JPS60247931A - Method for treatment of photosensitive heat-resisting insulating film - Google Patents

Abstract

PURPOSE:To manufacture a reliable semiconductor device by a method wherein, in the heat treatment process to be performed after patternization of a photosensitive polyimide film, the condition of heat treatment when the film is brough into a polyimide state is optimized. CONSTITUTION:After an insulating film 3 and an aluminum wiring 5 have been formed on the surface of the substrate 1 whereon a semiconductor element is formed, a photosensitive polyimide film 6 is coated on the whole surface. Then, after the polyimide film 6 has been selectively exposed and developed, a polyimide film 9 which is patternized and hardened by heat treatment is formed. In the above-mentioned heat treatment, the temperature and the time of the final heat treatment are set at the optimum value corresponding to the degree of the required heat resistivity. As a result, the heat-resisting property of the polyimide film and the electric characteristics of the semiconductor device using the polyimide film can be excellently harmonized, thereby enabling to obtain the semiconductor device of high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat treatment technique after patterning a photosensitive heat-resistant insulating film, particularly a photosensitive polyimide.

[Background technology]

In recent years, polyimide resins have been attracting attention as protective films for transistors, ICs, and LSIs, as well as insulating films between multilayer interconnections.

In addition to its excellent heat resistance, polyimide resin has many advantages such as easier flattening than inorganic insulating film materials such as silicon oxide and nitride, and high product yield and reliability. has advantages.

These polyimide resins are also being developed as photosensitive heat-resistant materials that have both the functions of photoresists and insulating films, with the aim of streamlining the conventional multilayer wiring interlayer insulating film formation process, and the results have been announced one after another. has been done. ((
b) Hiraki, Ero: Photosensitive heat-resistant insulation, electronic materials 1981
November 2013 P47゜←) Indenters, rice grains, etc.: Fine pattern formation method using photosensitive polyimide, electronic materials July 1983 P,
30) Photosensitive polyimide, which is a photosensitive heat-resistant insulating film developed by the applicant, is a highly pure photosensitive polymer composition in which a photosensitive group such as bisazide is bonded to a wholly aromatic polyimide precursor. It includes. The sensitivity of this photosensitive polyimide is equivalent to or higher than that of high-sensitivity rubber-based photoresists for LSIs, excellent resolution, and its heat resistance and electrical and mechanical properties are equivalent to or higher than polyimide resins currently used for LSIs. (Electronic materials July 1983, p. 30)
.

To form a patterned polyimide film using this photosensitive polyimide, the face is coated with a spinner, prebaked at 80°C for 20 minutes, and then selectively exposed and developed in the same manner as conventional photoresists. After patterning, 200'C, 30 minutes and 35
A hardened polyimide film was formed by heat treatment at 0°G for 60 minutes.

According to studies conducted by the present inventors, it has been found that the heat resistance of polyimide films obtained by heat-treating photosensitive polyimide varies significantly depending on the heat-treating conditions (temperature: 0 hours). In the case of polyimide, which has traditionally been used as a heat-resistant insulating material, when forming a polyimide film by heat treatment from the face state,
If the heat treatment is performed at a temperature of 350'C or higher, the heat resistance of the polyimide film after the heat treatment will hardly change.

Therefore, when using a polyimide film obtained by heat-treating photosensitive polyimide, the temperature is obviously high.

Long-term heat treatment is preferred. However, depending on the device to which photosensitive polyimide is applied, such as a semiconductor device, the characteristics of the device (for example, voltage resistance characteristics) depend on the final heat treatment conditions.
may change or deteriorate.

For the above reasons, when photosensitive polyimide is used, heat treatment conditions cannot be easily determined as in the case of forming conventionally used polyimide films. The heat treatment conditions for the photosensitive polyimide must be such that the combination of the heat resistance of the obtained polyimide film and the heat resistance of the device using the same is well balanced.

In other words, the heat resistance of a polyimide film using photosensitive polyimide depends on the heat treatment conditions during polyimidation (curing), and in order to improve the heat resistance, high temperature,
Long-term heat treatment is recommended. However, if the high-temperature, long-term treatment becomes excessive, two contradictory results will occur: the electrical and mechanical properties of the semiconductor element, which is the main body of the product to which it is applied, will deteriorate.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and its purpose is to harmonize the above two contradictory trends, optimize heat treatment conditions during polyimidization of photosensitive polyimide,
The purpose of this invention is to provide a heat treatment technology for photosensitive polyimide that can produce the most reliable products (semiconductor devices).

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, after selectively exposing and developing a photosensitive polyimide film coated on a substrate, heat treatment is performed to form a desired patterned and hardened polyimide film. The optimum temperature and time for the final heat treatment of the photosensitive polyimide are selected depending on the degree of heat treatment.
When using a photosensitive polyimide containing a photosensitive polymer composition in which a bisazide photocrosslinking agent is bonded to a bisazide photocrosslinking agent, and the patterned polyimide film requires a heat resistance of about 450'c, final heat treatment is required. 60 at 400-430℃
If the heat resistance requires 470°C, the final heat treatment temperature is 4306°C to 450°C for about 60 minutes, so that the required heat resistance can be obtained depending on the product and the heat resistance can ensure the characteristics of the product. An insulating film is obtained and the above object can be achieved.

[Example 1] FIG. 1 (1/2) is a chart showing the process of forming a polyimide film for a resin-sealed semiconductor device according to the present invention, and FIGS. 2 to 7 are (a) to (a) of FIG. It is a process sectional view corresponding to f).

Hereinafter, each step will be explained in detail.

(a) P′″ type diffusion in a part of the semiconductor (Si) substrate 1;
? By selectively performing type diffusion, a semiconductor element 2 with a busy transistor thickness is formed as shown in FIG. 2, and an insulating film (S
A contact hole 4 for outputting electrical signals to the outside of the device is formed by photo-etching a part of the iO, ) 3.

(b) Aluminum (Ad) is vapor deposited and the Al film is patterned by photo-etching to form an Al electrode (distribution@) 5 as shown in FIG.

(c) As shown in FIG. 4, a photosensitive polyimide film 6 is formed to cover the entire surface.

When forming the photosensitive film 6, this photosensitive polyurethane is 470
Heat treatment is performed for 15 minutes at ℃ to make the contact resistance at the contact hole (4mm) sufficiently low.After this, the resin concentration in the face is reduced to 1
A photosensitive polyimide powder having a viscosity of 4% by weight and a viscosity of 30 poise is applied using a spinner for 30 seconds at a rotational speed of 3000 γPm.

Polyamic acid is used as this photosensitive polyimide.

In a photosensitive polymer composition comprising a bisazide photocrosslinking agent, an amine compound having a carbon-carbon double bond, and a compound containing one or more hydroxyl groups in the molecule and having a boiling point of 150°C or higher at normal pressure, polyamide A photosensitive polymer composition using a polyamic acid whose acid structure is represented by a repeating unit of the general formula (where R' represents a divalent aromatic ring-containing organic group or a silicon-containing organic group) is used. do. After spinner application, 80℃
Pre-bake for 20 minutes.

At this time, the film thickness of the photosensitive polyimide is about 4.5 μm.

(d) After this, as shown in FIG.
Exposure is performed using nanometer ultraviolet light.

The appropriate photosensitive energy is 100 mJ/ctd, but considering pattern processing accuracy, etc., the range of 20 to 200 m
J/CRD You can choose from a range of 6.

(e) After exposure, add a developer having a composition of NMP (n-methylpyrrolidone):water = 4:1 (volume ratio) at 25°C.
, immerse for 10 minutes and develop. At this time, the film thickness of the photosensitive polyimide is about 4 μm. By this development, the unexposed portion of the photosensitive polyimide film is dissolved and removed, and a through hole 8 is opened so that a portion of one wiring 5 is exposed, as shown in FIG. After that, the residue of the unexposed polyimide area is removed using a cleaning solution.

(f) After this, 30 minutes at 200℃ and 30 minutes at 400℃
A heat treatment is performed for 30 minutes to form a polyimide film 9 having a heat resistance of 410° C. as shown in FIG. This 410℃
is a temperature that can withstand the processing temperature during resin molding.

(g) Next, scribe (or dice) the semiconductor substrate in wafer form to individually form ICs (or LSIs).
Divide into chips (berrets) containing. Figure 8(a)~
(e) is Char) N of the process of assembling the pelletized semiconductor substrate into a lead frame and sealing it with a resin mold. 9 to 11 are process cross-sectional views corresponding to FIG. 8, and FIG. 12 is a perspective view showing the completed form.

(&) For pellet attachment, a lead frame is prepared in which a tab 10 and a plurality of adhesives 11 are integrally formed on one metal plate.

(b) Using a pellet ponder, the chip 12 having a heat-cured polyimide film is attached to the tab 1 of the lead frame.
The chip 12 is bonded onto the lead frame with silver paste or the like, and heat treated at 180° C. for 90 minutes, as shown in FIG. 9, to fix the chip 12 to the lead frame.

(c) Heat the lead frame and chip to 200'C and use ultrasonic thermocompression bonding to form terminals (bonding pads) for each wiring on the chip 12 using gold (Au) wires as shown in Figure 10. A wire 13 for electrical continuity is provided between the lead 11 and the peripheral lead 11.

(d) Using an epoxy resin, transfer molding is performed at 180° C., and the semiconductor chip is sealed with a resin body 14 as shown in FIG.

(e) Finally, the leads are separated on the outside of the resin body 14 to complete the resin-sealed conductor packaging as shown in FIG.

〔effect〕

Figure 18 shows the relationship between the heat treatment conditions of photosensitive polyimide by the present inventor and the heat resistance of the polyimide film obtained by this heat treatment (temperature at which weight loss is 1% by constant rate temperature increase method). .

For example, the final heat treatment condition at 400°C for 30 minutes is 410°C.
℃ heat resistance (point C in the figure), but at 400℃ for 60 minutes it was 4.
It has a heat resistance of 40°C (point E in the figure), and after heat treatment at 430°C for 30 minutes, it has a heat resistance of 445°C (point E in the figure).

The maximum heat resistance temperature obtained from the photosensitive polyimide used in the present invention is 490'C, and no matter how the heat treatment conditions are devised, higher heat resistance cannot be obtained. This temperature corresponds to the thermal decomposition temperature of the pace polymer used in the photosensitive polyimide.

In the process of the present invention described in the examples, the maximum temperature applied after the final heat treatment of the photosensitive polyimide film is about 200°C, and a polyimide film having a heat resistance of 410°C can sufficiently fulfill its role.

In this step, in order to increase the heat resistance of the photosensitive polyimide as much as possible, a final heat treatment at 450°C for 60 minutes is performed to prevent the reaction between the N-type S 1 (2) and the Al electrode (5) in the contact hole (6). As the process progresses, the characteristics deteriorate.

Therefore, in this step, the heat treatment temperature is preferably as low as possible from the viewpoint of the characteristics of the element, and the heat treatment temperature is preferably as high as possible from the viewpoint of the heat resistance of the polyimide. Considering the balance between the two, it can be seen that the final heat treatment condition of 400° C. for 30 minutes is the most preferable in this process.

[Embodiment 2] As another embodiment of the present invention, the present invention may be applied to a glass-sealed product in which, for example, a semiconductor chip is sealed in a ceramic package using low-melting glass.

In this case, the steps of confectionery formation by selective impurity diffusion, aluminum wiring formation, photosensitive polyimide face coating, and exposure/development at the semiconductor substrate (wafer) stage are described in steps (a) to (e) of Example 1. This is the same as the case shown in Figures 1 to 6. However, the heat treatment process after development and the subsequent package introduction process differ as follows. That is, in the heat treatment steps shown in FIG. 1(f) and FIG. 7, the final heat treatment conditions for the photosensitive polyimide are 43
0℃.

9. Heat treatment for 60 minutes or 450°C for 30 minutes
3(&) to (e) are chart diagrams of the process of sealing the pelletized semiconductor chip into a ceramic package. 14 to 16 are process cross-sectional views corresponding to FIG. 13, and FIG. 17 is a perspective view showing the completed form.

(a) As shown in Fig. 14, prepare a ceramic package 17 that has an opening at the top, is electrically connected between the inside and outside by metallized wiring 15, and has leads 16 attached to the outside of the wiring. (b) Ceramic package The six semiconductor chips 18 formed into chips inside are connected using HG paste or the like.

(c) As shown in FIG. 15, wires 19 are used to connect the wiring terminals of the chip and the metallized wiring of the package.

(d) As shown in FIG. 16, there is a lid $20t-1 made of metal or 72ξ on the top of the package 17! : Sealing is performed at 470° C. using low melting glass 21.

(e) FIG. 17 shows the external form of a ceramic package containing a semiconductor chip and sealed with glass.

〔effect〕

When the present invention is applied to a glass-sealed product as in Example 2, the glass-sealing temperature must be 470°C, and in this case, the reaction between the AI electrode and 81 in the contact hole is A! By using Al-2% 81 alloy as the electrode and heat-treating the photosensitive polyimide for 60 minutes at 430°C or 30 minutes at 450°C (see Figure 18), polyimide that can withstand the glass sealing temperature can be obtained. A film can be formed. In the former case, pure AJ was used as the M electrode, and in the latter case, an Al-2% Si alloy was used. For the former, there is a question as to whether it would be better to use an A12%81 alloy film, but pure AA and AJ-2%S1 alloy films have poor electrical properties (e.g., high sheet key barrier) for Si substrates. However, it is not possible to obtain good characteristics as an IC, and depending on the product, pure Al electrodes have no choice but to be used.

[Application field]

The present invention can be used in general semiconductor devices (transistors, ICs) that use polyimide films for passivation.

[Brief explanation of the drawing]

FIG. 1→M is a chart of the manufacturing process of a semiconductor device having a polyimide film, and FIGS. 2 to 7 are process cross-sectional views corresponding to FIG. 1, showing an embodiment of the present invention. be. Fig. 8 is a chart showing an example of the assembly process of a semiconductor device, Figs. 9 to 11 are process sectional views corresponding to Fig. 8, and Fig. 12 is a perspective view showing the completed state. be. Figure 13 is a chart showing another example of the assembly process of a semiconductor device, Figures 14 to 16 are process sectional views corresponding to Figure 13, and Figure 17 is a perspective view showing the completed state. Figure 18 is a relationship curve diagram showing the heat resistance of photosensitive polyimide and heat treatment time. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Semiconductor element, 3... Oxide film, 4... Contact hole, 5... Aluminum wiring, 6... Photosensitive polyimide film, 7... Mask, 8
...Through hole, 9...Polyimide film. !・Pa Figure 1 Figure 2 Figure 8 Figure 18 Jindaigin F, i'l (button

Claims (1)

[Scope of Claims] 1. When a photosensitive heat-resistant insulating film coated on a substrate is selectively exposed to light, developed, and then heat-treated to form a heat-resistant insulating film of a predetermined shape, the heat-resistant insulating film requires the following: A method for processing a photosensitive heat-resistant insulating film, comprising selecting an optimal treatment temperature and time in the final heat treatment stage of the photosensitive heat-resistant insulating film according to the degree of heat resistance. 2. The photosensitive heat-resistant insulating film contains a photosensitive polymer composition in which a bisazide photocrosslinking agent is bonded to a wholly aromatic polyimide precursor, and the heat resistance of the polyimide film in the desired shape is approximately 450°C. In some cases, final heat treatment is performed at 400-430℃.
The method of treating a photosensitive heat-resistant insulating film according to claim 1, wherein the final heat treatment is carried out at 430 to 450°C for about 60 minutes when the heat resistance is about 470°C or higher. 3. The photosensitive polymer composition is a polyamic acid, a bisazide photocrosslinking agent, an amine compound having a carbon-carbon double bond, and a compound containing one or more hydroxyl groups in the molecule and having a boiling point of 150°C or higher at normal pressure. A photosensitive polymer composition comprising a polyamic acid whose structure is represented by a repeating unit of the general formula: (wherein R' represents a divalent aromatic ring-containing organic group or a silicon-containing organic group) A method for treating a photosensitive heat-resistant insulating film according to claim 2, using the method.