Quantitative characterization of polyimide and copper-plated interface bonding force test sample and preparation method

Abstract

The present application relates to a quantitative characterization of the bonding force between polyimide and copper-plated interface test sample and preparation method, comprising the following steps: solidifying a layer of polyimide film on a silicon wafer; preparing a copper layer on the polyimide film, and protecting the copper layer from oxidation; wafer dicing treatment, cutting into a certain size of polyimide and copper-plated interface sample; the upper surface of the polyimide and copper-plated interface sample is welded together with the bottom surface of the tensile clamp, and the integration of the test sample and the tensile clamp is completed. The present application avoids the method of preparing a copper layer on the silicon wafer, and then preparing a polyimide film on the copper layer in a specified pattern, but instead, a polyimide film is first prepared on the silicon wafer in its entirety, then a copper-plated layer is prepared on the polyimide film in a specified pattern, and a tensile clamp is welded on the copper layer. The high-strength weld reduces the risk of fracture of the non-test surface during the test process, thereby achieving the quantitative characterization of the bonding force between the polyimide and the copper-plated interface.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and in particular to a test sample for quantitatively characterizing the interfacial adhesion between polyimide and copper plating and a preparation method thereof. BACKGROUND

[0002] Currently, the test method for the interfacial adhesion strength between polyimide and copper plating layer is to vertically stretch the polyimide after bonding with an external clamp, and to evaluate the interfacial adhesion strength by the area of the fracture surface and the tensile force when the interface is broken.

[0003] The existing test method has the following defects:

[0004] Firstly, through verification, most of the fracture surfaces in the tensile test are located at the bonding glue, because the bonding glue itself has a low strength and has a risk of breaking, and thus the interfacial adhesion between polyimide and copper plating layer cannot be quantitatively characterized.

[0005] Secondly, after the bonding glue is pre-fixed, a heat treatment is needed to solidify the bonding glue, and during this process, an additional force perpendicular to the bonding surface needs to be applied to ensure that the interface between the polyimide and the copper plating layer is perpendicular to the free end of the tensile test, and it is difficult to achieve vertical fixation by using a conventional spring clamp.

[0006] In addition, research shows that the adhesion strength between metal and polyimide is mainly due to the chemical interaction between the metal layer and the functional groups of polyimide, and the heat treatment affects the functional group concentration of the interface between polyimide and copper plating layer, thereby affecting the interfacial adhesion, and the existing test sample cannot evaluate the influence of the subsequent reflow process on the interface between polyimide and copper plating layer. SUMMARY

[0007] In view of the above-mentioned defects in the existing production technology, the present application provides a test sample for quantitatively characterizing the interfacial adhesion between polyimide and copper plating and a preparation method thereof, so as to realize accurate testing of the interfacial adhesion between polyimide and copper plating layer.

[0008] The technical solution adopted by the present application is as follows:

[0009] A preparation method of a test sample for quantitatively characterizing the interfacial adhesion between polyimide and copper plating, comprising the following steps:

[0010] providing a silicon wafer, and solidifying a layer of polyimide film on the silicon wafer;

[0011] preparing a copper layer on the polyimide film, and performing oxidation protection on the copper layer to prepare an oxidation protection layer;

[0012] dicing the wafer to separate the polyimide and copper plating interface sample;

[0013] A stretching clamp is provided, and the upper surface of the polyimide and copper-plated interface sample is welded to the bottom surface of the stretching clamp to complete the integrated preparation of the test sample and the stretching clamp.

[0014] As a further improvement of the above technical solution:

[0015] The silicon wafer is first prepared with silicon oxide, and the surface of the silicon oxide is treated for hydrophilicity, so that the polyimide film forms a good bonding force after solidification.

[0016] The surface is treated for hydrophilicity, specifically, a pretreatment process of plasma bombardment or dry etching.

[0017] A copper layer is prepared on the polyimide film, specifically, a copper layer is prepared on the polyimide film by electroplating, PVD, or CVD process; the area of the upper surface of the polyimide and copper-plated interface sample should be less than the ratio of the limit tensile force of the test equipment to the estimated interface tensile strength.

[0018] The copper layer is protected from oxidation, specifically, a gold layer is prepared on the upper surface of the copper layer by electroless plating, or a nickel layer is prepared by electroplating.

[0019] The upper surface of the polyimide and copper-plated interface sample is welded to the bottom surface of the stretching clamp, specifically:

[0020] The limiting tool is placed on the polyimide and copper-plated interface sample from top to bottom before placing the solder, and the solder and the stretching clamp are placed in the positioning holes of the limiting tool in turn; to ensure that the interface to be tested is perpendicular to the stretching test force direction, and to facilitate the alignment of the anti-oxidation layer and the stretching clamp during the welding process, and to isolate the molten solder from the polyimide and copper-plated interface during the high-temperature process.

[0021] The polyimide and copper-plated interface sample, limiting tool, solder, and stretching clamp are placed together in a chain furnace or vacuum sintering furnace, and the temperature is raised to above the melting point of the solder under a protective atmosphere to complete the welding of the anti-oxidation layer and the stretching clamp.

[0022] After cooling to room temperature, the limiting tool is removed from the top to complete the integrated preparation of the test sample and the stretching clamp.

[0023] The solder adopts a solder sheet with an area smaller than that of the polyimide and copper-plated interface sample, to prevent the solder from overflowing onto the polyimide and copper-plated interface during the melting process and affecting the test results.

[0024] The upper surface of the polyimide and copper-plated interface sample is welded with the bottom surface of the tensile clamp, specifically, the upper surface of the polyimide and copper-plated interface sample is consistent with the bottom surface of the tensile clamp in shape and size, and the extension of the tensile clamp can be used as a free end for stretching, so as to avoid that the solder layer is broken in advance due to insufficient strength during the test.

[0025] The limiting tool is a hollow integrated structure and is made of ceramic material, comprising a tool body for vertical limiting and a base arranged below the tool body, and a groove is arranged below the base; in use, the polyimide film is embedded in the groove, and the upper part of the silicon wafer is embedded in the groove, so as to ensure that the limiting tool is vertical.

[0026] The inner through hole of the tool body comprises a first through hole at the upper part and a second through hole at the lower part, the inner diameter of the first through hole is smaller than that of the second through hole, the solder and the lower end of the tensile clamp are located in the first through hole, and the copper layer and the oxidation prevention layer are located in the second through hole, so as to prevent the solder from overflowing to the polyimide and copper-plated interface during the melting process and affecting the test result.

[0027] A test sample for quantitatively characterizing the bonding force between polyimide and copper-plated interface is prepared by the preparation method, the test sample is an integrated structure, comprising a silicon wafer, silicon oxide, a polyimide film fixed on the silicon oxide, a copper layer, solder, and a tensile clamp from bottom to top; an interface for bonding force test is formed between the polyimide film and the copper layer.

[0028] As a further improvement of the above technical solution:

[0029] The copper layer is provided with an oxidation prevention layer, and the oxidation prevention layer is a gold layer or a nickel layer;

[0030] The area of the upper surface of the copper layer should be smaller than the ratio of the limit tensile force of the test equipment to the estimated interface tensile strength;

[0031] The area of the solder sheet used by the solder is smaller than the area of the copper layer.

[0032] The beneficial effects of the present application are as follows:

[0033] The present application avoids the method of preparing a copper layer on the silicon wafer in whole, and then preparing a polyimide film on the copper layer in a specified pattern, but instead, a polyimide film is first prepared on the silicon wafer in whole, then a copper layer is prepared on the polyimide film in a specified pattern, and a tensile clamp is welded on the copper layer, the high-strength welding point reduces the risk of fracture of the non-test surface during the test, so as to realize the quantitatively characterizing the bonding force between the polyimide and the copper-plated interface.

[0034] The present application also includes the following advantages:

[0035] (1) The limiting tool is used in the welding process to constrain the tensile clamp to be welded, so as to realize the perpendicularity of the free end of the tensile clamp to the welding layer and the interface to be tested, isolate the solder during the welding temperature rising process, realize the alignment of the welding layer, ensure the accuracy of the test result, facilitate the operation, and can be recycled subsequently.

[0036] (2) A groove is arranged below the limiting tool base, when in use, the polyimide film is embedded in the groove, and the upper part of the silicon wafer is embedded in the groove, so as to ensure the perpendicularity of the limiting tool and avoid affecting the verticality of the free state of the base; the first through hole and the second through hole are arranged in the tool body, the inner diameter of the first through hole is smaller than that of the second through hole, the solder and the lower end of the tensile clamp are located in the first through hole, and the copper layer and the oxidation prevention layer are located in the second through hole, so as to prevent the solder from overflowing to the polyimide and copper-plated interface during the melting process and affecting the test result.

[0037] (3) The test sample of the interface bonding force between the polyimide and the copper-plated layer is reasonably designed to quantitatively characterize the interface bonding force; the sample can be reflowed for multiple times, the influence of the subsequent heat treatment process on the interface bonding force can be evaluated, the influence of multiple reflows on the interface between the polyimide and the copper-plated layer can be evaluated, so as to take this test method as a process improvement standard or material selection standard for optimizing the interface bonding force between the polyimide and the copper-plated layer under the comprehensive evaluation of multiple processes. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is an exploded view of the assembly of the polyimide and copper-plated interface sample, limiting tool and tensile clamp in the application.

[0039] Figure 2 It is a structural schematic view of the combination of the polyimide film and the copper layer in the application.

[0040] Figure 3 It is a structural schematic view of the assembly after the welding of the polyimide and copper-plated interface sample, limiting tool and tensile clamp in the application.

[0041] Figure 4 It is Figure 3 a sectional view of A-A section in the application.

[0042] Figure 5 It is a structural schematic view of the limiting tool in one embodiment of the application.

[0043] Figure 6 It is a sectional view of the limiting tool in another embodiment of the application.

[0044] Figure 7 It is a sectional view of the assembly after the welding of the polyimide and copper-plated interface sample, limiting tool and tensile clamp in another embodiment of the application.

[0045] Figure 8This is a schematic diagram of the structure of the test sample in this invention.

[0046] Wherein: 100, silicon wafer; 110, silicon oxide; 200, polyimide film; 300, copper layer; 310, anti-oxidation layer; 400, stretching fixture; 500, solder; 610, tooling body; 611, first through hole; 612, second through hole; 620, base; 621, groove. Detailed Implementation

[0047] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0048] like Figures 1-4 As shown in this embodiment, the method for preparing the test sample for quantitative characterization of the interfacial adhesion between polyimide and copper plating includes the following steps:

[0049] A silicon wafer 100 is provided, and a polyimide film 200 is cured on the silicon wafer 100.

[0050] Specifically, silicon oxide 110 is first prepared on silicon wafer 100, and the surface of silicon oxide 110 is subjected to hydrophilic treatment. The surface hydrophilic treatment is carried out by plasma bombardment or dry etching pretreatment process so that the polyimide film 200 can form a good bonding force with it after curing.

[0051] A copper layer 300 is prepared on a polyimide film 200, and an anti-oxidation layer 310 is prepared to protect the copper layer 300 from oxidation.

[0052] Specifically, a copper layer 300 is prepared on a polyimide film 200 by electroplating, PVD, and CVD processes; the area of ​​the upper surface of the polyimide-copper interface sample should be less than the ratio of the ultimate tensile force of the test equipment to the estimated tensile strength of the interface.

[0053] To protect the copper layer 300 from oxidation, specifically, a gold layer is prepared on the upper surface of the copper layer 300 by chemical plating or a nickel layer is prepared by electroplating, so as to achieve the effect of protecting the copper layer 300 from oxidation.

[0054] The wafer was diced, and the resulting polyimide-copper interface sample was shown in the image. Figure 2 The cutting size should match the bottom surface of the tensile fixture 400 (suitable for universal testing).

[0055] A tensile fixture 400 is provided to weld the upper surface of the polyimide-copper interface sample to the bottom surface of the tensile fixture 400, thereby completing the integrated preparation of the test sample and the tensile fixture 400.

[0056] Specifically:

[0057] See Figure 1 and4 Before placing the solder 500, the limiting tool is placed on the polyimide and copper-plated interface sample from top to bottom, and the solder 500 and the tensile clamp 400 are placed in the positioning holes of the limiting tool in turn; to ensure that the interface to be tested is perpendicular to the tensile test force direction, and to facilitate the alignment of the anti-oxidation layer 310 and the tensile clamp 400 during the welding process, and to isolate the molten solder 500 from the polyimide and copper-plated interface during the high-temperature process.

[0058] After the positioning of the polyimide and copper-plated interface sample, the limiting tool, the solder 500, and the tensile clamp 400 are integrated into a chain furnace or a vacuum sintering furnace, and the temperature is raised to above the melting point of the solder 500, and the welding of the anti-oxidation layer 310 and the tensile clamp 400 is completed in a protective atmosphere.

[0059] After cooling to room temperature, the limiting tool is removed from the top, and the integration of the test sample and the tensile clamp 400 is completed, which is used for the quantitative characterization of the bonding force test of the polyimide and copper-plated interface.

[0060] Further, the area of the solder sheet used by the solder 500 is smaller than the area of the polyimide and copper-plated interface sample, so as to prevent the solder 500 from overflowing onto the polyimide and copper-plated interface during the melting process and affecting the test results.

[0061] Further, the solder 500 selected in the welding process is consistent with the welding method used in the subsequent ball planting process, so as to consider the influence of the thermal mismatch generated by the subsequent ball planting process on the stress of the polyimide and copper-plated interface.

[0062] In one embodiment, the upper surface of the polyimide and copper-plated interface sample is consistent with the bottom surface of the tensile clamp 400 in shape and size, and the extended part of the tensile clamp 400 can serve as the free end of the tensile clamp, so as to ensure sufficient connection strength between the upper surface of the polyimide and copper-plated interface sample and the bottom surface of the tensile clamp 400, and to avoid premature fracture of the solder layer due to insufficient strength during the test.

[0063] As shown in Figure 5 , the limiting tool is a hollow integrated structure, which includes a tool body 610 for vertical limiting, a base 620 arranged below the tool body 610, and a groove 621 arranged below the base 620; during use, the polyimide film 200 is embedded in the groove 621, and the upper part of the silicon wafer 100 is embedded in the groove 621, so as to ensure the verticality of the limiting tool.

[0064] Further, the limiting tool is made of ceramic material and has an integrated structure, which can be repeatedly used for welding interface samples of the same size.

[0065] In one embodiment, as shown in Figure 6 and 7As shown, the inner through hole of the tool body 610 includes a first through hole 611 located above and a second through hole 612 located below, the inner diameter of the first through hole 611 is smaller than that of the second through hole 612, the solder 500 and the lower end of the tensile clamp 400 are located in the first through hole 611, and the copper layer 300 and the oxidation prevention layer 310 are located in the second through hole 612, so as to prevent the solder 500 from overflowing to the interface between the polyimide and the copper plating during the melting process and affecting the test results.

[0066] The above preparation method avoids the method of preparing the copper layer 300 on the silicon wafer 100 in whole, and then preparing the polyimide film 200 on the copper layer 300 in a specified pattern, but instead, the polyimide film 200 is prepared on the silicon wafer 100 in whole, then the copper plating layer 300 is prepared on the polyimide film 200 in a specified pattern, and the tensile clamp 400 is welded on the copper layer 300, the high-strength welding point reduces the risk of fracture of the non-test surface during the test process, so as to realize the quantitative characterization of the bonding force between the interface of the polyimide and the copper plating layer.

[0067] As shown, Figure 8 The test sample for quantitatively characterizing the bonding force between the polyimide and the copper plating interface of the embodiment is prepared by the above preparation method, the test sample is an integrated structure, including the silicon wafer 100, the silicon oxide 110, the polyimide film 200 solidified on the silicon oxide 110, the copper layer 300, the solder 500, and the tensile clamp 400 fixed in sequence from bottom to top; the interface for bonding force test is formed between the polyimide film 200 and the copper layer 300.

[0068] Further, the surface of the silicon oxide 110 is treated for hydrophilicity by using plasma bombardment and dry etching pretreatment process, so that the polyimide film 200 forms good bonding force with the silicon oxide 110 after solidification.

[0069] The oxidation prevention layer 310 is provided on the copper layer 300, and the oxidation prevention layer 310 is a gold layer or a nickel layer, so as to realize the oxidation prevention and protection effect of the copper layer 300.

[0070] The area of the upper surface of the copper layer 300 should be less than the ratio of the limit tensile force of the test equipment to the estimated interface tensile strength, and the area of the upper surface of the copper layer 300 is 3-20 mm, preferably 5 mm, so as to realize the best test requirement of quantitatively characterizing the bonding force between the polyimide and the copper plating interface.

[0071] The area of the solder sheet used for the solder 500 is smaller than the area of the copper layer 300, so as to prevent the solder 500 from overflowing to the interface between the polyimide and the copper plating during the melting process and affecting the test results.

[0072] The test sample of the interface bonding force between the above polyimide and the copper plating layer is used to quantitatively characterize the interface bonding force, the sample can be reflowed for multiple times, the influence of the heat mismatch introduced by the subsequent heat treatment process on the interface bonding force can be evaluated at the same time, the influence of multiple reflows on the interface between the polyimide and the copper plating layer is evaluated, and the test method is used as a process improvement standard or material selection standard for optimizing the interface bonding force between the polyimide and the copper plating layer under the comprehensive evaluation of multiple processes.

[0073] The above description is an explanation of the application, not a limitation of the application, the scope of the application is defined in the claims, and any form of modification within the protection scope of the application can be made.

Claims

1. A method for preparing a test sample for quantitatively characterizing the interfacial adhesion between polyimide and copper plating, characterized by, The method comprises the following steps: providing a silicon wafer (100), solidifying a layer of polyimide film (200) on the silicon wafer (100); preparing a copper layer (300) on the polyimide film (200) and protecting the copper layer (300) from oxidation to prepare an anti-oxidation layer (310); wafer dicing treatment to cut into a polyimide and copper-plated interface sample; providing a tensile clamp (400), welding the upper surface of the polyimide and copper-plated interface sample to the bottom surface of the tensile clamp (400) to complete the integrated preparation of the test sample and the tensile clamp (400); welding the upper surface of the polyimide and copper-plated interface sample to the bottom surface of the tensile clamp (400), specifically: placing the limiting tool from top to bottom on the polyimide and copper-plated interface sample before placing the solder (500), placing the solder (500) and the tensile clamp (400) in the positioning hole of the limiting tool in sequence; to ensure that the interface to be tested is perpendicular to the tensile test force direction, and to facilitate the alignment of the anti-oxidation layer (310) and the tensile clamp (400) during the welding process, and to isolate the molten solder (500) and the polyimide and copper-plated interface during the high temperature process; placing the polyimide and copper-plated interface sample, the limiting tool, the solder (500) and the tensile clamp (400) integrally into a chain furnace or a vacuum sintering furnace, heating to a temperature above the melting point of the solder (500), and completing the welding of the anti-oxidation layer (310) and the tensile clamp (400) in a protective atmosphere; after cooling to room temperature, removing the limiting tool from above to complete the integrated preparation of the test sample and the tensile clamp (400).

2. The method of claim 1, wherein the test sample is prepared by: The silicon wafer (100) is first prepared with a silicon oxide layer (110), and the surface of the silicon oxide layer (110) is treated for hydrophilicity to enable the polyimide film (200) to form good bonding force after solidification. The surface is treated for hydrophilicity, specifically, using a plasma bombardment or dry etching pretreatment process.

3. The method of claim 1, wherein the test sample is prepared by: The copper layer (300) is prepared on the polyimide film (200), specifically, through electroplating, PVD or CVD process to prepare the copper layer (300) on the polyimide film (200); the area of the upper surface of the polyimide and copper-plated interface sample should be less than the ratio of the limit tensile force of the test equipment to the estimated interface tensile strength.

4. The method of claim 1, wherein the test sample is prepared by: The copper layer (300) is protected from oxidation, specifically, a gold layer is prepared on the upper surface of the copper layer (300) by electroless plating, or a nickel layer is prepared by electroplating.

5. The method of claim 1, wherein the test sample is prepared by: The solder (500) uses a solder sheet with an area smaller than that of the polyimide and copper-plated interface sample, to prevent the solder (500) from overflowing onto the polyimide and copper-plated interface during the melting process and affecting the test results.

6. The method of claim 1, wherein the test sample is prepared by: The limiting tool is a hollow integrated structure, comprising a tool body (610) for vertical limiting and a base (620) arranged below the tool body (610), and a groove (621) is arranged below the base (620); in use, the polyimide film (200) is embedded in the groove (621), and the upper part of the silicon wafer (100) is embedded in the groove (621) to ensure that the limiting tool is vertical.

7. The method of claim 6, wherein the test sample is prepared by, The inner through hole of the tool body (610) includes a first through hole (611) on the upper side and a second through hole (612) on the lower side, the inner diameter of the first through hole (611) is smaller than that of the second through hole (612), the solder (500) and the lower end of the tensile clamp (400) are located in the first through hole (611), and the copper layer (300) and the oxidation prevention layer (310) are located in the second through hole (612), so as to prevent the solder (500) from overflowing to the polyimide and copper plating interface during the melting process and affecting the test result.

8. A test sample for quantifying the interfacial adhesion between a polyimide and a copper plating, characterized by, The test sample prepared by the preparation method in any one of claims 2-7 is an integrated structure, which comprises, from bottom to top, a silicon wafer (100), silicon oxide (110), a polyimide film (200) fixed on the silicon oxide (110), a copper layer (300), solder (500), and a tensile clamp (400); and an interface for bonding force test is formed between the polyimide film (200) and the copper layer (300).

9. The test sample for quantifying the polyimide to copper interface bond strength of claim 8 wherein, The copper layer (300) is provided with an oxidation prevention layer (310), and the oxidation prevention layer (310) is a gold layer or a nickel layer; The area of the upper surface of the copper layer (300) should be smaller than the ratio of the limit tensile force of the test equipment to the estimated interface tensile strength. The solder (500) adopts a solder sheet with an area smaller than that of the copper layer (300). The copper layer (300) is provided with an oxidation prevention layer (310), and the oxidation prevention layer (310) is a gold layer or a nickel layer; The area of the upper surface of the copper layer (300) should be smaller than the ratio of the limit tensile force of the test equipment to the estimated interface tensile strength. The solder (500) adopts a solder sheet with an area smaller than that of the copper layer (300).

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