Aluminum film for wafer pad layer and method for coating the same

Abstract

The objective is to provide an aluminum film for a wafer pad layer and a method for coating it therewith. [Solution] The wafer is composed of a first AL-containing layer and a third AL-containing layer, the material of the first AL-containing layer is selected from aluminum and / or copper, the first AL-containing layer is connected to the 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 Therefore, the hardness of the third AL-containing layer is 50 g / cm². 2 In the following, the ratio of the thicknesses 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. 2 In summary, the hardness of the second AL-containing layer is 60-80 g / cm². 2 Within this range, the hardness of the third AL-containing layer is 50 g / cm². 2 The following conditions apply during manufacturing: During manufacturing, the coating speed of the first AL layer is 0.45 to 0.5 nm / second, the coating speed of the second AL layer is 0.3 to 0.45 nm / second, and the coating speed of the third AL layer is 0.25 to 0.35 nm / second. The present invention solves the problem of IMC defects after ball mounting and flip-chip mounting in the package and improves the main performance of the AL layer after film formation.

Description

[Technical Field]

[0001] This invention relates to the technical field of wafer coating, and more particularly to a coating process for aluminum (AL) materials. The optimized process facilitates post-processing such as ball mounting and flip-chip mounting in packages, improves the performance of IMCs (intermetallic compounds), and promotes the development of wafer semiconductor coatings and packaging. [Background technology]

[0002] Currently, the M2(PAD) layer material AL coating for wafer coatings is typically applied to a thickness of around 2000nm to 2500nm. The deposition structure is classified into three types: 1) TI+AL, 2) TI+ALCU+TI+AL, and 3) TI+ALCU+TI+AU. The first two have unstable performance, and the cost of TI+ALCU+TI+AU is too high. In actual applications, it has been found that important performance indicators of the AL material itself, such as stress, roughness, and reflectivity, undergo uncontrollable changes after deposition. Since different forms of AL layers have different effects on package quality, it was necessary to review the wafer coating process and implement process improvements and focused control that affect the important performance of the AL layer to solve important problems in semiconductor wafers. [Overview of the project] [Problems that the invention aims to solve]

[0003] To overcome the shortcomings of the prior art, the present invention aims to provide an aluminum film for a wafer pad layer and a method for coating it therewith. [Means for solving the problem]

[0004] To achieve the above objective, the present invention provides an AL layer structure coated on a wafer PAD layer material layer, wherein the AL layer structure consists of a first AL-containing layer and a third AL-containing layer, the material of the first AL-containing layer is selected from aluminum and / or copper, the first AL-containing layer is connected to the 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 Therefore, the hardness of the third AL-containing layer is 50 g / cm². 2 In the following, the ratio of the thickness of the first AL-containing layer to the third AL-containing layer is 1:1.

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

[0006] Preferably, a second AL-containing layer is further provided 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 That is the case.

[0007] Preferably, the ratio of the thicknesses of the first AL-containing layer, the second AL-containing layer, and the third AL-containing layer is 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, the metal layer comprising a titanium layer.

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

[0011] Preferably, when coating the first AL-containing layer using a copper-aluminum alloy, the coating speed for aluminum is 0.5 nm / second, and the coating speed for copper is 0.1 to 0.16 nm / second.

[0012] Preferably, the coating speed of the second AL-containing layer is 0.30 to 0.45 nm / second. [Effects of the Invention]

[0013] This invention solves the problems of ball mounting in the package and IMC defects after flip-chip mounting, and improves the main performance of the AL layer after film formation. [Brief explanation of the drawing]

[0014] [Figure 1] This image shows the inspection results for aluminum residue >20% in the present invention. [Figure 2] This image shows the inspection results for aluminum spillage in the present invention. [Figure 3] This image shows the result of passing the IMC inspection in this invention. [Figure 4] This image shows the result of failing the IMC inspection in this invention. [Figure 5] This is a product flowchart of the PAD layer coating process according to the present invention. [Figure 6] This image shows the morphological examination results of the first group in the present invention. [Figure 7] This image shows the results of the IMC interface inspection for the first group of the present invention. [Figure 8] This is a measurement image of the first group of gold balls in the present invention. [Figure 9] This image shows the morphological examination results of the second group in the present invention. [Figure 10] This image shows the results of the IMC interface inspection for the second group in the present invention. [Figure 11] This is a measurement image of the second group of gold balls in the present invention. [Figure 12]It is an image showing the morphological inspection results of the third group in the present invention. [Figure 13] It is an image showing the IMC interface inspection results of the third group in the present invention. [Figure 14] It is an image of the gold ball measurement of the third group in the present invention. [Figure 15] It is an image showing the morphological inspection results of the fourth group in the present invention. [Figure 16] It is an image showing the IMC interface inspection results of the fourth group in the present invention. [Figure 17] It is an image of the gold ball measurement of the fourth group in the present invention.

Embodiments for Carrying Out the Invention

[0015] In the drawings, the X-axis of the IMC interface diagram represents the horizontal coordinate, and the Y-axis represents the vertical coordinate. The value of the X-axis is calculated by taking the leftmost point of the metal residue mark as the reference point and measuring the distance to the rightmost point by moving the camera to the right. Thus, the width of the metal residue is obtained. In the same way, the width of the gold ball is also calculated.

[0016] Hereinafter, in order to better explain the object, technical means and advantages of the present invention, the present invention will be described in detail while referring to specific examples.

[0017] (Example 1) Regarding the TI+AL layer of the PAD layer, in the conventional coating process, the coating speed of the AL layer (2000 nm) is basically constant at 0.35 nm / second. After film formation, different degrees of changes occur in the surface characteristics of the AL material among different lots.

[0018] This example provides an aluminum film for the wafer pad layer and its coating method. Based on the product partial flowchart in FIG. 5, the coating speed of the AL layer in the pad layer process is divided, the 2000 nm AL layer is divided into multiple layers, the speed of the first AL layer (8OO nm) is changed to 0.5 nm / second, and the speed is controlled by the crystal oscillator of the coating apparatus. The hardness of aluminum is 100 g / cm 2The above was achieved. The second layer, the AL layer (800 nm), was coated at a speed of 0.35 nm / second, and the hardness of the aluminum was 60 g / cm². 2 ~80g / cm 2 The third layer, the AL layer (400 nm), was coated at a speed of 0.25 nm / second, and the hardness of the aluminum was 50 g / cm². 2 I made it so that it would be as follows.

[0019] Table 1 below shows some data results regarding the verification of the coating, and the conditions are as follows: 1) Conditions 1, 2, 3, and 4 are four verification DOEs, which mainly adjust the coating speed of the second and third layers, thereby changing the hardness of the AL layers of the second and third layers. Since the hardness increases with faster aluminum deposition speed and decreases with slower speed, the speed gradient method was selected for coating, starting at 0.5 nm / sec (0.5 nm / sec is the theoretical maximum value of the equipment), and the speed was reduced by 0.02 nm / sec increments using the gradient selection method to find a better state value that did not cause problems with IMC. 2) The purpose of annealing is to release stress on the wafer and improve the electrical curve of the wafer CP test. Annealing conditions: Annealed at 280°C for 5 hours. 3) Morphological measurement: The morphology of the product surface was observed under magnification using an OM machine (high-magnification microscope), and the measurement conditions were up to 5000x magnification. 4) For IMC measurement, after ball mounting and solder ball shear test, the coated surface of the PAD was observed at 200x magnification, and after flip-chip mounting and stacking, the aluminum coated surface of the gold balls on the substrate surface was observed at high magnification.

[0020] [Table 1]

[0021] Packaging process: Gold wires were mounted onto chip aluminum pads using a ball mounter while being heated to a high temperature (65°C or higher). The ball-mounted products were then pressed onto a circuit board, followed by ultrasonic heating (temperature controlled between 70 and 250°C), and finally soldered to the circuit board. Performance tests were conducted on the products using the ball mounting and lamination processes described above. The results are shown in Table 2 below.

[0022]

Table 2

[0023] <4. Result Explanation> Figure 1 is a high - magnification microscope inspection image 200,000 times that of the slice after flip - chip implementation. The used flip - chip implementation process is to press the ball - mounted product onto the substrate, and then after ultrasonic heating (the temperature is controlled at 70 - 250 °C), solder the substrate. In Figure 1, since the aluminum residue exceeded 20%, it was qualified, and the inspection result was pass. In Figure 2, there was aluminum overflow (NG), and the inspection result was fail.

[0024] 200 - fold inspection process: The best state of IMC is that the gold ball is mounted on the aluminum pad surface. During the test, the gold ball is pushed by the thrust of the mounter (30 - 60 g), and the size of IMC is calculated by width of metal residue÷width of gold ball×100. If the result exceeds 80%, it is judged as qualified. The IMC results in Figures 3 and 4 are pass and fail respectively. In Figures 1 - 4, OK and NG represent "the inspection result is pass" and "the inspection result is fail" respectively.

[0025] When the hardness of the outermost layer of the AL coating layer exceeds 50 g / cm 2 it is too hard for ball mounting in the packaging process, which causes poor IMC formation as shown in Figure 4. When the hardness of the innermost layer of the AL coating layer is less than 40 g / cm 2 it is too soft for flip - chip in the packaging process, which causes the problem of aluminum overflow as shown in Figure 2, and the aluminum layer is extruded and the performance becomes NG.

[0026] By using the method proposed in this invention (a layered coating method with different speeds similar to condition 4), the lower hard aluminum layer prevents overflow due to aluminum extrusion, and the upper soft aluminum layer achieves excellent IMC formation, completely resolving problems related to ball mounting and IMC after packaging (note that an aluminum residue of 20% or more is considered good in the industry). When the AL layer is coated with the above layered and different speeds and then packaged, no aluminum overflow occurs during ball mounting, no problems occur with eutectic formation of IMC, reliability (peel resistance and high temperature stability) is ensured, and there is no impact on electrical properties (CP test, frequency) (however, the values ​​differ for each product).

[0027] (Example 2) This embodiment provides an aluminum film for a wafer pad layer and a method for coating it. Based on the product flowchart in Figure 5, in the pad layer process, the AL coating layer was divided into two coating layers without changing the total thickness. Different proportions of Cu were added to the first layer Al (1000 nm), and the hardness of the AlCu alloy was harder than that of Al, and the hardness increased as the Cu content increased. During coating, the coating speed for aluminum was 0.5 nm / second, the copper content was in the range of 3% to 5%, and the coating speed was 0.1 to 0.16 nm / second, resulting in a hardness of 80 g / cm² for AlCu. 2 The process was controlled as described above. The second layer, the Al layer, was coated at a speed of 0.25 nm / second, and the hardness of the aluminum was set to 50 g / cm². 2 The following was maintained. This film formation method also made it possible to achieve a coating effect of soft aluminum on the outer layer and hard aluminum on the inner layer. The inspection results are shown in Table 3. Products formed from the coatings of groups 1, 2, and 3 in this example all passed the inspection shown in Figure 3.

[0028] [Table 3]

[0029] Finally, it should be noted that the above embodiments are for illustrative purposes only and do not limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it will be apparent to those skilled in the art that the technical means of the present invention can be modified or replaced with equivalents without departing from the essence and scope of the technical means of the present invention.

Claims

1. An AL layer structure coated on a wafer PAD layer material layer, comprising a first AL-containing layer and a third AL-containing layer, wherein the material of the first AL-containing layer includes one or more of aluminum, copper, or copper-aluminum alloy, the first AL-containing layer is connected to the 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 Therefore, the hardness of the third AL-containing layer is 50 g / cm². ２ The following describes an AL layer structure coated on a wafer PAD layer material layer, characterized in that the ratio of the thicknesses of the first AL-containing layer to the third AL-containing layer is 1:

1.

2. The AL layer structure coated on a wafer PAD layer material layer according to claim 1, characterized in that the copper content in the copper-aluminum alloy is 3% to 5%.

3. A second AL-containing layer is further provided 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 to 80 g / cm². ２ The AL layer structure coated on a wafer PAD layer material layer according to claim 1, characterized in that it is the same as described above.

4. The AL layer structure coated on a wafer PAD layer material layer according to claim 3, characterized in that the ratio of the thicknesses of the first AL-containing layer, the second AL-containing layer, and the third AL-containing layer is 2:1:

2.

5. The AL layer structure coated on a wafer PAD layer material layer according to claim 1, characterized in that the thickness is 1800 nm to 2500 nm.

6. The AL layer structure coated on the wafer PAD layer material layer according to claim 1, characterized in that 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.

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, characterized in that the coating speed of the first AL-containing layer is 0.45 to 0.5 nm / second, and the coating speed of the third AL-containing layer is 0.25 to 0.35 nm / second.

8. The method according to claim 3, characterized in that the coating speed of the second AL-containing layer is 0.30 to 0.45 nm / second.

9. The method according to claim 7, characterized in that, when the first AL-containing layer is coated using a copper-aluminum alloy, the coating speed for aluminum is 0.5 nm / second and the coating speed for copper is 0.1 to 0.16 nm / second.

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