Wafer pad layer aluminum film and the coating process thereof

Abstract

The present invention provides a wafer pad layer aluminum film and a coating processing process thereof, wherein the first Al-containing layer and a third Al-containing layer are included, wherein the material of the first Al-containing layer is selected from aluminum and / or copper, the first Al-containing layer is connected to a base layer of the wafer pad layer material, the material of the third Al-containing layer is selected from aluminum, the hardness of the first Al-containing layer is 100 g / cm² or more, the hardness of the third Al-containing layer is 50 g / cm² or less, and the thickness ratio of the first Al-containing layer to the third Al-containing layer is 1:1. The hardness of the first Al-containing layer is 100 g / cm² or more, the hardness of the second Al-containing layer is 60-80 g / cm², and the hardness of the third Al-containing layer is 50 g / cm² or less. During manufacturing, the coating speed of the first Al-containing layer is 0.45-0.5 nm / s, the coating speed of the second Al-containing layer is 0.3-0.45 nm / s, and the coating speed of the third Al-containing layer is 0.25-0.35 nm / s. The present invention solves the problem of ball mounting and IMC defects after flip-chip in packaging, and improves the core performance of the Al layer after film formation.

Description

Technology Field

[0001] The present invention belongs to the field of wafer coating processing technology, and specifically relates to a coating process for coating Al materials. The optimized process facilitates processes such as ball mounting and flip-chip in post-process packaging, improves IMC (intermetallic compound) performance, and promotes the advancement of wafer semiconductor coating packaging. Background Technology

[0002] Currently, the Al material used for the M2 (PAD) layer in wafer coating is typically coated to a thickness of approximately 2000nm to 2500nm. Film formation structures are generally classified into three types: ① Ti+Al, ② Ti+AlCu+Ti+Al, and ③ Ti+AlCu+Ti+Au. The first two types exhibit unstable performance, while the Ti+AlCu+Ti+Au type has very high costs. During actual application, it was discovered that after film formation is complete, critical performance indicators such as the intrinsic stress, roughness, and reflectivity of the Al material all undergo uncontrollable changes. The impact of Al layers on packaging quality varies depending on the structure. Therefore, it is necessary to modify the wafer coating process to implement process improvements and manage the coating indicators that affect the critical performance of the Al layer. Through this, these critical challenges in wafer semiconductors are resolved. The problem to be solved

[0003] To overcome the shortcomings of the prior art, the present invention provides a wafer pad layer (PAD) aluminum film and a coating processing process thereof. means of solving the problem

[0004] To realize the above objective, the present invention provides an Al layer structure coated on a wafer pad layer material layer, wherein the Al layer structure comprises a first Al-containing layer and a third Al-containing layer, wherein the material of the first Al-containing layer comprises a copper-aluminum alloy, wherein the first Al-containing layer is connected to a base layer of the wafer pad layer material, wherein the material of the third Al-containing layer is selected from aluminum, and wherein the hardness of the first Al-containing layer is 100 g / cm² 2 - That is all, and the hardness of the third Al-containing layer is 50 g / cm² 2 - The thickness ratio of the first Al-containing layer and the third Al-containing layer is 1:1.

[0005] Preferably, in the copper-aluminum alloy, the copper content is 3%-5%.

[0006] Preferably, a second Al-containing layer is further installed between the first Al-containing layer and the third Al-containing layer, the material of the second Al-containing layer is selected from aluminum, and the hardness of the second Al-containing layer is 60-80 g / cm² 2 am.

[0007] Preferably, the thicknesses of the first Al-containing layer, the second Al-containing layer, and the third Al-containing layer are 2:1:2.

[0008] Preferably, the thickness of the Al layer structure is 1800 nm to 2500 nm.

[0009] Preferably, the base layer of the wafer pad layer material comprises a substrate layer and a metal layer, and the metal layer comprises a titanium layer.

[0010] The present invention further provides a method for manufacturing an Al layer structure coated on the wafer pad layer material layer, wherein the coating speed of the first Al-containing layer is 0.45-0.5 nm / s and the coating speed of the third Al-containing layer is 0.25-0.35 nm / s.

[0011] Preferably, when the first Al-containing layer is coated using a copper-aluminum alloy, the coating speed of aluminum is 0.5 nm / s and the coating speed of copper is 0.1-0.16 nm / s.

[0012] Preferably, the coating speed of the second Al-containing layer is 0.30-0.45 nm / s. Effects of the invention

[0013] The beneficial effects of the present invention are as follows:

[0014] The present invention solves the problem of ball mounting and IMC defects after flip-chip in packaging, and improves the core performance of the Al layer after film formation. Brief explanation of the drawing

[0015] Figure 1 is a diagram showing the inspection effect of aluminum residue > 20% in the present invention. Figure 2 is a diagram showing the aluminum overflow inspection effect in the present invention. Figure 3 is a diagram showing the effect of passing the IMC test in the present invention. Figure 4 is a diagram showing the effect of failing the IMC inspection in the present invention. Figure 5 is a product flowchart of the pad layer coating process mentioned in the present invention. Figure 6 is a diagram of the shape result inspection of Group 1 in the present invention. Figure 7 is an IMC interface inspection drawing of Group 1 in the present invention. Figure 8 is a drawing of the gold ball measurement of Group 1 in the present invention. Figure 9 is a diagram showing the shape result inspection of Group 2 in the present invention. Figure 10 is an IMC interface inspection drawing of Group 2 in the present invention. Figure 11 is a drawing of the gold ball measurement of Group 2 in the present invention. FIG. 12 is a diagram of the shape result inspection of Group 3 in the present invention. FIG. 13 is an IMC interface inspection drawing of Group 3 in the present invention. FIG. 14 is a drawing of the gold ball measurement of Group 3 in the present invention. FIG. 15 is a diagram of the shape result inspection of Group 4 in the present invention. Figure 16 is an IMC interface inspection drawing of Group 4 in the present invention. Figure 17 is a drawing of the gold ball measurement of Group 4 in the present invention. Note: The X-axis of the IMC interface drawing is the horizontal coordinate and the y-axis is the vertical coordinate. The method for obtaining the X-axis value is to select the leftmost point of the residual gold trace as the reference point, move the camera to the rightmost point of the residual gold trace to obtain the X-value, which is the width of the residual gold, and obtain the width of the gold ball in this way. Specific details for implementing the invention

[0016] To better explain the purpose, technical solution, and advantages of the present invention, the present application will be described in more detail below in combination with specific embodiments.

[0017] Example 1

[0018] In the case of the Ti+Al layer of the pad layer, the general coating process has a coating speed of basically 0.35 nm / s for the Al layer (2000 nm), and after film formation, different degrees of change occur in the surface properties of the Al material between various charges.

[0019] The present embodiment provides a wafer pad layer aluminum film and a coating process thereof. Based on a partial product flowchart of FIG. 5, in the pad layer process, the speed at which the Al layer is coated is divided to separate the 2000 nm Al layer into different layers, and the speed of the first Al-containing layer (800 nm) is changed to 0.5 nm / s. The speed control method is crystal oscillator control of the coating machine, and the hardness of the aluminum is ≥100 g / cm² 2 It is made to be. The second Al-containing layer (800 nm) is coated at a speed of 0.35 nm / s so that the hardness of the aluminum is 60 g / cm² 2 -80g / cm 2The third Al-containing layer (400 nm) is coated at a speed of 0.25 nm / s so that the hardness of the aluminum is ≤50 g / cm² 2 Makes it so.

[0020] The parameters in Table 1 below represent partial data results from the coating verification, and the conditions are described as follows: ① Conditions 1, 2, 3, and 4 are the four verification DOEs. The DOEs primarily control the coating speed of the second and third layers and change the hardness of the Al layers in the second and third layers. Since the hardness of the aluminum film increases with faster forming speeds and decreases with slower speeds, a speed gradient splitting method was selected for coating. The process starts at 0.5 nm / s (0.5 nm / s is the theoretical maximum value of the equipment), and the gradient selection method reduces the speed to 0.02 nm / s to find relatively good state values, ensuring there are no issues with the IMC. ② The purpose of annealing is to release stress on the wafer to improve the wafer CP test electrical curve, and the annealing condition is to anneale at 280°C for 5 hours. ③ Shape inspection: The OM machine (high-magnification microscope) can magnify the shape of the product surface, and the inspection condition is to magnify by 5,000 times. ④ For IMC measurement, after ball mounting and extrusion, the coating surface of the PAD surface is viewed at a high magnification of 200x, and after flip-chip stacking, the aluminum coating surface of the gold ball on the substrate surface is observed at a high magnification.

[0021] Table 1

[0022]

[0023] Packaging process: Gold wire is heated to a high temperature (65°C or higher) using a ball mounter and installed on the aluminum pad of the chip. After ball mounting, the product is pressed onto the upper surface of the substrate using pressure, then heated using ultrasound (temperature controlled to 70-250°C), and welded to the substrate. The performance of the product is tested through the above ball mounting and pressing. The results are as shown in Table 2.

[0024] Table 2

[0025]

[0026] 4. Explanation of Results

[0027] Figure 1 is a microscopic inspection drawing at a high magnification of 200,000x after cutting following flip-chip processing. The flip-chip process used involves pressing the product onto the upper surface of a substrate by pressure after ball mounting, then heating it with ultrasound (controlling the temperature to 70-250℃), and finally welding it to the substrate. In Figure 1, if the aluminum residue is >20%, it is OK and the inspection is passed, and in Figure 2, if an aluminum overflow (NG) is observed, the inspection is not passed.

[0028] 200x inspection process: The optimal state of the IMC is when the gold ball is inoculated onto the surface of the aluminum pad. Through testing, the gold ball is pushed by mechanical thrust (30-60g), and the IMC size is determined by the width of the remaining gold ÷ width of the gold ball * 100. The result is >80%, which is a pass. In Figures 3 and 4, the IMC results are passed and failed inspection, respectively.

[0029] In FIGS. 1 to 4, OK and NG mean “inspection passed” and “inspection failed,” respectively.

[0030] The hardness of the outermost layer of the coated Al layer is >50 g / cm² 2 In this case, such hardness is too high for ball mounting in the packaging, which can lead to an IMC deficiency as shown in Fig. 4. The hardness of the innermost layer of the coated Al layer is <40 g / cm² 2 In this case, the hardness is too low for the flip chip of the packaging, which can cause an aluminum overflow problem as shown in Fig. 2, and the entire aluminum layer is extruded, resulting in poor performance.

[0031] The process of the present invention utilizes a fractional layer similar to Condition 4 and, by coating at divided speeds, ensures that the lower hard aluminum layer does not extrude aluminum and prevent aluminum overflow, ensures that the upper soft aluminum layer has very good IMC, and completely resolves issues regarding ball mounting and IMC after packaging (currently, aluminum residue >20% is considered a good condition in the industry). When the Al layer is coated at divided speeds according to the above fractional layer and subsequent packaging is performed, ball mounting can be prevented from causing aluminum overflow, there are no issues with the eutectic properties of the IMC, all issues such as reliability (defilming, high temperature) can be resolved, and electrical performance (CP) and frequency are not affected (values ​​vary by product).

[0032] Example 2

[0033] The present embodiment provides a wafer pad layer aluminum film and a coating process thereof. Based on a partial product flowchart of FIG. 5, in the pad layer process, the coating is divided into two layers while the total thickness of the coated Al layer remains unchanged. Different ratios of Cu are added to the first layer A1 (1000 nm). The hardness of the AlCu alloy must be harder than that of A1. As the Cu content continues to increase, the hardness of the AlCu alloy also increases. During coating, the aluminum coating speed is 0.5 nm / s, the copper ratio range is 3%-5%, the speed is 0.1-0.16 nm / s, and the hardness of AlCu is ≥80 g / cm³. 2 It is controlled by. The second Al-containing layer is coated at a speed of 0.25 nm / s, so that the hardness of aluminum is ≤50 g / cm² 2 It is made possible. The film formation method also achieves a coating effect in which the outer layer is soft aluminum and the inner layer is hard aluminum. Refer to Table 3 for inspection. In this embodiment, Groups 1, 2, and 3 are products formed after coating, and all can achieve the inspection pass result of FIG. 3.

[0034] Table 3

[0035]

[0036] Finally, it should be noted that the above embodiments are intended only to explain the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, a person skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of the present invention without departing from the substantial scope of the technical solution of the present invention.

Claims

Claim 1 In an Al layer structure coated on a wafer pad layer material layer, the structure comprises a first Al-containing layer and a third Al-containing layer, wherein the material of the first Al-containing layer comprises a copper-aluminum alloy, the first Al-containing layer is connected to a base layer of the wafer pad layer material, the material of the third Al-containing layer is selected from aluminum, and the hardness of the first Al-containing layer is 100 g / cm² 2 - That is all, and the hardness of the third Al-containing layer is 50 g / cm² 2 - An Al layer structure coated on a wafer pad layer material layer, wherein the thickness ratio of the first Al-containing layer and the third Al-containing layer is 1:

1. Claim 2 In claim 1, an Al layer structure coated on a wafer pad layer material layer, wherein the copper content in the copper-aluminum alloy is 3%-5%. Claim 3 In claim 1, a second Al-containing layer is further installed between the first Al-containing layer and the third Al-containing layer, the material of the second Al-containing layer is selected from aluminum, and the hardness of the second Al-containing layer is 60-80 g / cm² 2 Al layer structure coated on the wafer pad layer material layer. Claim 4 In paragraph 3, an Al layer structure coated on a wafer pad layer material layer, wherein the thickness ratio of the first Al-containing layer, the second Al-containing layer, and the third Al-containing layer is 2:1:

2. Claim 5 An Al layer structure coated on a wafer pad layer material layer, wherein the thickness of the Al layer structure is 1800 nm to 2500 nm in claim 1. Claim 6 In claim 1, the base layer of the wafer pad layer material comprises a substrate layer and a metal layer, and the metal layer comprises a titanium layer, wherein an Al layer structure is coated on the wafer pad layer material layer. Claim 7 A method for manufacturing an Al layer structure coated on a wafer pad layer material layer according to any one of claims 1 to 6, wherein the coating speed of the first Al-containing layer is 0.45-0.5 nm / s and the coating speed of the third Al-containing layer is 0.25-0.35 nm / s. Claim 8 A method for manufacturing an Al layer structure coated on a wafer pad layer material layer, wherein, in claim 7, the coating rate of the second Al-containing layer is 0.30-0.45 nm / s. Claim 9 A method for manufacturing an Al layer structure coated on a wafer pad layer material layer, wherein, in claim 7, when the first Al-containing layer is coated using a copper-aluminum alloy, the coating speed of aluminum is 0.5 nm / s and the coating speed of copper is 0.1-0.16 nm / s.

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