Treatment method for improving adsorption pollution of light emitting diode

Abstract

The invention relates to a treatment method for improving adsorption pollution of a light-emitting diode, which belongs to the technical field of light-emitting diodes, and fully and effectively removes residual hydroxyl radicals or other pollutants on the surface of a chip in the chip manufacturing process through the steps of vacuum high-temperature baking and plasma cleaning. Therefore, the glue gas adsorption chemical reaction of the chip in the solid crystal baking step is avoided, and the phenomena of chip pollution, difficulty in wire welding and A stripping are avoided. According to the scheme, the technology is simple, no chemical solution is used in the technological process, secondary pollution or chip corrosion damage cannot be caused to the chip, and high feasibility and universality are achieved.

Description

Technical Field

[0001] The present invention relates to a treatment method for improving the adsorption pollution of light-emitting diodes, belonging to the technical field of light-emitting diodes. Background Art

[0002] In recent years, due to their small size, energy saving, long lifespan, high brightness and other characteristics, light-emitting diodes have been widely used in various fields such as lighting, display, communication, decoration, etc. When in use, the light-emitting diode chips need to be fixed on the encapsulation bracket with die bonding glue, and the die bonding glue is cured by baking to fix the chips and form light-emitting diode devices. The hydroxyl small molecule cross-linking agent contained in the die bonding glue has a short molecular chain and a low boiling point, and volatilizes during the heating and curing process without participating in the reaction. At the same time, during the manufacturing process of light-emitting diode chips, multiple photolithography, developing, waxing, dewaxing and other chemical processes are required, and it is very easy to leave pollutants or functional groups such as hydroxyl groups on the surface of the chip electrodes. When the hydroxyl-containing small molecule cross-linking agent volatilized from the die bonding glue contacts the hydroxyl groups remaining on the electrode surface, the oxygen atom on the hydroxyl forms a hydrogen bond with the hydrogen on another hydroxyl. Subsequently, some hydrogen bonds are converted into covalent bonds and a water molecule is removed. The generated water molecules are discharged with the hot air in the oven under high-temperature baking. As time goes by, more and more cross-linking agents react chemically with the hydroxyl groups remaining on the electrode surface. Eventually, a layer of die bonding glue pollutants containing C, O, and Si is produced on the chip surface, which hinders the fusion of the gold wires during chip wire bonding, resulting in abnormal phenomena such as difficult wire bonding, virtual soldering, and A detachment. Therefore, how to remove the hydroxyl groups on the chip surface cleanly plays a crucial role in the normal use of the chip die bonding and wire bonding processes.

[0003] Chinese Patent Document CN107731981A discloses a method for manufacturing a nitride semiconductor light-emitting element. This method sets an adsorption material that is more likely to adsorb glue gas on the non-electrode area of the laminate to improve the glue gas adsorption phenomenon on the electrode surface. Although this inventive method has a certain improvement effect on glue gas adsorption, the manufacturing process is complex and the glue gas adsorption on the electrode surface cannot be completely avoided, having certain technical limitations.

[0004] Chinese Patent Document CN111162148A discloses an anti-glue gas LED chip and its manufacturing method. This method immerses the light-emitting structure in an alkaline ionization neutralization solution containing phosphorus and sodium, thereby forming an ionization neutralization layer on the electrode surface to improve the chip glue gas adsorption phenomenon. This method has a simple process, but the chemical solution cleaning method used in this invention is prone to secondary pollution and may corrode the electrode or the chip structure material. Therefore, its application scenario is limited.

[0005] In view of this, it is necessary to study a highly versatile, simple and effective process method to process light-emitting diode chips and avoid the phenomenon of glue absorption during die bonding, which may lead to abnormal situations such as difficult wire bonding and A detachment. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides a simple, general and effective chip processing method. Through the steps of vacuum high-temperature baking and plasma cleaning, the hydroxyl free radicals or other contaminants remaining on the chip surface during chip manufacturing are effectively removed, thereby avoiding the occurrence of chemical reactions of glue gas adsorption during the die bonding baking step and preventing chip contamination, difficult wire bonding and A detachment phenomena. This solution has a simple process, does not use chemical solutions during the process, will not cause secondary pollution or chip corrosion damage to the chips, and has high feasibility and versatility.

[0007] The technical solution of the present invention is as follows:

[0008] A processing method for improving the adsorption pollution of light-emitting diodes, comprising the following steps:

[0009] (1) Place the wafers that have completed the manufacturing of the light-emitting layer, electrodes, thinning and cleaning into a vacuum high-temperature baking equipment for high-temperature baking;

[0010] (2) After the high-temperature baking is completed, take out the wafers and place them into a plasma cleaning equipment for plasma cleaning;

[0011] (3) After the cleaning is completed, take out the wafers and perform subsequent wafer cutting and splitting steps to obtain single separated light-emitting diode chips.

[0012] Preferably according to the present invention, in step (1), the vacuum degree in the vacuum high-temperature baking equipment is ≤ 3*E-6 Torr, the baking temperature is 150 - 250 °C, and the baking time is 100 - 150 min.

[0013] Preferably according to the present invention, in step (2), the plasma cleaning chamber vacuum is < 20 mTorr, the cleaning power is 200 - 400 W, and the O 2 gas flow rate is 0.07 - 0.13 slm, and the cleaning time is 500 - 800 s.

[0014] The beneficial effects of the present invention are as follows:

[0015] 1. The present invention first removes the volatile contaminants generated during the manufacturing of light-emitting diode wafers through the high-temperature baking process, and then further removes the hydroxyl free radicals or charged ions on the wafer surface through the plasma cleaning process, thereby avoiding the occurrence of glue gas adsorption phenomena due to the action of charged particles such as hydroxyl free radicals on the chip surface during the subsequent die bonding process.

[0016] 2. The process of the present invention is simple, without using additional chemical solvents, avoiding secondary pollution and corrosion damage to the chips, etc. It is an effective, simple and highly applicable chip surface treatment method. Description of the Drawings

[0017] Figure 1 It is the surface morphology of the light-emitting diode chip obtained in the experimental example after baking in the experimental example;

[0018] Figure 2 It is the surface morphology of the light-emitting diode chip obtained in the comparative example after baking in the experimental example. Detailed Embodiments

[0019] The present invention will be further described below by way of examples in conjunction with the drawings, but not limited thereto.

[0020] Example 1:

[0021] A treatment method for improving the adsorption pollution of light-emitting diodes, comprising the following steps:

[0022] 1) Place the wafer that has completed the production of the light-emitting layer, electrodes, thinning and cleaning into a vacuum high-temperature baking equipment with a vacuum degree ≤ 3*E-6 Torr, and bake at 200 °C for 120 min.

[0023] 2) After the high-temperature baking is completed, take out the wafer and put it into the plasma cleaning equipment. Evacuate to < 20 mTorr, set the O 2 gas flow rate to 0.1 slm, the cleaning power to 300 W, and perform plasma cleaning for 600 s.

[0024] 3) After the cleaning is completed, take out the wafer and perform the subsequent wafer cutting and splitting steps to obtain single separated light-emitting diode chips.

[0025] Example 2:

[0026] A treatment method for improving the adsorption pollution of light-emitting diodes, comprising the following steps:

[0027] 1) Place the wafer that has completed the production of the light-emitting layer, electrodes, thinning and cleaning into a vacuum high-temperature baking equipment with a vacuum degree ≤ 3*E-6 Torr, and bake at 150 °C for 150 min.

[0028] 2) After the high-temperature baking is completed, take out the wafer and put it into the plasma cleaning equipment. Evacuate to < 20 mTorr, set the O 2 gas flow rate to 0.07 slm, the cleaning power to 200 W, and perform plasma cleaning for 800 s.

[0029] 3) After the cleaning is completed, take out the wafer and perform the subsequent wafer cutting and splitting steps to obtain single separated light-emitting diode chips.

[0030] Example 3:

[0031] A treatment method for improving the adsorption pollution of light-emitting diodes, comprising the following steps:

[0032] 1) Put the wafer that has completed the production of the light-emitting layer, electrodes, thinning, and cleaning into a vacuum high-temperature baking equipment with a vacuum degree ≤ 3*E-6 Torr, and bake at 250 °C for 100 min.

[0033] 2) After the high-temperature baking is completed, take out the wafer and put it into a plasma cleaning equipment. Evacuate to < 20 mTorr, set the O 2 gas flow rate to 0.13 slm, the cleaning power to 400 W, and perform plasma cleaning for 500 s.

[0034] 3) After the cleaning is completed, take out the wafer and perform subsequent wafer cutting and splitting steps to obtain single-separated light-emitting diode chips.

[0035] Comparative Example 1

[0036] A treatment method for improving the adsorption pollution problem of light-emitting diodes, comprising the following steps: directly perform the wafer cutting and splitting steps on the wafer that has completed the production of the light-emitting layer, electrodes, and thinning to obtain single-separated light-emitting diode chips.

[0037] Test Example 1

[0038] Randomly select 50 light-emitting diode chips obtained by the methods described in Example 1 and Comparative Example 1 respectively. Use die bonding glue to fix the chips on the bracket, place the bracket in a beaker, apply 2 - 3 g of die bonding glue around the bracket, then seal the beaker and place it in an oven at 165 °C for 90 min. After taking it out, observe the surface appearance of the chips, and conduct wire bonding and thrust verification comparisons. The results are as follows:

[0039] Observed and compared under a microscope, the surface of the electrodes of the chips obtained in Example 1 is clean and pollution-free (attached Figure 1 ), and the surface of the electrodes of the chips obtained in Comparative Example 1 is yellowed and there is an obvious pollution phenomenon (attached Figure 2 ). After wire bonding, the wire bonding situation is counted as shown in Table 1 below:

[0040] Table 1: Verification comparison of die bonding and wire bonding of chips obtained by the methods described in Example 1 and Comparative Example 1

[0041]

[0042] In contrast, for the chip obtained in Example 1, in an environment with extremely high concentrations of volatile small molecule crosslinking agents, no phenomenon of glue gas adsorption contaminating the electrodes occurred after baking and curing, and the solderability of the electrodes was good. However, for the chip obtained in Comparative Example 1, obvious electrode adsorption contamination phenomena were visible, and the solderability of the chip was significantly deteriorated. This shows that the inventive method significantly improves the problem of adsorption contamination of light-emitting diodes.

Claims

1. A method for improving adsorption contamination of light-emitting diode electrodes, characterized in that: The following steps are involved: (1) placing the wafer on which the light-emitting layer and electrode have been fabricated, thinned, and cleaned into a vacuum high-temperature baking device for high-temperature baking; (2) After the high temperature baking is completed, the wafer is taken out and placed in a plasma cleaning device for plasma cleaning; (3) After cleaning, the wafer is taken out and subsequent wafer cutting and splitting steps are performed to obtain a single separated light emitting diode chip.

2. The method for improving adsorption contamination of light-emitting diodes according to claim 1, characterized in that: In step (1), the vacuum degree in the vacuum high temperature baking equipment is ≤3*E-6Torr, the baking temperature is 150-250°C, and the baking time is 100-150min.

3. The method for improving adsorption contamination of light emitting diodes according to claim 1, characterized in that: In step (2), the vacuum of the plasma cleaning chamber is less than 20 mTorr, the cleaning power is 200-400 W, the O2 gas flow rate is 0.07-0.13 slm, and the cleaning time is 500-800 s.

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