Aluminum film for pad layer of wafer, and coating process therefor

Abstract

Provided in the present invention are an aluminum film for a pad layer of a wafer, and a coating process therefor. The aluminum film comprises 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, and the first Al-containing layer is connected to a base layer of the material of a pad layer of a wafer. The material of the third Al-containing layer is selected from aluminum. The hardness of the first Al-containing layer is greater than or equal to 100 g / cm2, and the hardness of the third Al-containing layer is less than or equal to 50 g / cm2. 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 greater than or equal to 100 g / cm2, the hardness of a second Al-containing layer is in the range of 60-80 g / cm2, and the hardness of the third Al-containing layer is less than or equal to 50 g / cm2. During preparation, the coating rate of the first Al layer is 0.45-0.5 nm / s, the coating rate of the second Al layer is 0.3-0.45 nm / s, and the coating rate of the third Al layer is 0.25-0.35 nm / s. The present invention solves the problem of poor IMC performance after bumping and flipping during packaging, and improves the key performance of the Al layer after film formation.

Description

Wafer pad layer aluminum film and plating process thereof TECHNICAL FIELD

[0001] The application belongs to the technical field of wafer plating processing, and particularly relates to a plating process of a plating AL material. BACKGROUND

[0002] At present, the M2 (PAD) layer material AL of wafer plating is generally plated to about 2000-2500 nm. The film forming structure is generally divided into three types. ① TI+AL ② TI+ALCU+TI+AL ③ TI+ALCU+TI+AU. The performances of the former two are unstable, and the cost of TI+ALCU+TI+AU is too high. In the actual application process, it is found that the important performance indicators of the AL material itself, such as stress, roughness and reflectivity, will change uncontrollably after the film forming is completed. The AL layer under different forms has different influences on the quality of packaging. Therefore, we need to change the wafer plating process, improve the plating indicators that affect the important performance of the AL layer, and focus on control. Thus, the important problem of wafer semiconductor is solved. SUMMARY

[0003] In order to overcome the deficiencies in the prior art, the application provides a wafer pad layer aluminum film and a plating process thereof.

[0004] To achieve the above-mentioned purpose, the application provides an AL layer structure plated on a wafer PAD layer material layer, which comprises 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 with the 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 greater than or equal to 100 g / cm 2 . The hardness of the third AL-containing layer is less than or equal to 50 g / cm 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 arranged between the first AL-containing layer and the third AL-containing layer. The material of the second AL-containing layer is selected from aluminum. The hardness of the second AL-containing layer is 60-80 g / cm 2 .

[0007] Preferably, the thickness ratio 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 1800nm-2500nm.

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

[0010] The application also provides a method for preparing the AL layer structure plated on the wafer PAD layer material, wherein the plating rate of the first AL-containing layer is 0.45-0.5nm / s, and the plating rate of the third AL layer is 0.25-0.35nm / s.

[0011] Preferably, when the first AL-containing layer is plated by using copper-aluminum alloy, the plating rate of aluminum is 0.5nm / s, and the plating rate of copper is 0.1-0.16nm / s.

[0012] Preferably, the plating rate of the second AL-containing layer is 0.30-0.45nm / s.

[0013] The application has the following advantages:

[0014] The application solves the problem of poor IMC after packaging flip-chip, and improves the key performance of the AL layer after film formation. BRIEF DESCRIPTION OF DRAWINGS

[0015] Fig. 1 is a detection effect display diagram of aluminum residue >20% in the application;

[0016] Fig. 2 is a detection effect display diagram of aluminum overflow in the application;

[0017] Fig. 3 is a display diagram of IMC detection passing effect in the application;

[0018] Fig. 4 is a display diagram of IMC detection not passing effect in the application;

[0019] Fig. 5 is a product flow chart of PAD layer plating process involved in the application;

[0020] Fig. 6 is a topography result detection diagram of group 1 in the application;

[0021] Fig. 7 is an IMC interface detection diagram of group 1 in the application;

[0022] Fig. 8 is a gold ball measurement diagram of group 1 in the application;

[0023] Fig. 9 is a topography result detection diagram of group 2 in the application;

[0024] Fig. 10 is an IMC interface detection diagram of group 2 in the application;

[0025] Fig. 11 is a gold ball measurement diagram of group 2 in the application;

[0026] Figure 12 is a topography result detection chart of Group 3 in the present application;

[0027] Figure 13 is an IMC interface detection chart of Group 3 in the present application;

[0028] Figure 14 is a gold ball measurement chart of Group 3 in the present application;

[0029] Figure 15 is a topography result detection chart of Group 4 in the present application;

[0030] Figure 16 is an IMC interface detection chart of Group 4 in the present application;

[0031] Figure 17 is a gold ball measurement chart of Group 4 in the present application;

[0032] Note: The IMC interface chart X axis is the horizontal coordinate, and the y axis is the vertical coordinate. The value of the X axis is obtained by selecting a point as a reference point at the leftmost edge of the residual gold stamp, moving the lens to the rightmost edge of the residual gold stamp, and obtaining the X value, which is the width of the residual gold. The gold ball width is also obtained in this way. DETAILED DESCRIPTION

[0033] For better purposes, technical solutions and advantages of the present application, the present application will be further described below in combination with specific examples.

[0034] Example 1

[0035] The conventional plating process of the TI+AL layer of the PAD layer is that the plating rate of the AL layer (2000nm) is the same, which is basically 0.35nm / s. After film formation, the surface characteristics of the AL material between different furnace times change to different degrees.

[0036] The present embodiment provides a wafer pad layer aluminum film and a plating processing technology thereof. Based on the product part flow chart in Figure 5, in the pad layer process, the plating rate of the AL layer is divided, and the 2000nm AL layer is divided into different layers. The rate of the first AL layer (800nm) is changed to 0.5nm / s. The control mode of the rate is the crystal oscillator control of the plating machine, and the hardness of the aluminum is ≥100g / cm 2 . The rate of the second AL layer (800nm) is 0.35nm / s, and the hardness of the aluminum is between 60g / cm 2 -80g / cm 2 . The rate of the third AL layer (400nm) is 0.25nm / s, and the hardness of the aluminum is ≤50g / cm 2 .

[0037] The following Table 1 parameters are some data results of the coating verification, wherein the conditions are explained as follows: ① Conditions 1, 2, 3, and 4 are four verifications of DOE. The DOE mainly adjusts the coating rate of the second layer and the third layer, and changes the hardness of the second layer and the third layer of AL layer. The faster the aluminum film forming speed, the greater the hardness, and the slower the speed, the smaller the hardness. Therefore, the film is plated by selecting a gradient rate, starting from 0.5 nm / s (0.5 nm / s is the theoretical maximum value of the equipment), and the gradient is selected by reducing the rate by 0.02 nm / s, in order to find a better state value, so that the IMC has no problem. ② The purpose of annealing is to release the stress of the wafer and improve the electrical property curve of the wafer cp test. The annealing condition is 280 degrees Celsius for 5 hours. ③ Appearance detection: OM machine (high magnification microscope) can magnify the appearance of the product surface, and the detection condition is magnified to 5000 times. ④ IMC measurement is after ball pushing, under high magnification 200 times, to see the coverage of the PAD surface. After flip pushing and stacking, high magnification is used to see the aluminum coverage of the gold ball on the substrate surface.

[0038] Table 1

[0039] Packaging process: The gold wire is heated to the chip aluminum pad by the ball mounting machine through high temperature (above 65℃). After ball mounting, the product is pressed onto the substrate by pressure, and then welded to the substrate after ultrasonic heating (temperature control at 70-250℃). The performance of the product is tested by the above ball mounting and pressing. The results are as follows in Table 2:

[0040] Table 2

[0041] 4. Result explanation

[0042] Fig. 1 is a 200,000 times high magnification detection diagram after flip and slicing. The flip process is as follows: After ball mounting, the product is pressed onto the substrate by pressure, and then welded to the substrate after ultrasonic heating (temperature control at 70-250℃). In Fig. 1, the aluminum residue is >20%, OK, the detection passes, and in Fig. 2, there is aluminum overflow (NG), the detection does not pass.

[0043] 200 times detection process: The best state of IMC is that the gold ball is planted on the surface of the aluminum pad. The gold ball is pushed by the machine force (30-60g), and the IMC size is according to the width of the residual gold ÷ the width of the gold ball * 100. The result >80% is qualified. The IMC results in Figs. 3 and 4 are detection pass and detection fail, respectively.

[0044] In Figs. 1-4, OK and NG respectively represent "detection pass" and "detection fail".

[0045] When the hardness of the outermost layer of the plated AL layer is >50 g / cm2 When the hardness is too large, it will cause the IMC problem as shown in Fig. 4. When the hardness of the innermost layer of the plated AL layer is < 40 g / cm 2 When the hardness is too small, it will cause the overflow problem as shown in Fig. 2, and the AL layer is squeezed out, causing performance NG.

[0046] The bottom layer of hard AL can ensure that the AL will not be squeezed out to cause the overflow problem, and the upper layer of soft AL can ensure that the IMC is very good, thus perfectly solving the problems of the post-packaging ball mounting and IMC (currently, the AL residue > 20% is considered to be a better state in the industry). When the AL layer is plated according to the above layered and speeded plating, the subsequent packaging can achieve the ball mounting without overflow, the eutectic property of the IMC will not be problematic, the reliability (debinding and high temperature) problems can be solved, and the electrical performance cp and frequency will not be affected (the values of each product are different).

[0047] Embodiment 2

[0048] The embodiment provides a wafer pad layer AL film and a plating processing technology thereof. Based on the product partial flowchart in Fig. 5, the pad layer technology is divided into two layers of plating in the total thickness of the plated AL layer without change. The first layer of Al (1000 nm) is added with different proportions of Cu, the hardness of the AlCu alloy is higher than that of Al, the hardness of the AlCu alloy will increase with the increasing of the proportion of Cu, the plating rate of the AL is 0.5 nm / s, the proportion of Cu is 3%-5%, the rate is 0.1-0.16 nm / s, and the hardness of the AlCu is controlled to be ≥ 80 g / cm 2 . The second layer of Al is plated at a rate of 0.25 nm / s, so that the hardness of the AL is ≤ 50 g / cm 2 . The film forming method also achieves the plating effect of the soft AL outer layer and the hard AL inner layer. The detection is shown in Table 3. The products formed after the plating of the groups 1, 2 and 3 in the embodiment can achieve the qualified results of Fig. 3.

[0049] Table 3

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the essence and scope of the technical solutions of the present application.

Claims

1. An AL layer structure plated on a wafer PAD layer material layer, characterized in that: The first AL-containing layer and the third AL-containing layer, 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 with the base layer of 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 greater than or equal to 100 g / cm 2 , the hardness of the third AL-containing layer is less than or equal to 50 g / cm 2 , and the thickness ratio of the first AL-containing layer and the third AL-containing layer is 1:

1.

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

3. The AL layer structure of a wafer PAD layer material layer coated with a film according to claim 1, characterized in that: A second AL-containing layer is arranged between the first AL-containing layer and the third AL-containing layer, the material of the second AL-containing layer being selected from the group consisting of aluminum, the hardness of the second AL-containing layer being 60-80 g / cm 2 .

4. The AL layer structure coated on the wafer PAD layer material layer according to claim 3, characterized in that: The thickness ratio 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 of a wafer PAD layer material layer coated with a film according to claim 1, characterized in that: The thickness of the AL layer structure is 1800nm-2500nm.

6. The AL layer structure of a wafer PAD layer material layer coated with a film according to claim 1, characterized in that: The base layer of the wafer PAD layer material includes a substrate layer and a metal layer, and the metal layer includes a titanium layer.

7. A method for preparing the AL layer structure coated on the wafer PAD layer material layer according to any one of claims 1-6, characterized in that: The plating rate of the first AL-containing layer is 0.45-0.5nm / s, and the plating rate of the third AL layer is 0.25-0.35nm / s.

8. The method of claim 7, wherein: The plating rate of the second AL-containing layer is 0.30-0.45nm / s.

9. The method of claim 7, wherein: When the copper-aluminum alloy is used to plate the first AL-containing layer, the plating rate of aluminum is 0.5nm / s, and the plating rate of copper is 0.1-0.16nm / s.

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