JPH04133321A - Chemical vapor growth method of metal thin film - Google Patents

Abstract

PURPOSE:To prevent an aluminum nucleus from being produced on an insulating thin film by a method wherein aluminum is grown selectively in a state that one part of a substrate has been protected by using an amorphous semiconductor thin film. CONSTITUTION:An amorphous silicon thin film 8 is set inside a CVD apparatus; the apparatus is evacuated to produce a vacuum; after that, the surface is etched by using an RF plasma or an ECR method; then, aluminum is rapidly grown selectively inside a CVD reaction furnace. Since, in succession to the etching operation, the aluminum is rapidly grown selectively, aluminum 6 is filled into a via hole. Since an interlayer insulating film 4 is covered with the amorphous silicon thin film 8 at this time, it is possible to restrain an aluminum nucleus from being produced. Then, the amorphous silicon thin film is removed by using a mixed-gas plasma of CF4 and oxygen. Any well-known method for removing the film can be applied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of depositing a metal thin film for use in electrodes or wiring of a semiconductor device, particularly to a chemical vapor deposition method.

[Prior art] Selective growth of aluminum using chemical vapor deposition is:
A thin aluminum film is not deposited on an insulating material, but only on a metal or semiconductor material. This selective growth of aluminum utilizes only differences in substrate materials to achieve selectivity in thin film deposition, so the surface of the substrate where aluminum is deposited is either an ideal metal or semiconductor material or exposed. , and the surface area where aluminum is not deposited must be a homogeneous insulating thin film without contamination or damage. However, in actual LSI manufacturing processes, these surfaces are usually not in an ideal state.

In most cases, the surfaces of metals and semiconductors are covered with a natural oxide layer or a surface contamination layer, and the surface of an insulating thin film is subject to changes in film quality due to differences in composition or deposition method, or damage caused during the process. exist.

For these reasons, an aluminum film with severe irregularities often grows, or aluminum nuclei are likely to be generated on an insulating thin film.

FIG. 3 is a diagram showing only the embedding process when performing pier hole embedding using conventional aluminum selective growth technology in the manufacturing process of semiconductor devices, in which 1 is a silicon substrate, 2 is an insulating In the film pattern, 3 is a first layer wiring pattern, 4 is an interlayer insulating film, and 5 is a peer hole opened in the first layer insulating film. FIG. 3(a) shows a cross-sectional structure of a pier hole portion in which a pier hole 5 is opened in an interlayer insulating film 4. As shown in FIG. Either send this sample to a CVD device and perform selective growth of aluminum to fill the pier hole, or at that time, a natural oxide layer is formed on the surface of the first layer of aluminum wiring exposed in the pier hole. , pretreatment is required to remove this. This pretreatment method includes lightly etching the aluminum surface using a dilute hydrofluoric acid solution, and CVD
After entering the device and drawing a vacuum, RF plasma or E
There is a method in which the surface is etched using CR etching, and then aluminum is rapidly selectively grown in a CVD reactor. In the former method, the surface is left exposed to the atmosphere after being etched, and the aluminum surface is oxidized again, which is not effective. By starting the deposition, the formation of a native oxide film is prevented and a high quality aluminum film can be deposited. However, the surface of the sewn membrane damaged by RP etching is shown in Fig. 3(b).
As shown in FIG. 2, aluminum nuclei 7 are generated, and there is a problem that so-called selectivity is deteriorated. This problem of selectivity deterioration is not limited to RF etching as a pretreatment for aluminum deposition; for example, when the insulating thin film is a silicon nitride film deposited using plasma CVD,
Nucleation was more likely to occur in silicon oxide films deposited using thermal oxidation than in silicon oxide films deposited using thermal oxidation, due to the properties of the material itself, deviations from stoichiometry, and damage caused by plasma.

[Problem to be Solved by the Invention] If the selectivity deteriorates and aluminum nuclei are generated on the insulating film, unevenness will occur in the aluminum film deposited over the entire surface in subsequent steps, and the fineness of the wiring pattern will be reduced. Processing becomes difficult, and various problems arise, such as increased electrical resistivity due to deterioration of film quality and deterioration of micro-rayon resistance.

An object of the present invention is to provide a method for selectively growing a smooth, high-quality aluminum thin film on a metal material while preventing nucleation on the insulating thin film and stably ensuring selectivity. In particular, one of the main objects of the present invention is to prevent the generation of aluminum nuclei on the insulating film when the substrate is cleaned by RF etching or the like before selective growth.

[Means for Solving the Problems] In the present invention, in order to prevent aluminum nucleation on an insulating thin film, an amorphous semiconductor thin film that can suppress the degree of nucleation even lower than an insulating thin film is used to form a substrate. In this method, selective growth of aluminum is performed with a portion of the aluminum layer protected. Methods for protecting a partial substrate surface with an amorphous semiconductor thin film include (1) simply forming an amorphous semiconductor thin film pattern on the substrate; (2) forming an amorphous semiconductor thin film on the entire surface or in part; After that, a method of crystallizing all or part of the amorphous semiconductor thin film using laser annealing, solid phase epitaxial growth, etc.; (3) forming a crystalline semiconductor thin film pattern (either single crystal or polycrystalline) on the substrate; After formation, there is a method of making the surface of this semiconductor thin film pattern amorphous by ion irradiation or the like.

[Operation] In the selective growth of aluminum, aluminum deposition progresses on the conductive substrate and does not progress on the insulating substrate. In the case of a semiconductor substrate, which is between the two, it may be considered possible to deposit aluminum, or there may be exceptional cases. In single-crystal silicon wafers, which are normally used as substrates for silicon semiconductor devices, and polycrystalline silicon, which is used as electrode material, aluminum can be deposited under selective growth conditions under commonly used conditions, regardless of the type of dopant or its concentration. It is possible. However, on an amorphous silicon material substrate deposited at a relatively low temperature using a method such as evaporation, sputtering, or thermal CVD, aluminum does not deposit under normal selective growth conditions.

Similarly, even with single crystal or polycrystalline Noricon materials, RF
If the substrate becomes amorphous due to ion irradiation such as etching, aluminum will no longer be deposited on these substrates. In contrast to the high density of aluminum nuclei generated during aluminum selective growth when an insulating thin film is irradiated with ions, it has been experimentally confirmed that nucleation is extremely low in amorphous semiconductors. From the above, it is possible to suppress aluminum nucleation on an amorphous semiconductor substrate, and to significantly improve selectivity in aluminum selective growth by protecting an insulating thin film with an amorphous semiconductor material. becomes.

[Example] (Example 1) Fig. 1 (2) is a diagram illustrating a first example of the present invention, taking as an example the embedding of peer holes in multilayer wiring.

Figure 1(a) shows an insulating film pattern 2 on a silicon substrate l.
, a first layer wiring pattern 3 is formed, and after an interlayer insulating film 4 and an amorphous silicon thin film 8 are sequentially deposited thereon, a peer hole 5 is opened using lithography and etching techniques.

The amorphous silicon thin film 8 is an important component in the present invention, and thereby prevents the generation of aluminum nuclei on the interlayer insulating film 4.

Various types of amorphous silicon thin films have been known depending on their composition and deposition method, and any of these can be used for the purpose of the present invention. For example, as for the dopant, non-doped, phosphorus-doped, or poron-doped can be used, and an amorphous silicon film containing oxygen, carbon, hydrogen, etc. can also be used.

Regarding deposition methods, in addition to sputtering and vapor deposition, thermal CVD
D, plasma CVD, etc. may be used. The thickness of the film can be freely selected depending on the purpose, as long as it is thick enough to provide a mask effect without pinholes, so here it was set at 500 people.

This sample is set in a CVD device and selective growth of aluminum is performed to fill the pier hole. At that time, a natural oxide film layer is formed on the surface of the first layer of aluminum wiring exposed inside the pier hole. Therefore, pretreatment is necessary to remove this. This pretreatment method includes lightly etching the aluminum surface using a dilute hydrofluoric acid solution, or placing the sample in a CVD device and drawing a vacuum, followed by l? There is a method of etching the surface using F plasma or ECR, and then selectively growing aluminum immediately in a CVD reactor. In the former method, the surface is left exposed to the atmosphere after being etched, and the aluminum surface is oxidized again, which is not effective. By starting the process, formation of a natural oxide film is prevented and a high quality aluminum film can be deposited.

Here, the RF etching conditions were RIE mode, argon gas pressure of 5 mTorr, RF power of 150 W, and etching time of 5 minutes.The oxide layer on the aluminum surface was removed and the amorphous amorphous silicon layer was completely etched. Other etching conditions may be used as long as there is no problem. It is known that when performing RF etching, the crystalline silicon surface becomes amorphous due to ion bombardment, so when performing RF etching as in this example, the amorphous silicon thin film 8 is It is possible to replace it with a crystalline silicon thin film such as crystalline silicon or single crystal silicon.

Immediately following the RF etching, aluminum is selectively grown to fill the inside of the peer hole with aluminum 6, as shown in FIG. 1(b). At this time, since the interlayer insulating film is covered with an amorphous silicon thin film, generation of aluminum nuclei, which has been a problem in the past, can be suppressed. The aluminum deposition conditions are as described in JP-A-63-033569. Japanese Patent Publication No. 63-047364
．． Alternatively, the method may be similar to the method disclosed in Japanese Patent Application Laid-Open No. 63-282274.

FIG. 1C shows a state in which the amorphous silicon thin film is removed using a mixed gas plasma of CF4 and oxygen. Any of the generally known methods can be used for this removal, but care must be taken to ensure that the selectively grown aluminum film is not etched to the extent that it becomes a substantial problem. Further, depending on the case, it is possible to omit this step and leave the amorphous silicon thin film as it is.

The subsequent steps are omitted in FIG. 1, or, for example, aluminum is deposited on the entire surface using a normal sputtering method, and aluminum wiring is formed using lithography and etching techniques. Note that since a natural oxide film layer is usually formed on the surface of the selectively grown aluminum 6, which causes an increase in contact resistance, 1n-situ RF etching is performed before this aluminum deposition. is desirable.

Figure 1 shows the case where the present invention is used to fill a peer hole between the first and second layer wiring, and the same figure can also be used when configuring multilayer wiring with a large number of wiring layers. Needless to say, this can be achieved by repeating the process. Furthermore, the process shown in FIG. 1 can be applied not only to burying peer holes but also to burying contact holes. In that case, since the contact hole is open in the silicon substrate 1, when RF etching is performed, the surface of the silicon substrate inside the contact hole becomes amorphous, making it impossible to deposit aluminum. Therefore l? It is preferable to use wet etching using dilute hydrofluoric acid or the like without using F etching. If silicon is not exposed in the contact hole and the contact hole is made of a conductive material other than silicon, such as titanium nitride, tungsten, or silicide, there is no problem in performing RF etching.

In the wiring formed as described above, fine peer holes are well filled and no aluminum nuclei are generated on the interlayer insulating film, so high migration resistance can be ensured, and fine and high-density wiring can be achieved. It is possible to realize LSI.

(Embodiment 2) FIG. 2 is a diagram illustrating a second embodiment of the present invention using contact hole filling as an example.

FIG. 2(a) shows a state in which an insulating film pattern 2 having an opening called a contact hole 9 is formed on a silicon substrate l. After cleaning this substrate with a dilute hydrofluoric acid solution or the like to remove the natural oxide film on the silicon surface in the contact hole 9, it is placed in a CVD device and an amorphous silicon thin film 8 is deposited as shown in No. 21m(b). do. Since this amorphous silicon thin film 8 is partially grown by solid-phase epitaxial growth in subsequent steps, it needs to be a high-quality film with little contamination with oxygen or carbon.
It is preferable to use a deposition method such as eE. Furthermore, if the thickness of the amorphous silicon thin film 8 is as small as several hundred nanometers, it may not be necessary to use a special dopant, or a thin film containing a high concentration of dopants such as phosphorus, arsenic, or boronic acid may be used. It is advantageous in terms of contact characteristics. Then, by performing a heat treatment, the amorphous silicone in the contact hole portion is caused to grow in a solid phase, and is converted into a solid phase growth silicone 10, as shown in FIG. 2(c'). The distance of solid phase epitaxial growth from the silicon substrate can be freely set by changing the heat treatment temperature and heat treatment time. For example, in addition to making the length approximately equal to the thickness of the insulating film pattern in the contact hole portion as shown in Figure 2, it is also possible to make the length approximately the same as the thickness of the amorphous silicon film. However, it is possible to limit it only to the lower part of the contact hole, or conversely, to make it protrude from the contact hole and not to extend it to the upper surface of the insulating film. Figure 2 (C
In the case of the structure shown in ), aluminum also grows from the sides of the contact hole in the subsequent selective growth of aluminum, which has the advantage of shortening the deposition time. - Numerical heat treatment conditions range from 550℃ to 60℃
The conditions are selected from several minutes to several hours at a temperature of about 0°C. Furthermore, it may be difficult to get used to any plane orientation of the silicon substrate l, or it may be necessary to pay attention to the fact that the directionality of in-phase epitaxial growth changes depending on the plane orientation. In this way, by selectively growing aluminum with only the contact hole region of the amorphous silicon thin film transformed into crystalline silicon, a structure in which the contact hole is filled with aluminum as shown in Figure 2 (d) can be realized. be done. The conditions for selective growth of aluminum are similar to those described in Example 1. If the amorphous silicon thin film on the insulating film pattern 2 on which aluminum is not deposited is thin, it may be left as is, or it is usually removed using RF etching or the like to form the structure shown in FIG. 2(e). do. Note that the removal of the amorphous silicon thin film can also be carried out subsequent to the step shown in FIG. 2(C). In this case, it is necessary to devise a method of selectively etching only the amorphous silicon by using an etching solution containing OH, for example, to prevent etching of the solid-phase epitaxially grown silicon. In this way, it is possible to perform high-temperature heat treatment before selectively growing aluminum, and it becomes possible to sufficiently activate the dopant in the solid phase silicon to be grown. Finally, as shown in FIG. 2(f'), a thin aluminum film is deposited on the entire surface and a first layer wiring pattern 3 is formed using lithography and etching techniques. Before depositing the aluminum film, it is necessary to remove the natural oxide film on the surface of the selectively grown aluminum 6 using RF etching to prevent an increase in contact resistance. Aluminum can be deposited by sputtering, vapor deposition, or CVD. Further, the aluminum film may contain impurities such as silicon or copper, or may have a multilayer structure with other metals or alloys such as titanium, titanium nitride, or silicide. do not have.

By using the process described above, it is possible to reduce the aluminum nuclei that often occur on the insulating film pattern during selective growth of aluminum, and it becomes possible to stably realize the filling and flattening of minute contact holes. . In addition, the processing time for selective growth can be shortened, and selective growth can be done on aluminum or silicon substrates.
Since it does not come into direct contact with the substrate, it has the advantage of reducing the deterioration of characteristics of bonding and active elements. As a method to reliably prevent characteristic deterioration due to diffusion, reaction, etc. between the selectively grown aluminum 6 and the silicon substrate 1, a material that is epitaxially grown in the contact hole in the state shown in FIG. 2(a) before depositing amorphous silicon is used. For example, a method of epitaxially growing a metal silicide such as cobalt silicide is effective. Cobalt silicide can be left only in the contact pole by performing heat treatment after depositing cobalt to silicide only the portion that is in contact with the silicon substrate 1, and then removing unreacted cobalt. After doing this, by depositing an amorphous silicon thin film 8 and subjecting it to heat treatment, only the amorphous silicon in the contact hole portion can be converted to crystalline silicon.

In this embodiment, the case where the amorphous semiconductor thin film 8 is converted has been described, but the same effect can be achieved by removing it.

(Example 3) Example 3 shows an example in which the heat treatment in Example 2 of the present invention is changed to irradiation with a laser beam or the like and applied to wiring pattern formation. First, amorphous silicon is deposited on the top surface or the entire surface of a substrate consisting of an insulating film pattern with openings such as contact holes and peer holes. By irradiating this amorphous silicon thin film with a laser beam or the like and drawing a wiring pattern including the contact holes and the tops of the peer holes, this portion is converted into crystalline silicon. If aluminum is selectively grown in this state, aluminum will grow only on the crystalline silicon pattern. Next, aluminum wiring is formed by removing the amorphous silicon in the portions where aluminum is not deposited by RF etching or the like.

It is known that the crystallinity of aluminum selectively grown on single-crystal silicon varies depending on the plane orientation of the substrate silicon, or in any case, the crystal grain size is large and the aluminum becomes close to single-crystal. Therefore, by crystallizing amorphous silicon to form a crystalline thin film with a large grain size, it becomes possible to form an aluminum thin film pattern close to a single crystal thereon. Since the aluminum wiring pattern formed as described above has extremely low density of crystal grain boundaries, it has extremely excellent electromigration and stress migration resistance.

In the above embodiments, selective growth of aluminum is performed after partially crystallizing the amorphous silicon, or alternatively, the entire surface of the amorphous silicon may be crystallized and aluminum may be deposited on the entire surface thereof. In this case, the basic purpose of improving migration resistance may not be achieved unless a subsequent processing step is required to form a wiring pattern using lithography and etching techniques.

Furthermore, after performing a process to deposit a crystalline silicon thin film over the entire surface of the substrate, or to crystallize the entire amorphous silicon thin film deposited over the entire surface of the substrate by laser annealing, these A mask pattern with the same shape as the wiring pattern is formed on the thin film using lithography technology, and in this state, the entire surface is irradiated with ions using RF plasma or low-energy ion implantation to eliminate damage that appears when the mask pattern is removed. It is also possible to selectively grow aluminum only on the unsupported crystalline silicon surface, thereby forming a wiring pattern.

[Effects of the Invention] As explained above, by covering the insulating film with an amorphous semiconductor, the generation of aluminum nuclei on the insulating film can be significantly suppressed, and aluminum can be selectively grown with high selectivity. It becomes possible. Particularly, when a pretreatment such as RF etching is performed before selective growth, there is an advantage that high-density aluminum nuclei generated on the insulating film can be reliably reduced. Further, by partially dividing the surface of the silicon thin film into an amorphous region and a crystalline region and selectively growing aluminum thereon, it becomes possible to easily obtain a wiring pattern with excellent characteristics.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention using a peer hole filling process as an example, FIG. 2 is an explanatory diagram of a second embodiment of the present invention using a contact hole filling process as an example, and FIG. The figure is an explanatory diagram of a conventional example of a pier hole filling process using aluminum selective growth. 1...Silicon substrate, 2...
...Insulating film pattern, 3...First layer wiring pattern, 4...Group...Interlayer insulating film, 5...
・・・Pier hole, 6・・・・・・Selective growth aluminum, 7・・・・・・Aluminum core, 8
... Group... Amorphous solicon thin film, 9...
・・・・・・Contact hole, IO・・・・・・・・・
Solid phase Evita kinial growth silicon pier hole (a) 6 selective growth aluminum (b) 6 selective growth aluminum (c) Fig. 1 First embodiment using the present invention in the pier hole filling process Pier hole 7 aluminum core (b) Conventional example of process

Claims (3)

[Claims] (1) In the selective growth of aluminum in which aluminum is selectively deposited only on the metal surface of a substrate whose surface is partially metal, a semiconductor thin film pattern is formed in a region of the substrate surface excluding metal; A method for chemical vapor deposition of a thin metal film, which comprises irradiating a substrate with ions and then depositing aluminum on the metal. (2) In the selective growth of aluminum, in which aluminum is selectively deposited on the metal or crystalline semiconductor surface of a substrate in which a part of the surface is a metal or a crystalline semiconductor and another surface part is an insulator, the substrate After forming an amorphous semiconductor thin film thereon and converting or removing a part of the amorphous semiconductor thin film to a crystalline semiconductor thin film, the converted crystalline semiconductor thin film or the removed substrate surface is A method of chemical vapor deposition of thin metal films, characterized in that aluminum is deposited on a metal or a crystalline semiconductor. (3) In the selective growth of aluminum, in which aluminum is selectively deposited on the metal or crystalline semiconductor surface of a substrate in which a part of the surface is a metal or a crystalline semiconductor and the other surface part is an insulator, the substrate After forming a crystalline semiconductor thin film thereon and converting or removing a part of the crystalline semiconductor thin film to an amorphous semiconductor, the converted crystalline semiconductor thin film or the metal on the surface of the substrate after the removal is performed. or a method of chemical vapor deposition of metal thin films characterized by depositing aluminum on a crystalline semiconductor.