JP2009099617A - Method of manufacturing semiconductor apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable semiconductor apparatus. <P>SOLUTION: The method of manufacturing a semiconductor apparatus includes the steps of: forming a semiconductor chip 11 having a bonding pad 15 in which an aluminum film 12, a nickel alloy film 13, and a metal film 14 are laminated on a first surface 11a; placing the semiconductor chip 14 on a substrate 16 while setting a second surface 11b opposite the first surface 11a at a substrate 16 side; removing the surface layer of the metal film 14 by making a pin 32 abut on the bonding pad 15 inclinedly to raise the substrate 16 relative to the pin 32, thereby sliding the leading end of the pin 32 in a horizontal direction, and; bonding a connection conductor 18 to the metal film 14 from which the surface layer is removed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device.

  In recent years, with the high integration of semiconductor devices typified by large scale integrated circuits (LSIs), the number of input / output pins of the semiconductor devices has been increased and the pitch has been reduced.

  Conventionally, aluminum (Al) has been used for bonding pads of semiconductor devices. Since the area of the bonding pad is reduced by narrowing the pitch of the input / output pins, gold (Au) that provides higher bonding strength than aluminum (Al) in order to maintain the bonding strength of the wire bonded to the bonding pad. Has come to be used.

  However, in the bonding pad in which the gold film is formed on the base metal film, the base metal piles up on the surface of the gold film due to the thermal history in the manufacturing process of the semiconductor device, and the base metal is not formed on the surface of the gold film. Since a film of oxide, hydroxide, or the like is formed, there is a problem that the original bonding strength of gold cannot be obtained.

  When removing the coating formed on the surface of the gold film by, for example, a sputtering method using argon (Ar) plasma, the sputtering method has no selectivity. There are problems that affect the reliability of the device.

  There is a problem that carbon (C) scattered from the organic protective film around the bonding pad adheres to the bonding pad, contaminates the bonding pad, and the expected bonding strength cannot be obtained.

  Since the film formed on the surface of the gold film has a variation in film thickness, there is a problem that much labor is required to optimize the sputtering conditions (plasma output, sputtering time, etc.) by Ar plasma.

  On the other hand, in the inspection of the electrical characteristics of the semiconductor device, the tester probe pin is brought into contact with and pressed against the test aluminum pad formed on the semiconductor chip, and the oxide film on the surface of the test pad is removed to expose the inner aluminum. By doing so, a method for ensuring electrical contact between the test pad and the probe pin of the tester is known (see, for example, Patent Document 1).

In Patent Document 1, it is only necessary to ensure electrical contact between the test pad and the probe pin of the tester, so that only the oxide on the pad surface is removed and the pad itself is not damaged as much as possible.
However, there is no disclosure of bonding pads that require bonding strength.
JP-A-10-221370

  An object of this invention is to provide the manufacturing method of a highly reliable semiconductor device.

  According to another aspect of the present invention, there is provided a method for manufacturing a semiconductor device, including: a step of forming a semiconductor chip having a bonding pad in which an aluminum film, a nickel-based alloy film, and a gold film are stacked on a first surface; A step of placing the semiconductor chip on the substrate with the second surface opposite to the surface of the substrate facing the substrate; slopingly contacting a pin to the bonding pad; and relative to the pin And removing the surface layer of the gold film by sliding the tip of the pin in the horizontal direction, and joining the connection conductor to the gold film from which the surface layer has been removed. It is said.

  According to the present invention, a highly reliable semiconductor device can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

  A method for manufacturing a semiconductor device according to an embodiment of the present invention will be described with reference to FIGS. 1A and 1B are diagrams showing a semiconductor device, FIG. 1A is a sectional view thereof, FIG. 1B is an enlarged sectional view showing an essential part thereof, FIG. 2 is a flowchart showing a manufacturing process of the semiconductor device, and FIG. It is sectional drawing which shows the principal part of the manufacturing process of a semiconductor device in order.

  As shown in FIG. 1, the semiconductor device 10 includes a semiconductor chip 11 having a bonding pad 15 in which an aluminum film 12, a nickel-based alloy film 13, and a gold film 14 are stacked on a first surface 11a, The substrate 16 is placed on the substrate 16 so as to face the second surface 11 b opposite to the surface 11 a of the semiconductor substrate 11, the substrate 16 on which the semiconductor chip 11 is placed, the bonding pad 15 of the semiconductor chip 11, and the bonding pad 15 and the semiconductor chip 11. A wire 18 (connection conductor) for connecting the formed bonding pad 17 is provided.

  The bonding pad 15 is surrounded by an insulating film 20 such as a silicon oxide film and a silicon nitride film, and a protective film 21 such as polyimide is formed on the insulating film 20. Thereby, the bonding pad 15 is protected.

  The bonding pad 17 of the substrate 16 is connected to a solder ball 19 formed on the bottom surface of the substrate 16 through a via (not shown) penetrating the substrate 16.

  The bonding pads 15 of the semiconductor chip 11 and the bonding pads 17 of the substrate 16 are arranged at a narrow pitch of 40 μm, for example.

  On the semiconductor chip 11, another plurality of semiconductor chips are stacked. The bonding pads 15 of the plurality of stacked semiconductor chips are connected to the bonding pads 17 of the substrate 16 through wires 18 respectively.

  The bottom surface of the substrate 16 is exposed, and the substrate 16, the semiconductor chip 11, and the wires 18 are collectively molded with the resin 22.

  For example, the bonding pad 17 of the substrate 16 is formed by laminating an aluminum film 12, a nickel-based alloy film 13, and a gold film 14 in the same manner as the bonding pad 15 of the semiconductor chip 11.

  The wire 18 is, for example, a gold wire, one end of which is an exposed surface after the surface layer of the gold film 12 of the bonding pad 15 of the semiconductor chip 11 is removed, for example, 4 to 10 nm, and the concentration of nickel is the abundance ratio of nickel to gold. The other end is bonded to the surface of the gold film 12 of the bonding pad 17 of the substrate 16.

Next, a method for manufacturing the semiconductor device 10 will be described. FIG. 2 is a flowchart showing the manufacturing process of the semiconductor device, and FIG. 3 is a cross-sectional view showing the main part of the manufacturing process of the semiconductor device.
As shown in FIG. 2, an electronic circuit, for example, an integrated circuit is formed on a semiconductor substrate by a well-known method, aluminum is vacuum-deposited, and a pattern having a pattern is formed by photolithography to form a pad having an aluminum film 12 around the integrated circuit. To do.

Next, a resist film having an opening corresponding to the pad having the aluminum film 12 is formed on the semiconductor substrate by photolithography.
Next, a nickel film containing, for example, about 1% of phosphorus (P) is formed as a nickel alloy film 13 on the aluminum film 12 by electroless plating using the resist film as a mask, and then on the nickel alloy film 13. Then, a gold film 14 is formed, and a bonding pad 15 in which an aluminum film 12, a nickel alloy film 13, and a gold film 14 are laminated is formed.

FIG. 3A is a cross-sectional view showing the bonding pad 15 after being formed.
As shown in FIG. 3, the gold film 14 formed by the electroless plating method has a low density and a large number of grain boundaries 30 exist.

Next, a TEOS (Tetra Ethyl Ortho Silicate) film is formed as an insulating film 20 on the semiconductor substrate so as to surround the bonding pad 15 by, for example, a CVD (Chemical Vapor Deposition) method, and a silicon nitride film is formed by a plasma CVD method. .
At this time, since the semiconductor substrate is heated to about 200 to 400 ° C., the first thermal history is applied to the bonding pad 15.

  Next, after applying polyimide as a protective film 21 on the entire surface of the semiconductor substrate including the insulating film 20, the back surface of the semiconductor substrate was ground to a predetermined thickness, and a resin film was attached to the back surface of the semiconductor substrate. Thereafter, the semiconductor substrate 11 is obtained by dicing the semiconductor substrate using a blade.

Next, the semiconductor chip 11 is mounted on the substrate 16 via a resin film, and the semiconductor chip 11 is mounted on the substrate 16 by curing the resin film.
At this time, since the semiconductor substrate is heated to about 100 to 150 ° C., a second thermal history is applied to the bonding pad 15.

FIG. 3B is a sectional view showing the bonding pad 15 after the first and second thermal histories are applied. However, the insulating film 20 is omitted.
As shown in FIG. 3 (b), when the first thermal history is applied, nickel scoops up the grain boundary 30 from the nickel alloy film 13 underlying the gold film 14, and on the surface of the gold film 14. By pile-up, a nickel coating 31 is formed on the surface of the gold film 14.

  When the nickel coating 31 is exposed to the atmosphere while the first and second thermal histories are being applied, the nickel reacts with moisture in the atmosphere to form nickel oxides and hydroxides. Hereinafter, the nickel coating 31 containing nickel oxide and hydroxide is simply referred to as a nickel coating 31.

  Next, the nickel concentration on the surface of the gold film 14 is obtained. The nickel concentration is measured by, for example, AES (Auger Electron Spectroscopy). In AES, the depth direction distribution can be obtained by sputtering the surface and repeating the concentration measurement.

  FIG. 4 is a diagram showing an example of the depth direction distribution of nickel in the gold film 14. The broken line 40 shows the depth direction distribution of nickel when a thermal history (150 ° C. × 500 h) is added, and the solid line 41 is It is a figure which shows the depth direction distribution of nickel when not adding a heat history.

As shown in FIG. 4, when no thermal history is applied, the nickel concentration (the abundance ratio of nickel to gold) is 0.03 or less.
On the other hand, when the thermal history was applied, the nickel concentration was about 0.2 on the surface and gradually decreased in the depth direction, and showed a substantially constant value of about 0.03 at a depth of about 20 nm.
From this, it is recognized that nickel piles up on the surface of the gold film 14 to form a nickel coating 31.

  As described above, according to the thermal history of the bonding pad 15, the depth direction distribution data of nickel in the gold film 14 is obtained in advance and accumulated.

  Next, since the gold film 14 on which the nickel coating 31 is formed cannot obtain a sufficient bonding strength, the removal amount of the surface layer of the gold film 14 is obtained so that a sufficient bonding strength can be obtained.

  FIG. 5 is a diagram showing the relationship between the nickel concentration on the surface of the gold film 14 and the bonding strength. The bonding strength was measured by bonding a gold wire 18 to the bonding pad 15, applying a static load to the wire 18 with a tensile tester, and determining the shear strength from the load at the time of fracture.

As shown in FIG. 5, it can be seen that the shear strength decreases to 280 mN to 120 mN as the nickel concentration increases from 0 to 0.4.
The fracture mode depends on the nickel concentration. It can be seen that when the nickel concentration is about 0 to 0.17, the fracture mode is a mode in which the ball of the wire 18 breaks, and the bonding strength between the gold film 14 and the ball of the wire 18 is sufficiently maintained.

  On the other hand, when the nickel concentration is about 0.28 or more, the fracture mode is a mode in which the fracture occurs at the bonding interface between the gold film 14 and the ball of the wire 18 and the bonding strength between the gold film 14 and the ball of the wire 18 is insufficient. I understand that

  When the nickel concentration is about 0.21 to 0.26, the fracture mode includes a mode in which the fracture occurs in the ball and a mode in which the fracture occurs at the interface, and the bonding strength between the gold film 14 and the ball of the wire 18 varies. I understand that.

  Thus, in order to obtain a sufficient bonding strength between the gold film 14 and the ball of the wire 18 with a margin, for example, a safety factor doubled, it is necessary to suppress the nickel concentration to 0.1 or less.

In order to obtain sufficient bonding strength from the depth direction distribution of the nickel element concentration shown in FIG. 4, it is desirable to scrape the surface layer of the gold film 14 by 4 nm or more.
However, if the surface layer of the gold film 14 is scraped excessively, the effect is not changed, and considering the variation in the cutting amount, it is desirable that the thickness be 10 nm or less.

  Therefore, the removal amount of the gold film 14 is obtained from the nickel concentration on the surface of the gold film 14 so that the nickel concentration is equal to or less than a predetermined value (0.1), based on the nickel depth distribution obtained in advance.

  Next, the substrate 16 on which the semiconductor chip 11 is mounted is placed on the stage, the pins are obliquely brought into contact with the bonding pads 15 having the nickel coating 31 formed on the surface, and the substrate 16 is relative to the pins. The surface of the gold film 14 is removed by sliding the tip of the pin horizontally.

  FIG. 6 is a diagram showing the relationship between the amount of rise of the substrate 16 and the amount of removal of the gold film 14. The removal amount of the gold film 14 was determined from the step between the removed portion and the non-removed portion by measuring the surface state by AFM (Atomic Force Microscopy).

As shown in FIG. 6, it has been found that a stable removal amount can be obtained when the rising amount of the substrate 16 is about 10 μm to 80 μm.
This is because if the rising amount is too small as 10 μm or less, the contact between the pin and the bonding pad 15 becomes unstable due to the initial position of the pin and the variation in the shape of the pin, and if it is too large as 80 μm or more, the pressing force becomes excessive. This is because it becomes difficult to scrape the metal film 14 smoothly. Here, the upper limit of the amount of increase is not fixed, but changes depending on the elasticity of the pins used.
In this way, correlation data between the rising amount of the substrate 16 and the removal amount of the gold film 14 is obtained in advance and accumulated.

FIG. 3C is a cross-sectional view showing the bonding pad 15 after the surface layer of the gold film 14 is removed. However, the insulating film 20 is omitted.
As shown in FIG. 3C, the pin 32 is brought into contact with the gold film 14 obliquely from above, for example, the stage is raised about 10 μm to 80 μm, and the tip 32a of the pin 32 is slid in the X direction (horizontal direction). The surface layer of the gold film 14 is cut off smoothly by 4 nm to 10 nm, and the nickel coating 31 is removed.

  As a result of various studies, when the surface roughness Ra of the tip 32a is 0.04 μm or less, the surface layer of the gold film 14 can be scraped off by about 4 nm to 10 nm with good reproducibility, and the surface 33 and the surface layer of the gold film 14 are removed. A step H of 4 nm to 10 nm is formed between the surface 34 of the gold film 14. Thereby, it is possible to expose the clean gold film 14 without the nickel coating 31.

  In consideration of the dimensional accuracy of the pin 32 and variations in the angle of entry of the pin 32, the ratio (R / D) of the radius of curvature R to the diameter D of the tip 32a of the pin 32 is preferably 6 or less.

FIG. 7 is a view showing the surface state of the cutting region of the gold film 14 of the bonding pad 15. The surface state was measured by AFM (Atomic Force Microscopy).
As shown in FIG. 7, it can be seen that the cutting region of the gold film 14 is flatter than the region where the nickel coating 31 is formed.

Next, wires 18 are bonded to the bonding pads 15 of the semiconductor chip 11 and the bonding pads 17 of the substrate 16.
FIG. 8 is a diagram showing the relationship between the cutting region of the gold film 14 of the bonding pad 15 and the connection region of the wire 18.
As shown in FIG. 8, the size of the cutting region 50 of the gold film 14 is such that the region 52 where the cutting region 50 and the ball 51 formed at the connecting portion of the wire 18 overlap when the wire 18 is bonded to the bonding pad 15. However, it is desirable that the contact area of the balls 51 be ½ or more.

  Next, the bottom surface of the substrate 16 is exposed, and the substrate 16, the semiconductor chip 11, and the wire 18 are integrally molded with the resin 22, whereby the semiconductor device shown in FIG. 1 is obtained.

  As described above, the method of manufacturing the semiconductor device according to the present embodiment is such that the pin is brought into contact with and pressed against the bonding pad 15 in which the aluminum film 12, the nickel-based alloy film 13, and the gold film 14 are laminated. The surface layer of the film 14 is scraped off to remove the nickel coating 31 formed on the surface of the gold film 14.

  As a result, the bonding pad 15 and the wire 18 where the clean gold film 14 without the nickel coating 31 is exposed can be bonded, so that an ideal bonding state with sufficiently high reliability can be obtained and the bonding strength can be increased. improves. Therefore, a highly reliable semiconductor device can be obtained.

  Here, the steps for determining the nickel surface concentration, the amount of removed gold film, and the amount of increase in the substrate do not have to be performed for each production lot, and it is sufficient if they are performed appropriately according to compensation for changes over time, changes in production conditions, etc. is there.

  Although the case where the wire 18 is a gold wire has been described, an aluminum wire or a copper wire may be used.

  Although the case where the nickel-based alloy film is nickel containing phosphorus (P) has been described, nickel (Ni) alone, nickel containing boron (B), nickel containing boron (B) and tungsten (W) It does not matter.

  Further, instead of nickel, cobalt (Co) alone, cobalt containing phosphorus (P), cobalt containing boron (B), cobalt containing phosphorus (P) and tungsten (W), boron (B) and Cobalt containing tungsten (W) may be used.

1A and 1B are diagrams illustrating a semiconductor device according to an embodiment of the present invention, in which FIG. 1A is a cross-sectional view thereof, and FIG. 6 is a flowchart showing a manufacturing process of a semiconductor device according to an embodiment of the present invention. Sectional drawing which shows the principal part of the manufacturing process of the semiconductor device which concerns on the Example of this invention in order. The figure which shows the depth direction distribution of the nickel of the bonding pad of the semiconductor device which concerns on the Example of this invention. The figure which shows the relationship between the nickel concentration of the semiconductor device which concerns on the Example of this invention, and bonding strength. The figure which shows the relationship between the raise amount of the board | substrate of the semiconductor device based on the Example of this invention, and the removal amount of a gold film. The figure which shows the cutting area | region of the bonding pad of the semiconductor device which concerns on the Example of this invention. The figure which shows the relationship between the cutting area | region of the bonding pad of the semiconductor device which concerns on the Example of this invention, and the connection area | region of a wire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor device 11 Semiconductor chip 12 Aluminum film 13 Nickel alloy film 14 Gold films 15 and 17 Bonding pad 16 Substrate 18 Wire (connection conductor)
19 Solder balls 20 Insulating film 21 Protective film 22 Resin 30 Grain boundary 31 Coating 32 Pin 50 Cutting area 51 Ball 52 Overlapping area

Claims (5)

Forming a semiconductor chip having a bonding pad in which an aluminum film, a nickel-based alloy film, and a gold film are laminated on a first surface;
Placing the semiconductor chip on the substrate with the second surface opposite to the first surface facing the substrate;
Removing the surface layer of the gold film by causing the pins to contact the bonding pads diagonally, raising the substrate relative to the pins, and sliding the tips of the pins in a horizontal direction;
Bonding the connection conductor to the gold film from which the surface layer has been removed;
A method for manufacturing a semiconductor device, comprising: Obtaining a nickel concentration on the surface of the gold film;
A step of determining the removal amount of the gold film based on a distribution in the depth direction of the nickel obtained in advance so that the nickel concentration on the surface of the gold film is a predetermined value or less;
A step of determining a rising amount of the substrate from which the gold film can be removed based on a relationship between the rising amount and the removal amount obtained in advance;
The method of manufacturing a semiconductor device according to claim 1, comprising:   3. The method of manufacturing a semiconductor device according to claim 2, wherein a predetermined value of the nickel concentration on the surface of the gold film is 0.1 or less in terms of an abundance ratio of the nickel to the gold.   The method for manufacturing a semiconductor device according to claim 1, wherein an amount of rise of the substrate is 10 μm or more.   2. The method of manufacturing a semiconductor device according to claim 1, wherein the removal amount of the gold film is in a range of 4 nm to 10 nm.

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