JP2001223210A - Method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a buffer coating film from wearing off and its surface from being damaged in a dry etching process in which the buffer coating film is used as a mask. SOLUTION: An insulating film 3, a metal wiring 5, a PSG film 7, and a positive photosensitive polybenzoxazole precursor 11 are sequentially formed (A), and furthermore a positive photosensitive resist 15 which can be developed with a developing solution common to the precursor 11 is formed thereon (B). The resist 15 and the precursor 11 are exposed to light for the formation of photodissociated regions 11b and 15b (C), the photodissociated regions 11b and 15b are removed by the use of a developing solution to form openings 11a and 15a (D), a silicon nitride film 9 is patterned through a dry etching method for the formation of an opening 9a, and the resist 15 is removed (E). The precursor 11 is cured into a polybenzoxazole film 11c, and then the PSG film 7 is patterned to form an opening 7a (F).

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 semiconductor device, and more particularly, to a method for forming a buffer coat film or a polybenzoxazole film or a polyimide film or both used as an interlayer insulating film formed further above a surface protective film. And a method for manufacturing a semiconductor device including the same.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have been mounted on a printed circuit board with high density, the thickness of semiconductor packages has been reduced, and the area ratio of semiconductor chips to semiconductor packages has been increasing remarkably. For this reason, there has been a problem that the semiconductor chip is directly susceptible to external thermal or mechanical stress, or the wiring is corroded due to the intrusion of moisture, which causes a decrease in the performance and reliability of the element. .
As a countermeasure, buffer coating is used to reduce the stress applied from the outside, protect the chip from silica (also called filler) in the sealing resin, and further improve the adhesion between the surface protective film and the sealing resin. Polybenzoxazole films and polyimide films, which are called films, have come to be widely used.

A case in which a buffer coat film is formed on a semiconductor substrate after a surface protective film has been formed will be described. The material of the buffer coat film is photosensitive and non-photosensitive, and there is a negative type and a positive type in the photosensitivity. Here, the material of the negative photosensitive buffer coat film will be described. FIG.
FIG. 4 is a process cross-sectional view showing a conventional manufacturing method including a process of opening a surface of an electrode pad by etching a surface protective film using a negative photosensitive buffer coat film material as a mask.

(A) An insulating film 3 is formed on a silicon substrate 1, and a metal wiring 5 is further formed thereon. Insulating film 3
On the upper surface and on the metal wiring 5, P
An SG film 7 is formed, and a silicon nitride film 9 constituting an upper layer of the surface protection film is further formed thereon. A negative photosensitive buffer coat film material 10 is applied on the silicon nitride film 9 by spin coating. (B) The negative photosensitive buffer coat film material 10 is exposed to light through the mask 12 and the remaining region of the negative photosensitive buffer coat film material 10 is photocrosslinked to form a photocrosslinked buffer coat film region 10b. .

(C) Using a developing solution to open the negative photosensitive buffer coat film material 10 on the electrode pad of the metal wiring 5, the negative photosensitive buffer coat film material 10 in a region not photocrosslinked is used. Is removed to form an opening 10a. Thereafter, a heat treatment is performed to cure the photo-crosslinking buffer coat film region 10b to form the buffer coat film 10c.
And (D) Using the buffer coat film 10c as a mask, the silicon nitride film 9 is etched by a dry etching method to form an opening 9a corresponding to the opening 11a. (E) Buffer coat film 10c and silicon nitride film 9
Is used as a mask, the PSG film 7 is etched by a dry etching method, an opening 7a is formed in accordance with the opening 11a and the opening 9a, and an opening is formed on the electrode pad of the metal wiring 5.

[0006]

In the conventional manufacturing method shown in FIG. 1, the silicon nitride film 9 is formed by using the photocrosslinking buffer coat film region 10b serving as the buffer coat film 10c as a mask.
In the step (D) of patterning the silicon nitride film 9 by dry etching, the etching rate of the photocrosslinking buffer coat film region 10b under the dry etching conditions for the silicon nitride film 9 is high. Membrane 1
There has been a problem that the performance and reliability of the device are reduced due to the thin film thickness of 0c or the formation of a damaged layer on the surface. The same problem as described above occurs when a positive photosensitive polybenzoxazole precursor or a positive photosensitive polyimide precursor is used as the material of the buffer coat film. An object of the present invention is to solve such a problem and to prevent the buffer coat film from being thinned and from being damaged during dry etching using the buffer coat film as a mask.

[0007]

The present invention is a method of manufacturing a semiconductor device including the following steps (A) to (F). (A) A positive-type photosensitive polybenzoxazole precursor or a positive-type photosensitive polybenzoxazole which can be developed on a surface protective film formed on a semiconductor substrate with a common developing solution with a positive-type photosensitive resist formed in a later step (C). A step of forming a photosensitive polyimide precursor, (B) a step of heating under conditions that do not impair the photosensitivity of the solvent of the positive photosensitive polybenzoxazole precursor or the positive photosensitive polyimide precursor, and (C) a positive photosensitive Forming a positive photosensitive resist on the conductive polybenzoxazole precursor or the positive photosensitive polyimide precursor,
(D) a step of simultaneously exposing a positive photosensitive polybenzoxazole precursor or a positive photosensitive polyimide precursor and a positive photosensitive resist and further developing them simultaneously to perform patterning simultaneously; Polybenzoxazole precursor or positive photosensitive polyimide precursor, and a step of patterning the surface protective film by etching using a positive photosensitive resist as a mask,
(F) a heating step of curing the positive photosensitive polybenzoxazole precursor or the positive photosensitive polyimide precursor to form a polybenzoxazole film or a polyimide film.

A positive-type photosensitive polybenzoxazole precursor or a positive-type photosensitive polyimide precursor (referred to as a buffer coat film precursor), which is to be a buffer coat film, is coated on the surface protective film, and the positive-type photosensitive film is further coated thereon. Apply a resist. Since the buffer coat film precursor and the positive photosensitive resist are selected so that they can be developed with a common developer, the buffer coat film precursor and the positive photosensitive resist must be simultaneously exposed and further developed at the same time. Can be. Thereby, patterning can be performed simultaneously, and the surface protective film is patterned by etching using the pattern as a mask. At this time, since the positive photosensitive resist is present on the buffer coat film precursor, it is possible to prevent the buffer coat film precursor, and eventually the buffer coat film, from being reduced in thickness and damaged. Thereafter, the buffer coat film precursor is cured to form a buffer coat film (polybenzoxazole film or polyimide film).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION It is preferable that the positive photosensitive resist is formed so as to have a thickness completely eliminated by the etching treatment on the surface protective film in the step (E).
It is more preferable that the film is formed to have a film thickness that just disappears. As a result, an ashing step for removing the positive photosensitive resist remaining after the etching treatment on the surface protective film can be omitted.

[0010] The surface protective film comprises a laminated film of two or more layers,
The etching treatment on the surface protective film in the step (E) leaves at least one layer of the surface protective film, and preferably further includes, after the step (F), a step of removing the remaining layer of the surface protective film. . As a result, the electrode pad is covered with the remaining layer of the surface protective film during the heat treatment for curing the buffer coat film precursor in the step (F), so that the contamination of the electrode pad surface can be prevented. .

[0011]

FIG. 2 is a process sectional view showing one embodiment.
Here, as a buffer coat film precursor, an etching solution common to the positive type photosensitive resist, for example, TMAH is used.
A positive photosensitive polybenzoxazole precursor which can be resolved with a 38% aqueous alkali developer was used. (A) An insulating film 3 is formed on a single-crystal silicon substrate 1 having a diameter of 6 inches, and a metal wiring 5 is formed in a predetermined region thereon. A PSG film 7 constituting a lower layer of a surface protection film is formed on the insulating film 3 and the metal wiring 5 by a plasma CVD method.
Is deposited in a film thickness of 0.2 to 0.6 μm. PSG film 7
Alternatively, a silicon oxide film may be used. Further thereon, a silicon nitride film 9 constituting an upper layer of the surface protection film is deposited to a thickness of 0.7 to 1.2 μm by a plasma CVD method.

While rotating the silicon substrate 1 at a low speed of 100 to 300 rpm, about 3 cc of a positive photosensitive polybenzoxazole precursor 11 is dropped. Thereafter, the rotation speed of the silicon substrate 1 is set to 800 rpm, 1600 to 4000 r.
The positive-type photosensitive polybenzoxazole precursor 11 is applied in a predetermined film thickness by increasing the rotation speed stepwise to pm. As the positive photosensitive polybenzoxazole precursor 11, CRC-8300 (a product of Sumitomo Bakelite Co., Ltd.) was used. Next, 110-13 on a hot plate
Heat treatment is performed at a temperature of 0 ° C. for about 3 to 5 minutes.
This is a positive photosensitive polybenzoxazole precursor 1
Part of the solvent in the positive photosensitive polybenzoxazole precursor 11 is volatilized to such an extent that the photosensitivity of No. 1 is not impaired,
This is performed for the purpose of improving the adhesion in the subsequent development step.

(B) The silicon substrate 1 is
While rotating at a rotation speed of 00 rpm, 2 to 3 cc of the positive photosensitive resist 15 is dropped on the positive photosensitive polybenzoxazole precursor 11. Then, the silicon substrate 1
Is increased to 2000 to 4000 rpm, and the positive photosensitive resist 15 is applied with a predetermined film thickness. afterwards,
A heat treatment is performed on a hot plate at a temperature of 90 ° C. for about 1 minute. As the positive photosensitive resist 15, O
FPR5000 S-3 50 cp (product of Tokyo Ohka Kogyo Co., Ltd.) was used. Here, in the dry etching process for the silicon nitride film 9 described later, the selectivity ratio of the silicon nitride film 9 / positive photosensitive resist 15 is 1.5 to 2
Therefore, the film thickness of the positive photosensitive resist 15 is
The setting is made so that the silicon nitride film 9 is completely removed by the etching process.

(C) The mask 13 is formed by photolithography.
To expose the positive-type photosensitive resist 15 and the positive-type photosensitive polybenzoxazole precursor 11 to photo-dissociate the positive-type photosensitive resist and the positive-type photosensitive polyimide precursor in the region to be removed. The regions 11b and 15b are formed. (D) In order to open the electrode pad of the metal wiring 5, TM
The photodissociation region 11b is formed by spray development or paddle development using an aqueous alkali developer containing 2.38% of AH.
15b is removed to form openings 11a and 15a.

(E) 110-130 on a hot plate
A heat treatment is performed at a temperature of about 1.5 ° C. for about 1.5 to 2 minutes. This is performed for the purpose of volatilizing a part of the solvent in the positive photosensitive resist 15 and preventing the positive photosensitive resist 15 from being scorched in a later dry etching process.
Using the positive-type photosensitive resist 15 and the positive-type photosensitive polybenzoxazole precursor 11 as a mask, the silicon nitride film 9 is patterned by a dry etching method, and an opening 9a is formed in accordance with the openings 11a and 15a. At this time, in step (B), the thickness of the positive photosensitive resist 15 is controlled so as not to be subjected to the dry etching process on the silicon nitride film 9.
5 is just gone.

(F) The positive photosensitive polybenzoxazole precursor 11 is subjected to a heat treatment at a temperature of 150 ° C. for about 30 minutes in a nitrogen atmosphere having an oxygen concentration of 100 ppm or less, and further, at a temperature of 300 to 350 ° C. 3 at temperature condition
A heat treatment for about 0 minutes is performed. At this time, the metal wiring 5
Since the electrode pad is covered with the PSG film 7, it is possible to prevent the electrode pad surface from being contaminated. By this heat treatment, the solvent and the photosensitive group in the positive photosensitive polybenzoxazole precursor 11 are removed, the ring-closing reaction of the benzoxazole ring is completed, and the positive photosensitive polybenzoxazole precursor 11 is cured. The polybenzoxazole film 11c is formed. When a positive photosensitive polyimide precursor is used as the buffer coat film precursor in place of the positive photosensitive polybenzoxazole precursor 11, the imide ring-closing reaction is completed and the positive photosensitive The conductive polyimide precursor is cured, and the polyimide film 11c is formed. Using the polybenzoxazole film 11c and the silicon nitride film 9 as a mask, the PSG film 7 is patterned by a dry etching method, and openings 7a are formed in accordance with the openings 9a, 11a, and 15a. Open the top.

In this embodiment, PGS is used as a surface protection film.
Although a two-layer laminated film of the film 7 and the silicon nitride film 9 is used, the present invention is not limited to this, and a laminated film of three or more layers may be used.

[0018]

According to the first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising a step of forming a positive resist on a surface protective film formed on a semiconductor substrate by using a common developing solution with a positive photosensitive resist formed in a later step. Applying a photosensitive photosensitive polybenzoxazole precursor or a positive photosensitive polyimide precursor, heating under conditions that do not impair the photosensitivity of the solvent of the positive photosensitive polybenzoxazole precursor or the positive photosensitive polyimide precursor, A positive photosensitive resist is formed on a positive photosensitive polybenzoxazole precursor or a positive photosensitive polyimide precursor, and a positive photosensitive polybenzoxazole precursor or a positive photosensitive polyimide precursor, and a positive photosensitive resist are formed. Simultaneously exposing the photosensitive resist and developing it at the same time, patterning at the same time, the positive photosensitive polybenzoxazole precursor Or a positive photosensitive polyimide precursor, and patterning the surface protective film by etching using a positive photosensitive resist as a mask, and curing the positive photosensitive polybenzoxazole precursor or the positive photosensitive polyimide precursor Since a polybenzoxazole film or a polyimide film is formed, when a surface protective film is patterned by etching, a positive photosensitive resist is present on the buffer coat film precursor, and the buffer coat film is reduced in film thickness and surface. Damage can be prevented.

In the method of manufacturing a semiconductor device according to the second aspect of the present invention, in the step of applying the positive type photosensitive resist, the positive type photosensitive resist is applied to a thickness which is completely eliminated by the etching treatment on the surface protective film. An ashing step for removing the positive photosensitive resist remaining after patterning the surface protective film can be omitted.

According to a third aspect of the present invention, the surface protective film is formed of a laminated film of two or more layers, and the surface protective film is etched by at least one of the surface protective films.
After the positive photosensitive polybenzoxazole precursor or the positive photosensitive polyimide precursor is cured to form a polybenzoxazole film or a polyimide film, the remaining layer of the surface protective film is removed. Since the method further includes a step, in the heat treatment for curing the positive photosensitive polybenzoxazole precursor or the positive photosensitive polyimide precursor, it is possible to prevent contamination of the electrode pad surface under the surface protective film. it can.

[Brief description of the drawings]

FIG. 1 is a process cross-sectional view showing a conventional manufacturing method including a step of opening a surface of an electrode pad by etching a surface protective film using a negative photosensitive buffer coat film material as a mask.

FIG. 2 is a process sectional view showing one embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single crystal silicon substrate 3 Insulating film 5 Metal wiring 7 PSG film 7a, 9a, 11a, 15a Opening 9 Silicon nitride film 11 Positive photosensitive polybenzoxazole precursor 11b, 15b Photodissociation area 11c Polybenzoxazole film 13 Mask 15 Positive photosensitive resist

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H025 AA02 AA09 AA11 AA13 AA20 AB17 AB20 AC01 AD03 BE01 CB25 CB26 DA11 FA01 FA29 FA41 FA44 5F046 NA05 NA17 5F058 AA10 AC02 AC07 AC10 AD04 AD09 AF04 AG01 AH01 AH02

Claims (3)

[Claims] 1. A method of manufacturing a semiconductor device comprising the following steps (A) to (F). (A) A positive-type photosensitive polybenzoxazole precursor or a positive-type photosensitive polybenzoxazole which can be developed on a surface protective film formed on a semiconductor substrate with a common developing solution with a positive-type photosensitive resist formed in a later step (C). A step of forming a photosensitive polyimide precursor, (B) a step of heating under conditions that do not impair the photosensitivity of the solvent of the positive photosensitive polybenzoxazole precursor or the positive photosensitive polyimide precursor, and (C) the step of: Forming a positive photosensitive resist on the positive photosensitive polybenzoxazole precursor or the positive photosensitive polyimide precursor, (D) the positive photosensitive polybenzoxazole precursor or the positive photosensitive A step of simultaneously exposing the polyimide precursor and the positive photosensitive resist and simultaneously developing the same to thereby perform patterning simultaneously; (E) the step of: Patterning the surface protective film by etching using the positive photosensitive polybenzoxazole precursor or the positive photosensitive polyimide precursor and the positive photosensitive resist as a mask, (F) the positive photosensitive A heating step of curing the polybenzoxazole precursor or the positive photosensitive polyimide precursor to form a polybenzoxazole film or a polyimide film; 2. The semiconductor according to claim 1, wherein in the step (C), the positive photosensitive resist is applied to a thickness that is completely eliminated by the etching treatment on the surface protective film in the step (D). Device manufacturing method. 3. The step of etching the surface protective film in the step (E), wherein the surface protective film comprises at least one layer of the surface protective film. 3. The method of manufacturing a semiconductor device according to claim 1, further comprising: after (F), removing a remaining layer of the surface protective film. 4.