JPH11251319A - Manufacture of protective film of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacturing method of the protective film of a semiconductor device. SOLUTION: A first photosensitive polyimide film 106 and a second photosensitive polyimide film 108 positioned on the surface of the semiconductor device for functioning as the protective film are manufactured by respective processes. The first photosensitive polyimide film 106 is thinly coated so as to accurately open the position of a bonding pad 102 for connecting a lead frame first. Then, the second photosensitive polyimide film 108 is formed thick so as to protect the semiconductor device from external influence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a protective film for a semiconductor device, and more particularly, to a semiconductor having a thickness that is hardly affected by external influences such as cosmic rays in securing a photographic process margin. The present invention relates to a method for manufacturing a protective film of a memory device.

[0002]

2. Description of the Related Art With the recent development of semiconductor memory device manufacturing technology and expansion of application fields, large-capacity memory devices have been actively developed. Such semiconductor memory devices are roughly classified into volatile and nonvolatile. Volatile memory devices such as SRAM (Static Random Access Memory) and DRA
M (Dynamic Random Access Memory) has a characteristic that data is deleted at power-off. On the other hand, non-volatile memory devices such as ROM (Read Only Memory) and EPROM (Erasabl
e and Programmable ROM), EEPROM (Electrically
Erasable and Progammable ROM) have the characteristic that once input data is maintained even when the power is turned off.

In particular, a DRAM temporarily stores data temporarily and a non-volatile memory device stores data permanently in a built-in capacitor. In both types of memory, data storage capacity is determined by the capacity of the capacitor. 2. Description of the Related Art As semiconductor memory devices have become more highly integrated, the area of a capacitor has been gradually reduced, and as a result, the capacitance of the capacitor has been decreasing. Data stored in a capacitor having a limited capacitance is liable to change during operation of a memory cell due to external influences, for example, cosmic rays such as α-particles and radiation, and frequent reading errors occur. In addition, when a physical shock generated during a packaging process is transmitted to the semiconductor memory device, the semiconductor memory device may malfunction or the capacitor may be changed, thereby deteriorating the reliability of the device.

In order to minimize such read errors and malfunctions, manufacturers in this field complete a semiconductor chip 1 as shown in FIG. 1 and connect a lead frame 3 thereto using wires 2. Has been packaged with the molding protective film 4. Usually, an epoxy resin has been used as the molding protective film so as to appropriately buffer external physical forces and impacts, but this is a problem that it is weak against penetration of cosmic rays).

Accordingly, recently, a protective film using a photosensitive polyimide is formed under the molding protective film to a certain thickness in order to prevent penetration of charged cosmic rays, for example, α particles, which cannot be blocked by the epoxy resin. Has formed.
Such a photosensitive polyimide protective film not only protects the semiconductor device by relaxing external physical forces and shocks, but also absorbs charged cosmic rays such as α particles into the photosensitive polyimide film. It is prevented from penetrating into the semiconductor device, and as a result, data stored in the capacitor is completely protected. Therefore, with the miniaturization of memory cells, the importance of the polyimide protective film is also increasing.

However, in order to accurately form a desired pattern by subjecting the photosensitive polyimide film to a photographic and developing process, there is a problem (disadvantage) that the coating thickness must be limited to about 10 μm or less. When the photosensitive polyimide coating thickness is limited to about 10 μm or less, a desired pattern can be obtained through a photographing and developing process, but it is too thin as a protective film of a semiconductor device. Accordingly, there is a need for a method of manufacturing a protective film for a semiconductor memory device having a thickness sufficient to secure a photo process margin and protect the semiconductor device from external influences such as cosmic rays.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems by securing a photographic process margin while reducing the thickness to such an extent that it is hardly affected by external influences such as cosmic rays. It is an object of the present invention to provide a method for manufacturing a protective film of a semiconductor memory device having the same. It is another object of the present invention to provide a method for manufacturing a polyimide protective film capable of securing a process margin by coating a thin photosensitive polyimide. It is still another object of the present invention to provide a method of manufacturing a polyimide protective film having a sufficient thickness to completely protect a semiconductor memory device from external influences.

[0008]

In order to achieve the above object, a method for manufacturing a protective film of a semiconductor device according to the present invention comprises:
After a metal pad functioning as a bonding pad to which a lead frame is connected and an insulating film are sequentially formed on a substrate, a first protective film is formed so as to be suitable for a set exposure margin. Then, an opening is formed in a metal pad region corresponding to a predetermined bonding pad region by patterning the first protective film using a mask pattern and etching a part of the insulating film. Next, a second protective film is formed on the entire surface of the resultant, and a photo process is performed with a margin larger than the exposure margin to remove the second protective film in the opening. This can prevent the charged particles from penetrating into the element region of the semiconductor device.

[0009]

Preferred embodiments according to the present invention will be described below in detail with reference to the accompanying drawings. In the drawings, the same reference numerals and numbers are used for the same constituent elements and portions as much as possible.

[0010] In the following description, specific specific items are shown, but it is obvious to those skilled in the art that the present invention can be practiced without being limited thereto. is there. In addition, description of related well-known techniques, for example, formation of an insulating film on a chip, die bonding, and a packaging process will be appropriately omitted.

FIG. 2 is a layout diagram of the semiconductor chip 1 of FIG. Referring to FIG. 2, the normal cell region 1
0, a redundant cell area 20, a fuse box area 30, and a bonding pad area 40 are shown. The normal cell area 10 is an area for storing data. Many unit cells are arranged in a matrix of rows and columns. A redundant cell area 20 is formed on the upper and side surfaces of the normal cell area 10. ing. A fuse box region 30 for driving the redundant cell at the time of repair is formed around the redundant cell.

Further, a bonding pad region 40 for connecting a lead frame is formed at an upper edge portion of the chip 1. In a later step, a protective film using photosensitive polyimide is formed on the entire surface of the chip 1 in order to protect the chip 1 from the external influence, which is the gist of the present invention. However, the polyimide film of the bonding pad area 40 for connecting the lead frame to the chip 1 is completely removed, and the area of the fuse box 30 used for driving the redundant cell at the time of repair is predetermined to facilitate laser cutting. Only the thickness of the photosensitive polyimide is left.

FIGS. 3 to 9 show the steps of manufacturing the protective film of the semiconductor device according to the first embodiment of the present invention.
It is sectional drawing shown in order along the D 'line. First, FIG.
Shows a step of forming the metal pad 102 on the semiconductor substrate 100. A metal material is formed on the semiconductor substrate 100 having an oxide film formed by partially oxidizing the surface. Thereafter, a photo and etching process is performed on the metal material to form a metal pad 102 as shown in FIG. 3A. The metal pad 102 formed on a part of the semiconductor substrate 100 functions as a bonding pad to which a lead frame is connected in the next step.

FIG. 4 shows an insulating film 104 and a first photosensitive polyimide film 1 on the semiconductor substrate 100 and the metal pads 102.
06 is shown in order. The metal pad 102
The insulating film 104 and the first
Photosensitive polyimide films 106 are sequentially formed. The first
The photosensitive polyimide film 106 is coated to a thickness of about 10 μm or less so as to be accurately patterned by exposure and development processes.

FIG. 5 shows the first photosensitive polyimide film 106.
Is shown. The first photosensitive polyimide film 1
06, the mask pattern 107 is covered. Thereafter, the first photosensitive polyimide layer 106 coated on the metal pad 102 is partially exposed so as to be developed.

FIG. 6 shows the first photosensitive polyimide film 106.
Shows a stage in which is developed by the exposure process. The exposed portion of the first photosensitive polyimide film 106 is vaporized and developed without a separate developing solution, and the portion covered with the mask pattern 107 remains as it is.
Since the first photosensitive polyimide film 106 is relatively thinly coated, it is developed into a desired pattern. The upper surface of the insulating film is partially exposed at the developed portion of the first photosensitive polyimide film 106. In this step, the first photosensitive polyimide film 106 existing on the fuse box region used at the time of repair is also developed at the same time, and is left at a predetermined thickness sufficient for laser cutting.

FIG. 7 shows a step in which a partial surface of the metal pad 102 is exposed. The first photosensitive polyimide film 1
A part of the insulating film 104 exposed by the pattern 06 is etched away. As a result, the metal pad 1
The surface of No. 02 is exposed as much as the symbol 'A'. The code 'A'
The portion is a bonding pad portion to which the lead frame is connected.

FIG. 8 shows the steps of forming and exposing the second photosensitive polyimide film 108. A second photosensitive polyimide layer 108 is coated on the bonding pad portion defined by the reference character “A” and on the first photosensitive polyimide layer 106. Here, the second photosensitive polyimide film 10
8 is coated with a thickness of about 10 μm or more, which is sufficient to protect the semiconductor device from external physical impacts and charged particles such as α. Then, after covering the mask pattern 109 on the second photosensitive polyimide film 108, the region including at least the bonding pad portion defined by the symbol 'A' is exposed. At this time, the second photosensitive polyimide film 108 may have a sufficient process margin because a precise pattern exposing the bonding pad region is already formed by the first photosensitive polyimide film 106.

FIG. 9 shows a completed stage of the protection film according to the first embodiment of the present invention. The second photosensitive polyimide film 108 is exposed to light to develop the second photosensitive polyimide film 108 in a region indicated by a symbol 'C'. At this time, the first photosensitive polyimide film 106 indicated by the symbol 'B' is also developed to form the same pattern as the second photosensitive polyimide film 108. Then, the first photosensitive polyimide film 1
06 and the second photosensitive polyimide film 108 at the same time
The polyimide protective film is completed by heat treatment (110) at 0 ° C. and curing.

According to the above-described method, the position of the bonding pad for bonding the lead frame can be accurately opened by coating the first photosensitive polyimide film thinly. In addition, the second photosensitive polyimide film may have a sufficient process margin due to the pattern of the first polyimide film already formed, and may be formed with a sufficient thickness to substantially protect the semiconductor memory device. In addition, when the bonding pad is opened, the patterned first photosensitive polyimide film is used as an etching mask, so that the process can be simplified and the process time can be reduced. Further, the process can be simplified by simultaneously curing the first photosensitive polyimide film and the second photosensitive polyimide film.

FIGS. 10 to 12 show a step of manufacturing a protective film of a semiconductor device according to a second embodiment of the present invention.
It is sectional drawing shown in order along -D '. Referring to FIG. 10, a first photosensitive polyimide layer 106-1 having a metal pad 102, an insulating layer 104, and an opening 'A' is formed on a semiconductor substrate 100. The opening 'A'
The manufacturing process up to the formation of is the same as the manufacturing process shown in FIGS. However, in this embodiment, after the opening 'A' is formed in the first photosensitive polyimide film, a heat treatment (107-1) is performed at about 300 ° C. to form the cured first photosensitive polyimide 106-1. Let it.
As a result, there is an advantage that even the edge of the metal pad 102 is protected.

FIG. 11 shows the steps of forming and exposing the second photosensitive polyimide film 108. A second photosensitive polyimide layer 108 is coated on the bonding pad portion defined by the reference character "A" and on the cured first photosensitive polyimide film 106-1 excluding the "A" portion.
Here, the thickness of the second photosensitive polyimide film 108 is:
Coating is performed with a thickness of about 10 μm or more, which is sufficient to protect the semiconductor device from charged particles such as external physical impact and α. Then, exposure is performed using the mask pattern 109 on a region including at least the bonding pad portion defined by the reference character “A”. At this time, since a precise pattern exposing the bonding pad region is already formed by the first photosensitive polyimide film 106-1, the second photosensitive polyimide film 108 can secure a sufficient process margin.

FIG. 12 shows a stage of completing a protective film according to an embodiment of the present invention. The second photosensitive polyimide film 108 is exposed to form the second photosensitive polyimide film 108 in a region indicated by a symbol 'C'. At this time, since the first photosensitive polyimide film 106 has already been heat-treated and cured, the first photosensitive polyimide film 106 indicated by the symbol 'B' remains without being developed. Next, the patterned second photosensitive polyimide film 108 is heat-treated at about 300 ° C. and cured to complete a polyimide protective film.

According to the above-described method, the first photosensitive polyimide film is thinly coated to accurately open the position of the bonding pad for connecting the lead frame, and the second photosensitive polyimide film is substantially a semiconductor memory device. Is formed with a sufficient thickness to protect the substrate. Since the first photosensitive polyimide film is formed thin, a sufficient process margin can be secured when the bonding pad is opened. Further, the second photosensitive polyimide film has a sufficient process margin since the bonding pad is already opened by the first photosensitive polyimide film, and is formed thick so as to substantially protect the semiconductor device. By forming the respective thicknesses of the polyimide films in this manner, a sufficient process margin can be secured in each process step.

When the bonding pad for connecting the lead frame is opened, the first patterned pad is opened.
By using the photosensitive polyimide film as an etching mask, the process can be simplified, the process time can be shortened, and the manufacturing cost can be reduced, and the edge of the bonding pad can be formed by pre-curing the first photosensitive polyimide film. Can protect. As described above, the present invention has been described as the preferred embodiments, but it is obvious that various modifications and variations are possible within the spirit of the present invention described in the appended claims.

[0026]

As described above, according to the present invention, the process can be simplified, the process time can be reduced, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a typical sectional view of a packaged semiconductor chip.

FIG. 2 is a layout diagram of the semiconductor chip of FIG. 1;

FIG. 3 is a cross-sectional view showing a manufacturing step of the protective film of the semiconductor device according to the first embodiment of the present invention, taken along section line DD ′ of FIG. 2;

FIG. 4 is a cross-sectional view showing a manufacturing step of the protective film of the semiconductor device according to the first embodiment of the present invention, taken along section line DD ′ of FIG. 2;

FIG. 5 is a cross-sectional view showing a manufacturing step of the protective film of the semiconductor device according to the first embodiment of the present invention, taken along section line DD ′ of FIG. 2;

FIG. 6 is a cross-sectional view showing a manufacturing step of the protective film of the semiconductor device according to the first embodiment of the present invention, taken along section line DD ′ of FIG. 2;

FIG. 7 is a cross-sectional view showing a manufacturing step of the protective film of the semiconductor device according to the first embodiment of the present invention, taken along section line DD ′ of FIG. 2;

FIG. 8 is a cross-sectional view showing a manufacturing step of the protective film of the semiconductor device according to the first embodiment of the present invention, taken along section line DD ′ of FIG. 2;

FIG. 9 is a cross-sectional view showing a manufacturing step of the protective film of the semiconductor device according to the first embodiment of the present invention, taken along section line DD ′ of FIG. 2;

FIG. 10 is a cross-sectional view showing a manufacturing step of the protective film of the semiconductor device according to the second embodiment of the present invention along the cutting line DD ′ in FIG. 2;

FIG. 11 is a cross-sectional view showing a manufacturing step of the protective film of the semiconductor device according to the second embodiment of the present invention along the cutting line DD ′ in FIG. 2;

FIG. 12 is a cross-sectional view showing a manufacturing step of the protective film of the semiconductor device according to the second embodiment of the present invention, taken along section line DD ′ of FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 semiconductor chip 10 normal cell region 20 redundant cell region 40 bonding pad region 100 semiconductor substrate 102 metal pad 104 insulating film 106 first photosensitive polyimide 107 mask pattern 108 second photosensitive polyimide film

Claims (9)

[Claims] In a method of manufacturing a protective film of a semiconductor device, a metal pad functioning as a bonding pad to which a lead frame is connected and an insulating film are sequentially formed on a substrate, and then a suitable exposure margin is set. Forming a first protective film as described above, and patterning the first protective film using a mask pattern and etching a part of the insulating film to form a metal pad region corresponding to a predetermined bonding pad region. Forming an opening; and forming a second protective film on the entire surface of the resultant structure, and removing the second protective film in the opening through a photographic process having a margin equal to or greater than the exposure margin. A method for preventing particles from penetrating into an element region of a semiconductor device. 2. The device according to claim 1, wherein the opening is also formed in a fuse box area in the element area.
The described method. 3. The method according to claim 1, wherein the second protection film is formed to be thicker than the first protection film. 4. The method according to claim 1, wherein the first protective film has a thickness of 10 μm or less. 5. The method according to claim 1, wherein the second protective film has a thickness of 10 μm or more. 6. The method according to claim 1, wherein the first protective film and the second protective film are the same material film. 7. The method according to claim 6, wherein the first protective film and the second protective film are made of photosensitive polyimide. 8. The method according to claim 1, wherein the first protective film and the second protective film are
2. The method according to claim 1, wherein the curing is performed by simultaneous heat treatment at 50 to 350.degree. 9. The method according to claim 1, wherein the first protective film and the second protective film are
The method according to claim 1, wherein each of the heat treatments is performed at 50 ° C. to 350 ° C. for curing.