A method for improving the moisture heat resistance reliability of a bump connection structure

Abstract

The application discloses a method for improving the moisture and heat resistance reliability of a bump connection structure, which comprises the following steps: (1) performing hydroxylation treatment on the bump connection structure for semiconductor device connection; (2) performing treatment on the bump connection structure with an organic compound to form a self-assembled molecular film; (3) performing dehydration treatment on the bump connection structure; and (4) performing etching on the self-assembled molecular film by using a reactive ion etching technology. Finally, the self-assembled molecular film with regular orientation and close arrangement is formed on the surface of the bump connection structure, especially at the undercut structure. The preparation method is simple, the self-assembled molecular film formed has high stability and corrosion resistance, and the reliability and stability of the bump in a moisture and heat environment can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of semiconductor integrated circuits, and particularly relates to a method for improving the humidity-heat reliability of a bump connection structure. BACKGROUND

[0002] In the field of display panels, display driving chips, radio frequency chips and the like need to be connected to substrates or other components through bump structures after the integrated circuits are manufactured. In display panel packaging, the main packaging methods are Chip On Film (COF), Chip On Glass (COG) and Chip On PI (COP). The bump is a key part of mechanical and electrical connection between the chip and the substrate or other components, and therefore the bump needs to have high reliability.

[0003] The current mainstream bump manufacturing process mainly includes the following steps. The first step is to form an Under Bump Metallization (UBM) layer. The UBM layer includes a barrier layer and a seed layer above the barrier layer. The bump is then grown on the UBM layer in an electroplating manner. After the bump is manufactured, the unnecessary part of the UBM layer is removed by wet etching. Due to the isotropy of wet etching and the need for over-etching in the etching process, the UBM layer is inevitably over-etched laterally, forming an undercut structure.

[0004] During the humidity-heat reliability test of the bump chip, stress corrosion and electrochemical corrosion occur at the undercut due to the existence of the undercut structure, which causes the UBM layer to crack and seriously reduces the humidity-heat reliability of the bump. SUMMARY

[0005] The purpose of the present application is to provide a method for improving the humidity-heat reliability of a bump connection structure, which forms a self-assembled molecular film on the surface of the bump, especially at the undercut structure, thereby improving the humidity-heat reliability of the bump.

[0006] In order to achieve the above purpose, the technical solution of the present application is as follows:

[0007] A method for improving the humidity-heat reliability of a bump connection structure, the bump connection structure is arranged on a semiconductor substrate, the surface of the semiconductor substrate has a metal pad, and the bump connection structure includes a bottom metal layer and a metal bump arranged in sequence on the metal pad; the method includes the following steps:

[0008] 1) performing hydroxylation treatment on the surface of the bump connection structure;

[0009] 2) treating the surface of the bump-connection structure after the hydroxylation treatment with an organic compound to form a self-assembled molecular film, wherein the organic compound is at least one of an organic sulfide, an organic silane, a fatty acid, an organic phosphate, or a Schiff base;

[0010] 3) dehydrating the bump-connection structure;

[0011] 4) removing the self-assembled molecular film covering the surface and the side of the metal bump by a reactive ion etching technique.

[0012] Optionally, the hydroxylation treatment includes alkaline hydroxylation, strong acid hydroxylation, ultraviolet irradiation hydroxylation, and plasma hydroxylation.

[0013] Optionally, the surface of the bump-connection structure is first treated with ultraviolet light and ozone for a preliminary hydroxylation treatment. In order to ensure that the surface and the undercut structure are completely covered with hydroxyl groups, the bump-connection structure is then treated with plasma, thereby obtaining a hydroxylated bump sample.

[0014] Optionally, the organic compound treatment is immersing the bump-connection structure in a solution of the organic compound with a volume concentration of 0.001-100 mL / L for 1 min-12 h.

[0015] Optionally, the organic compound treatment is immersing the bump-connection structure in a solution of the organic compound with a volume concentration of 0.03-30 mL / L for 30 min-12 h.

[0016] Optionally, the organic compound is octadecanethiol, octadecyltrichlorosilane, 11-mercaptoundecanoic acid, or n-octadecylphosphoric acid.

[0017] Optionally, the dehydration treatment is performed at a temperature of 10-300 °C for 1 min-12 h.

[0018] Optionally, the surface of the semiconductor substrate is covered with a passivation layer, the passivation layer is provided with an opening for connecting the metal pad and the bump-connection structure, and the bottom metal layer is deposited in the opening and extends to the surface of the passivation layer around the opening.

[0019] Optionally, the sidewall of the bottom metal layer is recessed inward relative to the sidewall of the metal bump, and the self-assembled molecular film covers at least the sidewall of the bottom metal layer.

[0020] Optionally, the bottom metal layer comprises, from bottom to top, a barrier layer and a seed layer, the barrier layer is titanium metal or a titanium-tungsten alloy, and the seed layer is the same metal as the metal bump.

[0021] Self-Assembled Monolayers (SAMs) are a kind of self-assembled monolayer formed spontaneously on the interface by the chemical adsorption between the head group of the organic active molecule and the substrate.

[0022] The SAMs have the following characteristics:

[0023] (1) Spontaneously formed in situ, thermodynamically stable, easy to make;

[0024] (2) Regardless of the shape of the substrate material, a uniform, consistent, molecularly ordered, densely packed and low defect coverage layer can be formed;

[0025] (3) Without changing the inherent properties of the substrate material, by artificially changing the molecular structure or cutting the molecules, an interface with specific properties is obtained, thereby improving the corrosion resistance of the substrate material.

[0026] The self-assembled monolayer formed on the bump surface has high stability and corrosion resistance, and can effectively improve the reliability and stability of the bump in a humid and hot environment.

[0027] Compared with the prior art, the method for improving the humidity and heat resistance of the bump connection structure provided by the present application can form a self-assembled monolayer with regular orientation and dense arrangement on the undercut structure of the bump connection structure, which can achieve the following beneficial effects:

[0028] 1) Greatly improve the corrosion resistance of the bump connection structure to acid, alkali and some salt solutions, effectively avoiding the problem of cracking of the UBM layer during the humidity and heat resistance test of the bump.

[0029] 2) The self-assembled monolayer has high thermal stability. In a higher temperature range, the contact angle of the self-assembled monolayer decreases slightly and the surface energy increases slightly. However, the change is not large, and the temperature range meets the requirements of the temperature range required by the humidity and heat resistance test. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the description of the embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0031] Figure 1 is a top view schematic diagram of the wafer with a bump connection structure of embodiment 1;

[0032] Figure 2A schematic view of the bump connection structure after the method for improving the humidity-heat reliability of the bump connection structure of Example 1 was processed;

[0033] Figure 3 A partial enlarged schematic view of Figure 2

[0034] Figure 4 A hydrophobic effect diagram of the bump surface (left) of the untreated bump of Comparative Example 1 and the treated bump (right) surface of Example 1;

[0035] Figure 5 A hydrophobic effect diagram of the untreated TiW alloy substrate surface (left) and the TiW alloy substrate (right) surface processed by the process of Example 1;

[0036] Figure 6 A scanning electron microscope image of the bump connection structure of Comparative Example 1 after the humidity-heat reliability test;

[0037] Figure 7 A scanning electron microscope image of the bump connection structure of Example 1 after the humidity-heat reliability test;

[0038] Figure 8 A schematic view of the results of the shear test of the bump connection structure of Comparative Example 1 (untreated) and Example 1 (treated with an organic compound) after the humidity-heat reliability test. DETAILED DESCRIPTION

[0039] The present application will be further explained in connection with the accompanying drawings and specific embodiments.

[0040] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in connection with specific embodiments, but the present application is not limited to these embodiments. It should be noted that the following described embodiments or technical features can be combined to form new embodiments without conflict. In the present application, the devices and raw materials used can be purchased from the market or are commonly used in the art. The methods in the following examples are conventional methods in the art, unless otherwise specified.

[0041] Example 1

[0042] As Figure 1 and Figure 2 ​As shown, the bump connection structure 1 used in the present embodiment is formed on a semiconductor substrate 2. The semiconductor substrate 2 can be made of silicon, gallium arsenide, silicon carbide, etc., and can be a semiconductor substrate, a semiconductor epitaxial structure, a semiconductor device structure after device processing, etc. At least one metal pad (e.g., an aluminum pad 3) is provided on the semiconductor substrate 2, and a passivation layer 4 is further provided on the surface of the semiconductor substrate 2, the passivation layer 4 having an opening exposing part of the aluminum pad 3. The passivation layer 4 can be made of silicon nitride, silicon oxide, or silicon oxynitride. The bump connection structure 1 is provided on the opening and contacts the aluminum pad 3. The bump connection structure 1 includes, from bottom to top, a bottom metal layer 11 and a metal bump 12, and the bottom metal layer 11 includes, from bottom to top, a barrier layer 111 and a seed layer 112. The bottom metal layer 11 is deposited in the opening and extends to the surface of the passivation layer 4 around the opening. The sidewall of the bottom metal layer 11 is recessed inward relative to the sidewall of the metal bump 12. The barrier layer 111 can be made of titanium metal or titanium alloy, chromium metal or chromium alloy, or nickel metal or nickel alloy. The seed layer 112 and the metal bump 12 can be made of gold, silver, copper, tin, palladium, or an alloy thereof.

[0043] In the above structure, during fabrication, the aluminum pad 3 is first formed on the semiconductor substrate 2, then the passivation layer 4 is deposited, the passivation layer 4 is opened, and then the barrier layer 111 and the seed layer 112 are sequentially deposited, the metal bump 12 is fabricated by electroplating, and then the unwanted bottom metal layer 11 is removed by etching. Due to the limitation of the etching process, the sidewall of the bottom metal layer 11 is recessed inward to form an undercut structure.

[0044] For the bump connection structure having the above structure, the following steps are performed:

[0045] S1: The bump connection structure is sequentially ultrasonically cleaned in acetone solution, ethanol solution, and ultrapure water for 10 minutes, and then dried with nitrogen.

[0046] S2: The bump connection structure cleaned in S1 is first subjected to a preliminary hydroxylation treatment by ultraviolet rays and ozone in a UV cleaning machine. In order to ensure that the surface and the undercut structure are completely covered with hydroxyl groups, the bump connection structure is again subjected to treatment by a plasma surface treatment instrument, thereby obtaining a hydroxylated bump sample.

[0047] S3: The hydroxylated bump connection structure treated in S2 is immersed in an organic compound solution having a volume concentration of 0.001-100 mL / L by using the immersion method, and the immersion time is 1 minute-12 hours, thereby forming a self-assembled molecular film on the surface of the bump connection structure.

[0048] S4: The bump connection structure treated in S3 is sequentially ultrasonically cleaned in acetone solution, ethanol solution, and ultrapure water for 10 minutes, and then dried with nitrogen.

[0049] S5: Put the bump connection structure after S4 step into the oven with temperature of 10-300℃ for dehydration treatment, take out after baking for 1 min-12 h.

[0050] S6: Finally, use the reactive ion etching technology (RIE) to remove the self-assembled molecular film covering the surface and side of the metal bump 12, so as to expose the metal bump for subsequent external connection, interconnection and other processes. Finally, the self-assembled molecular film 5 wrapping the undercut structure of the bump is formed, as shown in Figure 2 and Figure 3 The self-assembled molecular film 5 covers the sidewall of the bottom metal layer 11 and the surface of the metal bump 12 and the passivation layer 4 connected thereto, thereby avoiding the corrosion and cracking of the structure (i.e. the undercut structure) at the place, causing the connection reliability failure.

[0051] The obtained bump sample number and preparation conditions with the self-assembled molecular film are shown in Table 1.

[0052] Table 1

[0053] Sample No. Solution concentration Treatment time Organic compound A1 0.03 ml / L 30 min Octadecanethiol A2 0.3 ml / L 3h Octadecyltrichlorosilane A3 3 ml / L 6h 11-Mercaptoundecanoic acid A4 30 ml / L 12h n-Octadecylphosphonic acid

[0054] Comparative Example 1

[0055] The difference between Example 1 and Comparative Example is that the bump sample of the comparative example only undergoes the treatment means in the step S1, and the rest is not treated, and the sample number is A5.

[0056] Performance test

[0057] 1. Hydrophobicity test

[0058] The rated capacity of pure water is sucked by a straw and dropped on the surface of the bump connection structure under different conditions. At the same time, in order to better observe the hydrophobic effect, the sample which is not treated by RIE technology is selected for characterization. Preferably, A2 sample and A5 sample are selected for comparison, and the results show that the size difference of the surface contact angle of the bump treated by the organic compound and the untreated bump is obvious, as shown in Figure 4 .

[0059] In order to better illustrate the corrosion resistance of the self-assembled molecular film, the self-assembled molecular film is prepared on the TiW alloy substrate, and the preparation method is the same as that of the A2 sample of Example 1. The hydrophobic test is carried out with the TiW alloy substrate treated in the same way as Comparative Example 1 as a comparative example, and the results are shown in Figure 5 , which shows that the size difference of the surface contact angle of the TiW alloy substrate treated by the organic compound and the untreated TiW alloy substrate is obvious.

[0060] 2. Humidity and heat reliability test

[0061] Damp heat reliability test is mainly used for air tightness evaluation and firmness test. The sample is placed in a high temperature, high humidity and high pressure environment, forcing water into the sample to expose defects such as delamination, cracking and metallization corrosion.

[0062] According to reliability standards JESD22-A101 and JESD22-A102, two kinds of damp heat reliability tests are developed, and the conditions are as follows:

[0063]

[0064] In this embodiment, the bump sample under THT test for 500 hours is taken as an example. First, a part of the bump sample is cut off by using focused ion beam (FIB) technology to expose the interface to be observed. Second, whether there is a crack between the bump and the TiW barrier layer is observed by using a scanning electron microscope (SEM). If there is a crack, it is considered to be failed; otherwise, it is passed.

[0065] Preferably, A2 sample and A5 sample are selected for comparison. The observation by scanning electron microscope shows that the untreated bump has cracks (see Figure 6 ), and the bump treated by organic compound does not have cracks (see Figure 7 ). In addition, it should be noted that Figure 7 the area marked as Pt element in is a protective layer formed by depositing Pt element during FIB processing to protect the sample surface, which is not formed during sample preparation and reliability test.

[0066] 3. Shear test

[0067] The purpose of shear test is to evaluate the shear resistance of the bump sample by destructive shear test. The shear tool is aligned with the bump at a certain height by using a push-pull testing machine, so that it can contact one side of the bump. At the same time, a constant speed should be maintained during the shear process until the shear force drops below 25% of the maximum value, or until the moving distance of the shear tool exceeds the diameter of the bump. If the bump or seed layer cracks and the TiW barrier layer leaks out, it is considered to be failed; if it does not leak out, it is considered to be passed.

[0068] Preferably, A2 sample (treated by organic compound) and A5 sample (untreated) after damp heat reliability are subjected to shear test. As shown in Figure 8 , it can be found that after shear, the TiW barrier layer of A5 sample leaks out seriously, while the TiW barrier layer of A5 sample hardly leaks out.

[0069] The above embodiments are only used to further illustrate the method for improving the moisture and heat resistance reliability of the bump connection structure of the present application, but the present application is not limited to the embodiments, and any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application all fall within the protection scope of the technical scheme of the present application.

Claims

1. A method for improving the resistance to damp heat reliability of a bump connection structure, characterized by, The bump connection structure is arranged on a semiconductor substrate, a surface of the semiconductor substrate is provided with a metal pad, and the bump connection structure comprises a bottom metal layer and a metal bump arranged on the metal pad in sequence. 1) performing hydroxylation treatment on a surface of the bump connection structure; 2) performing organic compound treatment on the surface of the bump connection structure after the hydroxylation treatment to form a self-assembled molecular film, wherein the organic compound is at least one of an organic sulfide, an organic silane, a fatty acid, an organic phosphate or a Schiff base; 3) performing dehydration treatment on the bump connection structure; 4) removing the self-assembled molecular film covering the upper surface and the side surface of the metal bump by using a reactive ion etching technology, and the remaining self-assembled molecular film covers the sidewall of the bottom metal layer and the surface of the metal bump connected with the sidewall.

2. The method of improving the reliability against damp-heat of a bump connection structure according to claim 1, characterized by: The hydroxylation treatment comprises lye hydroxylation, strong acid hydroxylation, ultraviolet irradiation hydroxylation and plasma hydroxylation.

3. The method of improving the reliability against damp-heat of a bump connection structure according to claim 2, characterized by: The surface of the bump connection structure is first subjected to preliminary hydroxylation treatment by using ultraviolet and ozone, and then the bump connection structure is subjected to treatment by using plasma to obtain the bump connection structure with a surface subjected to hydroxylation.

4. The method of improving the reliability against damp-heat of a bump connection structure according to claim 1, characterized by: The organic compound treatment is to immerse the bump connection structure in a solution of the organic compound with a volume concentration of 0.001-100 mL / L, and the soaking time is 1 min-12 h.

5. The method of improving the reliability against damp-heat of a bump connection structure according to claim 4, characterized by: The organic compound treatment is to immerse the bump connection structure in a solution of the organic compound with a volume concentration of 0.03-30 mL / L, and the soaking time is 30 min-12 h.

6. The method of improving the reliability against damp-heat of a bump connection structure according to claim 5, characterized by: The organic compound is octadecanethiol, octadecyltrichlorosilane, 11-mercaptoundecanoic acid or n-octadecyl phosphoric acid.

7. The method of improving the reliability against damp-heat of a bump connection structure according to claim 1, characterized by: The dehydration treatment is performed at a temperature of 10-300 ℃, and the dehydration treatment time is 1 min-12 h.

8. The method of improving the reliability against damp-heat of a bump connection structure according to claim 1, characterized by: The surface of the semiconductor substrate is covered with a passivation layer, the passivation layer is provided with an opening for connecting the metal pad and the bump connection structure, and the bottom metal layer is deposited in the opening and extends to the surface of the passivation layer around the opening.

9. The method of improving the reliability against damp-heat of a bump connection structure according to claim 8, characterized by: The sidewall of the bottom metal layer is recessed inward relative to the sidewall of the metal bump, and the self-assembled molecular film at least covers the sidewall of the bottom metal layer.

10. The method of improving the reliability against damp-heat of a bump connection structure according to claim 1, characterized by: The bottom metal layer comprises a barrier layer and a seed layer from bottom to top. The bottom metal layer comprises a barrier layer and a seed layer from bottom to top.

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