JPH036819A - Method for inspecting etching state and structure of pattern to be inspected - Google Patents

Abstract

PURPOSE:To quantitatively inspect the residual film state in a contact hole after etching by radiating a region to be etched with an electron beam, and detecting an electron beam induced current induced at a P-N junction. CONSTITUTION:An N-type diffused layer 7 is extended directly from under a contact hole 3, and a pattern to be inspected having electrode pads 8 is formed thereon. When a reverse bias is applied between the pad 8 and a silicon substrate 1 and the hole 3 is irradiated with an electron beam 4, electron-hole pairs 5 are induced in the vicinity of the P-N junction, drawn to regions, and detected by an ammeter 9 as an external current. The degree of the external current varying according to the residual film degree in the hole 3 can be quantitatively obtained by regulating an acceleration voltage of the beam 4, a current level of a sample, and a voltage application level of a variable power source 10, thereby accurately obtaining the residual film state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applications] The present invention relates to a method for inspecting an etching state after etching processing, which is a manufacturing process of a semiconductor device, and a structure of a pattern to be inspected.

[Conventional technology]

FIG. 4 shows a schematic cross-sectional view of the contact hole of the n-type MO3+- transistor after etching.

In this figure, 1 is a silicon substrate, 2 is a single layer or multilayer inorganic glass group formed on the silicon substrate 1, and 3 is a contact hole formed in the inorganic glass film 2 by etching using a resist as a mask. show.

In the contact hole 3, it is necessary to make an ohmic contact between the metal wiring to be formed in the next step and the silicon substrate 1. Therefore, if even a small amount of --like residual film remains inside the contact hole 3 due to insufficient etching, it is necessary to make an ohmic contact with the silicon substrate 1. This will result in poor bonding. Therefore, inspection of the etching condition of the contact hole 3 is very important.

Conventionally, the inside of the contact hole 3 after the etching process has been inspected from above using an optical microscope or an electron microscope. In the case of an optical microscope, the remaining film condition of the inorganic glass film 2 is judged from the change in color, and then an electron microscope 1 is used.
In the case of the m-mirror, judgment was made based on changes in contrast.

[Problem to be solved by the invention]

The conventional etching state inspection method described above is no longer able to cope with the reduction in the diameter of contact hole 3 and the increase in aspect ratio 1 due to the miniaturization of devices, and the remaining film inside contact hole 3 is It is becoming very difficult to inspect the situation.

The present invention has been made to solve the above-mentioned problems, and includes an inspection method that can accurately and quantitatively inspect the state of remaining film inside a contact hole after etching, and an inspection method used for the inspection. The purpose is to obtain the structure of the turn.

[Means to solve the problem]

The etching state inspection method according to the present invention irradiates an etched region on a diffusion layer constituting a pn junction with an electron beam, and detects an electron beam induced current induced at the pn junction. This allows the state of the remaining film after etching to be inspected.

Further, the structure of the pattern to be inspected according to the present invention constitutes a pn junction, and electrode pads are formed on a diffusion layer extending from directly below the part to be etched.

[Effect]

In the etching state inspection method of this invention, pn
The degree of residual film is inspected from the electron beam induced current induced at the junction.

Further, in the structure of the pattern to be inspected according to the present invention, the electron beam induced current is detected using the electrode pad on the diffusion layer.

〔Example〕

First, the principle of this invention will be explained.

Fig. 3 is a schematic cross-sectional view of an n-type contact hole showing the state of electron-hole pairs induced at the pn junction surface by an electron beam, and Fig. 3(a) shows that the etching of the contact hole has been completely etched. Figure 3(b) shows the case where this is done.
indicates a case where etching is incomplete and there is a residual film inside the contact hole.

In these figures, 1, 2, and 3 are similar to those in Figure 4, 4 is an electron beam, 5 is an electron-hole pair induced near the pn junction, and 6 is a residual film from etching. .

When Si is irradiated with an electron beam, one electron-hole pair is generated per 3.75 eV. In the diffusion region, the generated electron-hole pairs are recombined and do not contribute to external current. On the other hand, the electron-hole pair generated near the pn junction is
By applying a reverse bias to the pn junction, electrons
The holes flow separately into the p region and are observed as an external current. The electron beam irradiated onto the Si surface reaches the p-n junction surface while attenuating its energy due to absorption inside the silicon, but as shown in FIG. 3(b), the electron beam reaches the p-n junction surface.
If there is a residual film of inorganic glass inside, the energy is attenuated when passing through the residual film, and the degree of generation of electron-hole pairs induced at the bonding surface is reduced. Furthermore, if excessive etching is performed and the underlying 81 substrate itself is slightly etched, the distance from the substrate surface to the pn junction will become shorter, and the degree of generation of electron-hole pairs induced at the pn junction will be reduced. To increase. In this way, the degree of generation of electron-hole pairs induced near the pn junction surface changes depending on the level of the remaining film, so by measuring the external current in g, the level of the remaining film can be quantitatively determined. Can you test it?

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

FIG. 1 is a diagram showing the most basic structure and inspection method of the pattern to be inspected in this invention. FIG. 1(a) is a schematic cross-sectional view, and FIG. It is a corresponding top pattern figure.

In these figures, 1 to 5 are similar to those in FIGS. 3 and 4, 7 is an n-type diffusion layer, 8 is a polycrystalline silicon electrode pad with phosphorus diffused, and 9 is an electrode pad for electron beam induced current. A detecting ammeter 10 indicates a variable power supply device that supplies a bias voltage to be applied to the pn junction.

First, in order to perform the inspection, as shown in FIG. 1(a), the n-type diffusion layer 7 is extended from directly below the contact hole 3,
A pattern to be inspected having electrode pads 8 is formed thereon. Next, a reverse bias is applied between the electrode pad 8 and the silicon substrate 1, and an electron beam 4 is applied to the contact hole 3.
When irradiated with
It is detected by the ammeter 9 as an external current. At this time, the degree of external current that changes depending on the degree of film remaining in the contact hole 3 can be quantitatively determined by adjusting the accelerating voltage of the electron beam 4, the level of the sample current, the voltage application level by the variable power supply 10, etc. This allows you to accurately know the remaining film status.

Furthermore, in this embodiment, a phosphorus-diffused polycrystalline silicon film is used for the electrode pad 8, but a phosphorus-diffused polycrystalline silicon film is normally used as a gate wiring material for MO3 type semiconductor devices. Day 1 - The wiring forming step is normally performed before the contact hole 3 etching step.

Therefore, the structure of the pattern to be inspected in FIG. 1 can be obtained by making slight additional changes to the mask pattern before the contact hole 3 etching process in the actual manufacturing process of the semiconductor device, without adding any special processing steps. can be formed during the manufacturing process.

Therefore, it is possible to form it in an empty area within an actual product substrate.

In addition, in the above embodiment, an example of the most basic structure was shown in which one of the contact holes 3 was inspected, but a large number of contact holes 3 as shown in FIG. 2 may be inspected, and electronic Since the scanning area of the beam 4 can be changed arbitrarily, it is also possible to irradiate each contact hole 3 with the beam for individual inspection. - Furthermore, by forming a plurality of such patterns to be inspected on a substrate, it is possible to obtain a distribution within the plane of the substrate.

Furthermore, the degree of occurrence of crystal defects inside the diffusion layer and in the vicinity of the pn junction can be simultaneously evaluated using the same method and the same pattern to be inspected as in the above embodiment.

In this case, if a crystal defect exists, a local energy level is generated there, and the electron-hole pair 5 induced by the electron beam 4 is captured, thereby increasing the external current. Therefore, if the degree of the etching residual film 6 in the contact hole 3 is the same, the degree of occurrence of defects can be detected from the amount of current.

〔Effect of the invention〕

As explained above, the etching state inspection method of the present invention irradiates the etched region on the diffusion layer constituting the pn junction with an electron beam to detect the electron beam induced at the pn junction. Since the state of the remaining film after etching is inspected by detecting the current, the extent of the remaining film can be quantitatively and accurately determined from the electron beam induced current induced at the pn junction even in minute areas. It has the effect of being measurable.

In addition, the structure of the pattern to be inspected according to the present invention constitutes a pn junction, and the electrode pad is simply formed on the diffusion layer extended from directly below the part to be etched. Change the previous mask pattern slightly! Therefore, it can be easily formed in a vacant area and is ideal for implementing the above inspection method.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the structure of the pattern to be inspected and the inspection method of the present invention, FIG. 2 is a diagram showing another embodiment of the structure of the pattern to be inspected, and FIG. 3 is the basic principle of the invention. FIG. 4 is a schematic cross-sectional view of the contact hole portion after etching treatment. In the figure, 1 is a silicon substrate, 2 is an inorganic glass film, and 3 is a silicon substrate.
4 is a contact hole, 4 is an electron beam, 5 is an electron-hole pair induced near the pn junction surface, 6 is a remaining film after etching, 7 is a flaky diffusion layer, 8 is an electrode pad, 9 is an ammeter, 1o
indicates a variable power supply. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (2)

[Claims] (1) By irradiating the etched region on the diffusion layer constituting the pn junction with an electron beam and detecting the electron beam induced current induced in the pn junction, the remaining after etching can be removed. An etching state inspection method characterized by inspecting a film state. (2) A structure of a pattern to be inspected that constitutes a pn junction and is characterized in that an electrode pad is formed on a diffusion layer extending from directly below the portion to be etched.