JPS5833855A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress an extraordinary crystal growth to occur on the surface of an aluminum film by inplanting Sn ions in the aluminum film at the substrate temperature of 150-400 deg.C. CONSTITUTION:An oxidized film 12, an n type diffused layer 13, an insulating film 14 and an aluminum film 15 are formed on a p type Si substrate 11. The film 15 is formed by a magnetron sputtering method at 250 deg.C of the substrate temperature. Then, Sn ions are inplanted in the film 15. After the film 15 is then formed in the prescribed wire pattern 15A, it is heat treated at 450 deg.C for approx. 30min. Subsequently, the PSG film is formed as an insulation protective film 16. Hillock is prevented from producing by inplanting the Sn ions.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming highly reliable metal thin film wiring.

In semiconductor devices such as integrated circuits, metal thin films, such as aluminum thin films, are widely used to form film wiring for inter-element connections. Aluminum can easily form ohmic connections with semiconductors. and good adhesion.
It has advantages such as easy processing and low electrical resistance. However, in general, after forming aluminum thin film wiring, there is a heating process at a temperature of 40G to 500°C to obtain a good contact with the semiconductor substrate, and a temperature raising process to form an insulating film. During these steps, abnormal crystal growth of aluminum occurs, resulting in surface protrusions called hillocks. Conventionally, the occurrence of hillocks has been a major factor in deteriorating the reliability of semiconductor devices. That is, in the case of an insulating film covering wiring or a multilayer wiring structure, a hole or breakage occurs in the interlayer insulating film etc. due to hillocks. These have been the cause of so-called /arm seal failures and interlayer leaks. In addition, as devices become smaller and wiring widths become narrower, the presence of hillocks with a diameter equal to or several times smaller than narrow wiring is a sign of the uniformity of current flow in the wiring. This has become a serious problem in terms of energizing life.

Furthermore, in the photolithography process for forming fine wiring, particularly in the exposure transfer process 11 for the wiring mask/middle turn photoresist layer, strict flatness of the photoresist substrate surface is required. In this case, if the specified flatness is not achieved, the transferred image will blur, making it impossible to form precise patterns. Further, when forming a multilayer wiring structure, the presence of hillocks in the lower thin film wiring layer adversely affects through-hole processing during the formation of the upper thin film wiring.

The present inventors have previously proposed a method for manufacturing an in-film conductor device using a nine-hillock suppression method using ion implantation, that is, after forming an aluminum thin film, neon ( N.), Arnon (Ar), Krypton (Kr)
) Due to the ion implantation of specified amounts of rare gas elements such as boron (B), arsenic (As), phosphorus (P), silicon (si), etc., hillocks may occur during the subsequent thermal process. It was clear that K could be significantly suppressed. However, subsequent studies have shown that the effect of suppressing the occurrence of hillocks due to the ion implantation of the above elements is limited when the substrate temperature is between room temperature and 15°C.
It was found that the effect was noticeable only when the aluminum was deposited at a temperature of 0° C., and almost no effect was observed for aluminum deposited at a substrate temperature of 150 tl or higher.

An object of the present invention is to provide a method for obtaining metal wiring that effectively suppresses the occurrence of cracks and cracks using a metal film containing aluminum as a main component and formed at a substrate temperature of 150°C or higher and 400°C or lower. .

In the present invention, after forming a metal film mainly composed of aluminum on a substrate set at a temperature of 150°C to 400°C,
The present invention is characterized in that by ion-implanting tin element (8m) into the metal film, occurrence of cracks and etchants in subsequent thermal processes is suppressed.

The physical *ms of the present invention will be explained below using drawings!
1111 vA (a) is, for example, a predetermined O active element on a pm silicon substrate 11 with a specific resistance of 10 Ω-1. Oxidation, diffusion,
Oxide film 1 is formed through processes such as vapor deposition, vapor deposition, and photo-engraving.
2, nm diffusion layer 13, insulating film 14, aluminum M15
It is a process sectional view at the time of forming. The type II scattering layer 13 is formed by phosphorus diffusion in an opening provided in a predetermined region of the oxide film 12, but in reality, in the case of an integrated circuit, things with different areas are uniformly formed. A large number of them are formed and constitute part of an active element or a passive element. In addition, aluminum Ell 5Fi is formed on the entire surface of the substrate so as to contact the n-type diffusion layer 13 and cover the insulating film 14 in an opening formed in a predetermined area of the insulation IMza on the substrate including the top of the n-type diffusion layer 13. In this embodiment, the aluminum film 15 is formed to a thickness of 0.81 sa by the Madanetron Suno or Tsuta method at a substrate temperature of ~25 G°C. Furthermore, in this example, 99.9999% pure aluminum is used as the vapor deposition material; however, depending on the purpose, an aluminum alloy material containing silicon, steel, etc. may be used.After this, in step (b), Into the aluminum film 15, tin ions (8n ions are implanted at an implantation amount of 3×1015/- at an acceleration energy of 110 @V).Subsequently, in step (c), the aluminum film 15 is etched by photolithography.
After forming the predetermined wiring no-turn IIAK processing, 11
Heat treatment is performed at 450° C. for about 30 minutes to obtain ohmic contact with the ill diffusion layer 13fC. If the above-mentioned ion implantation is not performed, hillocks will normally grow on the aluminum film wiring 4 turn 151 during this thermal process.
Large ones reach 1 to 2 fine pieces. In the case of this example, there was no occurrence of such hillocks. Next, in the step (d), PEG (Phoapho-St l l@
at@-Glams) film is formed as the insulating protective film 16. The PEG film is formed by chemical vapor deposition, but in this case the substrate temperature is 400-500°C! It becomes degree. However, no abnormal growth of hillocks occurred during this thermal process. When we conducted a wiring corrosion test by energizing under high temperature and high humidity conditions, we found that no defects occurred at all.

Incidentally, after the step (d), a step of forming holes in the insulating protective film 16, a wire pattern, etc. are usually added to form the I/Dings conductor device to manufacture the medium conductor device. .

Next, an embodiment in which the present invention is applied to forming wiring in a two-layer structure will be described with reference to FIGS. 2(a) to 2(f). First, at the time of step (a), a thermally oxidized N11xx having a thickness of ~1JII111 is formed on a predetermined silicon substrate 11, and an aluminum film 23 containing silicon with a weight composition ratio of ~1.5916 is formed on the thermally oxidized N11xx. Thickness ~1 sm using magnetron sputtering at substrate temperature ~200°C
IIC deposition is formed. Next, in step (b), acceleration energy s, af − is applied to the entire surface of the aluminum group 23.
Tin ions (an'') are implanted at 100&V and an implantation amount of 4 x 1015 ions/d.Next, in the step (,), the above 7
In the step (d), a silicon oxide film, which will become an interlayer insulating film, is formed on the substrate metal including the surface of the aluminum arranged IA turns 23A. 24 is formed to a thickness of ~α6 μm by vapor deposition, and then holes 25 for interlayer connection are formed in predetermined areas by photolithography. The above-mentioned interlayer insulating film may be a silicon nitride film in addition to a silicon oxide film, and the method for forming them is a vapor deposition method. Any method such as a plasma deposition method may be used. Normally, when forming these insulating films, the substrate is heated to 300 to 500°C, but in this example, no abnormal growth of hillocks occurred on the aluminum wiring/turf even during the heating process. Next, in the (-) step, the weight composition ratio is 1.0 as the second layer wiring material film.
Aluminum M26 containing 5% silicon was heated to a substrate temperature of 2.
00'CK''C Thickness ~ 1 μmK, formed by magnetron sputtering method. At this time, if necessary, two-layer aluminum film 26 is formed at substrate temperature 20° C. to thickness ~1 μm by magnetron sputtering method. At this time, if necessary, tin ions are implanted into the second layer of aluminum film J16 in the same manner as in step (b).Then, in step (f),
Aluminum M2c is processed using an ordinary photolithography method to form second-layer wiring pattern turns j6A and JOB.

The final shape obtained through the above steps is such that it is possible to measure the withstand voltage, leakage current, etc. between the wiring layers by examining the area between the wiring/arm turns 26A and 26B. As a result of actually measuring voltage short circuits and the like with the above structure, there was no glabellar short circuit, and a significant improvement in the breakdown voltage distribution 4 was observed.

As described in the above examples, the suppression of hillocks on the aluminum heated vapor deposited film by the method of the present invention led to significant improvements in corrosion tests and pressure tests. The appearance of hillocks was actually evaluated using a surface roughness needle. A thermal oxidation layer is formed on a silicon substrate to a thickness of ~1 field, and an aluminum film containing silicon at a weight composition ratio of i, s% is deposited on the entire surface of the thermal oxide film to a thickness of 250°C at a substrate temperature. ~1
．． Formed into itm. This sample was heat treated at 500° C. for 40 minutes, which is a severe heat treatment condition (compared to a normal process), and the surface condition was examined. Figure 3 (a) shows the case in which ion implantation is not performed into the FiAlZnium film, and (b) shows the case in which tin ions (liim" ) 3X1G15 pieces/c
These are the results of Cts surface roughness after heat treatment in case of d injection. (a).

The effect of the present invention is also clear from the comparison of (b).

As a result of microscopic observation of mold, the above ion-implanted Al1=
It was found that many fine protrusions were generated on the surface of the Kumu thin film after heat treatment.

From this, it can be interpreted that the effect of ion implantation into the aluminum film is to form a large number of hillocks near the surface of the thin film, generate many small hillocks during heat treatment, and suppress the formation of large hillocks. It can be considered that the effects of the present invention are produced by generating a large number of minute hillocks and ensuring macroscopic flatness of the aluminum film surface.

In the case of an aluminum film deposited on a substrate kept near room temperature, ion implantation of various elements including rare gas elements is performed as described above to suppress the occurrence of hillocks in the subsequent thermal process. Gadeti9. As for the aluminum vapor deposition film on the substrate heated to the temperature of 150℃ to 400℃, various studies have been conducted, and at present, tin element (Jiim) is used.
It has been found that only ion implantation of is shown to have a significant effect on hillock suppression. 99.999 mentioned in the example
9% purity O Al 1 thin film and weight composition ~1.5%
Any aluminum thin film containing elements such as silicon, copper, rumanium, nickel, iron, etc., or containing multiple types of these elements up to several percent by weight composition, including aluminum thin films containing silicon. The above-mentioned hillock suppressing effect was also confirmed. After ion-implanting tin element (Jim) into these thermally vapor-deposited thin films containing aluminum in the same manner as in the above examples, the melting point of the aluminum film (~600 ℃) It has also been confirmed that it has the above-mentioned hillock suppressing effect. In addition, in the above embodiment, acceleration energy of 100 to
Tin ions (8m") were implanted at 110x@v, but the distribution of tin in the aluminum film after implantation was such that the thickness of the aluminum film was only 6G0A@degrees deep from the surface. In order to produce the effect of suppressing hillocks as in the present invention, it is sufficient to ion-implant tin element (Sn) only near the surface of the aluminum film; It is not necessary to form a tin ion-implanted layer.Experiments have shown that if tin ions are implanted from the center to a deeper region along the thickness of the aluminum film, the hillock suppression effect cannot be achieved. Therefore, when ion-implanting tin element, the implantation energy needs to be selected appropriately so as to form a distribution of implanted ions in a region including the vicinity of the surface, depending on the thickness of the aluminum film that is the material to be implanted. There is 1.
+, the amount of tin element to be implanted into the aluminum film is 1
The range of ×1014 to lX1017 pieces/cd was good, and the effect of suppressing hillocks was remarkable in the range of I×10” to I×1 G” pieces/ado. In the above embodiment, the tin element ion implantation process was performed before the aluminum wiring pattern formation process, but it is of course possible to implant tin element ions into the aluminum film wiring after the ΔT pattern is formed. In general, the heroism of aluminum film is 1.
Hillocks are caused by a heating process near 00°C, but the density and size of hillocks increase as the heating temperature increases.

Hillocks that occur due to heating above 200°C are used in manufacturing various semiconductor devices including integrated circuits. Ion implantation of the tin element is the first step of the present invention.

As described above, according to the present invention, a predetermined amount of tin element (8 m
) is added before the subsequent thermal process that may cause hillocks), it is possible to suppress abnormal crystal growth that occurs on the surface of the aluminum film due to hillocks. By suppressing the occurrence of hillocks, it has become possible to significantly improve interlayer breakdown voltage during wiring corrosion, as described in the embodiments, and to form precise '&Δ turns during photolithography. Further, according to the present invention, by suppressing the occurrence of hillocks, the current life of the wiring can be extended, which can greatly contribute to improving the reliability of each semiconductor device.

[Brief explanation of the drawing]

Figures 1 (1) to (d) are process sectional views for explaining one embodiment of the present invention, and Figures 2 (,) to (f) are process sectional views for explaining other embodiments. , Figure 3 (a), (b)
FIG. 2 is a characteristic diagram for explaining the effects of the embodiment of the present invention. 11...1ml silicon substrate, 12...oxide film, J
J...1Ml diffusion layer, 14...insulating film, 15...aluminum film, 151 aluminum film arrangement! Id turn, 1e...insulating protective film, 2no...silicon substrate, 2
2... Oxide film, 23... Aluminum film, 2smu.
...Aluminum wiring/4 turns, 24...Silicon oxide film, 25...Open hole, 26 Aluminum film, Jg
A, JgB... Aluminum film wiring pattern. Applicant's representative Patent attorney Takeshi Suzue Figure 2 Figure 3 1-100pm-1 1-100pm-1

Claims (1)

[Claims] Manufacture of semiconductor devices in which a metal film mainly composed of aluminum is formed on a semiconductor substrate at a substrate temperature of 150°C to 400°C, and after this metal film is processed into wiring and arm turns, a heat process of 200°C or higher is applied. In the method, after forming the metal film and before applying the heat process at 200°C or higher,
. A method for manufacturing a semiconductor device, comprising the step of ion-implanting a tin element into the metal film.