JP2006270031A - Semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a bad influence due to change in quality from being caused even when a top surface layer of a protective film changes in quality during manufacturing of a semiconductor device in which the protective film made of polyimide, etc. is formed on a silicon substrate. <P>SOLUTION: When an opening 6 is formed in the protective film 5 made of polyimide, etc., residue comprising polyimide, etc. may be left on the top surface of a connection pad 2 exposed through the opening 6 of the protective film 5. Consequently, the residue is removed by oxygen plasma ashing in the next place. In this case, a quality-changed layer A having an uneven structure is formed on the top surface side of the protective film 5. Then a natural oxide film formed on the top surface of the connection pad 2 exposed through openings 4 and 6 is removed by argon plasma etching. In this case, the quality-changed layer A further changes in quality to form a quality-changed layer C having a mesh structure. Then a first base metal layer 7 comprising titanium, etc. is formed. In this case, since the first base metal layer 7 is formed on the top surface of the quality-changed layer C having the mesh structure, adhesion force at the interface is high. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof.

  In a conventional semiconductor device, a plurality of connection pads made of aluminum or the like on a semiconductor substrate, an insulating film made of silicon oxide or the like, a protective film made of polyimide, and an opening in which the connection pads are provided in the insulating film and the protective film The first base metal layer made of titanium-tungsten alloy, the second base metal layer made of gold, and gold are exposed on the upper surface of the exposed connection pad and the protective film in the vicinity thereof. Some bump electrodes are provided (for example, see Patent Document 1).

Japanese Patent No. 2698827

  In the conventional method for manufacturing a semiconductor device, the natural oxide film formed on the upper surface of the connection pad made of aluminum or the like is removed by argon ion etching before forming the first base metal layer. In this case, the upper surface layer of the protective film made of polyimide may be affected by the influence of argon ions, the insulation resistance of the protective film may be lowered, and eventually a leak failure may occur. Therefore, after forming the first and second base metal layers and the bump electrodes, at least the altered layer of the protective film is removed by oxygen plasma etching.

  By the way, when an opening is formed in the protective film made of polyimide, a polyimide residue called scum may remain on the upper surface of the connection pad exposed through the opening of the protective film. Therefore, this residue may be removed by oxygen plasma etching. In this case, the upper surface layer of the protective film made of polyimide is altered by the influence of oxygen plasma, and an altered layer (hereinafter, this altered layer is referred to as altered layer A) is formed.

  Then, when argon ion etching is performed to remove the natural oxide film formed on the upper surface of the connection pad exposed through the openings of the insulating film and the protective film, if this etching is an ion gun method, The altered layer A on the protective film is further altered to form another altered layer (hereinafter, this altered layer is referred to as altered layer B). However, as will be described later, the deteriorated layer B has a problem that adhesion with the first base metal layer made of titanium or the like is low, and peeling easily occurs at the interface.

  In view of the above, an object of the present invention is to provide a semiconductor device capable of improving the adhesion of an altered layer formed on the upper surface side of a protective film to a base metal layer and a method for manufacturing the same.

  In order to achieve the above object, the present invention provides a semiconductor substrate having a plurality of connection pads on the upper surface, and a protective film provided on the semiconductor substrate and made of a resin having openings at portions corresponding to the connection pads. An alteration layer having a network structure patterned on the upper surface side of the protective film, an upper surface of the connection pad exposed through the opening of the protective film, and a base metal layer provided on the upper surface of the alteration layer It is characterized by having.

  According to the present invention, when an altered layer having a network structure different from the altered layer B is formed on the upper surface side of the protective film, the adhesion of the altered layer having the network structure to the underlying metal layer can be improved.

  FIG. 1 is a sectional view of a semiconductor device as an embodiment of the present invention. This semiconductor device is generally called a CSP (chip size package) and includes a silicon substrate (semiconductor substrate) 1. An integrated circuit (not shown) having a predetermined function is provided on the upper surface of the silicon substrate 1, and a plurality of connection pads 2 made of aluminum-based metal such as aluminum or aluminum alloy are connected to the integrated circuit around the upper surface. Is provided.

  An insulating film 3 made of silicon oxide, silicon nitride, Teos, or the like is provided on the upper surface of the silicon substrate 1 excluding the central portion of the connection pad 2, and the opening 4 provided in the insulating film 3 is provided in the central portion of the connection pad 2. Is exposed through. A protective film 5 made of polyimide, polybenzooxide (PBO) or the like is provided on the upper surface of the insulating film 3. In this case, an altered layer (hereinafter, this altered layer is referred to as an altered layer C) is patterned on the upper surface side of the protective film 5 below the first base metal layer 7 to be described later. . The protective film 5 including the altered layer C in a portion corresponding to the opening 4 of the insulating film 3 is provided with an opening 6 that is slightly larger than the opening 4 of the insulating film 3.

  A first base metal layer 7 made of titanium, chromium, or the like is provided in the openings 4 and 6 of the protective film 5 including the insulating film 3 and the altered layer C and on the entire upper surface of the altered layer C. A second base metal layer 8 made of copper is provided on the entire top surface of the first base metal layer 7. A wiring 9 made of copper is provided on the entire upper surface of the second base metal layer 8. One end of the wiring 9 including the first and second base metal layers 7 and 8 is connected to the connection pad 2 via the openings 4 and 6 of the protective film 5 including the insulating film 3 and the altered layer C. .

  A columnar electrode 10 made of copper is provided on the upper surface of the connection pad portion of the wiring 9. A sealing film 11 made of an epoxy resin, a phenol resin, or the like is provided on the upper surface of the protective film 5 including the wiring 9 so that the upper surface is flush with the upper surface of the columnar electrode 10. A solder ball 12 is provided on the upper surface of the columnar electrode 10.

  Next, an example of a method for manufacturing this semiconductor device will be described. First, as shown in FIG. 2, a plurality of connection pads 2 made of an aluminum-based metal and an insulating film 3 made of silicon oxide or the like are provided on silicon 1 (semiconductor substrate) in a wafer state. What is exposed through the opening 4 formed in the insulating film 3 is prepared. In this case, on the silicon substrate 1 in the wafer state, an integrated circuit (not shown) having a predetermined function is formed in a region where each semiconductor device is formed, and the connection pads 2 are formed in the corresponding regions. It is electrically connected to the integrated circuit.

  Next, as shown in FIG. 3, the entire upper surface of the insulating film 3 including the upper surface of the connection pad 2 exposed through the opening 4 of the insulating film 3 is coated with polyimide or the like by screen printing or spin coating. A protective film 5 made of PBO or the like is formed. Next, an opening 6 that is slightly larger than the opening 4 of the insulating film 3 is formed in the protective film 5 at a portion corresponding to the opening 3 of the insulating film 3 by photolithography.

  Here, when the opening 6 is formed in the protective film 5 made of resin such as polyimide or PBO, polyimide or PBO called scum is formed on the upper surface of the connection pad 2 exposed through the opening 6 of the protective film 5. Residues (not shown) made of resin may remain. Therefore, next, this residue is removed by oxygen plasma ashing. In this case, as shown in FIG. 4, the upper surface layer of the protective film 5 is altered by the influence of oxygen plasma, and the altered layer A is formed.

  Next, a natural oxide film (not shown) formed on the upper surface of the connection pad 2 made of an aluminum-based metal exposed through the openings 4 and 6 of the protective film 5 including the insulating film 3 and the altered layer A is formed. Removal is performed by plasma etching using an inert gas such as argon gas. By such plasma etching, the altered layer A is further altered, and the altered layer C is formed. As a plasma etching method using an inert gas, reactive ion etching (RIE) excited by one frequency or two frequencies, reactive high-density plasma excited by helicon wave, two-frequency excited inductively coupled plasma (ICP, Inductively coupled plasma), ISM (inductively super magneron), and the like, and plasma etching using ICP or ISM excited by two frequencies is particularly preferable.

  Here, referring to FIG. 12A, which is an SEM (scanning electron microscope) photograph of the upper surface of the protective film 5 shown in FIG. 3, the upper surface is almost flat, and the altered layer is not formed. Next, when FIG. 12B, which is an SEM photograph of the upper surface of the altered layer A, is seen, the upper surface has an uneven structure with a thickness of 10 to 100 nm, and the altered layer A is formed. Next, referring to FIG. 12C, which is an SEM photograph of the upper surface of the altered layer C, a network structure having a rougher surface roughness than the altered layer A is formed, and the altered layer C is formed.

  In this case, the modified layer C has a mesh diameter of 10 to 500 nm, a mesh thickness of 10 to 200 nm, and a layer thickness of 10 to 1000 nm. Further, since the constituent elements of polyimide or PBO, which is the material of the protective film 5, are carbon, oxygen, nitrogen, and hydrogen, the constituent elements of the altered layer C are carbon, oxygen, nitrogen, hydrogen, and an inert gas. In this case, the inert gas contained in the altered layer C is argon gas in the plasma etching process using argon gas as the inert gas. The constituent elements of the altered layer A are the same as those of the protective film 5 and are carbon, oxygen, nitrogen, and hydrogen.

  By the way, in order to remove the natural oxide film on the upper surface of the connection pad 2, instead of plasma etching using argon gas, when argon ion etching is performed by an ion gun method, the alteration is caused on the upper surface side of the protective film 5. Not the layer C but the altered layer B is formed. 12 (D) which is an SEM photograph of the upper surface of the altered layer B, the unevenness seen in the altered layer A shown in FIG. 12 (B) is reduced, and the protective film shown in FIG. 12 (A). 5 is close to the upper surface.

  Next, as shown in FIG. 5, the entire upper surface of the altered layer C including the upper surface of the connection pad 2 exposed through the openings 4 and 6 of the protective film 5 including the insulating film 3 and the altered layer C is sputtered. The first base metal layer 7 made of titanium or chromium and the second base metal layer 8 made of copper are successively formed by a method or the like. In this case, since the first base metal layer 7 is formed on the upper surface of the altered layer C, the adhesion at the interface is high as will be described later. The base metal layer may be a single layer as long as it has an adhesion function and a barrier function.

  Next, a plating resist film 21 is pattern-formed on the upper surface of the second base metal layer 8. In this case, an opening 22 is formed in the plating resist film 21 in a portion corresponding to the wiring 9 formation region. Next, by performing copper electroplating using the first and second base metal layers 7 and 8 as plating current paths, wiring is formed on the upper surface of the second base metal layer 8 in the opening 22 of the plating resist film 21. 9 is formed. Next, the plating resist film 21 is peeled off. Note that it is also possible to form a wiring composed of only the base metal layer by forming the base metal layer thick.

  Next, as shown in FIG. 6, a plating resist film 23 is patterned on the upper surface of the second base metal layer 8 including the wiring 9. In this case, an opening 24 is formed in the plating resist film 23 in a portion corresponding to the columnar electrode 10 formation region. Next, by performing copper electroplating using the first and second base metal layers 7 and 8 as plating current paths, the columnar electrode 10 is formed on the upper surface of the connection pad portion of the wiring 9 in the opening 24 of the plating resist film 23. Form.

  Next, the plating resist film 23 is peeled off, and then unnecessary portions of the first and second base metal layers 7 and 8 are removed by etching using the wiring 9 as a mask. As shown in FIG. The first and second base metal layers 7 and 8 remain only below.

  In this state, the altered layer C is also formed on the upper surface of the protective film 5 in a region other than the region under the first base metal layer 7. Since the deteriorated layer C has conductivity, a short circuit occurs between the wirings 9 as it is. Therefore, next, when the altered layer C in the region other than under the first base metal layer 7 is removed by oxygen plasma ashing, the altered layer C remains only under the first base metal layer 7 as shown in FIG. Is done.

  As oxygen plasma ashing in this case, an ICP (Inductively Coupled Plasma) type plasma ashing apparatus is used. The oxygen amount is 200 to 500 sccm, the plasma power is 500 to 1000 W, the pressure is 20 to 133 Pa, and the stage temperature is 40 for one wafer. It was carried out under conditions of ˜80 ° C. and treatment time of 10 to 60 seconds.

  Then, overashing occurs, and a part of the upper surface side of the protective film in a region other than the region under the first base metal layer 7 is also removed, and the altered layer C in a region other than the region under the first base metal layer 7 is completely removed. It was. In this case, the upper surface layer of the protective film 5 in a region other than the region under the first base metal layer 7 is altered by the influence of oxygen plasma to form the altered layer A, but there is no problem.

  Next, as shown in FIG. 9, the sealing film 11 made of epoxy resin or the like is formed on the entire upper surface of the protective film 5 including the columnar electrodes 10 and the wirings 9 by screen printing or spin coating. Is formed to be thicker than the height of the columnar electrode 10. Therefore, in this state, the upper surface of the columnar electrode 10 is covered with the sealing film 11.

  Next, the upper surface side of the sealing film 11 and the columnar electrode 10 is appropriately polished, and the upper surface of the columnar electrode 10 is exposed as shown in FIG. 10, and the sealing including the exposed upper surface of the columnar electrode 10 is performed. The upper surface of the stop film 11 is flattened. Next, as shown in FIG. 11, solder balls 11 are formed on the upper surface of the columnar electrode 10. Next, through a dicing process, a plurality of semiconductor devices shown in FIG. 1 are obtained.

  In the semiconductor device thus obtained, the modified layer C having a network structure is formed instead of the modified layer B on the upper surface side of the protective film 5 made of polyimide, PBO or the like. The adhesion of C to the first base metal layer 7 made of titanium, chromium, or the like can be improved as described below.

  Next, the shear strength test by the pressure cooker test (PCT) of the semiconductor device manufactured by the above manufacturing method will be described. In this case, the product of the present invention shown in FIG. 13 was prepared. In the product of the present invention, a protective film 5 made of polyimide is formed on the upper surface of the silicon substrate 1, an altered layer C is formed on the upper surface of the protective film 5, and a first layer made of planar circular titanium is formed on the upper surface of the altered layer C. The base metal layer 7, the second base metal layer 8 made of copper, and the columnar electrode 10 made of copper are formed. For comparison, a comparative product having the same structure as the product of the present invention shown in FIG. 13 but having an altered layer B formed on the upper surface of the protective film 5 was prepared.

  Then, for the product of the present invention and the comparative product, with the silicon substrate 1 fixed, a shear measurement jig (not shown) is pressed against the side surface of the columnar electrode 10 so that the first base metal layer 7 becomes the altered layer C ( The strength (g) when peeled from B) was determined. In this case, both the present invention product and the comparative product have a shear strength of 1 before the environmental test, and determine the shear strength after standing for 500 hours in PCT saturation (temperature 121 ° C., humidity 100% Rh, 2 atm). It was.

  Then, in the case of the comparative product, when the shear strength before the environmental test was set to 1, the shear strength after leaving for 500 hours in the saturation of the PCT decreased to 0.1. On the other hand, in the case of the product of the present invention, when the shear strength before the environmental test was set to 1, the shear strength after leaving for 500 hours at the saturation of PCT decreased to 0.68. It was 6.8 times, and it can be said that the interfacial adhesion was improved.

  The present invention is not limited to a semiconductor device called a CSP. For example, as in the above-described conventional example, a plurality of connection pads, insulating films, and protective films are provided on a semiconductor substrate, and the connection pads are formed as insulating films and protective films. The present invention is also applicable to the case where the first and second base metal layers and the bump electrode are provided on the upper surface of the exposed connection pad and the protective film in the vicinity thereof exposed through the provided opening. Can do.

1 is a cross-sectional view of a semiconductor device as an embodiment of the present invention. Sectional drawing of what was prepared initially in an example of the manufacturing method of the semiconductor device shown in FIG. Sectional drawing of the process following FIG. Sectional drawing of the process following FIG. Sectional drawing of the process following FIG. Sectional drawing of the process following FIG. Sectional drawing of the process following FIG. Sectional drawing of the process following FIG. FIG. 9 is a cross-sectional view of the process following FIG. 8. Sectional drawing of the process following FIG. Sectional drawing of the process following FIG. (A)-(D) is a figure which shows the SEM photograph of each upper surface of a protective film, the altered layer A, the altered layer C, and the altered layer B, respectively. The perspective view of this invention product used for the shear strength test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Connection pad 3 Insulating film 4 Opening part 5 Protective film 6 Opening part 7 1st base metal layer 8 2nd base metal layer 9 Wiring 10 Columnar electrode 11 Sealing film 12 Solder ball A Alteration layer A
B Altered layer B
C Altered layer C

Claims (13)

  A semiconductor substrate having a plurality of connection pads on the upper surface, a protective film formed on the semiconductor substrate and having an opening in a portion corresponding to the connection pads, and pattern formation on the upper surface side of the protective film And a metal layer provided on the upper surface of the connection pad exposed through the opening of the protective film and on the upper surface of the deteriorated layer. .   2. The semiconductor device according to claim 1, wherein the protective film is made of a resin containing carbon, oxygen, nitrogen, and hydrogen.   3. The semiconductor device according to claim 2, wherein the altered layer includes carbon, oxygen, nitrogen, hydrogen, and argon.   2. The semiconductor device according to claim 1, wherein the network structure of the altered layer has a mesh diameter of 10 to 500 nm, a mesh thickness of 10 to 200 nm, and a layer thickness of 10 to 1000 nm.   2. The semiconductor device according to claim 1, wherein wiring is provided on the metal layer.   6. The semiconductor device according to claim 5, wherein a columnar electrode is provided on a connection pad portion of the wiring.   7. The semiconductor device according to claim 6, wherein a sealing film is provided around the columnar electrode, and a solder ball is provided on the columnar electrode. Forming a protective film made of a resin having an opening in a portion corresponding to the connection pad on a semiconductor substrate having a plurality of connection pads on the upper surface;
Deterioration in which the residue of the protective film remaining on the upper surface of the connection pad exposed through the opening of the protective film is removed by oxygen plasma ashing, and the upper surface layer of the protective film is altered by the oxygen plasma ashing The step of forming layer A;
The oxide film formed on the upper surface of the connection pad exposed through the opening of the protective film is removed by plasma etching using an inert gas, and the altered layer A is altered by the plasma etching. A step of forming a modified layer C having a rougher surface roughness than the modified layer;
Patterning a metal layer on the upper surface of the connection pad and the upper surface of the altered layer C exposed through the opening of the protective film;
Removing the altered layer C in a region other than under the metal layer by oxygen plasma ashing;
A method for manufacturing a semiconductor device, comprising:   9. The method of manufacturing a semiconductor device according to claim 8, wherein the step of removing the deteriorated layer C includes a part on the upper surface side of the protective film in a region other than under the metal layer. .   9. The method of manufacturing a semiconductor device according to claim 8, wherein the altered layer C has a network structure.   11. The semiconductor device according to claim 10, wherein the network structure of the altered layer has a mesh diameter of 10 to 500 nm, a mesh thickness of 10 to 200 nm, and a layer thickness of 10 to 1000 nm. Production method.   9. The method of manufacturing a semiconductor device according to claim 8, wherein the protective film is formed of a resin containing carbon, oxygen, nitrogen, and hydrogen.   13. The method of manufacturing a semiconductor device according to claim 12, wherein the inert gas is an argon gas, and the altered layer C includes carbon, oxygen, nitrogen, hydrogen, and argon.

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