JPS6336993A - Laser beam processing method - Google Patents

Abstract

PURPOSE:To prevent the damage of wirings and to reduce an initial cost by allowing a laser light transmittable material to remain on a high reflectivity conductive material, then projecting laser light to the material in a gaseous material atmosphere state. CONSTITUTION:A semiconductor integrated circuit is successively formed with the Al wirings 2 and protective film 3 (SiO2) on a substrate 1. Through-holes 4 are first formed by etching or ion beam processing, etc., to the protective film 3 on the Al wirings 2 to be connected. The protective film 3 is made to remain on the peripheral edge of the Al wiring 2 at this time to decrease the reflectivity of the Al wirings 2 to the wavelength of the laser light. Such integrated circuit is then disposed in the gaseous material atmosphere of Al(CH3)3, etc., and the laser light 5 is projected thereto. The conductive material 6 is deposited by the heating in the remaining part of the protective film 3 and fills the through-holes 4 up to the upper part thereof. The damage of the Al wirings 2 by the laser light is prevented and the initial cost is reduced by the above-mentioned method.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the manufacturing of semiconductor integrated circuits, and in particular, for debugging integrated circuits, fine holes are made in the integrated circuit and a conductive material is embedded in the integrated circuit. Concerning how to repair wiring.

[Conventional technology]

The development of semiconductor integrated circuits takes a relatively long time from the basic study stage to the realization of actual devices. Particularly in the later stages of development, it is common practice to mount and test devices, and then change logic.

Conventionally, such a logic change has been carried out by changing the wiring as well as changing the exposure mask for manufacturing the semiconductor device, and then remanufacturing the device itself through a series of subsequent device manufacturing processes.

In order to quickly change this logic, the inventor of the present invention came up with the idea of processing the wiring itself formed in the integrated circuit. To this end, it is essential to have a technique for interconnecting the wirings formed in any part of the horizontal circuit by opening holes in the protective film and insulating film covering the wirings and filling them with a conductive material.

Laser CVD (Chpmtcal Vqp) is a technology for filling minute holes (through holes) with conductive material.
or Depotitior: Chemical Pahate Position) is used. For example, JP-A-59-119
No. 853 discloses that Al(C4H9)3 or S-type H4 is etched into through holes of 2.5 square microns formed by dry etching technology in a PSG film with a thickness of 2 μm on a semiconductor substrate using an Ar laser or a CO2 laser. A method of filling silicon or polysilicon from material gases such as

It is said that a photochemical reaction without using high heat is effective when filling with Al, and a thermochemical reaction is effective when filling with polysilicon because silicon can withstand high heat.

[Problem that the invention seeks to solve]

The purpose of the above-mentioned prior art is to form through holes in an insulating film formed on a semiconductor substrate and to fill them with a conductive material. For this reason, thermal considerations are not taken into consideration, and when processing actual integrated circuits, the lower layer of the through hole may be damaged.

41 is often used for wiring in integrated circuits,
The melting point of Ai is about 660°C. Also, the laser light (e.g. laser with a wavelength of 515 nm, 1.06 μm)
The reflectance of Al with respect to the YAG laser of 10.6 μm and the CO2 laser of 10.6 μm is both above 90%μ. Therefore, if a thermochemical reaction is to be caused by laser beam irradiation in order to fill the through holes on the Al wiring, which is the object of processing in the present invention, with a conductive material, high-output laser beams are required. This laser beam is placed at the bottom of the through hole. 4
If one wiring is irradiated in a material gas atmosphere, the Al wiring will melt and bump and break at the moment a conductive substance is deposited on the Al wiring. This is because the conductive material involved in the deposition has a lower reflectance than the Al wiring with respect to the laser beam. That is, when an Al wiring is heated to a temperature higher than the decomposition temperature of the material gas with a laser beam, a conductive substance with a low reflectance is precipitated, and absorption of the laser beam occurs rapidly, burning out the Al wiring together with the precipitated conductive substance. This is thought to be because it ends up happening.

On the other hand, the laser light output was narrowed down and irradiated onto the Al wiring.4
No electrolytic substances are deposited. There is also a method of reducing the laser light output at the moment when the conductive substance is deposited, but this method requires a more complicated device configuration than the present invention.

According to experiments conducted by the inventor of the present application, no change in appearance was observed even when Al wiring was irradiated with an Ar laser beam having a wavelength of 515 rzm for 50 seconds at an output of 0.4 F in a vacuum. N again.

(CO)6 gas atmosphere (gas pressure approximately 0.05 Torr)
) to reduce ArV-the light to 0. No change in appearance was observed even when irradiated for 5 seconds at IF output, but damage occurred to the Al wiring when irradiated for 1 second at 0.2F output. M
The reflectance of No, which also precipitates o(CO)6, to Ar laser light is about 20%, which is significantly lower than 90% of Al wiring.

For this reason, the aforementioned V-za light is rapidly absorbed, leading to disconnection of the wiring.

An object of the present invention is to fill the through-hole with a conductive material without damaging the base of the through-hole.

- [Means for solving the problem] The above problem can be achieved by leaving a protective film or an insulating film on the Al wiring to reduce the reflectance of laser light (C).

In the embodiment, the protective film is made of Al in consideration of forming through holes in the protective film on the Al wiring.

The wiring remains on the exposed periphery. The residue may be in the center of said exposed portion.

[Effect]

The thin film remaining at the bottom of the through-hole acts as an anti-reflection film, so the periphery or center of the Al wiring is coated with Al.
The reflectance of the wiring to laser light is reduced.

As a result, the laser light is sufficiently absorbed, and even low-power laser light can heat the Al wiring above the decomposition humidity of the material gas, without damaging the Al distribution area. It becomes possible to fill the

〔Example〕

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

1 and 2 are diagrams illustrating the implementation process of the method according to the present invention.

In a semiconductor integrated circuit, an All wiring 2 and a protective film 3 (5i02) are sequentially formed on a substrate 1 (see Fig. 1 (α)).
)).

First, four through holes are formed in the protective film 3 on the All wiring 2 to be connected by etching or ion beam processing. At that time, the AI2I2 wiring 2nd protective film 3 is left (Fig. 1(b)), and the All
Leave the protective film 3 at a thickness that reduces the reflectance for two wires.

This process may be performed using a processing device having a plurality of vacuum chambers separated by gate valves, or
The process may also be carried out using a vacuum device capable of batch processing dedicated to through-hole formation.

The following integrated circuit includes Al(CH3)3, Cd(
CH3) 3, MO(CO)6, F((?0)
6 or SiH4, etc., and a laser beam 5 is irradiated thereon. Through hole 4 is irradiated with laser beam 5.
The Al plate 2 at the bottom of the plate is heated, but the remaining portion of the protective film 3 absorbs the laser beam 5 to a large extent.
The exposed portion of the Al wiring 2 is heated to a high temperature, and heat is applied to the exposed portion of the Al wiring 2. As a result, these parts become higher than the decomposition temperature of the material gas, and the conductive material 6, for example, Al
, Cd, No.

W, polysilicone begins to precipitate.

The reflectance of the conductive substance 6 itself that has begun to precipitate is smaller than that of the 1, 41 wiring 2, and therefore is heated to a temperature sufficient to absorb the laser beam well and decompose the material gas. When the conductive substance is deposited to the top of the through hole, the laser beam irradiation is stopped (FIG. 1(C)), and the material is taken out from the material gas atmosphere.

Through the above steps, the through holes are filled with a conductive material. Such a process may be accomplished in a dedicated batch processing vacuum device, or, if the usage is high, in a single vacuum device separated from the through-hole forming vacuum device via a gate valve. It may be done.

The semiconductor device in FIG. 2 has an All wiring 2 on a substrate 1.
, Insulating film (543N4) 7 + Protective film (Si02)
3 are formed in sequence (FIG. 2(α)), and first, through holes 4 are formed by etching or ion beam processing (FIG. 2(b)). Here, the insulating film 7
remains on the exposed periphery of the Al wiring 20, and the Al wiring 2
It works to reduce the reflectance of laser light (as described above).

Next, the laser beam 5 is irradiated in a material gas atmosphere to fill the through hole 4 with a conductive substance 6 (Fig. 2 (C)).
.

In the above embodiments, the thickness of the protective film 3 or the insulating film 7 to be left on the exposed peripheral portion of the Al wiring 20 is determined, for example, with reference to FIG.

Figure 3 shows that when using an Ar laser with a wavelength of 515 lumens,
This shows how the reflectance changes depending on the film thickness of the material.

By setting the protective film 3 to 70rLrn and the insulating film 7 to about 45+zm, the dust can be reduced to about 80% and 70%, respectively, for the All wiring 2. Note that the protective film 3 and The thickness of the insulating film 7 varies depending on the wavelength of the laser light 50 used, and may be appropriately selected accordingly.

02g4 and 5 show a method of forming a through hole 4 with the film thickness as described above in the peripheral portion of the Al wiring 20 where the protective film 3 or the insulating film 7 is exposed. is a combination of anisotropic etching and isotropic etching. In these embodiments, first, through-holes 4 are formed by anisotropic etching so that several tens to hundreds of nanometers of the protective film 31 on the Al wiring 2 remain (FIG. 4(a)). Alternatively, the through hole 4 is formed up to the boundary with the insulating film 7 (Fig. 5 (σ)).
. Thereafter, the remaining protective film 3 or insulating film 7 is removed by isotropic etching until the central portion of the Al wiring 2 is exposed. As a result, the centrifugal membrane 3 and the insulating film 7 at the peripheral portion where the Al wiring 2 is exposed remain in a shape in which the thickness increases continuously toward the outside (FIG. 4(b) or FIG. 5(h)). .

A specific example of anisotropic etching is RIE (reactive ion etching).
n EtcAirLq ) and microwave ECR method (electron cyclotron resonance method: Elec
tronCyclotron Rgson. ance
) etc. are known. On the other hand, a specific example of isotropic etching is a wet etching method using various etching solutions. As etching solutions, a mixed solution of NH4F and HF is known for St and O2, and a solution of H3PO4 is known for S3N4.

6 to 8 show a method of forming through holes using a focused ion beam. Example of FIG. 6: (Then, the protective film 3 on the Al wiring 2 is removed to an appropriate depth using an ion beam 8 with a small spot diameter to form a through hole 4 (FIG. 6 (α)). After that, , the portion where the Al wiring 2 is to be exposed is irradiated with the ion beam having a small spot diameter, and the peripheral portion is irradiated with the ion beam 8, the spot diameter of which increases as it goes outward.When the ion beam current is constant, the spot diameter is As the ion beam current density becomes smaller, the processing speed increases.
), the thickness of the protective film 3 increases toward the outside of the peripheral edge. This method can be used even if the insulating film 7 is formed on the Al wiring 2 at a temperature of .degree.

The embodiment shown in FIG.
A through hole is formed while mass spectrometry is performed on the next ion. In the same figure, when the amount of nitrogen ions from the insulating film 7 is detected to be more than a certain value with respect to the amount of oxygen ions from the protective film 3, it is regarded as the boundary between the protective film 3 and the insulating film 7,
The protective film 3 is removed until that value is obtained (FIG. 7(a)).

Then, the insulating film 7 is removed until the reflectance of the Al wiring 2 to the laser beam 5 becomes the lowest film thickness (FIG. 7(h)).
). Thereafter, the insulation 7 is removed until the Al wiring 2 is exposed. At this time, similarly to the above, mass spectrometry is performed for the violet 9 ions from the insulating film 7 and the aluminum ions from the All wiring 2 (FIG. 7(C)). Like this 2
If ion beam processing is performed while performing quality 1 analysis of the next ion, processing accuracy in the depth direction will be improved.

In the embodiment shown in FIG. 8, as in the embodiment shown in FIG. 7, the through hole 4 is formed while performing mass spectrometry on secondary ions.1. The processing procedure up to the boundary between the protective film 3 and the insulating film 7 shown in Figure 81 (α) is the same as the embodiment shown in FIG. After that, the scanning area of the ion beam 8 is narrowed in stages <t, -C.
Insulating film 7? Process for removal. Then, as in the embodiment shown in FIG. 7, when aluminum ions are detected relative to nitrogen ions over a certain value, it is determined that the Al wiring 2 is exposed, and processing is stopped (FIG. 8(b)).

As mentioned above, the cross-sectional shape of the exposed peripheral part of A15'42 is as shown in Figures 6 and 8 from No. 41. , as shown in Fig. 7, the temperature is constant and the temperature is good at 1°C. However, if the film thickness is not constant, the part of the Al wiring 2 with a low opposition rate to the laser beam 5 has a certain temperature for anti-reflection. If it is i drop (
(Of course, it is narrower in comparison.

In the inventor's experiment, an Al wiring with a thickness of 1 μm was formed on the substrate.
jiu i￥15Q n, m? '-1iff C5
i 3#4) + fil F20.5am protective film (5LQ2)'' - 2μ for the conventionally formed semiconductor device
Form a through hole as large as m x 3 μm (7 Ig), and
family gas r'hfo(Co)6 (gas pressure = Q, l T
When the above through hole j (-4r laser beam was irradiated with a power of 2Q+nF) using
A man's light for a second! 11O was precipitated in Village I Terama.

1) Ilf himself did not have any natural, secondary forces.

In the previous explanation, a crushing film or an insulating film was left on the periphery of the exposed Al wiring in order to reduce the reflectance of the Al wiring to the laser beam, but this is not limited to this. As shown, a protective film 3 or an insulating film (not shown) is left in the center of the exposed Al wiring 2 and the temperature is good. The cross-sectional shape of the remaining film can be one in which the film thickness is continuously changed as shown in Figure 4, or one in which the film thickness is constant as shown in Figure 7. , 8th
Any film whose thickness is changed stepwise as shown in the figure may be used. Furthermore, it may be provided both at the center and at the periphery of the exposed Al wiring 2.

〔Effect of the invention〕

As explained above, according to the present invention (C), since the conductive material is filled in the through hole with a low power laser beam, there is no damage to the Al wiring.
Not only the wiring, but also a wiring having a high reflectance for the laser beam used is very effective. The story of the excavation of the most powerful laser in history! Since the contact surface is the striking surface, it has the effect of expanding the range of choices regarding the output performance of optical elements such as lenses and mirrors, and has the effect of reducing the cost of the equipment including the laser oscillator.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing the process of implementing the method according to the present invention for depositing a conductive material on a wiring having a protective film, and FIG.
The figure is a conceptual diagram corresponding to Figure 1 when processing a wiring with a protective film via an insulating film, and Figure 3 is the film thickness and reflectance of a protective film or insulating film formed on an aluminum wiring. Figures 4 and 5, which show the relationship between the two, are wirings each having a protective film. An illustrative diagram showing that the process of FIGS. 1 and 2 is achieved by applying anisotropic etching and isotropic etching to a wiring having a protective film through an insulating film. FIG. 6 shows a wiring having a protective film. For wiring, a focused ion beam is used to achieve the process shown in Figure 1. Figure 7 is an example diagram showing how to achieve the process shown in Figure 1 using a focused ion beam. An illustrative diagram showing the remaining process,
Figure 8 shows wiring that has a protective film through an insulating film.
An illustrative diagram showing the use of a focused ion beam to accomplish the process of FIG. 2, and FIG. 9 is a conceptual diagram illustrating another process for carrying out the method according to the invention. 1... Board, 2... Washing wiring, 3...
・Hot F8M, 4...Through hole, 5・
... Laser light, 6... I-conducting substance, 7.
...Insulating film, 8...Ion beam.

Claims (1)

[Claims] 1. Regarding a processing object in which a conductive material having a high reflectance with respect to the laser beam to be irradiated is covered with a substance that transmits the laser beam, the material that transmits the laser beam is A film having a thickness that prevents reflection is left partially on the conductive material having a high reflectance, a material gas atmosphere is created around the workpiece for attaching the conductive substance, and the laser beam is applied to the workpiece. A laser processing method that irradiates the laser beam onto a portion where a transmitting substance remains. 2. In the laser processing method according to claim 1, the object to be processed is a semiconductor integrated circuit, and the material that transmits the laser beam is a SiO_2 film or S.
i_3N_4 film, and the conductive material with high reflectance is Al wiring.