the substrate material includes silicon, silicon carbide, silicon on an insulating substrate, glass, and sapphire.

10. The plasma treatment method for an oxide semiconductor channel film according to claim 1, characterized in that: The material of the amorphous oxide semiconductor film includes indium gallium zinc oxide, indium oxide, indium gallium oxide, zinc oxide and indium tin oxide.

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