JP2664924B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a semiconductor manufacturing technique, and particularly to a method for forming a passivation protective film in a pretreatment process of a semiconductor wafer (hereinafter simply referred to as “wafer”). Regarding effective technology to apply.

[Conventional technology]

For examples of recent LSI processes, see the Industrial Research Council, published on November 18, 1987, “Electronic Materials Separate Volume, Guidebook for Ultra LSI Manufacturing and Testing Equipment”, page 41
There is P51.

In the above literature, various pretreatment steps by the CVD method are described, but recently, in the uppermost layer of the circuit forming surface of the semiconductor pellet, a resin filler or an insulating film is prevented from being broken due to application of unnecessary pressing force. Therefore, it is known to form a protective film by applying a synthetic resin such as a polyimide resin.

In the case where wire bonding is performed after the formation of the above-described protective film, a step of forming a bonding window by repeating etching processing on the protective film and the insulating film on the bonding pad is required. This step will be described with reference to FIGS. 6 (a) to 6 (e).

In FIG. 1A, reference numeral 61 denotes a semiconductor substrate, and 62 denotes a bonding pad made of aluminum (Al).

First, after a predetermined characteristic region (not shown) and the above-mentioned bonding pad 62 and the like are formed on a semiconductor substrate 61, an insulating film 63 made of phosphorus silicate glass or nitride is formed. An attached chelate film 64 is formed. Further, in FIG. 6A, a protective film 65 made of a synthetic resin such as a polyimide resin is formed on the chelate film 64 (FIG. 6A).

In order to form the bonding window 66 in the upper layer of the bonding pad 62 on the semiconductor substrate 61 thus formed to expose the bonding pad 62, the following steps are required.

That is, first, the uppermost protective film 65 of the bonding pad 62 is removed. In this step, first, the protective film 65 is removed.
A resist material 67a is applied to the upper layer of 65 (FIG. 9B). As the resist material 67a, a negative resist is used because of the etching characteristics of the protective film 65. In this negative resist, the chemical characteristics of the light-irradiated portion change, and the photomask 68a used for this resist also has a light-shielding structure in which only the portion to be etched away is shielded, as shown in FIG. It is a pattern to biao 70a.

Next, a part of the resist material 67a corresponding to the light shielding pattern 70a is removed, and the surface of the protective film 65 in the range is exposed. Subsequently, the exposed protective film
Etching is performed on the protective film 65 to remove a predetermined area of the protective film 65, and further, the underlying chelate film 64 is subjected to an etching process to expose the insulating film 63 over a predetermined area (FIG. 3C).

Subsequently, a resist material 67b is applied again to a predetermined range of the insulating film 63 exposed as described above. The resist material 67b is a positive resist and has a structure in which a resist portion corresponding to a portion of the photomask 68b without the light-shielding pattern 70b is removed by etching (FIG. 4D). Thus, the lower bonding pad 62 is exposed. (FIG. (E)).

[Problems to be solved by the invention]

As described above, since the upper protective film 65 and the lower insulating film 63 have different etching characteristics, in order to open the bonding window 66 and expose the bonding pad 62,
The negative polarity photoresist process and the positive polarity photoresist process had to be performed in independent processes. As described above, the number of photoresist steps becomes plural, which has been a major obstacle to efficient semiconductor device manufacturing.

Further, as described above, in the prior art, the combination of two etchings with a photomask is required for the etching with the negative polarity and the etching with the positive polarity.
As shown in FIG. 6, the etching range had to be limited to a wide range l ₁ (FIG. 6 (e)) from the pad edge. As a result, a part (l ₁ −l ₂ ) of the insulating film 63 around the bonding pad 62 is exposed, and a wire whose bonding point is shifted as shown by a broken line in FIG. When bonding or the like is performed, not only is the insulating film 63 destroyed, but there is also a possibility that a characteristic change occurs in a characteristic region of the semiconductor substrate 61 or an electrical failure occurs.

The present invention has been made in view of the above problems,
The aim is to efficiently carry out the manufacturing process of semiconductor devices, shorten the wafer processing process, and
It is an object of the present invention to provide a technique capable of improving protection reliability of a semiconductor pellet.

The above and other objects and novel features of the present invention are as follows.
It will be apparent from the description of this specification and the accompanying drawings.

[Means for solving the problem]

The outline of a representative invention among the inventions disclosed in the present application will be briefly described as follows.

That is, when an insulating film covering a bonding pad on a semiconductor substrate and a protective film made of a polyimide-based synthetic resin covering the insulating film are etched to form a bonding window directly above the bonding pad, By leaving the photoresist material formed on the protective film as it is, a laminated protective mask is formed by the photoresist material and the remaining portion of the protective film, and then the insulating film is formed using the laminated protective mask. By etching
The bonding window whose opening line coincides with the edge line is opened to expose a bonding pad, a wire is bonded to the exposed bonding pad by ultrasonic combined bonding, and then resin sealing is performed.

[Action]

According to the above-described means, even when it is necessary to use photoresist materials having different resist polarities for the upper layer and the lower layer, continuous exposure of the upper layer and the lower layer can be performed in one exposure step using a photomask. Etching can be performed, and the efficiency of the wafer process in the manufacture of semiconductor devices can be increased.

In addition, since only one photomask process is required, it is not necessary to consider a positional deviation due to a plurality of times of alignment for each mask, and the etching edges of the upper layer and the lower layer can be matched. Therefore, the lower insulating film and the like can be reliably protected by the upper protective film.

Embodiment 1 FIGS. 1A to 1D are explanatory cross-sectional views each showing a part of a wafer process according to an embodiment of the present invention, and FIG. 1E is a plan view of a bonding window. FIG. 2 is a schematic cross-sectional view for explaining the structure of the semiconductor device obtained by the present embodiment. FIG. FIG. 4 is a partially enlarged view showing a state of forming a pellet on a wafer.

The semiconductor device 1 of the present embodiment has a ROM (Read) obtained by dividing a wafer obtained by slicing a cylindrical semiconductor single crystal ingot made of silicon (Si) or the like in the radial direction.
Only pellets 2a having a function such as Only Memory) are formed in a matrix on the wafer with a dicing line 24 which is also a TEG (Test Element Group) forming region as a boundary as shown in FIG. The array is formed. Here, the formation state of each layer on the wafer, that is, the semiconductor substrate 2 will be briefly described.
In the figure, reference numerals 3A and 3B denote characteristic regions formed of N wells and P wells, 4 denotes a field oxide film formed thereon, 5 denotes a gate electrode, and 6 denotes a diffusion layer.

When the writing of ROM information is performed after the formation of each of the above layers, an interlayer insulating film 7 made of phosphorus silicate glass (PSG) is formed on the field oxide film 4 by a known technique such as a low-temperature vapor deposition method. After the contact through hole or the impurity for short-circuit prevention is introduced into the portion, the wiring layer 8 made of aluminum and the bonding pad 10 are simultaneously formed. Further, after the formation of the bonding pad 10, a heat treatment by hydrogen annealing is performed.

Subsequently, an insulating film made of phosphorus silicate glass or nitride is formed on the upper surface of the bonding pad 10.
11 is formed, and a chelate film 12 on which aluminum is thinly applied is further formed thereon (see FIG. 1A). The chelate film 12 prevents residues of the material to be etched when etching the protective film 13 described below,
This is for improving the etching removal efficiency. A protective film 13 made of a polyimide resin-based synthetic resin is further applied and formed on the upper layer of the chelate film 12 (FIG. 1A). In FIG. 2, the protective film 13 is formed over substantially the entire area of the pellet 2a except for the upper surface of the bonding pad 10, and the protective film 13 is formed on the It is formed to prevent destruction and the like.

By the way, a bonding window 14 is opened in the insulating film 11 and the protective film 13 immediately above the bonding pad 10. The following describes a step of opening the bonding window 14 with reference to FIGS. This will be described based on d).

First, when opening the upper protective film 13, the protective film 13
A resist material 15 is applied over the entire upper surface (FIG. 7A). The resist material 15 used here is a so-called negative resist, which is used because of its property compatibility with the material for forming the protective film 13. Therefore,
As shown in FIG.
A portion on which a light-shielding pattern 17 is formed is prepared at a portion where etching is to be performed, and a photoresist process is performed through a photomask 16. After the photosensitive process of the resist material 15 is completed, the light-shielding pattern 17 is removed. The corresponding portion of the resist material 15 is removed, and a predetermined area of the protective film 13 is exposed. (FIG. 2B). Next, using the resist material 15 as a mask, the protective film 13 is removed by an etching material such as hydrazine, and the lower chelate film 12 is exposed. Further, the chelate film 12 is removed by etching, and a predetermined surface of the underlying insulating film 11 is exposed (FIG. 3C). At this time, the resist material 15 obtained by etching the protective film 13 is left on the protective film 13.

Next, the exposed area of the insulating film 11 is removed by etching using the resist material 15 and the protective film 13 in the remaining state as a mask.

By the above-described etching process, the surface of the bonding pad 10 located in the lower layer is exposed over a predetermined range, and the opening of the bonding window 14 is completed (simultaneously (d) and (e)).

As described above, in the present embodiment, the protective film 13 located on the upper layer
Is removed in a predetermined range, and then the lower insulating film 11 is etched using the resist material 15 and the protective film 13 after the etching process as a mask. For this reason, the etching process of the protective film 13 and the insulating film 11 can be sequentially performed in one photomask process.
One photomask process is reduced to one. Therefore, it is possible to improve the processing efficiency in the pre-processing step of the wafer and to shorten the work completion, and to increase the manufacturing efficiency of the semiconductor device 1.

Further, according to this embodiment, since it is not necessary to align the photomask a plurality of times, it is possible to maintain a consistent hole diameter l from the stage of etching the protective film, and as shown in FIG. The opening of the bonding window 14 in which the edge lines of the portions coincide with each other becomes possible.

After the pre-processing step on the wafer is completed as described above, the back surface of the wafer is cut to a predetermined depth, and the back surface from which foreign substances and the like attached to the back surface have been removed is cleaned.
Subsequently, after a probe test or the like for testing the electrical characteristics of the area of each pellet 2a is performed, the pellet 2a is divided into individual pellets 2a by a dicing device (not shown). The pellet 2a thus obtained is adhered to the main surface of the lead frame 18 obtained by processing a conductive metal plate such as a 42 alloy or Kovar into a predetermined shape with an adhesive such as a silver paste 20.

Next, the bonding pad 10 in which the bonding window 14 is opened and exposed in the above-described process is formed from the inner lead 18a of the lead frame 18 and copper (Cu), gold (Au), aluminum (Al), or the like. Wire bonding that is electrically connected by the conductive wire 21 is performed.
This wire bonding step will be described below.

First, one end of a wire 21 protruding from a tip of a bonding tool such as a capillary (not shown) is heated by a discharge torch to form a spherical bonding ball 22,
The portion of the bonding ball 22 is pressed (thermo-compression bonded) in a heated state together with the application of ultrasonic vibration to the surface of the bonding pad 10 exposed by the opening of the bonding window 14 to form a bonding with the bonding ball 22. The pad 10 is joined by ultrasonic combined thermocompression bonding.

At this time, according to the present embodiment, as is apparent from FIG. 1D, the edges of the inner walls of the opening of the bonding window 14 coincide with each other, and the insulating film 11 around the bonding pad 10 is formed. Is almost completely covered by the protective film 13. Therefore, even if the bonding point is displaced from the exposed bonding pad 10, the elasticity of the protective film 13 can effectively prevent the insulating film 11 from being broken.

Next, the bonding tool lands on the predetermined surface of the inner lead 18a so as to draw a loop of a predetermined shape while protruding the wire 21 and applies the ultrasonic vibration to the abdomen of the wire 21 with respect to the inner lead 18a. Thermocompression bonding.

After completing the wire bonding step, the portion of the lead frame 18 inside the inner leads 18a is
Molding is performed with a resin 23 such as an epoxy resin. The resin molding is performed by placing the inner lead 18a in a mold having a cavity of a predetermined shape, injecting a molten resin 23 into the mold at a high pressure, and then curing the resin.

After completion of this resin molding process, lead frame 18
Each of the leads 18b is cut and formed into an independent state, and the semiconductor device 1 as shown in FIG. 2 is obtained.

Embodiment 2 FIG. 5 is an explanatory sectional view showing a part of a wafer process according to another embodiment of the present invention.

This embodiment is different from the first embodiment in that the synthetic resin film forming the protective film 13 is made of a resin having a photosensitive property whose chemical property is changed by irradiation with light of a predetermined wavelength.

That is, in FIG. 5, the structure of the insulating film 11 and the chelate film 12 formed on the semiconductor substrate 2 is the same as that of the first embodiment, but the protective film 13 formed on the chelate film 12 is , Itself is formed of a material having photosensitive characteristics. This photosensitive characteristic may have either polarity of negative characteristic or positive characteristic,
Photosensitive processing is performed by a photomask 16 corresponding to each characteristic.

FIG. 5 illustrates a case where the protective film 13 has a negative characteristic, and a portion of the photomask 16 corresponding to the light-shielding pattern 17 is removed by etching.

As described above, according to the second embodiment, since the protective film 13 itself has photosensitive characteristics, the application of the resist material 15 and the etching treatment of the resist material 15 are not required, and the protection is directly performed after the photomask process. The film 13 can be removed by etching. Therefore, the efficiency of the wafer process can be further improved.

Note that the subsequent steps are the same as in the first embodiment, and a description thereof will be omitted.

Although the invention made by the inventor has been specifically described based on the embodiment, the present invention is not limited to the embodiment, and it is needless to say that various modifications can be made without departing from the gist of the invention. .

In the above description, mainly the case where the invention made by the inventor is applied to a method of manufacturing a semiconductor device mounted with a pellet as a so-called ROM element, which is a field of use, has been described, but the present invention is not limited to this. ,
The present invention can be widely applied to other elements that require a window opening on a bonding pad, such as a RAM or another memory element or a logic element.

〔The invention's effect〕

The effect obtained by the representative one of the inventions disclosed in the present application will be briefly described as follows.

In other words, even when it is necessary to use a photoresist material having a different resist polarity between the upper layer and the lower layer,
In one exposure step using a photomask, the upper layer and the lower layer can be continuously etched, so that the efficiency of a wafer process in the manufacture of a semiconductor device can be increased.

Further, since only one photomask process is required, it is not necessary to consider a positional shift caused by a plurality of times of alignment for each mask, and the etching edges of the upper layer and the lower layer can be matched. Therefore, for example, when the upper layer functions as a protective film of a synthetic resin, it is possible to reliably protect the lower insulating film and the like.

In addition, the edges of the inner walls of the opening of the bonding window coincide with each other, and the upper surface of the insulating film around the bonding pad is almost completely covered with the protective film. It is possible to effectively prevent the breakdown of the underlying insulating film due to the elasticity of the substrate.

[Brief description of the drawings]

1 (a) to 1 (d) are explanatory cross-sectional views each showing a part of a wafer process according to an embodiment of the present invention, FIG. 1 (e) is a plan view of a bonding window, and FIG. FIG. 3 is a schematic cross-sectional view for explaining the structure of the semiconductor device obtained by the above embodiment; FIG. FIG. 5 is a partially enlarged view showing a state of forming a pellet on a wafer in the above embodiment, FIG. 5 is an explanatory sectional view showing a part of a wafer process which is another embodiment of the present invention, and FIGS. (E) is an explanatory sectional view showing a part of the wafer process in the conventional technique. DESCRIPTION OF SYMBOLS 1 ... Semiconductor device, 2 ... Semiconductor substrate, 2 ... Pellet, 3A ... N well layer, 3B ... P well layer, 4 ... Field oxide film, 5 ... Gate electrode, 6 ... Diffusion layer, 7 ...
... interlayer insulating film, 8 ... wiring layer, 10 ... bonding pad, 11 ... insulating film, 12 ... chelate film, 13 ... protective film,
14 ... bonding window, 15 ... resist material, 16 ... photomask, 17 ... light shielding pattern, 18 ... lead frame, 18 a ... inner lead, 18 b ... lead, 20 ... silver paste, 21 ... … Wire, 22 …… bonding ball,
23 ... resin, 24 ... dicing line, 61 ... semiconductor substrate, 62 ... bonding pad, 63 ... insulating film, 64
... Chelate film, 65 ... Protective film, 66 ... Bonding window, 67a ... Resist material (negative), 67b ... Resist material (positive), 68a, 68b ... Photomask, 70a, 70b ... Light shielding pattern.

Continuation of the front page (56) References JP-A-59-229829 (JP, A) JP-A-60-15948 (JP, A) JP-A-63-37640 (JP, A) JP-A-1-166527 (JP) JP-A-63-86550 (JP, A) JP-A-63-299253 (JP, A)

Claims (2)

(57) [Claims] An insulating film covering a bonding pad on a semiconductor substrate and a protective film made of a polyimide-based synthetic resin covering the insulating film are etched to form a bonding window directly above the bonding pad. At this time, by leaving the photoresist material formed on the protective film as it is, a laminated protective mask is formed with the photoresist material and the remaining portion of the protective film, and then the laminated protective mask is formed using the laminated protective mask. By etching the insulating film, the bonding window in which the edge line of the opening portion coincides is opened to expose the bonding pad, and a wire is bonded to the exposed bonding pad by ultrasonic combined bonding, and thereafter, A method for manufacturing a semiconductor device, comprising resin sealing. 2. A method according to claim 1, wherein said photoresist material is a negative resist.