A method of metal lift optimization

Abstract

The application discloses a metal stripping optimization method, and belongs to the field of semiconductor electronic technology. The metal stripping optimization method provided by the application can reduce the undercut angle to 70-80 degrees and / or increase the thickness of a mask layer in metal stripping treatment, so that the metal is easy to strip, the metal stripping effect is better, and the cost is lower.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor electronics, in particular to a method for optimizing metal lift-off. BACKGROUND

[0002] With the popularization and application of high-power high-efficiency LED, the size of the minimum feature size (i.e. the minimum line width) of the chip is related to the performance of the chip, wherein the minimum feature size refers to the thinnest current conduction metal link size on the chip. In the metal lift-off process of the LED chip, the electrode layer usually uses negative photoresist as a mask layer. The smaller the minimum feature size of the chip, the smaller the photoresist slot, resulting in a smaller evaporation line width, i.e. area. Since the negative photoresist is in the shape of an inverted trapezoid, when the photoresist is lifted off using a blue film, it is more prone to cause problems such as bruising and deformation of the evaporated metal. For example, the Chinese invention patent with the publication number CN111137845A discloses a method for forming a patterned metal layer. Currently, in the electrode structure, photoresist is used as a mask layer, and after evaporating metal, a blue film or a white film is used for lift-off, so that the metal evaporated on the photoresist is lifted off together with the blue film or the white film, and the metal in the area without photoresist is directly evaporated on the chip surface. The lift-off of the mask layer has the following shortcomings: the higher the temperature of the evaporation machine, the more the photoresist deforms, resulting in a morphology that cannot meet the lift-off effect. The photoresist is equivalent to being baked at high temperature, and the stability is improved, but the lift-off effect is worse. Since the temperature cannot be kept constant during evaporation, the lift-off effect of the chip is low. SUMMARY

[0003] In order to overcome the above-mentioned defects of the prior art, the technical problem to be solved by the present application is to provide a method for optimizing metal lift-off, which is easy to peel off, has better tearing effect and is low in cost.

[0004] In order to solve the above-mentioned technical problems, the technical scheme adopted by the present application is as follows:

[0005] A method for optimizing metal lift-off, which reduces the undercut angle to 70-80° and / or increases the thickness of the mask layer to 1-2um in the metal lift-off process.

[0006] The present application has the advantages that a method for optimizing metal lift-off is provided, which is easy to peel off, saves blue film or white film materials, further saves cost, has better tearing effect, and optimizes the subsequent glue falling off of the residual gold caused by incomplete edge tearing. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 The figure shows the metal angle electron microscope graph of the product obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0008] To make the technical contents, purposes and effects of the present application clear, the following will be described in detail in combination with the embodiments and the accompanying drawings.

[0009] The most critical idea of the present application is to reduce the undercut angle and / or increase the thickness of the mask layer in the metal stripping process, so that the metal is easy to strip, the metal stripping effect is better, and the cost is lower.

[0010] Please refer to Figure 1 The method for optimizing metal stripping of the present application reduces the undercut angle to 70-80° and / or increases the thickness of the mask layer to

[0011] As can be seen from the above description, the present application has the advantages of easy metal stripping, saving blue film or white film materials, AOI yield improvement of 1%, and since the wafer cost is 240 yuan / wafer, 2497 wafers are produced per month, the cost saved is 2497*240*0.01=5993 yuan / month, i.e. the present application can save 5993 yuan of cost per month, greatly saving the production cost; the metal is easy to strip, the metal stripping effect is better, and the optimization of the edge metal stripping leads to residual metal collision and abnormality.

[0012] Further, reducing the undercut angle includes reducing the undercut angle by at least one of reducing the exposure dose, reducing the post-baking temperature, and reducing the post-baking time.

[0013] As can be seen from the above description, by reducing the exposure dose or reducing the post-baking temperature or reducing the post-baking time, or simultaneously reducing the exposure dose and the post-baking time or temperature, the undercut angle is reduced, wherein the post-baking temperature, time and exposure dose affect the undercut angle in the order of high to low.

[0014] Further, the exposure dose is 90-130 mj, the post-baking temperature is 112-116°C, and the time is 85-95s.

[0015] As can be seen from the above description, in batch production, the exposure dose, post-baking temperature and time are adjusted at the same time, so that the production conditions in the production process are more stable.

[0016] Further, increasing the thickness of the mask layer includes increasing the thickness of the mask layer by reducing the spin coating speed, so that the thickness of the mask layer is higher than the thickness of the electrode The above.

[0017] As can be seen from the above description, the electrode thickness is the thickness of the metal material above the mask layer, by increasing the thickness of the mask layer, when the electrode thickness and the mask layer thickness form a step, the metal is easy to strip, and the metal stripping effect is better.

[0018] Further, a metal stripping optimization method comprises the following steps:

[0019] S1: providing a substrate, and forming a photoresist layer on the substrate, and reducing the rotation speed of a spin coater;

[0020] S2: patterning the photoresist layer, wherein the exposure dose is 90-130 mj, the temperature of post-baking is 112-116 ℃, and the time is 85-95 s;

[0021] S3: depositing a metal material;

[0022] S4: removing the photoresist layer and the metal material above the photoresist layer to form a patterned metal layer.

[0023] From the above description, by reducing the rotation speed of the spin coater in S1, the thickness of the mask layer is increased, and by reducing the exposure dose, the temperature and time of post-baking in S2, the undercut angle is reduced, the metal stripping is easy to peel off, and the metal stripping effect is better.

[0024] Further, in S4, a blue film metal stripping machine is used to remove the photoresist layer and the metal material above the photoresist layer, and a photoresist removing liquid is used to remove the residual photoresist layer.

[0025] From the above description, the blue film metal stripping machine is used, the metal stripping efficiency is high, the material is saved, the cost is saved, the photoresist removing liquid is used to remove the residual photoresist layer, and the treated photoresist layer has no photoresist residue.

[0026] Further, the photoresist removing liquid is N-methyl pyrrolidone.

[0027] From the above description, the use of N-methyl pyrrolidone photoresist removing liquid not only greatly improves the photoresist removing speed and ability, but also reduces the corrosion of various substrates such as metal, passivation layer and silicon oxide.

[0028] Please refer to Figure 1 , the embodiment one of the present application is:

[0029] A metal stripping optimization method comprises the following steps:

[0030] S1: providing a substrate, and forming a photoresist layer on the substrate, and reducing the rotation speed of a spin coater to 1375 rpm;

[0031] S2: patterning the photoresist layer, wherein the exposure dose is 90 mj, the temperature of post-baking is 112 ℃, and the time is 85 s;

[0032] S3: depositing a metal material;

[0033] S4: using a blue film tear gold machine to remove the photoresist layer and the metal material above the photoresist layer, using N-methyl pyrrolidone to remove the residual photoresist layer, forming a patterned metal layer.

[0034] The thickness of the mask layer and the angle of the undercut angle of the product obtained above are measured, and the thickness of the mask layer is The angle of the undercut angle is 70°.

[0035] Embodiment two of the application:

[0036] A method for optimizing metal stripping, comprising the following steps:

[0037] S1: providing a substrate, and forming a photoresist layer on the substrate, reducing the rotation speed of the spin coater to 1375 rpm;

[0038] S2: patterning the photoresist layer, wherein the exposure dose is 90 mj, the temperature of the post-baking is 112℃, and the time is 85s;

[0039] S3: depositing a metal material;

[0040] S4: using a blue film tear gold machine to remove the photoresist layer and the metal material above the photoresist layer, using N-methyl pyrrolidone to remove the residual photoresist layer, forming a patterned metal layer.

[0041] The thickness of the mask layer and the angle of the undercut angle of the product obtained above are measured, and the thickness of the mask layer is The angle of the undercut angle is 80°.

[0042] Embodiment three of the application:

[0043] A method for optimizing metal stripping, comprising the following steps:

[0044] S1: providing a substrate, and forming a photoresist layer on the substrate, reducing the rotation speed of the spin coater to 1375 rpm;

[0045] S2: patterning the photoresist layer, wherein the exposure dose is 100 mj, the temperature of the post-baking is 114℃, and the time is 90s;

[0046] S3: depositing a metal material;

[0047] S4: using a blue film tear gold machine to remove the photoresist layer and the metal material above the photoresist layer, using N-methyl pyrrolidone to remove the residual photoresist layer, forming a patterned metal layer.

[0048] The thickness of the mask layer and the angle of the undercut angle of the product obtained above are measured, and the thickness of the mask layer is The angle of the undercut angle is 75°.

[0049] The comparative example one of the present application is:

[0050] A method for optimizing metal stripping, comprising the following steps:

[0051] S1: providing a substrate, and forming a photoresist layer on the substrate, and reducing the rotation speed of a spin coater to 3300 rpm;

[0052] S2: patterning the photoresist layer, wherein the exposure dose is 90 mj, the temperature of post-baking is 112℃, and the time is 85 s;

[0053] S3: depositing a metal material;

[0054] S4: removing the photoresist layer and the metal material above the photoresist layer by using a blue film gold tearing machine, removing the residual photoresist layer by using N-methyl pyrrolidone, and forming a patterned metal layer.

[0055] The thickness of the mask layer and the angle of the undercut angle of the product obtained above are measured, and the thickness of the mask layer is measured to be The angle of the undercut angle is 80°.

[0056] The comparative example two of the present application is:

[0057] A method for optimizing metal stripping, comprising the following steps:

[0058] S1: providing a substrate, and forming a photoresist layer on the substrate, and reducing the rotation speed of a spin coater to 1375 rpm;

[0059] S2: patterning the photoresist layer, wherein the exposure dose is 150 mj, the temperature of post-baking is 120℃, and the time is 100 s;

[0060] S3: depositing a metal material;

[0061] S4: removing the photoresist layer and the metal material above the photoresist layer by using a blue film gold tearing machine, removing the residual photoresist layer by using N-methyl pyrrolidone, and forming a patterned metal layer.

[0062] The thickness of the mask layer and the angle of the undercut angle of the product obtained above are measured, and the thickness of the mask layer is measured to be The angle of the undercut angle is 90°.

[0063] The AOL yield of the example one and the comparative examples one to two is tested, and the results show that the AOL yield of the example one and the comparative examples one to two is 99.2%, 98.1%, and 98.2%, respectively.

[0064] According to the above results, the AOI yield is improved by about 1%, and since the chip source cost is 240 yuan / chip, 2497 chips are produced per month, and the cost saved is 2497*240*0.01=5993 yuan / month. That is, the application can save 5993 yuan of cost per month, greatly saving the production cost.

[0065] In summary, the application provides a metal stripping optimization method, which is easy to peel off, saves blue film or white film materials, and saves cost; the gold tearing effect is better, and the subsequent glue removal machine falling residual gold caused by incomplete edge gold tearing is optimized to avoid abnormal impact.

[0066] The above is only an embodiment of the application, and does not limit the patent scope of the application, and any equivalent transformation, direct or indirect application in related technical fields using the content of the application specification and drawings are also included in the patent protection scope of the application.

Claims

1. A method of metal lift optimization, characterized by, The undercut angle is reduced to 70-80° and the thickness of the mask layer is increased to 38000-42000 angstroms.

2. A method of metal strip optimization according to claim 1, characterized in that, The undercut angle is reduced by at least one of reducing the exposure dose, reducing the post-exposure baking temperature, and reducing the post-exposure baking time.

3. A method of metal strip optimization according to claim 2, wherein, The exposure dose is 90-130 mj, the post-exposure baking temperature is 112-116 °C, and the time is 85-95 s.

4. A method of metal strip optimization as claimed in claim 1, wherein, The thickness of the mask layer is increased by reducing the spin speed of the spin coater, so that the thickness of the mask layer is more than 10000 angstroms higher than the thickness of the electrode.

5. A method of metal strip optimization as claimed in claim 1, wherein, The method comprises the following steps: S1: providing a substrate and forming a photoresist layer on the substrate, and reducing the spin speed of the spin coater; S2: patterning the photoresist layer, wherein the exposure dose is 90-130 mj, the post-exposure baking temperature is 112-116 °C, and the time is 85-95 s; S3: depositing a metal material; S4: removing the photoresist layer and the metal material above the photoresist layer to form a patterned metal layer.

6. A method of metal strip optimization according to claim 5, wherein, In S4, a blue film tearing machine is used to remove the photoresist layer and the metal material above the photoresist layer, and a photoresist remover is used to remove the residual photoresist layer.

7. A method of metal strip optimization according to claim 6, wherein, The photoresist remover is N-methyl pyrrolidone.

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