ITO film preparation method, LED chip and electronic equipment

Abstract

The invention provides an ITO film preparation method, an LED chip and electronic equipment, and the method comprises the steps: providing an epitaxial wafer, and depositing an initial ITO film; preparing an initial photoresist mask on the initial ITO film, and performing first etching to form a patterned transition ITO film; heating the initial photoresist mask to soften the initial photoresist mask so as to form a final photoresist mask; and performing second etching on the transition ITO film based on the final photoresist mask to form a final ITO film. The graphical transition ITO film is obtained through the first etching, the edge of the initial photoresist mask is softened and then collapses downwards to form the final photoresist mask, the transition ITO film is protected, the over-etching phenomenon is effectively avoided, meanwhile, residual ITO, metal and other impurities can be removed through the second etching, and abnormity of the appearance and the electrical yield of the chip is prevented.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an ITO film preparation method, an LED chip and an electronic device. Background Art

[0002] In LED chip manufacturing, ITO is widely used as a transparent conductive layer. After the ITO film is prepared, a photoresist is usually used as a mask to etch the ITO film into a film with a specific pattern to meet the needs of various chip products.

[0003] Wet chemical etching is typically used to etch the ITO film. After etching, a desmearing process is performed to obtain a specific ITO film shape. To prevent over-etching of the ITO film, which can lead to abnormal appearance and electrical yield, the etching time is usually short.

[0004] However, existing LED products, such as high-voltage and flip-chip products, have deep grooves, making it difficult for ITO etchants to completely etch the film within the grooves in a short etching time. Furthermore, ITO films are often deposited and etched together with other materials. For example, ITO films are often covered with an extremely thin aluminum film, and ITO etchants etch these metal films at a slow rate. In a short etching time, this can easily lead to metallic foreign matter residue, negatively impacting the performance of LED products. Longer etching times, while reducing the amount of residue to a certain extent, can easily lead to over-etching, which also negatively impacts the performance and yield of LED products. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an ITO film preparation method, LED chip and electronic equipment, aiming to solve the problem in the existing technology that it is easy to etch the ITO film and it is difficult to balance the problem of residual residue when etching the ITO film and avoiding over-etching.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A method for preparing an ITO film comprises the following steps:

[0008] Providing an epitaxial wafer, depositing an initial ITO film on the epitaxial wafer, and performing annealing on the initial ITO film;

[0009] Preparing an initial photoresist mask on the initial ITO film, and performing a first etching on the initial ITO film based on the initial photoresist mask to form a patterned transition ITO film, wherein the projection of the transition ITO film on the epitaxial wafer is located within the projection of the initial photoresist mask on the epitaxial wafer;

[0010] heating the initial photoresist mask in an inert gas environment to soften the initial photoresist mask to form a final photoresist mask, wherein the final photoresist mask covers the transition ITO film;

[0011] The transition ITO film is etched a second time based on the final photoresist mask to form a final ITO film.

[0012] Compared with the prior art, the beneficial effect of the present invention is that: a patterned transition ITO film is obtained by performing a first etching, and except for the transition ITO film, a small amount of unetched ITO is left in the grooves and other positions of the epitaxial wafer, and the initial photoresist mask is heated to soften it. Due to the lack of support from the edge of the transition ITO film, the edge of the initial photoresist mask collapses downward under gravity after softening to form the final photoresist mask with bent edges. The final photoresist mask matches the shape of the transition ITO film that needs to be prevented from over-etching, and the bent edge covers the edge of the transition ITO film, so that the transition ITO film is not exposed to the ITO etching solution during the second etching process, thereby protecting the transition ITO film and effectively avoiding over-etching. At the same time, the second etching can remove residual ITO, metal and other impurities, which is beneficial to improving product quality and preventing abnormalities in the appearance and electrical yield of the chip.

[0013] Furthermore, the transition ITO film includes an ITO film strip and an ITO sub-film, the outer edge of the ITO sub-film is connected to the film strip, and the average thickness of the ITO film strip is smaller than the average thickness of the ITO sub-film.

[0014] Furthermore, an ITO inclined surface is formed on a side of the ITO film strip facing the initial photoresist mask.

[0015] Furthermore, the heating temperature of the initial photoresist mask is higher than the glass transition temperature of the initial photoresist mask, and the heating temperature of the initial photoresist mask is lower than the decomposition temperature of the initial photoresist mask.

[0016] Furthermore, the heating time of the initial photoresist mask is 10 seconds to 300 seconds.

[0017] Furthermore, the final photoresist mask includes a bent portion and a flat portion, the side of the ITO sub-film facing away from the epitaxial wafer is connected to the flat portion, the outer edge of the flat portion is connected to the bent portion, and one end of the bent portion facing away from the flat portion is connected to the side of the epitaxial wafer facing the transition ITO film, and the bent portion covers the ITO film strip.

[0018] Furthermore, the step of etching the transition ITO film a second time based on the final photoresist mask to form a final ITO film further includes:

[0019] Based on the final photoresist mask, the transition ITO film is etched for a second time using the same etching solution, temperature and time as the first etching to form an ITO film to be cleaned;

[0020] The final photoresist mask is removed by an organic solvent, and the ITO film to be cleaned is treated by ultrasonic cleaning to obtain a final ITO film.

[0021] An embodiment of the present invention further provides an LED chip, comprising an ITO film, wherein the ITO film is prepared by the ITO film preparation method as described in the above technical solution.

[0022] An embodiment of the present invention further provides an electronic device, comprising the LED chip as described in the above technical solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 is a flowchart of a method for preparing an ITO film according to a first embodiment of the present invention;

[0024] Figure 2 Schematic diagram of the structure of the initial ITO film and the initial photoresist mask in the first embodiment of the present invention;

[0025] Figure 3 Schematic diagram of the structure of the transition ITO film in the first embodiment of the present invention;

[0026] Figure 4 Schematic diagram of the structure of the final photoresist mask and the final ITO film in the first embodiment of the present invention;

[0027] Figure 5 This is an appearance diagram of the transition ITO film and the initial photoresist mask in the first embodiment of the present invention;

[0028] Figure 6 This is an appearance diagram of the transition ITO film and the final photoresist mask in the first embodiment of the present invention;

[0029] Description of main component symbols:

[0030] epitaxial wafer 100 N-type epitaxial layer 110 light-emitting layer 120 P-type epitaxial layer 130 groove 200 Initial ITO film 300 Remaining part 301 ITO film strip 310 ITO sub-film 320 Final ITO film 330 Initial photoresist mask 400 Bending part 410 Leveling Department 420

[0031] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0032] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0033] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] See also Figure 1 The ITO film preparation method in the first embodiment of the present invention comprises the following steps:

[0036] Step S10: providing an epitaxial wafer, depositing an initial ITO film on the epitaxial wafer, and performing annealing treatment on the initial ITO film;

[0037] Preferably, see Figure 2 , providing a wafer including a plurality of epitaxial wafers 100, wherein the epitaxial wafer 100 includes an N-type epitaxial layer 110, a light-emitting layer 120 and a P-type epitaxial layer 130, and the epitaxial wafer 100 is a stepped structure, and there are deeper grooves 200 between adjacent epitaxial wafers 100. When the initial ITO film 300 is deposited, the ITO film will be deposited into the grooves 200, and the initial ITO film 300 covers the grooves 200 and the stepped structure. It can be understood that when the initial ITO film 300 is etched for a short time by conventional wet etching to avoid excessive etching, it is easy for ITO material to remain in the grooves 200 and the stepped structure. In the process of producing LED chips, the ITO film is often deposited and etched together with other materials, such as aluminum film. Short-term wet etching is also easy to cause other materials to remain on the surface of the epitaxial wafer 100.

[0038] Step S20: preparing an initial photoresist mask on the initial ITO film, and performing a first etching on the initial ITO film based on the initial photoresist mask to form a patterned transition ITO film, wherein the projection of the transition ITO film on the epitaxial wafer is located within the projection of the initial photoresist mask on the epitaxial wafer;

[0039] Preferably, the first etching is wet etching, using ITO etching solution, etching temperature of 45° C., and etching time of 210 seconds.

[0040] In step S20, the transition ITO film includes an ITO film strip and an ITO sub-film, the outer edge of the ITO sub-film is connected to the film strip, the average thickness of the ITO film strip is less than the average thickness of the ITO sub-film, and the ITO film strip forms an ITO bevel on the side facing the initial photoresist mask.

[0041] Preferably, see Figure 3 The ITO sub-film 320 is the central area of ​​the transition ITO film 300, and the ITO film strip 310 surrounds and connects the side edge of the ITO sub-film 320. For example, if the transition ITO film is a circular film, the ITO sub-film 320 is a circular film with a radius slightly smaller than that of the transition ITO film, and the ITO film strip 310 is an annular ring surrounding the ITO sub-film 320. The outer edge of the ITO film strip 310 is sunken under the action of the ITO etching solution to form an inclined surface, that is, after the initial ITO film 300 is etched, the P-type epitaxial layer 130 is back to the light-emitting layer 1 20, a sloped platform-shaped ITO material is left on one side. The cross-section of the ITO film strip 310 in this embodiment is trapezoidal. The initial photoresist mask 400 above the ITO slope is suspended. After the initial ITO film is etched for a short time, a residual portion 301 still exists. The residual portion 301 is located on the surface of the epitaxial wafer 100. The residual portion 301 includes ITO residual particles, metal particles and foreign matter. It can be understood that the residual portion 301 is prone to cause abnormal electrical performance of the LED chip, and is prone to problems such as leakage and direct connection short circuit between PN epitaxial layers, resulting in a decrease in the electrical yield of the LED chip.

[0042] Step S30: heating the initial photoresist mask in an inert gas environment to soften the initial photoresist mask to form a final photoresist mask, wherein the final photoresist mask covers the transition ITO film;

[0043] Preferably, the wafer is placed in an oven for heating to soften the initial photoresist mask 400. The inert gas is nitrogen with a flow rate of 500 sccm. Figure 4The softened photoresist covers the surface of the transition ITO film and cooperates with the P-type epitaxial layer 130 to completely cover the transition ITO film. It can be understood that the inert gas can effectively prevent the photoresist from being oxidized at high temperatures, thereby improving process reliability.

[0044] In the step S30, the heating temperature of the initial photoresist mask is higher than the glass transition temperature of the initial photoresist mask, the heating temperature of the initial photoresist mask is lower than the decomposition temperature of the initial photoresist mask, and the heating time of the initial photoresist mask is 10 seconds to 300 seconds.

[0045] Preferably, the heating temperature of the initial photoresist mask 400 selected in this embodiment is 160° C., and the heating time is 60 seconds.

[0046] In step S30, please refer to Figure 4 The final photoresist mask includes a bending portion 410 and a flat portion 420. The side of the ITO sub-film 320 facing away from the epitaxial wafer 100 is connected to the flat portion 420. The outer edge of the flat portion 420 is connected to the bending portion 410. The end of the bending portion 410 facing away from the flat portion 420 is connected to the side of the epitaxial wafer 100 facing the transition ITO film. The bending portion covers the ITO film strip.

[0047] Preferably, the suspended edge of the initial photoresist mask 400 collapses due to gravity and surface tension after being heated and softened, and the ITO film in a sloped shape is bent, that is, it is bent in accordance with the ITO slope until one end is connected to the P-type epitaxial layer 130. It can be understood that the ITO film strip 310 surrounds the outer edge of the ITO sub-film 320 and is a closed ring. The outer edge of the transition ITO film is the ITO slope. The suspended initial photoresist mask 400 located above the ITO slope is uniformly bent downward to cover the entire transition ITO film. It can be understood that if etching is performed again, the etching solution cannot contact the transition ITO film, and the final photoresist mask forms a protection for the transition ITO film.

[0048] Furthermore, the appearance of the LED chip was observed by using a metallographic microscope at a magnification of 500 times. After the first etching, the appearance of the transition ITO film and the initial photoresist mask can be seen in FIG. Figure 5 , it can be seen that there is a gap between the transition ITO film and the initial photoresist mask 400, which can be seen in FIG. Figure 5As can be understood, if further etching is performed to remove the residue, the ITO etching liquid will enter through the gap and etch the transition ITO film, causing the shape of the transition ITO film to change, the electrical properties to change, and over-etching to occur, which will cause the electrical yield of the LED chip to drop significantly. After the initial photoresist mask 400 is softened by heating, the edge of the initial photoresist mask 400 softens and collapses, bends in accordance with the shape of the transition ITO film, and covers the transition ITO film. For the appearance of the final photoresist mask and the transition ITO film, please refer to Figure 6 It can be seen that the gap between the transition ITO film and the final photoresist mask disappears, specifically the white gap disappears. After the heating and softening step, the transition ITO film required for the product is protected, and further etching will not cause excessive etching of the transition ITO film.

[0049] Step S40: etching the transition ITO film a second time based on the final photoresist mask to form a final ITO film.

[0050] See also Figure 4 It can be understood that through the second etching, the ITO particles, metal particles and foreign matter remaining on the surface of the epitaxial wafer can be completely removed without over-etching the transition ITO film, that is, the residual part 301 is removed, which effectively ensures that the electrical parameters of the LED chip are not abnormal and avoids quality problems such as leakage and short circuit.

[0051] The step S40 further includes:

[0052] S410: Based on the final photoresist mask, the transition ITO film is etched for the second time using the same etching solution, temperature and time as the first etching to form an ITO film to be cleaned;

[0053] Preferably, the same etching parameters as the first etching are used, that is, ITO etching solution is used, the etching temperature is 45° C., and the etching time is 210 seconds.

[0054] S420: removing the final photoresist mask by using an organic solvent, and treating the ITO film to be cleaned by ultrasonic cleaning to obtain a final ITO film.

[0055] It can be understood that the shape of the final ITO film is consistent with that of the transition ITO film, and is protected by the final photoresist mask during the second etching, and the shape does not change.

[0056] Preferably, wafers of the same product model are selected, and ITO films are prepared using the traditional etching method and the method in this embodiment respectively. Other process parameters are consistent, and the electrical parameter yields are tested separately by the MAP machine. Among them, the starting voltage yield of the LED chip in the wafer processed by the traditional etching method is 91.72%, and the operating voltage yield of the LED chip is 94.81%. The starting voltage yield of the LED chip in the wafer processed by the method in this embodiment is 94.67%, and the operating voltage yield of the LED chip is 97.14%. The ITO film preparation method in this embodiment effectively improves the electrical yield of the LED chip.

[0057] The LED chip in the second embodiment of the present invention includes an ITO film, and the ITO film is prepared by the ITO film preparation method described in the first embodiment.

[0058] The electronic device in the third embodiment of the present invention includes the LED chip as described in the second embodiment.

[0059] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0060] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing an ITO film, characterized in that: The steps include: Providing an epitaxial wafer, depositing an initial ITO film on the epitaxial wafer, and performing annealing on the initial ITO film; Preparing an initial photoresist mask on the initial ITO film, and performing a first etching on the initial ITO film based on the initial photoresist mask to form a patterned transition ITO film, wherein the projection of the transition ITO film on the epitaxial wafer is located within the projection of the initial photoresist mask on the epitaxial wafer; heating the initial photoresist mask in an inert gas environment to soften the initial photoresist mask to form a final photoresist mask, wherein the final photoresist mask covers the transition ITO film; The transition ITO film is etched a second time based on the final photoresist mask to form a final ITO film.

2. The ITO film preparation method according to claim 1, wherein The transition ITO film includes an ITO film strip and an ITO sub-film. The outer edge of the ITO sub-film is connected to the film strip, and the average thickness of the ITO film strip is smaller than the average thickness of the ITO sub-film.

3. The ITO film preparation method according to claim 2, wherein The side of the ITO film strip facing the initial photoresist mask forms an ITO inclined surface.

4. The method for preparing an ITO film according to claim 1, wherein The heating temperature of the initial photoresist mask is higher than the glass transition temperature of the initial photoresist mask, and the heating temperature of the initial photoresist mask is lower than the decomposition temperature of the initial photoresist mask.

5. The ITO film preparation method according to claim 1, wherein The heating time of the initial photoresist mask is 10 seconds to 300 seconds.

6. The method for preparing an ITO film according to claim 2, wherein: The final photoresist mask includes a bent portion and a flat portion. The side of the ITO sub-film facing away from the epitaxial wafer is connected to the flat portion, the outer edge of the flat portion is connected to the bent portion, and one end of the bent portion facing away from the flat portion is connected to the side of the epitaxial wafer facing the transition ITO film. The bent portion covers the ITO film strip.

7. The method for preparing an ITO film according to claim 1, wherein: The step of etching the transition ITO film for a second time based on the final photoresist mask to form a final ITO film further includes: Based on the final photoresist mask, the transition ITO film is etched for a second time using the same etching solution, temperature and time as the first etching to form an ITO film to be cleaned; The final photoresist mask is removed by an organic solvent, and the ITO film to be cleaned is treated by ultrasonic cleaning to obtain a final ITO film.

8. An LED chip comprising an ITO film, characterized in that: The ITO film is prepared by the ITO film preparation method according to any one of claims 1 to 7.

9. An electronic device, characterized in that: The LED chip according to claim 8 is included.

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