JPH02278851A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress a flow of a photosensitive polyimide in a curing process of the polyimide and to control a taper shape of a contact hole by a method wherein, after the contact hole has been formed, ultraviolet rays (UV) are irradiated. CONSTITUTION:A wiring layer 3 of Al or the like which has been formed on a substrate 1 is coated with a photosensitive polyimide 2 by a spin coating method in such a way that the surface becomes flat. Then, a part other than a formation region of a contact hole 4 is irradiated by using a mercury vapor lamp containing H rays, G rays and I rays; the photosensitive polyimide in a part which has not been exposed to light in the contact hole 4 is removed by using a developing solution. Then, a polyimide 5 after an exposure operation by using the mercury vapor lamp is irradiated with ultraviolet rays; a heating operation at this time is executed on a hot plate. When a surface temperature of the substrate is changed properly, a taper shape after a curing operation can be controlled to a desired shape. Then, a prescribed curing operation is executed in nitrogen; the polyimide 5 after the exposure operation is hardened. During this curing operation, the polyimide is hardened to a certain extent by a previous UV irradiation process. Thereby, it is possible to suppress a flow in an opening part of the contact hole.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a method for manufacturing a glabella insulating film that insulates between each wiring layer in a semiconductor device with multilayer wiring, and in a curing process of photosensitive polyimide, the flow of polyimide is suppressed and contact is achieved. For the purpose of controlling the taper shape of the hole, a step of forming a photosensitive polyimide film 2 on a first electrically conductive wiring layer 1 formed on a substrate 1; A step of exposing the polyimide film 2 to light and forming a contact hole 4 through which the first wiring layer 1 is exposed through development; A step of irradiating the exposed polyimide film 5 with ultraviolet rays; A step of irradiating the exposed polyimide film 5 with ultraviolet rays; The second wiring layer 6 is formed inside the contact hole 4 and on the exposed polyimide film 5, and the second wiring N6 is patterned.

[Industrial application field]

The present invention relates to a method for manufacturing a glabellar insulating film that insulates between wiring layers in a semiconductor device with multilayer wiring.

[Conventional technology]

Conventionally, semiconductor integrated circuits (Integrated C1
In the multilayer wiring of rcuit (IC), an insulating film such as polyimide is used to insulate each wiring layer. Contact holes are then opened in the polyimide at locations where electrical conduction is desired between each wiring layer, and wiring layers are buried in the holes to establish contact between the upper and lower wiring layers.

Two conventional methods for forming contact holes in polyimide are to apply a resist film on top of the polyimide film, and then use the resist film in a predetermined pattern as a mask to remove unnecessary polyimide from the contact hole area by etching. However, when the wiring layer is multi-layered, the process of resist coating, developing, etching and removal must be performed correspondingly, resulting in an increase in the number of processes.

Therefore, instead of buttering using resist,
A method has begun to be used in which a photosensitive polyimide is used as an insulating film, and contact holes are formed by direct exposure and patterning. With this method, there is no step of forming a resist film, so the number of steps can be reduced.

The method will be explained using FIGS. 2(a) to 2(C).

First, as shown in FIG.
Apply it evenly with a spin cord, etc. Photosensitive polyimide has the property that when it is irradiated with light of a certain wavelength, the polyimide in the irradiated area becomes insoluble in a specific developer, and only the polyimide in the area that is not irradiated becomes soluble in the developer. It's worth it. Therefore, patterning using a negative resist works in the same way as etching polyimide.

Next, as shown in FIG. 2(b), a mercury lamp is irradiated onto the area other than the area where the contact hole 24 with a diameter of 2 μm is formed, and a developing process is performed to remove the photosensitive polyimide from the area where the contact hole 24 is not exposed. remove.

Next, as shown in FIG. 2(C), curing is performed at 450° C. to harden the polyimide 25 after exposure.

Through this curing process, the polyimide 25 after exposure is
As shown in the figure, it flows and becomes a tapered shape.

At this time, the opening L expands due to the flow as shown in the figure.
is approximately 3.611m wide. This is thought to be because the polyimide becomes soft and flows before the target temperature is reached during curing, and then hardens at a temperature of 450°C.

Thereafter, A2 is formed on the entire surface by sputtering, and a resist is applied thereon and patterned to form a second wiring layer 26.

[Problem to be solved by the invention]

Conventionally, as shown in Fig. 2(C), polyimide 25 was exposed after exposure.
The tapered shape had the advantage of better step coverage.

However, with the miniaturization of ICs, pattern rules have become narrower, and the spread L of the opening of a contact hole due to the tapered shape overlaps with the spread part of the opening of an adjacent contact hole, causing a problem of pattern short circuits. It has arisen.

This problem will be explained using FIGS. 3 and 4.

FIG. 3 shows a top view of the multilayer wiring pattern when such a pattern short occurs, and FIG.
4 is a diagram showing a cross section taken along line AA' in FIG. 3. FIG.

Both figures show how the first layer Al wiring JW 33 and the second layer Al wiring layer 34 are connected through the contact hole 32. When the opening of the contact hole widens due to the flow as described above, the regions 31 of adjacent contact holes widened by the flow at point P will short-circuit with each other, as shown in the figure.

This is because the l attached to the region 31 spread by the flow
However, even during the etching when forming the second layer Af wiring pattern, AN is deposited deeper than the etching end point, as shown at point P in the figure, so this remains without being removed, resulting in a short circuit. This is because you end up doing it. Beyond the etching end point.

If you do over-etching, the short circuit will disappear, but
This time, even the polyimide insulating film between the eyebrows is etched and becomes thinner, resulting in a lack of withstand voltage.

Furthermore, since the shape of the opening of the contact hole due to the flow after curing changes depending on the temperature of curing, there is also the problem that the shape cannot be freely controlled.

Therefore, an object of the present invention is to control the tapered shape of a contact hole by suppressing the flow of polyimide in a photosensitive polyimide curing process.

[Means to solve the problem]

A step of forming a photosensitive polyimide film 2 on a conductive first wiring layer 1 formed on a substrate 1, selectively exposing the photosensitive polyimide film 2 and developing the first wiring layer 1. a step of forming a contact hole 4 through which the wiring layer 1 is exposed; a step of irradiating the exposed polyimide film 5 with ultraviolet rays; a step of curing and hardening the exposed polyimide film 5; 4 and on the exposed polyimide film 5, and the second wiring layer 6 is patterned.

[Effect]

In the present invention, after forming a contact hole, by irradiating ultraviolet (UV) light, a crosslink is formed between the main chains of the photosensitive polyimide and the polyimide is cured, and the opening of the contact hole due to the flow when cured. The spread of can be suppressed.

FIG. 5 shows a graph of the relationship between the UV irradiation temperature and the width of the opening. As shown in the figure, the width of the opening can be controlled by changing the UV irradiation temperature.

〔Example〕

An embodiment of the present invention will be described using FIGS. 1(a) to (d).

First, as shown in FIG. 1(a), A
! On top of the wiring layer 3, etc., there is a υI? 3100
．． UI? A photosensitive polyimide 2 such as 3600.1IR3B00 was coated with 6
Coat to a thickness of μm.

Next, as shown in FIG. 1(b), HlG, ! DV162.
The photosensitive polyimide in the non-exposed areas of the contact hole 4 is removed using a developer such as DV502.

The process up to this point is the same as the conventional method.

Next, as shown in FIG. 1(C), the polyimide 5 was exposed to light using a mercury lamp at an illuminance of 650 aa W/cd.
.

Ultraviolet rays with a wavelength of 220 to 320 nm are irradiated for 3 minutes at a temperature of 250°C. Heating at this time is performed on a hot plate to bring the temperature of the substrate surface to 250°C. By appropriately changing the substrate surface temperature, the tapered shape after curing can be controlled to a desired shape as shown in FIG. In addition to temperature, illuminance and time are also related to the taper shape.

Next, as shown in Figure 1(d), in nitrogen (N2) at a temperature of 4.
Curing is performed at 50'C for 30 minutes to harden the exposed polyimide 5. In this curing, since the polyimide has already been hardened to some extent by the previous UV irradiation process, flow at the opening of the contact hole can be suppressed. At this time, the tapered part due to the flow indicated by M in the figure is 1.1
It is about μm, which is 3.6 when conventional UV irradiation is not performed.
Compared to μm, the expansion of the contact hole opening due to flow can be suppressed to about 1/3.

Therefore, even if contact holes are formed next to each other in areas with narrow wiring spacing, the openings of the contact holes do not widen, so the polyimide between the contact holes is different from the polyimide in other areas. formed at the same height. And above.

Even in etching when forming a layer wiring pattern,
Since the polyimide between the contact holes has a sufficient height, adjacent wiring layers 6 will not be short-circuited.

Furthermore, since no resist is used to pattern the photosensitive polyimide, the number of man-hours can be reduced accordingly, and the more wiring layers there are, the more the number of man-hours can be reduced.

〔effect〕

As explained above, according to the present invention, the opening of the contact hole does not widen even if the photosensitive polyimide is exposed, so the wiring spacing can be narrowed, and the number of steps can be reduced compared to when resist is used. This effect is achieved.

Further, by controlling the intensity and time of UV irradiation, it is possible to obtain a desired tapered shape.

Therefore, the present invention greatly contributes to the miniaturization and improvement of reliability of ICs.

[Brief explanation of drawings]

FIGS. 1(a) to (d) are diagrams for explaining an embodiment of the present invention, and FIGS. 2(a) to (C) are diagrams for explaining a conventional technique. , FIG. 3 and FIG. 4 are diagrams for explaining the problems of the conventional technology, and FIG. 5 is a graph showing the relationship between the UV irradiation temperature and the spread of the opening. l, 21... Substrate 2.22... Photosensitive polyimide 3.23... Wiring layer 4.24...
- Contact hole 5.25...Polyimide after exposure 6.26...Wiring layer 31...Region expanded by flow 32...Contact hole 33...First wiring layer 34... 2nd layer wiring layer % 1 mouth Uv clothing M twice [°C] UV, QjN -JI-fl-111'C) f5 f
) L? ')? Knee i7) 11At#zu')”y
Fuka S diagram

Claims (1)

[Claims] A step of forming a photosensitive polyimide film (2) on a first electrically conductive wiring layer (1) formed on a substrate (1); A step of exposing the polyimide film (2) to light and forming a contact hole (4) through which the first wiring layer (1) is exposed by development; A step of irradiating the exposed polyimide film (5) with ultraviolet rays. , curing and hardening the exposed polyimide film (5), forming a second wiring layer (6) inside the contact hole (4) and on the exposed polyimide film (5), A method for manufacturing a semiconductor device, comprising the step of patterning the second wiring layer (6).