JPS6348845A - Thin film device and formation thereof - Google Patents

Abstract

PURPOSE:To prevent breakdown of Al wiring film and to obtain the Al wiring film having low resistivity, by a constitution, in which C is included in Al, as a metal wiring film, and forming the metal wiring film in plasma, which includes at least Al and C. CONSTITUTION:This device comprises an Si substrate 1, a diffused layer 2, an SiO2 oxide film 3 and an Al wiring film 4 including C. When the film is formed by a plasma CVD method, e.g., an Si wafer 11 is placed in a parallel- flat-plate type plasma chamber 10, in which a vacuum state is provided, trimethyl Al gas is dilluted with hydrogen gas and the gas is introduced in the chamber 10 through a shower state nozzle 14 of an upper electrode. At this time, the trimethyl Al is cooled to about 5 deg.C, which is lower than a melting point (15 deg.C), and used. For the metal wiring film 4, Al is formed at a temperature less than a thermal decomposition temperature (i. e., a temperature, where Al is not condensed). Thereafter, heat treatment is performed. The concentration in the Al film is controlled by changing RF power and the amount of dilluting H2. The concentration of carbon is more than solid solution limit and less than 20%. The carbon is present in a chemically bonded state as Al-C in the aluminum.

Description

Detailed Description of the Invention (Summary) The present invention provides a thin film device and a method for forming the same.
- In order to solve the problem of conventional devices in which the A2 wiring film breaks due to electromigration, etc., by containing a small amount of carbon, electromigration is small, hillocks (protrusions) do not occur, and the A2 wiring film is In addition, by forming the A2 wiring film by the plasma CVD method using a magnetic field, the A2 wiring film has a good A e -C bonding state and has a low specific resistance. It was designed so that it could be formed.

[Industrial Application Field] The present invention relates to a thin film device, particularly a thin film device using an A2 wiring film, and a method for forming the same. In a thin film device, the A2 wiring film may be disconnected if electromigration or hillocks occur, so there is a need for a highly reliable thin film device that suppresses these phenomena and does not cause disconnection of the A2 wiring film.

[Conventional technology]

An IC is formed by forming elements on a semiconductor substrate and connecting them with metal wiring. In this case, with the development of highly integrated ICs, there is a tendency for elements and wiring to be miniaturized, but currently, the configuration of the wiring is limiting the degree of integration.

[Problem that the invention seeks to solve]

Wiring films tend to be multilayered as they become finer, and this causes problems such as disconnections at stepped portions, failures due to electromigration due to increased flow density, and short circuits between layers due to the formation of hillocks. All of these are caused by the fact that Au atoms are easy to migrate, and even heat treatment alone without current flow causes migration and disconnection of the wiring film.

In order to eliminate these problems, attempts have been made to add Cu, 3i, etc. to the Afl wiring film to form an alloy. However, there are problems with workability due to the residue during etching, and the added 3i is removed by heat treatment. There is a problem in that contact resistance increases due to in-phase epitaxial growth in the contact portion. Furthermore, the reaction between the wiring material and the 3i substrate or barrier metal layer.

There is also the problem that it may penetrate through the diffusion layer due to intrusion or the like and short-circuit the junction.

As described above, the current situation is that the problem of reduced reliability of the A2 wiring film is becoming more serious with the miniaturization of ICs.

[Means for solving problems]

The metal wiring film has a structure in which C is contained in A2, and
At least A2. In a plasma containing C, the metal arrangement I! 2
Forms a film.

[Effect]

By including C in A2, electromigration and hillocks do not occur, and A[1'! By forming a wire film, a cross section of A with a good bonding state of Al-C and low specific resistance is formed and V is formed. In the figure, 1 is a 3i substrate, 2 is a diffusion layer, 3 is an St2 oxide film, and 4 is an A4 wiring film containing C, which is a main part of the present invention.

Here, a method of mixing C into Al will be explained. A
When C is doped into this film by ion implantation, 0.
C precipitates during heat treatment at 6450° C., where the specific resistance gradually increases when 1% or more is implanted.

This is because C and A2 are not in a bonded state, so the eigenlimit (0
, 1%) or more may precipitate during heat treatment.

Therefore, in the state where Al and C are combined, AI! .

As a result of introducing C into the film, it was found that no C was precipitated even after heat treatment. However, in this case, I3 of C
When rg exceeds a certain value, the resistance increases exponentially, making it impossible to use it as a wiring.

Figure 2 shows the C concentration in the bound state (C/ (AJll10))
FIG. 3 is a diagram showing the change in specific resistance when changing the resistance before and after the heat treatment. As is clear from the figure (, heat treatment 1
! It can be seen that there is almost no increase in resistivity if the temperature is 20% or less for both the heat treatment and after the heat treatment, and that the resistivity is reduced to 1/2 by heat treatment at 450 °C.

As a result of X-ray measurement, it was found that the A2 film mixed with C had oriented microcrystals (grain size of about 20 na before heat treatment of the A2 film by plasma CVD method), and C entered the grain boundaries. It is possible that

Therefore, even during heat treatment, migration of A2 atoms is suppressed and crystal growth does not occur rapidly (600℃, 30℃
(The grain size becomes 40 nm after heat treatment for 30 minutes), and electromigration accompanying an increase in current density is also suppressed, and hillocks do not occur. In particular, there were no hillocks even during heat treatment at 600°C (400°C for those without C).
hillocks occur during heat treatment), it has excellent properties not found in the A2 film of conventional equipment. In this case, the bonding state between C and A atoms was measured using an X-ray photoelectron analyzer, and it was confirmed that they were completely chemically bonded. The present invention is characterized by containing carbon in a bonded state in the microcrystals, and since the wiring width is 1 μm or less, the crystal grain size of 1100 nm or less means that it is compact in order to realize even thinner wiring. be.

By the way, S: It is necessary to form a contact in order to make an electrical connection with the element formed on the substrate.
A of 3i, which has traditionally been a problem in this contact
In the case of the present invention, the intrusion into the e 110 is solved by pre-mixing Si into the AIQ. Further, since the migration of Si in the 3i substrate 1 is also limited by the film of the wiring 4, there is little in-phase epitaxial growth on the contact portion, and submicron contact holes are also formed with low contact resistance. In this case, 3
If i is mixed in, precipitation will occur, so it is necessary to keep the content below this value.

Next, the plasma CVD method employed in the present invention will be explained. Generally, in the thermal CVD method in which a source gas is decomposed by heat to form an A2 layer, the formed AlrlA surface has severe irregularities. Even in the plasma CVD method adopted in the present invention, thermal CVD occurs if the film is formed at a temperature higher than that at which thermal decomposition occurs.
Similar to method D, unevenness is produced on the surface of the A2 film. This is A2
It is thought that this occurs due to the large cohesive force of , and is an unavoidable problem in the thermal CVD method.

Therefore, in the present invention, by exciting organometallic gas etc. with plasma to promote dissociation and bonding reactions, A2
form. This can be achieved by using plasma.
This is advantageous because the E-C bond is complete.

FIG. 3 shows a diagram illustrating film formation by plasma CVD method. As shown in FIG. 3, a Si tube 1 is placed in a parallel plate type plasma chamber 10 that is evacuated, and 13.5
A heater 13 is installed outside the chamber 10 below the 6 MHz RF oscillation power source 12 and the Si wafer 11. Organometallic trimethyl A2 (AE(Cth)3) < TMA
) The gas is diluted with hydrogen gas and introduced into the chamber 10 through a shower-like nozzle 14 with an upper 1 g K pole. in this case,
Trimedel A is used after being cooled to about 5°C below the melting point (15°C).

Here, a diagram of etching time versus intensity characteristics is shown in FIG.

The conditions are: R "power 1 kW, pressure 4.5T o
rr, the heat treatment temperature was 450° C. and the time was 30 m1n. p! Before A treatment (solid line (H) and broken line (C)), not only C but also T1 (aqueous) is observed in the film, but 45
0℃ aspiration pl! It can be seen that after (two-dot chain line (1-1> and - dot-dashed line (C)), t1 decreases. This is because the film of heat treatment 1) η contains undecomposed CH3 groups. It is thought that this is because it disappears by heat treatment. Thus, it is necessary to perform heat treatment after deposition.

Note that the dashed line range near 103 (arbitrary unit) is the measurement limit.

Further, the C concentration in the A2 film can be controlled by changing the RF power and the amount of diluted H2. Figure 5 shows 112 dilution B.
A characteristic diagram of the product velocity versus JFT and specific resistance is shown.

In this case, it can be seen that if the dilution amount is not a certain value or more, not only the specific resistance is high but also the deposition rate is low. In other words,
The dilution 11zm needs to be about 60 times or more that of the carrier gas. As this carrier gas, in addition to organometallic gas (TMA gas), organometallic gas and silane gas (S
! A mixture of H4) may also be used.

Here, as the plasma CVD method, by using a plasma CVD method in which a magnetic field is applied to plasma, the reaction can be further promoted and a film with a small specific resistance can be produced in a thickness of 1q.

Next, what is the difference between a simple plasma CVD method (P-CVD method) and a method in which a magnetic field is added to plasma? CVD method (MP-CVD method) and pressure.

A comparison of film thickness, resistivity, and carbon concentration is shown in the following table. In addition, in the table, the values in parentheses are 450°C and 25°C.
This is the value after heat treatment of 1n.

According to this, it can be seen that the higher the gas pressure is within the range where plasma generation is stable, the higher the magnetic field is, the lower the specific resistance is. In this case, as shown in FIG. 9, the C concentration and resistivity can be lowered by controlling the magnetic field strength, and in particular, when the magnetic field strength is 200 G or more, the C concentration and resistivity can be lowered.

FIG. 6G, t A temperature-resistance characteristic diagram of the heat-treated TEL in the P-CVD method and the MP-CVD method J5 is not shown. As is clear from the figure, it can be seen that the plasma CVD method using heat treatment at 300° C. or higher and applying a magnetic field of 780 G is effective in reducing the resistivity.

FIG. 7 shows a graph of RF power versus deposition rate and resistivity characteristics in the p-cvo method. Although the deposition rate increases with increasing RF power, the resistivity changes uniquely. In other words,
If the RF power is too high, the deposition rate will be slow and the specific resistance will be low due to the relatively large amount of oxygen taken in. Furthermore, if the RF power is too high, a polymer will be formed (C content). too many) is inconvenient. Therefore, the RF power is preferably about 300W to 800W.

Furthermore, FIG. 8 shows cross-sectional views of films formed by the conventional CVD method and the present invention. The figure (△) shows conventional thermal CVD
method, the surface of the A2 film 20 is extremely uneven, and
In the same figure (B), a film formed by thermal bonding or sputtering was heat-treated at 450°C.
is occurring.

On the other hand, as in the method of the present invention, A2 containing C is 78
When formed by the plasma CVD method applying a magnetic field of 0 Gauss, no hillocks occur on the A2 film 23 even after heat treatment at 600°C, as shown in the same figure (C), and the A2 film becomes A2.
It shows high resistance to two-atom migration.

〔Effect of the invention〕

According to the present invention, since A2 contains C,
Electromigration can be suppressed, hillocks do not occur, and the i-line of the A2 wiring film can be prevented compared to conventional ones, and since the film is formed in plasma, the
Since the -C bond is perfect and A2 is formed in plasma to which a magnetic field is applied, it has the advantage that a film with low resistivity can be obtained.

[Brief explanation of drawings]

Fig. 1 is a sectional view of an embodiment of the device of the present invention, Fig. 2 is a graph of resistance versus carbon concentration according to the method of the present invention, Fig. 3 is a diagram illustrating film formation by the P-CVD method, and Fig. 4 is a diagram illustrating film formation by the P-CVD method. Etching time vs. strength characteristic diagram, Figure 5 shows hydrogen dilution vs. Figure 8 is a cross-sectional view of films formed by conventional and inventive CVD methods. Figure 9 is a graph of magnetic field strength vs. resistance and carbon 1α characteristics. In the figure, 1 is 81 1 is a substrate, 2 is a diffusion layer, 3 is a 5iOz film, 4.20 is a Δ2 wiring film, 10 is a chamber, 11 is a wafer, 12 is an R oscillation power source, 13 is a heater, and 14 is a shower-like nozzle. Figure P-CVD Rokushi L: Soaring wealth Pe 9th room Otshat T turn Figure 3 ←? ili!! Attachment (opponent side 4) Ippo Hyoushu Ban Ichiki Kozu, Hibiki - To HI YuI - Seventy-one

Claims (9)

[Claims] (1) A thin film device characterized in that the metal wiring film (4) contains carbon in aluminum. (2) the carbon has a concentration of not less than the solid solubility limit and not more than 20%;
2. The thin film device according to claim 1, wherein the thin film device contains aluminum in a chemically bonded state as Al-C. (3) The thin film device according to claim 1, wherein the metal wiring film (4) is made of the carbon-containing aluminum film further containing 2% or less silicon. (4) When forming the metal wiring film (4) of an aluminum film containing carbon or an aluminum film containing carbon and silicon, the metal wiring film is formed by keeping the temperature below the agglomeration temperature of aluminum, and then heated to 300°C. A method for forming a thin film device, characterized by performing the above heat treatment. (5) When forming the metal wiring film (4) of an aluminum film containing carbon or an aluminum film containing carbon and silicon, use plasma containing at least aluminum and carbon, or plasma containing at least aluminum, carbon, and silicon. 1. A method for forming a thin film device, characterized in that the thin film device is formed inside a thin film device. (6) The method for forming a thin film device according to claim 5, wherein the method for forming a thin film device using plasma includes dissociating the organic metal with plasma in hydrogen, or using silane gas at the same time. . (7) The method of forming with the plasma is (diluted hydrogen)/(
7. The method of forming a thin film device according to claim 6, wherein the ratio of the organic metal gas or a mixed gas of an organic metal gas and a silane gas is set to 60/1 or more. (8) The method for forming a thin film device according to claim 6 or 7, wherein the method for forming a thin film device using plasma is used in a state where the temperature of the organic metal is cooled to below the melting point. (9) Formation of a thin film device according to any one of claims 5 to 8, wherein the plasma forming method uses plasma in which a strong magnetic field is applied to the substrate surface. Method.