A multi-stage annealing process for ITO thin films

Abstract

This invention belongs to the field of semiconductor optoelectronic device manufacturing technology and discloses a multi-stage annealing process for ITO thin films, including the following steps: Step 1: Under high vacuum protection, the furnace temperature is raised from room temperature to a first temperature T1 and held for a first time; Step 2: The furnace temperature is raised to a higher second temperature T2 and held for a second time, without the need for oxygen introduction during the second holding stage; Step 3: While maintaining the second temperature T2, a third holding stage is performed, and oxygen is introduced during the third holding stage; Step 4: A controllable cooling process is performed, which includes at least a slow cooling stage under the oxygen atmosphere and a rapid cooling stage under an inert gas or extremely low oxygen concentration atmosphere. This invention achieves precise staged control of the ITO thin film crystallization process, oxygen vacancy filling, and interfacial reactions by precisely controlling the oxygen partial pressure and cooling rate at different temperature stages.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor optoelectronic device manufacturing technology, specifically relating to a multi-stage annealing process for ITO thin films. Background Technology

[0002] In LED chip manufacturing, after depositing an ITO thin film on a P-type GaN layer, annealing is necessary to reduce its resistivity, increase its transmittance, and improve its ohmic contact characteristics with P-GaN. Traditional ITO annealing processes are typically performed in a single atmosphere (such as pure nitrogen (N2), pure oxygen (O2), or a nitrogen-oxygen mixture) at one or a few fixed temperature steps. The main drawbacks of this method are as follows: 1. Lattice oxygen deficiency and oxygen vacancies; 2. Overgrowth of grains and surface roughening; 3. Narrow process window; 4. Interface oxidation problems. Summary of the Invention

[0003] To address the aforementioned issues, this invention develops a multi-stage annealing process for ITO thin films. By precisely controlling the oxygen partial pressure and cooling rate at different temperature stages, it achieves precise staged control of the ITO thin film crystallization process, oxygen vacancy filling, and interfacial reactions.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A multi-stage annealing process for ITO thin films includes the following steps:

[0006] Step 1: Place the LED chip substrate with deposited ITO thin film into an annealing furnace. Under high vacuum protection, raise the furnace temperature from room temperature to a first temperature T1 and perform a first heat preservation.

[0007] Step 2: Raise the furnace temperature to a higher second temperature T2 and perform a second heat preservation. No oxygen needs to be introduced during the second heat preservation stage.

[0008] Step 3: While maintaining the second temperature T2, perform a third heat preservation, and introduce oxygen during the third heat preservation stage;

[0009] Step 4: Conduct a controlled cooling process, which includes at least a slow cooling phase in the oxygen atmosphere and a rapid cooling phase in an inert gas or extremely low oxygen concentration atmosphere.

[0010] Preferably, the high vacuum is 0.07 torr.

[0011] Preferably, the first temperature T1 is 150℃~300℃, and the first temperature heating rate is 1℃ / s~5℃ / s.

[0012] Preferably, the first heat preservation time is 30s to 60s.

[0013] Preferably, the second temperature T2 is 500℃~600℃, and the heating rate of the second temperature is 5℃ / s~10℃ / s.

[0014] Preferably, the second heat preservation time is 50s to 150s.

[0015] Preferably, the oxygen flow rate is 0.5 sccm to 3 sccm.

[0016] Preferably, the third heat preservation time is 100s~150s.

[0017] Preferably, the controllable cooling process in step four specifically includes:

[0018] Slow cooling phase: The temperature is reduced from T2 to the intermediate temperature T3 at a rate of R3, and the oxygen atmosphere is maintained during this phase;

[0019] Rapid cooling phase: When the temperature drops to T3 or below, the atmosphere is switched to an inert gas or a mixture with an oxygen volume fraction of less than 0.1%, and cooled to room temperature at a rate of R4.

[0020] Preferably, the rate R3 is 1℃ / s to 5℃ / s, the rate R4 is 5℃ / s to 15℃ / s, and the intermediate temperature T3 is 300℃ to 400℃.

[0021] Preferably, the inert gas is N2.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention achieves precise staged control of the ITO thin film crystallization process, oxygen vacancy filling, and interfacial reaction by precisely controlling the oxygen partial pressure and cooling rate at different temperature stages. Through synergistic optimization of performance, it effectively improves ohmic contact and enhances light efficiency. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0025] Figure 1 These are experimental resistance values ​​after annealing in an embodiment of the present invention;

[0026] Figure 2 These are the experimental values ​​of light transmittance after annealing in an embodiment of the present invention;

[0027] Figure 3 The experimental values ​​of the working voltage for the photoelectric properties of the product after annealing according to an embodiment of the present invention;

[0028] Figure 4The values ​​for the photoelectric properties and luminous intensity of the product after annealing according to an embodiment of the present invention are experimental values. Detailed Implementation

[0029] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0030] The present invention provides a multi-stage annealing process for ITO thin films, which specifically includes the following steps:

[0031] Step 1: Wafer Loading and Initial Heating. The LED chip substrate with deposited ITO thin film is placed in an annealing furnace. The annealing furnace is evacuated to a high vacuum V1, and the furnace temperature is raised from room temperature to a first target temperature T1 at a first heating rate R1. The high vacuum V1 is 0.07 torr, the first heating rate R1 is 1℃ / s~5℃ / s, and the first target temperature T1 is 150℃~300℃.

[0032] Step Two: First Incubation Section (Low-Temperature Crystallization and Solvent Evaporation Section), maintain the temperature at T1 for a period of time t1, while simultaneously maintaining a vacuum atmosphere below V1. The first incubation time t1 is 30s~60s.

[0033] The main purpose of this stage is to induce the amorphous structure in the ITO film to begin its transformation into a crystalline state and to fully volatilize organic matter and solvents.

[0034] Step 3: Second heating stage and second holding stage (high-temperature recrystallization and grain optimization stage). While maintaining a vacuum atmosphere below V1, the furnace temperature is raised to the second target temperature T2 at a second heating rate R2. After reaching T2, the second holding stage is performed for a time t2. While keeping T2 constant, oxygen A0 is not introduced during this stage. The second heating rate R2 is 5℃ / s~10℃ / s, the second target temperature T2 is 500℃~600℃, the second holding time t2 is 50s~150s, and the oxygen A0 is 0 sccm.

[0035] The key to this stage is to ensure sufficient recrystallization and grain growth while suppressing excessive grain growth and surface roughening by preventing the introduction of oxygen.

[0036] Step 4: Third Insulation Stage (Precise Oxygen Vacancy Filling Stage): After completing the second insulation stage, while maintaining a vacuum atmosphere below V1 and keeping the temperature T2 constant, a certain amount of oxygen A1 is introduced. The temperature and pressure are maintained under this oxygen atmosphere for a period of time t3. The time t3 is 100s~150s, and the oxygen A1 concentration is 0.5sccm~3sccm.

[0037] The core objective of this stage is to utilize the oxygen ion mobility under high temperature and pressure to quickly and effectively fill some of the oxygen vacancies generated in the previous stage, thereby reducing resistivity and improving the chemical stability and optical transmittance of the thin film without causing significant secondary growth of grains.

[0038] Step 5: Controlled Cooling and Oxygenation Stage (Interface Stabilization and Stress Relief Stage). After completing the third insulation stage, the cooling process begins. This cooling process is divided into two sub-stages:

[0039] 1. Slow cooling phase: The temperature is reduced from T2 to an intermediate temperature T3 at a first cooling rate R3. During this slow cooling process, an oxygen A1 atmosphere is maintained. The first cooling rate R3 is 1℃ / s to 5℃ / s, and the temperature T3 is 300℃ to 400℃.

[0040] This slow oxygen-passing cooling process allows oxygen to continue to permeate and stabilize the film structure, while slowly releasing the thermal stress within the film to prevent crack formation.

[0041] 2. Rapid cooling phase: When the temperature drops below T3, the cooling rate is increased to R4, and the gas is switched to pure N2 or an N2 atmosphere with extremely low oxygen concentration (<0.1%) until it drops to room temperature. The third cooling rate R4 is 5℃ / s to 15℃ / s.

[0042] Cutting off the oxygen supply at this stage at a lower temperature can effectively prevent potential oxidation of the ITO / GaN interface by oxygen at low temperatures, ensuring the performance of the ohmic contact.

[0043] Example:

[0044] Using the above method, the key parameters are set as follows: high vacuum V1 is 0.07 torr, first heating rate R1 is 3℃ / s, first target temperature T1 is 250℃, holding time t1 is 30s, second heating rate R2 is 10℃ / s, second target temperature T2 is 530℃, holding time t2 is 120s, holding time t3 is 100s, oxygen A0 is 0 sccm, oxygen A1 is 2 sccm, cooling rate R3 is approximately -5℃ / s, target temperature T3 is 400℃, and cooling rate R3 is approximately 10℃ / s. When the cooling rate is uncontrollable, it can also be controlled by setting the time. The following results are obtained:

[0045] 1. The experiment used a 2-inch BK7 substrate with a 90nm thick ITO film, and the resistivity and transmittance were consistent. For example... Figure 1 , Figure 2 After annealing with the above parameters, the resistance is reduced by 3.58Ω / hole compared to the base, and the transmittance is increased by 1.0%.

[0046] 2. The experiment used wafers from the same epitaxial furnace and circuit, with consistent chip manufacturing processes. Before annealing, they were separated in pairs and annealed separately before being combined into batches to ensure consistency in chip manufacturing processes. For example... Figure 3 , Figure 4 By leveraging photoelectric properties, the operating voltage decreased by 0.008V, while the luminous intensity increased by 0.29mW.

[0047] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A multi-stage annealing process for ITO thin films, characterized in that: Includes the following steps: Step 1: Place the LED chip substrate with deposited ITO thin film into an annealing furnace. Under high vacuum protection, raise the furnace temperature from room temperature to a first temperature T1 and perform a first heat preservation. Step 2: Raise the furnace temperature to a higher second temperature T2 and perform a second heat preservation. No oxygen needs to be introduced during the second heat preservation stage. Step 3: While maintaining the second temperature T2, perform a third heat preservation, and introduce oxygen during the third heat preservation stage; Step 4: Conduct a controlled cooling process, which includes at least a slow cooling phase in the oxygen atmosphere and a rapid cooling phase in an inert gas or extremely low oxygen concentration atmosphere, specifically including: Slow cooling phase: The temperature is reduced from T2 to the intermediate temperature T3 at a rate of R3, and the oxygen atmosphere is maintained during this phase; The rate R3 is 1℃ / s to 5℃ / s; the intermediate temperature T3 is 300℃ to 400℃. Rapid cooling phase: When the temperature drops to T3 or below, the atmosphere is switched to an inert gas or a mixture with an oxygen volume fraction of less than 0.1%, and the temperature is reduced to room temperature at a rate R4; the rate R4 is 5℃ / s to 15℃ / s.

2. The multi-stage annealing process for ITO thin films as described in claim 1, characterized in that: The high vacuum is 0.07 torr.

3. The multi-stage annealing process for ITO thin films as described in claim 1, characterized in that: The first temperature T1 is 150℃~300℃, and the heating rate of the first temperature is 1℃ / s~5℃ / s.

4. The multi-stage annealing process for ITO thin films as described in claim 1, characterized in that: The first heat preservation time is 30s~60s.

5. The multi-stage annealing process for ITO thin films as described in claim 1, characterized in that: The second temperature T2 is 500℃~600℃, and the heating rate of the second temperature is 5℃ / s~10℃ / s.

6. The multi-stage annealing process for ITO thin films as described in claim 1, characterized in that: The second heat preservation time is 50s~150s.

7. The multi-stage annealing process for ITO thin films as described in claim 1, characterized in that: The oxygen flow rate is 0.5 sccm to 3 sccm.

8. The multi-stage annealing process for ITO thin films as described in claim 1, characterized in that: The third heat preservation time is 100s~150s.

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