Patent Application
20230110402
The present disclosure relates to a semiconductor device and a method for packaging the semiconductor device.
Packaging semiconductor device typically includes bonding wires to a bond pad on a semiconductor device die. The bonded wires allow signals to be transmitted from and into the semiconductor device die. The bond pads on the device die and the wires are usually made from different materials, and the bonding makes use of alloys formed from the different materials. Subsequent to the bonding, the packaging process encapsulates the bonded combination using molding compounds. Particular components, for example chloride ions (chloridion), chemically react with the alloys due to galvanic effect, which can result in corrosion, that bring challenges to the reliability of the bonded interconnections.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
In one embodiment, a method of packaging a semiconductor device includes: bonding a ball at an end of a bond wire to a bond pad of a semiconductor device die in an aperture of a shielding layer of the semiconductor device; and sealing the part of the bond pad exposed by the aperture of the shielding layer by deforming the ball of the bond wire to fill the aperture of the shielding layer. The aperture of the shielding layer includes an edge wall, and exposes a part of the bond pad. The shielding layer covers a remaining part of the bond pad. The aperture of the shielding layer is completely filled with the ball of the bond wire, thereby deforming the edge wall of the shielding layer.
In another embodiment, a semiconductor device includes a device die, a connector, and molding compound. The device die includes a bond pad and a shielding layer covering a part of the bond pad and having an aperture over a remaining part of the bond pad. The connector has an end electrically and mechanically connected to the bond pad within the aperture. The end of the connector contacts an edge wall of the aperture. The molding compound encapsulates the device die and the end of the connector. The molding compound is remote from the bond pad.
In yet another embodiment, a semiconductor device includes a substrate having a surface; at least a bond pad on the surface of the substrate; and a shielding layer on the surface. The shielding layer includes an aperture to expose a part of the bond pad. The shielding layer covers a remaining part of the bond pad. The shielding layer is deformable such that the aperture is expandable to receive an end of a bond wire to be bonded to the bond pad.
So that the manner in which the above recited features of the present disclosure can be understood in detail, a more detailed description of the disclosure may be had by reference to embodiments, some of which are illustrated in the appended drawings. The appended drawings illustrate only typical embodiments of the disclosure and should not limit the scope of the disclosure, as the disclosure may have other equally effective embodiments. The drawings are for facilitating an understanding of the disclosure and thus are not necessarily drawn to scale. Advantages of the subject matter claimed will become apparent to those skilled in the art upon reading this description in conjunction with the accompanying drawings, in which like reference numerals have been used to designate like elements, and in which:
The semiconductor device 100 includes a shielding layer 106 deposited on the surface thereof. The shielding layer 106 is also patterned to expose the whole of the bond pad 102. The passivation layer 104 and the shielding layer 106 are deposited to protect underlying parts of the semiconductor device 100, for example active regions, from any foreign materials (FM) such as ambient moisture, dust, or other chemical pollutants. However, the bond pad 102 shown in
The shielding layer 206 is configured to have an aperture 208 over the bond pad 204. The aperture 208 allows the part of the bond pad 204 to be exposed. In the embodiment shown, the aperture 208 is circular with a diameter of less than 45 μm, for example 40-45 μm, and an opening size of the bond pad 204 (bond pad opening, BPO, typically formed through patterning the passivation layer to expose the bond pad 204) may typically be generally square with a width and length of 52 μm; it is greater than the diameter of the aperture 208, so that part of the bond pad 204 is covered by the shielding layer 206, and another part of the bond pad 204 is left exposed from the aperture 208. The shielding layer 206 according to the embodiment is formed of polymer or organic silicon resin. More particularly, the shielding layer 206 can be formed of polyimide or methyl silicone through a spin coating process during fabrication of the semiconductor device substrate 202. In detail, soluble polyimide precursor, for example amide copolymer of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), oxydianiline (ODA), or meta-phenylenediamine (MPD), is spin coated onto the surface of the substrate 202. The spin coated substrate 202 is then applied a negative mask before sent for exposure under a thermal cure and/or ultraviolet radiation process, to be cured and/or cross-linked. After the curing process, the masked and uncured area of the coat material, for example an area of the aperture 208, is removed by spraying solvent, plasma etch, or reactive ion etching (RIE), and the part of the bond pad 204 is exposed from the aperture 208. In the embodiment, the shielding layer 206 has a thickness of between 2 μm and 7 μm, preferably 2-5 μm, and may have a thickness of 4 μm.
It will be understood that the aperture 208 further allows a connector, for example a bond wire, to electrically and mechanically connect to the exposed part of the bond pad 204, which will be further described hereunder. The bond pad 204, as described above, can be made of aluminum material according to one or more embodiments, and the bond wire to be connected is typically made of copper. The electrical and mechanical connection between the bond pad 204 and the connector is implemented by forming an intermetallic compound (IMC, which in the case of a copper wire and an aluminum bond pad is an Al—Cu alloy) as an interface region using the Al material of the bond pad 204 and the Cu material of the connector. By forming the alloy interface region (and specifically the IMC), an end of the connector (also referred to as a “ball-bond” or “bonded ball”) bonds to the bond pad 204 within the aperture 208. The shielding layer 206 according to the embodiment, and in particular its sidewall, is deformable to allow the aperture 208 to be expanded laterally when receiving the connector to be connected to the exposed part of the bonding pad 204. Typically, the bond or join between the shielding layer 206 and the bond pad 204 itself is not affected by the deformation; any stress which might tend to make the shielding layer 206 peel away from the perimeter of the aperture 208 is balanced by the downwards force from the relatively rigid bonded ball at the end of the connector. The diameter of the aperture 208 is less than a diameter of the end of the connector (the bonded ball), such that the aperture 208 is completely filled with the bonded ball and/or the formed IMC, leaving no space between the side of the bonded ball and the “splash” of the bond pad 204, for subsequent molding compounds. By “splash” is meant the region of the bond pad 204 which is the formed alloy interface region or peripheral regions thereto, the “splash” may also be referred to as “Al splash” in the case of aluminum bond pads. In other words, the bond wire deforms during bonding—which is the case with convention bonding—but the limited size of the aperture 208 in the shielding layer 206 limits the lateral spread of the bond wire material as it forms the ball-bond and fills the aperture 208, thereby providing an effective seal against ingress of moisture or other volatile materials. Because the molding compound does not contact with the bond pad 204 or the Al—Cu alloy conjunction (the IMC), that is to say, it is entirely remote from the bond pad 204, the connection between the connector and the bond pad 204 can be protected from corrosion.
Referring now to
The bond wire 302 in the embodiment shown is made from copper, and an Al—Cu alloy interface region is formed at a bond interface between the Cu end 304 and the Al bond pad 204. The end 304 and the formed Al—Cu alloy completely fill the aperture 208 of the shielding layer 206, while the rest of the bond pad 204 is covered with the shielding layer 206, leaving no space for ingress of molding compound 306. The aperture 208 of the shielding layer 206 has an edge wall 210 which is in contact with the end 304 of the bond wire 302. In other words, the molding compound 306 that is introduced into the semiconductor device 300 in subsequent encapsulation processes is unable to reach near the interface between the bond pad 204 and the end 304. The bond pad 204 and the end 304 with the Al—Cu alloy are thereby protected from corrosion.
The method of
Step 406, the connected device die 200 and the connector 302 is encapsulated with molding compounds 306, to produce a packaged semiconductor device 300. As it is understood, because there is no gap between the shielding layer 206, the bond pad 204, and the end 304, during encapsulation the molding compound 306 does not flow to contact the Al—Cu alloy at the jointing interface of the bond pad 204 and the ball end 304, or the Al bond pad 204, but is remote from the bond pad 204 or the interface region of alloy. The provided isolations of the molding compound 306 from the alloy and the bond pad 204 prevent corrosions due to the galvanic effect as explained above.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the subject matter (particularly in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “coupled” and “connected” both mean that there is an electrical connection between the elements being coupled or connected, and neither implies that there are no intervening elements. In describing transistors and connections thereto, the terms gate, drain and source are used interchangeably with the terms “gate terminal”, “drain terminal” and “source terminal”. Recitation of ranges of values herein are intended merely to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation, as the scope of protection sought is defined by the claims set forth hereinafter together with any equivalents thereof entitled to. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illustrate the subject matter and does not pose a limitation on the scope of the subject matter unless otherwise claimed. The use of the term “based on” and other like phrases indicating a condition for bringing about a result, both in the claims and in the written description, is not intended to foreclose any other conditions that bring about that result. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosure as claimed.
Preferred embodiments are described herein, including the best mode known to the inventor for carrying out the claimed subject matter. Of course, variations of those preferred embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventor intends for the claimed subject matter to be practiced otherwise than as specifically described herein. Accordingly, this claimed subject matter includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed unless otherwise indicated herein or otherwise clearly contradicted by context.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202111184282.1 | Oct 2021 | CN | national |
