JP2667517B2 - Method of forming hole in interlayer insulating film - Google Patents

Description

Description: [Object of the Invention] (Industrial field of application) The present invention relates to a method for forming an opening in an interlayer insulating film, for example, a method for forming an opening in an interlayer insulating film of a thin-film multilayer wiring board. Regarding

(Prior Art) In recent years, with the increase in the density of substrate wiring, the development of a wiring substrate using a thin film forming technique capable of forming a wiring having a narrow line width is progressing. This is because the limit of wiring width due to thick film printing etc.
This is because the width of the wiring can be easily formed even when the width of the wiring is 100 μm or less by the thin film forming technique using the photolithography method, while the width of the chemical is about 100 μm. In addition, fine wiring formed by the thin film forming technique is essential because it contributes to high density wiring, that is, miniaturization of the device or improvement of reliability of the device.

Such wiring by the thin film forming technique usually has a multi-layer wiring structure composed of two or more wiring layers. As a matter of course, multi-layer wiring of a wiring board by a thin film forming technique is also progressing.

By the way, as the number of wiring layers increases, means for electrically separating these three-dimensionally arranged wirings becomes necessary. At present, as a means of this electrical isolation, insulation is performed by an insulator such as polyimide on a multilayer wiring board. Such a layer that insulates three-dimensionally arranged wirings is generally called an interlayer insulating film.
In this interlayer insulating film, by stacking two or more layers of the insulating material that constitutes the interlayer insulating film, the reliability in further electrical separation is improved. This means that if the interlayer insulating film is composed of only one layer made of an insulating material, if a pinhole is formed in this, the wirings located above and below will easily cause insulation failure. However,
If two or more layers are used, even if pinholes occur in the insulator, these pinholes rarely coincide with each other. Therefore, the probability of causing insulation failure is greatly reduced.

From the above points, currently, the interlayer insulating film is usually 2
It is composed of an insulator stacked in layers or more.

However, in the case of an interlayer insulating film formed of an insulating material laminated in two or more layers, an opening portion, for example, a contact hole for connecting a wiring located at the upper part and a wiring located at the lower part is opened. The problem described below arises when drilling.

The interlayer insulating film is composed of an insulator composed of two or more layers, and it is necessary to form a contact hole through these two or more insulators. Therefore, it is necessary to use, for example, an etching solution or the like to etch each of these two or more layers of insulating material, and for example, a photoresist that matches the properties of the etching solution is required.
When a photoresist suitable for the etching solution is required, two or more photomasks used for the photo-etching process corresponding to the photoresist are required. That is, one photomask is required for each insulating layer. If the photoresist is a positive type, this photomask has a large area of the transparent portion (for example, a contact hole opening pattern) of the photomask that matches the insulator existing at the bottom, and becomes the insulator existing at the top. Is set so that the area of the transmission part of the photomask becomes smaller as the distance becomes smaller. This is taken into consideration for the alignment allowance of the mask and for the conductor layer forming the wiring to have, for example, a contact hole shape that facilitates vapor deposition.

On the other hand, if the photoresist is a negative type, the opposite is true, and the blocking portion has a contact hole opening pattern.

However, since the photomasks used in these photo-etching processes have very similar shapes, it is easy to make a mistake in the order of the photomasks used. If the order is wrong, a contact hole as shown in FIG. 3 will be formed. Referring to FIG.
A first insulating layer 3 and a second insulating layer 4 constituting an interlayer insulating film are formed on a wiring board 1 on which a wiring 2 of a layer is formed. Thus, assuming that the width X2 of the opening of the second insulating layer 4 existing above the opening X1 of the opening of the first insulating layer 3 is larger than the width X1 of the opening A of the first insulating layer 3 shown in FIG. Part of
That is, although not shown, when a conductor layer constituting the second layer wiring is deposited, for example, in the step portion, the step coverage deteriorates. In the worst case, the wiring is stepped. In other words, the wiring is stepped open and causes a reduction in manufacturing yield.

Also, there is a problem that a great deal of cost is required for designing and manufacturing the photomask as the number of photomasks increases.

(Problems to be Solved by the Invention) The present invention has been made in view of the above points, and is used when forming an opening portion such as a contact hole in an interlayer insulating film formed of multiple insulating layers. Apertures in the interlayer insulating film can be reliably formed in the interlayer insulating film composed of multiple insulating films without increasing the number of photomasks and achieving cost savings, and without increasing the number of photomasks. It is an object of the present invention to provide a method for forming a film.

[Structure of the Invention] (Means for Solving the Problems) According to the method for forming an opening in the first interlayer insulating film according to the present invention, a positive photoresist and a photomask are used to form multiple layers by proximity exposure. Forming an opening in the interlayer insulating film made of an insulating layer, the print gap from the photoresist surface formed on the lowermost insulating layer of the multilayer insulating layer to the photomask surface is reduced. Proximity exposure is performed by setting it to be the largest, apertures are formed by predetermined insulating layer removing means, and the print gap is gradually reduced as the insulating layer existing in the upper part is sequentially formed. The proximity exposure is performed by setting as described above, and the opening portions are sequentially formed by predetermined insulating layer removing means.

Further, according to the second forming method, in the formation of the opening portion in the interlayer insulating film formed of the multiple insulating layers by proximity exposure using the negative type photoresist and the photomask, the above-mentioned insulation of the multiple layers is formed. Of the layers, the proximity exposure is performed by setting the print gap from the photoresist surface formed on the lowermost insulating layer to the photomask surface to be the smallest, and opened by predetermined insulating layer removing means. A hole is formed, and the above-mentioned print gap is set so as to gradually increase as the insulating layer existing on the upper portion is formed. Proximity exposure is performed, and the opening is sequentially formed by a predetermined insulating layer removing means. Is formed.

Further, according to the third forming method, a negative insulating layer;
Using a photomask and forming an opening in an interlayer insulating film composed of multiple layers of the negative-type photosensitive insulating layers by proximity exposure, the plurality of insulating layers are present at the bottom. Proximity exposure is performed by setting the print gap from the surface of the insulating layer to the surface of the photomask to be the smallest, and an opening is formed by a predetermined insulating layer removing means, which in turn becomes the insulating layer existing on the upper side. According to the above, the exposure gap is set so that the print gap gradually increases, and the opening portions are sequentially formed by a predetermined insulating layer removing unit.

(Function) In the above-described method for forming the opening in the interlayer insulating film, the amount of light wraparound due to the light diffraction phenomenon at the transmission part of the photomask or at the outer peripheral part of the blocking part at the time of proximity exposure is described. To use. For example, if the print gap is increased, the area of the photoresist to which the photomask pattern is projected increases, and the exposure swelling increases. Conversely, if the print gap is made smaller, the exposed portion becomes smaller. As a result, the area on which the pattern formed on the photomask is projected, that is, the exposure area can be freely controlled with one photomask. Therefore, an opening can be formed in the interlayer insulating film formed of a multi-layer insulating layer by using only one photomask.

(Embodiment) A method for forming an opening in an interlayer insulating film according to an embodiment of the present invention will be described below with reference to the drawings.

First, as shown in FIG. 1A, a first insulating layer 3 made of, for example, polyimide is applied onto a wiring substrate 1 on which a first-layer metal wiring 2 is formed by using a spinner. Next, the first photoresist 5 having a positive photosensitivity is applied using a spinner. Then, for example, ultraviolet rays hν are irradiated to the first photoresist 5 through the photomask 7 with a predetermined print gap Y1 (first
Proximity exposure process). In this photomask 7,
An ultraviolet transmitting portion 8 formed in a predetermined contact hole opening pattern (having a width of, for example, Z1) is formed.
The ultraviolet ray hν passing through the transmissive portion 8 is diffracted at the outer peripheral portion 9 of the transmissive portion 8 and becomes larger than the width Z1 of the transmissive portion 8 when projected on the first photoresist 5. This size increases as the print gap Y1 increases. Here, for example, the print gap Y1 is 14 μm, and the width Z1 of the contact hole opening pattern is 20 μm.

Next, as shown in FIG. 1 (b), the exposed portion of the first photoresist 5 is removed by a predetermined removing means in the first proximity exposure step. At this time, the width of the removed portion is defined as X1. Where width X1 is
For example, it is about 23 μm.

Next, as shown in FIG. 1C, the first insulating layer 3 made of, for example, polyimide is removed by a predetermined removing means by using the first photoresist 5 as a mask. The width of the portion removed at this time is substantially the same as the width X1.

Next, as shown in FIG. 1D, a second insulating layer 4 made of, for example, polyimide is applied to the apparatus shown in FIG. 1C by using a spinner. Next, the second photosensitive type
Is applied using a spinner. next,
Using the photomask 7 used in the first proximity exposure step, this time, with a predetermined print gap Y2, the second photoresist 6 is exposed to ultraviolet rays hν.
(A second proximity exposure step). At this time, the print gap Y2 is set to be smaller than the print gap Y1. For example, the print gap Y2 is 6 μm. By doing so, the amount of wraparound of the light diffracted at the outer peripheral portion 9 of the transmission portion 8 is smaller than in the first proximity exposure step. Therefore,
The exposed area of the second photoresist 6 is smaller than the exposed area of the first photoresist 5.

Next, as shown in FIG. 1 (e), the exposed portion of the second photoresist 6 is removed by a predetermined removing means in the second proximity exposure step. At this time, the width of the removed portion is defined as X2. Where width X2 is
For example, it is about 19 μm.

Next, as shown in FIG. 1 (f), the second insulating layer 4 made of, for example, polyimide is removed by a predetermined removing means using the second photoresist 6 as a mask. The width of the portion removed at this time is almost the same as the above X2. Thereafter, although not shown, including the inside of the opening,
A conductor layer serving as a predetermined second-layer metal wiring is, for example, vapor-deposited and patterned into a predetermined wiring pattern.

Through the steps described above, for example, an opening serving as a contact hole is formed by the method for forming an opening in the interlayer insulating film according to the embodiment of the present invention.

According to such a method for forming an opening in the interlayer insulating film, the interlayer insulating film can be formed by changing the print gap variously, for example, Y1 (14 μm) and Y2 (6 μm) with one photoresist 7. Openings of different sizes can be formed in the constituent first, second polyimide layers, for example polyimide. That is, an opening having a good cross-sectional shape as shown in FIG. 1 (f) is formed by a simple method of simply adjusting the print gap. Moreover, even if the number of insulating layers forming the interlayer insulating film is three or more, the number of photomasks is only one and the cost can be reduced. Also, since the photomask used is 1, there is no fear of making a mistake in the order of use.
Therefore, there is no reduction in yield due to an incorrect order of using the photomask.

Next, a second embodiment will be described with reference to FIGS. 2 (a) to 2 (d). In the second example, a material in which the insulating layer itself has negative photosensitivity is used for the insulating layer constituting the interlayer insulating film.

First, as shown in FIG. 2A, a first insulating layer 13 made of, for example, a negative photosensitive polyimide is formed on the wiring metal plate 1 on which the first-layer metal wiring 2 is formed. Apply using a spinner. And the predetermined print gap
With Y1, through the photomask 17, the first insulating layer
13 is irradiated with, for example, ultraviolet light hν (first proximity exposure step). The photomask 17 has an ultraviolet blocking portion 18 formed in a predetermined contact hole opening pattern (having a width of, for example, Z2). This blocking part
The ultraviolet ray hν that has passed through the transmission parts other than 18 is diffracted at the outer peripheral part 19 of the blocking part 18, and becomes smaller than the width Z2 of the blocking part 18 when projected on the first insulating layer 13. This size decreases as the print gap Y1 increases. Here, for example, the print gap Y1 is 6 μm, and the contact hole opening pattern width Z2 is 25 μm.

Next, as shown in FIG. 2B, the unexposed portion of the first insulating layer 13 is removed by a predetermined removing means in the first proximity exposure step. At this time, the width of the removed portion is defined as X1. Thereafter, the first insulating layer 13 is baked at a high temperature and dried. Here, the width X1 is, for example, about 23 μm.

Next, as shown in FIG. 2 (c), the apparatus shown in FIG.
Of the insulating layer 14 is applied using a spinner. Next, the photomask 17 used in the first proximity exposure step is used.
This time, the second insulating layer 14 is irradiated with ultraviolet rays hν with a predetermined print gap Y2 (second proximity exposure step). At this time, the print gap Y2 is set to be larger than the print gap Y1. For example, the print gap Y2 is 16μ
m. By doing so, the amount of wraparound of the light diffracted at the outer peripheral portion 19 of the blocking portion 18 becomes larger than in the first proximity exposure step. Therefore, the exposed area of the second insulating layer 14 is larger than the exposed area of the first insulating layer 13.

Next, as shown in FIG. 2 (e), the unexposed portion of the second photoresist 6 is removed by a predetermined removing means in the second proximity exposure step.
At this time, the width of the removed portion is defined as X2. After a while
The second insulating layer 14 is baked at a high temperature and dried.
Here, the width X1 is, for example, about 20 μm. Thereafter, although not shown, a conductor layer serving as a predetermined metal wiring including an opening portion is deposited, for example, and patterned into a predetermined wiring pattern.

Through the steps described above, for example, an opening serving as a contact hole is formed by the method for forming an opening in the interlayer insulating film according to the embodiment of the present invention.

According to the method of forming the opening in the interlayer insulating film according to the second embodiment, the print gap is set to, for example, Y1 with one photoresist 17 as in the first embodiment.
(6 μm) and Y2 (14 μm) are variously changed to form the interlayer insulating film. For example, openings of different sizes can be formed in the first and second insulating layers 13 and 14 of a negative photosensitive polyimide. That is, the second method is a simple method of appropriately adjusting the print gap.
An opening having a good sectional shape as shown in FIG. Moreover, the number of insulating layers constituting the interlayer insulating film is three.
Even if there are more or more layers, only one photomask is required, and the cost can be reduced. Also, since only one photomask is used, there is no risk of making a mistake in the order of use. Therefore, there is no reduction in yield due to an incorrect order of using the photomask.

Although the positive type photoresist is used in the first embodiment, it goes without saying that a negative type photoresist may be used separately. However, in this case, the print gaps Y1 and Y2 are set such that Y1 <Y2, contrary to the first embodiment.

On the other hand, in the second embodiment, the negative photosensitive polyimide was used for the insulating layer constituting the interlayer insulating film. However, a separate positive photosensitive insulating material was used for the interlayer insulating film. It goes without saying that an insulating layer may be used. However, in this case, the print gaps Y1 and Y2
Contrary to the second embodiment, the setting is set so that Y1> Y2.

In the first and second embodiments, specific numerical values have been described by taking the interlayer insulating film of the wiring board as an example, but various numerical values may be appropriately adjusted without being limited to these numerical values. . Further, the present invention is not limited to the interlayer insulating film of the wiring board, but may be a semiconductor device having an interlayer insulating film composed of multiple insulating films, for example, a semiconductor device having various sizes such as a power element, which is relatively large. Of course, it is applicable. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

In the present invention, since the wraparound amount due to the diffraction phenomenon of the holes is used, there is a concern that the amount of light, that is, the exposure capability is reduced, when the print gap becomes large, for example. However, this point can be easily avoided by increasing the light irradiation amount.

[Effects of the Invention] As described above, according to the present invention, when forming an opening such as a contact hole in an interlayer insulating film composed of multiple insulating layers, an increase in the number of photomasks to be used is suppressed, and cost is reduced. Is achieved, and a method for forming an opening in an interlayer insulating film capable of reliably forming an opening in an interlayer insulating film composed of multiple insulating layers without increasing the number of photomasks is provided.

[Brief description of the drawings]

1 (a) to 1 (f) are sectional views showing a method of forming an opening in an interlayer insulating film according to the first embodiment of the present invention in the order of steps, and FIGS. 2 (a) to 2 (f). Figure 2 (d)
FIG. 3 is a sectional view showing a method of forming an opening portion in an interlayer insulating film according to the second embodiment of the present invention in the order of steps, and FIG. 3 is a sectional view showing a defective example caused by a conventional forming method. 1 ... wiring board, 2 ... wiring, 3,13 ... first insulating layer,
4, 14 ... second insulating layer, 5 ... first photoresist, 6
...... Second photoresist, 7,17 ...... Photo mask, 8 ......
Transmissive part, 18 ... blocking part, 9, 19 ... ... outer peripheral part.

Claims (3)

(57) [Claims] 1. A method of forming a hole in an interlayer insulating film made of a multilayer insulating layer by proximity exposure using a positive photoresist and a photomask, wherein the bottom of the multilayer insulating layers is formed. Performing proximity exposure by setting the print gap from the photoresist surface formed on the insulating layer present to the photomask surface to the maximum, and forming an opening by a predetermined insulating layer removing means, The print gap is set so as to be gradually reduced as the insulating layer existing in the upper portion is gradually formed, and the proximity exposure is performed, and the opening is sequentially formed by the predetermined insulating layer removing means. A method for forming an opening in an interlayer insulating film. 2. A negative type photoresist and a photomask are used to form an opening in an interlayer insulating film made of a multilayer insulating layer by proximity exposure, and the bottom of the multilayer insulating layers is formed. Performing proximity exposure by setting the print gap from the photoresist surface formed on the insulating layer present to the photomask surface to the smallest, and forming an opening by a predetermined insulating layer removing means, The print gap is set so as to gradually increase as the insulating layer existing in the upper part is gradually increased, and the proximity exposure is performed, and the opening is sequentially formed by the predetermined insulating layer removing means. A method for forming an opening in an interlayer insulating film. 3. The method according to claim 1, wherein a plurality of openings are formed in the interlayer insulating film composed of the plurality of negative-type photosensitive insulating layers by proximity exposure using a negative-type insulating layer and a photomask. Of the above insulating layers, a proximity exposure is performed by setting the print gap from the lowermost insulating surface to the photomask surface to be the smallest, and an opening is formed by predetermined insulating layer removing means. The print exposure is set so that the print gap is gradually increased as the insulating layer existing in the upper portion is gradually formed, and the aperture is sequentially formed by the predetermined insulating layer removing means. A method for forming an opening in an interlayer insulating film.