KR100586607B1 - Method for protecting by using blocking plate - Google Patents

Abstract

The present invention relates to a method of protecting a surface of a semiconductor device, and prevents damage to the chip surface in the process of disassembling the semiconductor device for failure analysis of the already manufactured semiconductor device. The surface protection method of the present invention includes removing a package body of a packaged semiconductor device, disposing a blocking plate on an electrode pad region formed on an active surface of the semiconductor chip exposed from the removed package body, and Removing a protective film (eg, a passivation layer and a polyimide layer) applied to the active surface of the chip. The blocking plate may be manufactured by back-grinding a semiconductor wafer for manufacturing a semiconductor chip to make the thickness of 1 to 2 m, and then cutting the polished wafer into a predetermined length and width. Since the blocking plate is placed in the electrode pad region and then the protective film removal process (for example, plasma etching process or reactive ion etching process) is performed, the electrode pad and the bonding wire bonded to the electrode pad are separated from the reactive particles or reactive ions. Protected. In addition, damage or hardening of the electrode pad or the bonding wire may be prevented, so that the application or input / output of a signal for failure analysis may be performed more accurately.

Decapsulation, Surface Protection, Electrode Pads, Reactive Ion Etching

Description

Method for protecting the surface of semiconductor chip using a blocking plate {Method for Protecting by Using Blocking Plate}

FIG. 1A is a plan view illustrating a process of decapsulation of a packaged semiconductor chip, and FIG. 1B is a cross-sectional view of FIG. 1A taken along line 1B-1B ′.

Figure 2a and Figure 2b is a schematic diagram for explaining the process of manufacturing the blocking plate of the present invention.

3A is a partial plan view showing a state in which a blocking plate of the present invention is disposed in a process of disassembling a packaged semiconductor chip, and FIG. 3B is a cross-sectional view taken along line 3B-3B ′ of FIG. 3A.

<Description of Major Symbols in Drawing>

10: semiconductor chip package 12: package body

14: lead frame lead 16: bonding wire

17: ball bonding 20: semiconductor chip

22: active surface of semiconductor chip 24: protective film

26: electrode pad 50: wafer for manufacturing a blocking plate

52a-52d: Block 60: Polishing machine

70: cutting chuck 80: cutting machine

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor technology, and more particularly, to a method of protecting a surface of a semiconductor chip during a decapsulation process for failure analysis of a semiconductor device.

In order to analyze the defect of the chip after the package process, the package body such as the epoxy molding compound (EMC) is removed and the polyimide (PIX) film and the passivation layer (coated on the active surface of the chip) Decapsulation is necessary to remove the passivation layer. Package bodies such as EMC are removed using fuming nitric acid or fuming sulfuric acid, and the polyimide film and protective film are removed by an etching process such as Reactive Ion Etching (RIE).

In the reactive ion etching process, gas ions due to RF discharge collide with the surface of a sample (semiconductor chip) in a plasma state, thereby weakening the interatomic bonding force on the surface or removing the interatomic bonding. However, if the CF ₄ , O ₂ gas injected into the etching chamber and 200 ~ 300 W are applied in order to cause RF discharge in the process of ionizing these gases, the protection material as well as the protection material of the chip surface is not applied. Ion damage is caused to the non-region, that is, the electrode pad. The electrode pads have ball bonding wires that connect the circuit elements inside the semiconductor chip to the outside (for example, leads of lead frames), and ball bonding or electrode pads are used to prevent ion damage. In this case, it is impossible to check the electrical characteristics of the semiconductor chip to be analyzed for failure or to apply a signal necessary for the failure analysis to the semiconductor chip. In addition, even though ball bonding or electrode pads are not damaged to the extent that the signal cannot be applied, it is difficult to accurately and accurately analyze the electrical characteristics of the semiconductor chip to analyze the defects because the impedance value is not transferred correctly. There is a problem that it becomes difficult.

The present invention solves this conventional problem so that failure analysis of a semiconductor device can be made more accurately.

Another object of the present invention is to prevent damage to the bonding wire and the electrode pad generated when the organic material protecting the surface of the semiconductor chip, that is, the polyimide and the protective film.

The method for protecting a surface of a semiconductor device according to the present invention includes removing a package body of a packaged semiconductor device, and placing a blocking plate on an electrode pad region formed on an active surface of a semiconductor chip exposed from the removed package body. And removing a protective film (eg, a passivation layer and a polyimide layer) applied to the active surface of the semiconductor chip. The blocking plate may be manufactured by back-grinding a semiconductor wafer for manufacturing a semiconductor chip to make the thickness of 1 to 2 탆, and then cutting the polished wafer into a predetermined length and width. Since the blocking plate is placed in the electrode pad region and then the protective film removal process (for example, plasma etching process or reactive ion etching process) is performed, the electrode pad and the bonding wire bonded to the electrode pad are separated from the reactive particles or reactive ions. Protected.

Embodiment

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

FIG. 1A is a plan view of a partially disassembled semiconductor chip packaged for defect analysis, and FIG. 1B is a cross-sectional view taken along line 1B-1B ′ of FIG. 1A.

As shown in FIG. 1, the semiconductor chip package 10 has a structure in which the semiconductor chip 20 is sealed and protected by a package body 12 such as, for example, an epoxy molding resin. Therefore, in the case where it is determined that the package is completed and the semiconductor chip is inspected as defective, the package body 12 must be removed first to perform the disassembly work for identifying the cause of the defect. The semiconductor device has a structure in which several layers made of different materials are stacked. Such a multilayer semiconductor chip is likely to be defective due to a manufacturing error or contamination due to fine impurities. It is common to carry out a complete inspection of the finished product to identify the cause of the defect. The failure analysis can be divided into structural analysis, circuit analysis, or design analysis. For this analysis, it is necessary to peel off the laminated film forming the semiconductor device and find the cause of the defect inside the chip. Through defect analysis, it is possible to know whether there is a cause of defect in the package assembly process or whether a problem occurs during the wafer processing process or the circuit design stage, and the result is reflected in the assembly process, wafer processing process, and design process to improve the yield of semiconductor devices. Increase the reliability and productivity of the product.

In the decomposition process for the failure analysis, the package body 12 is removed by hand using, for example, fuming nitric acid or fuming sulfuric acid, or by using automated equipment. FIG. 1A shows a portion of the semiconductor chip 20 and lead frame leads 14 with portions of the package body 12 removed.

On the active surface 22 of the semiconductor chip 20, a protective film 24 is applied to the entire surface. A lamination structure for the operation of the semiconductor chip 20 is formed under the passivation layer 24, but the lamination structure is omitted for simplicity of the drawings. The passivation layer 24 is formed of, for example, a passivation layer made of a nitride film and a polyimide layer, and the polyimide layer is a kind of buffer layer for preventing cracking due to stress generated in the process of forming the package body. Conventional methods of removing the protective film 24 are plasma etching or reactive ion etching. In addition, wet chemical etching may be used. Plasma etching is dry anisotropic etching, which produces chemically reactive particles from relatively inert gases (eg O ₂ , C ₂ F ₆ , CF ₄ , CHF ₃ , SF ₆ , CCLF ₂ -CF ₃ ) through incandescent discharges. In addition, the reactive particles are diffused and absorbed on the surface of the protective film 24 to be etched, and then the protective film 24 is removed by making the volatile by-products through the reaction of the particles and dropping the by-products from the surface. Reactive ion etching, on the other hand, is similar to plasma etching, except that accelerated reactive ions are dropped onto the surface to be etched. The accelerated reactive ions not only react chemically with the protective film 24 but also allow the protective film 24 to be removed through a sputtering process that strikes the surface of the protective film 24. That is, reactive ion etching removes the protective film 24 through a chemical reaction and sputtering process.

When the protective film 24 is removed from the active surface 22 of the semiconductor chip 20 by plasma etching or reactive ion etching, reactive particles or accelerated reactive ions do not affect only the protective film 24. It also affects the electrode pads 26 arranged on the four sides of the face 22 and the bonding wires 16 connecting the electrode pads 26 with the lead frame leads 14. As shown in FIG. 1, the bonding wires 16 are ball bonded to the electrode pads 26 and stitch bonded to the leads 14. In the process of removing the protective film 14, aluminum or copper may be used. The electrode pad 26 made of metal may be damaged by the reactive particles or the reactive ions, and may be cured. The bonding wire 16 and the ball bonding 17 made of gold (Au) may also be damaged. The electrode pads 26 and the bonding wires 16 serve to connect the internal circuits of the semiconductor chip 20 to the outside, and when such a connection part is damaged, an inspection signal is input to the semiconductor chip 20 for failure analysis. In addition, even if the output signal of the semiconductor chip 20 cannot be read or the signal is inputted or outputted, the impedance of the connection portion is changed so that accurate input and output of the signal is impossible, so that the failure analysis cannot be performed properly.

In order to prevent such a problem from occurring, in the present invention, when the protective film 24 is removed, the electrode pad 26, the bonding wire 16, and the ball bonding 17 may be protected from reactive particles or accelerated reactive ions. Use a plate. The manufacturing process of such a blocking plate will be described with reference to FIG. 2.

Referring to FIG. 2A, a semiconductor wafer 50 is prepared first. As the semiconductor wafer 50, a wafer made of the same material as the wafer used to manufacture the semiconductor chip 20 of FIG. 1 can be used. The tape 65 is attached to one side of the wafer 50 and subjected to back grinding by the grinder 60. In the back surface polishing process, the wafer 50 is polished by supplying an etchant while rotating the polishing machine 60 at a high speed. Currently, the semiconductor wafer is thin enough to have a thickness of 50 μm or less. In the present invention, it is preferable that the thickness 'd1' of the remaining wafer 50 polished by the wafer polishing process is about 1 to 2 μm. When the thickness 'd1' of the polished wafer 50 is 3 μm or more, the bonding wire may be damaged by the blocking plate (see FIG. 3B).

Next, referring to FIG. 2B, the polished wafer 50 is fixed to a cutting chuck 70 for manufacturing a blocking plate and, for example, using a cutter 80 that rotates at a high speed at which a diamond blade is formed. The wafer 50 is cut into predetermined lengths and widths. In this way, several blocking plates 52a to 52d can be made of one wafer 50. The length and width of the blocking plate 52 is determined in accordance with the length and width of the electrode pad region of the semiconductor chip in which it is to be used.

As shown in FIG. 3A, each of the blocking plates 52a to 52d is arranged in four sides of the active surface 22 of the semiconductor chip 10, that is, in the region in which the electrode pads 26 are formed. Even if the protective film 24 is removed through the plasma etching or reactive ion etching process described above with the blocking plate 52 arranged in the electrode pad 26 region, as shown in FIG. 3B, the electrode pad 26 and the bonding wire are removed. (16) Since the ball bonding 17 is protected by the blocking plate 52 and is not directly affected by the reactive particles or the reactive ions, no damage occurs. The black dots just above the arrows in FIG. 3b represent reactive particles or reactive ions.

Although specific embodiments of the present invention have been described with reference to the drawings, this is intended to be easily understood by those skilled in the art and is not intended to limit the technical scope of the present invention. Therefore, the technical scope of the present invention is determined by the matters described in the claims, and the embodiments described with reference to the drawings may be modified or modified as much as possible within the technical spirit and scope of the present invention. For example, the blocking plate 52 of the present invention is not necessarily made of a semiconductor wafer, but may be made of another material capable of blocking reactive particles or reactive ions. It is not necessary to form both sides, but may be formed on two sides or may be formed in the center of the active region.

According to the present invention, damage may be prevented by protecting an exposed electrode pad or bonding wire without a protective film being covered on the surface of the semiconductor chip in a decomposition process for defect analysis of a semiconductor device.                     

In addition, according to the present invention prevents damage or hardening of the electrode pad or bonding wire for electrically connecting the semiconductor chip to the outside, and the application of the signal for failure analysis is made to accurately input and output the signal, more accurate and precise Defect analysis is possible.

Claims (3)

As a surface protection method of a semiconductor element, Removing the package body of the packaged semiconductor chip; Disposing a blocking plate on an electrode pad region formed on an active surface of the semiconductor chip exposed from the removed package body; Removing the protective film applied to the semiconductor chip active surface; The blocking plate protects an electrode pad and a bonding wire bonded to the electrode pad in the protective film removing step. In claim 1, The blocking plate is manufactured by grinding the semiconductor wafer back to a predetermined thickness and cutting the polished semiconductor wafer to a predetermined length and width. In claim 2, The blocking plate has a thickness of 1 to 2 μm, and the etching process performed in the protective film removing step includes a plasma etching process and a reactive ion etching process.

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