JP2017037924A - Semiconductor package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of joining defect between a bonding wire and a metal electrode, when performing reliability test at a higher temperature.SOLUTION: A semiconductor package includes: a semiconductor element having a die pad and a plurality of electrode pads placed on the die pad; a connections placed on the electrode pads; a plurality of external terminals placed around the die pads; a wiring for connecting the external terminals and the electrode pads electrically; and a sealing body for sealing at least the semiconductor element and the wiring entirely. The sealing body is a resin material, containing 100 ppm or less of sulfur and chlorine, when measured by whole volume analysis.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for improving the reliability of wiring in a semiconductor package.

  In a conventional semiconductor package, a bonding wire (wire connected by a wire bonding method) for bonding between a metal electrode on a semiconductor element and an external terminal is used, and at least the entire semiconductor element and the bonding wire are sealed with a sealing resin. (For example, Patent Document 1). Since the material of the bonding wire is also a metal, an alloy layer is formed at the joint between the bonding wire and the metal electrode.

  On the other hand, in recent years, development of semiconductor packages for in-vehicle use (particularly, control systems) has been accelerated. AEC-Q100, which is a certification standard for various reliability tests for in-vehicle integrated circuits (ICs), has been upgraded, and the demand for semiconductor packages has been increasing. In general-purpose IC reliability tests, heating at 125 ° C. is common, but in-vehicle ICs require reliability at higher temperatures of 150 to 175 ° C. As the reliability test, there are an HTS (High Temperature Storage) test that heats at a high temperature, a PCT (Pressure Cooker Test) that is a heat test in a high-temperature and high-humidity environment, and a HAST (Highly Integrated Temperature and Humidity Test).

JP 2009-59962 A

  When the reliability test as described above is performed in order to cope with the in-vehicle use, there is a problem that a defect that has not been revealed in the conventional reliability test occurs. For example, it has been found that there is a problem that a bonding failure between a bonding wire and a metal electrode occurs.

  The present invention has been made in view of the above circumstances, and an object thereof is to suppress the occurrence of bonding failure between a bonding wire and a metal electrode when a reliability test at a higher temperature is performed. By the way.

  According to the present embodiment, a semiconductor device having a plurality of electrode pads disposed on the die pad and the die pad, a connection portion disposed on the electrode pad, and a plurality of semiconductor devices disposed around the die pad. An external terminal; a wiring electrically connected to the external terminal and the electrode pad; and a sealing body that seals at least the semiconductor element and the entire wiring; and the sealing body is a resin material, Provided is a semiconductor package characterized in that the resin material contains less than 100 ppm of sulfur and chlorine, respectively, when measured by total analysis.

  The sealing body may contain 50 ppm or less of sulfur and chlorine, respectively, when measured by total analysis.

  A plurality of the semiconductor elements may be stacked.

  The wiring may be composed mainly of copper.

  The external terminal may be either a lead or a solder bump.

  According to one embodiment of the present invention, it is possible to suppress the occurrence of a bonding failure between a bonding wire and a metal electrode when performing a reliability test at a higher temperature.

It is a perspective view showing a schematic structure of a semiconductor package concerning one embodiment of the present invention. It is a top view of the semiconductor package of FIG. FIG. 3 is a cross-sectional view taken along line AB of the semiconductor package of FIG. 2. It is sectional drawing which shows the wire junction part vicinity of the conventional semiconductor package.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The following embodiments are examples of the embodiments of the present invention, and the present invention is not limited to these embodiments. Note that in the drawings referred to in this embodiment, the same portions or portions having similar functions are denoted by the same reference numerals, and repeated description thereof may be omitted. In addition, the dimensional ratio in the drawing may be different from the actual ratio for convenience of explanation, or a part of the configuration may be omitted from the drawing.

[Structure of semiconductor package]
A configuration of a semiconductor package according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a perspective view showing a schematic configuration of a semiconductor package according to an embodiment of the present invention. FIG. 2 is a top view of the semiconductor package of FIG. FIG. 3 is a cross-sectional view taken along line AB of the semiconductor package of FIG. The semiconductor package 10 includes an external terminal 101, a die pad 102, a semiconductor element 103, a semiconductor element protective film 111, a metal electrode 112, a bonding portion 113, a metal wire 104, and a sealing resin (mold resin) 105.

  In this example, the external terminal 101 is a lead frame, and the semiconductor package is a QFN (Quad Flat Non-Leaded Package), but is not limited to this, and is not limited to this, but a QFP (Quad Flat Package), SOP (Small). It may be a lead frame used in an Outline Package or a hemispherical solder used in a BGA (Ball Grid Array) package or the like.

  The die pad 102 fixedly supports the semiconductor element 103. The semiconductor element 103 has a plurality of metal electrodes 112 and is disposed on the die pad 102. The semiconductor element 103 is a semiconductor device such as an IC chip or an LSI chip. Although FIG. 1 shows an example in which one semiconductor element 103 is arranged on the die pad 102, a plurality of semiconductor elements 103 can actually be arranged on the die pad 102.

  The semiconductor element protective film (passivation film) 111 is for protecting the metal electrode 112 from being corroded by moisture. Examples of the semiconductor element protective film 111 include a silicon nitride film, but the semiconductor element protective film 111 is not limited thereto, and a known technique may be used.

  An alloy layer of the metal of the metal electrode 112 and the metal of the metal wire 104 is formed at the joint 113 between the metal electrode 112 and the metal wire 104. In order to maintain a good electrical connection between the metal electrode 112 and the metal wire 104, it is necessary that the alloy layer exists stably. Therefore, even in a high temperature state, the alloy at the joint does not change, so it is necessary to prevent impurities from acting on the joint.

  In order to prevent impurities from acting on the junction, it is conceivable to cover the junction with a passivation film. However, in the manufacturing process, after a passivation film is applied to the entire surface of the semiconductor wafer, a window is opened to connect the metal electrode 112 with the metal wire 104, and then the metal electrode 112 is bonded with the metal wire 104. Since an alloy layer is formed at the joint between the metal electrode 112 and the metal wire 104 during bonding, the joint is inevitably not covered with the passivation film. After that, since the joint portion is covered with the sealing resin 105, a portion that comes into contact with the sealing resin inevitably exists.

  The present invention reduces impurities that adversely affect the alloy layer, which are included in a member in contact with the joint. That is, the concentration of impurities that can react with the alloy layer contained in the sealing resin is reduced. Preferably, it is less than 100 ppm.

  The material of the metal electrode 112 is aluminum in this example. However, it is not limited to pure aluminum, and may be an aluminum alloy. Here, examples of the aluminum alloy include Al-1% Si, Al-0.5% Cu, and Al-1% Si-0.5% Cu, but are not limited thereto.

  A metal wire (bonding wire) 104 electrically connects the external terminal 101 and the metal electrode 112 of the semiconductor element 103. The material of the metal wire 104 may be gold (Au). For example, a high purity (purity> 99.99%) 4N gold wire is mainly used as the material of the metal wire 104. However, because the growth rate of the intermetallic compound at the gold / aluminum junction (Au / Al junction) is high, voids due to the Kirkendall phenomenon occur when HTS tests are performed at high temperatures. In view of stability at high temperatures, it is preferable to use alloy wires or copper (Cu) wires that slow the growth of voids. In the case of a copper wire, a trace amount of additive material may be included as long as copper is the main component. Examples of the trace amount of additive material include, but are not limited to, palladium (Pd), gold, silver (Ag), and the like.

When the metal wire 104 is a copper wire containing copper as a main component and the metal electrode is aluminum, the main layers of the intermetallic compound composed of Cu and Al are Cu ₉ Al ₄ layer and CuAl ₂ layer. It is known that there is. In this example, the joint 113 is an alloy layer such as a Cu ₉ Al ₄ layer and a CuAl ₂ layer. However, copper is less chemically stable than gold. Therefore, in the present invention, it is important that impurities that alter the CuAl alloy do not act at high temperatures.

  Specifically, it is preferable to prevent impurities from being contained in the sealing resin 105 in contact with the joint 113 as much as possible. Here, “not to be included as much as possible” means not to be intentionally included unless it is inevitably included in the manufacturing process.

The Cu ₉ Al ₄ layer is vulnerable to moisture and impurities. Therefore, it is desirable that the corresponding impurity is less than 100 ppm so that the impurity does not act from the sealing resin.

  The sealing resin 105 protects the upper portion of the die pad 102 and the semiconductor element 103 from entry of moisture and impurities from the outside. As the sealing resin 105, an epoxy resin, a cyanate ester resin, an acrylic resin, a polyimide resin, a silicon resin, or the like can be used.

  Incidentally, the sealing resin 105 contains impurities such as sulfur (S) and chlorine (Cl) in order to improve the adhesion between the sealing resin and a metal such as a lead frame in the semiconductor package. Of the added elements, sulfur and chlorine are particularly undesirable because they act on the CuAl alloy layer.

  Table 1 shows the number of defects in which the bonding portion 113 between the copper wire and the aluminum electrode was electrically opened when the HTS test was performed with the number of samples of 22 pcs in each evaluation resin (sample). As shown in Table 1, when using a resin (sample 2) containing 100 ppm or more of sulfur and 50 ppm or less of chlorine in the sealing resin, an HTS test was conducted at 175 ° C. for 1000 hours. 0 pcs. However, when an HTS test was performed at 175 ° C. for 2000 hours, the defect was 21 pcs.

  As a result of intensive investigations by the present inventors, it was found that microcracks due to dry corrosion occur in the alloy layer at the joint portion between the copper wire and the aluminum electrode of the semiconductor element when a high temperature storage test is performed. As described above, it has been confirmed that when left at 175 ° C. for 2000 hours, the joint portion is electrically open. After the present inventors have polished the cross section of the defective joint, the elements of the cross section using EDX (Energy Dispersive X-ray Spectroscopy) or EPMA (Electron Probe Micro Analyzer: Electron Microanalyzer) are used. As a result of analysis, sulfur and chlorine were confirmed.

  Here, it demonstrates that a microcrack arises in a junction part using FIG. FIG. 4 is a cross-sectional view showing the vicinity of a wire bonding portion of a conventional semiconductor package. A semiconductor element protective film 911 and an aluminum electrode 912 are disposed on the semiconductor element 903. In addition, a joint portion 913 is provided between the aluminum electrode 912 and the wire 904. The sealing resin 905 includes impurities such as chlorine 915 and sulfur 916. When the chlorine 915 and sulfur 916 collide with the joint portion 913, micro cracks are generated. Therefore, the greater the content of chlorine and sulfur in the sealing resin, the easier it is for microcracks to occur.

  On the other hand, when a resin (sample 1) containing 50 pppm or less of sulfur and chlorine was used as the sealing resin, an HTS test was conducted at 175 ° C. for 1000 hours. The defect was 0 pcs. Moreover, when the HTS test for 2000 hours was performed at 175 degreeC, the defect remained 0 pcs.

  As a result, it is preferable to reduce at least one or both of sulfur and chlorine among the elements contained in the sealing resin. The amount of impurities contained in the sealing resin 105 is preferably at least sulfur less than 100 ppm. More preferably, the amount of impurities contained in the sealing resin 105 is less than 100 ppm each of chlorine 115 and sulfur 116. More preferably, the amount of impurities contained in the sealing resin 105 is preferably at least 50 ppm or less of sulfur. More preferably, the amount of impurities contained in the sealing resin 105 is 50 ppm or less for each of chlorine 115 and sulfur 116.

When a higher temperature reliability test for in-vehicle use is performed on a semiconductor package using a copper wire, chlorine 115 and sulfur 116 may cause micro cracks in the Cu ₉ Al ₄ layer of the joint 113. Thereby, it is considered that the joint 113 between the copper wire and the aluminum electrode is electrically opened.

  According to the present invention, the contents of chlorine and sulfur conventionally required for improving the adhesion to the sealing resin are each reduced to less than 100 ppm, more preferably to 50 ppm or less, and the sealing property is maintained. However, it is possible to improve the reliability of copper wire bonding. That is, it is possible to suppress the occurrence of microcracks due to dry corrosion at the joint between the copper wire and the aluminum electrode of the semiconductor element when left at high temperature.

  In addition, according to the present invention, when a copper wire is used as the metal wire, it is possible to provide a cheaper semiconductor package than when an expensive gold (Au) is used.

In addition, when the content of chlorine and sulfur in the sealing resin is reduced, there is a concern about deterioration of adhesion. However, the deterioration of adhesion can be suppressed while reducing the additive elements by the O ₂ plasma treatment during the assembly process, the anchor effect due to surface roughening, and the like.

  The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present invention.

10: Semiconductor package 101: External terminal 102: Die pad 103, 903: Semiconductor element 104, 904: Wire
105, 905: Sealing resin 111, 911: Semiconductor element protective film
112, 912: Metal electrode 113, 913: Junction 115, 915: Chlorine 116, 916: Sulfur 917: Microcrack

Claims (5)

A die pad and a semiconductor element disposed on the die pad and having a plurality of electrode pads;
A connecting portion disposed on the electrode pad;
A plurality of external terminals arranged around the die pad;
A wiring electrically connected to the external terminal and the electrode pad;
A sealing body that seals at least the semiconductor element and the entire wiring;
The sealed package is a resin material, and the resin material contains less than 100 ppm of sulfur and chlorine, respectively, when measured by a total analysis.   2. The semiconductor package according to claim 1, wherein each of the sealing bodies contains 50 ppm or less of sulfur and chlorine when measured by a total analysis.   The semiconductor package according to claim 1, wherein a plurality of the semiconductor elements are stacked.   The semiconductor package according to claim 1, wherein a main component of the wiring is copper.   The semiconductor package according to claim 1, wherein the external terminal is any one of a lead and a solder bump.

Images