JPH07240412A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an aluminum wiring layer which does not easily generate electromigration even if the layer becomes thinner by depositing first an aluminum layer on an object substrate surface without positive heating of the substrate and then by depositing later the aluminum layer while the substrate is heated. CONSTITUTION:As a substrate 3 to form a film, a substrate which a Ti/TiN layer is formed on the surface is used and an aluminum layer is deposited by the sputtering on the Ti/TiN layer without heat treatment to the substrate. Subsequently, the substrate 3 is heated by flowing Ar gas heated up to 300 to 400 deg.C into a cavity of a substrate holder 4 and the aluminum layer is deposited. As explained above, an aluminum layer having a large grain size and high orientation (111) can be deposited by heating the substrate during deposition of aluminum layer and generation of electromigration can be suppressed even when the film becomes thinner. Moreover, deposition without heating of substrate and deposition with heating of substrate are continued within the same vacuum vessel to maintain a higher throughput.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to an Al having a pattern width of submicron order.
The present invention relates to a method of manufacturing an integrated circuit using wiring.

[0002]

2. Description of the Related Art Electromigration of Al atoms causes disconnection of aluminum wiring. It is known that increasing the grain size of Al is effective for preventing the occurrence of electromigration. In order to increase the grain size of Al, the substrate temperature during deposition of the Al layer by sputtering is usually 200.
It was set at about 350 ° C.

[0003]

With the progress of integration of integrated circuits and multilayer wiring layers, the film thickness of the first Al wiring layer has become thinner. As the film thickness of the Al wiring layer becomes thinner, the current density flowing through the Al wiring increases. Therefore, electromigration in which atoms move due to being swept away by electrons is likely to occur.

When electromigration occurs, the resistance of the wiring increases, and further disconnection occurs. However, the conventional Al wiring layer deposition method is not sufficiently effective in suppressing electromigration when the wiring layer becomes thin.

An object of the present invention is to provide a method for producing an Al wiring layer in which electromigration is less likely to occur even when the film thickness is reduced.

[0006]

A method of manufacturing a semiconductor device according to the present invention comprises a step of placing a target substrate on which wiring is to be formed on a substrate holding means in a vacuum container, and first, the substrate is positively heated. However, an Al deposition step of depositing an Al layer on the surface of the target substrate and heating the substrate halfway to deposit the Al layer is also included.

[0007]

When the Al layer is deposited, the substrate is not heated at first, so that the Al layer having a high (111) orientation can be formed. The Al layer having a strong (111) orientation has high resistance to electromigration. However, the grain size of the Al layer deposited without heating the substrate is small. It is also known that electromigration easily occurs when the grain size is small.

By heating the substrate during the deposition of the Al layer, the (111) orientation of the underlayer can be inherited and the grain size can be increased. Usually, when the substrate is heated to deposit the Al layer, the (111) orientation becomes weak, but by depositing on the underlying Al layer having a high (111) orientation, the (111) orientation is high even if the substrate is heated. You can get sex.

As described above, by heating the Al layer during deposition, the grain size is large and (111)
A highly oriented Al layer can be deposited. Therefore, the occurrence of electromigration can be sufficiently suppressed even if the film thickness is reduced.

Further, by carrying out the deposition without heating the substrate and the deposition with heating the substrate successively in the same vacuum container, it is possible to maintain a high throughput without increasing the number of steps.

[0011]

EXAMPLES It is generally known that electromigration is less likely to occur as the grain size is larger. It is considered that this is because electromigration mainly occurs at the grain boundary. Further, in the case of Al, it is known that the stronger the orientation of the (111) plane of the crystal, the less likely electromigration occurs. According to a paper by Bell Laboratories in 1981, the average grain size of grains is s, the grain size dispersion is σ ² , and the X-ray diffraction intensities of the (111) plane and the (200) plane are I ₍₁₁₁₎ and I, respectively.
₍₂₀₀₎ , the average life of the Al wiring layer MTF (mean t
ime failure) is reported to be proportional to (s / σ ² ) log (I ₍₁₁₁₎ / I ₍₂₀₀₎ ) ³ .

Therefore, it is understood that the grain size may be increased and the orientation of the (111) plane may be increased in order to extend the average life of the Al wiring layer. FIG. 1 shows a schematic view of a sputtering apparatus used in the examples of the present invention. A substrate holder 4 is attached to the side surface inside the vacuum container 1. During film formation, the substrate 3 to be formed on the substrate holding surface of the substrate holder 4
To fix. A cavity is provided inside the substrate holder 4, and Ar gas can flow in the cavity. For example, by flowing heated Ar gas, the substrate holder 4
The substrate 3 held at can be heated.

A target holder 5 is provided so as to face the substrate holder 4. At the time of film formation, the target 2 is fixed to the target holding surface of the target holder 5. Al
When the wiring layer is deposited by sputtering, an Al disc is used as the target 2. At the time of film formation, while introducing a sputtering gas such as Ar from the sputtering gas introduction pipe 6,
The inside of the vacuum container 1 is evacuated from the exhaust pipe 7 to maintain the inside at a predetermined pressure. A discharge is generated in the vacuum container 1 by applying a DC voltage. A negative voltage is applied to the target holder, and ionized Ar ⁺ ions collide with the target and sputter Al.

Next, a method of manufacturing the Al wiring layer according to the embodiment of the present invention will be described. As the substrate 3 for film formation, a substrate having a Ti / TiN layer (barrier metal layer) formed on its surface was used. The Al layer on the TiN layer is usually difficult to have (111) orientation. First, an Al layer having a thickness of 200 nm is deposited on the Ti / TiN layer by sputtering without heating the substrate. Subsequently, Ar gas heated to 350 ° C. is caused to flow into the cavity in the substrate holder 4 to heat the substrate 3 to deposit an Al layer having a thickness of 300 nm.

FIG. 2 shows the change over time in resistance when a current is passed through the Al wiring. FIG. 2A shows a substrate temperature of 350 ° C.
Al with a thickness of 350 nm prepared by conventional sputtering with
In the case of wiring, FIG. 2B shows the case of Al wiring manufactured by the above-mentioned embodiment. The horizontal axis represents the elapsed time from the start of measurement in unit time, and the vertical axis represents the resistance in unit Ω. The width of the Al wiring to be measured is 2 μm and the length is 800 μm.
m, and the current density is 2 × 10 ⁶ A / cm ² .

As shown in FIG. 2A, in the case of the Al wiring manufactured by the conventional method, the resistance value greatly increases with the elapse of time, although it varies depending on the sample. If the resistance increased by 10% or more from the initial resistance value is regarded as defective, about 40% of the samples become defective in 580 hours.

As shown in FIG. 2 (B), in the case of the Al wiring manufactured according to this embodiment, the resistance value hardly increases with the passage of time. No defects occurred at all even after 1200 hours from the start of measurement.

Al produced by the conventional example and the present example
The grain size of the wiring layer surface is 2.76 μm each
And 2.72 μm. In the conventional example, since the substrate is heated from the beginning of film formation, a relatively large grain size is obtained. On the other hand, in the case of this example, the grain size is considered to be small because the substrate was not heated at the beginning of film formation. However, since heating is performed during film formation, the grain size becomes large, and a grain size almost the same as that of the conventional example is obtained.

Further, the (111) crystal orientation of the Al wiring layer produced by the conventional example and the present example was measured by X-ray diffraction. The peak showing the (111) crystal plane is 1510 cps in the case of the conventional example, and 7120 c in the case of this example.
It was ps. From this, it can be seen that the Al wiring layer manufactured according to this example has a very strong (111) orientation as compared with the conventional example.

This is inferred as follows. When the substrate is heated to deposit the Al layer, the grain size becomes large but the (111) orientation becomes weak. On the other hand, when an Al wiring layer is deposited without heating the substrate at the beginning of film formation, an Al layer having a small grain size but excellent (111) orientation is formed. By heating the substrate during film formation, the grain size increases while maintaining high (111) orientation. Therefore, it is considered that an Al wiring layer having excellent (111) orientation and a relatively large grain size can be deposited.

Further, according to the present embodiment, since the film formation performed without heating the substrate and the film formation performed with the substrate being heated can be continuously performed, the number of steps is not increased as compared with the conventional example.
Therefore, it is possible to obtain almost the same throughput as the conventional example.

In the above embodiment, A for heating the substrate is used.
Although the case where the temperature of the r gas is set to 350 ° C. has been described, the temperature may be 300 ° C. or higher in order to obtain the heating effect. Also, since Al melts at 400 ° C. or higher, 4
It is preferably 00 ° C or lower.

The thickness of the Al wiring layer deposited without heating the substrate is preferably 20 to 50%, more preferably 30 to 50% of the total thickness of the Al wiring layer. Although DC sputtering was used as sputtering in the above embodiment, DC magnetron sputtering, RF sputtering and RF sputtering were used.
Similar effects can be obtained by using other sputtering such as magnetron sputtering.

Further, in the above embodiment, the case of depositing the Al wiring layer on the Ti / TiN layer has been described, but the same effect can be expected when depositing on the other barrier metal layer or on the insulating layer. In particular, when the substrate is heated, it is highly effective when it is deposited on the surface where (111) orientation is difficult.

FIG. 3 shows a partial cross section of a DRAM manufactured by using the Al layer manufacturing method according to the embodiment of the present invention. p
A field oxide film 13 is selectively formed on the surface of the type silicon substrate 10 to define an active region. A gate electrode 14 is formed on the surface of the active region via a gate oxide film. N ⁺ type source / drain regions 11 and 12 are formed on both sides of the gate electrode 14.

Bit lines 16 are arranged in the source region 11. The bit line 16 is formed, for example, in a laminated structure in which a tungsten silicide layer is stacked on a polycrystalline silicon layer.

An electrode 17 of the storage capacitor is connected to the drain region 12. The counter electrode 18 is arranged to face the electrode 17 via a thin insulating film. These electrodes 17 and 18 are made of, for example, polycrystalline silicon.

A bit line 1 is formed on the surface of the silicon substrate 10.
6, the gate electrode 14 and the storage capacitor are embedded to form an interlayer insulating film 15. A contact hole is provided in a portion of the interlayer insulating film 15 corresponding to the bit line 16, and a first-layer Al wiring is formed so as to be connected to the bit line 16.

The Al wiring of the first layer is formed by stacking a Ti / TiN barrier metal layer 19 and an Al layer 20. The thicknesses of the Ti layer and the TiN layer are, for example, 20 nm and 1 respectively.
00 nm. The Al layer 20 is manufactured by the method according to the above-described embodiment. Interlayer insulating films 21 and 22 are formed by burying the first-layer Al wiring 20. The Al wiring 20 of the first layer is connected to the Al wiring 2 of the second layer through the contact holes provided in the interlayer insulating films 21 and 22.
Connected to 3.

The Al wiring 20 of the first layer is the A wiring of the second layer.
The current density in the Al wiring 20 is high because it is much thinner than the 1 wiring 23. By producing this Al wiring 20 by the method according to the above-mentioned embodiment, the occurrence of electromigration can be suppressed.

Since the underlying layer of the second Al layer 23 is the interlayer insulating film or the first Al wiring layer, it is not necessary to provide a TiN layer as a barrier metal layer. Second layer A
It is preferable to form a Ti layer having a thickness of, for example, about 30 nm as a lower layer of the 1 wiring layer. On the Ti layer, an Al layer having a strong (111) orientation can be formed even if the substrate is heated from the beginning to deposit Al.

In the above embodiments, the case where Al is used as the wiring layer has been described, but it is also possible to use a material containing Al as a main component and a slight amount of other metal or semiconductor material mixed therein. For example, add 1% Si to Al, add 1% Si to Al
Add 0.5% Cu, add 1% Ti to Al, add S to Al
You may use the wiring layer etc. which added 1% of i to 0.5% of Ti.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0034]

As described above, according to the present invention,
Even if the thickness of the Al wiring layer is reduced, electromigration can be effectively suppressed.

[Brief description of drawings]

FIG. 1 is a schematic view of a sputtering apparatus used in an example of the present invention.

FIG. 2 is a graph showing changes in resistance of an Al wiring layer manufactured by a method according to a conventional example and a method according to an example of the present invention with time.

FIG. 3 is a cross-sectional view of a DRAM manufactured by an Al wiring layer manufacturing method according to an example of the present invention.

[Explanation of symbols]

 1 Vacuum Container 2 Target 3 Substrate 4 Substrate Holder 5 Target Holder 6 Sputtering Gas Introducing Pipe 7 Evacuation Pipe 10 Silicon Substrate 11 Source Region 12 Drain Region 13 Field Oxide Film 14 Gate Electrode 15, 21, 22 Interlayer Insulating Film 16 Bit Line 17 Storage capacitor electrode 18 Counter electrode 19 Ti / TiN barrier metal layer 20 First layer Al wiring 23 Second layer Al wiring

Claims (7)

[Claims] 1. A step of placing a target substrate on which a wiring layer containing Al as a main component is to be formed on a substrate holding means in a vacuum container, and first, on the surface of the target substrate without actively heating the substrate. An Al deposition step of depositing a wiring layer containing Al as a main component and heating the substrate midway to deposit the wiring layer containing Al as a main component. 2. The substrate holding means has a cavity through which a gas flows, and in the Al depositing step, after the wiring layer containing Al having a predetermined thickness as a main component is deposited, the substrate holding means The method of manufacturing a semiconductor device according to claim 1, further comprising the step of flowing a heated gas into the cavity. 3. The temperature of the heated gas is 300 to 4
The method for manufacturing a semiconductor device according to claim 2, wherein the temperature is 00 ° C. 4. The method for manufacturing a semiconductor device according to claim 2, wherein the heated gas is Ar gas. 5. A Ti / TiN layer is formed on the surface of the target substrate.
The method for manufacturing a semiconductor device according to claim 1, wherein a layer is formed. 6. The wiring layer containing Al as a main component is deposited by sputtering in the Al deposition step.
A method for manufacturing a semiconductor device according to any one of 1. 7. In the Al deposition step, the thickness of the deposited wiring layer containing Al as a main component is 20 to 50% of the total thickness of the target wiring layer containing Al as a main component. 7. The method for manufacturing a semiconductor device according to claim 1, wherein the heating of the substrate is started when the temperature becomes low.