Wafer pad layer aluminum film and coating processing technology thereof

Abstract

The invention provides a wafer pad layer aluminum film and a coating processing technology thereof, the wafer pad layer 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, the first AL-containing layer is connected with a base layer of a 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 >, and the thickness of the first AL-containing layer is greater than or equal to 10 mm. The hardness of the third AL-containing layer is smaller than or equal to 50 g / cm < 2 >, 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 larger than or equal to 100 g / cm < 2 >, the hardness of the second AL-containing layer ranges from 60 g / cm < 2 > to 80 g / cm < 2 >, and the hardness of the third AL-containing layer is smaller than or equal to 50 g / cm < 2 >. During preparation, the coating rate of the first AL layer ranges from 0.45 nm / s to 0.5 nm / s, the coating rate of the second AL layer ranges from 0.3 nm / s to 0.45 nm / s, and the coating rate of the third AL layer ranges from 0.25 nm / s to 0.35 nm / s. According to the invention, the problem of poor IMC after packaging ball mounting inversion is solved, and the key performance of the AL layer after film forming is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wafer coating processing, and specifically relates to a coating process for coated AL materials. The optimized process promotes ball implantation, flip-chip and other processes in post-process packaging, improves IMC (intermetallic compound) performance, and promotes the development of wafer semiconductor coating packaging. Background Art

[0002] At present, the M2 (PAD) layer material AL of wafer coating is generally coated with about 2000nm-2500nm. There are generally three types of film structures. ①TI+AL②TI+ALCU+TI+AL③TI+ALCU+TI+AU. The performance of the first two is unstable, and the cost of TI+ALCU+TI+AU is too high. In the process of actual application, it is found that after the film is formed, the important performance indicators such as stress, roughness, and reflection value of the AL material itself will undergo uncontrollable changes. The AL layer in different forms has different effects on the quality of the package. Therefore, we need to change the wafer coating process, improve the process of the coating indicators that affect the important performance of the AL layer, and focus on control. Thereby solving this important problem of wafer semiconductors. Summary of the invention

[0003] In order to overcome the deficiencies in the prior art, the present invention provides a wafer pad layer aluminum film and a coating processing technology thereof.

[0004] To achieve the above object, the present invention provides 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 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, and the hardness of the first AL-containing layer is greater than or equal to 100g / 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 to the third AL-containing layer is 1:1.

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

[0006] Preferably, a second Al-containing layer is 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 / 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 present invention also provides a method for preparing the AL layer structure coated on the wafer PAD layer material layer, wherein the coating rate of the first AL-containing layer is 0.45-0.5nm / s, and the coating rate of the third AL layer is 0.25-0.35nm / s.

[0011] Preferably, when copper-aluminum alloy is used to plate the first Al-containing layer, the coating rate of aluminum is 0.5 nm / s, and the coating rate of copper is 0.1-0.16 nm / s.

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

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

[0014] The present invention solves the problem of poor IMC after package ball implantation and flip-chip, and improves the key performance of the AL layer after film formation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a graph showing the detection effect of aluminum residue>20% in the present invention;

[0016] Figure 2 This is a diagram showing the detection effect of aluminum overflow in the present invention;

[0017] Figure 3 This is a diagram showing the effect of IMC detection in the present invention;

[0018] Figure 4 This is a diagram showing the effect of failing the IMC test in the present invention;

[0019] Figure 5 This is a product flow chart of the PAD layer coating process involved in the present invention;

[0020] Figure 6 This is a test diagram of the morphological results of Group 1 in the present invention;

[0021] Figure 7 This is the IMC interface detection diagram of Group 1 in the present invention;

[0022] Figure 8 This is the gold ball calculation diagram of Group 1 in the present invention;

[0023] Fig. 9 This is a test diagram of the morphological results of Group 2 in the present invention;

[0024] Fig.10This is the IMC interface detection diagram of Group 2 in the present invention;

[0025] Fig.11 This is the gold ball calculation diagram of Group 2 in the present invention;

[0026] Fig.12 This is a test diagram of the morphological results of Group 3 in the present invention;

[0027] Fig.13 This is the IMC interface detection diagram of Group 3 in the present invention;

[0028] Fig.14 This is the gold ball calculation diagram of Group 3 in the present invention;

[0029] Fig.15 This is a test diagram of the morphological results of Group 4 in the present invention;

[0030] Fig.16 This is the IMC interface detection diagram of group 4 in the present invention;

[0031] Fig.17 This is the gold ball calculation diagram of Group 4 in the present invention;

[0032] Note: IMC interface Figure X The x-axis is the horizontal coordinate, the y-axis is the vertical coordinate, and the x-axis value is obtained by selecting a point on the leftmost side of the residual gold seal as the reference point, moving the camera to the right to the rightmost side of the residual gold seal, and obtaining the x-value, which is the width of the residual gold. The width of the gold ball is also obtained in this way. DETAILED DESCRIPTION

[0033] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present application will be further described below in conjunction with specific embodiments.

[0034] Example 1

[0035] The TI+AL layer of the PAD layer, the conventional coating process is that the coating rate of the AL layer (2000nm) is the same, basically 0.35nm / s. After film formation, the surface properties of the AL material in different furnaces change to varying degrees.

[0036] This embodiment provides a wafer pad layer aluminum film and its coating process. Figure 5 Based on the product flow chart, in the pad layer process, the 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 rate is controlled by the crystal oscillator of the coating machine, so that the hardness of aluminum is ≥100g / cm 2 The second Al layer (800nm) is deposited at a rate of 0.35nm / s, making the hardness of aluminum 60g / cm2 -80g / cm 2 The third AL layer (400nm) is coated at a rate of 0.25nm / s to keep the hardness of aluminum at ≤50g / cm 2 .

[0037] The following parameters in Table 1 are some data results of coating verification, among which the conditions are explained: ① Conditions 1, 2, 3, and 4 are 4 verified DOEs. DOE mainly adjusts the coating rate of the second and third layers and changes the hardness of the second and third AL layers. The faster the aluminum film forming speed, the greater the hardness, and the slower the speed, the smaller the hardness. Therefore, we choose to coat the film in a rate gradient manner, starting from 0.5nm / s (0.5nm / s is the theoretical maximum value of the equipment). The gradient selection method reduces the rate by 0.02nm / s to find a better state value so that there is no problem with IMC. ② The purpose of annealing is to release the stress of the wafer and improve the electrical curve of the wafer cp test. Annealing conditions: annealing at 280 degrees Celsius for 5 hours. ③ Morphology detection: The OM machine (high-power microscope) can magnify the morphology of the product surface. The detection condition is to magnify it to 5000 times. ④IMC measurement is to observe the coverage of PAD surface at 200 times magnification after ball implantation and to observe the aluminum coverage of gold ball on substrate surface at high magnification after flip chip stacking.

[0038] Table 1

[0039]

[0040]

[0041] Packaging process: The gold wire is heated at high temperature (above 65°C) by a ball planting machine and installed on the chip aluminum pad. The ball-planted product is pressed onto the substrate by pressure, and then welded to the substrate after ultrasonic heating (temperature controlled at 70-250°C). Through the above ball planting and pressing, the product performance is tested. The results are shown in Table 2:

[0042] Table 2

[0043]

[0044] 4. Results

[0045] Figure 1 This is a 200,000x high-power microscope inspection image after flip-chip slicing. The flip-chip process used is: the ball-implanted product is pressed onto the substrate by pressure, and then welded to the substrate after ultrasonic heating (temperature controlled at 70-250°C). Figure 1 In the test, aluminum residue>20%, OK, the test passed, Figure 2 Aluminum overflow (NG) occurs and the test fails.

[0046] The 200x inspection process is as follows: the best state of IMC is that the gold ball is planted on the surface of the aluminum pad. Through the test, the gold ball is pushed by the machine thrust (30-60g). The size of IMC is calculated according to the width of the residual gold ÷ the width of the gold ball * 100. The result >80% is qualified. Figure 3 , Figure 4 The IMC results are test passed and test failed.

[0047] Figure 1-4 In the table, OK and NG respectively mean "test passed" and "test failed".

[0048] When the hardness of the outermost layer of the coating AL layer is greater than 50g / cm 2 At this time, the hardness is too high for the package ball, which will cause Figure 4 The same IMC is not good. When the hardness of the innermost layer of the coating AL layer is less than 40g / cm 2 At the same time, the hardness is too small for the flip-chip package, which will cause Figure 2 The same problem of aluminum overflow occurs, and the aluminum layer is squeezed out, resulting in poor performance.

[0049] The process of the present invention is similar to the layering and rate coating of condition 4. The bottom layer of hard aluminum can ensure that the aluminum will not be squeezed out to cause aluminum overflow, and the upper layer of soft aluminum can ensure that the IMC is very good, which perfectly solves the problem of ball planting and IMC after packaging (currently, aluminum residue>20% is considered a relatively good state in the industry). The AL layer is plated according to the above layering and rate coating. When packaging is performed later, there will be no aluminum overflow during ball planting, and there will be no problem with the eutectic property of IMC. Reliability (demolding, high temperature) and other problems can be solved, and the electrical performance cp and frequency will not be affected (the value of each product is different).

[0050] Example 2

[0051] This embodiment provides a wafer pad layer aluminum film and its coating process. Figure 5 Based on the product part flow chart, in the pad layer process, the total thickness of the coated AL layer is divided into two layers of coating. Different proportions of Cu are added to the first layer of Al (1000nm). The hardness of AlCu alloy is harder than Al. As the Cu content continues to increase, the hardness of AlCu alloy will also increase. During coating, the coating rate of aluminum is 0.5nm / s, the proportion of copper is in the range of 3%-5%, the rate is 0.1-0.16nm / s, and the hardness of AlCu is controlled to be ≥80g / cm 2 The second Al layer is deposited at a rate of 0.25nm / s, making the hardness of aluminum ≤50g / cm 2This film forming method also achieves the coating effect of the outer layer being soft aluminum and the inner layer being hard aluminum. The test results are shown in Table 3. The products formed by the coating of groups 1, 2, and 3 in this embodiment can all achieve Figure 3 Qualified test results.

[0052] Table 3

[0053]

[0054]

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. An AL layer structure coated on a wafer PAD layer material layer, characterized in that: The invention comprises a first Al-containing layer and a third Al-containing layer, wherein the material of the first Al-containing layer comprises 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 greater than or equal to 100g / 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 to 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 content of the copper-aluminum alloy is 3%-5%.

3. The AL layer structure coated on the wafer PAD layer material layer according to claim 1, characterized in that: A second Al-containing layer is disposed 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 .

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 coated on the wafer PAD layer material layer according to claim 1, characterized in that: The thickness of the Al layer structure is 1800nm-2500nm.

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 includes a substrate layer and a metal layer, and the metal layer includes a titanium layer.

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

8. The method according to claim 7, characterized in that: The coating rate of the second Al-containing layer is 0.30-0.45 nm / s.

9. The method according to claim 7, characterized in that: When the first Al-containing layer is plated with a copper-aluminum alloy, the aluminum plating rate is 0.5 nm / s, and the copper plating rate is 0.1-0.16 nm / s.

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