JPH03166731A - Wiring method of copper or copper alloy and structure thereof - Google Patents

Abstract

PURPOSE:To improve the oxidation resistance of copper, and to form a copper wiring having high reliability by inactivating chemically active copper, extremely increasing crystal grain size as large as or larger than the wiring width of the copper wiring. CONSTITUTION:A copper film 1 is applied onto a substrate 3, crystal grain size is increased extremely, and the crystal grain size is made larger than the wiring width of a copper wiring. Consequently, crystal grain size is grown and a diffusion rate into the copper film 1 of oxygen is decreased in the active copper film 1, thus improving oxidation resistance. Since the copper film 1 is inactivated, a copper surface is not oxidized under the temperature at the time of applying, even if other metal or alloy is applied for the purpose of enhancing oxidation resistance subsequently. Likewise, stable copper nitride and copper fluoride can be formed because no copper oxide is formed on the copper surface even when nitriding treatment and fluorination treatment are executed. Accordingly, the reliability of the wiring can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for surface treatment of copper alloy wiring. Copper originally has low oxidation resistance, and its surface is oxidized even in a trace amount of oxygen, reducing the reliability of copper wiring. Therefore, in order to solve this problem, a surface treatment method for copper wiring is required.

[Conventional technology]

Conventionally (Japanese Unexamined Patent Publication No. 62-290150), a structure in which Cn is covered with another metal or alloy has been proposed in order to improve the oxidation resistance of Cn. However, the process is complicated, and there are concerns about reactions between the copper and the metal covering it due to the subsequent thermal history. This has led to problems such as an increase in wiring resistance and progress of oxidation and corrosion, leading to a decrease in the reliability of the wiring.

[Problem to be solved by the invention]

The problem that the present invention aims to solve is that in order to improve the oxidation resistance of steel, methods of covering it with other metals or alloys or simply nitriding copper oxidize the copper due to the subsequent thermal history. There were concerns. Copper films are usually deposited by sputtering or vapor deposition, but the crystal grain size after deposition is usually 0.
．． The diameter is 1 to 0.2 μm, and oxidation proceeds at about 100° C. even in the presence of trace amounts of oxygen. Therefore, the copper surface is oxidized even at the treatment temperature of the selective CVD method, nitriding method, or fluoriding method in which the #i surface is covered with another metal. As a result, even if the copper surface is covered with a metal or alloy or treated with nitride fluoride, copper oxide is formed by reacting with residual oxygen, and an oxidation-resistant film is deposited on top of the copper oxide. Ta. In this case, there was a problem in that copper oxide on the copper surface progressed into the film due to the subsequent thermal history, leading to a decrease in the reliability of the wiring. In addition, the copper film has poor adhesion with the SiOz film, and as shown above, there was a problem that the copper film would peel off during selective CVD nitriding, fluoridation, and etching for pattern formation. .

[Means to solve the problem]

The present invention to solve the above-mentioned problems is achieved by depositing a copper film on a substrate, enlarging the crystal grain size, and then performing an annealing treatment to improve adhesion. Regarding the annealing conditions, it is preferable to perform the annealing in a vacuum to avoid the inclusion of oxygen in the atmosphere, or to perform the annealing using an inert gas, nitrogen, or hydrogen. In this case, several percent of hydrogen may be added to the inert gas, nitrogen, for the purpose of reducing trace amounts of oxygen.

Alternatively, the copper film may be deposited while increasing the substrate temperature and elongating the crystal to a certain extent.

[Effect]

By applying the above measures, the crystal grain size of the active copper film grows, and the diffusion rate of oxygen into the copper film decreases, thereby improving oxidation resistance. Furthermore, since the copper film is inactivated, even if other metals or alloys are subsequently deposited for the purpose of improving oxidation resistance, the copper surface will not be oxidized due to the temperature during deposition. Similarly, even when nitriding or fluoridating,
Since no copper oxide is formed on the copper surface, stable copper nitride and copper fluoride can be used.

On the other hand, a degassing reaction occurs at the interface between copper and SiC), and copper and S
The adhesion of iOz is improved.

〔Example〕

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

In FIG. 1(a), for example, 50% of copper is deposited on a Si substrate on which a thermal oxide film 2 is formed, for example, by a DC magnetron sputtering method.
It is coated with 00A. In the as-adhered state, the crystal grain size of copper is as fine as about 0.2 μm. For example, as shown in (b), 40
Anneal at a temperature of about 0℃. As a result, the copper crystal grain size increases to about 1 μm. Next, as shown in (c), copper is etched using the resist 4 as a mask. As is well known, copper is difficult to etch and requires etching at high temperatures. At this time, the grains of the steel have already become huge, so if the wiring IIA width is, for example, 0.5 μm, the grain size is larger than the wiring width, so oxygen diffusion from the grain boundaries is suppressed. There is no problem even if the resist is subsequently removed in oxygen plasma. Next, as shown in (d), even when an interlayer insulating film 5 is deposited, it can withstand high temperatures to a certain extent. FIG. 2 is a schematic diagram when copper wiring is formed by a normal method that does not use the present invention. As shown in (a), the case where copper is deposited and then etched without making the grains large is shown. When etching is performed using the resist 4 as a mask, the resist is oxidized by diffusion of oxygen from grain boundaries during heating before coating. Since the subsequent dry etching step is also carried out in a high temperature atmosphere as described above, after etching, the entire surface is covered with copper oxide 6 as shown in (b), and oxygen is further diffused into the film. The resist 4 is removed and an interlayer insulating film 5 is deposited as shown in (c). Even in this case, oxidation of copper 1 proceeds at a certain high temperature, and the substantial cross-sectional area of copper 1 decreases, leading to an increase in resistance.

FIGS. 3 and 4 show the case where the copper surface is covered with another metal by selective CVD as a method for improving oxidation resistance. FIG. 3 shows the case where copper is deposited and then etched without enlarging the crystal grain size, and then covered with another metal.

As shown in (a), the entire surface of the active copper 1 is covered with copper oxide 6 after etching. Thereafter, as shown in (b), another metal 7 such as Mo, W, etc. is deposited by, for example, selective CVD. In this case, it is necessary to raise the temperature to a certain degree, e.g.
This results in a wiring structure with low oxidation resistance. On the other hand, FIG. 4 shows a similar wiring structure formed using the present invention. As shown in Figure 1, before patterning, in an inert gas, vacuum, nitrogen, or several percent hydrogen.
Materials that are annealed in a forming gas that contains them, or that increase the substrate temperature during deposition to increase the crystal grain size, have excellent oxidation resistance, and as shown in Figure 4 (a), the surface is not oxidized. It is only pure copper 1. Even if metal 7 is then deposited by selective CVD, it is not oxidized during deposition, and copper 1
The entire surface is covered with metal 7, which not only has oxidation resistance but also
The wiring structure also has excellent migration resistance.

FIGS. 5 and 6 show another method for improving oxidation resistance in which the copper surface is nitrided or fluorinated. Fifth
The figure shows that after copper is deposited, it is etched without increasing the crystal grain size, and then nitrided in a nitrogen or ammonia atmosphere. N
The case of fluorination treatment in a fluoride atmosphere such as Fa or SFs is shown.

As the copperwork is covered with copper oxide 6 as shown in (b), copper nitride or copper fluoride is not formed even if it is nitrided or fluoridated, and oxidation progresses due to the influence of residual oxygen during the treatment. ．． Therefore, oxidation resistance does not improve even if the nitriding or fluoriding treatment is performed.

On the other hand, FIG. 6 shows the case of nitriding or fluoriding using the present invention. FIG. 6(a) is a diagram produced in the same manner as FIG. 4(a). Thereafter, nitriding or fluoriding treatment is performed as shown in (b). At this time, since the copper surface is not oxidized, the copper 1 reacts with nitrogen or fluorine, and the entire surface is covered with copper nitride or copper fluoride 8, improving oxidation resistance.

Figure 7 shows that as described in Figures 5 and 6, as a method of enlarging grains before nitriding, annealing was performed at 450°C for a processing time in a nitrogen-based forming gas containing several percent hydrogen. One is in an as-devo state, that is, without annealing, and then nitrided and then oxidized. The horizontal axis of the graph is the oxidation time, and the back axis is the copper oxide film thickness. Obviously, the rate of oxidation of copper is slower when the copper crystal grain size is enlarged by annealing than when the copper crystal grain size is finer than when the copper is not annealed. The film thickness is about 300 pieces. In this way, even when the same nitriding treatment is applied, the oxidation resistance is improved when the grains are made larger. Furthermore,
Since there is no substantial reduction in the cross-sectional area of copper, a wiring with excellent migration resistance can be formed without increasing current density.

Figure 8 is at the time of as-devotion. The orientation of a copper film annealed at 400°C and 500°C was investigated by X-ray diffraction. 5
If the (1 1 1) strength at 00°C annealing is 1, it is approximately 0.65 at as-deposited, and approximately 0.85 at 400°C annealing, and the increased orientation also improves oxidation resistance. Improving.

The crystal grain size on the surface during as-debossing and annealing at 500°C is
According to EM observation, the crystal grain size during as-deposited is 0.1 to 0.
．． 2 μm, whereas when annealing at 500°C, it is l~2 μm.
As a result, the intrusion of oxygen from the grain boundaries is suppressed.

〔Effect of the invention〕

As explained above, according to the present invention, by inactivating chemically active copper and increasing the crystal grain size, the oxidation resistance of copper is improved and highly reliable copper wiring can be formed. can.

[Brief explanation of the drawing]

Fig. 1 shows the formation of an interlayer insulating film after forming copper wiring using the present invention, Fig. 2 shows the conventional method, Fig. 3,
Figure 4 shows a structure in which the entire surface of the copper wiring is coated with metal, Figure 3 shows the conventional method, Figure 4 shows the method of the present invention, and Figures 5 and 6 show the structure of the copper wiring. This is a structure in which the entire surface is nitrided or fluorinated. Figure 5 shows the conventional method, Figure 6 shows the method of the present invention, and Figure 7 shows the oxidation of nitrided copper using the present invention. FIG. 8 is a diagram comparing the increase in copper film thickness between crystal grain sizes of 0.2 μm and 1 μm, and a diagram showing changes in orientation due to annealing treatment. DESCRIPTION OF SYMBOLS 1... Copper, 2... Thermal oxide film, 3... Silicon substrate, 4... Resist, 5... Interlayer insulating film, 6... Copper oxide, 7... Gold Figure 1 Figure 2 Figure 3 Figure Level 4 Figure 5-1 ÷ 5 Figure 6 Figure 7 Figure 7 Presentation by Jinri Shun /) m indoctrination / 1st life comparison Annie) v1: Yoru @'s haiku It student

Claims (1)

[Scope of Claims] 1. A wiring structure of copper or copper alloy containing at least copper, characterized in that the crystal grain size is larger than the wiring width of the copper wiring. 2. In claim 1, the structure of the copper wiring is as follows:
A copper wiring structure characterized in that a crystal grain boundary formed by two crystals is larger than the wiring width and wiring thickness of the copper wiring. 3. A method for forming a wiring containing at least copper, including a step of enlarging the crystal grain size of copper or copper alloy, a patterning step after the step, and an oxidation-resistant treatment after the step,
A wiring method for copper or copper alloy, comprising a step of forming an interlayer insulating film after the step. 4. In claim 2, the step of enlarging the crystal grain size of the copper or copper alloy involves annealing after depositing the copper or copper alloy or raising the substrate temperature to a high temperature during deposition. Features copper or copper alloy wiring method. 5. In claim 3, the annealing atmosphere is an inert gas that does not oxidize the copper or copper alloy, nitrogen, a mixed gas containing these and hydrogen, hydrogen gas, or vacuum. Copper alloy wiring method.