LED substrate material fine polishing method

Abstract

The invention discloses an LED substrate material fine polishing method which comprises the steps of substrate surface pretreatment, substrate surface three-stage polishing, in-situ optical surface state monitoring, dynamic chemical environment regulation and control, ultrasonic-assisted nano pollutant removal and vacuum gradient drying and surface energy verification, and relates to the technical field of semiconductor material processing. According to the fine polishing method for the LED substrate material, damage can be eliminated layer by layer through gradient material diamond-aluminum oxide-colloidal silicon three-stage abrasive progressive, atomic scale flatness can be achieved through surface hydrolysis softening and mechanical friction of colloidal silicon in an alkaline environment, atomic scale fine polishing is achieved, and the quality of the LED substrate material is improved. Potential of hydrogen (pH) switching is carried out on the polishing solution in the rough polishing stage and the fine polishing stage, chemical and mechanical dynamic can be coordinated, then the mechanical cutting efficiency of rough polishing is enhanced, the cutting resistance of fine polishing is reduced, sodium dodecyl benzene sulfonate is added into the fine polishing solution, the agglomeration of grinding materials can be reduced, and the dispersion uniformity is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material processing technology, specifically to a method for fine polishing LED substrate materials. Background Technology

[0002] LED substrate material is the substrate material used to grow LED epitaxial layers. Its main function is to support and fix the epitaxial layer, which has an important impact on the performance and quality of LED devices.

[0003] Polishing is an important step in the substrate material manufacturing process. Polishing can further remove the residual damage layer on the processing surface to make it meet the usage standards. Secondly, polishing is also to ensure the quality of the substrate material and meet the requirements of semiconductor device manufacturing.

[0004] Currently, there are generally three materials available as substrates: sapphire (Al2O3), silicon (Si), and silicon carbide (SiC). All three share the characteristic of high hardness (Mohs hardness ≥ 9). Traditional polishing methods for these hard materials have the following drawbacks:

[0005] 1. Bottlenecks in hard material processing:

[0006] Polishing with a single abrasive can easily lead to surface / subsurface damage (microcracks > 100 nm), and there is a contradiction between material removal rate (MRR) and surface quality.

[0007] Mechanical polishing leaves residual scratches (Ra > 0.5 nm), while chemical polishing is inefficient and difficult to control the integrity of the pattern structure.

[0008] 2. Insufficient process synergy

[0009] Chemical-mechanical imbalance: The fixed acid and alkaline environment in the traditional CMP process cannot adapt to the different needs of rough polishing (mechanical removal) and fine polishing (chemical etching), resulting in low efficiency or over-etching of the surface;

[0010] 3. Lack of process control

[0011] Open-loop operation risks: lack of real-time surface monitoring, reliance on experience to judge the polishing endpoint, resulting in a pattern edge collapse rate >15% or over-polishing (deepening of the damaged layer).

[0012] To avoid the aforementioned problems, a fine polishing method for LED substrate materials is proposed to solve the existing issues. Summary of the Invention

[0013] To address the shortcomings of existing technologies, this invention provides a method for fine polishing LED substrate materials, which solves the problems of traditional polishing methods being susceptible to bottlenecks in hard material processing, insufficient process synergy, and lack of process control.

[0014] To achieve the above objectives, the present invention provides a method for fine polishing of LED substrate materials, specifically comprising the following steps:

[0015] Step 1: Substrate surface pretreatment: Perform ultrasonic cleaning on the original substrate;

[0016] Step 2, Three-stage polishing of substrate surface: The cleaned substrate is subjected to mechanical rough polishing, transition polishing and mechanical fine polishing in sequence;

[0017] Step 3: In-situ optical surface condition monitoring: A laser interferometer is used to scan and monitor the substrate surface during the fine polishing stage to monitor the fine polishing status;

[0018] Step 4: Dynamic chemical environment control; different removal mechanisms for materials at different polishing stages;

[0019] Step 5, Ultrasonic-assisted removal of nano-contaminants: The finished substrate after polishing is ultrasonically cleaned to remove nano-sized abrasive particles adsorbed on the surface.

[0020] Step 6: Vacuum gradient drying and surface energy verification: Perform gradient drying on the cleaned finished product and conduct acceptance testing on its surface energy.

[0021] Preferably, the ultrasonic cleaning in step one uses an acetone-isopropanol mixture as the cleaning solution.

[0022] Preferably, in step two, the mechanical coarse polishing uses a polishing slurry containing diamond as an abrasive as the coarse polishing medium, wherein the diamond abrasive particle size is 3-5μm.

[0023] Preferably, the transition polishing in step two uses a polishing slurry containing α-alumina abrasive as the polishing medium, wherein the α-alumina abrasive has a particle size of 0.2 μm.

[0024] Preferably, in step two, the mechanical polishing uses a polishing slurry containing 60nm colloidal silicon particles as the polishing medium, wherein the polishing slurry containing 60nm colloidal silicon particles contains 0.2wt% sodium dodecyl sulfonate as a surfactant.

[0025] Preferably, in step three, the surface roughness is measured in real time using a 632.8nm wavelength laser interferometer, and polishing is automatically terminated when the roughness Ra value is ≤0.3nm.

[0026] Preferably, in step four, the pH value of the polishing solution is controlled at 4.0-5.0 in the rough polishing stage and adjusted to 10.0-11.0 in the fine polishing stage.

[0027] Preferably, step five uses a cleaning solution containing 0.05 mol / L disodium ethylenediaminetetraacetate and cleans the substrate under ultrasonic conditions at 40 kHz.

[0028] Preferably, the final vacuum drying pressure in step six is ​​≤10. -3 Pa.

[0029] Preferably, the surface energy verification standard in step six is: surface contact angle detection threshold ≤ 5°.

[0030] Beneficial effects:

[0031] This invention provides a method for fine polishing LED substrate materials. Compared with existing technologies, it has the following advantages:

[0032] Beneficial effects:

[0033] (1) The LED substrate material polishing method uses a three-level abrasive gradient material diamond-alumina-colloidal silicon to eliminate damage layer by layer. In addition, colloidal silicon can achieve atomic-scale flatness through surface hydrolysis and mechanical friction in an alkaline environment, thus achieving atomic-level polishing.

[0034] (2) The method for polishing LED substrate material by switching the pH of the polishing liquid in the coarse polishing stage and the fine polishing stage can enable chemical and mechanical dynamics to work together, thereby enhancing the mechanical removal efficiency of coarse polishing and reducing the cutting resistance of fine polishing.

[0035] Secondly, adding sodium dodecylbenzenesulfonate to the fine polishing slurry can reduce abrasive agglomeration and improve dispersion uniformity.

[0036] (3) The method for polishing LED substrate material uses a laser interferometer to measure the roughness value in real time, which can avoid the problem of excessive risk of over-polishing caused by human experience judgment, and can avoid pattern deformation by dynamically adjusting the pressure and rotation speed through roughness data. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0039] Please see Figure 1 This invention provides a technical solution: a method for fine polishing LED substrate materials, specifically including the following steps:

[0040] Step 1: Substrate surface pretreatment

[0041] First, the cut substrate is immersed in a 60°C acetone-isopropanol mixed solution (volume ratio 1:1) for ultrasonic cleaning for 10 minutes to remove organic contaminants and cutting debris. After cleaning, the surface is immediately dried with high-purity nitrogen to ensure that no liquid residue remains before proceeding to the next process.

[0042] Step 2: Mechanical coarse polishing with first-grade diamond abrasive grains

[0043] The pretreated substrate was loaded onto a rotary polishing disk and polished for 20 minutes at a pressure of 0.35 MPa and a speed of 75 rpm using a suspension containing 3 μm diamond abrasive particles (concentration 20 wt%). During this process, the sharp edges of the diamond particles efficiently removed the micron-level unevenness of the surface, reducing the surface roughness from the initial Ra>200 nm to the range of 50-80 nm. When the surface gloss reached a mirror effect, it indicated that the transition to the transition polishing stage was possible.

[0044] Secondary alumina abrasive transition polishing

[0045] Following the initial rough polishing, the surface was replaced with a 0.2μm α-type alumina abrasive suspension. The polishing pressure was reduced to 0.1MPa, the rotation speed was adjusted to 50rpm, and the process was continued for 15 minutes. During this stage, the rolling grinding action of the alumina particles eliminated the scratches produced by diamond polishing and further reduced the roughness to Ra<10nm. When a white light interferometer detected no obvious macroscopic defects on the surface, the transition polishing was considered complete.

[0046] Grade III colloidal silica chemical mechanical polishing

[0047] Based on the transition polishing, a polishing slurry containing 60nm colloidal silicon particles was used, with 0.2wt% sodium dodecyl sulfonate added as a surfactant. In the initial stage, the slurry was run at a pressure of 0.05MPa and a speed of 30rpm. As the polishing process progressed, the pressure was gradually reduced to 0.01MPa and the speed was reduced to 10rpm. During this process, the colloidal silicon particles were removed at the atomic level under the synergistic effect of chemical corrosion and mechanical friction. The processing time was about 40 minutes.

[0048] Step 3: In-situ optical surface condition monitoring

[0049] During the fine polishing stage, a laser interferometer is used to scan and monitor the surface. Ra value data is collected every 2 minutes. When Ra is ≤0.3nm for three consecutive measurements, the polishing termination program is automatically triggered.

[0050] If the polishing time exceeds 45 minutes and the target is not met, an alarm will be issued to check the abrasive consumption status. This monitoring step ensures that the surface quality is precisely controlled and avoids over-polishing that could lead to deformation of the graphic structure.

[0051] Step 4: Dynamic Chemical Environment Regulation

[0052] Based on the differences in material removal mechanisms at different polishing stages, oxalic acid solution is injected into the polishing slurry during the rough polishing stage to stabilize the pH at 4.5, thereby enhancing the mechanical removal efficiency.

[0053] After entering the fine polishing stage, the solution is switched to tetramethylammonium hydroxide to raise the pH to 10.5, which promotes the surface hydrolysis and softening reaction.

[0054] Acid-base switching is controlled in real time via online sensors;

[0055] Step 5: Ultrasonic-assisted removal of nano-pollutants

[0056] Immediately after polishing, the substrate was moved into a cleaning tank containing 0.05 mol / L disodium ethylenediaminetetraacetate and treated with 40 kHz ultrasound for 8 minutes. The cavitation effect generated by the ultrasound caused the nano-sized abrasive particles adsorbed on the surface to detach.

[0057] Step Six: Vacuum Gradient Drying and Surface Energy Verification

[0058] After cleaning, the substrate is first purged with 0.2MPa nitrogen to remove surface droplets, and then placed in a vacuum drying chamber for three-stage drying: the first stage is to evaporate the main body moisture by maintaining it at -0.08MPa and 25°C for 5 minutes.

[0059] The second stage involves heating to 40°C and maintaining a vacuum of -0.095 MPa for 3 minutes.

[0060] The third stage involves treating the area at 60℃ and -0.1MPa for 2 minutes to completely remove adsorbed water molecules.

[0061] Finally, the surface energy was verified using a contact angle meter, and a water droplet contact angle of ≤5° was considered acceptable.

[0062] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, the phrase "comprising an element defined as..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0063] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for fine polishing LED substrate materials, characterized in that: Specifically, the following steps are included: Step 1: Substrate surface pretreatment: Perform ultrasonic cleaning on the original substrate; Step 2, Three-stage polishing of substrate surface: The cleaned substrate is subjected to mechanical rough polishing, transition polishing and mechanical fine polishing in sequence; Step 3: In-situ optical surface condition monitoring: A laser interferometer is used to scan and monitor the substrate surface during the fine polishing stage to monitor the fine polishing status; Step 4: Dynamic chemical environment control; different removal mechanisms for materials at different polishing stages; Step 5, Ultrasonic-assisted removal of nano-contaminants: The finished substrate after polishing is ultrasonically cleaned to remove nano-sized abrasive particles adsorbed on the surface. Step 6: Vacuum gradient drying and surface energy verification: Perform gradient drying on the cleaned finished product and conduct acceptance testing on its surface energy.

2. The method for fine polishing LED substrate material according to claim 1, characterized in that: The ultrasonic cleaning in step one uses an acetone-isopropanol mixture as the cleaning solution.

3. The method for fine polishing LED substrate material according to claim 1, characterized in that: The mechanical rough polishing in step two uses a polishing slurry containing diamond as an abrasive as the rough polishing medium, wherein the diamond abrasive particle size is 3-5μm.

4. The method for fine polishing LED substrate material according to claim 1, characterized in that: The transition polishing in step two uses a polishing slurry containing α-alumina abrasive as the polishing medium, wherein the α-alumina abrasive has a particle size of 0.2 μm.

5. The method for fine polishing LED substrate material according to claim 1, characterized in that: The mechanical polishing in step two uses a polishing slurry containing 60nm colloidal silicon particles as the polishing medium, wherein 0.2wt% sodium dodecyl sulfonate is added to the polishing slurry containing 60nm colloidal silicon particles as a surfactant.

6. The method for fine polishing LED substrate material according to claim 1, characterized in that: Step three involves measuring the surface roughness in real time using a 632.8nm wavelength laser interferometer, and automatically terminating the polishing process when the roughness Ra value is ≤0.3nm.

7. The method for fine polishing LED substrate material according to claim 1, characterized in that: In step four, the pH value of the polishing solution is controlled at 4.0-5.0 during the rough polishing stage and adjusted to 10.0-11.0 during the fine polishing stage.

8. The method for fine polishing LED substrate material according to claim 1, characterized in that: Step five involves cleaning the substrate using a cleaning solution containing 0.05 mol / L disodium ethylenediaminetetraacetate and under ultrasonic conditions at 40 kHz.

9. The method for fine polishing LED substrate material according to claim 1, characterized in that: The final pressure of vacuum drying in step six is ​​≤10. -3 Pa.

10. The method for fine polishing LED substrate material according to claim 1, characterized in that: The surface energy verification standard in step six is: the surface contact angle detection threshold is ≤5°.

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