JP2785752B2 - Method for manufacturing semiconductor device - Google Patents

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 polyimide buffer coat on an integrated circuit having a semiconductor element such as an EPROM which requires light transmittance.

[0002]

2. Description of the Related Art As a prior art of this kind, FIGS. 6 and 7 show a patterning method for wet polyimide which is currently most frequently used. FIGS. 6 and 7 show EP
A method of patterning a polyimide in a semiconductor integrated circuit having a ROM (Electrically Programmable ROM; a PROM capable of electrically writing stored contents and erasing by ultraviolet rays) by wet polyimide is illustrated in the order of steps.

[0003] P-SiON8 as a passivation film
Integrated circuit board with built-in EPROM (see FIG. 6)
(A), a polyimide precursor 9 is spin-coated, the solvent is removed by baking at 120 ° C. for 2 minutes on a hot plate to form a layer having a coating thickness of about 10 μm, and then a positive photoresist (“ A positive resist 10) is spin-coated so as to have a coating thickness of about 2 μm and dried (see FIG. 6B).

Next, after the EPROM portion is exposed using a photomask for opening the EPROM portion, that is, the EPROM portion is exposed, 2.38% TMA which is a developing solution of a positive resist is used.
The positive resist 10 is developed with H ((CH ₃ ) ₄ NOH), and the underlying polyimide precursor 9 is subsequently etched with TMAH.

At this time, polyimide residue (also referred to as “residue”) due to insufficient penetration of the developing solution in the opening, that is, in the narrow space between the wirings of the EPROM portion.
11 occurs (see FIG. 7C).

Next, butyl acetate is dropped and a positive resist 10
Was removed, followed by 350 from room temperature this substrate in an N ₂ atmosphere
Heat treatment for the imidization reaction is performed while slowly raising the temperature to ° C. to form the polyimide resin 12. The polyimide remains as it is between the openings (FIG. 7D).
reference).

Another conventional example is disclosed in, for example, Japanese Patent Laid-Open No. 4-43641.
In the publication, a polyimide residue is generated in an opening (a punch pattern portion) during development of a photosensitive polyimide film.
In order to solve the problem of occurrence of bonding failure, contact failure, etc. during the subsequent assembling process, a photosensitive polyimide is applied to a semiconductor substrate on which an inorganic insulating film is formed, prebaked, and the photosensitive polyimide is exposed,
A method of manufacturing a semiconductor device has been proposed in which development and curing are performed, and a lower inorganic insulating film is etched using a photosensitive polyimide as a mask.

[0008]

In the processing method of polyimide according to the conventional example shown in FIGS. 6 and 7, there is no problem in processing a flat and large opening area pattern such as a bonding pad.

However, when a polyimide buffer coat is applied to an integrated circuit having a built-in EPROM, the polyimide that does not transmit ultraviolet rays must be removed from the EPROM.

At this time, according to the conventional example, the EPROM
In a space portion between the wirings having a narrow opening, a polyimide residue is generated, which is considered to be caused by insufficient penetration of the developing solution.

This is the main cause of EPROM erasure failure.

The polyimide residue has a film thickness of about 3,000 angstroms (= 300 nm), and no improvement is observed even when the developing time is lengthened.

Although it is possible to reduce the level of the polyimide residue by lowering the baking temperature after the application of the polyimide precursor resin, as a disadvantage, this causes cloudiness of the polyimide precursor and a reduction in pattern resolution. There are things.

The above-mentioned Japanese Patent Application Laid-Open No. 4-43641 discloses that the residue of the photosensitive polyimide is dry-etched with CF ₄ + O ₂ plasma.

In this case, a film thickness of 50 angstroms (= 5n
It is said that the polyimide residue of about m) is surely etched. However, when the polyimide residue has a film thickness of about 3000 Å, damage due to polyimide etching cannot be avoided because dry etching is performed using a photosensitive polyimide as a mask. Even recently, polyimide film with a thickness of 3,000 angstroms or more occurs. On the other hand, as will be described later, in the present invention, since the etching is performed using the positive resist as a mask, the polyimide is hardly damaged.

That is, the present invention solves the above problems,
An object of the present invention is to provide a method of manufacturing a semiconductor device in which an ultraviolet erasure failure due to a polyimide residue is eliminated in patterning of an integrated circuit with a built-in EPROM using a polyimide positive resist developer to which a polyimide buffer coat is applied.

[0017]

In order to achieve the above object, the present invention provides: (a) a step of applying a polyimide precursor on a passivation film on a semiconductor substrate; and b) a photoresist on the polyimide precursor. A step of applying
(c) selectively exposing and developing the photoresist;
Selectively removing the photoresist; and (d)
Selectively removing the polyimide precursor using the selectively removed photoresist as a mask,
(E) a step of the polyimide precursor to the polyimide resin by heat treatment, (f) a step of dry etching at least the photoresist across to residual film in O2 plasma, the photoresist was (g) residual film And a method for manufacturing a semiconductor device.

Further, the present invention provides (a) a step of applying a polyimide precursor on a passivation film on a semiconductor substrate; (b) a step of applying a photoresist on the polyimide precursor; Selectively exposing and developing a photoresist to selectively remove the photoresist; and (d) selectively removing the polyimide precursor using the selectively removed photoresist as a mask. (E) a step of converting the polyimide precursor into a polyimide resin by a heat treatment; and (f) a step of dry-etching the whole with a mixed gas plasma of O 2 and CF 4 so that the photoresist is entirely removed. A method of manufacturing a semiconductor device is provided.

In the present invention, preferably, the package
The passivation film is formed on relatively narrow wiring,
The wiring between the wirings that could not be removed in the step (d).
The polyimide residue on the passivation film is as described in (f) above.
It is characterized by being removed in the process .

[0020]

According to the present invention, in the patterning of a polyimide precursor with a positive resist developer, the resist is usually removed after patterning the polyimide precursor. By curing the body resin and removing the etching residue of the polyimide resin by oxygen plasma using a positive resist as a mask, the etching residue of the polyimide resin in the step portion is minimized while the damage of the oxygen plasma to the polyimide resin is minimized. Can be removed.

[0021]

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

[0022]

Embodiment 1 FIGS. 1A to 3F are cross-sectional views for explaining an embodiment of the present invention in the order of steps.

P-SiON8 as passivation film
Integrated circuit board with built-in EPROM (Fig. 1
(A)), a polyimide precursor 9 is spin-coated and baked on a hot plate at 120 ° C. for 2 minutes to remove a solvent component, thereby forming a layer having a coating thickness of about 10 μm. Subsequently, a positive photoresist (referred to as “positive resist”) 10 is spin-coated so as to have a coating thickness of about 2 μm and dried (see FIG. 1B).

Next, to open the EPROM portion, that is, after exposing the EPROM portion using a photomask to which the EPROM portion is exposed, 2.38% TM
Develop positive resist 10 with AH ((CH ₃ ) ₄ NOH)
Subsequently, the lower polyimide precursor 9 is etched with TMAH.

At this time, in the opening, that is, in the narrow space between the wirings of the EPROM section, polyimide residue 11 is generated, which is considered to be caused by insufficient penetration of the developing solution. The thickness is about 3000 Å (see FIG. 2C).

Next, heat treatment is performed with the positive resist 10 left. The heat treatment conditions are from room temperature to 250 in nitrogen atmosphere.
Heat to 10 ° C / min to 250 ° C and heat at 250 ° C for 30 minutes. At this stage, the polyimide precursor 9 becomes a polyimide resin 12 by an imidization reaction. Although the positive resist 10 is deformed and carbonized by heat, it does not reach a level where the masking property is deteriorated (see FIG. 2D).

Next, using a parallel plate type dry etching apparatus,
For example, O ₂ , 50 SCCM, pressure 200 mTorr, RF power: 800
When etching is performed under the condition of W and 3 minutes, the polyimide etching residue 11 is removed. The etching rate of the polyimide at this time is about 0.3 μm / min. The positive resist is also etched about 1.5 μm, but the remaining film is about 0.5 μm
m, the polyimide resin 12 in the lower layer is not damaged by the O ₂ plasma, so that no film thinning occurs (see FIG. 3E).

Subsequently, an organic resist stripper is used.
For example, 100 ° C 15
Then, the positive resist 10 is removed. Next, 350 ° C
Heat treatment is performed for 30 minutes with N ₂ to form a final shape (see FIG. 3F).

According to the above-described method of the present embodiment, since the polyimide etching residue can be completely removed, it is possible to completely eliminate the EPROM ultraviolet erasure failure caused by the polyimide residue.

[0030]

Embodiment 2 Next, a second embodiment of the present invention will be described. FIGS. 4A to 5E are cross-sectional views for explaining the manufacturing method of this embodiment in the order of steps.

In this embodiment, the case where the present invention is applied to the manufacture of a semiconductor integrated circuit incorporating a light receiving element (for example, a photodiode) is shown. In the light receiving element, if a polyimide resin having a low transmittance of light having a wavelength of 400 nm or less remains on the surface of the light receiving element, problems such as a decrease in light receiving sensitivity occur. The present embodiment is also effective in such a case.

First, P-Si is used as a passivation film.
A polyimide precursor 9 is spin-coated on an integrated circuit substrate with a built-in light receiving element formed up to the O film 13 and is heated at 120 ° C. 2 on a hot plate.
And a solvent component is removed to form a layer having a coating thickness of about 10 μm. Subsequently, when a positive photoresist is spin-coated so as to have a coating thickness of about 2 μm and dried, the result is as shown in FIG.

Next, exposure is performed by a G-line stepper using a photomask 14 in which a light receiving element portion and a pad portion are opened (see FIG. 4B).

Next, 2.38% of a positive resist developer
The positive resist 10 is developed with TMAH ((CH ₃ ) ₄ NOH), and then the lower layer polyimide precursor 9 is etched with TMAH.

At this time, the opening, that is, the light receiving element,
A polyimide etching residue 11 is generated in a narrow space between the wirings of the pad portion. The thickness is about 3000 angstroms (see FIG. 4C).

Next, heat treatment is performed while the positive resist 10 is left. The heat treatment conditions are the same as in the first embodiment. Then, O ₂ 80SCCM, CF ₄ 20SCCM, pressure 500mTorr, RF
Isotropic dry etching is performed under the condition of power of 300 W for 5 minutes.

At this time, the etching rate is about 0.5 μm / min together with the polyimide resin 12 and the positive resist 10.
P-SiO is hardly etched because it has no anisotropic etching component. The polyimide etching residue 11 in the light receiving element can be completely removed (see FIG. 5D).

The dry etching conditions are such that the resist is etched for 5 minutes at an etching rate of 0.5 μm / min, so that all the resist having a coating film thickness of 2.0 μm is removed.

According to the manufacturing method of this embodiment, although the lower polyimide resin 12 is also etched by about 0.5 μm, the step of removing the resist is not required, so that it is effective in a line without an organic resist removing agent.

Subsequently, at 350 ° C., N ₂ (in a nitrogen atmosphere),
By performing heat treatment for 0 minutes, a final shape (see FIG. 5E) can be obtained.

Although the present invention has been described with reference to the above embodiment, the present invention is not limited to the above embodiment, but includes various embodiments according to the principle of the present invention.

[0042]

As described above, according to the present invention, in patterning a polyimide film on an integrated circuit substrate, in patterning a polyimide precursor positive resist with a developing solution, the resist is usually removed after the polyimide precursor patterning. However, since the polyimide precursor resin is cured by heat treatment with the resist left, and the etching residue of the polyimide resin is removed by oxygen plasma using the resist as a mask, oxygen plasma damage to the polyimide resin is performed. While the etching residue of the polyimide resin in the step portion can be removed. For this reason, the present invention is a very effective method for removing the etching residue of the polyimide resin, which is the main cause of the ultraviolet erasing failure of the integrated circuit having the built-in EPROM, for example.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a manufacturing method according to an embodiment of the present invention in the order of steps.

FIG. 2 is a cross-sectional view for explaining a manufacturing method according to one embodiment of the present invention in the order of steps.

FIG. 3 is a cross-sectional view for explaining a manufacturing method according to one embodiment of the present invention in the order of steps.

FIG. 4 is a process sectional view of a second embodiment of the present invention.

FIG. 5 is a process sectional view of a second embodiment of the present invention.

FIG. 6 is a process sectional view of a conventional example.

FIG. 7 is a process sectional view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Field 2 Contact 3 Floating gate 4 Control gate 5 Gate 6 BPSG 7 Al 8 P-SiON 9 Polyimide precursor 10 Positive resist 11 Remaining polyimide etching 12 Polyimide resin 13 P-SiO 14 Photomask

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 29/788 H01L 31/02 B 29/792 31/02

Claims (3)

(57) [Claims] (A) applying a polyimide precursor on a passivation film on a semiconductor substrate; (b) applying a photoresist on the polyimide precursor; and (c) selecting the photoresist. (E) selectively exposing and developing the photoresist to selectively remove the photoresist; and (d) selectively removing the polyimide precursor using the selectively removed photoresist as a mask. ) removing a step of the polyimide precursor to the polyimide resin by a heat treatment, a step of dry etching altogether O2 plasma so that at least the photoresist is remaining film (f), the photoresist was (g) residual film A method of manufacturing a semiconductor device, comprising: 2. (a) a step of applying a polyimide precursor on a passivation film on a semiconductor substrate; (b) a step of applying a photoresist on the polyimide precursor; and (c) selecting the photoresist. (E) selectively exposing and developing the photoresist to selectively remove the photoresist; and (d) selectively removing the polyimide precursor using the selectively removed photoresist as a mask. A) a step of converting the polyimide precursor into a polyimide resin by a heat treatment; and (f) a step of dry-etching the whole with a mixed gas plasma of O 2 and CF 4 so that the photoresist is completely removed. Semiconductor device manufacturing method. 3. The passivation film has a relatively small interval.
Formed on the wiring that is not completely removed by the above-mentioned step (d).
Polyimide on the passivation film between the interconnects
3. The method according to claim 1 , wherein the residue is removed in the step (f) . 4.