JPH01109735A - Inspection method of wiring layer - Google Patents

Abstract

PURPOSE:To detect a defective position in a step coverage by a method wherein a wiring layer is formed onto a semiconductor substrate, light including infrared light having a specific wavelength is applied from the rear of the substrate, light transmitted through the substrate is detected by an infrared detector and the state of coating of the wiring layer is inspected by transmitted light. CONSTITUTION:A semiconductor substrate is composed of an Si substrate 1, a field SiO2 layer 2, a gate SiO2 layer 3, a gate poly Si layer 4, PSG inter-layer insulating layers 5, a contact hole 6 and an Al wiring. The Al wiring layer 7 is deposited on the whole surface on the surface side of the substrate, infrared light is applied from the rear of the Si substrate 1 before the wiring layer is patterned, and leakage infrared light shown in the arrow is detected and the presence of wirings is decided. When light containing a wavelength of 1.3-6mum is used as infrared light at that time, Si, SiO2, PSG, etc., excellently transmit infrared light within the range of the wavelength, and A2 does not transmit even infrared light having any wavelength. Accordingly, the state of the defective or nondefective coating of a metallic wiring layer can be decided quickly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for inspecting the covering state of a wiring layer formed on a semiconductor substrate.

Quickly determines whether the coating state of the metal wiring layer is good or bad.

The purpose is to remove or reprocess defective boards.

After forming a wiring layer on a semiconductor substrate, light containing infrared light with a wavelength of 1.3 to 6 μm is irradiated from the back surface of the substrate.

The configuration is such that the light transmitted through the substrate is detected by an infrared detector, and the covering state of the wiring layer is inspected using the transmitted light.

[Industrial application field]

The present invention relates to a method for inspecting the covering state of a wiring layer formed on a semiconductor substrate.

[Conventional technology]

FIG. 3 is a cross-sectional view of the substrate illustrating the step covering of the contact hole.

In the figure, 1 is a Si substrate, 2 is a field SiO□ layer, 3 is a gate SiO□ layer, 4 is a gate poly-Si layer, 5 is a PSG interlayer insulating layer 36 is a contact hole, and 7 is an AI wiring layer.

FIG. 4 is a cross-sectional view of the substrate illustrating wiring intersection and step covering of the difference portion.

In the figure, 1 is a Si substrate, and 7 is a lower AI wiring layer.

8 is a PSG interlayer insulating layer, and 9 is an upper AI wiring layer.

In the wafer process of integrated circuits, as shown in Fig. 3, above the contact hole 6 for leading out the electrode (part A), and as shown in Fig. 4, the part where two wires 7°9 intersect with each other through an insulating layer. (Part B), the coating of the wiring layer becomes thin, and in severe cases, disconnection may occur.

As a method for improving such step coverage, a method is used in which phosphosilicate glass (PSG) is used for the glabella insulating layer and reflowed.

In this method, PSG is deposited on a substrate, and in the case of Fig. 3, after opening a contact hole, the PSG is heated to 1050° C. or above, and then the PSG flows and smooths out the steep steps of the contact hole.

However, this method has a problem in that as devices become smaller and the diameter of the contact hole becomes approximately 0.5 μm, the hole becomes clogged due to flow.

In addition, as miniaturization requires lowering the process temperature,
It has become impossible to heat the temperature above 1 oso℃.

Furthermore, in the case of FIG. 4, the lower layer wiring is AI.

It is difficult to reflow PSG to improve step coverage of upper layer wiring. This is because AI reacts violently with PSG or 5iO1 at about 500° C., causing damage to the underlying wiring.

On the other hand, in order to lower the reflow temperature, Si containing Pb
O□ or PSG with increased phosphorus concentration is sometimes used, but these increase hygroscopicity and cause deterioration of the characteristics of the integrated circuit.

Another method for improving the one-level difference coating is to make the level difference rounded by etching. However, the control is extremely unstable.

[Problem that the invention seeks to solve]

However, the various step coverage improvement methods mentioned above are
It is extremely difficult to achieve perfection across all manufacturing lofts.

Therefore, one aspect of the present invention is to deposit the metal wiring layer on the substrate at 90°C immediately after depositing the metal wiring layer on the substrate.
The purpose is to detect a defective part of the step coating and repair the defective substrate by repeating the etching or deposition process, or to avoid the loss of post-processing performed on the defective substrate.

[Means for solving problems]

The solution to the above problem is to form a wiring layer on a semiconductor substrate, then
irradiating light containing infrared light with a wavelength of 1.3 to 6 μm from the back side of the substrate, detecting the light transmitted through the substrate with an infrared detector,
This is achieved by a method of inspecting the coating state of the wiring layer using transmitted light.

[Effect]

FIG. 1 is a cross-sectional view of a semiconductor substrate for explaining the present invention.

In the figure, 1 is an St substrate, 2 is a field 5i (h layer, 3 is a gate SiO□ layer, 4 is a gate poly-Si layer, 5 is a PSG interlayer insulating layer, 6 is a contact hole, and 7 is a ^l wiring layer).

In the present invention, after depositing the ^1 wiring layer 7 on the entire surface side of the substrate,
Before patterning the wiring layer, infrared light (IR) is irradiated from the back surface of the St substrate 1, and leaked infrared light indicated by an arrow is detected to determine whether there is a disconnection.

Here, when using infrared light with a wavelength of 1.3 to 6 μm, St, Sing, PSG, etc. can easily transmit infrared light in this wavelength range, and ^l can transmit infrared light of any wavelength. do not.

In general, semiconductor devices are made of single-crystal and polycrystalline Si, and films whose main component is Sing, such as CVD-PSG, CCVD-5in, and thermally oxidized SiO2, except for wiring metals.

On the other hand, the transmittance of Si changes significantly when the wavelength is around 1.3 μm and increases when the wavelength is 1.3 μm or more, while the transmittance of SiO□ decreases significantly when the wavelength is 6 μm or more.

An example of measured transmittance is first order.

Wavelength (μm) 1 1.5~4 10 Transmittance
Si 0.2 99 70(%) 5
iOz 90 90 3PSG
90 90 3AI O,00,
00,0 However, the film thickness is St: 300, 5iOt:
70. PSG: 300°At: 1 μm.

From the above table, if the thickness of St is 300 μm and the thickness of 5T (h is at most 10 μm), the wavelength is 1.5~
It can be seen that more than 90% of infrared light of 4 μm is transmitted if there is no metal film, and if there is an At film of 1 μm, the transmittance becomes o, 0%.

Although the above measurement results were carried out in the wavelength range of 1.5 to 4 μm, for the above-mentioned reasons, even in the wavelength range of 1.3 to 6 μm, there is an effect similar to that of time opening.

〔Example〕

FIG. 2 is a configuration diagram of an apparatus for explaining an embodiment of the present invention.

7, infrared light emitted from a lamp house 11 is reflected by a mirror 12 and is incident on the back surface of a semiconductor substrate 13.

The light transmitted through the semiconductor substrate 13 is imaged on an imaging plane 15 by an imaging lens 14, detected by an infrared detector 16 placed on the imaging plane 15, amplified by an amplifier 17, and output.

Although not shown, a chopper may be placed between the substrate 13 and the imaging lens 14 to AC amplify the output of the infrared detector 16.

In this case, the entire surface of the substrate is reduced by the imaging lens 14 and an image is formed on the photosensitive plate of the infrared detector 16.

The infrared light emitted from the lamp house 11 may be monochromatic light with a specific wavelength within the wavelength range of 1.3 to 6 μm, or may be a plurality of monochromatic lights within this range. Additionally, light within this range can be removed from the infrared and visible.

Even if ultraviolet light is included, this light will not impede the implementation of the present invention because it cannot pass through the metal film.

The lamp house 11 uses, for example, a tungsten lamp filled with iodine (I). The emission spectrum in this case is a continuous spectrum that rises when the wavelength becomes 0.2 μm or more, reaches a peak near 1 μm, and gradually decreases as the wavelength increases.

The infrared detector 16 uses a photovoltaic element using an HgCdTe-based compound semiconductor or a photoconductive element in which a PBS thin film is adhered to a glass substrate.

Now, if one element of the infrared detector 16 is used, ^
The output voltage of the amplifier 17 changes in an analog manner depending on the number or degree of poor coverage of the film.

On the other hand, if a large number of elements of the infrared detector 16 are arranged in an array, an image of the substrate 13 can be obtained on the imaging plane 15, so the output of the amplifier 17 is processed by a computer to
It is also possible to map which locations in 3 have poor coverage.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to quickly determine whether the covering state of a metal wiring layer is good or bad.

Therefore, by removing the defective substrate, losses due to post-processing can be eliminated, or by reprocessing the defective substrate, it is possible to convert it into a good substrate.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor substrate explaining the present invention. FIG. 2 is a configuration diagram of an apparatus for explaining an embodiment of the present invention. FIG. 3 is a cross-sectional view of the substrate illustrating the step covering of the contact hole. FIG. 4 is a cross-sectional view of the substrate illustrating step coverage at wiring intersections. In fig. 1 is a Si substrate. 2 is a field SiO□ layer. 3 is the gate Sin layer. 4 is a gate poly-Si layer. 5 is a PSG interlayer insulating layer. 6 is a contact hole. 7 is the AI wiring layer. 11 is the lamp house. 12 is a mirror. 13 is a semiconductor substrate. 14 is an imaging lens. 15 is an imaging plane. 16 is an infrared detector. Spear 2M

Claims (1)

[Claims] After forming a wiring layer on a semiconductor substrate, light containing infrared light with a wavelength of 1.3 to 6 μm is irradiated from the back side of the substrate, and the light transmitted through the substrate is detected by an infrared detector. A method for inspecting a wiring layer, comprising inspecting a covering state of the wiring layer.